Pub Date : 2007-11-19DOI: 10.1109/ISPCS.2007.4383784
S. Blixt
A compact module for networked device control is presented, focusing on its IEEE1588 FTP support. Its processor has an unusually big control store, and implements Java- and C-oriented instruction sets that also contain special instructions for compute-intensive algorithms. It is partly writable, allowing Imsys to develop efficient microcode for special sequences and processes and thus reduce the use of clock cycles and memory bandwidth and thereby save power and cost. The chip contains a dual Ethernet MAC and a timer system both of which are tightly controlled by microcode and designed to produce timestamps, which are then processed by microcode. Software on the module includes RTOS, file system, TCP/IP stack, and a 3rd-party PTP Protocol Engine.
{"title":"A Microcontroller with IEEE1588 Support","authors":"S. Blixt","doi":"10.1109/ISPCS.2007.4383784","DOIUrl":"https://doi.org/10.1109/ISPCS.2007.4383784","url":null,"abstract":"A compact module for networked device control is presented, focusing on its IEEE1588 FTP support. Its processor has an unusually big control store, and implements Java- and C-oriented instruction sets that also contain special instructions for compute-intensive algorithms. It is partly writable, allowing Imsys to develop efficient microcode for special sequences and processes and thus reduce the use of clock cycles and memory bandwidth and thereby save power and cost. The chip contains a dual Ethernet MAC and a timer system both of which are tightly controlled by microcode and designed to produce timestamps, which are then processed by microcode. Software on the module includes RTOS, file system, TCP/IP stack, and a 3rd-party PTP Protocol Engine.","PeriodicalId":258197,"journal":{"name":"2007 IEEE International Symposium on Precision Clock Synchronization for Measurement, Control and Communication","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125373129","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}
Pub Date : 2007-11-19DOI: 10.1109/ISPCS.2007.4383777
V. Anandarajah, N. Kalappa, R. Sangole, Safiullah Hussaini, Ya-Shian Li, J. Baboud, J. Moyne
In today's semiconductor fabrication facilities ("fabs"), coordination of time-based information throughout the factory and enterprise has become necessary to support fab-wide diagnostics, control, and information management. This has driven the need to have time synchronization at all levels of the enterprise. Time synchronization protocols such as network time protocol (NTP) and precision time protocol (PTP) have been defined for performing synchronization over distributed systems. Lack of time synchronization among the various subsystems is seen as a factor of poor data quality in equipment data acquisition (EDA) and advanced process control (A PC) analysis. The focus of our study is to investigate the extent and precision of time synchronization that can be practically applied with the available protocols at various levels of the semiconductor factory environment to meet next generation manufacturing requirements. To this end, we describe the objectives, details, and implementation of the simulator that aims to model a semiconductor factory network This will provide a practical perspective to study the accuracy achievable and potential network factors contributing to accuracy degradation of factory-wide time synchronization.
{"title":"Precise Time Synchronization in Semiconductor Manufacturing","authors":"V. Anandarajah, N. Kalappa, R. Sangole, Safiullah Hussaini, Ya-Shian Li, J. Baboud, J. Moyne","doi":"10.1109/ISPCS.2007.4383777","DOIUrl":"https://doi.org/10.1109/ISPCS.2007.4383777","url":null,"abstract":"In today's semiconductor fabrication facilities (\"fabs\"), coordination of time-based information throughout the factory and enterprise has become necessary to support fab-wide diagnostics, control, and information management. This has driven the need to have time synchronization at all levels of the enterprise. Time synchronization protocols such as network time protocol (NTP) and precision time protocol (PTP) have been defined for performing synchronization over distributed systems. Lack of time synchronization among the various subsystems is seen as a factor of poor data quality in equipment data acquisition (EDA) and advanced process control (A PC) analysis. The focus of our study is to investigate the extent and precision of time synchronization that can be practically applied with the available protocols at various levels of the semiconductor factory environment to meet next generation manufacturing requirements. To this end, we describe the objectives, details, and implementation of the simulator that aims to model a semiconductor factory network This will provide a practical perspective to study the accuracy achievable and potential network factors contributing to accuracy degradation of factory-wide time synchronization.","PeriodicalId":258197,"journal":{"name":"2007 IEEE International Symposium on Precision Clock Synchronization for Measurement, Control and Communication","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115261280","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}
Pub Date : 2007-11-19DOI: 10.1109/ISPCS.2007.4383788
S. Rodrigues
Service providers are moving from voice services to bundled services, delivering voice, data, video and wireless (quad-play). TDM services continue to represent significant revenue for carriers, and must be supported in this new model. As the network moves to a packet switched infrastructure, there are still applications that require synchronization, e.g.; traditional TDM services, cellular base stations. Timing synchronization is key to distributed networks and it is critical for today's network environments. As the network services continue to increase, the challenges involved with providing accurate time to systems and applications also increase. This paper addresses the use of IEEE1588TM in conjunction with synchronous Ethernet to deliver accurate synchronization for the telecom network.
{"title":"IEEE-1588 and Synchronous Ethernet in Telecom","authors":"S. Rodrigues","doi":"10.1109/ISPCS.2007.4383788","DOIUrl":"https://doi.org/10.1109/ISPCS.2007.4383788","url":null,"abstract":"Service providers are moving from voice services to bundled services, delivering voice, data, video and wireless (quad-play). TDM services continue to represent significant revenue for carriers, and must be supported in this new model. As the network moves to a packet switched infrastructure, there are still applications that require synchronization, e.g.; traditional TDM services, cellular base stations. Timing synchronization is key to distributed networks and it is critical for today's network environments. As the network services continue to increase, the challenges involved with providing accurate time to systems and applications also increase. This paper addresses the use of IEEE1588TM in conjunction with synchronous Ethernet to deliver accurate synchronization for the telecom network.","PeriodicalId":258197,"journal":{"name":"2007 IEEE International Symposium on Precision Clock Synchronization for Measurement, Control and Communication","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116477990","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}
Pub Date : 2007-11-19DOI: 10.1109/ISPCS.2007.4383782
J. Ridoux, D. Veitch
The status quo for timestamping in PCs is ntpd, which is accurate to 1[ms] at best. For precision applications this is inadequate, but it is a low cost solution which suits many generic applications. IEEE-1588 provides mechanisms for sub-microsecond accuracy, but to achieve this more hardware is needed. We have developed the TSCclock, which gives performance between these two, around 10 microseconds on LAN, sub millisecond beyond, but using commodity hardware. We begin detailed benchmarking of the TSCclock to show its potential as an inexpensive yet accurate software clock, which could be used with IEEE-1588 for LANs, but has wider applicability as a replacement to ntpd.
{"title":"Ten Microseconds Over LAN, for Free","authors":"J. Ridoux, D. Veitch","doi":"10.1109/ISPCS.2007.4383782","DOIUrl":"https://doi.org/10.1109/ISPCS.2007.4383782","url":null,"abstract":"The status quo for timestamping in PCs is ntpd, which is accurate to 1[ms] at best. For precision applications this is inadequate, but it is a low cost solution which suits many generic applications. IEEE-1588 provides mechanisms for sub-microsecond accuracy, but to achieve this more hardware is needed. We have developed the TSCclock, which gives performance between these two, around 10 microseconds on LAN, sub millisecond beyond, but using commodity hardware. We begin detailed benchmarking of the TSCclock to show its potential as an inexpensive yet accurate software clock, which could be used with IEEE-1588 for LANs, but has wider applicability as a replacement to ntpd.","PeriodicalId":258197,"journal":{"name":"2007 IEEE International Symposium on Precision Clock Synchronization for Measurement, Control and Communication","volume":"71 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121594594","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}
Pub Date : 2007-11-19DOI: 10.1109/ISPCS.2007.4383773
S. Schriegel, J. Jasperneite
Networked Industrial Devices must fulfill requirements regarding temperature ranges, noise immunities, and mechanical loads (e.g. DIN EN 60068-2-6). The effects of these environmental conditions on the stability of the frequency of clock sources are well studied [1, 2]. However the influence on the synchronization characteristics of IEEE 1588 can be derived only partly from these investigations. The dependency between the frequency drift (df/dt) and the transmission period of the synchronization frames T is very important for the achievable accuracy of IEEE 1588-based networks. In order to examine these effects, a novel measuring method is proposed in this paper. The results of exemplary measurements at a crystal oscillator with different temperature and mechanical loads will be discussed. These results are compared with the existing requirements for industrial communication systems, especially for the Industrial Ethernet system PROFINET. The objective is to derive coherences and rules for the implementation of functional components of the synchronization procedure.
联网工业设备必须满足有关温度范围，噪声抗扰性和机械负载的要求(例如DIN EN 60068-2-6)。这些环境条件对时钟源频率稳定性的影响已经得到了很好的研究[1,2]。然而，这些研究只能部分地影响IEEE 1588的同步特性。频率漂移(df/dt)与同步帧传输周期T之间的依赖关系对基于IEEE 1588的网络的可实现精度非常重要。为了检验这些影响，本文提出了一种新的测量方法。本文将讨论在不同温度和机械负荷下晶体振荡器的示例性测量结果。这些结果与现有工业通信系统，特别是工业以太网系统PROFINET的要求进行了比较。目标是为同步过程的功能组件的实现派生一致性和规则。
{"title":"Investigation of Industrial Environmental Influences on Clock Sources and their Effect on the Synchronization Accuracy of IEEE 1588","authors":"S. Schriegel, J. Jasperneite","doi":"10.1109/ISPCS.2007.4383773","DOIUrl":"https://doi.org/10.1109/ISPCS.2007.4383773","url":null,"abstract":"Networked Industrial Devices must fulfill requirements regarding temperature ranges, noise immunities, and mechanical loads (e.g. DIN EN 60068-2-6). The effects of these environmental conditions on the stability of the frequency of clock sources are well studied [1, 2]. However the influence on the synchronization characteristics of IEEE 1588 can be derived only partly from these investigations. The dependency between the frequency drift (df/dt) and the transmission period of the synchronization frames T is very important for the achievable accuracy of IEEE 1588-based networks. In order to examine these effects, a novel measuring method is proposed in this paper. The results of exemplary measurements at a crystal oscillator with different temperature and mechanical loads will be discussed. These results are compared with the existing requirements for industrial communication systems, especially for the Industrial Ethernet system PROFINET. The objective is to derive coherences and rules for the implementation of functional components of the synchronization procedure.","PeriodicalId":258197,"journal":{"name":"2007 IEEE International Symposium on Precision Clock Synchronization for Measurement, Control and Communication","volume":"121 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133823214","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}
Pub Date : 2007-11-19DOI: 10.1109/ISPCS.2007.4383786
D. Latremouille, K. Harper, R. Subrahmanyan
This paper describes a first-generation architecture for IEEE 1588 support in an embedded processor. Close coupling is provided between the internal IEEE 1588 timebase and the packet interface in order to minimize the impact of software delays on the calculated time. A versatile timer interface is also directly coupled via hardware to the internal timebase. This allows direct programming of output events, including complex waveforms, from the internal timebase without software intervention.
{"title":"An Architecture for Embedded IEEE 1588 Support","authors":"D. Latremouille, K. Harper, R. Subrahmanyan","doi":"10.1109/ISPCS.2007.4383786","DOIUrl":"https://doi.org/10.1109/ISPCS.2007.4383786","url":null,"abstract":"This paper describes a first-generation architecture for IEEE 1588 support in an embedded processor. Close coupling is provided between the internal IEEE 1588 timebase and the packet interface in order to minimize the impact of software delays on the calculated time. A versatile timer interface is also directly coupled via hardware to the internal timebase. This allows direct programming of output events, including complex waveforms, from the internal timebase without software intervention.","PeriodicalId":258197,"journal":{"name":"2007 IEEE International Symposium on Precision Clock Synchronization for Measurement, Control and Communication","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123714406","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}
Pub Date : 2007-11-19DOI: 10.1109/ISPCS.2007.4383767
H. Kopetz
In many hi-dependability applications (such as a fly-by-wire system) triple-modular redundancy (TMR) is deployed to mask arbitrary failures of any of its constituent components. A TMR system will only work properly if the three replicated channels are synchronized, operate independently and exhibit a deterministic behavior. Determinism requires that two inputs that are presented to the three independent channel at the same instant must be ordered in the same way by all three channels, i.e., simultaneity must be resolved consistently at the system level. In order to resolve this issue of system-wide consistent temporal ordering of events, a global time base of known precision-as established by the IEEE 1588 standard-is of utmost utility. Given such a global time-base of known precision, one can establish a global sparse time model that supports the consistent ordering of events.
{"title":"Why do we need a Sparse Global Time-Base in Dependable Real-time Systems?","authors":"H. Kopetz","doi":"10.1109/ISPCS.2007.4383767","DOIUrl":"https://doi.org/10.1109/ISPCS.2007.4383767","url":null,"abstract":"In many hi-dependability applications (such as a fly-by-wire system) triple-modular redundancy (TMR) is deployed to mask arbitrary failures of any of its constituent components. A TMR system will only work properly if the three replicated channels are synchronized, operate independently and exhibit a deterministic behavior. Determinism requires that two inputs that are presented to the three independent channel at the same instant must be ordered in the same way by all three channels, i.e., simultaneity must be resolved consistently at the system level. In order to resolve this issue of system-wide consistent temporal ordering of events, a global time base of known precision-as established by the IEEE 1588 standard-is of utmost utility. Given such a global time-base of known precision, one can establish a global sparse time model that supports the consistent ordering of events.","PeriodicalId":258197,"journal":{"name":"2007 IEEE International Symposium on Precision Clock Synchronization for Measurement, Control and Communication","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126926827","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}
Pub Date : 2007-11-19DOI: 10.1109/ISPCS.2007.4383772
P. Foster, A. Kouznetsov, N. Vlasenko, C. Walker
We present a distributed synchronisation architecture based on the universal serial bus (USB) found on every PC and laptop. This work has extended the capabilities of USB by adding a synchronization layer, capable of synchronizing a distributed USB network. Synchronization is achieved without consuming USB bandwidth or modifying the USB protocol. The synchronous USB device contains a phase-locked local oscillator. Oscillator phase accuracy is <700 ps across the distributed system, regardless of connection topology and clock jitter is better than 150 ps RMS. The synchronous USB device also contains a notion of real time allowing coordinated real-time operation. This local area synthetic instrumentation (SI) architecture offers sub-nanosecond distributed clock accuracy.
{"title":"Sub-nanosecond Distributed Synchronisation via the Universal Serial Bus","authors":"P. Foster, A. Kouznetsov, N. Vlasenko, C. Walker","doi":"10.1109/ISPCS.2007.4383772","DOIUrl":"https://doi.org/10.1109/ISPCS.2007.4383772","url":null,"abstract":"We present a distributed synchronisation architecture based on the universal serial bus (USB) found on every PC and laptop. This work has extended the capabilities of USB by adding a synchronization layer, capable of synchronizing a distributed USB network. Synchronization is achieved without consuming USB bandwidth or modifying the USB protocol. The synchronous USB device contains a phase-locked local oscillator. Oscillator phase accuracy is <700 ps across the distributed system, regardless of connection topology and clock jitter is better than 150 ps RMS. The synchronous USB device also contains a notion of real time allowing coordinated real-time operation. This local area synthetic instrumentation (SI) architecture offers sub-nanosecond distributed clock accuracy.","PeriodicalId":258197,"journal":{"name":"2007 IEEE International Symposium on Precision Clock Synchronization for Measurement, Control and Communication","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126409262","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}
Pub Date : 2007-11-19DOI: 10.1109/ISPCS.2007.4383781
Sven Meier, Hans Weibel
High availability applications typically count on the network's ability to reconfigure in case of a failure. Since the precision time protocol (PTP) measures the delay of communication paths, it has to cope with network topology changes. The concept of peer-to-peer transparent clocks (TC), introduced with PTP version 2, facilitates the handling of path switchover by measuring the link delays from each node to its neighbors in advance. The parallel redundancy protocol (PRP) follows a different approach from the well-known reconfiguration protocols. It makes use of two independent Ethernet networks. Frames are replicated by the sending node and transmitted over both networks. Duplicates are discarded by the receiving node. There is no distinction between a working and a backup path. The combination of PTP and PRP is studied in this paper. Different models are presented and evaluated with respect to synchronization switchover and implementation issues. An experimental implementation is outlined. The results show that master clock failure as well as network failures can be handled with very low impact on synchronization quality.
{"title":"IEEE 1588 applied in the environment of high availability LANs","authors":"Sven Meier, Hans Weibel","doi":"10.1109/ISPCS.2007.4383781","DOIUrl":"https://doi.org/10.1109/ISPCS.2007.4383781","url":null,"abstract":"High availability applications typically count on the network's ability to reconfigure in case of a failure. Since the precision time protocol (PTP) measures the delay of communication paths, it has to cope with network topology changes. The concept of peer-to-peer transparent clocks (TC), introduced with PTP version 2, facilitates the handling of path switchover by measuring the link delays from each node to its neighbors in advance. The parallel redundancy protocol (PRP) follows a different approach from the well-known reconfiguration protocols. It makes use of two independent Ethernet networks. Frames are replicated by the sending node and transmitted over both networks. Duplicates are discarded by the receiving node. There is no distinction between a working and a backup path. The combination of PTP and PRP is studied in this paper. Different models are presented and evaluated with respect to synchronization switchover and implementation issues. An experimental implementation is outlined. The results show that master clock failure as well as network failures can be handled with very low impact on synchronization quality.","PeriodicalId":258197,"journal":{"name":"2007 IEEE International Symposium on Precision Clock Synchronization for Measurement, Control and Communication","volume":"2014 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114891575","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}
Pub Date : 2007-11-19DOI: 10.1109/ISPCS.2007.4383783
H. Mach, E. Grim, O. Holmeide, C. Calley
Large-scale data acquisition and recording systems have long sought to benefit from the bandwidth, scalability, and low-cost of Ethernet and Internet protocol (IP). However, these systems' requirement for reliable correlation of data with time is impeded by Ethernet's inherently non-deterministic transit delay. With the advent of precision time protocol (PTP), these challenges can now be overcome by deploying synchronized data sources that timestamp data at the source. Furthermore, data producers and consumers constitute a multicast data distribution model, where a single data source is observable by any interested subscribers. This paper details our work for Boeing's 787 which deployed these technologies to build an innovative system capable of providing gigabit data throughput with sub-microsecond synchronization.
{"title":"PTP Enabled Network for Flight Test Data Acquisition and Recording","authors":"H. Mach, E. Grim, O. Holmeide, C. Calley","doi":"10.1109/ISPCS.2007.4383783","DOIUrl":"https://doi.org/10.1109/ISPCS.2007.4383783","url":null,"abstract":"Large-scale data acquisition and recording systems have long sought to benefit from the bandwidth, scalability, and low-cost of Ethernet and Internet protocol (IP). However, these systems' requirement for reliable correlation of data with time is impeded by Ethernet's inherently non-deterministic transit delay. With the advent of precision time protocol (PTP), these challenges can now be overcome by deploying synchronized data sources that timestamp data at the source. Furthermore, data producers and consumers constitute a multicast data distribution model, where a single data source is observable by any interested subscribers. This paper details our work for Boeing's 787 which deployed these technologies to build an innovative system capable of providing gigabit data throughput with sub-microsecond synchronization.","PeriodicalId":258197,"journal":{"name":"2007 IEEE International Symposium on Precision Clock Synchronization for Measurement, Control and Communication","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123010563","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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