In designing information communication devices such as real-time embedded systems, it is quite important to maximize the system performance under some hard energy constraints. As a useful technology to reduce the energy consumption in computer-based systems, the dynamic voltage and frequency scaling (DVFS) is becoming very popular. In this paper, we consider an optimal DVFS allocation problem by maximizing the system reliability subject to the hard real-time and energy constraints. More specifically, we formulate a reliability maximization problem when the task processing is probabilistic and is described by a discrete-time Markov chain. Two approximate formulas are proposed to calculate the system reliability efficiently. We perform the sensitivity analysis of model parameters in numerical examples, and also give a case study to design a Wi-Fi subsystem in terms of the DVFS allocation.
{"title":"Optimal Reliability Design for Real-Time Systems with Dynamic Voltage and Frequency Scaling","authors":"Toshitaka Koga, T. Dohi, H. Okamura","doi":"10.1109/PRDC.2014.35","DOIUrl":"https://doi.org/10.1109/PRDC.2014.35","url":null,"abstract":"In designing information communication devices such as real-time embedded systems, it is quite important to maximize the system performance under some hard energy constraints. As a useful technology to reduce the energy consumption in computer-based systems, the dynamic voltage and frequency scaling (DVFS) is becoming very popular. In this paper, we consider an optimal DVFS allocation problem by maximizing the system reliability subject to the hard real-time and energy constraints. More specifically, we formulate a reliability maximization problem when the task processing is probabilistic and is described by a discrete-time Markov chain. Two approximate formulas are proposed to calculate the system reliability efficiently. We perform the sensitivity analysis of model parameters in numerical examples, and also give a case study to design a Wi-Fi subsystem in terms of the DVFS allocation.","PeriodicalId":187000,"journal":{"name":"2014 IEEE 20th Pacific Rim International Symposium on Dependable Computing","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129951678","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}
We present a new class of fault-tolerant distributed algorithms based on a concept which we call region adherence. A region-adherent algorithm upper-bounds the violation of safety due to faults in space. Region adherence counter-poses the concept of self-stabilization which upper-bounds a violation of safety in time. It turns out that region adherence is an orthogonal concept to self-stabilization. We give a formal definition of region-adherence that, intuitively, upper-bounds the reduction of the algorithm's service quality per fault. Then, we present a sample algorithm that exhibits region-adherent behavior and prove this property formally. Finally, we analyze the service quality of the sample algorithm via simulation and compare it to the worst-case behavior stated by the region adherence property.
{"title":"Region-Adherent Algorithms: Restricting the Impact of Faults on Service Quality","authors":"J. Becker, D. Rahmatov, Oliver E. Theel","doi":"10.1109/PRDC.2014.34","DOIUrl":"https://doi.org/10.1109/PRDC.2014.34","url":null,"abstract":"We present a new class of fault-tolerant distributed algorithms based on a concept which we call region adherence. A region-adherent algorithm upper-bounds the violation of safety due to faults in space. Region adherence counter-poses the concept of self-stabilization which upper-bounds a violation of safety in time. It turns out that region adherence is an orthogonal concept to self-stabilization. We give a formal definition of region-adherence that, intuitively, upper-bounds the reduction of the algorithm's service quality per fault. Then, we present a sample algorithm that exhibits region-adherent behavior and prove this property formally. Finally, we analyze the service quality of the sample algorithm via simulation and compare it to the worst-case behavior stated by the region adherence property.","PeriodicalId":187000,"journal":{"name":"2014 IEEE 20th Pacific Rim International Symposium on Dependable Computing","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115585855","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}
One of the main issues in Solid State Drive (SSD)-based storage systems is endurance which is directly affected by the number of Program/Erase (P/E) cycles. The increment of P/E cycles increases the bit error rate threatening the reliability of SSDs. Erasure codes are used to leverage the reliability of storage systems but they also affect the number of P/E cycles based on their code pattern. A lower dependency between data and parities in the code pattern may lead to smaller number of P/E cycles providing better endurance. This paper introduces an Endurance Aware EVENODD (EA-EO), which minimizes the dependency between data and parities in the coding pattern. A simulation environment is used to compare the write-cycles of EA-EO with EVENODD in terms of different request size. The results show that the endurance improvement of EA-EO code could be as high as 44%. Furthermore, performance analysis of these codes in terms of parity construction and failure recovery shows that the number of XOR-operations is reduced in EA-EO compared to EVENODD.
{"title":"EA-EO: Endurance Aware Erasure Code for SSD-Based Storage Systems","authors":"Saeideh Alinezhad Chamazcoti, S. Miremadi","doi":"10.1109/PRDC.2014.18","DOIUrl":"https://doi.org/10.1109/PRDC.2014.18","url":null,"abstract":"One of the main issues in Solid State Drive (SSD)-based storage systems is endurance which is directly affected by the number of Program/Erase (P/E) cycles. The increment of P/E cycles increases the bit error rate threatening the reliability of SSDs. Erasure codes are used to leverage the reliability of storage systems but they also affect the number of P/E cycles based on their code pattern. A lower dependency between data and parities in the code pattern may lead to smaller number of P/E cycles providing better endurance. This paper introduces an Endurance Aware EVENODD (EA-EO), which minimizes the dependency between data and parities in the coding pattern. A simulation environment is used to compare the write-cycles of EA-EO with EVENODD in terms of different request size. The results show that the endurance improvement of EA-EO code could be as high as 44%. Furthermore, performance analysis of these codes in terms of parity construction and failure recovery shows that the number of XOR-operations is reduced in EA-EO compared to EVENODD.","PeriodicalId":187000,"journal":{"name":"2014 IEEE 20th Pacific Rim International Symposium on Dependable Computing","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126310951","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 article discusses the location of faulty interactions in software testing. We propose an algorithm to generate a test suite that can be used to identify a faulty pair-wise interaction. This approach works as follows. First, a test suite is generated using an existing method for pair-wise testing. Pair-wise testing requires testing all pair-wise interactions but does not guarantee that the faulty interaction can be located. Second, pair-wise interactions that cannot be located by the test suite are enumerated. Finally, test cases are repeatedly added to the test suite until all pair-wise interactions can be located. The results of applying the algorithm to several problem instances show that the test suites obtained using the algorithm are nearly twice as large as those for ordinary pair-wise testing which does not ensure fault locating ability.
{"title":"Locating a Faulty Interaction in Pair-wise Testing","authors":"Takahiro Nagamoto, Hideharu Kojima, Hiroyuki Nakagawa, Tatsuhiro Tsuchiya","doi":"10.1109/PRDC.2014.26","DOIUrl":"https://doi.org/10.1109/PRDC.2014.26","url":null,"abstract":"This article discusses the location of faulty interactions in software testing. We propose an algorithm to generate a test suite that can be used to identify a faulty pair-wise interaction. This approach works as follows. First, a test suite is generated using an existing method for pair-wise testing. Pair-wise testing requires testing all pair-wise interactions but does not guarantee that the faulty interaction can be located. Second, pair-wise interactions that cannot be located by the test suite are enumerated. Finally, test cases are repeatedly added to the test suite until all pair-wise interactions can be located. The results of applying the algorithm to several problem instances show that the test suites obtained using the algorithm are nearly twice as large as those for ordinary pair-wise testing which does not ensure fault locating ability.","PeriodicalId":187000,"journal":{"name":"2014 IEEE 20th Pacific Rim International Symposium on Dependable Computing","volume":"PP 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126356174","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}
Jehan-Francois Pâris, T. Schwarz, A. Amer, D. Long
Disk failure rates vary so widely among different makes and models that designing storage solutions for the worst case scenario is a losing proposition. The approach we propose here is to design our storage solutions for the most probable case while incorporating in our design the option of adding extra redundancy when we find out that its disks are less reliable than expected. To illustrate our proposal, we show how to increase the reliability of existing two-dimensional disk arrays with n2 data elements and 2n parity elements by adding n additional parity elements that will mirror the contents of half the existing parity elements. Our approach offers the three advantages of being easy to deploy, not affecting the complexity of parity calculations, and providing a five-year reliability of 99.999 percent in the face of catastrophic levels of data loss where the array would lose up to a quarter of its storage capacity in a year.
{"title":"Protecting RAID Arrays against Unexpectedly High Disk Failure Rates","authors":"Jehan-Francois Pâris, T. Schwarz, A. Amer, D. Long","doi":"10.1109/PRDC.2014.17","DOIUrl":"https://doi.org/10.1109/PRDC.2014.17","url":null,"abstract":"Disk failure rates vary so widely among different makes and models that designing storage solutions for the worst case scenario is a losing proposition. The approach we propose here is to design our storage solutions for the most probable case while incorporating in our design the option of adding extra redundancy when we find out that its disks are less reliable than expected. To illustrate our proposal, we show how to increase the reliability of existing two-dimensional disk arrays with n2 data elements and 2n parity elements by adding n additional parity elements that will mirror the contents of half the existing parity elements. Our approach offers the three advantages of being easy to deploy, not affecting the complexity of parity calculations, and providing a five-year reliability of 99.999 percent in the face of catastrophic levels of data loss where the array would lose up to a quarter of its storage capacity in a year.","PeriodicalId":187000,"journal":{"name":"2014 IEEE 20th Pacific Rim International Symposium on Dependable Computing","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131851092","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}
Ludovic Pintard, J. Fabre, Michel Leeman, K. Kanoun, Matthieu Roy
Automotive embedded systems are becoming increasingly complex. Therefore verification activities are paramount to ensure safety. ISO 26262 is the first standard specifically dedicated to automotive safety systems. This standard requires introducing fault injection (FI) from the very early phases of the development process. Our work aims at developing an approach that will help integrate FI in the whole development process in a continuous way, from system requirements to the verification and validation phase. In this paper, we concentrate on exploring the benefits of safety analyses for experimental validation of the system. We propose an analogy between FI during the pre-implementation phase with safety analyses that are of common use during system design. We finally illustrate this approach on a case study from the automotive domain.
{"title":"From Safety Analyses to Experimental Validation of Automotive Embedded Systems","authors":"Ludovic Pintard, J. Fabre, Michel Leeman, K. Kanoun, Matthieu Roy","doi":"10.1109/PRDC.2014.23","DOIUrl":"https://doi.org/10.1109/PRDC.2014.23","url":null,"abstract":"Automotive embedded systems are becoming increasingly complex. Therefore verification activities are paramount to ensure safety. ISO 26262 is the first standard specifically dedicated to automotive safety systems. This standard requires introducing fault injection (FI) from the very early phases of the development process. Our work aims at developing an approach that will help integrate FI in the whole development process in a continuous way, from system requirements to the verification and validation phase. In this paper, we concentrate on exploring the benefits of safety analyses for experimental validation of the system. We propose an analogy between FI during the pre-implementation phase with safety analyses that are of common use during system design. We finally illustrate this approach on a case study from the automotive domain.","PeriodicalId":187000,"journal":{"name":"2014 IEEE 20th Pacific Rim International Symposium on Dependable Computing","volume":"134 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131052687","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 firewall is a crucial security element in modern computer networks. This work investigates and demonstrates the implementation of a lightweight TCP/IP firewall in a bare-metal environment, on a commercial embedded ARM device. Compared to an implementation having an operating system (OS), using bare-metal design enables reduction of exposure to potential vulnerabilities in OS code, and provides a more dependable system. The implemented firewall provides both static and stateful filtering capabilities, and is configurable in a user-friendly way. As the architecture of the commercial hardware used was not available under closed source licensing, it was discovered through analysis at both hardware and software levels. Some challenges were encountered, and tools were developed to address these. The prototype is validated through functional testing in a controlled environment successfully.
{"title":"Lightweight Bare-Metal Stateful Firewall","authors":"Yihuan Xing, Ford-Long Wong, Akash Kumar","doi":"10.1109/PRDC.2014.15","DOIUrl":"https://doi.org/10.1109/PRDC.2014.15","url":null,"abstract":"A firewall is a crucial security element in modern computer networks. This work investigates and demonstrates the implementation of a lightweight TCP/IP firewall in a bare-metal environment, on a commercial embedded ARM device. Compared to an implementation having an operating system (OS), using bare-metal design enables reduction of exposure to potential vulnerabilities in OS code, and provides a more dependable system. The implemented firewall provides both static and stateful filtering capabilities, and is configurable in a user-friendly way. As the architecture of the commercial hardware used was not available under closed source licensing, it was discovered through analysis at both hardware and software levels. Some challenges were encountered, and tools were developed to address these. The prototype is validated through functional testing in a controlled environment successfully.","PeriodicalId":187000,"journal":{"name":"2014 IEEE 20th Pacific Rim International Symposium on Dependable Computing","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124959578","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}
Cloud computing is increasingly important, with the industry moving towards outsourcing computational resources as a means to reduce investment and management costs, while improving security, dependability and performance. Cloud operators use multi-tenancy, by grouping virtual machines (VMs) into a few physical machines (PMs), to pool computing resources, thus offering elasticity to clients. Although cloud-based fault tolerance schemes impose communication and synchronization overheads, the cloud offers excellent facilities for critical applications, as it can host varying numbers of replicas in independent resources. Given these contradictory forces, determining whether the cloud can host elastic critical services is a major research question. We address this challenge from the perspective of a standard three-tiered system with relational data. We propose to tolerate Byzantine faults using groups of replicas placed on distinct physical machines, as a means to avoid exposing applications to correlated failures. To improve the scalability of our system, we divide data to enable parallel accesses. Using a realistic setup, this setting can reach speedups largely exceeding the number of partitions. Even for a wide variation of the load, the system preserves latency and throughput within reasonable bounds. We believe that the elasticity we observe demonstrates the feasibility of tolerating Byzantine faults in a cloud-based server using a relational database.
{"title":"CloudBFT: Elastic Byzantine Fault Tolerance","authors":"Rodrigo Nogueira, Filipe Araújo, R. Barbosa","doi":"10.1109/PRDC.2014.31","DOIUrl":"https://doi.org/10.1109/PRDC.2014.31","url":null,"abstract":"Cloud computing is increasingly important, with the industry moving towards outsourcing computational resources as a means to reduce investment and management costs, while improving security, dependability and performance. Cloud operators use multi-tenancy, by grouping virtual machines (VMs) into a few physical machines (PMs), to pool computing resources, thus offering elasticity to clients. Although cloud-based fault tolerance schemes impose communication and synchronization overheads, the cloud offers excellent facilities for critical applications, as it can host varying numbers of replicas in independent resources. Given these contradictory forces, determining whether the cloud can host elastic critical services is a major research question. We address this challenge from the perspective of a standard three-tiered system with relational data. We propose to tolerate Byzantine faults using groups of replicas placed on distinct physical machines, as a means to avoid exposing applications to correlated failures. To improve the scalability of our system, we divide data to enable parallel accesses. Using a realistic setup, this setting can reach speedups largely exceeding the number of partitions. Even for a wide variation of the load, the system preserves latency and throughput within reasonable bounds. We believe that the elasticity we observe demonstrates the feasibility of tolerating Byzantine faults in a cloud-based server using a relational database.","PeriodicalId":187000,"journal":{"name":"2014 IEEE 20th Pacific Rim International Symposium on Dependable Computing","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116859175","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 study we discuss fault tolerant routing mechanism for the P2P network, Chord, considering the existence of faulty or malicious nodes. We propose a routing protocol which works despite existence of faulty nodes. We modify the original Chord routing protocol so that it can handle redundant lookups of multiple "knuckles," and replica or data fragments allocation on knuckles. Analysis based on mathematical models and simulations show that the proposed protocol effectively avoids the interruption of object supply caused by the target node fault and/or the acquisition failure of objects caused by malicious nodes tampering.
{"title":"Study on Routing Protocol for Structured P2P Network Taking Account of the Nodes Which Behave Like a Byzantine Fault","authors":"S. Fukumoto, Tomoki Endo, Mamoru Ohara, M. Arai","doi":"10.1109/PRDC.2014.12","DOIUrl":"https://doi.org/10.1109/PRDC.2014.12","url":null,"abstract":"In this study we discuss fault tolerant routing mechanism for the P2P network, Chord, considering the existence of faulty or malicious nodes. We propose a routing protocol which works despite existence of faulty nodes. We modify the original Chord routing protocol so that it can handle redundant lookups of multiple \"knuckles,\" and replica or data fragments allocation on knuckles. Analysis based on mathematical models and simulations show that the proposed protocol effectively avoids the interruption of object supply caused by the target node fault and/or the acquisition failure of objects caused by malicious nodes tampering.","PeriodicalId":187000,"journal":{"name":"2014 IEEE 20th Pacific Rim International Symposium on Dependable Computing","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125559813","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}
Fault-tolerance is vital for dependable distributed applications that can deliver service, even in the presence of faults. Over the last few decades, above all protocols proposed to offer reliability and fault-tolerance, TCP grew to become one of the cornerstones of the Internet. However, despite emulating reliable communication in distributed environments, TCP does not handle connection failures when the connectivity is lost for some time, even if both endpoints are still running. When this occurs, developers must rollback the peers to some coherent state, many times with error-prone, ad hoc, or custom application-level solutions. In this paper, we refine the Acceptor-Connector design pattern to tackle the TCP unreliability problem. The pattern decouples the failure-related processing from the connection and service processing, efficiently handling different connections and their possible crashes concurrently, thereby yielding more reusable, extensible, and efficient distributed communication. The solution we propose incorporates proven multi-threaded solutions and a buffering scheme that discards the need for an application-layer acknowledgment scheme. This simplifies the development of reliable connection-oriented applications using the ubiquitous TCP protocol.
{"title":"Design of Multi-threaded Fault-Tolerant Connection-Oriented Communication","authors":"N. Ivaki, Filipe Araújo, F. Barros","doi":"10.1109/PRDC.2014.10","DOIUrl":"https://doi.org/10.1109/PRDC.2014.10","url":null,"abstract":"Fault-tolerance is vital for dependable distributed applications that can deliver service, even in the presence of faults. Over the last few decades, above all protocols proposed to offer reliability and fault-tolerance, TCP grew to become one of the cornerstones of the Internet. However, despite emulating reliable communication in distributed environments, TCP does not handle connection failures when the connectivity is lost for some time, even if both endpoints are still running. When this occurs, developers must rollback the peers to some coherent state, many times with error-prone, ad hoc, or custom application-level solutions. In this paper, we refine the Acceptor-Connector design pattern to tackle the TCP unreliability problem. The pattern decouples the failure-related processing from the connection and service processing, efficiently handling different connections and their possible crashes concurrently, thereby yielding more reusable, extensible, and efficient distributed communication. The solution we propose incorporates proven multi-threaded solutions and a buffering scheme that discards the need for an application-layer acknowledgment scheme. This simplifies the development of reliable connection-oriented applications using the ubiquitous TCP protocol.","PeriodicalId":187000,"journal":{"name":"2014 IEEE 20th Pacific Rim International Symposium on Dependable Computing","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127914833","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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