Distance education created new challenges regarding the delivery of large size isochronous continuous streaming media (SM) objects. In this paper, we consider the design of a framework for customized SM presentations, where each presentation consists of a number of SM objects that should be retrieved and displayed to the user in a coherent fashion. We describe a retrieval optimizer (Prime) that captures the flexibilities and requirements imposed by the user query, user profile, and session profile. Then, it determines how this query script should be imposed against the continuous media (CM) server to reduce contention. We also provide a cost model to evaluate each proposed plan. Finally, we explain the role of memory buffering in alleviating the server bandwidth fragmentation problem. Our preliminary experimental results show the feasibility and effectiveness of our proposed model and techniques in generating near optimal retrieval.
{"title":"Streaming of Continuous Media for Distance Education Systems","authors":"A. Dashti, Maytham Safar","doi":"10.4018/jdet.2007070104","DOIUrl":"https://doi.org/10.4018/jdet.2007070104","url":null,"abstract":"Distance education created new challenges regarding the delivery of large size isochronous continuous streaming media (SM) objects. In this paper, we consider the design of a framework for customized SM presentations, where each presentation consists of a number of SM objects that should be retrieved and displayed to the user in a coherent fashion. We describe a retrieval optimizer (Prime) that captures the flexibilities and requirements imposed by the user query, user profile, and session profile. Then, it determines how this query script should be imposed against the continuous media (CM) server to reduce contention. We also provide a cost model to evaluate each proposed plan. Finally, we explain the role of memory buffering in alleviating the server bandwidth fragmentation problem. Our preliminary experimental results show the feasibility and effectiveness of our proposed model and techniques in generating near optimal retrieval.","PeriodicalId":44463,"journal":{"name":"International Journal of Distance Education Technologies","volume":"14 1","pages":"190-216"},"PeriodicalIF":3.3,"publicationDate":"2007-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89186129","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Computer aided assessment is a common approach used by educational institutions. The benefits range into the design of teaching, learning and instructional materials. While some such systems implement fully automated marking for multiple choice questions and fill-in-the-blanks they are insufficient when human critiquing is required. Current systems developed in isolation have little regard to scalability and interoperability between courses, computer platforms and Learning Management Systems. The IMS Global Learning Consortium’s open specifications for interoperable learning technology lack functionality to make it useful for Computer Assisted Marking. This paper presents an enhanced set of these standards to address the issue.
{"title":"Enhancing the IMS QTI to Better Support Computer Assisted Marking","authors":"D. Clark, Penny Baillie de Byl","doi":"10.4018/jdet.2007070102","DOIUrl":"https://doi.org/10.4018/jdet.2007070102","url":null,"abstract":"Computer aided assessment is a common approach used by educational institutions. The benefits range into the design of teaching, learning and instructional materials. While some such systems implement fully automated marking for multiple choice questions and fill-in-the-blanks they are insufficient when human critiquing is required. Current systems developed in isolation have little regard to scalability and interoperability between courses, computer platforms and Learning Management Systems. The IMS Global Learning Consortium’s open specifications for interoperable learning technology lack functionality to make it useful for Computer Assisted Marking. This paper presents an enhanced set of these standards to address the issue.","PeriodicalId":44463,"journal":{"name":"International Journal of Distance Education Technologies","volume":"56 1","pages":"174-189"},"PeriodicalIF":3.3,"publicationDate":"2007-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78425294","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The sharable content object reference model (SCORM) includes a representation of distance learning contents and a behavior definition of how users should interact with the contents. Generally, SCORMcompliant systems were based on multimedia and Web technologies on PCs. We further build a pervasive learning environment, which allows users to read SCORM-compliant textbooks with multimodal learning devices. Respecting the learning contents for supporting such learning environment, an efficient authoring tool was developed for serving this goal. Some specific tags were defined to specify the corresponding information or interactions that cannot be performed in the hardcopy books. These tags can be printed in SCORM-compliant textbooks and recognized by Hyper Pen to facilitate the affinity between the physical textbooks and digital world. Therefore, users can read the SCORM-compliant hardcopy textbooks in a traditional manner. The authored course contents will be the same while applying to the multimodal learning devices with different layouts.
{"title":"A SCORM Compliant Courseware Authoring Tool for Supporting Pervasive Learning","authors":"Te-Hua Wang, Flora Chia-I Chang","doi":"10.4018/jdet.2007070105","DOIUrl":"https://doi.org/10.4018/jdet.2007070105","url":null,"abstract":"The sharable content object reference model (SCORM) includes a representation of distance learning contents and a behavior definition of how users should interact with the contents. Generally, SCORMcompliant systems were based on multimedia and Web technologies on PCs. We further build a pervasive learning environment, which allows users to read SCORM-compliant textbooks with multimodal learning devices. Respecting the learning contents for supporting such learning environment, an efficient authoring tool was developed for serving this goal. Some specific tags were defined to specify the corresponding information or interactions that cannot be performed in the hardcopy books. These tags can be printed in SCORM-compliant textbooks and recognized by Hyper Pen to facilitate the affinity between the physical textbooks and digital world. Therefore, users can read the SCORM-compliant hardcopy textbooks in a traditional manner. The authored course contents will be the same while applying to the multimodal learning devices with different layouts.","PeriodicalId":44463,"journal":{"name":"International Journal of Distance Education Technologies","volume":"10 1","pages":"40-62"},"PeriodicalIF":3.3,"publicationDate":"2007-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89803954","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Frederick W. B. Li, Rynson W. H. Lau, T. Komura, M. Wang, B. Siu
Human motion animation has been one of the major research topics in the field of computer graphics for decades. Techniques developed in this area help present human motions in various applications. This is crucial for enhancing the realism as well as promoting the user interest in the applications. To carry this merit to e-learning applications, we have developed efficient techniques for delivering human motion information over the Internet to collaborating e-learning users and revealing the motion information in the client machines with different rendering capability. Our method offers a mechanism to extract human motion data at various levels of detail (LoD). We also propose a set of importance factors to allow an e-learning system to determine the LoD of the human motion for rendering as well as transmission, according to the importance of the motion and the available network bandwidth. At the end of the paper, we demonstrate the effectiveness of the new method with some experimental results.
{"title":"Adaptive Animation of Human Motion for E-Learning Applications","authors":"Frederick W. B. Li, Rynson W. H. Lau, T. Komura, M. Wang, B. Siu","doi":"10.4018/jdet.2007040106","DOIUrl":"https://doi.org/10.4018/jdet.2007040106","url":null,"abstract":"Human motion animation has been one of the major research topics in the field of computer graphics for decades. Techniques developed in this area help present human motions in various applications. This is crucial for enhancing the realism as well as promoting the user interest in the applications. To carry this merit to e-learning applications, we have developed efficient techniques for delivering human motion information over the Internet to collaborating e-learning users and revealing the motion information in the client machines with different rendering capability. Our method offers a mechanism to extract human motion data at various levels of detail (LoD). We also propose a set of importance factors to allow an e-learning system to determine the LoD of the human motion for rendering as well as transmission, according to the importance of the motion and the available network bandwidth. At the end of the paper, we demonstrate the effectiveness of the new method with some experimental results.","PeriodicalId":44463,"journal":{"name":"International Journal of Distance Education Technologies","volume":"130 1","pages":"134-144"},"PeriodicalIF":3.3,"publicationDate":"2007-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81340233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dan B. Phung, G. Valetto, G. Kaiser, Tiecheng Liu, J. Kender
The increasing popularity of online courses has highlighted the need for collaborative learning tools for student groups. In addition, the introduction of lecture videos into the online curriculum has drawn attention to the disparity in the network resources available to students. We present an e-Learning architecture and adaptation model called AITV (Adaptive Interactive Internet Team Video), which allows groups of students to collaboratively view a video in synchrony. AITV upholds the invariant that each student will view semantically equivalent content at all times. A semantic compression model is developed to provide instructional videos at different level-of-details to accommodate dynamic network conditions and users’ system requirements. We take advantage of the semantic compression algorithm’s ability to provide different layers of semantically equivalent video by adapting the client to play at the appropriate layer that provides the client with the richest possible viewing experience. Video player actions, like play, pause and stop, can be initiated by any group member and and the results of those actions are synchronized with all the other students. These features allow students to review a lecture video in tandem, facilitating the learning process. Experimental trials show that AITV successfully synchronizes instructional videos for distributed students while concurrently optimizing the video quality, even under conditions of fluctuating bandwidth, by adaptively adjusting the quality level for each student while still maintaining the invariant.
{"title":"Adaptive Synchronization of Semantically Compressed Instructional Videos for Collaborative Distance Learning","authors":"Dan B. Phung, G. Valetto, G. Kaiser, Tiecheng Liu, J. Kender","doi":"10.4018/jdet.2007040105","DOIUrl":"https://doi.org/10.4018/jdet.2007040105","url":null,"abstract":"The increasing popularity of online courses has highlighted the need for collaborative learning tools for student groups. In addition, the introduction of lecture videos into the online curriculum has drawn attention to the disparity in the network resources available to students. We present an e-Learning architecture and adaptation model called AITV (Adaptive Interactive Internet Team Video), which allows groups of students to collaboratively view a video in synchrony. AITV upholds the invariant that each student will view semantically equivalent content at all times. A semantic compression model is developed to provide instructional videos at different level-of-details to accommodate dynamic network conditions and users’ system requirements. We take advantage of the semantic compression algorithm’s ability to provide different layers of semantically equivalent video by adapting the client to play at the appropriate layer that provides the client with the richest possible viewing experience. Video player actions, like play, pause and stop, can be initiated by any group member and and the results of those actions are synchronized with all the other students. These features allow students to review a lecture video in tandem, facilitating the learning process. Experimental trials show that AITV successfully synchronizes instructional videos for distributed students while concurrently optimizing the video quality, even under conditions of fluctuating bandwidth, by adaptively adjusting the quality level for each student while still maintaining the invariant.","PeriodicalId":44463,"journal":{"name":"International Journal of Distance Education Technologies","volume":"81 1","pages":"72-86"},"PeriodicalIF":3.3,"publicationDate":"2007-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77343147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
W. K. Cheung, A. Mørch, K. Wong, Cynthia Lee, Jiming Liu, Mason H. Lam
In this paper we investigate the use of Latent Semantic Analysis (LSA), Critiquing Systems, and Knowledge Building to support computer-based teaching of English composition. We have built and tested an English Composition Critiquing System that makes use of LSA to analyze student essays and compute feedback by comparing their essays with teacher’s model essays. LSA values are input to a critiquing component to provide a user interface for the students. A software agent can also use the critic feedback to coordinate a collaborative knowledge building session with multiple users (students and teachers). Shared feedback provides seed questions that can trigger discussion and extended reflection about the next phase of writing. We present the first version of a prototype we have built, and report the results from three experiments. We end the paper by describing our plans for future work.
{"title":"Grounding Collaborative Learning in Semantics-Based Critiquing","authors":"W. K. Cheung, A. Mørch, K. Wong, Cynthia Lee, Jiming Liu, Mason H. Lam","doi":"10.4018/JDET.2007040104","DOIUrl":"https://doi.org/10.4018/JDET.2007040104","url":null,"abstract":"In this paper we investigate the use of Latent Semantic Analysis (LSA), Critiquing Systems, and Knowledge Building to support computer-based teaching of English composition. We have built and tested an English Composition Critiquing System that makes use of LSA to analyze student essays and compute feedback by comparing their essays with teacher’s model essays. LSA values are input to a critiquing component to provide a user interface for the students. A software agent can also use the critic feedback to coordinate a collaborative knowledge building session with multiple users (students and teachers). Shared feedback provides seed questions that can trigger discussion and extended reflection about the next phase of writing. We present the first version of a prototype we have built, and report the results from three experiments. We end the paper by describing our plans for future work.","PeriodicalId":44463,"journal":{"name":"International Journal of Distance Education Technologies","volume":"14 1","pages":"106-119"},"PeriodicalIF":3.3,"publicationDate":"2007-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90316186","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Iwatsuki, Norio Takeuchi, Hisato Kobayashi, K. Yana, H. Takeda, Hisashi Yaginuma, Hajime Kiyohara, Akira Tokuyasu
This article describes a new automatic digital content generation system we have developed. Recently some universities, including Hosei University, have been offering students opportunities to take distance interactive classes over the Internet from overseas. When such distance lectures are delivered in English to Japanese students, there is a pressing need to provide materials for review after class, such as video content on a CD-ROM or on a Web site. To meet this need, we have developed a new automatic content generation system, which enables the complete archiving of lectures including video/audio content, synchronized presentation materials, and handwritten traces on virtual whiteboards. The content is generated in real time and is immediately available at the end of the class. In addition, this system incorporates a unique video search algorithm which adopts a phonetic-based search technology. This enables quick review of the video content by typed-in keywords. The system can automatically create a vast amount of digital content and provide students with an efficient learning tool.
{"title":"Automatic Digital Content Generation System for Real-Time Distance Lectures","authors":"M. Iwatsuki, Norio Takeuchi, Hisato Kobayashi, K. Yana, H. Takeda, Hisashi Yaginuma, Hajime Kiyohara, Akira Tokuyasu","doi":"10.4018/jdet.2007010102","DOIUrl":"https://doi.org/10.4018/jdet.2007010102","url":null,"abstract":"This article describes a new automatic digital content generation system we have developed. Recently some universities, including Hosei University, have been offering students opportunities to take distance interactive classes over the Internet from overseas. When such distance lectures are delivered in English to Japanese students, there is a pressing need to provide materials for review after class, such as video content on a CD-ROM or on a Web site. To meet this need, we have developed a new automatic content generation system, which enables the complete archiving of lectures including video/audio content, synchronized presentation materials, and handwritten traces on virtual whiteboards. The content is generated in real time and is immediately available at the end of the class. In addition, this system incorporates a unique video search algorithm which adopts a phonetic-based search technology. This enables quick review of the video content by typed-in keywords. The system can automatically create a vast amount of digital content and provide students with an efficient learning tool.","PeriodicalId":44463,"journal":{"name":"International Journal of Distance Education Technologies","volume":"10 1","pages":"1-8"},"PeriodicalIF":3.3,"publicationDate":"2007-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77892220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Judy C. R. Tseng, W. Tsai, Gwo-jen Hwang, Po-Han Wu
In developing traditional learning materials, quality is the key issue to be considered. However, for high technical e-training courses, not only the quality of the learning materials but also the efficiency of developing the courses needs to be taken into consideration. It is a challenging issue for experienced engineers to develop up-to-date e-training courses for inexperienced engineers before further new technologies are proposed. To cope with these problems, a concept relationship-oriented approach is proposed in this paper. A system for developing e-training courses has been implemented based on the novel approach. Experimental results showed that the novel approach can significantly shorten the time needed for developing e-training courses, such that engineers can receive up-to-date technologies in time.
{"title":"An Efficient and Effective Approach to Developing Engineering E-Training Courses","authors":"Judy C. R. Tseng, W. Tsai, Gwo-jen Hwang, Po-Han Wu","doi":"10.4018/jdet.2007010104","DOIUrl":"https://doi.org/10.4018/jdet.2007010104","url":null,"abstract":"In developing traditional learning materials, quality is the key issue to be considered. However, for high technical e-training courses, not only the quality of the learning materials but also the efficiency of developing the courses needs to be taken into consideration. It is a challenging issue for experienced engineers to develop up-to-date e-training courses for inexperienced engineers before further new technologies are proposed. To cope with these problems, a concept relationship-oriented approach is proposed in this paper. A system for developing e-training courses has been implemented based on the novel approach. Experimental results showed that the novel approach can significantly shorten the time needed for developing e-training courses, such that engineers can receive up-to-date technologies in time.","PeriodicalId":44463,"journal":{"name":"International Journal of Distance Education Technologies","volume":"1 1","pages":"26-39"},"PeriodicalIF":3.3,"publicationDate":"2007-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74405165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Traditionally, in teaching handwriting, the teacher writes a character on the blackboard, and then students try to follow the teacher in order to write the same character. The teacher can check whether a student’s handwriting is spatially correct by looking at its shape but he/she is not able to verify if the student is writing in the correct stroke order with the correct number of strokes. As a result, we design a web-based handwriting education system. With our proposed system, students can stay at home to do the exercises for learning the handwriting of characters. A student’s handwriting can be captured in digital format with the information in both temporal and spatial domain and the results can be sent to the teacher for evaluation. In addition, we propose to animate a virtual teacher on the student’s terminal for demonstrating the handwriting of the characters to give students a sense of presence.
{"title":"Web-Based Handwriting Education with Animated Virtual Teacher","authors":"Howard Leung, T. Komura","doi":"10.4018/jdet.2006010106","DOIUrl":"https://doi.org/10.4018/jdet.2006010106","url":null,"abstract":"Traditionally, in teaching handwriting, the teacher writes a character on the blackboard, and then students try to follow the teacher in order to write the same character. The teacher can check whether a student’s handwriting is spatially correct by looking at its shape but he/she is not able to verify if the student is writing in the correct stroke order with the correct number of strokes. As a result, we design a web-based handwriting education system. With our proposed system, students can stay at home to do the exercises for learning the handwriting of characters. A student’s handwriting can be captured in digital format with the information in both temporal and spatial domain and the results can be sent to the teacher for evaluation. In addition, we propose to animate a virtual teacher on the student’s terminal for demonstrating the handwriting of the characters to give students a sense of presence.","PeriodicalId":44463,"journal":{"name":"International Journal of Distance Education Technologies","volume":"196 1","pages":"293-300"},"PeriodicalIF":3.3,"publicationDate":"2004-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77421388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Instead of web-based course development using an off-the-shelf web authoring tool, we believe that a better way to show principles and techniques in computer science is to have the related algorithms running "live" in background and to allow students interact with them within a web browser. We have chosen computer graphics as an example course because of its demand for visualization and its challenge for 3D rendering. This paper presents the visualization techniques and a set of web-based demos designed to demonstrate the computer graphics concepts and OpenGL functions. We have ported the popular Nate Robins' OpenGL demos on the web and have also developed our own demos. The main idea of the approach is to put a real world scene and a rendering result side by side together with a set of corresponding OpenGL functions to produce the rendering result from the real-world scene. Animation, user interaction, manipulation, and virtual navigation are supported in the sense that functions and the parameters of each function can be changed interactively and such changes will be reflected immediately in the rendering result. The demos are written by using Java and GL4Java, an OpenGL Java binding to ensure the deployment on the Web. The result is a set of interactive web-based tutorials with rich visualization driven by underlying algorithms to demonstrate the subject principles and techniques. Although the contents of the demos are specific to computer graphics, the presented methodology represents a generic approach which is discipline/course independent and can be applied to various other computer science courses.
{"title":"Web-Based Interactive 3D Visualization for Computer Graphics Education","authors":"Li Yang, M. Sanver","doi":"10.4018/jdet.2003070106","DOIUrl":"https://doi.org/10.4018/jdet.2003070106","url":null,"abstract":"Instead of web-based course development using an off-the-shelf web authoring tool, we believe that a better way to show principles and techniques in computer science is to have the related algorithms running \"live\" in background and to allow students interact with them within a web browser. We have chosen computer graphics as an example course because of its demand for visualization and its challenge for 3D rendering. This paper presents the visualization techniques and a set of web-based demos designed to demonstrate the computer graphics concepts and OpenGL functions. We have ported the popular Nate Robins' OpenGL demos on the web and have also developed our own demos. The main idea of the approach is to put a real world scene and a rendering result side by side together with a set of corresponding OpenGL functions to produce the rendering result from the real-world scene. Animation, user interaction, manipulation, and virtual navigation are supported in the sense that functions and the parameters of each function can be changed interactively and such changes will be reflected immediately in the rendering result. The demos are written by using Java and GL4Java, an OpenGL Java binding to ensure the deployment on the Web. The result is a set of interactive web-based tutorials with rich visualization driven by underlying algorithms to demonstrate the subject principles and techniques. Although the contents of the demos are specific to computer graphics, the presented methodology represents a generic approach which is discipline/course independent and can be applied to various other computer science courses.","PeriodicalId":44463,"journal":{"name":"International Journal of Distance Education Technologies","volume":"22 1","pages":"423-432"},"PeriodicalIF":3.3,"publicationDate":"2002-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87918188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：