One of the challenges for 3D multi-user virtual simulation environments (3D MUVEs) developers is to keep the shared virtual simulation environment synchronized among all the participating users´ terminals. Support to 3DMUVEs through traditional client-server communication model offers simpler management but can lead to bottlenecks and higher latencies. Peer-to-peer communication model, on the other hand, offers no central coordination but are more complex to manage. Current peer-to-peer networks, such as KaZaA and Gnutella, provide multimedia sharing services but do not support multiuser 3D virtual environment applications. This paper describes a solution to support 3D MUVEs in a hybrid peer-to-peer Gnutella network, which provides session control and distributed shared virtual environment synchronization. As a result of this work, two components specified by the ongoing multi-user extension to the MPEG-4 standard were implemented and integrated to the Gnutella network for control and synchonization. This solution minimizes the disadvantages of client-server, pure peer-to-peer and proxy-based models. The results show the number of users per session that can be supported with acceptable delays for tasks such as collaborative editing and for highly interactive applications such as action games.
{"title":"A Hybrid Solution to Support Multiuser 3D Virtual Simulation Environments in Peer-to-Peer Networks","authors":"A. Boukerche, R. B. Araujo, Marcelo Laffranchi","doi":"10.1109/DS-RT.2004.2","DOIUrl":"https://doi.org/10.1109/DS-RT.2004.2","url":null,"abstract":"One of the challenges for 3D multi-user virtual simulation environments (3D MUVEs) developers is to keep the shared virtual simulation environment synchronized among all the participating users´ terminals. Support to 3DMUVEs through traditional client-server communication model offers simpler management but can lead to bottlenecks and higher latencies. Peer-to-peer communication model, on the other hand, offers no central coordination but are more complex to manage. Current peer-to-peer networks, such as KaZaA and Gnutella, provide multimedia sharing services but do not support multiuser 3D virtual environment applications. This paper describes a solution to support 3D MUVEs in a hybrid peer-to-peer Gnutella network, which provides session control and distributed shared virtual environment synchronization. As a result of this work, two components specified by the ongoing multi-user extension to the MPEG-4 standard were implemented and integrated to the Gnutella network for control and synchonization. This solution minimizes the disadvantages of client-server, pure peer-to-peer and proxy-based models. The results show the number of users per session that can be supported with acceptable delays for tasks such as collaborative editing and for highly interactive applications such as action games.","PeriodicalId":355772,"journal":{"name":"Eighth IEEE International Symposium on Distributed Simulation and Real-Time Applications","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122711971","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}
This paper focuses on the performance monitoring of a networked virtual environment, called EVE, in order to identify the elements that degrade its network performance. In particular, based both on the architectural and communication model that EVE adopts in order to cope with the dynamic behavior of the network, we performed a series of experiments, taking into account the number of the connected users, the network load as well as the connection type of the users.
{"title":"Monitoring and Analyzing Performance of Networked Virtual Environments: The Case of EVE","authors":"C. Bouras, E. Giannaka","doi":"10.1109/DS-RT.2004.30","DOIUrl":"https://doi.org/10.1109/DS-RT.2004.30","url":null,"abstract":"This paper focuses on the performance monitoring of a networked virtual environment, called EVE, in order to identify the elements that degrade its network performance. In particular, based both on the architectural and communication model that EVE adopts in order to cope with the dynamic behavior of the network, we performed a series of experiments, taking into account the number of the connected users, the network load as well as the connection type of the users.","PeriodicalId":355772,"journal":{"name":"Eighth IEEE International Symposium on Distributed Simulation and Real-Time Applications","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125095524","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}
Fábio Reis Cecin, R. Real, R. D. O. Jannone, C. Geyer, M. G. Martins, J. Barbosa
State-of-the-art Massively Multiplayer Games such as EverQuest and Ultima Online are currently implemented as client-server systems. Although this approach allows the development of commercially viable MMG services, the costs associated with running a scalable client-server MMG service are often too high for small companies or research projects. This paper proposes FreeMMG, a mixed peer-to-peer and client-server approach to the distribution aspect ofMMGs. It is argued that the FreeMMG model supports scalable, cheat-resistant, massively multiplayer realtime strategy (RTS) games using a lightweight server that delegates the bulk of the game simulation to the clients. A working prototype game called FreeMMG Wizards is presented, together with some preliminary scalability test results featuring up to 300 simulated game clients connected to a FreeMMG server. The results show that the measured server traffic can be considered very low if compared with more centralized alternatives.
{"title":"FreeMMG: A Scalable and Cheat-Resistant Distribution Model for Internet Games","authors":"Fábio Reis Cecin, R. Real, R. D. O. Jannone, C. Geyer, M. G. Martins, J. Barbosa","doi":"10.1109/DS-RT.2004.21","DOIUrl":"https://doi.org/10.1109/DS-RT.2004.21","url":null,"abstract":"State-of-the-art Massively Multiplayer Games such as EverQuest and Ultima Online are currently implemented as client-server systems. Although this approach allows the development of commercially viable MMG services, the costs associated with running a scalable client-server MMG service are often too high for small companies or research projects. This paper proposes FreeMMG, a mixed peer-to-peer and client-server approach to the distribution aspect ofMMGs. It is argued that the FreeMMG model supports scalable, cheat-resistant, massively multiplayer realtime strategy (RTS) games using a lightweight server that delegates the bulk of the game simulation to the clients. A working prototype game called FreeMMG Wizards is presented, together with some preliminary scalability test results featuring up to 300 simulated game clients connected to a FreeMMG server. The results show that the measured server traffic can be considered very low if compared with more centralized alternatives.","PeriodicalId":355772,"journal":{"name":"Eighth IEEE International Symposium on Distributed Simulation and Real-Time Applications","volume":"32 10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125734856","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}
Successful development of large-scale complex and distributed real-time systems commonly relies on models developed separately for simulation studies and software implementation. Systems theory provides sound modeling principles to characterize structural and behavioral aspects of systems across time and space. The behavior of these models can be observed using simulation protocols that can correctly interpret time-based logical dynamics. Similarly, object-orientation theories and software architecture principles enable modeling static and dynamic behavior of systems. While models described either in system-theoretic or object-orientated languages may be used for both software design and simulation modeling, each has its own strengths and weaknesses. For example, a class of system-theoretic modeling approach called Discrete-event System Specification (DEVS) provides an appropriate basis to develop simulation models exhibiting concurrent and distributed behavior. Similarly, the Unified Modeling Language with real-time (UML-RT) constructs can be used to develop software design models that can be implemented and executed. Since software models are not suitable to be used as simulation models and simulation models may not adequately lend themselves to serve as software design blueprints, it is important to examine these approaches. We show some of the key shortcomings of these simulation and software design modeling approaches by developing some detailed specifications and implementation of a coffee machine with a focus on their treatment of logical and physical time.
{"title":"Software and Simulation Modeling for Real-Time Software-Intensive Systems","authors":"Dongping Huang, H. Sarjoughian","doi":"10.1109/DS-RT.2004.37","DOIUrl":"https://doi.org/10.1109/DS-RT.2004.37","url":null,"abstract":"Successful development of large-scale complex and distributed real-time systems commonly relies on models developed separately for simulation studies and software implementation. Systems theory provides sound modeling principles to characterize structural and behavioral aspects of systems across time and space. The behavior of these models can be observed using simulation protocols that can correctly interpret time-based logical dynamics. Similarly, object-orientation theories and software architecture principles enable modeling static and dynamic behavior of systems. While models described either in system-theoretic or object-orientated languages may be used for both software design and simulation modeling, each has its own strengths and weaknesses. For example, a class of system-theoretic modeling approach called Discrete-event System Specification (DEVS) provides an appropriate basis to develop simulation models exhibiting concurrent and distributed behavior. Similarly, the Unified Modeling Language with real-time (UML-RT) constructs can be used to develop software design models that can be implemented and executed. Since software models are not suitable to be used as simulation models and simulation models may not adequately lend themselves to serve as software design blueprints, it is important to examine these approaches. We show some of the key shortcomings of these simulation and software design modeling approaches by developing some detailed specifications and implementation of a coffee machine with a focus on their treatment of logical and physical time.","PeriodicalId":355772,"journal":{"name":"Eighth IEEE International Symposium on Distributed Simulation and Real-Time Applications","volume":"290 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116402712","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}
Running a large-scale HLA-based simulation in a distributed environment may require large amounts of computing resources at geographically different locations. A simulation running for a long period of time may result in imbalance of load levels at different computing hosts, hence leading to degradation of performance. Performance typically improves if the workload can be equally distributed among the different computing hosts. However, the Run Time Infrastructure (RTI) does not have any facilities to perform load distribution to alleviate this problem. This paper describes an architecture that provides load distribution services over a multi-threaded RTI to improve the performance of HLA simulations. A new metric for measuring the workload for both optimistic and conservative simulation federates is proposed. Load distribution is achieved through federate migration by introducing mobility and reactivity to each simulation federate.
{"title":"Load Distribution Services in HLA","authors":"Gary S. H. Tan, K. C. Lim","doi":"10.1109/DS-RT.2004.27","DOIUrl":"https://doi.org/10.1109/DS-RT.2004.27","url":null,"abstract":"Running a large-scale HLA-based simulation in a distributed environment may require large amounts of computing resources at geographically different locations. A simulation running for a long period of time may result in imbalance of load levels at different computing hosts, hence leading to degradation of performance. Performance typically improves if the workload can be equally distributed among the different computing hosts. However, the Run Time Infrastructure (RTI) does not have any facilities to perform load distribution to alleviate this problem. This paper describes an architecture that provides load distribution services over a multi-threaded RTI to improve the performance of HLA simulations. A new metric for measuring the workload for both optimistic and conservative simulation federates is proposed. Load distribution is achieved through federate migration by introducing mobility and reactivity to each simulation federate.","PeriodicalId":355772,"journal":{"name":"Eighth IEEE International Symposium on Distributed Simulation and Real-Time Applications","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134026057","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}
This paper presents an improved and updated taxonomy for Time Warp based distributed synchronization protocols. This taxonomy aims to allow the grouping of several optmistic distributed simulation synchronization protocols, with the objective to facilitate the task to decide which protocol is better for a specific simulation.
{"title":"A Revised Taxonomy for Time Warp Based Distributed Synchronization Protocols","authors":"R. S. Lobato, R. S. Ulson, M. J. Santana","doi":"10.1109/DS-RT.2004.4","DOIUrl":"https://doi.org/10.1109/DS-RT.2004.4","url":null,"abstract":"This paper presents an improved and updated taxonomy for Time Warp based distributed synchronization protocols. This taxonomy aims to allow the grouping of several optmistic distributed simulation synchronization protocols, with the objective to facilitate the task to decide which protocol is better for a specific simulation.","PeriodicalId":355772,"journal":{"name":"Eighth IEEE International Symposium on Distributed Simulation and Real-Time Applications","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115452175","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}
Collaborative Virtual Environments (CVE) are a form of telecommunication technology that bring together co-located or remote, participants within a spatial social and information context. Collaboration occurs between people and often around shared objects. Fruitful cooperation is helped by natural and intuitive ways of communicating and sharing, for which responsiveness and consistency are leading factors. Many CVEs maximise local responsiveness through a process of localisation and database replication, increasing responsiveness at the cost of lowering consistency. This is acceptable provided the application does not require the shared manipulation of objects. Those that do, require consistency control that provide sufficient synchronisation, ordering and update control, whilst maximising concurrence and thus the responsiveness of the system. This paper describes the major issues and principles of consistency control and demonstrates how we have applied many of these principles in three CVEs.
{"title":"Controlling Consistency within Collaborative Virtual Environments","authors":"D. Roberts, R. Wolff","doi":"10.1109/DS-RT.2004.13","DOIUrl":"https://doi.org/10.1109/DS-RT.2004.13","url":null,"abstract":"Collaborative Virtual Environments (CVE) are a form of telecommunication technology that bring together co-located or remote, participants within a spatial social and information context. Collaboration occurs between people and often around shared objects. Fruitful cooperation is helped by natural and intuitive ways of communicating and sharing, for which responsiveness and consistency are leading factors. Many CVEs maximise local responsiveness through a process of localisation and database replication, increasing responsiveness at the cost of lowering consistency. This is acceptable provided the application does not require the shared manipulation of objects. Those that do, require consistency control that provide sufficient synchronisation, ordering and update control, whilst maximising concurrence and thus the responsiveness of the system. This paper describes the major issues and principles of consistency control and demonstrates how we have applied many of these principles in three CVEs.","PeriodicalId":355772,"journal":{"name":"Eighth IEEE International Symposium on Distributed Simulation and Real-Time Applications","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129729505","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}
Modelling and simulation permeate all areas of business, science and engineering and increasingly complex simulation systems often require huge computing resources and data sets that are geographically distributed. The widely adopted platform for building distributed simulations is the High Level Architecture (HLA). Deficiencies associated with HLA have been well discussed in the literature. The advent of Grid technology enables the use of distributed computing resources and facilitates the access of geographically distributed data. In this paper, we propose a framework for executing large-scale distributed simulations using Grid services. The framework addresses some of the deficiencies of HLA, including dynamic discovery and resource utilization. End-users can construct large-scale distributed simulations using this framework with ease.
{"title":"Grid Services and Service Discovery for HLA-Based Distributed Simulation","authors":"Wenbo Zong, Yong Wang, Wentong Cai, S. Turner","doi":"10.1109/DS-RT.2004.22","DOIUrl":"https://doi.org/10.1109/DS-RT.2004.22","url":null,"abstract":"Modelling and simulation permeate all areas of business, science and engineering and increasingly complex simulation systems often require huge computing resources and data sets that are geographically distributed. The widely adopted platform for building distributed simulations is the High Level Architecture (HLA). Deficiencies associated with HLA have been well discussed in the literature. The advent of Grid technology enables the use of distributed computing resources and facilitates the access of geographically distributed data. In this paper, we propose a framework for executing large-scale distributed simulations using Grid services. The framework addresses some of the deficiencies of HLA, including dynamic discovery and resource utilization. End-users can construct large-scale distributed simulations using this framework with ease.","PeriodicalId":355772,"journal":{"name":"Eighth IEEE International Symposium on Distributed Simulation and Real-Time Applications","volume":"335 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127573630","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 high level architecture (HLA) standard developed by the Department of Defense in the United States is a key technology to perform distributed simulation. Inside the HLA framework, many different simulators (termed federates) may be interconnected to create a single, more complex simulator (federation). Data distribution management (DDM) is an optional subset of services that controls which federates should receive notification of state modifications made by other federates. A simple DDM implementation usually generate much more traffic than needed, while a complex one might introduce too much overhead. In this work, we describe an approach to DDM that delegates a portion of the DDM computation to a processor on the network card, in order to provide more CPU time for other federate and RTI computations, while still being able to exploit the benefits of a complex DDM implementation to reduce the amount of information exchange.
{"title":"Off-loading data distribution mananagement to network processors in HLA-based distributed simulations [mananagement read management]","authors":"Andrea Santoro, R. Fujimoto","doi":"10.1109/DS-RT.2004.32","DOIUrl":"https://doi.org/10.1109/DS-RT.2004.32","url":null,"abstract":"The high level architecture (HLA) standard developed by the Department of Defense in the United States is a key technology to perform distributed simulation. Inside the HLA framework, many different simulators (termed federates) may be interconnected to create a single, more complex simulator (federation). Data distribution management (DDM) is an optional subset of services that controls which federates should receive notification of state modifications made by other federates. A simple DDM implementation usually generate much more traffic than needed, while a complex one might introduce too much overhead. In this work, we describe an approach to DDM that delegates a portion of the DDM computation to a processor on the network card, in order to provide more CPU time for other federate and RTI computations, while still being able to exploit the benefits of a complex DDM implementation to reduce the amount of information exchange.","PeriodicalId":355772,"journal":{"name":"Eighth IEEE International Symposium on Distributed Simulation and Real-Time Applications","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126537851","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}
K. L. Morse, R. Brunton, J. Pullen, P. McAndrews, A. Tolk, James Muguira
The Experimentation Command and Control Interface (XC2I) project has developed an architecture for a Web-service based viewer/controller for use with distributed simulations supporting military experiments. As part of this activity, a capability for Interest Management with three functions is being created. The functions are Role-Based Access Control (RBAC), Area of Interest Management (AOIM), and Aggregation Interest Management (AGIM). While the approach is compatible with High Level Architecture (HLA) for Modeling and Simulation, primary information exchange takes place using the Web services, i.e. software-to-software messaging interfaces that operate over Web protocols such as XML/SOAP. This paper presents a Web Services Internet Management (WSIM) architecture designed to achieve these capabilities in a way that is compatible with simulations using the HLA. The protocols and information flow structure are described, along with the architecture's design rationale, interest management rules, and plans for its implementation. The paper concludes with a description of potential for future development of WSIM, including adoption of the Command and Control Information Exchange Data Model (C2IEDM) and use of Overlay Multicast for data distribution.
实验命令和控制接口(XC2I)项目已经开发了一个基于web服务的查看器/控制器体系结构，用于支持军事实验的分布式模拟。作为该活动的一部分，将创建一个具有三个功能的兴趣管理功能。功能包括基于角色的访问控制(RBAC)、兴趣区域管理(AOIM)和聚合兴趣管理(AGIM)。虽然该方法与用于建模和仿真的高级体系结构(HLA)兼容，但主要的信息交换是使用Web服务进行的，即通过Web协议(如XML/SOAP)操作的软件到软件消息传递接口。本文提出了一个Web Services Internet Management (WSIM)体系结构，旨在以一种与使用HLA的模拟兼容的方式实现这些功能。描述了协议和信息流结构，以及体系结构的设计原理、兴趣管理规则和实现计划。论文最后描述了WSIM未来发展的潜力，包括采用命令与控制信息交换数据模型(C2IEDM)和使用覆盖组播进行数据分发。
{"title":"An Architecture for Web-Services Based Interest Management in Real Time Distributed Simulation","authors":"K. L. Morse, R. Brunton, J. Pullen, P. McAndrews, A. Tolk, James Muguira","doi":"10.1109/DS-RT.2004.6","DOIUrl":"https://doi.org/10.1109/DS-RT.2004.6","url":null,"abstract":"The Experimentation Command and Control Interface (XC2I) project has developed an architecture for a Web-service based viewer/controller for use with distributed simulations supporting military experiments. As part of this activity, a capability for Interest Management with three functions is being created. The functions are Role-Based Access Control (RBAC), Area of Interest Management (AOIM), and Aggregation Interest Management (AGIM). While the approach is compatible with High Level Architecture (HLA) for Modeling and Simulation, primary information exchange takes place using the Web services, i.e. software-to-software messaging interfaces that operate over Web protocols such as XML/SOAP. This paper presents a Web Services Internet Management (WSIM) architecture designed to achieve these capabilities in a way that is compatible with simulations using the HLA. The protocols and information flow structure are described, along with the architecture's design rationale, interest management rules, and plans for its implementation. The paper concludes with a description of potential for future development of WSIM, including adoption of the Command and Control Information Exchange Data Model (C2IEDM) and use of Overlay Multicast for data distribution.","PeriodicalId":355772,"journal":{"name":"Eighth IEEE International Symposium on Distributed Simulation and Real-Time Applications","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130879929","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}
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