Pub Date : 1995-04-25DOI: 10.1109/WPDRTS.1995.470503
T. Ae, K. Nishimura, R. Aibara, K. Sakai, K. Nakamura
We propose a multimedia network system using VLIW hardware stack processors, which supports mainly the presentation layer of OSI protocol and fits various real-time applications including intelligent processing.<>
{"title":"Real-time multimedia network system using VLIW hardware stack processor","authors":"T. Ae, K. Nishimura, R. Aibara, K. Sakai, K. Nakamura","doi":"10.1109/WPDRTS.1995.470503","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470503","url":null,"abstract":"We propose a multimedia network system using VLIW hardware stack processors, which supports mainly the presentation layer of OSI protocol and fits various real-time applications including intelligent processing.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122493699","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 : 1995-04-25DOI: 10.1109/WPDRTS.1995.470511
N. Howes, Jonathan D. Wood, A. Goforth
This paper is a preliminary report of an ARPA sponsored study. It focuses on designing real-time command and control or battle management systems for parallel and distributed architectures. Due to delays in other ARPA programs, the targeted architectures were not available during the time frame of the study. The results of the study were, however, tested on more conventional sequential and parallel platforms. The design method discussed here is fundamentally different from those assumed by current real-time scheduling theories, e.g., rate-monotonic, earliest-deadline-first, least-laxity or best-effort. These theories assume that the fundamental unit of prioritization is the task. In this new method, the fundamental unit of prioritization is called a work item. Work items are functions the system performs that have timing requirements (deadlines) associated with them in the requirements specification. Current scheduling theories are applied using artifact deadlines introduced by designers whereas this new method schedules work items to meet specification deadlines (sometimes called end-to-end deadlines) required by the user. With this method, tasks have no priorities. A collection of tasks with no priorities will be called a collection of peer tasks. The study showed that it is possible to schedule work items based on importance rather than urgency while still meeting as many work item deadlines as can be met by scheduling tasks with respect to urgency. Also, it showed that the minimum on-line deadline that can be guaranteed for a work item of highest importance, scheduled at run-time, is approximately the inverse of the throughput, measured in work items per second, for a work load consisting only of work items of that type. Further, it was shown that it provides optimal utilization of a single processor machine, and that its timing behavior is predictable (provable) for both single and multiprocessor machines. Finally, it was shown that throughput is not degraded during overload.<>
{"title":"The peer tasking design method","authors":"N. Howes, Jonathan D. Wood, A. Goforth","doi":"10.1109/WPDRTS.1995.470511","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470511","url":null,"abstract":"This paper is a preliminary report of an ARPA sponsored study. It focuses on designing real-time command and control or battle management systems for parallel and distributed architectures. Due to delays in other ARPA programs, the targeted architectures were not available during the time frame of the study. The results of the study were, however, tested on more conventional sequential and parallel platforms. The design method discussed here is fundamentally different from those assumed by current real-time scheduling theories, e.g., rate-monotonic, earliest-deadline-first, least-laxity or best-effort. These theories assume that the fundamental unit of prioritization is the task. In this new method, the fundamental unit of prioritization is called a work item. Work items are functions the system performs that have timing requirements (deadlines) associated with them in the requirements specification. Current scheduling theories are applied using artifact deadlines introduced by designers whereas this new method schedules work items to meet specification deadlines (sometimes called end-to-end deadlines) required by the user. With this method, tasks have no priorities. A collection of tasks with no priorities will be called a collection of peer tasks. The study showed that it is possible to schedule work items based on importance rather than urgency while still meeting as many work item deadlines as can be met by scheduling tasks with respect to urgency. Also, it showed that the minimum on-line deadline that can be guaranteed for a work item of highest importance, scheduled at run-time, is approximately the inverse of the throughput, measured in work items per second, for a work load consisting only of work items of that type. Further, it was shown that it provides optimal utilization of a single processor machine, and that its timing behavior is predictable (provable) for both single and multiprocessor machines. Finally, it was shown that throughput is not degraded during overload.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133871503","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 : 1995-04-25DOI: 10.1109/WPDRTS.1995.470507
R. Volz, R. Theriault, G. C. Smith, R. Waldrop
Since the standardization of the Ada programming language in 1989, much research has gone into the distribution of Ada programs across a number of separate processors. However, no standard for distribution of Ada 89 programs has emerged. A new language standard, known as Ada 95, includes explicit support for the distribution of Ada programs. This paper describes the techniques and a graphical tool which allow the distribution of Ada 85 programs, using a sub-set of the methodology developed for Ada 95, with extensions to allow coarse grain parallel programming. This work is also a precursor to an implementation of the Ada 95 Distributed Systems Annex being developed by the authors in cooperation with the NYU GNAT team and France Telecom University.<>
{"title":"Distributed and parallel execution in Ada 83","authors":"R. Volz, R. Theriault, G. C. Smith, R. Waldrop","doi":"10.1109/WPDRTS.1995.470507","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470507","url":null,"abstract":"Since the standardization of the Ada programming language in 1989, much research has gone into the distribution of Ada programs across a number of separate processors. However, no standard for distribution of Ada 89 programs has emerged. A new language standard, known as Ada 95, includes explicit support for the distribution of Ada programs. This paper describes the techniques and a graphical tool which allow the distribution of Ada 85 programs, using a sub-set of the methodology developed for Ada 95, with extensions to allow coarse grain parallel programming. This work is also a precursor to an implementation of the Ada 95 Distributed Systems Annex being developed by the authors in cooperation with the NYU GNAT team and France Telecom University.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117216852","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 : 1995-04-25DOI: 10.1109/WPDRTS.1995.470500
U. Chandra, Marion, Harmon
Predicting the execution time of straight line code sequences is essential for reliable real-time systems. Traditional timing techniques suck as table lookup method, instruction counting and averaging are inadequate to predict a tight execution time on reduced instruction set processors since they do not account for the low-level parallelism that exists in these processors. This paper presents a server based methodology for predicting point-to-point execution times of code segments. A sequence of assembler instructions is analyzed to identify the execution paths and the basic blocks within the execution path. The execution of these assembler instructions is simulated by scheduling them on the different servers such as caches and pipelines. Performance is predicted by consolidating the execution times of the basic blocks and then the execution paths. This methodology was applied to Alpha AXP architecture as a case study. Execution times of three benchmark programs were observed on an Alpha AXP machine and predicted using this methodology. The worst case time predicted by this methodology bounds the observed worst case time and the best case execution time is lower than the observed best case execution time.<>
{"title":"Predictability of program execution times on superscalar pipelined architectures","authors":"U. Chandra, Marion, Harmon","doi":"10.1109/WPDRTS.1995.470500","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470500","url":null,"abstract":"Predicting the execution time of straight line code sequences is essential for reliable real-time systems. Traditional timing techniques suck as table lookup method, instruction counting and averaging are inadequate to predict a tight execution time on reduced instruction set processors since they do not account for the low-level parallelism that exists in these processors. This paper presents a server based methodology for predicting point-to-point execution times of code segments. A sequence of assembler instructions is analyzed to identify the execution paths and the basic blocks within the execution path. The execution of these assembler instructions is simulated by scheduling them on the different servers such as caches and pipelines. Performance is predicted by consolidating the execution times of the basic blocks and then the execution paths. This methodology was applied to Alpha AXP architecture as a case study. Execution times of three benchmark programs were observed on an Alpha AXP machine and predicted using this methodology. The worst case time predicted by this methodology bounds the observed worst case time and the best case execution time is lower than the observed best case execution time.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"33 11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128926489","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 : 1995-04-25DOI: 10.1109/WPDRTS.1995.470512
Ben Kao, Hector Garcia-Molina, Brad Adelberg
When building a distributed real-time system, one can either build the whole system from scratch, or from pre-existing standard components. Although the former allows better scheduling design, it may not be economical in terms of the cost and time of development. This paper studies the performance of distributed soft real-time systems that use standard components with various scheduling algorithms and suggests ways to improve them.<>
{"title":"On building distributed soft real-time systems","authors":"Ben Kao, Hector Garcia-Molina, Brad Adelberg","doi":"10.1109/WPDRTS.1995.470512","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470512","url":null,"abstract":"When building a distributed real-time system, one can either build the whole system from scratch, or from pre-existing standard components. Although the former allows better scheduling design, it may not be economical in terms of the cost and time of development. This paper studies the performance of distributed soft real-time systems that use standard components with various scheduling algorithms and suggests ways to improve them.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"183 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121331774","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 : 1995-04-25DOI: 10.1109/WPDRTS.1995.470506
A. Wellings, S. Mitchell, A. Burns
Integrating concurrent and object-oriented language facilities is currently an active research area. There are a few experimental languages which attempt to combine various models of concurrency within an OOP framework. Most of these suffer from the so called inheritance anomaly where a concurrent object's synchronisation code needs to be modified if the object is extended. Ada 95 has avoided some of these problems by integrating protected types into the model of type extensibility. However this has been at the expense of some loss of generality. This paper considers three paradigms of combining protected types with the type extension. The strengths and weaknesses of each approach is discussed. We conclude that none of the approaches are entirely satisfactory and they either suffer from the inheritance anomaly or preclude further extensions.<>
{"title":"Object-oriented programming with protected types in Ada 95","authors":"A. Wellings, S. Mitchell, A. Burns","doi":"10.1109/WPDRTS.1995.470506","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470506","url":null,"abstract":"Integrating concurrent and object-oriented language facilities is currently an active research area. There are a few experimental languages which attempt to combine various models of concurrency within an OOP framework. Most of these suffer from the so called inheritance anomaly where a concurrent object's synchronisation code needs to be modified if the object is extended. Ada 95 has avoided some of these problems by integrating protected types into the model of type extensibility. However this has been at the expense of some loss of generality. This paper considers three paradigms of combining protected types with the type extension. The strengths and weaknesses of each approach is discussed. We conclude that none of the approaches are entirely satisfactory and they either suffer from the inheritance anomaly or preclude further extensions.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120966943","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 : 1995-04-25DOI: 10.1109/WPDRTS.1995.470504
R. Bettati, A. Nica
HIPPI provides a very-high-speed communication medium, which is very well suited for a large number of bandwidth-demanding distributed applications. Unfortunately, its circuit-switched nature makes it very difficult to provide real-time guarantees when connections contend for network resources. We present a time-division-multiplex access scheme designed to give timing guarantees to high-speed connections. We describe the problem of scheduling the access to a HIPPI network, and show that, although the problem is very unlikely to be computationally tractable, very simple heuristics give high network utilizations for moderately-sized networks. We present the RMP/RMCP protocol, our implementation of the scheme described in this paper on the XUNET-West HIPPI testbed.<>
{"title":"Real-time networking over HIPPI","authors":"R. Bettati, A. Nica","doi":"10.1109/WPDRTS.1995.470504","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470504","url":null,"abstract":"HIPPI provides a very-high-speed communication medium, which is very well suited for a large number of bandwidth-demanding distributed applications. Unfortunately, its circuit-switched nature makes it very difficult to provide real-time guarantees when connections contend for network resources. We present a time-division-multiplex access scheme designed to give timing guarantees to high-speed connections. We describe the problem of scheduling the access to a HIPPI network, and show that, although the problem is very unlikely to be computationally tractable, very simple heuristics give high network utilizations for moderately-sized networks. We present the RMP/RMCP protocol, our implementation of the scheme described in this paper on the XUNET-West HIPPI testbed.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"33 8","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121004189","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 : 1995-04-25DOI: 10.1109/WPDRTS.1995.470508
T. Vardanega
An increasing proportion of the critical control activities performed on board of modern satellite systems is nowadays being implemented in software. The resulting software systems have thus to accommodate a large spectrum of processing requirements, which shows an increasing demand for event-driven activities. Hence, process-oriented preemptive priority-based scheduling is most suited for use in such systems. This paper contends that the recent advances in the domain of hard real-time make Ada tasking particularly apt for it. This paper shows that, although a variety of reasons exist to date for not using any of the Ada tasking in critical applications, most of such reasons may be defeated by educated design and efficient implementations.<>
{"title":"On the use of Ada tasking in the building of satellite control software","authors":"T. Vardanega","doi":"10.1109/WPDRTS.1995.470508","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470508","url":null,"abstract":"An increasing proportion of the critical control activities performed on board of modern satellite systems is nowadays being implemented in software. The resulting software systems have thus to accommodate a large spectrum of processing requirements, which shows an increasing demand for event-driven activities. Hence, process-oriented preemptive priority-based scheduling is most suited for use in such systems. This paper contends that the recent advances in the domain of hard real-time make Ada tasking particularly apt for it. This paper shows that, although a variety of reasons exist to date for not using any of the Ada tasking in critical applications, most of such reasons may be defeated by educated design and efficient implementations.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127722788","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 : 1995-04-25DOI: 10.1109/WPDRTS.1995.470494
J. Caruso
Standard hardware performance and cost concerns are increasingly driving designers of real-time systems toward the use of Commercial Off-The-Shelf (COTS) components. There are many difficulties with this transition yet there is a perceived lack of interest in the subject. It is speculated that the community is not fully aware of the problems being encountered in utilizing COTS components. This paper describes some of the difficulties system designers face, using experiences from on-going efforts to transition a large real-time system, the AEGIS Weapons System (AWS), to a distributed compute plant built with COTS.<>
{"title":"The challenge of the increased use of COTS: a developer's perspective","authors":"J. Caruso","doi":"10.1109/WPDRTS.1995.470494","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470494","url":null,"abstract":"Standard hardware performance and cost concerns are increasingly driving designers of real-time systems toward the use of Commercial Off-The-Shelf (COTS) components. There are many difficulties with this transition yet there is a perceived lack of interest in the subject. It is speculated that the community is not fully aware of the problems being encountered in utilizing COTS components. This paper describes some of the difficulties system designers face, using experiences from on-going efforts to transition a large real-time system, the AEGIS Weapons System (AWS), to a distributed compute plant built with COTS.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124972285","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 : 1995-04-25DOI: 10.1109/WPDRTS.1995.470497
M. Adelantado, F. Boniol, S. de Givry
One of the major challenge of next embedded systems is to involve intelligence while preserving the classical real-time properties: (a) reactivity, i.e. the capability to react continuously towards asynchronous inputs, and (b) predictability. Furthermore, one of the main property which is requested in this kind of systems operating in a highly non-deterministic outside environment, is adaptability to new and unexpected conditions, and particularly to dynamic temporal deadlines. Strong predictability often means that it should be possible to prove both the functional and temporal behavior of a system, in response to any combination of signals from outside environment, and particularly to prove that critical tasks meet their deadlines. On the contrary, in non-deterministic environments involving dynamic timing constraints, the assumption that critical tasks meet their deadlines can not be guaranteed. In that sense, strong predictability and adaptability are contradictory requirements. Furthermore, intelligence often means complex computations. In that sense reactivity and punctuality seem also to be incompatible with reasoning capabilities. The aim of this paper is to investigate a programming model, called SATURNE, addressing the issue of intelligent real-time systems, that is how to mix adaptability, reactivity and predictability. We only focuses on adaptability to temporal deadlines, addressing the problem of guaranteeing a response when temporal deadlines may be statically unpredictable. SATURNE is based on a mixed reactive-anytime approach. The main idea is to introduce firstly a reactive model of computation providing predictability, and secondly an anytime model of computation providing adaptability to dynamic temporal deadlines.<>
{"title":"SATURNE: a reactive-anytime programming model for intelligent embedded real-time systems","authors":"M. Adelantado, F. Boniol, S. de Givry","doi":"10.1109/WPDRTS.1995.470497","DOIUrl":"https://doi.org/10.1109/WPDRTS.1995.470497","url":null,"abstract":"One of the major challenge of next embedded systems is to involve intelligence while preserving the classical real-time properties: (a) reactivity, i.e. the capability to react continuously towards asynchronous inputs, and (b) predictability. Furthermore, one of the main property which is requested in this kind of systems operating in a highly non-deterministic outside environment, is adaptability to new and unexpected conditions, and particularly to dynamic temporal deadlines. Strong predictability often means that it should be possible to prove both the functional and temporal behavior of a system, in response to any combination of signals from outside environment, and particularly to prove that critical tasks meet their deadlines. On the contrary, in non-deterministic environments involving dynamic timing constraints, the assumption that critical tasks meet their deadlines can not be guaranteed. In that sense, strong predictability and adaptability are contradictory requirements. Furthermore, intelligence often means complex computations. In that sense reactivity and punctuality seem also to be incompatible with reasoning capabilities. The aim of this paper is to investigate a programming model, called SATURNE, addressing the issue of intelligent real-time systems, that is how to mix adaptability, reactivity and predictability. We only focuses on adaptability to temporal deadlines, addressing the problem of guaranteeing a response when temporal deadlines may be statically unpredictable. SATURNE is based on a mixed reactive-anytime approach. The main idea is to introduce firstly a reactive model of computation providing predictability, and secondly an anytime model of computation providing adaptability to dynamic temporal deadlines.<<ETX>>","PeriodicalId":438550,"journal":{"name":"Proceedings of Third Workshop on Parallel and Distributed Real-Time Systems","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123515806","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：