The replication scheme of a distributed database determines how many replicas of each object are created, and to which processors these replicas are allocated. This scheme critically affects the performance of a distr...
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The replication scheme of a distributed database determines how many replicas of each object are created, and to which processors these replicas are allocated. This scheme critically affects the performance of a distributed system, since reading an object locally is less costly than reading it from a remote processor. Therefore in a read-intensive network a widely distributed replication is mandated. On the other hand, an update of an object is usually written to all, or a majority of the replicas, and therefore in a write-intensive network a narrowly distributed replication is mandated. In other words, the optimal replication scheme depends on the read-write pattern for each object. The authors propose a practical algorithm, called dynamic-data-allocation (DDA), that changes the replication scheme of an object (i.e. the processors which store a replica of the object) dynamically as the read-write pattern of the object changes in the network. They assume that the changes in the read-write pattern are not known a priori.< >
This paper presents a newly developed environment for supporting the management of software testing. This environment has been built on the top of UNIX and RCS to maintain all versions of the specifications, the test ...
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This paper presents a newly developed environment for supporting the management of software testing. This environment has been built on the top of UNIX and RCS to maintain all versions of the specifications, the test cases and programs, as well as managing the relationships among these components. It is a practical model of applying software configuration management methods to the testing process.< >
With the Navy leaning towards a smaller but better trained force, using simulators in training becomes a cost effective way of keeping our military edge. Several innovations are being utilized in today's simulator...
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With the Navy leaning towards a smaller but better trained force, using simulators in training becomes a cost effective way of keeping our military edge. Several innovations are being utilized in today's simulators. Hardware and software designs now include distributed computer architectures, real-time, multi-tasking operating systems, flexible generic consoles, commercial off-the-shelf equipment, standard real-time ocean acoustic models, and standard acoustic data bases. This paper describes these technologies and their innovative application in the Navy's newest Anti-Submarine Warfare Team Trainer, Device 14A12. Device 14A12 simulates sonar, fire control, electronic warfare, bridge, ownship aircraft and Naval Tactical Data systems (NTDS) for 16 surface ownship classes. Device 14A12 also simulates multiple air, surface and subsurface threat, neutral and friendly platforms as well as missiles and torpedoes. The innovative modeling of these systems along with Device 14A12's enormous flexibility will allow the Navy to provide effective tactical training for the surface fleet now and in the future.
Electromagnetic interference (EMI) is one of the major contributors to mission degradation in our fleet today due to the increase in population and sensitivity of both topside and below deck electronic systems. Sensit...
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Electromagnetic interference (EMI) is one of the major contributors to mission degradation in our fleet today due to the increase in population and sensitivity of both topside and below deck electronic systems. Sensitive combat systems designed to counter intelligent and deceptive targets can be confused by the complex intra-ship EM environment. This can cause identification failure or losing "track" of a hostile or incoming missile or even engaging "friendly targets." Topside design and integration efforts have been used to reduce EMI, but this is not the total solution to the problem. A program of total ship and system EMI assessment and control must be implemented. This program must exploit electromagnetic compatibility (EMC) optimization in electronic circuit design and take advantage of and (in some cases) direct topside shapes and structures to control the propagation of desired and undesired EM energy. Positive and active control of EM design characteristics are absolutely required before optimum combat system effectiveness can be realized. This paper will describe the current topside design process, EMC improvements being made, and how the process is being integrated into, and is dependent upon, the ship design process. It will give examples of some of the major mission degrading EMI problems in the fleet today and how past problems were solved with existing EM analysis programs. It will also discuss the control of EM energy in new design through the use of techniques being developed such as ray tracing and ray casting. The paper projects where the challenges lie for future topside and EM engineering designers and describes how the equipment technology transfer process must be better integrated to meet the challenge of effective EMI control.
Advances in compiler technology have recently led to the introduction of a new architectural paradigm, called the Very Long Instruction Word (VLIW) architecture. The Multijlow TRACE series of processors is the jirst c...
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Model selection based on a predictive performance measure is compared to model selection based on maximum likelihood. Both procedures exhibit unstable relative performance when predictive performance is measured over ...
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Poisson processes with failure intensity functions that are approximately constant are investigated. Maximum likelihood estimation procedures are used to estimate the failure intensity for a fixed level of approximati...
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Design for dependability has long been an important issue for computersystems. While several dependability analysis tools have been produced, no effort has been made to automate the design for dependability. This pap...
ISBN:
(纸本)9780897913638
Design for dependability has long been an important issue for computersystems. While several dependability analysis tools have been produced, no effort has been made to automate the design for dependability. This paper describes ASSURE, an automated design for dependability advisor, which is part of the MICON system for rapid prototyping of small computersystems. A design for dependability methodology and a formal interface between synthesis and dependability analysis are presented. ASSURE's operation includes dependability analysis, evaluation of dependability enhancement techniques using predictive estimation, and selection of a technique. Different kinds of knowledge used in designing for dependability are identified, including an algorithmic approach for dependability analysis and a knowledge-based approach for suggesting dependability enhancement techniques. Examples of designs produced using ASSURE as a dependability advisor are provided and show an order of magnitude dependability improvement.
作者：
Raymond JacobyYoshihiro TohmaTOSHIBA Corporation
Systems & Software Engineering Laboratory Saiwat-ku Kawasaki-shi 210 Japan and Department of Computer Science Tokyo Institute of Technology Ookayama 2-12-1 Meguro-Ku Tokyo Department of Computer Science
Tokyo Institute of Technology Ookayama 2-12-1 Meguro-Ku Tokyo
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