Instructional Model for E Essay Example

Instructional Model for E Essay A Classroom Model for Designing an ESL Course Ayami Gunasinghe University of South Alabama A Classroom Model for Designing an ESL Course The demand for English-as-a-second-language (ESL) courses has increased tremendously in recent years. This may be due to many reasons including the pervasive influences of globalization and the Internet revolution, and the general attitude change towards the English language as a whole.In former colonial nations such as Sri Lanka, English is no longer viewed as a tool of colonial oppression. Instead, English is vastly perceived by non-native speakers as a non-threatening, utilitarian language that would be of tremendous advantage to them. In the present context, English departments in countries such as Sri Lanka have been overwhelmed by the huge demand for ESL courses and Extension courses in English. The pressure to meet this demand has led to ESL courses being hastily churned out in great quantity but at the expense of quality.Many of these course s are often poorly designed, generic language courses that lack structure and purpose. They often include outdated content and strategies, and pay little or no attention to specific curriculum goals and learner needs. For this reason, I believe that ESL courses must be designed using a systematic approach that is focused on achieving particular communicative and language goals that meet the needs of the learner. The ESL Course Design model was created to facilitate this task.This model has been inspired primarily by the Kemp, Morrison and Ross Model (as cited in Gustafson Branch, 1997), which focuses on curriculum planning. It has, however, also been influenced by other classroom-oriented models such as the Gerlach and Ely model (as cited in Gustafson Branch, 1997)) that emphasizes the specification of content and objectives and the Foresee model (Kid Marquardson, 1994) that adopts a content-based approach to ESL instruction. Like the latter model, this model also takes note of p ractical and theoretical considerations involved in course design.However, while the Foresee model emphasizes the need for sound theoretical basis for content design, the ESL Course Design model focuses on the need for designers to consider research findings and established principles of language teaching with regard to every aspect of the language course design process. In addition, the ESL Course Design model is focused on the design process of a curriculum whereas the Foresee model (Kid Marqurdson, 1994) by contrast, is devoted to integrating content, language and learning strategies instruction in the ESL classroom.The ESL Course Design model advocates a systematic approach to language course design. This does not however mean that this model adopts a linear, lock-step approach. This is essentially a non-linear model that has been created to help language teachers in the design of an effective ESL curriculum. An Overview of the ESL Course Design Model The Three Outer Circles: N eeds, Resources Delivery and Research The ESL Course Design model’s three outer circles are linked to the inner circle via two-way arrows, which indicate that the components of this model are mutually supportive rather than separate and isolated.See figure 1. These three outer circles (Needs, Resources and Delivery, and Research) represent practical and theoretical considerations that will guide the designer during the course design process. A thorough needs analysis of learner needs will result in realistic goals being set and purposeful content being developed, in accordance with the learner’s language learning goals and proficiency level. A focus on available resources and feasible delivery systems will also help designers in their quest to design language courses that are situation appropriate.It is my contention that all these processes must be guided by current research findings and established teaching principles to ensure that the most suitable methods are bei ng employed. Figure 1: The ESL Course Design Model The Innermost Circle: Goals At the heart of the inner circle is a circle with goals at its center. This innermost circle is meant to represent the importance of setting clear goals when designing a language course. As such, in many ways this is a goal-based or goal-driven model although it does pay equal importance to learner analysis and content.In addition, just as Gerlach and Ely (as cited in Gustafson Branch, 1997) acknowledge the fact that teachers may think about instruction from differing points-objectives or content, this model too makes provisions for the designer’s preference. In this respect it allows greater design flexibility than the afore mentioned model as it allows the designer the freedom to approach the task from any point. The Inner Circle: Content and Sequencing, Format and Presentation and Assessment The inner circle is divided into three components. They are Content and Sequencing, Format and Presentat ion and Assessment.The Content and Sequencing segment of the design process includes what will be taught and in what order. A focus on content ensures that learners are being presented with the opportunity to further their knowledge and practice of the language. The Format and Presentation segment draws the designer’s attention to how the subject matter will be taught. The Gerlach and Ely and Kemp models (as cited in Gustafson and Brach, 1997) include the above-mentioned segments, as they are vital ingredients in keeping ESL learners motivated and focused.The Assessment segment prompts designers to focus on evaluation instruments and feedback, which are often given step-motherly treatment in language course design but are a prominent feature of classroom models such as the Gerlach and Ely model (as cited in Gustafson and Branch, 1997). The Outermost Circle: Evaluation The outermost circle represents evaluation. This is a much needed aspect of course design which involves insp ecting every aspect of the course to determine its value, if it meets the required standard and /or whether it needs improvement.The Kemp, Morrison and Ross model (as cited in Gustafson and Branch, 1997) and the Gerlach and Ely model (as cited in Gustafson and Brach, 1997) both emphasize the importance of evaluation in course design and see evaluation as being closely linked to learner goals. As such, this model also incorporates this vital aspect of course design. Parts of the ESL Course Design Model All the parts of this model in my estimation merit equal consideration by the designer. An elaboration of each of the design processes of this model follows, beginning with the three outer circles.The Three Outer Circles: Needs, Resources Delivery and Research Needs A thorough analysis of learner needs is imperative for useful course goals to be set. Many language theorists like Nunan and Lamb (as cited in Valdez, 1999) believe that an effective curriculum is one that has been designe d after a needs assessment has been done to set out the learning objectives, which guide the teacher. In many respects needs analysis influences every aspect of course design including content, format and presentation, and assessment.Learner needs analysis will yield vital information regarding the learner’s current proficiency level, learning style, attitude towards the language and course, in what context the knowledge and skills gained from the course will be utilized, and what interests the learner. This information is invaluable in developing a course that meets the needs of the learner, which should be the primary goal of any language course. Many language courses have been unsuccessful in achieving the desired learning objectives because of the designers’ failure to take note of individual learner goals and preferences.A case in point was the recently developed ESL course for Business Management students at a major university. This course though well organized, was rooted in linguistic development and subscribed to the traditional ESL emphasis on grammar-based exercises. The Business Management students who viewed English as a business tool were disappointed that the course failed to provide them with practical skills that would help them as they entered the corporate world. They were able to attach very little use or meaning to the grammar exercises that were used in isolation, in this course.This resulted in poor attendance and dropouts among the disgruntled students. As such, if learner needs had been considered this course would have been focused on the communicative aspects of language learning and developing communicative competence, which would have been more favorably received by the learners in question. Apart from learning purpose, an analysis of learner needs may also yield data on learning styles and preferences, which have an equal impact on the success or failure of a course.For instance adapting Willing’s grouping (as cited in Valdez, 1999) there are those who are concrete learners; those who like using games, pictures, films and practicing English outside the class. Then there are analytical learners; those who like to study grammar, and English books, and read newspapers, and who like to study alone, find their own mistakes and work on problems set by the teacher. Others are communicative learners who learn by watching, listening to native speakers, talking to friends, in English, and watching television in English.These students value the interactive nature of group work and activities such as simulations that provide them with meaningful opportunities to practice the target language. Others are authority–oriented learners who prefer that the teacher explain everything and who learn by reading and studying grammar (Valdez, 1999). Learner differences such as these must be considered during course design in order to keep learners motivated and engaged in the course material and activitie s. Resources and DeliveryThis aspect of the model prompts designers to consider the situation in which the course will be used and the resources that it has to offer. Resources in this model represent many things. It refers to classroom equipment such as video and audio equipment, recording facilities and computers. It also refers to the monetary resources provided by sponsors for the design, development and implementation of the course. In addition, the teacher or instructor too maybe viewed as a resource and his or her skills and knowledge must be a vital consideration during course design.Yet another resource that is a crucial factor in course design is time. The students themselves become a resource in my opinion in the eyes of the instructor as the number of students and their level of competence plays a large part in designing appropriate activities and content. Designers of ESL curricula must pay attention to all these resources during the design process. The delivery system of the course i. e. if it is to be traditional, web-based, computer-based, self-paced, etc is another important consideration for the language course designer, and will depend on the resources available.Computer-based language learning simulations have become popular in certain developed nations as a means of communicative language instruction. In developing countries such as Sri Lanka, designers must seek alternatives to such instruction due to budgetary constraints and the lack of technological skill amongst learners and instructors, especially in the rural areas. Designers need to focus on resources and delivery in order to ensure that the course will be suitable, practical, and realistic.Research I believe that along with the practical considerations of language course design, designers must also focus on the theoretical implications of language use, acquisition and teaching. There is much research on how to encourage learning in general, and language learning in particular, whi ch must be used to guide content development along with format and presentation. There are many principles that have been established from this research.For instance, research done by Nunan (as cited in De Dilva, 2001) indicates that learners have â€Å"hidden agendas† and that effective learning takes place when the curriculum is expanded to accommodate these hidden individual agendas. Such research supports the principle that individual learner differences and styles must be considered during course design. Designers must explore applied linguistic research and principles related to all the components of this model. They must be guided by this research during their curriculum design journey and quest to establish meaningful content and realistic learning goals.The Innermost Circle: Goals Goals Goals take center stage in this model. Nunan and Lamb (as cited in Valdez, 1999) believe that all language programs should take their form of departure from the goals and objectives t hat have been derived from an analysis of learner needs. I have placed goals at the center of this model, as it is my belief that it is essential to establish why a course is being designed and what it hopes to achieve from the very outset. Having a clear statement of goals is vital for determining the content of the course, deciding on the presentation, and guiding assessment.What follows is an example of goals that were set for an ESL extension course at a major university in Sri Lanka. The course was targeted at Law Faculty students and was based both on tradition and task-based methodology. This course aims to: a) Assist students in developing communicative competence in the English Language by providing them with meaningful opportunities to practice their language skills. b) Help students understand and master the grammatical rules of English. c) Acquaint students with basic legal terms. d) Develop confidence in using the target language.Establishing clear goals for a course al so benefits learners. Crookal and Oxford (as cited in Hill, 2002) suggest that many students, especially graduate students, benefit from being told the goals or purpose of an activity or course. The goals of a course influence the overall design of the course in general and content in particular. The Inner Circle: Content and Sequencing, Format Presentation and Assessment Content and Sequencing The content of language courses consists of the language items, strategies and tasks that meet the goals of the course. When the goal of a language lass is to promote communicative competence the content of the course centers on task-based activities. Conversely, if the goal of the course is focused on developing grammar skills, course content will then be characterized by grammatical features. A systematic way of checking the content of a course is via lists such as frequency-based vocabulary lists, lists of functions and topics, and lists of subskills and strategies (Valdez, 1999). Working from lists is an effective way for designers to make sure that what should be covered is covered and not left to chance and what is unnecessary or redundant is omitted.It is also my view that these lists should be chosen and adapted as a result of the needs analysis in order to set the language learning content of the course. Content also needs to be properly sequenced for logical learning according to the Kemp, Morrison and Ross model (as cited in Gustafson Branch, 1997). I believe that the best way to achieve this is by including easier tasks or units at the beginning of the course and then progressively introducing more challenging ones. This helps to build confidence, which is imperative in language learning.The content of a language course should serve to motivate learners by presenting information that is relevant to the learner and is within the purview of his /her experiences and worldview. I believe that what Gredler (1994) states in relation to language skills /communica tion simulations may also be applied to the content of a language course in that it must be a challenge but not a threat to the learner. In addition, content must also be based on available resources, and current research. Format and Presentation Format and Presentation are often neglected aspects of course design, in my experience.The material in a course needs to be presented in a form that will facilitate learning and achieve the goals of the course. The presentation of a course includes the teaching strategies and activities that will be used. It is imperative that the designer focus on these aspects during the design process as it plays a vital role in keeping ESL learners motivated. The learner analysis and available resources along with current research must guide format and presentation in the design process. Especially vital is the consideration of individual learning styles. For nstance, the format and presentation must appeal to both auditory and visual learners. Some res earch reveals that learners are more comfortable with â€Å"traditional† learning activities over more â€Å" communicative† types (De Silva, 2001). Another study by Pope and Saka (as cited in De Silva, 2001) revealed that stronger (according to test scores and teacher grading) pupils preferred more learner oriented or learner-teacher oriented activities whereas weak students preferred teacher controlled classroom activities. Such findings must be considered when designing a course.During my brief stint as an ESL instructor at a major university in Sri Lanka I began to realize the importance of having a set format for a course. The university ESL course was structured in such a way that learners would first be introduced to a topic of current interest. This would be followed by a listening activity, a reading activity and finally a speaking task in that order. Having this kind of set format is beneficial as it makes the course easier to monitor and fosters learner conf idence, as they become familiar with the learning procedure.Learners are often more comfortable with the predictable than they are with the unpredictable. The fear of â€Å"pop† quizzes is testaments to this, although certain surprise elements do need to be incorporated into course design to prevent students from becoming complacent. These â€Å"surprise† elements may include a role-play activity or a simulation in a traditional grammar-based language course. Course design according to this model is not a linear process. As such, it may be necessary to alter the content or sequencing to suit the lesson format and meet the learning goals. Content must also focus on and facilitate assessment.Assessment Assessment plays a key role in determining if a course has achieved its goals. As such, it is a useful and recurring part of the design process. Of the many ways assessment may be carried out, tests take precedence over the other methods. These tests are an important consi deration in course design. Language courses are associated with both proficiency tests and achievement tests. Proficiency or placement tests are usually held prior to the commencement of a course to determine the learner’s level of language knowledge and which level of the course best fits him or her.Based on this knowledge ESL learners at a major university in Sri Lanka are enrolled in three different courses, simply labeled level one, level two and level three. Level three courses cater to the more proficient learners while level one courses are focused on the needs of learners with little or no knowledge of the target language. These students are subjected to achievement tests that monitor their progress and identify knowledge gaps, at the end of each unit. They are also subjected to a comprehensive achievement test at the end of the course.Such tests elicit valuable information on the effectiveness of the course. As such, designers must pay careful attention to the struct ure of such tests and their place in the overall course design. Curriculum design must also make provisions for the inclusion of other non-test-based assessment such as observation, journal entries, simulation debriefing outcomes and student accounts of their learning. Data gathered from such methods of assessment may in some cases prove to be more valuable than tests in determining the strengths and weaknesses of the course design.The Outermost Circle: Evaluation Evaluation Apart from using assessment data, a course maybe evaluated via learner and instructor input gathered through surveys, interviews and focus groups. This information will determine whether the course meets the required standards, is deficient and needs improvement or needs to be discontinued. Although immediate or formative evaluation of a course is vital, the true worth of a language course can be evaluated only after some time has elapsed allowing learners to utilize the knowledge and skills gained from the cour se in the desired setting.The effectiveness of a language course in my view lies in how it has impacted the life of the learner. In this regard summative evaluation is an important part of the design process. The evaluation process maybe regarded as a backstage process that is imperative for the successful completion and realization of center stage processes such as setting realistic and purposeful goals and content. Responsible curriculum design must therefore include ongoing evaluation of the course. Conclusion The ESL Course Design model serves language teachers in course design, which is often seen as an arduous task.It portrays course design as a process and emphasizes the importance of considering learner needs, resources and applied linguistic research as a practical and theoretical basis for course design. According to the model, this knowledge will hold designers in good stead as they proceed to the other vital components of course design. Goals, content, format and present ation and assessment are all vital aspects of this model that must be given equal consideration. Evaluation too, is given prominence and designers are advised to conduct continuous evaluations to ensure that the curriculum design is effective and viable.The ESL Course Design model testifies to the fact that course design is not a linear or static process. It also implies that ESL course design is a constantly evolving process that needs careful consideration and planning. References De Silva, R. (2001). Students’ perceptions of the English teaching / language experience in the classroom. In David Hays (Ed. ), Teaching English: Possibilities and opportunities ( pp. 85-91). Colombo: The British Council. Hill, J. L. (2002). Playing with the three pigs. Simulation Gaming, 33 (3), 353-359. Gredler, M. (1994). Design evaluation games simulation: A process approach.Texas: Gulf Publishing Company. Gustafson, K. , Branch, R. (Ed. ). (1997). Survey of instructional development mode ls (3rd Ed). New York. Eric Clearinghouse. Kidd, R. , Marquardson, B. (1994, March). The Foresee approach. Paper presented at the annual meeting of the teachers of English to speakers of other languages, Baltimore, MD. Valdez, M. (1999). How learners’ needs affect syllabus design. Forum, 37(1), 30-34. Format Assessment Presentation Content Sequencing Goals Needs Research Resources Delivery Evaluation Evaluation Evaluation Evaluation Evaluation Instructional Model for E Essay Example Instructional Model for E Essay A Classroom Model for Designing an ESL Course Ayami Gunasinghe University of South Alabama A Classroom Model for Designing an ESL Course The demand for English-as-a-second-language (ESL) courses has increased tremendously in recent years. This may be due to many reasons including the pervasive influences of globalization and the Internet revolution, and the general attitude change towards the English language as a whole.In former colonial nations such as Sri Lanka, English is no longer viewed as a tool of colonial oppression. Instead, English is vastly perceived by non-native speakers as a non-threatening, utilitarian language that would be of tremendous advantage to them. In the present context, English departments in countries such as Sri Lanka have been overwhelmed by the huge demand for ESL courses and Extension courses in English. The pressure to meet this demand has led to ESL courses being hastily churned out in great quantity but at the expense of quality.Many of these course s are often poorly designed, generic language courses that lack structure and purpose. They often include outdated content and strategies, and pay little or no attention to specific curriculum goals and learner needs. For this reason, I believe that ESL courses must be designed using a systematic approach that is focused on achieving particular communicative and language goals that meet the needs of the learner. The ESL Course Design model was created to facilitate this task.This model has been inspired primarily by the Kemp, Morrison and Ross Model (as cited in Gustafson Branch, 1997), which focuses on curriculum planning. It has, however, also been influenced by other classroom-oriented models such as the Gerlach and Ely model (as cited in Gustafson Branch, 1997)) that emphasizes the specification of content and objectives and the Foresee model (Kid Marquardson, 1994) that adopts a content-based approach to ESL instruction. Like the latter model, this model also takes note of p ractical and theoretical considerations involved in course design.However, while the Foresee model emphasizes the need for sound theoretical basis for content design, the ESL Course Design model focuses on the need for designers to consider research findings and established principles of language teaching with regard to every aspect of the language course design process. In addition, the ESL Course Design model is focused on the design process of a curriculum whereas the Foresee model (Kid Marqurdson, 1994) by contrast, is devoted to integrating content, language and learning strategies instruction in the ESL classroom.The ESL Course Design model advocates a systematic approach to language course design. This does not however mean that this model adopts a linear, lock-step approach. This is essentially a non-linear model that has been created to help language teachers in the design of an effective ESL curriculum. An Overview of the ESL Course Design Model The Three Outer Circles: N eeds, Resources Delivery and Research The ESL Course Design model’s three outer circles are linked to the inner circle via two-way arrows, which indicate that the components of this model are mutually supportive rather than separate and isolated.See figure 1. These three outer circles (Needs, Resources and Delivery, and Research) represent practical and theoretical considerations that will guide the designer during the course design process. A thorough needs analysis of learner needs will result in realistic goals being set and purposeful content being developed, in accordance with the learner’s language learning goals and proficiency level. A focus on available resources and feasible delivery systems will also help designers in their quest to design language courses that are situation appropriate.It is my contention that all these processes must be guided by current research findings and established teaching principles to ensure that the most suitable methods are bei ng employed. Figure 1: The ESL Course Design Model The Innermost Circle: Goals At the heart of the inner circle is a circle with goals at its center. This innermost circle is meant to represent the importance of setting clear goals when designing a language course. As such, in many ways this is a goal-based or goal-driven model although it does pay equal importance to learner analysis and content.In addition, just as Gerlach and Ely (as cited in Gustafson Branch, 1997) acknowledge the fact that teachers may think about instruction from differing points-objectives or content, this model too makes provisions for the designer’s preference. In this respect it allows greater design flexibility than the afore mentioned model as it allows the designer the freedom to approach the task from any point. The Inner Circle: Content and Sequencing, Format and Presentation and Assessment The inner circle is divided into three components. They are Content and Sequencing, Format and Presentat ion and Assessment.The Content and Sequencing segment of the design process includes what will be taught and in what order. A focus on content ensures that learners are being presented with the opportunity to further their knowledge and practice of the language. The Format and Presentation segment draws the designer’s attention to how the subject matter will be taught. The Gerlach and Ely and Kemp models (as cited in Gustafson and Brach, 1997) include the above-mentioned segments, as they are vital ingredients in keeping ESL learners motivated and focused.The Assessment segment prompts designers to focus on evaluation instruments and feedback, which are often given step-motherly treatment in language course design but are a prominent feature of classroom models such as the Gerlach and Ely model (as cited in Gustafson and Branch, 1997). The Outermost Circle: Evaluation The outermost circle represents evaluation. This is a much needed aspect of course design which involves insp ecting every aspect of the course to determine its value, if it meets the required standard and /or whether it needs improvement.The Kemp, Morrison and Ross model (as cited in Gustafson and Branch, 1997) and the Gerlach and Ely model (as cited in Gustafson and Brach, 1997) both emphasize the importance of evaluation in course design and see evaluation as being closely linked to learner goals. As such, this model also incorporates this vital aspect of course design. Parts of the ESL Course Design Model All the parts of this model in my estimation merit equal consideration by the designer. An elaboration of each of the design processes of this model follows, beginning with the three outer circles.The Three Outer Circles: Needs, Resources Delivery and Research Needs A thorough analysis of learner needs is imperative for useful course goals to be set. Many language theorists like Nunan and Lamb (as cited in Valdez, 1999) believe that an effective curriculum is one that has been designe d after a needs assessment has been done to set out the learning objectives, which guide the teacher. In many respects needs analysis influences every aspect of course design including content, format and presentation, and assessment.Learner needs analysis will yield vital information regarding the learner’s current proficiency level, learning style, attitude towards the language and course, in what context the knowledge and skills gained from the course will be utilized, and what interests the learner. This information is invaluable in developing a course that meets the needs of the learner, which should be the primary goal of any language course. Many language courses have been unsuccessful in achieving the desired learning objectives because of the designers’ failure to take note of individual learner goals and preferences.A case in point was the recently developed ESL course for Business Management students at a major university. This course though well organized, was rooted in linguistic development and subscribed to the traditional ESL emphasis on grammar-based exercises. The Business Management students who viewed English as a business tool were disappointed that the course failed to provide them with practical skills that would help them as they entered the corporate world. They were able to attach very little use or meaning to the grammar exercises that were used in isolation, in this course.This resulted in poor attendance and dropouts among the disgruntled students. As such, if learner needs had been considered this course would have been focused on the communicative aspects of language learning and developing communicative competence, which would have been more favorably received by the learners in question. Apart from learning purpose, an analysis of learner needs may also yield data on learning styles and preferences, which have an equal impact on the success or failure of a course.For instance adapting Willing’s grouping (as cited in Valdez, 1999) there are those who are concrete learners; those who like using games, pictures, films and practicing English outside the class. Then there are analytical learners; those who like to study grammar, and English books, and read newspapers, and who like to study alone, find their own mistakes and work on problems set by the teacher. Others are communicative learners who learn by watching, listening to native speakers, talking to friends, in English, and watching television in English.These students value the interactive nature of group work and activities such as simulations that provide them with meaningful opportunities to practice the target language. Others are authority–oriented learners who prefer that the teacher explain everything and who learn by reading and studying grammar (Valdez, 1999). Learner differences such as these must be considered during course design in order to keep learners motivated and engaged in the course material and activitie s. Resources and DeliveryThis aspect of the model prompts designers to consider the situation in which the course will be used and the resources that it has to offer. Resources in this model represent many things. It refers to classroom equipment such as video and audio equipment, recording facilities and computers. It also refers to the monetary resources provided by sponsors for the design, development and implementation of the course. In addition, the teacher or instructor too maybe viewed as a resource and his or her skills and knowledge must be a vital consideration during course design.Yet another resource that is a crucial factor in course design is time. The students themselves become a resource in my opinion in the eyes of the instructor as the number of students and their level of competence plays a large part in designing appropriate activities and content. Designers of ESL curricula must pay attention to all these resources during the design process. The delivery system of the course i. e. if it is to be traditional, web-based, computer-based, self-paced, etc is another important consideration for the language course designer, and will depend on the resources available.Computer-based language learning simulations have become popular in certain developed nations as a means of communicative language instruction. In developing countries such as Sri Lanka, designers must seek alternatives to such instruction due to budgetary constraints and the lack of technological skill amongst learners and instructors, especially in the rural areas. Designers need to focus on resources and delivery in order to ensure that the course will be suitable, practical, and realistic.Research I believe that along with the practical considerations of language course design, designers must also focus on the theoretical implications of language use, acquisition and teaching. There is much research on how to encourage learning in general, and language learning in particular, whi ch must be used to guide content development along with format and presentation. There are many principles that have been established from this research.For instance, research done by Nunan (as cited in De Dilva, 2001) indicates that learners have â€Å"hidden agendas† and that effective learning takes place when the curriculum is expanded to accommodate these hidden individual agendas. Such research supports the principle that individual learner differences and styles must be considered during course design. Designers must explore applied linguistic research and principles related to all the components of this model. They must be guided by this research during their curriculum design journey and quest to establish meaningful content and realistic learning goals.The Innermost Circle: Goals Goals Goals take center stage in this model. Nunan and Lamb (as cited in Valdez, 1999) believe that all language programs should take their form of departure from the goals and objectives t hat have been derived from an analysis of learner needs. I have placed goals at the center of this model, as it is my belief that it is essential to establish why a course is being designed and what it hopes to achieve from the very outset. Having a clear statement of goals is vital for determining the content of the course, deciding on the presentation, and guiding assessment.What follows is an example of goals that were set for an ESL extension course at a major university in Sri Lanka. The course was targeted at Law Faculty students and was based both on tradition and task-based methodology. This course aims to: a) Assist students in developing communicative competence in the English Language by providing them with meaningful opportunities to practice their language skills. b) Help students understand and master the grammatical rules of English. c) Acquaint students with basic legal terms. d) Develop confidence in using the target language.Establishing clear goals for a course al so benefits learners. Crookal and Oxford (as cited in Hill, 2002) suggest that many students, especially graduate students, benefit from being told the goals or purpose of an activity or course. The goals of a course influence the overall design of the course in general and content in particular. The Inner Circle: Content and Sequencing, Format Presentation and Assessment Content and Sequencing The content of language courses consists of the language items, strategies and tasks that meet the goals of the course. When the goal of a language lass is to promote communicative competence the content of the course centers on task-based activities. Conversely, if the goal of the course is focused on developing grammar skills, course content will then be characterized by grammatical features. A systematic way of checking the content of a course is via lists such as frequency-based vocabulary lists, lists of functions and topics, and lists of subskills and strategies (Valdez, 1999). Working from lists is an effective way for designers to make sure that what should be covered is covered and not left to chance and what is unnecessary or redundant is omitted.It is also my view that these lists should be chosen and adapted as a result of the needs analysis in order to set the language learning content of the course. Content also needs to be properly sequenced for logical learning according to the Kemp, Morrison and Ross model (as cited in Gustafson Branch, 1997). I believe that the best way to achieve this is by including easier tasks or units at the beginning of the course and then progressively introducing more challenging ones. This helps to build confidence, which is imperative in language learning.The content of a language course should serve to motivate learners by presenting information that is relevant to the learner and is within the purview of his /her experiences and worldview. I believe that what Gredler (1994) states in relation to language skills /communica tion simulations may also be applied to the content of a language course in that it must be a challenge but not a threat to the learner. In addition, content must also be based on available resources, and current research. Format and Presentation Format and Presentation are often neglected aspects of course design, in my experience.The material in a course needs to be presented in a form that will facilitate learning and achieve the goals of the course. The presentation of a course includes the teaching strategies and activities that will be used. It is imperative that the designer focus on these aspects during the design process as it plays a vital role in keeping ESL learners motivated. The learner analysis and available resources along with current research must guide format and presentation in the design process. Especially vital is the consideration of individual learning styles. For nstance, the format and presentation must appeal to both auditory and visual learners. Some res earch reveals that learners are more comfortable with â€Å"traditional† learning activities over more â€Å" communicative† types (De Silva, 2001). Another study by Pope and Saka (as cited in De Silva, 2001) revealed that stronger (according to test scores and teacher grading) pupils preferred more learner oriented or learner-teacher oriented activities whereas weak students preferred teacher controlled classroom activities. Such findings must be considered when designing a course.During my brief stint as an ESL instructor at a major university in Sri Lanka I began to realize the importance of having a set format for a course. The university ESL course was structured in such a way that learners would first be introduced to a topic of current interest. This would be followed by a listening activity, a reading activity and finally a speaking task in that order. Having this kind of set format is beneficial as it makes the course easier to monitor and fosters learner conf idence, as they become familiar with the learning procedure.Learners are often more comfortable with the predictable than they are with the unpredictable. The fear of â€Å"pop† quizzes is testaments to this, although certain surprise elements do need to be incorporated into course design to prevent students from becoming complacent. These â€Å"surprise† elements may include a role-play activity or a simulation in a traditional grammar-based language course. Course design according to this model is not a linear process. As such, it may be necessary to alter the content or sequencing to suit the lesson format and meet the learning goals. Content must also focus on and facilitate assessment.Assessment Assessment plays a key role in determining if a course has achieved its goals. As such, it is a useful and recurring part of the design process. Of the many ways assessment may be carried out, tests take precedence over the other methods. These tests are an important consi deration in course design. Language courses are associated with both proficiency tests and achievement tests. Proficiency or placement tests are usually held prior to the commencement of a course to determine the learner’s level of language knowledge and which level of the course best fits him or her.Based on this knowledge ESL learners at a major university in Sri Lanka are enrolled in three different courses, simply labeled level one, level two and level three. Level three courses cater to the more proficient learners while level one courses are focused on the needs of learners with little or no knowledge of the target language. These students are subjected to achievement tests that monitor their progress and identify knowledge gaps, at the end of each unit. They are also subjected to a comprehensive achievement test at the end of the course.Such tests elicit valuable information on the effectiveness of the course. As such, designers must pay careful attention to the struct ure of such tests and their place in the overall course design. Curriculum design must also make provisions for the inclusion of other non-test-based assessment such as observation, journal entries, simulation debriefing outcomes and student accounts of their learning. Data gathered from such methods of assessment may in some cases prove to be more valuable than tests in determining the strengths and weaknesses of the course design.The Outermost Circle: Evaluation Evaluation Apart from using assessment data, a course maybe evaluated via learner and instructor input gathered through surveys, interviews and focus groups. This information will determine whether the course meets the required standards, is deficient and needs improvement or needs to be discontinued. Although immediate or formative evaluation of a course is vital, the true worth of a language course can be evaluated only after some time has elapsed allowing learners to utilize the knowledge and skills gained from the cour se in the desired setting.The effectiveness of a language course in my view lies in how it has impacted the life of the learner. In this regard summative evaluation is an important part of the design process. The evaluation process maybe regarded as a backstage process that is imperative for the successful completion and realization of center stage processes such as setting realistic and purposeful goals and content. Responsible curriculum design must therefore include ongoing evaluation of the course. Conclusion The ESL Course Design model serves language teachers in course design, which is often seen as an arduous task.It portrays course design as a process and emphasizes the importance of considering learner needs, resources and applied linguistic research as a practical and theoretical basis for course design. According to the model, this knowledge will hold designers in good stead as they proceed to the other vital components of course design. Goals, content, format and present ation and assessment are all vital aspects of this model that must be given equal consideration. Evaluation too, is given prominence and designers are advised to conduct continuous evaluations to ensure that the curriculum design is effective and viable.The ESL Course Design model testifies to the fact that course design is not a linear or static process. It also implies that ESL course design is a constantly evolving process that needs careful consideration and planning. References De Silva, R. (2001). Students’ perceptions of the English teaching / language experience in the classroom. In David Hays (Ed. ), Teaching English: Possibilities and opportunities ( pp. 85-91). Colombo: The British Council. Hill, J. L. (2002). Playing with the three pigs. Simulation Gaming, 33 (3), 353-359. Gredler, M. (1994). Design evaluation games simulation: A process approach.Texas: Gulf Publishing Company. Gustafson, K. , Branch, R. (Ed. ). (1997). Survey of instructional development mode ls (3rd Ed). New York. Eric Clearinghouse. Kidd, R. , Marquardson, B. (1994, March). The Foresee approach. Paper presented at the annual meeting of the teachers of English to speakers of other languages, Baltimore, MD. Valdez, M. (1999). How learners’ needs affect syllabus design. Forum, 37(1), 30-34. Format Assessment Presentation Content Sequencing Goals Needs Research Resources Delivery Evaluation Evaluation Evaluation Evaluation Evaluation

Demonstrative Adjectives in Spanish

Demonstrative Adjectives in Spanish Demonstrative adjectives are those adjectives whose function is to point at something. In English, the singular demonstrative adjectives are this and that, while their  plurals are these and those, respectively. (Some grammarians refer to them as demonstrative determiners.) Key Takeaways: Spanish Demonstrative Adjectives The demonstrative adjectives or determiners of Spanish - este, ese, and aquel along with their plural and feminine forms - are used in much the same was as this, that, these, and those are used as adjectives or determiners in English.Both ese and aquel are rough equivalents of that. Aquel is used in referring to entities that are further away in time, distance, or emotional sentiment than entities that use ese.When demonstratives are used with items in a series, they typically are used for each item, unlike in English. Unlike English, Spanish has three sets of demonstrative adjectives, which vary by number and gender, so there are 12 in all: singular masculineeste (this)ese (that)aquel (that)plural masculineestos (these)esos (those)aquellos (those)singular feminineesta (this)esa (that)aquella (that)plural feminineestas (these)esas (those)aquellas (those) Note that the masculine singular forms dont end in -o. Where To Place Demonstrative Adjectives The demonstrative adjectives typically are placed before the nouns they modify. They must match the noun in both number and gender. A few examples: Me gusta este perro. (I like this dog.)Prefiero estas computadoras. (I prefer these computers.)Voy a comprar ese coche. (Im going to buy that car.)Me gustan aquellas casas. (I like those houses.) Ese or Aquel? Although ese and aquel and their related forms can be translated as that or those, there are distinctions in meaning. Ese and its related forms are more common, and youre generally safe to use them when in English youd use that or those. However, aquel and its related forms refer to something thats farther away in terms of distance, emotion, or time. Although ese and its forms can be used for an object near the speaker or listener, aquel cannot. The distinction, if not made clear by context, can be translated in various ways, as these examples indicate: Me gustan esos perros. (I like those dogs.)Me gustan aquellos perros. (I like those dogs over there.)No quiero esa casa. Quiero aquella casa. (I dont want that house. I want that house farther back.) ¿Recuerdas esos dà ­as? (Do you remember those days?) ¿Recuerdas aquellos dà ­as? (Do you remember those days long ago?) Items in a Series When two or more items are in a series, the demonstrative adjective must be used with each item. While in English we would say those dogs and cats, in Spanish we would say esos perros y esos gatos. Use of just one demonstrative adjective in this case, as in esos perros y gatos, would imply that were talking about animals that are a cross between a cat and a dog. Sample Sentences Using Demonstrative Adjectives Perseverancia: Pocos entienden el valor de esa palabra. (Perseverance: Few understand the value of that word.) Esta idea puede cambiar tu futuro. (This idea can change your future.) Siempre que veo la televisià ³n y veo a esos pobres nià ±os hambrientos en todo el mundo, no puedo evitar llorar. (Whenever I watch television and see those poor hungry children everywhere, I cant keep from crying.) Yo sabà ­a que era este mes pero no ese dà ­a. (I knew that it was this month but not that day.) Vuelvo a vivir aquellas experiencias que tuve hace muchos aà ±os. (Im going to relive those experiences I had many years ago.) Estas manos pueden construir una casa. (These hands can build a house.) Aquellos ojos azules irradiaban una luz que era casi tangible. (Those blue eyes radiated a light that was almost tangible.) Gracias por esa leccià ³n de vida. (Thank you for that lesson in life.) Esta persona no es mi amigo. (This person is not my friend.) Hay riesgos si abandonamos esas costumbres nuevas y olvida aquellas enseà ±anzas milenarias. (There are risks if we abandon those new customs and forget those traditional teachings.) Se llama radiogalaxia a aquella galaxia que irradia energà ­a con gran potencia en forma radioondas. (That galaxy that radiates powerful energy in the form of radio waves is called a radio galaxy.)   Aquel aà ±o descubrà ­ que mi à ºnico rival no era ms que mis propias debilidades. (That day I discovered that my only enemy wasnt anything more than my own weaknesses.)

PSAT Test Dates 2017

PSAT Test Dates 2017 SAT / ACT Prep Online Guides and Tips Attention, 2017 juniors! Do you know when you’ll be taking the PSAT? Do you know the best way to prepare for the test? This guide is for anyone planning to take the PSAT in the fall of 2017. We have the predicted PSAT test dates, along with some key study tips. To start, let’s discuss what you need to know about how your school will administer the PSAT. How Will Your High School Administer the PSAT? Unlike the SAT or ACT, you don’t get to choose when you take the PSAT. Instead, your school administers the PSAT on one date in the fall. All juniors automatically take the PSAT, while younger students can request to take it if they want the experience. College Board gives schools three options for PSAT test dates, a primary test date, an alternate test date, and a Saturday test date. The majority of schools choose the primary test date, which falls on a Wednesday. Your school will only administer the PSAT on its one selected test date. College Board hasn’t released the exact 2017 PSAT test dates yet, but we can predict the dates based on previous years. Read on for the predictedPSAT test dates in 2017. With the PSAT, you don't get to choose your test date. What Are the 2017 PSAT Test Dates? Every year the primary PSAT test date falls on a Wednesday in mid-October. The alternate test date will be offered two weeks later, while the Saturday test date will fall within a few days ofthe primary test date. Here are the officialPSAT test dates 2017: Primary date: Wednesday, October 11 Alternate Date: Wednesday,October 25 Saturday Date: Saturday, October 14 Since your school only administers the PSAT once, you should try your hardest to be there. Of course, you can’t help it if you come down with the flu or have a family emergency. If you miss your PSAT test date for whatever reason, can you still take the test? When the days start to cool and the leaves change color, PSAT season is upon you. What If You Miss the 2017 PSAT Test Date? Even though your school only administers the PSAT once, it is possible to retake the test if you’re absent on test day. If you miss the PSAT, then you’ll have to contact the National Merit Scholarship Corporation (NMSC) with a written request to take it by March 1. Here’s what the NMSC website says about scheduling a makeup PSAT: â€Å"The student or a school official must write to NMSC as soon as possible after the PSAT/NMSQT administration to request information about procedures for entry to NMSC competitions by alternate testing. The earlier NMSC receives the written request, the greater the student’s opportunities for meeting alternate entry requirements. To be considered, a request must be postmarked no later than March 1 following the PSAT/NMSQT administration that was missed. NMSC will provide alternate entry materials including an entry form that requires the signature of a school official.† While you can schedule a retest if you miss the PSAT, you really only need to take this step if you’re aiming for National Merit distinction or scholarships. If you’re not, then you could instead simply take a timed PSAT practice test on your own. While you won’t get the official testing experience, you can still take and score the test, analyze your results, and reflect on your performance to help you prep for the SAT. For students who are able to take the PSAT on its official test date, how long will they have to wait to get their scores? If you miss the PSAT, you probably only need to schedule a makeup test if you're aiming for top, National Merit-qualifying scores. When Will You Get PSAT Scores? PSAT scores willcome out a couple of months after you take the test, sometime in mid-December. You’ll be able to access them online via your College Board account. School counselors should have access to the scores one day earlier than students. Your school should also distribute paper score reports around the end of the month. Beside your total scores, what feedback will you see on your PSAT score report? What Will Your PSAT Score Report Look Like? Your PSAT score report will tell you how you scored on the entire test, as well as how you scored on each section. Your total scores will fall between 320 and 1520. This scale, by the way, is 80 points lower than the SAT scale to account for the fact that the PSAT is a slightly easier test. You’ll also get a score between 160 and 760 for Evidence-based Reading and Writing, and a score between 160 and 760 for math. Your test performance will be further broken down with three section scores between 8 and 38, one each for Reading, Writing and Language, and Math. Finally, you’ll get a Selection Index score between 48 and 228. The National Merit Scholarship Corporation uses this Selection Index to name Commended Students and Semifinalists. Each state has a different Selection Index cutoff to qualify. We estimate that the average state cutoff to qualify as National Merit Semifinalist will be 214. Whether you’re aiming for National Merit or getting ready for the PSAT and SAT, you should take time to study for the PSAT. Read on for some essential PSAT prep tips. Your PSAT score report slices through your results toreveal all the layers of your test performance. How to Prep for the PSAT No one should go into the PSAT without knowing what to expect. There are lots of available practice materials that will help you learn about the test and get some experience with PSAT questions. The following seventips will help guide your prep for the PSAT. We also have in-depth articles that illuminate every aspect of the test, plus give some key test-taking and time management strategies to help you do your best. Your first step in PSAT studying is simply familiarizing yourself with the content, format, and scoring of the test. Want to improve your PSAT score by 150 points? We have the industry's leading PSAT prep program. Built by Harvard grads and SAT full scorers, the program learns your strengths and weaknesses through advanced statistics, then customizes your prep program to you so that you get the most effective prep possible. Check out our 5-day free trial today: #1: Familiarize Yourself With the Test First things first, set aside some time tolearn all about the PSAT. Learn about how the test is structured, how much time you have for each section, and when you get breaks. Figure out what skills are tested in Reading, what grammar rules you need to know for Writing, and what the difference is between the Math No Calculator and Math With Calculator sections (besides, of course, whether or not you can use a calculator). As you learn, take notes on theskills and concepts you feel confident about and which ones need review. Keep track of the areas where you’ll need to spend the most time studying. You can use these notes to design a study plan that targets your weak areas and fills in any gaps in knowledge. Your first step in preparing for the PSAT is learning all about the PSAT. In other words, you should make the PSAT your new best friend. #2: Make a Study Schedule To meet your goals on the PSAT, you need to design a study schedule customized to you. You should think about how much time you have before the PSAT, and how much of that time you can realistically commit to test prep. Ideally, you can set aside the same time each week so that your PSAT prep becomes part of your routine. Just a few hours of prep a week can add up to dozens or even hundreds of hours if you start early enough. Take time to design a schedule, write it down, and stick to it. By developing a consistent habit of PSAT prep, you’ll see significantprogress over time. #3: Take a Timed Practice Test When you start studying, you should sit down and take a full PSAT practice test. Find a quiet environment, time yourself, and score your test. By simulating the test day experience, you can get a sense of your current scoring level. Then you can use this practice test to diagnose your strengths and weaknesses as a test-taker. Take time to figure out your section scores and pinpoint your weaknesses. Where do you see the most room for improvement? By taking a practice test at the beginning, you can figure out where you need to put in the most work to see improvement. Take timed practice tests to get a sense of the pacing of the PSAT. With enough practice, you'll manage to stay afloat despitethe strict time limits. #4: Analyze Your Results Once you’ve scored your test, you should go back through and circle all of the questions that you got wrong or where unsure about. Look for patterns in questions that tripped you up. Perhaps you need to work on time management in the Reading section. Maybe you need to review geometry concepts and memorize more formulas. Think deeply about the reasons you got a question wrong. Were you missing some core knowledge, or did you make a careless error because you were rushing? Memorizing grammar rules won’t help your Writing score if what you really need is better time management strategies. Getting to the root of your issues will help you address them directly and effectively. #5: Review Core Concepts While strategy is important on the PSAT, you also need to possess certain core knowledge to do well on it. You’ll need to understand specific rules of grammar, certain literary terms, key math formulas, and concepts of algebra and geometry. Make sure your PSAT study materials break down each section into its component concepts. After reviewing a concept, you should answer relevant practice questions to reinforce your understanding. If you come across a concept that you haven’t learned yet in school, you might seek help from a peer or teacher or try to learn it on your own with PSAT study materials. Filling in any gaps in knowledge is especially key if you’re aiming for top scores. Even if the PSAT calls itself a skills-based, rather than content-basedtest, it still requires that you've memorized some facts and figures. #6: Get Strategic Unfortunately, even academically excellent students aren’t guaranteed a high score on the PSAT without a solid understanding of test-taking strategy. The PSAT is a fast-paced test that requires deft time management. By practicing with timed tests, you’ll be able to get more and more efficient and less prone to careless errors. You shouldalso try outspecificstrategies, like process of elimination or speed-reading passages, to improve your speed while maintaining accuracy. #7: Practice, Practice, Practice Becoming a good PSAT-taker is a learned skill, just like writing or playing the guitar. You can’t expect to get great scores the first time you take a practice test. Rather, you’ll get better and better the more you practice. Ideally, you can start several months before your test date and commit one to three hours to PSAT prep each week. As you get closer to the test, you can ramp up the time commitment, if possible. However, you’ll already have accumulated many study hours, so you won’t have to panic and cram at the last minute.By the time the PSAT rolls around, all the skills you’ve developed will kick in and carry you across the finish line of your PSAT goals. Now that you have a sense of when you’ll take the PSAT and how you can start preparing for it, let’s go over the key points you should remember about this important test. Just as youcan't expect to know how to play the guitar without any practice, you also shouldn't expect to ace the PSAT without some serious prep work. PSAT Test Dates 2017: Key Points If you’ll be a junior in 2017, then you’ll be taking the PSAT in the fall. In all likelihood, you’ll take the PSAT on a Wednesday in mid-October.Our projected 2017 PSAT dates are Wednesday, October 18, Wednesday, November 1, andSaturday, October 15. The PSAT is a unique test, probably unlike othertests you take in school. To achieve your target scores, you should take time to review material and try out test-taking strategies. With enough practice, you might qualify for National Merit distinction and scholarships. Regardless of whether or not you make this competitive cutoff, you’ll still benefit from prepping for the PSAT. The test is extremely similar to the SAT, so any prep you do now will help you when you take the college admissions test. Taking the PSAT is a skill that you can learn and improve with practice. The more effort you put in beforehand, the more comfortable and confident you’ll feel when test day rolls around. What’s Next? Are you aiming for top scores on the PSAT? For any aspiring National Merit Finalists, this guide tells you what it takes to get a perfect score on the PSAT. What PSAT score do you need to qualify for National Merit? This guide breaks down the predicted state-by-state cutoffs to make Semifinalist status. If you were named a National Merit Semifinalist, how do you move on to become a Finalist and earn scholarship money? Check out this full guide on becoming a National Merit Finalist to find out. Want to improve your SAT score by 160 points or your ACT score by 4 points?We've written a guide for each test about the top 5 strategies you must be using to have a shot at improving your score. Download it for free now:

Teenage pregnancy Research Paper Example | Topics and Well Written Essays - 1500 words

Teenage pregnancy - Research Paper Example Previously it was believed that teen pregnancies are usually because of socio-economic factors, lack of sex related services and decreased contraception but nowadays this view is challenged by many as all these aspects have been overcome by the growing society (Kost et al 2010). It is a belief that the economic burden that is passed unto teenagers who become pregnant can put a significant strain on the possibility of a brighter future. Moreover, it could be argued that abortion can help alleviate a cycle of poverty in women who themselves are the result of teenage pregnancy. Therefore, abortions are the answer for a pregnant teenager in view of her health, future and career. Different Views on Abortion Smith (2001) carries out a study to explore the negative and adverse effects of teenage pregnancy in the form of premature delivery and stillbirth. The study is carried out in order to understand the adverse perinatal outcomes in teenage pregnancy cases. Teenagers are at a lower risk o f unhealthy outcomes when given 1st birth. Moreover, the risk of caesarean is also loweramong teenage mothers in the first delivery. However, Smith (2001) reveals that second delivery of a teenage mother is highly risky in terms of caesarean and premature or still birth. There is an increase in the teenage pregnancies between the years 2005 and 2006 by 3% (Lewin 2010). The teenage abortion rate has also been increased by approximately 1 percent from 2005 to 2006. These increasing rates are related to the struggles made by government in order to curb this issue. The "abstinence-only programs" supported by Clinton's government are called into question. However, the pregnancy rates are significantly lower in 2005 at 69.5 as compared to 116.9 in 1990. The only issue that is gaining increasing attention from the opposition is the increased rate in 2007 of 71.5 in 2006. Lewin (2010) forms an opinion that Blacks, Hispanics and Whites are all showing increasing trends on teenage pregnancies in the recent years. Teen pregnancy is generally believed to be harmful by many for not only the pregnant woman but also for the baby. Teenage pregnancy can pose health risks to the baby because the teenager woman would not be capable enough to take care of the baby at such a tender age. Similarly the teenager woman would also not be able to support her child financially and thus this would disrupt safety and life plans for the baby. The only way out of these issues to teenagers is abortion. This interruption in pregnancy leads to increased risk of breast cancer among the teenagers (Melbye et al. 1997). The study suggests that the breast cells are proliferated quickly without following the normal procedure which protects the health of the woman. There are certain positive aspects of teenage pregnancy and motherhood which keep the trend going. Seamark (2004) provides a valuable study in this regard by interviewing teenage mothers to evaluate their experiences of having children at a n early age. The responses were quite positive as the teenage mothers tend to be positive in their perceptions, goals and feel more motivated towards their aims by the responsibility of their children. They show a positive attitude towards the busy yet ambitious life to protect and help the children grow healthy and contented (Seamark 2004). The teenage pregnan

Cyber Warfare in China Term Paper Example | Topics and Well Written Essays - 5000 words

Cyber Warfare in China - Term Paper Example Moreover, it is difficult to identify the sources of attack since the hackers can strike the target precisely without leaving many evidences about the culprits. Cyber warfare will involve disruption of crucial network services and data, damage to critical infrastructure, and the creation of uncertainty and doubt among opposing commanders and political leaders. Cyber-attack provides an ability to strike both tactical and strategic targets from a distance using inexpensive systems China is often been accused for its involvement in cyber warfare with its enemy countries like America, India etc. People’s Liberation Army (PLA) of China is accused for conducting cyber warfare with many other countries. In fact, â€Å"PLA takes cyber war seriously as this kind of warfare offers an immediate way for the country to overcome the superiority of the U.S. in warfare techniques and weaponry† . America is one country which has superior military power than China. Based on the current capabilities, it is difficult for China to attack America directly. So, they are believed to be causing huge problems to America with the help of cyber warfare. Same way, India is another country which is working against the interests of China. India’s has frontier disputes with China. Moreover, the acceptance given to the Tibetan leader Dalai Lama by India is indigestible to China. So they are causing huge problems to India with the help of cyber warfare. Because of the necessities of instant interchange of information between countries located at different parts of the world, most networks and the computers in the world are connected in some ways. In a heavily globalized world, it is difficult for a country to isolate its computer networks from global networks. Moreover, majority of the computers in the networks are using same operating systems and networking technologies because of the monopoly of some companies in these sectors. For example, Windows is used as the operating system in majority of the computers all over the world. Same way, TCP/IP protocols are used in majority of the computer networks. Although a completely accurate map of the overall Net has not been produced, it is logical to reason that the 95% of privately owned networks are connected to each other in some way. The interoperability benefits of standardized protocols and the spread of recently devised worms and viruses such as Nimda and Sasser are testament to th e links between these networks4. China has superior internet related technologies compared to many other countries in the world. Moreover, many of the Chinese youths are currently getting training on computer software. China knows very well that they can cause huge problems to enemies silently and escape from getting punished by others. â€Å"After land, sea, air and space, warfare has entered the fifth domain: cyberspace†5. Until recent times, military powers were keen in accumulating arms and for land, sea, air and space attacks and defense. However, the development of internet or cyber space opened another domain for

Six Stroke Ic Engine Essay Example for Free

Six Stroke Ic Engine Essay 1. INTRODUCTION A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber during the final stage of compression. Diesel engines have wide range of utilization for automobiles, locomotives marines and co-generation systems. However, large problem is still related to undesirable emission. The six-stroke engine is a type of internal combustion engine based on the four-stroke engine but with additional complexity to make it more efficient and reduce emissions. Two different types of six-stroke engine have been developed: In the first approach, the engine captures the heat lost from the four-stroke Otto cycle or Diesel cycle and uses it to power an additional power and exhaust stroke of the piston in the same cylinder. Designs use either steam or air as the working fluid for the additional power stroke. The pistons in this type of six-stroke engine go up and down three times for each injection of fuel. There are two power strokes: one with fuel, the other with steam or air. The currently notable designs in this class are the Crower Six-stroke engine invented by Bruce Crower of the U.S. ; the Bajulaz engine by the Bajulaz S.A. company of Switzerland; and the Velozeta Six-stroke engine built by the College of Engineering, at Trivandrum in India. The second approach to the six-stroke engine uses a second opposed piston in each cylinder that moves at half the cyclical rate of the main piston, thus giving six piston movements per cycle. Functionally, the second piston replaces the valve mechanism of a conventional engine but also increases the compression ratio. The currently notable designs in this class include two designs developed independently: the Beare Head engine, invented by Australian Malcolm Beare, and the German Charge pump, invented by Helmut Kottmann. To improve exhaust emissions from diesel engines, a new concept of Six Stroke Engine has been proposed. This engine has a second compression and combustion processes before exhaust process. [pic] Fig 1 Diesel engine sectional view Fig 2 Ideal Otto cycle [pic] Fig 3 Pressure- Volume diagrams for dual cycle As the fuel in one cycle was divided into two combustion processes and the EGR (Exhaust Gas Recirculation) effect appeared in the second combustion process, the decreased maximum cylinder temperature reduced Nitrous Oxide (NO) concentration in the exhaust gas. It was further confirmed that soot formed in the first combustion process was oxidized in the second combustion process .Therefore, a six stroke diesel engine has significant possibilities to improve combustion process because of its more controllable factors relative to a conventional four-stroke engine. Since the cylinder temperature before the second combustion process is high because of an increased temperature in the first combustion process, ignition delay in the second combustion process should be shortened. In addition, typically less desirable low cetane number fuels might also be suitable for use in the second combustion process, because the long ignition delays of these fuels might be improved by increased cylinder temperatures from the first combustion process. Methanol was chosen as the fuel of the second combustion. The cetane number of methanol is low and it shows low ignitability. However, since methanol will form an oxidizing radical (OH) during combustion, it has the potential to reduce the soot produced in the first combustion process. [pic] Fig 4 Comparison of 4 stroke and 6 stroke cycle 2. BAJULAZ SIX STROKE ENGINE The majority of the actual internal combustion engines, operating on different cycles have one common feature, combustion occurring in the cylinder after each compression, resulting in gas expansion that acts directly on the piston (work) and limited to 180 degrees of crankshaft angle. According to its mechanical design, the six-stroke engine with external and internal combustion and double flow is similar to the actual internal reciprocating combustion engine. However, it differentiates itself entirely, due to its thermodynamic cycle and a modified cylinder head with two supplementary chambers: Combustion, does not occur within the cylinder within the cylinder but in the supplementary combustion chamber, does not act immediately on the piston, and it’s duration is independent from the 180 degrees of crankshaft rotation that occurs during the expansion of the combustion gases (work). The combustion chamber is totally enclosed within the air-heating chamber. By heat exchange through the glowing combustion chamber walls, air pressure in the heating chamber increases and generate power for an a supplementary work stroke. Several advantages result from this, one very important being the increase in thermal efficiency. IN the contemporary internal combustion engine, the necessary cooling of the combustion chamber walls generates important calorific losses. 2.1 Analysis: Six-stroke engine is mainly due to the radical hybridization of two- and four-stroke technology. The six-stroke engine is supplemented with two chambers, which allow parallel function and results a full eight-event cycle: two four-event-each cycles, an external combustion cycle and an internal combustion cycle. In the internal combustion there is direct contact between air and the working fluid, whereas there is no direct contact between air and the working fluid in the external combustion process. Those events that affect the motion of the crankshaft are called dynamic events and those, which do not effect are called static events. [pic] Fig 5 Prototype of Six stroke engine internal view 1. Intake valve, 2.Heating chamber valve, 3.Combustion chamber valve,4. Exhaust valve, 5.Cylinder, 6.Combustion chamber, 7. Air heating chamber, 8.Wall of combustion chamber, 9.Fuel injector and 10.Heater plug. 2.1.1 Analysis of events [pic] Fig 6 Event 1: Pure air intake in the cylinder (dynamic event) 1. Intake valve. 2. Heating chamber valve 3. Combustion chamber valve. 4. Exhaust valve 5. Cylinder 6. Combustion chamber. 7. Air heating chamber. 8. Wall of combustion chamber. 9. Fuel injector. 10. Heater plug. [pic] Fig 7 Event 2: Pure air compression in the heating chamber. Event 3: Keeping pure air pressure in closed chamber where a maximum heat exchange occurs with the combustion chambers walls, without direct action on the crankshaft (static event). [pic] Fig 8 Event 4: Expansion of the Super heat air in the cylinder work (dynamic Event). [pic] Fig 9 Event 5: Re-compressions of pure heated air in the combustion chamber (dynamic event). Events 6: fuel injection and combustion in closed combustion chamber, without direct action on the crankshaft (static event). [pic] Fig 10 Events 7: Combustion gases expanding in the cylinder, work (dynamic event). [pic] Fig 11 Events 8: Combustion gases exhaust (dynamic event). [pic] Fig 12 Six-stroke engine cycle diagram: 2.1.2 External combustion cycle: (divided in 4 events): No direct contact between the air and the heating source. e1. (Event 1) Pure air intake in the cylinder (dynamic event). e2. (Event 2) Compression of pure air in the heating chamber (dynamic event). e3. (Event 3) Keeping pure air pressure in closed chamber where a maximum heat exchange occurs with the combustion chambers walls, without direct action on the crankshaft (static event). e4. (Event 4) Expansion of the super heated air in the cylinder, work (dynamic event). 2.1.3 Internal combustion cycle: (divided in 4 events) Direct contact between the air and the heating source. I1. (Event 5) Re-compression of pure heated air in the combustion chamber (dynamic event) I2. (Event 6) Fuel injection and combustion in closed combustion chamber, without direct action on the crankshaft (static event). I3. (Event 7) Combustion gases expanding in the cylinder, work (dynamic event). I4. (Event 8) Combustion gases exhaust (dynamic event). 2.2 Constructional details: The sketches shows the cylinder head equipped with both chambers and four valves of which two are conventional (intake and exhaust). The two others are made of heavy-duty heat-resisting material. During the combustion and the air heating processes, the valves could open under the pressure within the chambers. To avoid this, a piston is installed on both valve shafts which compensate this pressure. Being a six-stroke cycle, the camshaft speed in one third of the crankshaft speed. The combustion chambers walls are glowing when the engine is running. Their small thickness allows heat exchange with the air-heating chamber, which is surrounding the combustion chamber. The air-heating chamber is isolated from the cylinder head to reduce thermal loss. Through heat transfer from the combustion chamber to the heating chamber, the work is distributed over two strokes, which results in less pressure on the piston and greater smoothness of operation. In addition, since the combustion chamber is isolated from the cylinder by its valves, the moving parts, especially the piston, are not subject to any excessive stress from the very high temperatures and pressures. They are also protected from explosive combustion or auto-ignition, which are observed on ignition of the air-fuel mixture in conventional gas or diesel engines. The combustion and air-heating chambers have different compression ratio. The compression ratio is high for the heating chamber, which operates on an external cycle and is supplied solely with pure air. On the other hand, the compression ratio is low for the combustion chamber because of effectively increased volume, which operates on internal combustion cycle. The combustion of all injected fuel is insured, first, by the supply of preheated pure air in the combustion chamber, then, by the glowing walls of the chamber, which acts as multiple spark plugs. In order to facilitate cold  starts, the combustion chamber is fitted with a heater plug (glow plug). In contrast to a diesel engine, which requires a heavy construction, this multi-fuel engine, which can also use diesel fuel, may be built in a much lighter fashion than that of a gas engine, especially in the case of all moving parts. Injection and combustion take place in the closed combustion chamber, therefore at a constant volume, over 360 degrees of crankshaft angle. This feature gives plenty of time for the fuel to burn ideally, and releases every potential calorie (first contribution to pollution reduction). The injection may be split up, with dual fuel using the SNDF system (Single Nozzle, Dual Fuel). The glowing walls of the combustion chamber will calcite the residues, which are deposited there during fuel combustion (second contribution to pollution reduction). As well as regulating the intake and exhaust strokes, the valves of the heating and the combustion chambers allow significantly additional adjustments for improving efficiency and reducing noise. 2.3 Factors Contributing To the Increased Thermal Efficiency, Reduced Fuel Consumption, and Pollutant Emission 1. The heat that is evacuated during the cooling of a conventional engine’s cylinder head is recovered in six-stroke engine by air-heating chamber surrounding the combustion chamber. 2. After intake, air is compressed in the heating chamber and heated through 720 degrees of crankshaft angle, 360 degrees of which in closed chamber (external combustion). 3. The transfer of heat from thin walls of the combustion chamber to the air heating chambers lowers the temperature, pressure of gases on expansion and exhaust (internal combustion). 4. Better combustion and expansion of gases that take place over 540 degrees of crankshaft rotation, 360 ° of which is in closed combustion chamber, and 180 ° for expansion. 5. Elimination of the exhaust gases crossing with fresh air on intake. In the six stroke-engines, intake takes place on the first stroke and exhaust on the fourth stroke. 6. Large reduction in cooling power. The water pump and fan outputs are reduced. Possibility to suppress the water cooler. 7. Less inertia due  to the lightness of the moving parts. 8. Better filling of the cylinders on the intake due to the lower temperature of the cylinder walls and the piston head. 9. The glowing combustion chamber allows the finest burning of any fuel and calcinate the residues. 10. Distribution of the work: two expansions (power strokes) over six strokes, or a third more than the in a four-stroke engine. Since the six-stroke engine has a third less intake and exhaust than a four stroke engine, the depression on the piston during intake and the back pressure during exhaust are reduced by a third. The gain in efficiency balances out the losses due to the passage of air through the combustion chamber and heating chamber valves, during compression of fresh and superheated air. Recovered in the six-stroke engine By the air-heating chamber surrounding the combustion. Friction losses, theoretically high er in the six-stroke engine, are balanced by a better distribution of pressure on the moving parts due to the work being spread over two strokes and the elimination of the direct combustion. 3. DUAL FUEL SIX STROKE ENGINE 3.1 Working The cycle of this engine consists of six strokes: 1. Intake stroke 2. First compression stroke 3. First combustion stroke 4. Second compression stroke 5. Second combustion stroke 6. Exhaust stroke [pic] Fig 13 Concept of a Six-stroke diesel engine 3.1.1 Intake or Suction stroke To start with the piston is at or very near to the T.D.C., the inlet valve is open and the exhaust valve is closed. A rotation is given to the crank by the energy from a flywheel or by a starter motor when the engine is  just being started. As the piston moves from top to bottom dead centre the rarefaction is formed inside the cylinder i.e. the pressure in the cylinder is reduced to a value below atmospheric pressure. The pressure difference causes the fresh air to rush in and fill the space vacated by the piston. The admission of air continues until the inlet valve closes at B.D.C. 3.1.2 First Compression stroke Both the valves are closed and the piston moves from bottom to top dead centre. The air is compressed up to compression ratio that depends upon type of engine. For diesel engines the compression ratio is 12-18 and pressure and temperature towards the end of compression are 35-40 kgf/cm2 and 600-700 0C 3.1.3 First combustion stroke This stroke includes combustion of first fuel (most probably diesel) and expansion of product of combustion. The combustion of the charge commences when the piston approaches T.D.C. Here the fuel in the form of fine spray is injected in the combustion space. The atomization of the fuel is accomplished by air supplied. The air entering the cylinder with fuel is so regulated that the pressure theoretically remains constant during burning process. In airless injection process, the fuel in finely atomized form is injected in combustion chamber. When fuel vapors raises to self ignition temperature, the combustion of accumulated oil commences and there is sudden rise in pressure at approximately constant volume. The combustion of fresh fuel injected into the cylinder continues and this ignition is due to high temperature developed in engine cylinder. However this latter combustion occurs at approximately constant pressure. Due to expansion of gases piston moves downwards. The reciprocating motion of piston is converted into rotary motion of crankshaft by connecting  rod and crank. During expansion the pressure drop is due to increase in volume of gases and absorption of heat by cylinder walls. 3.1.4 Second compression stroke Both the valves are closed and the piston moves from bottom to top dead centre. The combustion products from the first compression stroke are recompressed and utilized in the second combustion process before the exhaust stroke. In typical diesel engine combustion the combustion products still contains some oxygen. 3.1.5 Second combustion stroke This stroke includes combustion of second fuel having low cetane (Cetane number of fuel is defined as percent volume of cetane (C16H34) in a mixture of cetane and alpha-methyl-naphthalene that produces the same delay period or ignition lag as the fuel being tested under same operating conditions on same engine). The combustion of the charge commences when the piston approaches to TDC. The second fuel injected into recompressed burnt gas can be burnt in the second combustion process. In other words combustion process of the second fuel takes place in an internal full EGR (Exhaust Gas Recirculation) of the first combustion. This second combustion process was the special feature of the proposed Six Stroke DI Diesel Engine. 3.1.6 Exhaust stroke The exhaust valve begins to open when the power stroke is about to complete. A pressure of 4-5 kgf/cm2 at this instant forces about 60% of burnt gases into the exhaust manifold at high speed. Much of the noise associated with automobile engine is due to high exhaust velocity. The remainder of burnt gases is cleared of the swept volume when the piston moves from TDC to BDC. During this stroke pressure inside the cylinder is slightly above the atmospheric value. Some of the burnt gases are however  left in the clearance space. The exhaust valve closes shortly after TDC. The inlet valve opens slightly before the end of exhaust stroke and cylinder is ready to receive the fresh air for new cycle. Since from the beginning of the intake stroke the piston has made six strokes through the cylinder (Three up And Three down). In the same period crank shaft has made three revolutions. Thus for six stroke cycle engine there are two power strokes for every three revolutions of crank shaft. 3.2 Performance analysis 3.2.1 Modification over four stroke diesel engine This six-stroke diesel engine was made from a conventional four-stroke diesel engine with some modification. A sub-shaft was added to the engine, in order to drive a camshaft and injection pumps. The rotation speed of the sub-shaft was reduced to 1/3 of the rotation of an output shaft. To obtain similar valve timings between a four-stroke and a six-stroke diesel engine, the cam profile of the six-stroke diesel engine was modified. In order to separate the fuels, to control each of the injection timings and to control each injection flow rate in the first and the second combustion processes, the six-stroke diesel engine was equipped with two injection pumps and two injection nozzles. The injection pumps were of the same type as is used in the four-stroke diesel engine. The nozzle is located near the center of a piston cavity, and has four injection holes. For the six-stroke diesel engine, one extra nozzle was added on the cylinder head. This extra nozzle was of the same design as that of the four-stroke engine. [pic] Fig 14 Volume –Angle diagram for six stroke engine Diesel fuel for the first combustion process was injected through this extra nozzle, and methanol for the second combustion process was injected through the center nozzle. Here, we denoted the injection timing of the four  stroke diesel engine as Xi. The injection timings of the first and second combustion strokes for the six-stroke diesel engine are shown as Xi I and Xi II, respectively. Crank angle X was measured from the intake BDC. In the six-stroke engine, crank angle of the first combustion TDC is 180 degrees. The second combustion TDC is 540 degrees. Specifications of the test engines are shown in Table 1. The conventional four-stroke diesel engine that was chosen as the basis for these experiments was a single cylinder, air cooled engine with 82 mm bore and 78 mm stroke. The six-stroke engine has the same engine specifications except for the valve timings. However, the volumetric efficiency of the six-stroke engine showed no significant difference from that of the four-stroke engine. Characteristics of the six-stroke diesel engine were compared with the conventional four-stroke diesel engine. In this paper, the engine speed (Ne) was fixed at 2,000 rpm. Cylinder and line pressure indicators were equipped on the cylinder head. NO concentration was measured by a chemiluminescence’s NO meter, and soot emission was measured by a Bosch smoke meter. The physical and combustion properties of diesel fuel and methanol are shown in Table. 2. Since combustion heats of diesel fuel and methanol are different, injection flow rates of the first and the second combustion processes are defined by the amount of combustion heat. Here, the supplied combustion heat for the first combustion process is denoted by QI. The second combustion stroke is denoted by QII. The ratio of QII to Qt (Qt = QI+QII) supplied combustion heat per cycle) is defined as the heat allocation ratio ÃŽ ±H: ÃŽ ±H = QII = QII QI +QII Qt Table 1. Specifications of the test engine: Four stoke Six stroke Diesel Engine Diesel Engine Engine type DI, Single cylinder, Air cooled, OHV Bore x Stroke [mm] 82 x 78 Displacement [cc] 412 Top Clearance [mm] 0.9 Cavity Volume [cc] 16 Compression ratio 21 Intake Valve Open100 BTDC70 BTDC Intake valve Close1400 BTDC1450 BTDC Exhaust Valve Open1350 ATDC1400 ATDC Exhaust Valve Close120 ATDC30 ATDC Valve Overlap 220 100 Rated power 5.9 kW /3000rpm Base Engine - Table 2. Physical and combustion properties of diesel fuel and methanol: | |Diesel Fuel |Methanol | |Combustion heat [MJ/kg] |42.7 |19.9 | |Cetane number |40-55 |3.0 | |Density [kg/m2] |840 |793 | |Theoretical air-fuel ratio |14.6 |6.5 | 3.3 Performance of six stroke diesel engine 3.3.1 Comparison with four stroke diesel engine A four-stroke engine has one intake stroke for every two engine rotations. For the six-stroke engine, however, the intake stroke took place once for every three engine rotations. In order to keep the combustion heat per unit time constant, the combustion heat supplied to one six-stroke cycle should be 3 or 2 times larger than that of the four-stroke engine. There are many ways to compare performance between the four-stroke and six-stroke engines. For this paper, the authors have chosen to compare  thermal efficiency or SFC at same output power. If the thermal efficiency was the same in both engines, the same output power would be produced by the fuels of equivalent heats of combustion. Therefore, in order to make valid comparison, fuels supplied per unit time were controlled at the same value for both engines and engine speeds were kept constant. In this section, fuel supplied for the engines was only a diesel fuel. Performance of the six-stroke engine was compared with that of the four-stroke engine under various injection timings. Detailed conditions for comparison of the four-stroke and six-stroke engines are listed in Table. 3. The heat allocation ratio of the six-stroke engine was set at ÃŽ ±H = 0.5. Injection flow rate of fuel was Qt4 = 0.50 KJ/cycle for the four-stroke engine and Qt6 = 0.68 KJ/cycle for the six stroke engine. For six stroke engine, it meant that the amount of 0.34KJ was supplied at each combustion process. At the viewpoint of combustion heat, 0.75 KJ/cycle of heat should be supplied for the six stroke engine to make the equivalence heat condition. However diesel fuel of 0.68 KJ/cycle was supplied here because of difficulties associated with methanol injection. Injection timing of the four-stroke engine was changed from 160 degrees (200BTDC) to 180 degrees (TDC). For six -stroke engine, the injection timing of the first combustion process was fixed to 165 degrees (15 °BTDC) or 174 degrees (6 °BTDC), and the second injection timing was changed from 520 degrees (2000 BTDC) to 540 degrees (TDC). [pic] Fig 15 Valve timing diagram four stroke engine Table 3. Detailed conditions of comparison between the four stroke and six stroke diesel engines and performance of engine | |Four Stroke |Six Stroke | |Engine Parameters |Diesel Engine |Diesel Engine | |Engine Speed Ne [rpm] |2007 |2016 | |Supplied combustion heat per cycle | | | |Qt [KJ/cycle] |0.50 |0.68 | |Supplied combustion heat per unit time Ht [KJ/s] | | | | |8.36 |7.62 | |Intake air flow per cycle | | | |Ma [mg/cycle] |358.7 |371.4 | |Injection quantity per cycle | | | |Mf [mg/cycle] |11.8 |16 | | | | | |Excess air ratio ÃŽ » |2.40 |1.83 | |Intake air flow per unit time | | | |Ma [g/cycle] |6.00 |4.16 | |Injection quantity per unit time | | | |Mf [g/sec] |0.197 |0.179 | |Brake torque Tb [N-m] |15.52 |15.28 | |Brake power Lb [KW] |3.26 |3.24 | |BSFC. b [ g / KW-h] |217.9 |520.3 | |IMEP Pi [Kgf / cm2] |5.94 |4.37 | |Indicated torque Ti [N-m] |19.10 |18.71 | |Indicated power Li [KW] |4.01 |3.75 | |ISFC bi [g / KW-h ] |177.2 |163.3 | Indicated torque of the six-stroke engine is almost same level with that of the four-stroke engine under various injection timings. NO concentration in exhaust gas of the six-stroke engine was lower than that of the four-stroke engine. NO emissions from both engines were reduced by the retard of injection timing. The effect of retard in the second injection timing of the six-stroke engine was similar to that of the retard in the four-stroke engine. For the six-stroke engine, from the comparison between Xi I = 165 degrees (15 °BTDC) and Xi I = 174 degrees (6 °BTDC), it seemed that the NO reduction effect appeared with the timing retard in the first combustion process. Soot emission in the exhaust gas of the four-stroke engine was low level and it was not affected by the timing retard of injection. However, the level of soot emission from the six-stroke engine was strongly affected by the timing of the second injection. When the injection timing was advanced from 528 degrees (12 ° BTDC), it was confirmed that the soot emission was lower than that of the four-stroke engine. From numerical analysis, it was considered that the soot formed in the first combustion process was oxidized in the second combustion process. On the contrary, when the injection timing was retarded from 528 degrees (12 ° BTDC), soot emission increased with the timing retard. Then, it was considered that the increased part of the soot was formed in the second combustion process because an available period for combustion was shortened with the retard of injection timing. Experimental conditions were Xi = Xi I = 170 degrees (100 BTDC) and XiII=530 degrees (100 BTDC). The heat allocation ratio of six stroke engine was ÃŽ ±H=0.5. The cylinder temperature and heat release rate were calculated from the cylinder pressure. The pattern of heat release rate in the first combustion stroke of the six-stroke engine was similar to that of the heat release rate of the four-stroke engine. It was the typical combustion pattern that contained a pre-mixed combustion and diffusion combustion. On the other hand, since an increase of cylinder temperature in the second combustion process was caused by the compression of the burned gas formed in the first combustion stroke, a pre-mixed combustion in the second combustion process was suppressed by a short ignition delay. The maximum cylinder temperature in the first combustion process was lower than that in the four-stroke engine. It was caused by smaller amount of fuel which was injected in the first combustion process. Considering these results, it was proved that NO concentration in the exhaust gas was reduced by the decrease of the maximum cylinder temperature in the first co mbustion process and EGR effect in the second combustion process. The performance of these two engines could be compared by Table. 3. Since BSFC of the six-stroke engine obtained by the brake power suffered, SFC is compared with ISFC for the Xi = 163 degree (170 BTDC), ISFC of the four-stroke engine was 177.2 g/KW-h. On the other hand, for the Xi I = 165 degrees (15 ° BTDC) and Xi II = 523 degrees (170 BTDC), I.S the six-stroke engine was 163.3 g/KW-h. i.e. ISFC of the six-stroke engine was slightly lower than that of the four-stroke engine. It was considered that this advantage in ISFC was caused by a small cut-off ratio of constant pressure combustion. Because, in the six-stroke engine proposed here, the fuel divided into two combustion processes resulted in a short combustion period of each combustion process. Furthermore, in the reduction of NO emission, the six-stroke engine was superior to the four-stroke engine. 3.3.2 Effect of heat allocation ratio Injection conditions were Xi I = 170 degrees (1000 BTDC) and Xi II = 530 degrees (100 BTDC). Both fuels in the first and second combustion processes were diesel fuel. Total fuel at the combustion heat basis was Qt = 0.68 KJ/cycle. It meant a high load in this engine because the total excess air ratio was 1.83 as previously shown in Table 3. The maximum value of the indicated torque appeared around ÃŽ ±H = 0.5 NO concentration in exhaust gas was reduced by an increase of heat allocation ratio. In other words, NO emission decreased with an increase of the fuel of the second combustion process. In the case of ÃŽ ±H = 0.5, there is a relatively long ignition delay in the first combustion process and pre-mixed combustion was the main combustion phenomena in it. NO of high concentration was formed in this pre-mixed combustion process. On the other hand, in the case of ÃŽ ±H = 1, diffusion combustion was the main combustion phenomena and NO emission was low. Soot emission in exhaust gas increased with an increase of heat allocation ratio. Since the injection flow rate in the second combustion process increased with an increase of the heat allocation ratio, the injection period increased with an increase of the heat allocation ratio. It caused the second combustion process to be long, and unburnt fuel that was the origin of soot remained after the second combustion process. The heat release rates on ÃŽ ±H = 0.15 and ÃŽ ±H = 0.85. For ÃŽ ±H =0.15, since injection flow rate in the first combustion process was high and injection period in it was long, the combustion period in the first combustion process became long as compared with case of ÃŽ ±H = 0.85. On the other hand, for ÃŽ ±H = 0.85, the combustion period in the second combustion process became long as compared with case of ÃŽ ±H=0.15. It was also observed that the long combustion periods in both the first and second combustion were caused by the long diffusion combustion. Further, diffusion combustion was the main combustion phenomena of the second combustion process. When the heat allocation ratio was 0.85, the ratio of heat release rates between the first and second combustion should be 15: 85, however the actual ratio obtained from the figure was 46: 54. This inconsistency was caused from the drift of the base lines of the heat release diagrams. For ÃŽ ±H = 0.15, the actual ratio of heat release rates was 73: 27 with the similar reason. The cylinder temperature for the ÃŽ ±H = 0.15 condition was higher than that of the ÃŽ ±H = 0.85 condition. This could be explained as follows. In the first combustion stroke, since the injection flow rate of ÃŽ ±H = 0.15 was higher than that of ÃŽ ±H = 0.85, the combustion temperature for the ÃŽ ±H = 0.15 condition was higher than that of ÃŽ ±H = 0.85. In the second compression stroke, since the high temperature burned gas was re-compressed, the temperature of ÃŽ ±H = 0.15 was also higher than that of ÃŽ ±H = 0.85. As a result, the temperature at the beginning of the second combustion stroke was high in ÃŽ ±H = 0.15 condition as compared with ÃŽ ±H = 0.85 condition. At the later stage of the second combustion, however, the opposite relationship between these two temperatures were observed, because the injection flow rate of the second combustion process was low in ÃŽ ±H = 0.15 condition. The maximum temperatures in the first and second combustion process decreased with an increase of the heat allocation ratio. Then, it could be concluded that the reduction of NO concentration with the heat allocation ratio, was caused by the decrease of the cylinder temperature. 3.4 Performance of the dual fuel six stroke diesel engine 3.4.1 Comparison with diesel fuel six stroke engine Operating conditions of comparison between the diesel fuel and the dual fuel six-stroke engines are shown in Table. 4. Experimental conditions were Xi I= 170 degrees (100 BTDC), Xi II = 530 degrees (10o BTDC) and ÃŽ ±H = 0.5. In dual fuel six-stroke engine, diesel fuel and methanol were supplied into first and second combustion process, independently. Combustion heats supplied per one cycle of the diesel fuel and dual fuel six-stroke engines were same. The combustion heat supplied per one cycle was selected as Qt = 0.43 KJ/cycle under the middle load condition. Performance of the dual fuel six-stroke engine was compared with the diesel fuel six-stroke engine under various injection timings in the second combustion process. Indicated torques of both engines was revealed constant around 15 N-m. As a result, it could be concluded that states of combustion of the diesel fuel and the dual fuel six-stroke engines had similar contributions on the engine performance. NO emissions from the dual fuel six-stroke engine were lower than those of the diesel fuel six-stroke engine. This effect appeared prominently at the advanced injection timing of the second combustion. Further, NO concentrations of both engines were reduced by the injection timing retard in the second combustion. [pic] Fig 16 Torque- Angle diagram for six stroke engine Soot emission in the exhaust gas of the diesel fuel six stroke engines increased with a retard of the injection timing in the second combustion. For the dual fuel six-stroke engine, the exhaust level of soot was very low under various injection timings of the second combustion process. Soot was formed clearly by the combustion of diesel fuel in the first combustion process and it was oxidized in the second combustion process. Considering these results, it was possible to estimate that soot was almost oxidized by methanol combustion in the second combustion process. This estimation is supported by a dual fuel diesel engine operated with diesel fuel methanol. The combustion heat supplied per one cycle was selected as Qt = 0.68 KJ/cycle under the high load condition. Indicated torques of both engines was also revealed constant around 20 N-m. NO concentration had the same tendency as the cases of the middle load. Soot emission level of the diesel fuel six-stroke engine was high in this high load condition. For the dual fuel six-stroke engine, however, soot was very low under various injection timings of the second combustion process. The performance of these engines was compared in Table. 4. For the second combustion process, since combustion heats of diesel fuel and methanol were different, injection quantities of both engines were different. BSFC and ISFC of the dual fuel six-stroke engine was sensibly higher than that of the diesel fuel engine. To compare the performance of these engines, injection quantity of both engines was defined by an amount of combustion heat, and SFC should be calculated from it. As a result, indicated specific heat consumption of the diesel fuel six-stroke engine was 5.59 MJ/KW-h, and that of the dual fuel six-stroke engine was 5.43 MJ/KW-h. For the high load conditions shown in Table. 5, the similar advantage of the dual fuel six-stroke engine was observed. Table 4. Detailed conditions of comparison between the diesel fuel and dual fuel diesel engines and performance of engines under ÃŽ ±H = 0.5 and middle load | |Diesel Fuel Six Stroke Diesel |Dual Fuel Six Stroke | | |Engine |Diesel Engine | |Engine Speed Ne [rpm] |2016 |2003 | |Supplied combustion heat per cycle | | | |Qt [KJ/cycle] |0.43 | | |Injection quantity per cycle |5.0 | | |(First Combustion Stroke) |(Diesel Fuel) | | |Mf1 [mg/cycle] | | | |Injection quantity per cycle |5.0 |10.7 | |(Second Combustion Stroke) |(Diesel Fuel) |(Methanol) | |Mf2 [mg/cycle] | | | |Excess air ratio ÃŽ » |2.98 |3.15 | |Brake torque Tb [N-m] |3.14 |3.14 | |Brake power Lb [KW] |0.66 |0.66 | |B.S.F.C. b [ g / KW-h] | 610.9 |952.9 | |I.M.E.P. Pi [Kgf / cm2] |3.43 |3.53 | |Indicated torque Ti [N-m] |16.70 |15.12 | |Indicated power Li [KW] |3.1 |2.77 | |I.S.F.C. bi [g / KW-h ] |130.1 |198.4 | |Indicated specific heat consumption | | | |bi’ [MJ /KW-h] |5.59 |5.43 | In order to confirm the advantage of dual fuel six-stroke engine, the performance of these engines was compared with four-stroke engine as shown in Table. 6. NO concentrations of the diesel fuel and the dual fuel six-stroke engines were improved with 85 90% as compared with that of the four-stroke engine. Soot emission of the diesel fuel six-stroke engine was much higher than that of the four-stroke engine. However, for the dual fuel six-stroke engine, soot level was very low. Furthermore, the indicated specific heat consumption of the diesel fuel and dual fuel six-stroke engine were lower than that of the four-stroke engine. Especially, for the dual fuel six-stroke engine, the indicated specific heat consumption was improved with 15% as compared with that of the four stroke engine. From these results, it could be confirmed that the dual fuel six-stroke engine was superior to the diesel fuel six-stroke engine, and also it was superior to the four-stroke engine. Table 6. Percentage improvements of exhaust emission and specific heat consumption | |Four Stroke Diesel | Six Stroke Diesel Engine|Dual Fuel Six Stroke Engine | | |Engine | | | |NO [ppm] | |113 |90.5 | |( % improvement) |768 |(85.3%) |(88.2%) | |Soot [%] | |28.8 |0 | |(%improvement) |6.8 |(- 323.5%) |(100%) | |Indicated specific heat consumption bi’ | | | | |[MJ/KW-h] |7.51 |6.61 |6.37 | |(% improvement) | |(12.0%) |(15.2%) | Table 5. Detailed conditions of comparison between the diesel fuel and dual fuel diesel engine and performance of engines under ÃŽ ±H =0.5 and high load | | Six Stroke Diesel Engine |Dual Fuel Six Stroke Engine | |Engine Speed Ne [rpm] |2016 |2006 | |Supplied combustion heat per cycle | | | |Qt [kJ/cycle] |0.68 | | |Injection quantity per cycle |8.0 | | |(First Combustion Stroke) |(Diesel Fuel) | | |Mf1 [mg/cycle] | | | |Injection quantity per cycle |8.0 |17.2 | |(Second Combustion Stroke) |(Diesel Fuel) |(Methanol) | |Mf2 [mg/cycle] | | | |Excess air ratio ÃŽ » |1.86 |1.93 | |Brake torque Tb [N-m] |6.18 |6.08 | |Brake power Lb [kW] |1.52 |1.5 | |B.S.F.C. b [ g / kW.h] | 504.0 |777.7 | |I.M.E.P. Pi [kgf / cm2] |4.56 |4.75 | |Indicated torque Ti [N-m] |21.68 |20.38 | |Indicated power Li [kW] |3.45 |2.98 | |I.S.F.C. bi [g / kW.h ] |155.5 |236.2 | |Indicated specific heat consumption | | | |bi’ [MJ /kW.h] |6.61 |6.37 | 3.4.2 Effect of injection timing Performance of the dual fuel six-stroke engine under various injection timings in the second combustion process was investigated on middle and high load. Experimental conditions were Xi I = 170 degrees (100 BTDC) and ÃŽ ±H = 0.5. Performance of the dual fuel six-stroke engine under both load conditions had the similar tendency with the timing retard. NO concentrations in the high load condition were higher than those of the middle load condition. However, soot emission levels of both load conditions were extremely low under various injection timings of the second combustion. 3.4.3 Effect of heat allocation ratio Performance of the dual fuel six-stroke engine under various heat allocation ratios was investigated on middle and high load. Injection conditions were Xi I = 170 degrees (100 BTDC) and Xi II = 530 degrees (100 BTDC). Since the combustion heat of methanol was low, experimental range of heat allocation ratio was limited by the smooth operation of the engine. Only the range from ÃŽ ±H = 0.25 to 0.75 (on Qt = 0.43 KJ/cycle), and from ÃŽ ±H = 0 to 0.5 (on Qt = 0.68 KJ/cycle) could be tested.. Indicated torque increased with an increase of the heat allocation ratio. NO concentration in exhaust gas was reduced with an increase of the heat allocation ratio. Soot was very low, irrespective of the methanol flow rate. Even if the load condition was high, it was concluded that soot was practically eliminated by a small amount of methanol in the second combustion process (8% of total fuel). 4. ADVANTAGES OF SIX STROKE OVER FOUR STROKE ENGINES The six stroke is thermodynamically more efficient because the change in volume of the power stroke is greater than the intake stroke, the compression stroke and the Six stroke engine is fundamentally superior to the four stroke because the head is no longer parasitic but is a net contributor to – and an integral part of – the power generation within exhaust stroke. The compression ration can be increased because of the absent of hot spots and the rate of change in volume during the critical combustion period is less than in a Four stroke. The absence of valves within the combustion chamber allows considerable design freedom. 4.1 Main advantages of the duel fuel six-stroke engine: 4.1.1 Reduction in fuel consumption by at least 40%: An operating efficiency of approximately 50%, hence the large reduction in specific consumption. the Operating efficiency of current petrol engine is of the order of 30%. The specific power of the six-stroke engine will not be less than that of a four-stroke petrol engine, the increase in thermal efficiency compensating for the issue due to the two additional strokes. 4.1.2 Two expansions (work) in six strokes: Since the work cycles occur on two strokes (3600 out of 10800 ) or 8% more than in a four-stroke engine (1800 out of 720 ), the torque is much more even. This lead to very smooth operation at low speed without any significant effects on consumption and the emission of pollutants, the combustion not being affected by the engine speed. These advantages are very important in improving the performance of car in town traffic. 4.1.2 Dramatic reduction in pollution: Chemical, noise and thermal pollution are reduced, on the one hand, in proportion to the reduction in specific consumption, and on the other, through the engine’s own characteristics which will help to considerably lower HC, CO and NOx emissions. Furthermore, it’s ability to run with fuels of vegetable origin and weakly pollutant gases under optimum conditions, gives it qualities which will allow it to match up to the strictest standards. 4.1.3 Multifuel: Multifuel par excellence, it can use the most varied fuels, of any origin (fossil or vegetable), from diesel to L.P.G. or animal grease. The difference in inflammability or antiknock rating does not present any problem in combustion. It’s light, standard petrol engine construction, and the low compression ration of the combustion chamber; do not exclude the use of diesel fuel. Methanol-petrol mixture is also recommended. 5. CONCLUSIONS The performance of the dual fuel six-stroke engine was investigated. In this dual fuel engine, diesel fuel was supplied into the first combustion process and methanol was supplied into the second combustion process where  the burned gas in the first combustion process was re-compressed. The results are summarized as follows. 1. Indicated specific fuel consumption (ISFC.) of the six-stroke engine proposed here is slightly lower than that of the four-stroke engine (about 9% improvement). NO and soot emissions from the six-stroke engine was improved as compared with four-stroke engine under advanced injection timings in the second combustion stroke. 2. For the dual fuel six-stroke engine, the timing retard and an increase of heat allocation ratio in the second combustion stroke resulted in a decrease of the maximum temperatures in the combustion processes. It caused the reduction of NO emission. 3. For the dual fuel six-stroke engine, soot was practically eliminated by a small amount of methanol in the second combustion process. 4. From the comparison of the performance between the dual fuel six-stroke and the four-stroke engine, it was concluded that indicated specific heat consumption of the dual fuel six-stroke engine was improved with 15% as compared with the four-stroke engine. NO concentration of the dual fuel six-stroke engine was improved with 90%. Furthermore, soot emission was very low in the dual fuel six-stroke engine. 5. As the fuel in one cycle was divided into two combustion processes and the EGR effect appeared in the second combustion process, the decreased maximum cylinder temperature reduced NO concentration in the exhaust gas It was further confirmed that soot formed in the first combustion process was oxidized in the second combustion process .Therefore, a six stroke DI diesel engine has significant possibilities to improve combustion process because of its more controllable factors relative to a conventional four-stroke engine. Considering these results, it was confirmed that the dual fuel six-stroke engine was superior to the four-stroke engine. 6. REFERENCES 1. Tsunaki Hayasaki, Yuichirou Okamoto, Kenji Amagai and Masataka Arai â€Å"A Six-stroke DI Diesel Engine under Dual Fuel Operation â€Å"SAE Paper No 1999-01-1500 2. S.Goto and K.Kontani, A Dual Fuel Injector for Diesel Engines, SAE paper, No. 851584, 1985 3. â€Å"Internal Combustion Engines â€Å"A book by Mathur Sharma. 4. â€Å"Internal Combustion Engines† Tata McGraw-hill publications, Author V Ganesan 7. NOMENCLATURE Ne : Engine speed X : Crank angle Xi : Injection timing of the four-stroke diesel engine ÃŽ ±H : Heat allocation ratio Q : Supplied combustion heat Qt : Supplied combustion heat per cycle P : Cylinder pressure V : Cylinder volume Vs : Stroke volume Pi : Indicated mean effective pressure (LM.E.P) Ti : Indicated torque Li : Indicated power Tb : Brake torque Lb : Brake power Ht : Supplied combustion heat per unit time Ma : Intake air flow per cycle Ma : Intake air flow per unit time Mf : Injection quantity per cycle Mi : Injection quantity per unit time ÃŽ » : Excess air ratio b : Brake specific fuel consumption (B.S.F.C.) bl : Indicated specific fuel consumption (I.S.F.C.) bi : Indicated specific heat consumption SUBSCRIPTS I: first combustion stroke II: second combustion stroke 4: four-stroke diesel engine 6: six-stroke diesel engine