For modern software systems, performance analysis can be a challenging task. The software stack can be a complex, multi-layer, multi-component, concurrent, and parallel environment with multiple contexts of execution and multiple sources of performance data. Although much performance data is available, because modern systems incorporate many mature data-collection mechanisms, analysis algorithms suffer from the lack of a unifying programming environment for processing the collected performance data, potentially from multiple sources, in a convenient and script-like manner. This paper presents Weir, a streaming language for systems performance analysis. Weir is based on the insight that performanceanalysis algorithms can be naturally expressed as stream-processing pipelines. In Weir, an analysis algorithm is implemented as a graph composed of stages, where each stage operates on a stream of events that represent collected performance measurements. Weir is an imperative streaming language with a syntax designed for the convenient construction of stream pipelines that utilize composable and reusable analysis stages. To demonstrate practical application, this paper presents the authors' experience in using Weir to analyze performance in systems based on the Xen virtualization platform.
{"title":"Weir: a streaming language for performance analysis","authors":"A. Burtsev, Nikhil Mishrikoti, E. Eide, R. Ricci","doi":"10.1145/2626401.2626415","DOIUrl":"https://doi.org/10.1145/2626401.2626415","url":null,"abstract":"For modern software systems, performance analysis can be a challenging task. The software stack can be a complex, multi-layer, multi-component, concurrent, and parallel environment with multiple contexts of execution and multiple sources of performance data. Although much performance data is available, because modern systems incorporate many mature data-collection mechanisms, analysis algorithms suffer from the lack of a unifying programming environment for processing the collected performance data, potentially from multiple sources, in a convenient and script-like manner.\u0000 This paper presents Weir, a streaming language for systems performance analysis. Weir is based on the insight that performanceanalysis algorithms can be naturally expressed as stream-processing pipelines. In Weir, an analysis algorithm is implemented as a graph composed of stages, where each stage operates on a stream of events that represent collected performance measurements. Weir is an imperative streaming language with a syntax designed for the convenient construction of stream pipelines that utilize composable and reusable analysis stages. To demonstrate practical application, this paper presents the authors' experience in using Weir to analyze performance in systems based on the Xen virtualization platform.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73986169","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}
G. Keller, Toby C. Murray, Sidney Amani, Liam O'Connor, Zilin Chen, L. Ryzhyk, G. Klein, G. Heiser
File systems are too important, and current ones are too buggy, to remain unverified. Yet the most successful verification methods for functional correctness remain too expensive for current file system implementations-we need verified correctness but at reasonable cost. This paper presents our vision and ongoing work to achieve this goal for a new high-performance flash file system, called BilbyFs. BilbyFs is carefully designed to be highly modular, so it can be verified against a high-level functional specification one component at a time. This modular implementation is captured in a set of domain specific languages from which we produce the design-level specification, as well as its optimised C implementation. Importantly, we also automatically generate the proof linking these two artefacts. The combination of these features dramatically reduces verification effort. Verified file systems are now within reach for the first time.
{"title":"File systems deserve verification too!","authors":"G. Keller, Toby C. Murray, Sidney Amani, Liam O'Connor, Zilin Chen, L. Ryzhyk, G. Klein, G. Heiser","doi":"10.1145/2626401.2626414","DOIUrl":"https://doi.org/10.1145/2626401.2626414","url":null,"abstract":"File systems are too important, and current ones are too buggy, to remain unverified. Yet the most successful verification methods for functional correctness remain too expensive for current file system implementations-we need verified correctness but at reasonable cost. This paper presents our vision and ongoing work to achieve this goal for a new high-performance flash file system, called BilbyFs. BilbyFs is carefully designed to be highly modular, so it can be verified against a high-level functional specification one component at a time. This modular implementation is captured in a set of domain specific languages from which we produce the design-level specification, as well as its optimised C implementation. Importantly, we also automatically generate the proof linking these two artefacts. The combination of these features dramatically reduces verification effort. Verified file systems are now within reach for the first time.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87033203","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}
Soguy Mak Karé Gueye, N. D. Palma, É. Rutten, A. Tchana
The increasing complexity of computer systems has led to the automation of administration functions, in the form of autonomic managers. One important aspect requiring such management is the issue of energy consumption of computing systems, in the perspective of green computing. As these managers address each a specific aspect, there is a need for using several managers to cover all the domains of administration. However, coordinating them is necessary for proper and effective global administration. Such coordination is a problem of synchronization and logical control of administration operations that can be applied by autonomous managers on the managed system at a given time in response to events observed on the state of this system. We therefore propose to investigate the use of reactive models with events and states, and discrete control techniques to solve this problem. In this paper, we illustrate this approach by integrating a controller obtained by synchronous programming, based on Discrete Controller Synthesis, in an autonomic system administration infrastructure. The role of this controller is to orchestrate the execution of reconfiguration operations of all administration policies to satisfy properties of logical consistency. We apply this approach to coordinate three managers : two energy-aware ones, which control server provisioning and processor frequency, and a repair manager.
{"title":"Coordinating multiple administration loops using discrete control","authors":"Soguy Mak Karé Gueye, N. D. Palma, É. Rutten, A. Tchana","doi":"10.1145/2553070.2553074","DOIUrl":"https://doi.org/10.1145/2553070.2553074","url":null,"abstract":"The increasing complexity of computer systems has led to the automation of administration functions, in the form of autonomic managers. One important aspect requiring such management is the issue of energy consumption of computing systems, in the perspective of green computing. As these managers address each a specific aspect, there is a need for using several managers to cover all the domains of administration. However, coordinating them is necessary for proper and effective global administration. Such coordination is a problem of synchronization and logical control of administration operations that can be applied by autonomous managers on the managed system at a given time in response to events observed on the state of this system. We therefore propose to investigate the use of reactive models with events and states, and discrete control techniques to solve this problem. In this paper, we illustrate this approach by integrating a controller obtained by synchronous programming, based on Discrete Controller Synthesis, in an autonomic system administration infrastructure. The role of this controller is to orchestrate the execution of reconfiguration operations of all administration policies to satisfy properties of logical consistency. We apply this approach to coordinate three managers : two energy-aware ones, which control server provisioning and processor frequency, and a repair manager.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80326699","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 recent years, energy conservation has become a major issue in information technology. Cloud computing is an emerging model for distributed utility computing and is being considered as an attractive opportunity for saving energy through central management of computational resources. Obviously, a substantial reduction in energy consumption can be made by powering down servers when they are not in use. This work presents a resources provisioning approach based on an unsupervised predictor model in the form of an unsupervised, recurrent neural network based on a self-organizing map. Another unique feature of our work is a resources administration strategy for energy saving in the cloud. Such a strategy is implemented as a selfadministration module. We show that the proposed approach gives promising results.
{"title":"An energy-efficient self-provisioning approach for cloud resources management","authors":"Hanen Chihi, Walid Chainbi, K. Ghédira","doi":"10.1145/2553070.2553072","DOIUrl":"https://doi.org/10.1145/2553070.2553072","url":null,"abstract":"In recent years, energy conservation has become a major issue in information technology. Cloud computing is an emerging model for distributed utility computing and is being considered as an attractive opportunity for saving energy through central management of computational resources. Obviously, a substantial reduction in energy consumption can be made by powering down servers when they are not in use. This work presents a resources provisioning approach based on an unsupervised predictor model in the form of an unsupervised, recurrent neural network based on a self-organizing map. Another unique feature of our work is a resources administration strategy for energy saving in the cloud. Such a strategy is implemented as a selfadministration module. We show that the proposed approach gives promising results.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85683279","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}
Dynamic voltage and frequency scaling (DVFS) is heavily used for power management in real-time environments. Although the schemes leveraging DVFS provide significant power reduction, adverse effects on chip reliability are possible. Alternate increase and decrease in operating voltage and frequency leads to thermal cycling. Increasing transistor packing density leads to a larger range of possible operating temperatures, exacerbating the thermal cycling problem. Also, the chip reliability quantification process does not include and represent the effects of small scale thermal cycles. A good number of in-field chip failures are attributed to the consequences of these. Thus, it is imperative to include their effects into the processor voltage and frequency selection process. Our work develops an integrated processor thermal and performance management technique centered on novel polynomial time scheduling algorithms that lead to lowering of thermal cycles in soft real time environments. Our technique leverages application awareness and runtime monitoring for improving chip lifetime, while achieving considerable energy savings. We show that a significant reduction in thermal cycles and peaks is possible, leading to longer chip life expectations.
{"title":"Reliability aware dynamic voltage and frequency scaling for improved microprocessor lifetime","authors":"Naga Pavan Kumar Gorti, Arun Kumar Somani","doi":"10.1145/2553070.2553073","DOIUrl":"https://doi.org/10.1145/2553070.2553073","url":null,"abstract":"Dynamic voltage and frequency scaling (DVFS) is heavily used for power management in real-time environments. Although the schemes leveraging DVFS provide significant power reduction, adverse effects on chip reliability are possible. Alternate increase and decrease in operating voltage and frequency leads to thermal cycling. Increasing transistor packing density leads to a larger range of possible operating temperatures, exacerbating the thermal cycling problem. Also, the chip reliability quantification process does not include and represent the effects of small scale thermal cycles. A good number of in-field chip failures are attributed to the consequences of these. Thus, it is imperative to include their effects into the processor voltage and frequency selection process. Our work develops an integrated processor thermal and performance management technique centered on novel polynomial time scheduling algorithms that lead to lowering of thermal cycles in soft real time environments. Our technique leverages application awareness and runtime monitoring for improving chip lifetime, while achieving considerable energy savings. We show that a significant reduction in thermal cycles and peaks is possible, leading to longer chip life expectations.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89790229","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}
Sou Koyano, S. Ata, H. Iwamoto, Yuji Yano, Y. Kuroda, K. Inoue, I. Oka
For green networking, Sliced Router Architecture was proposed, which controls the power consumption of routers by adjusting the routers' performance on the basis of the volume of traffic. In this architecture, traffic prediction is used for appropriate power control of router. For obtaining the efficient gain of power reduction, we need to consider the impact of overestimation or underestimation. In this paper, we propose a traffic prediction method by considering the impact of overestimate and underestimate on power efficiency and processing performance of Sliced Router Architecture. We evaluate our method by trace-driven simulations with real traffic, we show that our approach can control the power consumption of Sliced Router without significant performance degradation.
{"title":"A study on micro level traffic prediction for energy-aware routers","authors":"Sou Koyano, S. Ata, H. Iwamoto, Yuji Yano, Y. Kuroda, K. Inoue, I. Oka","doi":"10.1145/2553070.2553075","DOIUrl":"https://doi.org/10.1145/2553070.2553075","url":null,"abstract":"For green networking, Sliced Router Architecture was proposed, which controls the power consumption of routers by adjusting the routers' performance on the basis of the volume of traffic. In this architecture, traffic prediction is used for appropriate power control of router. For obtaining the efficient gain of power reduction, we need to consider the impact of overestimation or underestimation. In this paper, we propose a traffic prediction method by considering the impact of overestimate and underestimate on power efficiency and processing performance of Sliced Router Architecture. We evaluate our method by trace-driven simulations with real traffic, we show that our approach can control the power consumption of Sliced Router without significant performance degradation.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85159611","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}
Reducing the energy footprint of digital devices and software is a task challenging the research in Green IT. Researches have proposed approaches for energy management, ranging from reducing usage of software and hardware, compilators optimization, to server consolidation and software migration. However, optimizing the energy consumption requires knowledge of that said consumption. In particular, measuring the energy consumption of hardware and software is an important requirement for efficient energy strategies. In this review, we outline the different categories of approaches in energy measurements, and provide insights into example of each category. We draw recommendations from our review on requirements on how to efficiently measure energy consumption of devices and software.
{"title":"A review of energy measurement approaches","authors":"Adel Noureddine, Romain Rouvoy, L. Seinturier","doi":"10.1145/2553070.2553077","DOIUrl":"https://doi.org/10.1145/2553070.2553077","url":null,"abstract":"Reducing the energy footprint of digital devices and software is a task challenging the research in Green IT. Researches have proposed approaches for energy management, ranging from reducing usage of software and hardware, compilators optimization, to server consolidation and software migration. However, optimizing the energy consumption requires knowledge of that said consumption. In particular, measuring the energy consumption of hardware and software is an important requirement for efficient energy strategies. In this review, we outline the different categories of approaches in energy measurements, and provide insights into example of each category. We draw recommendations from our review on requirements on how to efficiently measure energy consumption of devices and software.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91394522","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}
Chengwei Wang, Soila Kavulya, Jiaqi Tan, Liting Hu, Mahendra Kutare, Michael P. Kasick, K. Schwan, P. Narasimhan, R. Gandhi
In the emerging cloud computing era, enterprise data centers host a plethora of web services and applications, including those for e-Commerce, distributed multimedia, and social networks, which jointly, serve many aspects of our daily lives and business. For such applications, lack of availability, reliability, or responsiveness can lead to extensive losses. For instance, on June 29 2010, Amazon.com experienced three hours of intermittent performance problems as the normally reliable website took minutes to load items, and searches came back without product links. Customers were also unable to place orders. Based on their 2010 quarterly revenues, such downtime could cost Amazon up to $1.75 million per hour, thus making rapid problem resolution critical to its business. In another serious incident, on July 7, 2010, DBS bank in Singapore suffered a 7-hour outage which crippled its Internet banking systems, and disrupted other consumer banking services, including automated teller machines, credit card and NETS payments. The cascading failure occurred due to a procedural error while replacing a faulty component in one of the bank’s storage systems that was connected to its main computers. The high-cost of downtime in large-scale distributed systems drives the need for troubleshooting tools that can quickly detect problems and point system administrators to potential solutions. The increasing size and complexity of enterprise applications, coupled with the large scale of data centers in which they operate, make troubleshooting extremely challenging. Problems can arise due to a large variety of root-causes because of the complex interactions between hardware and software systems. The large volume of monitoring data available in these systems can obscure the root-cause of these problems. Lastly, the multi-tier nature of applications composed of entirely different subsystems man-
{"title":"Performance troubleshooting in data centers: an annotated bibliography?","authors":"Chengwei Wang, Soila Kavulya, Jiaqi Tan, Liting Hu, Mahendra Kutare, Michael P. Kasick, K. Schwan, P. Narasimhan, R. Gandhi","doi":"10.1145/2553070.2553079","DOIUrl":"https://doi.org/10.1145/2553070.2553079","url":null,"abstract":"In the emerging cloud computing era, enterprise data centers host a plethora of web services and applications, including those for e-Commerce, distributed multimedia, and social networks, which jointly, serve many aspects of our daily lives and business. For such applications, lack of availability, reliability, or responsiveness can lead to extensive losses. For instance, on June 29 2010, Amazon.com experienced three hours of intermittent performance problems as the normally reliable website took minutes to load items, and searches came back without product links. Customers were also unable to place orders. Based on their 2010 quarterly revenues, such downtime could cost Amazon up to $1.75 million per hour, thus making rapid problem resolution critical to its business. In another serious incident, on July 7, 2010, DBS bank in Singapore suffered a 7-hour outage which crippled its Internet banking systems, and disrupted other consumer banking services, including automated teller machines, credit card and NETS payments. The cascading failure occurred due to a procedural error while replacing a faulty component in one of the bank’s storage systems that was connected to its main computers. The high-cost of downtime in large-scale distributed systems drives the need for troubleshooting tools that can quickly detect problems and point system administrators to potential solutions. The increasing size and complexity of enterprise applications, coupled with the large scale of data centers in which they operate, make troubleshooting extremely challenging. Problems can arise due to a large variety of root-causes because of the complex interactions between hardware and software systems. The large volume of monitoring data available in these systems can obscure the root-cause of these problems. Lastly, the multi-tier nature of applications composed of entirely different subsystems man-","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87690457","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}
Building server software in a large-scale setting, where systems exhibit a high degree of concurrency and environmental variability, is a challenging task to even the most experienced programmer. Efficiency, safety, and robustness are paramount---goals which have traditionally conflicted with modularity, reusability, and flexibility. We describe three abstractions which combine to present a powerful programming model for building safe, modular, and efficient server software: Composable futures are used to relate concurrent, asynchronous actions; services and filters are specialized functions used for the modular composition of our complex server software. Finally, we discuss our experiences using these abstractions and techniques throughout Twitter's serving infrastructure.
{"title":"Your server as a function","authors":"Marius Eriksen","doi":"10.1145/2525528.2525538","DOIUrl":"https://doi.org/10.1145/2525528.2525538","url":null,"abstract":"Building server software in a large-scale setting, where systems exhibit a high degree of concurrency and environmental variability, is a challenging task to even the most experienced programmer. Efficiency, safety, and robustness are paramount---goals which have traditionally conflicted with modularity, reusability, and flexibility.\u0000 We describe three abstractions which combine to present a powerful programming model for building safe, modular, and efficient server software: Composable futures are used to relate concurrent, asynchronous actions; services and filters are specialized functions used for the modular composition of our complex server software.\u0000 Finally, we discuss our experiences using these abstractions and techniques throughout Twitter's serving infrastructure.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82641877","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}
S. Bouchenak, G. Chockler, Hana Chockler, Gabriela Gheorghe, Nuno Santos, A. Shraer
As cloud-based services gain popularity in both private and enterprise domains, cloud consumers are still lacking in tools to verify that these services work as expected. Such tools should consider properties such as functional correctness, service availability, reliability, performance and security guarantees. In this paper we survey existing work in these areas and identify gaps in existing cloud technology in terms of the verification tools provided to users. We also discuss challenges and new research directions that can help bridge these gaps.
{"title":"Verifying cloud services: present and future","authors":"S. Bouchenak, G. Chockler, Hana Chockler, Gabriela Gheorghe, Nuno Santos, A. Shraer","doi":"10.1145/2506164.2506167","DOIUrl":"https://doi.org/10.1145/2506164.2506167","url":null,"abstract":"As cloud-based services gain popularity in both private and enterprise domains, cloud consumers are still lacking in tools to verify that these services work as expected. Such tools should consider properties such as functional correctness, service availability, reliability, performance and security guarantees. In this paper we survey existing work in these areas and identify gaps in existing cloud technology in terms of the verification tools provided to users. We also discuss challenges and new research directions that can help bridge these gaps.","PeriodicalId":7046,"journal":{"name":"ACM SIGOPS Oper. Syst. Rev.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72664617","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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