A framework of open interoperable simulators for computer architecture is long overdue. Today there are many separate, uncoordinated efforts to develop simulation and modeling artifacts (tools) for computer architecture research. The artifacts are used to empirically evaluate new computer architecture innovations and compare them with the state of the art. The artifacts are usually developed by individual groups, often for a specific purpose, and may not be publicly released. Consequently, it is difficult to leverage investment in artifact development and to repeat or reproduce experiments. In this position paper, we present recommendations and a roadmap for sharing and building open-source, interoperable simulation and modeling artifacts. The recommendations are the outcome of a community workshop involving industry, government and academia to determine how to coordinate effort, share tools and improve methodology.
{"title":"A Roadmap and Plan of Action for Community-Supported Empirical Evaluation in Computer Architecture","authors":"B. Childers, A. Jones, D. Mossé","doi":"10.1145/2723872.2723886","DOIUrl":"https://doi.org/10.1145/2723872.2723886","url":null,"abstract":"A framework of open interoperable simulators for computer architecture is long overdue. Today there are many separate, uncoordinated efforts to develop simulation and modeling artifacts (tools) for computer architecture research. The artifacts are used to empirically evaluate new computer architecture innovations and compare them with the state of the art. The artifacts are usually developed by individual groups, often for a specific purpose, and may not be publicly released. Consequently, it is difficult to leverage investment in artifact development and to repeat or reproduce experiments. In this position paper, we present recommendations and a roadmap for sharing and building open-source, interoperable simulation and modeling artifacts. The recommendations are the outcome of a community workshop involving industry, government and academia to determine how to coordinate effort, share tools and improve methodology.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":"46 1","pages":"108-117"},"PeriodicalIF":0.0,"publicationDate":"2015-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82809934","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 purpose of a screening experiment is to identify significant factors and interactions on a response for a system. Engineered systems are complex in part due to their size. To apply traditional experimental designs for screening in complex engineered systems requires either restricting the factors considered, which automatically restricts the interactions to those in the set, or restricting interest to main effects, which fails to consider any possible interactions. To address this problem we propose a locating array (LA) as a screening design. Locating arrays exhibit logarithmic growth in the number of factors because their focus is on identification rather than on measurement. This makes practical the consideration of an order of magnitude more factors in experimentation than traditional screening designs. We present preliminary results applying an LA for screening the response of TCP throughput in a simulation model of a mobile wireless network. The full-factorial design for this system is infeasible (over 1043 design points!) yet an LA has only 421 design points. We validate the significance of the identified factors and interactions independently using the statistical software JMP. Screening using locating arrays is viable and yields useful models.
{"title":"Locating Arrays: A New Experimental Design for Screening Complex Engineered Systems","authors":"A. Aldaco, C. Colbourn, V. Syrotiuk","doi":"10.1145/2723872.2723878","DOIUrl":"https://doi.org/10.1145/2723872.2723878","url":null,"abstract":"The purpose of a screening experiment is to identify significant factors and interactions on a response for a system. Engineered systems are complex in part due to their size. To apply traditional experimental designs for screening in complex engineered systems requires either restricting the factors considered, which automatically restricts the interactions to those in the set, or restricting interest to main effects, which fails to consider any possible interactions. To address this problem we propose a locating array (LA) as a screening design. Locating arrays exhibit logarithmic growth in the number of factors because their focus is on identification rather than on measurement. This makes practical the consideration of an order of magnitude more factors in experimentation than traditional screening designs. We present preliminary results applying an LA for screening the response of TCP throughput in a simulation model of a mobile wireless network. The full-factorial design for this system is infeasible (over 1043 design points!) yet an LA has only 421 design points. We validate the significance of the identified factors and interactions independently using the statistical software JMP. Screening using locating arrays is viable and yields useful models.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":"10 1","pages":"31-40"},"PeriodicalIF":0.0,"publicationDate":"2015-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85290653","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}
Valter Balegas, S. Duarte, Carla Ferreira, R. Rodrigues, Nuno M. Preguiça, Mahsa Najafzadeh, M. Shapiro
Today's global services and applications are expected to be highly available, scale to an unprecedented number of clients, and offer reliable, low-latency operations. This can be achieved through geo-replication, particularly when data consistency is relaxed. There are, however, applications whose data must obey global invariants at all times. Strong consistency protocols easily address this issue, but require global coordination among replicas and inevitably degrade application throughput and latency. While coordination is an inherent requirement for maintaining global application invariants, there are instances where coordination on a per operation basis can be avoided. In particular, it has been shown that either moving coordination outside the critical path for executing operations, or having one coordination round for multiple operations, are both effective ways to maintain global invariants and avoid most of the penalties of coordination. However, current georeplication protocols still have not taken advantage of these observations. In this paper, we review the design space of current solutions for building geo-replicated applications and present our guiding vision towards a general technique for providing global application invariants under eventual consistency, as a much cheaper alternative to strong consistency.
{"title":"Towards Fast Invariant Preservation in Geo-replicated Systems","authors":"Valter Balegas, S. Duarte, Carla Ferreira, R. Rodrigues, Nuno M. Preguiça, Mahsa Najafzadeh, M. Shapiro","doi":"10.1145/2723872.2723889","DOIUrl":"https://doi.org/10.1145/2723872.2723889","url":null,"abstract":"Today's global services and applications are expected to be highly available, scale to an unprecedented number of clients, and offer reliable, low-latency operations. This can be achieved through geo-replication, particularly when data consistency is relaxed. There are, however, applications whose data must obey global invariants at all times. Strong consistency protocols easily address this issue, but require global coordination among replicas and inevitably degrade application throughput and latency.\u0000 While coordination is an inherent requirement for maintaining global application invariants, there are instances where coordination on a per operation basis can be avoided. In particular, it has been shown that either moving coordination outside the critical path for executing operations, or having one coordination round for multiple operations, are both effective ways to maintain global invariants and avoid most of the penalties of coordination. However, current georeplication protocols still have not taken advantage of these observations.\u0000 In this paper, we review the design space of current solutions for building geo-replicated applications and present our guiding vision towards a general technique for providing global application invariants under eventual consistency, as a much cheaper alternative to strong consistency.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":"128 1","pages":"121-125"},"PeriodicalIF":0.0,"publicationDate":"2015-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91112146","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}
Being able to repeat experiments is considered a hallmark of the scientific method, used to confirm or refute hypotheses and previously obtained results. But this can take many forms, from precise repetition using the original experimental artifacts, to conceptual reproduction of the main experimental idea using new artifacts. Furthermore, the conclusions from previous work can also be corroborated using a different experimental methodology altogether. In order to promote a better understanding and use of such methodologies we propose precise definitions for different terms, and suggest when and why each should be used.
{"title":"From Repeatability to Reproducibility and Corroboration","authors":"D. Feitelson","doi":"10.1145/2723872.2723875","DOIUrl":"https://doi.org/10.1145/2723872.2723875","url":null,"abstract":"Being able to repeat experiments is considered a hallmark of the scientific method, used to confirm or refute hypotheses and previously obtained results. But this can take many forms, from precise repetition using the original experimental artifacts, to conceptual reproduction of the main experimental idea using new artifacts. Furthermore, the conclusions from previous work can also be corroborated using a different experimental methodology altogether. In order to promote a better understanding and use of such methodologies we propose precise definitions for different terms, and suggest when and why each should be used.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":"119 1","pages":"3-11"},"PeriodicalIF":0.0,"publicationDate":"2015-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76286601","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}
Mayank Varia, Benjamin Price, Nicholas Hwang, Ariel Hamlin, Jonathan C. Herzog, Jill Poland, Michael Reschly, Sophia Yakoubov, R. Cunningham
This work presents the results of a three-year project that assessed nine different privacy-preserving data search systems. We detail the design of a software assessment framework that focuses on low system footprint, repeatability, and reusability. A unique achievement of this project was the automation and integration of the entire test process, from the production and execution of tests to the generation of human-readable evaluation reports. We synthesize our experiences into a set of simple mantras that we recommend following in the design of any assessment framework.
{"title":"Automated Assessment of Secure Search Systems","authors":"Mayank Varia, Benjamin Price, Nicholas Hwang, Ariel Hamlin, Jonathan C. Herzog, Jill Poland, Michael Reschly, Sophia Yakoubov, R. Cunningham","doi":"10.1145/2723872.2723877","DOIUrl":"https://doi.org/10.1145/2723872.2723877","url":null,"abstract":"This work presents the results of a three-year project that assessed nine different privacy-preserving data search systems. We detail the design of a software assessment framework that focuses on low system footprint, repeatability, and reusability. A unique achievement of this project was the automation and integration of the entire test process, from the production and execution of tests to the generation of human-readable evaluation reports. We synthesize our experiences into a set of simple mantras that we recommend following in the design of any assessment framework.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":"66 1","pages":"22-30"},"PeriodicalIF":0.0,"publicationDate":"2015-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72868712","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. Birman, Márk Jelasity, Robert D. Kleinberg, E. Tremel
New technologies for computerized metering and data collection in the electrical power grid promise to create a more efficient, cost-effective, and adaptable smart grid. However, naive implementations of smart grid data collection could jeopardize the privacy of consumers, and concerns about privacy are a significant obstacle to the rollout of smart grid technology. Our work proposes a design for a smart metering system that will allow utilities to use the collected data effectively while preserving the privacy of individual consumers.
{"title":"Building a Secure and Privacy-Preserving Smart Grid","authors":"K. Birman, Márk Jelasity, Robert D. Kleinberg, E. Tremel","doi":"10.1145/2723872.2723891","DOIUrl":"https://doi.org/10.1145/2723872.2723891","url":null,"abstract":"New technologies for computerized metering and data collection in the electrical power grid promise to create a more efficient, cost-effective, and adaptable smart grid. However, naive implementations of smart grid data collection could jeopardize the privacy of consumers, and concerns about privacy are a significant obstacle to the rollout of smart grid technology. Our work proposes a design for a smart metering system that will allow utilities to use the collected data effectively while preserving the privacy of individual consumers.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":"44 1","pages":"131-136"},"PeriodicalIF":0.0,"publicationDate":"2015-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88633897","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}
There are many compelling reasons to use a shared, public testbed such as GENI, Emulab, or PlanetLab to conduct experiments in computer science and networking. These testbeds support creating experiments with a large and diverse set of resources. Moreover these testbeds are constructed to inherently support the repeatability of experiments as required for scientifically sound research. Finally, the artifacts needed for a researcher to repeat their own experiment can be shared so that others can readily repeat the experiment in the same environment. However using a shared, public testbed is different from conducting experiments on resources either owned by the experimenter or someone the experimenter knows. Experiments on shared, public testbeds are more likely to use large topologies, use scarce resources, and need to be tolerant to outages and maintenances in the testbed. In addition, experimenters may not have access to low-level debugging information. This paper describes a methodology for new experimenters to write and deploy repeatable and sharable experiments which deal with these challenges by: having a clear plan; automating the execution and analysis of an experiment by following best practices from software engineering and system administration; and building scalable experiments. In addition, the paper describes a case study run on the GENI testbed which illustrates the methodology described.
{"title":"Creating Repeatable Computer Science and Networking Experiments on Shared, Public Testbeds","authors":"Sarah Edwards, Xuan Liu, N. Riga","doi":"10.1145/2723872.2723884","DOIUrl":"https://doi.org/10.1145/2723872.2723884","url":null,"abstract":"There are many compelling reasons to use a shared, public testbed such as GENI, Emulab, or PlanetLab to conduct experiments in computer science and networking. These testbeds support creating experiments with a large and diverse set of resources. Moreover these testbeds are constructed to inherently support the repeatability of experiments as required for scientifically sound research. Finally, the artifacts needed for a researcher to repeat their own experiment can be shared so that others can readily repeat the experiment in the same environment.\u0000 However using a shared, public testbed is different from conducting experiments on resources either owned by the experimenter or someone the experimenter knows. Experiments on shared, public testbeds are more likely to use large topologies, use scarce resources, and need to be tolerant to outages and maintenances in the testbed. In addition, experimenters may not have access to low-level debugging information.\u0000 This paper describes a methodology for new experimenters to write and deploy repeatable and sharable experiments which deal with these challenges by: having a clear plan; automating the execution and analysis of an experiment by following best practices from software engineering and system administration; and building scalable experiments. In addition, the paper describes a case study run on the GENI testbed which illustrates the methodology described.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":"1 1","pages":"90-99"},"PeriodicalIF":0.0,"publicationDate":"2015-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86832728","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}
Qin Jia, Zhiming Shen, Weijia Song, R. V. Renesse, Hakim Weatherspoon
Infrastructure as a Service (IaaS) clouds couple applications tightly with the underlying infrastructures and services. This vendor lock-in problem forces users to apply ad-hoc deployment strategies in order to tolerate cloud failures, and limits the ability of doing virtual machine (VM) migration and resource scaling across different clouds. This paper presents the Supercloud, a cloud service comprising resources obtained from several diverse IaaS cloud providers, and discusses opportunities, limitations, and future research directions. Currently, the Supercloud has been deployed using resources from several major cloud providers, including Amazon EC2, Rackspace, HP Cloud, and some private clouds. VMs run in a virtual network and can be migrated seamlessly across different clouds, with different hypervisors and device models. Using case studies we demonstrate that, being able to deploy applications to more regions and granting more control to end-users, the Supercloud can reduce latency and cost compared to the underlying cloud providers.
{"title":"Supercloud: Opportunities and Challenges","authors":"Qin Jia, Zhiming Shen, Weijia Song, R. V. Renesse, Hakim Weatherspoon","doi":"10.1145/2723872.2723892","DOIUrl":"https://doi.org/10.1145/2723872.2723892","url":null,"abstract":"Infrastructure as a Service (IaaS) clouds couple applications tightly with the underlying infrastructures and services. This vendor lock-in problem forces users to apply ad-hoc deployment strategies in order to tolerate cloud failures, and limits the ability of doing virtual machine (VM) migration and resource scaling across different clouds.\u0000 This paper presents the Supercloud, a cloud service comprising resources obtained from several diverse IaaS cloud providers, and discusses opportunities, limitations, and future research directions. Currently, the Supercloud has been deployed using resources from several major cloud providers, including Amazon EC2, Rackspace, HP Cloud, and some private clouds. VMs run in a virtual network and can be migrated seamlessly across different clouds, with different hypervisors and device models. Using case studies we demonstrate that, being able to deploy applications to more regions and granting more control to end-users, the Supercloud can reduce latency and cost compared to the underlying cloud providers.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":"37 1","pages":"137-141"},"PeriodicalIF":0.0,"publicationDate":"2015-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90793789","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 commonly used technique for evaluating and comparing the performance of systems using 802.11 (WiFi) networks is to conduct experiments. This approach is appealing and important because it inherently captures critical properties of wireless signal transmission that are difficult to analytically model and simulate. Unfortunately, obtaining consistent and statistically meaningful empirical results using 802.11 networks, even in well-controlled environments, can be quite challenging and time consuming because channel conditions can vary over time. In this paper, we use 2.4 and 5 GHz 802.11n MIMO networks to study different methodologies that could be used to evaluate and compare the performance of different alternatives used in 802.11 systems (e.g., different systems, configurations or algorithms). We first illustrate that some of the more commonly used methods in existing research are flawed and explain why. We then describe a methodology called multiple interleaved trials that, to our knowledge, has not been used for, or studied on, 802.11 networks. We evaluate this methodology and find that it can be used to repeat experiments and to compare the performance of different alternatives. Finally, we discuss other possible applications of this approach for comparative performance evaluations.
{"title":"Conducting Repeatable Experiments and Fair Comparisons using 802.11n MIMO Networks","authors":"A. Abedi, Andrew Heard, Tim Brecht","doi":"10.1145/2723872.2723879","DOIUrl":"https://doi.org/10.1145/2723872.2723879","url":null,"abstract":"A commonly used technique for evaluating and comparing the performance of systems using 802.11 (WiFi) networks is to conduct experiments. This approach is appealing and important because it inherently captures critical properties of wireless signal transmission that are difficult to analytically model and simulate. Unfortunately, obtaining consistent and statistically meaningful empirical results using 802.11 networks, even in well-controlled environments, can be quite challenging and time consuming because channel conditions can vary over time.\u0000 In this paper, we use 2.4 and 5 GHz 802.11n MIMO networks to study different methodologies that could be used to evaluate and compare the performance of different alternatives used in 802.11 systems (e.g., different systems, configurations or algorithms). We first illustrate that some of the more commonly used methods in existing research are flawed and explain why. We then describe a methodology called multiple interleaved trials that, to our knowledge, has not been used for, or studied on, 802.11 networks. We evaluate this methodology and find that it can be used to repeat experiments and to compare the performance of different alternatives. Finally, we discuss other possible applications of this approach for comparative performance evaluations.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":"10 1","pages":"41-50"},"PeriodicalIF":0.0,"publicationDate":"2015-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76397746","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}
R. Ricci, Gary Wong, L. Stoller, Kirk Webb, Jonathon Duerig, Keith Downie, Mike Hibler
Repeating research in computer science requires more than just code and data: it requires an appropriate environment in which to run experiments. In some cases, this environment appears fairly straightforward: it consists of a particular operating system and set of required libraries. In many cases, however, it is considerably more complex: the execution environment may be an entire network, may involve complex and fragile configuration of the dependencies, or may require large amounts of resources in terms of computation cycles, network bandwidth, or storage. Even the "straightforward" case turns out to be surprisingly intricate: there may be explicit or hidden dependencies on compilers, kernel quirks, details of the ISA, etc. The result is that when one tries to repeat published results, creating an environment sufficiently similar to one in which the experiment was originally run can be troublesome; this problem only gets worse as time passes. What the computer science community needs, then, are environments that have the explicit goal of enabling repeatable research. This paper outlines the problem of repeatable research environments, presents a set of requirements for such environments, and describes one facility that attempts to address them.
{"title":"Apt: A Platform for Repeatable Research in Computer Science","authors":"R. Ricci, Gary Wong, L. Stoller, Kirk Webb, Jonathon Duerig, Keith Downie, Mike Hibler","doi":"10.1145/2723872.2723885","DOIUrl":"https://doi.org/10.1145/2723872.2723885","url":null,"abstract":"Repeating research in computer science requires more than just code and data: it requires an appropriate environment in which to run experiments. In some cases, this environment appears fairly straightforward: it consists of a particular operating system and set of required libraries. In many cases, however, it is considerably more complex: the execution environment may be an entire network, may involve complex and fragile configuration of the dependencies, or may require large amounts of resources in terms of computation cycles, network bandwidth, or storage. Even the \"straightforward\" case turns out to be surprisingly intricate: there may be explicit or hidden dependencies on compilers, kernel quirks, details of the ISA, etc. The result is that when one tries to repeat published results, creating an environment sufficiently similar to one in which the experiment was originally run can be troublesome; this problem only gets worse as time passes. What the computer science community needs, then, are environments that have the explicit goal of enabling repeatable research. This paper outlines the problem of repeatable research environments, presents a set of requirements for such environments, and describes one facility that attempts to address them.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":"21 1","pages":"100-107"},"PeriodicalIF":0.0,"publicationDate":"2015-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75331431","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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