International Conference on Virtual Execution Environments最新文献_第10页

Multi-stage replay with crosscut 多阶段回放与横切

International Conference on Virtual Execution Environments Pub Date : 2010-03-17 DOI: 10.1145/1735997.1736002

Jim Chow, Dominic G. Lucchetti, Tal Garfinkel, Geoffrey Lefebvre, Ryan W. Gardner, Joshua Mason, Sam Small, Peter M. Chen

{"title":"Multi-stage replay with crosscut","authors":"Jim Chow, Dominic G. Lucchetti, Tal Garfinkel, Geoffrey Lefebvre, Ryan W. Gardner, Joshua Mason, Sam Small, Peter M. Chen","doi":"10.1145/1735997.1736002","DOIUrl":"https://doi.org/10.1145/1735997.1736002","url":null,"abstract":"Deterministic record-replay has many useful applications, ranging from fault tolerance and forensics to reproducing and diagnosing bugs. When choosing a record-replay solution, the system administrator must choose a priori how comprehensively to record the execution and at what abstraction level to record it. Unfortunately, these choices may not match well with how the recording is eventually used. A recording may contain too little information to support the end use of replay, or it may contain more sensitive information than is allowed to be shown to the end user of replay. Similarly, fixing the abstraction level at the time of recording often leads to a semantic mismatch with the end use of replay.\u0000 This paper describes how to remedy these problems by adding customizable replay stages to create special-purpose logs for the end users of replay. Our system, called Crosscut, allows replay logs to be \"sliced\" along time and abstraction boundaries. Using this approach, users can create slices that include only the processes, applications, or components of interest, excluding parts that handle sensitive data. Users can also retarget the abstraction level of the replay log to higher-level platforms, such as Perl or Valgrind. Execution can then be augmented with additional analysis code at replay time, without disturbing the replayed components in the slice. Crosscut thus uses replay itself to transform logs into a more efficient, secure, and usable form for replay-based applications.\u0000 Our current Crosscut prototype builds on VMware Workstation's record-replay capabilities, and supports a variety of different replay environments. We show how Crosscut can create slices of only the parts of the computation of interest and thereby avoid leaking sensitive information, and we show how to retarget the abstraction level of the log to enable more convenient use during replay debugging.","PeriodicalId":202844,"journal":{"name":"International Conference on Virtual Execution Environments","volume":"40 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116726588","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}

引用次数: 35

ClientVisor: leverage COTS OS functionalities for power management in virtualized desktop environment ClientVisor:利用COTS OS功能在虚拟化桌面环境中进行电源管理

International Conference on Virtual Execution Environments Pub Date : 2009-03-11 DOI: 10.1145/1508293.1508312

Huacai Chen, Hai Jin, Zhiyuan Shao, K. Yu, Kun Tian

{"title":"ClientVisor: leverage COTS OS functionalities for power management in virtualized desktop environment","authors":"Huacai Chen, Hai Jin, Zhiyuan Shao, K. Yu, Kun Tian","doi":"10.1145/1508293.1508312","DOIUrl":"https://doi.org/10.1145/1508293.1508312","url":null,"abstract":"As an emerging trend, virtualization is more and more widely used in today's computing world. But, the introduc-tion of virtual machines bring trouble for the power man-agement (PM for short), since the operating system can not directly access and control the hardware as before. Solu-tions were proposed to manage the power in the server con-solidation case. However, such solutions are VMM-centric: the VMM gathers the PM decisions of the guests as hints, and makes the final decision to manipulate the hardware. These solutions do not fit well for the virtualized desktop environment, which is highly interactive with the users.\u0000 In this paper, we propose a novel solution, called Cli-entVisor, to manage the power in the virtualized desktop environment. The key idea of our scheme is to leverage the functionalities of the Commercial-Off-The-Shelf (COTS) operating system, which actually interacts with the user, to manage the power of the processor and the peripheral de-vices in all possible cases. VMM coordinates the PM deci-sions of the guests only at the key points. By prototype implementation and experiments, we find our scheme re-sults in 22% lower power consumption in the static power usage scenario, and about 8% lower in the dynamic sce-nario than the corresponding cases of Xen. Moreover, the experimental data shows that the deployment of our scheme will not deteriorate the user experience.","PeriodicalId":202844,"journal":{"name":"International Conference on Virtual Execution Environments","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133528133","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}

引用次数: 10

Memory buddies: exploiting page sharing for smart colocation in virtualized data centers 内存伙伴:在虚拟化数据中心中利用页面共享实现智能主机托管

International Conference on Virtual Execution Environments Pub Date : 2009-03-11 DOI: 10.1145/1508293.1508299

Timothy Wood, Gabriel Tarasuk-Levin, P. Shenoy, Peter Desnoyers, E. Cecchet, M. Corner

{"title":"Memory buddies: exploiting page sharing for smart colocation in virtualized data centers","authors":"Timothy Wood, Gabriel Tarasuk-Levin, P. Shenoy, Peter Desnoyers, E. Cecchet, M. Corner","doi":"10.1145/1508293.1508299","DOIUrl":"https://doi.org/10.1145/1508293.1508299","url":null,"abstract":"Many data center virtualization solutions, such as VMware ESX, employ content-based page sharing to consolidate the resources of multiple servers. Page sharing identifies virtual machine memory pages with identical content and consolidates them into a single shared page. This technique, implemented at the host level, applies only between VMs placed on a given physical host. In a multi-server data center, opportunities for sharing may be lost because the VMs holding identical pages are resident on different hosts. In order to obtain the full benefit of content-based page sharing it is necessary to place virtual machines such that VMs with similar memory content are located on the same hosts.\u0000 In this paper we present Memory Buddies, a memory sharing-aware placement system for virtual machines. This system includes a memory fingerprinting system to efficiently determine the sharing potential among a set of VMs, and compute more efficient placements. In addition it makes use of live migration to optimize VM placement as workloads change. We have implemented a prototype Memory Buddies system with VMware ESX Server and present experimental results on our testbed, as well as an analysis of an extensive memory trace study. Evaluation of our prototype using a mix of enterprise and e-commerce applications demonstrates an increase of data center capacity (i.e. number of VMs supported) of 17%, while imposing low overhead and scaling to as many as a thousand servers.","PeriodicalId":202844,"journal":{"name":"International Conference on Virtual Execution Environments","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126148686","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}

引用次数: 203

BitVisor: a thin hypervisor for enforcing i/o device security BitVisor:用于加强i/o设备安全性的瘦管理程序

International Conference on Virtual Execution Environments Pub Date : 2009-03-11 DOI: 10.1145/1508293.1508311

Takahiro Shinagawa, H. Eiraku, Kouichi Tanimoto, Kazumasa Omote, Shoichi Hasegawa, Takashi Horie, Manabu Hirano, Kenichi Kourai, Y. Oyama, Eiji Kawai, K. Kono, S. Chiba, Yasushi Shinjo, Kazuhiko Kato

{"title":"BitVisor: a thin hypervisor for enforcing i/o device security","authors":"Takahiro Shinagawa, H. Eiraku, Kouichi Tanimoto, Kazumasa Omote, Shoichi Hasegawa, Takashi Horie, Manabu Hirano, Kenichi Kourai, Y. Oyama, Eiji Kawai, K. Kono, S. Chiba, Yasushi Shinjo, Kazuhiko Kato","doi":"10.1145/1508293.1508311","DOIUrl":"https://doi.org/10.1145/1508293.1508311","url":null,"abstract":"Virtual machine monitors (VMMs), including hypervisors, are a popular platform for implementing various security functionalities. However, traditional VMMs require numerous components for providing virtual hardware devices and for sharing and protecting system resources among virtual machines (VMs), enlarging the code size of and reducing the reliability of the VMMs.\u0000 This paper introduces a hypervisor architecture, called parapass-through, designed to minimize the code size of hypervisors by allowing most of the I/O access from the guest operating system (OS) to pass-through the hypervisor, while the minimum access necessary to implement security functionalities is completely mediated by the hypervisor. This architecture uses device drivers of the guest OS to handle devices, thereby reducing the size of components in the hypervisor to provide virtual devices. This architecture also allows to run only single VM on it, eliminating the components for sharing and protecting system resources among VMs.\u0000 We implemented a hypervisor called BitVisor and a parapass-through driver for enforcing storage encryption of ATA devices based on the parapass-through architecture. The experimental result reveals that the hypervisor and ATA driver require approximately 20 kilo lines of code (KLOC) and 1.4 KLOC respectively.","PeriodicalId":202844,"journal":{"name":"International Conference on Virtual Execution Environments","volume":"210 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115766872","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}

引用次数: 197

Achieving 10 Gb/s using safe and transparent network interface virtualization 通过安全透明的网络接口虚拟化实现10gb /s

International Conference on Virtual Execution Environments Pub Date : 2009-03-11 DOI: 10.1145/1508293.1508303

K. Ram, J. R. Santos, Yoshio Turner, A. Cox, S. Rixner

{"title":"Achieving 10 Gb/s using safe and transparent network interface virtualization","authors":"K. Ram, J. R. Santos, Yoshio Turner, A. Cox, S. Rixner","doi":"10.1145/1508293.1508303","DOIUrl":"https://doi.org/10.1145/1508293.1508303","url":null,"abstract":"This paper presents mechanisms and optimizations to reduce the overhead of network interface virtualization when using the driver domain I/O virtualization model. The driver domain model provides benefits such as support for legacy device drivers and fault isolation. However, the processing overheads incurred in the driver domain to achieve these benefits limit overall I/O performance. This paper demonstrates the effectiveness of two approaches to reduce driver domain overheads. First, Xen is modified to support multi-queue network interfaces to eliminate the software overheads of packet demultiplexing and copying. Second, a grant reuse mechanism is developed to reduce memory protection overheads. These mechanisms shift the bottleneck from the driver domain to the guest domains, improving scalability and enabling significantly higher data rates. This paper also presents and evaluates a series of optimizations that substantially reduce the I/O virtualization overheads in the guest domain. In combination, these mechanisms and optimizations increase the maximum throughput achieved by guest domains from 2.9Gb/s to full 10 Gigabit Ethernet link rates.","PeriodicalId":202844,"journal":{"name":"International Conference on Virtual Execution Environments","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127625487","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}

引用次数: 123

A lock-free, concurrent, and incremental stack scanning for garbage collectors 垃圾收集器的无锁、并发和增量堆栈扫描

International Conference on Virtual Execution Environments Pub Date : 2009-03-11 DOI: 10.1145/1508293.1508296

G. Kliot, E. Petrank, B. Steensgaard

{"title":"A lock-free, concurrent, and incremental stack scanning for garbage collectors","authors":"G. Kliot, E. Petrank, B. Steensgaard","doi":"10.1145/1508293.1508296","DOIUrl":"https://doi.org/10.1145/1508293.1508296","url":null,"abstract":"Two major efficiency parameters for garbage collectors are the throughput overheads and the pause times that they introduce. Highly responsive systems need to use collectors with as short as possible pause times. Pause lengths have decreased significantly during the years, especially through the use of concurrent garbage collectors. For modern concurrent collectors, the longest pause is typically created by the need to atomically scan the runtime stack. All practical concurrent collectors that we are aware of must obtain a snapshot of the pointers on each thread's runtime stack, in order to reclaim objects correctly. To further reduce the length of the collector pauses, incremental stack scans were proposed. However, previous such methods employ locks to stop the mutator from accessing a stack frame while it is being scanned. Thus, these methods introduce a potential long and unpredictable pauses for a mutator thread. In this work we propose the first concurrent, incremental, and lock-free stack scanning for garbage collectors, allowing high responsiveness and support for programs that employ fine-synchronization to avoid locks. Our solution can be employed by all concurrent collectors that we are aware of, it is lock-free, it imposes a negligible overhead on the program execution, and it supports the special in-stack references existing in languages like C#.","PeriodicalId":202844,"journal":{"name":"International Conference on Virtual Execution Environments","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129640169","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}

引用次数: 13

The hybrid scheduling framework for virtual machine systems 虚拟机系统的混合调度框架

International Conference on Virtual Execution Environments Pub Date : 2009-03-11 DOI: 10.1145/1508293.1508309

Chuliang Weng, Zhigang Wang, Minglu Li, Xinda Lu

{"title":"The hybrid scheduling framework for virtual machine systems","authors":"Chuliang Weng, Zhigang Wang, Minglu Li, Xinda Lu","doi":"10.1145/1508293.1508309","DOIUrl":"https://doi.org/10.1145/1508293.1508309","url":null,"abstract":"The virtualization technology makes it feasible that multiple guest operating systems run on a single physical machine. It is the virtual machine monitor that dynamically maps the virtual CPU of virtual machines to physical CPUs according to the scheduling strategy. The scheduling strategy in Xen schedules virtual CPUs of a virtual machines asynchronously while guarantees the proportion of the CPU time corresponding to its weight, maximizing the throughput of the system. However, this scheduling strategy may deteriorate the performance when the virtual machine is used to execute the concurrent applications such as parallel programs or multithreaded programs. In this paper, we analyze the CPU scheduling problem in the virtual machine monitor theoretically, and the result is that the asynchronous CPU scheduling strategy will waste considerable physical CPU time when the system workload is the concurrent application. Then, we present a hybrid scheduling framework for the CPU scheduling in the virtual machine monitor. There are two types of virtual machines in the system: the high-throughput type and the concurrent type. The virtual machine can be set as the concurrent type when the majority of its workload is concurrent applications in order to reduce the cost of synchronization. Otherwise, it is set as the high-throughput type as the default. Moreover, we implement the hybrid scheduling framework based on Xen, and we will give a description of our implementation in details. At last, we test the performance of the presented scheduling framework and strategy based on the multi-core platform, and the experiment result indicates that the scheduling framework and strategy is feasible to improve the performance of the virtual machine system.","PeriodicalId":202844,"journal":{"name":"International Conference on Virtual Execution Environments","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131327171","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}

引用次数: 104

Demystifying magic: high-level low-level programming 揭秘魔法:高级低级编程

International Conference on Virtual Execution Environments Pub Date : 2009-03-11 DOI: 10.1145/1508293.1508305

Daniel Frampton, S. Blackburn, P. Cheng, Robin Garner, D. Grove, J. E. B. Moss, Sergey I. Salishev

{"title":"Demystifying magic: high-level low-level programming","authors":"Daniel Frampton, S. Blackburn, P. Cheng, Robin Garner, D. Grove, J. E. B. Moss, Sergey I. Salishev","doi":"10.1145/1508293.1508305","DOIUrl":"https://doi.org/10.1145/1508293.1508305","url":null,"abstract":"The power of high-level languages lies in their abstraction over hardware and software complexity, leading to greater security, better reliability, and lower development costs. However, opaque abstractions are often show-stoppers for systems programmers, forcing them to either break the abstraction, or more often, simply give up and use a different language. This paper addresses the challenge of opening up a high-level language to allow practical low-level programming without forsaking integrity or performance.\u0000 The contribution of this paper is three-fold: 1) we draw together common threads in a diverse literature, 2) we identify a framework for extending high-level languages for low-level programming, and 3) we show the power of this approach through concrete case studies. Our framework leverages just three core ideas: extending semantics via intrinsic methods, extending types via unboxing and architectural-width primitives, and controlling semantics via scoped semantic regimes. We develop these ideas through the context of a rich literature and substantial practical experience. We show that they provide the power necessary to implement substantial artifacts such as a high-performance virtual machine, while preserving the software engineering benefits of the host language.\u0000 The time has come for high-level low-level programming to be taken more seriously: 1) more projects now use high-level languages for systems programming, 2) increasing architectural heterogeneity and parallelism heighten the need for abstraction, and 3) a new generation of high-level languages are under development and ripe to be influenced.","PeriodicalId":202844,"journal":{"name":"International Conference on Virtual Execution Environments","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127170075","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}

引用次数: 67

Architectural support for shadow memory in multiprocessors 多处理器阴影内存的架构支持

International Conference on Virtual Execution Environments Pub Date : 2009-03-11 DOI: 10.1145/1508293.1508295

V. Nagarajan, Rajiv Gupta

{"title":"Architectural support for shadow memory in multiprocessors","authors":"V. Nagarajan, Rajiv Gupta","doi":"10.1145/1508293.1508295","DOIUrl":"https://doi.org/10.1145/1508293.1508295","url":null,"abstract":"Runtime monitoring support serves as a foundation for the important tasks of providing security, performing debugging, and improving performance of applications. Often runtime monitoring requires the maintenance of information associated with each of the application's original memory location, which is held in corresponding shadow memory locations. Unfortunately, existing robust shadow memory implementations are inefficient. In this paper, we present a shadow memory implementation that is both efficient and robust. A combination of architectural support (in the form of ISA support and augmentations to the cache coherency protocol) and operating system support (in the form of coupled allocation of memory pages used by the application and associated shadow memory pages) is proposed. By coupling the coherency of shadow memory with the coherency of the main memory, we ensure that the shadow memory instructions execute atomically with their corresponding original memory instructions. Our page allocation policy enables fast translation of original addresses into corresponding shadow memory addresses; thus allowing implicit addressing of shadow memory. This approach obviates the need for page table entries for shadow pages. Our experiments show that the overheads of runtime monitoring tasks are significantly reduced in comparison to previous software implementations.","PeriodicalId":202844,"journal":{"name":"International Conference on Virtual Execution Environments","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127873634","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}

引用次数: 34

Post-copy based live virtual machine migration using adaptive pre-paging and dynamic self-ballooning 使用自适应预分页和动态自膨胀的基于复制后的实时虚拟机迁移

International Conference on Virtual Execution Environments Pub Date : 2009-03-11 DOI: 10.1145/1508293.1508301

M. R. Hines, Kartik Gopalan

{"title":"Post-copy based live virtual machine migration using adaptive pre-paging and dynamic self-ballooning","authors":"M. R. Hines, Kartik Gopalan","doi":"10.1145/1508293.1508301","DOIUrl":"https://doi.org/10.1145/1508293.1508301","url":null,"abstract":"We present the design, implementation, and evaluation of post-copy based live migration for virtual machines (VMs) across a Gigabit LAN. Live migration is an indispensable feature in today's virtualization technologies. Post-copy migration defers the transfer of a VM's memory contents until after its processor state has been sent to the target host. This deferral is in contrast to the traditional pre-copy approach, which first copies the memory state over multiple iterations followed by a final transfer of the processor state. The post-copy strategy can provide a \"win-win\" by reducing total migration time closer to its equivalent time achieved by non-live VM migration. This is done while maintaining the liveness benefits of the pre-copy approach. We compare post-copy extensively against the traditional pre-copy approach on top of the Xen Hypervisor. Using a range of VM workloads we show improvements in several migration metrics including pages transferred, total migration time and network overhead. We facilitate the use of post-copy with adaptive pre-paging in order to eliminate all duplicate page transmissions. Our implementation is able to reduce the number of network-bound page faults to within 21% of the VM's working set for large workloads. Finally, we eliminate the transfer of free memory pages in both migration schemes through a dynamic self-ballooning (DSB) mechanism. DSB periodically releases free pages in a guest VM back to the hypervisor and significantly speeds up migration with negligible performance degradation.","PeriodicalId":202844,"journal":{"name":"International Conference on Virtual Execution Environments","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132980030","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}

引用次数: 446