Viking [13] is a multi-spanning-tree Ethernet architecture that is designed to leverage commodity Ethernet switches to support Metro-Ethernet services. In particular, it exploits VLAN switching to provide network-wide load balancing across a metro-area network. However, Viking assumes the traffic matrix is fixed; as time goes by, the input load may gradually deviate from the assumed traffic matrix because of addition/deletion of subscribers and/or changes in bandwidth requirements from existing subscribers. Therefore, dynamic resource management is required to accommodate such traffic load fluctuations. This paper describes the design, implementation and evaluation of an autonomic network resource management system called Viking2 that enables a Metro-Ethernet network to dynamically self-reconfigure itself, with minimal human intervention, to adapt to changing traffic loads. In particular, whenever possible Viking2 uses a local repair approach to eliminate congestion while minimizing the number of flows affected. If local repair cannot fix a congestion problem, Viking2 resorts to a global reconfiguration approach that recomputes a new path for every flow and deploys the new routing state in a way that reduces the disruption during the period of transition to the minimum. Simulation results show that compared with the original Viking, Viking2 can indeed significantly improve a network's ability to dynamically adapt itself to changing traffic loads, to minimize the degree of congestion during normal network operation, and to increase the total effective network capacity.
{"title":"Autonomic Resource Management for Multiple-Spanning-Tree Metro-Ethernet Networks","authors":"Shibiao Lin, Srikant Sharma, T. Chiueh","doi":"10.1109/NCA.2007.10","DOIUrl":"https://doi.org/10.1109/NCA.2007.10","url":null,"abstract":"Viking [13] is a multi-spanning-tree Ethernet architecture that is designed to leverage commodity Ethernet switches to support Metro-Ethernet services. In particular, it exploits VLAN switching to provide network-wide load balancing across a metro-area network. However, Viking assumes the traffic matrix is fixed; as time goes by, the input load may gradually deviate from the assumed traffic matrix because of addition/deletion of subscribers and/or changes in bandwidth requirements from existing subscribers. Therefore, dynamic resource management is required to accommodate such traffic load fluctuations. This paper describes the design, implementation and evaluation of an autonomic network resource management system called Viking2 that enables a Metro-Ethernet network to dynamically self-reconfigure itself, with minimal human intervention, to adapt to changing traffic loads. In particular, whenever possible Viking2 uses a local repair approach to eliminate congestion while minimizing the number of flows affected. If local repair cannot fix a congestion problem, Viking2 resorts to a global reconfiguration approach that recomputes a new path for every flow and deploys the new routing state in a way that reduces the disruption during the period of transition to the minimum. Simulation results show that compared with the original Viking, Viking2 can indeed significantly improve a network's ability to dynamically adapt itself to changing traffic loads, to minimize the degree of congestion during normal network operation, and to increase the total effective network capacity.","PeriodicalId":135395,"journal":{"name":"Sixth IEEE International Symposium on Network Computing and Applications (NCA 2007)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125191994","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}
In this paper we present a wide area distributed system using a content-based publish/subscribe communication middleware which can deterministically detect and report failures with respect to timely message delivery and message omission. Our approach does not require external clock synchronization nor does it impose any constraints on the publish/subscribe middleware. We show that our system performs better and is safer than when using NTP for external clock synchronization. We provide a proof of concept implementation and present results of experiments carried out in the PlanetLab environment.
{"title":"Fail-Aware Publish/Subscribe","authors":"Zbigniew Jerzak, Robert Fach, C. Fetzer","doi":"10.1109/NCA.2007.24","DOIUrl":"https://doi.org/10.1109/NCA.2007.24","url":null,"abstract":"In this paper we present a wide area distributed system using a content-based publish/subscribe communication middleware which can deterministically detect and report failures with respect to timely message delivery and message omission. Our approach does not require external clock synchronization nor does it impose any constraints on the publish/subscribe middleware. We show that our system performs better and is safer than when using NTP for external clock synchronization. We provide a proof of concept implementation and present results of experiments carried out in the PlanetLab environment.","PeriodicalId":135395,"journal":{"name":"Sixth IEEE International Symposium on Network Computing and Applications (NCA 2007)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122765051","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}
Peer-to-peer (P2P) file sharing accounts for a very significant part of the Internet's traffic, translating into significant peering costs for ISPs. It has been noticed that, just like WWW traffic, P2P file sharing traffic shows locality properties, which are not exploited by current P2P file sharing protocols. We propose a novel peer selection algorithm, adaptive search radius (ASR), whose primary goal is to reduce ISPs' peering costs, where peers exploit locality by only downloading from those other peers which are nearest (in network hops). Simulation studies, using the eMule protocol, show that ASR benefits both ISPs, by globally reducing P2P file sharing traffic, and users, who experience faster downloads.
{"title":"Adaptive Search Radius - Lowering Internet P2P File-Sharing Traffic through Self-Restraint","authors":"R. Pereira, T. Vazão, R. Rodrigues","doi":"10.1109/NCA.2007.6","DOIUrl":"https://doi.org/10.1109/NCA.2007.6","url":null,"abstract":"Peer-to-peer (P2P) file sharing accounts for a very significant part of the Internet's traffic, translating into significant peering costs for ISPs. It has been noticed that, just like WWW traffic, P2P file sharing traffic shows locality properties, which are not exploited by current P2P file sharing protocols. We propose a novel peer selection algorithm, adaptive search radius (ASR), whose primary goal is to reduce ISPs' peering costs, where peers exploit locality by only downloading from those other peers which are nearest (in network hops). Simulation studies, using the eMule protocol, show that ASR benefits both ISPs, by globally reducing P2P file sharing traffic, and users, who experience faster downloads.","PeriodicalId":135395,"journal":{"name":"Sixth IEEE International Symposium on Network Computing and Applications (NCA 2007)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123913862","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 advent of the mobile Web and the increasing demand for personalized contents arise the need for computationally expensive services, such as dynamic generation and on-the- fly adaptation of contents. Providing these services exacerbates the performance issues that have to be addressed by the underlying Web architecture. When performance issues are addressed through geographically distributed Web systems with a large number of nodes located on the network edge, the dispatching mechanism that distributes requests among the system nodes becomes a critical element. In this paper, we investigate how the granularity of re- quest dispatching may affect the performance of a distributed Web system for personalized contents. Through a real prototype, we compare dispatching mechanisms operating at various levels of granularity for different workload and network scenarios. We demonstrate that the choice of the best granularity for request dispatching strongly depends on the characteristics of the workload in terms of heterogeneity and computational requirements. A coarse- grain dispatching is preferable only when the requests have similar computational requirements. In all other instances of skewed workloads, that we can consider more realistic, a fine-grain dispatching augments the control on the node load and allows the system to achieve better performance.
{"title":"Impact of request dispatching granularity in geographically distributed Web systems","authors":"M. Andreolini, C. Canali, R. Lancellotti","doi":"10.1109/NCA.2007.28","DOIUrl":"https://doi.org/10.1109/NCA.2007.28","url":null,"abstract":"The advent of the mobile Web and the increasing demand for personalized contents arise the need for computationally expensive services, such as dynamic generation and on-the- fly adaptation of contents. Providing these services exacerbates the performance issues that have to be addressed by the underlying Web architecture. When performance issues are addressed through geographically distributed Web systems with a large number of nodes located on the network edge, the dispatching mechanism that distributes requests among the system nodes becomes a critical element. In this paper, we investigate how the granularity of re- quest dispatching may affect the performance of a distributed Web system for personalized contents. Through a real prototype, we compare dispatching mechanisms operating at various levels of granularity for different workload and network scenarios. We demonstrate that the choice of the best granularity for request dispatching strongly depends on the characteristics of the workload in terms of heterogeneity and computational requirements. A coarse- grain dispatching is preferable only when the requests have similar computational requirements. In all other instances of skewed workloads, that we can consider more realistic, a fine-grain dispatching augments the control on the node load and allows the system to achieve better performance.","PeriodicalId":135395,"journal":{"name":"Sixth IEEE International Symposium on Network Computing and Applications (NCA 2007)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127751162","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}
Replication is a primary means to achieve fault tolerance in distributed systems. While replication techniques are well known and have been widely applied in distributed object and database systems, they have not yet been extensively used in service oriented systems. However, if the success of service oriented computing shall continue in critical settings, replication middleware will play a crucial role in service oriented infrastructures. Thus, we contribute with a discussion of our experiences in building distributed object and service replication middleware and present the main lessons learned. Our conclusions are drawn from several replication middleware implementations built upon J2EE, .NET, CORBA, and Axis2.
{"title":"Experiences from Building Service and Object Replication Middleware","authors":"Johannes Osrael, Lorenz Froihofer, K. M. Göschka","doi":"10.1109/NCA.2007.21","DOIUrl":"https://doi.org/10.1109/NCA.2007.21","url":null,"abstract":"Replication is a primary means to achieve fault tolerance in distributed systems. While replication techniques are well known and have been widely applied in distributed object and database systems, they have not yet been extensively used in service oriented systems. However, if the success of service oriented computing shall continue in critical settings, replication middleware will play a crucial role in service oriented infrastructures. Thus, we contribute with a discussion of our experiences in building distributed object and service replication middleware and present the main lessons learned. Our conclusions are drawn from several replication middleware implementations built upon J2EE, .NET, CORBA, and Axis2.","PeriodicalId":135395,"journal":{"name":"Sixth IEEE International Symposium on Network Computing and Applications (NCA 2007)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132680807","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}
As disk storage density increases and data availability requirements become ever more demanding, data replication is increasingly an indispensable feature of enterprise-class storage systems. For highly available storage systems, every disk block is typically replicated on a local mirror server and a remote mirror server in addition to being stored on the main storage server. In a network storage environment, this N-way data replication increases the write traffic load on the storage client's network interface by N times. Multicast is a natural solution to this problem. However, existing storage area network technologies such as fibre channel and Ethernet do not provide adequate support for linklayer multicast. This paper describes a novel reliable multicast mechanism for Ethernet-based storage area networks that effectively exploits the virtual LAN technology and is able to keep the traffic load of N-way replication roughly at the same level as the no-replication case regardless of the value of N. This technology greatly increases the appeal of using Ethernet as the physical-layer technology for storage area networking, as fibre channel networks currently do not support such in-network replication. Performance measurements on an iSCSI-based network storage system demonstrate that the proposed reliable multicast mechanism is able to reduce the end-to-end data transport time by a factor of 2.6 for three-way replication when the disk write size is more than 4 Mbytes.
{"title":"Transparent Reliable Multicast for Ethernet-Based Storage Area Networks","authors":"Shibiao Lin, Maohua Lu, T. Chiueh","doi":"10.1109/NCA.2007.51","DOIUrl":"https://doi.org/10.1109/NCA.2007.51","url":null,"abstract":"As disk storage density increases and data availability requirements become ever more demanding, data replication is increasingly an indispensable feature of enterprise-class storage systems. For highly available storage systems, every disk block is typically replicated on a local mirror server and a remote mirror server in addition to being stored on the main storage server. In a network storage environment, this N-way data replication increases the write traffic load on the storage client's network interface by N times. Multicast is a natural solution to this problem. However, existing storage area network technologies such as fibre channel and Ethernet do not provide adequate support for linklayer multicast. This paper describes a novel reliable multicast mechanism for Ethernet-based storage area networks that effectively exploits the virtual LAN technology and is able to keep the traffic load of N-way replication roughly at the same level as the no-replication case regardless of the value of N. This technology greatly increases the appeal of using Ethernet as the physical-layer technology for storage area networking, as fibre channel networks currently do not support such in-network replication. Performance measurements on an iSCSI-based network storage system demonstrate that the proposed reliable multicast mechanism is able to reduce the end-to-end data transport time by a factor of 2.6 for three-way replication when the disk write size is more than 4 Mbytes.","PeriodicalId":135395,"journal":{"name":"Sixth IEEE International Symposium on Network Computing and Applications (NCA 2007)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122072920","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}
Clustering protocols are often used in sensor networks. In many deployment scenarios, security is a key concern. In this paper we provide a secure solution to a commonly used clustering protocol, the LEACH protocol. We show that our protocol, the GS-LEACH protocol is more energy efficient than any of the secure flavors of LEACH. The GS-LEACH (grid-based secure LEACH) protocol uses pre deployment key distribution using prior knowledge of the deployment area. We also provide a detailed security analysis of our protocol and show that it is more secure than the secure versions of LEACH. Finally with the results of our simulation experiments we show that our protocol is very energy efficient and provides a longer network lifetime compared to the other flavors of LEACH.
{"title":"Security and performance analysis of a secure clustering protocol for sensor networks","authors":"P. Banerjee, D. Jacobson, S. Lahiri","doi":"10.1109/NCA.2007.40","DOIUrl":"https://doi.org/10.1109/NCA.2007.40","url":null,"abstract":"Clustering protocols are often used in sensor networks. In many deployment scenarios, security is a key concern. In this paper we provide a secure solution to a commonly used clustering protocol, the LEACH protocol. We show that our protocol, the GS-LEACH protocol is more energy efficient than any of the secure flavors of LEACH. The GS-LEACH (grid-based secure LEACH) protocol uses pre deployment key distribution using prior knowledge of the deployment area. We also provide a detailed security analysis of our protocol and show that it is more secure than the secure versions of LEACH. Finally with the results of our simulation experiments we show that our protocol is very energy efficient and provides a longer network lifetime compared to the other flavors of LEACH.","PeriodicalId":135395,"journal":{"name":"Sixth IEEE International Symposium on Network Computing and Applications (NCA 2007)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129833986","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}
A. Jackson, W. Milliken, C. Santivanez, M. Condell, W. Strayer
The Internet is an extremely complex system, and it is essential that we be able to make accurate measurements in order to understand its underlying behavior or to detect improper behavior (e.g., attacks). The reality, however, is that it is impractical to fully instrument anything but relatively small networks and impossible to even partially instrument many parts of the Internet. This paper analyzes a subset of the general monitor placement problem where the goal is to maximize the coverage of the entire universe of potential communication pairs (i.e., source and destination are randomly distributed in the routable Internet address space). This issue arises, for example, when trying to detect/track a distributed attack. We present results from a simulation, seeded with data from skitter and RouteViews, that indicate we can monitor a packet with a high probability by monitoring relatively few points in the Internet. Our analysis suggests that the preferred strategy to place monitors should be to instrument one or two specific inter-AS links per AS for many ASes rather than deeply instrumenting a subset of the largest ASes.
{"title":"A Topological Analysis of Monitor Placement","authors":"A. Jackson, W. Milliken, C. Santivanez, M. Condell, W. Strayer","doi":"10.1109/NCA.2007.3","DOIUrl":"https://doi.org/10.1109/NCA.2007.3","url":null,"abstract":"The Internet is an extremely complex system, and it is essential that we be able to make accurate measurements in order to understand its underlying behavior or to detect improper behavior (e.g., attacks). The reality, however, is that it is impractical to fully instrument anything but relatively small networks and impossible to even partially instrument many parts of the Internet. This paper analyzes a subset of the general monitor placement problem where the goal is to maximize the coverage of the entire universe of potential communication pairs (i.e., source and destination are randomly distributed in the routable Internet address space). This issue arises, for example, when trying to detect/track a distributed attack. We present results from a simulation, seeded with data from skitter and RouteViews, that indicate we can monitor a packet with a high probability by monitoring relatively few points in the Internet. Our analysis suggests that the preferred strategy to place monitors should be to instrument one or two specific inter-AS links per AS for many ASes rather than deeply instrumenting a subset of the largest ASes.","PeriodicalId":135395,"journal":{"name":"Sixth IEEE International Symposium on Network Computing and Applications (NCA 2007)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122974879","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}
Gregory J. Brault, Christopher J. Augeri, B. Mullins, R. Baldwin, Christopher B. Mayer
A skip graph is a resilient application-layer routing structure that supports range queries of distributed k-dimensional data. By sorting deterministic keys into groups based on locally computed random membership vectors, nodes in a standard skip graph can optimize range query performance in mobile networks such as unmanned aerial vehicle swarms. We propose a skip graph extension that inverts the key and membership vector roles and bases group membership on deterministic vectors derived from the z-ordering of k-dimensional data and sorting within groups is based on locally computed random keys.
{"title":"Enabling Skip Graphs to Process K-Dimensional Range Queries in a Mobile Sensor Network","authors":"Gregory J. Brault, Christopher J. Augeri, B. Mullins, R. Baldwin, Christopher B. Mayer","doi":"10.1109/NCA.2007.18","DOIUrl":"https://doi.org/10.1109/NCA.2007.18","url":null,"abstract":"A skip graph is a resilient application-layer routing structure that supports range queries of distributed k-dimensional data. By sorting deterministic keys into groups based on locally computed random membership vectors, nodes in a standard skip graph can optimize range query performance in mobile networks such as unmanned aerial vehicle swarms. We propose a skip graph extension that inverts the key and membership vector roles and bases group membership on deterministic vectors derived from the z-ordering of k-dimensional data and sorting within groups is based on locally computed random keys.","PeriodicalId":135395,"journal":{"name":"Sixth IEEE International Symposium on Network Computing and Applications (NCA 2007)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116555105","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}
A reparable database management system has the ability to automatically undo the set of transactions that are corrupted by a human error or malicious attack. The key technical challenge to building repairable database management systems is how to accurately and efficiently keep track of inter-transaction dependencies that take place through a database as well as through application logic. In this paper, we present the design, implementation and evaluation of the inter-transaction dependency tracking mechanisms used in a repairable database management system called RDB2, which adds fast repairability in a portable way to a commercial DBMS Oracle 9.2.0. RDB2 eliminates dependencies due to false sharing using fine-grained inter-transaction dependency tracking, and is able to successfully identify a major source of false negatives, phantom dependencies. With these advanced inter-transaction dependency tracking mechanisms, RDB2 can significantly improve the availability of modern DBMSs by facilitating and sometimes even automating the damage repair process after an error or attack. Performance measurements on the fully operational prototypes under the TPC-C benchmark show that the run-time throughput penalty of these enhanced inter-transaction dependency tracking mechanisms is less than 18%.
{"title":"Accurate Inter-Transaction Dependency Tracking for Repairable DBMS","authors":"Shweta Bajpai, A. Smirnov, T. Chiueh","doi":"10.1109/NCA.2007.5","DOIUrl":"https://doi.org/10.1109/NCA.2007.5","url":null,"abstract":"A reparable database management system has the ability to automatically undo the set of transactions that are corrupted by a human error or malicious attack. The key technical challenge to building repairable database management systems is how to accurately and efficiently keep track of inter-transaction dependencies that take place through a database as well as through application logic. In this paper, we present the design, implementation and evaluation of the inter-transaction dependency tracking mechanisms used in a repairable database management system called RDB2, which adds fast repairability in a portable way to a commercial DBMS Oracle 9.2.0. RDB2 eliminates dependencies due to false sharing using fine-grained inter-transaction dependency tracking, and is able to successfully identify a major source of false negatives, phantom dependencies. With these advanced inter-transaction dependency tracking mechanisms, RDB2 can significantly improve the availability of modern DBMSs by facilitating and sometimes even automating the damage repair process after an error or attack. Performance measurements on the fully operational prototypes under the TPC-C benchmark show that the run-time throughput penalty of these enhanced inter-transaction dependency tracking mechanisms is less than 18%.","PeriodicalId":135395,"journal":{"name":"Sixth IEEE International Symposium on Network Computing and Applications (NCA 2007)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116144973","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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