7,573 research outputs found

    Periodic Application of Concurrent Error Detection in Processor Array Architectures

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    Processor arrays can provide an attractive architecture for some applications. Featuring modularity, regular interconnection and high parallelism, such arrays are well-suited for VLSI/WSI implementations, and applications with high computational requirements, such as real-time signal processing. Preserving the integrity of results can be of paramount importance for certain applications. In these cases, fault tolerance should be used to ensure reliable delivery of a system's service. One aspect of fault tolerance is the detection of errors caused by faults. Concurrent error detection (CED) techniques offer the advantage that transient and intermittent faults may be detected with greater probability than with off-line diagnostic tests. Applying time-redundant CED techniques can reduce hardware redundancy costs. However, most time-redundant CED techniques degrade a system's performance

    Flight deck engine advisor

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    The focus of this project is on alerting pilots to impending events in such a way as to provide the additional time required for the crew to make critical decisions concerning non-normal operations. The project addresses pilots' need for support in diagnosis and trend monitoring of faults as they affect decisions that must be made within the context of the current flight. Monitoring and diagnostic modules developed under the NASA Faultfinder program were restructured and enhanced using input data from an engine model and real engine fault data. Fault scenarios were prepared to support knowledge base development activities on the MONITAUR and DRAPhyS modules of Faultfinder. An analysis of the information requirements for fault management was included in each scenario. A conceptual framework was developed for systematic evaluation of the impact of context variables on pilot action alternatives as a function of event/fault combinations

    Developing a distributed electronic health-record store for India

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    The DIGHT project is addressing the problem of building a scalable and highly available information store for the Electronic Health Records (EHRs) of the over one billion citizens of India

    Automated test of evolving software

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    A thesis submitted to the University of Luton, in partial fulfilment of the requirements for the degree of Doctor of PhilosophyComputers and the software they run are pervasive, yet released software is often unreliable, which has many consequences. Loss of time and earnings can be caused by application software (such as word processors) behaving incorrectly or crashing. Serious disruption can occur as in the l4th August 2003 blackouts in North East USA and Canadal, or serious injury or death can be caused as in the Therac-25 overdose incidents. One way to improve the quality of software is to test it thoroughly. However, software testing is time consuming, the resources, capabilities and skills needed to carry it out are often not available and the time required is often curtailed because of pressures to meet delivery deadlines3. Automation should allow more thorough testing in the time available and improve the quality of delivered software, but there are some problems with automation that this research addresses. Firstly, it is difficult to determine ifthe system under test (SUT) has passed or failed a test. This is known as the oracle problem4 and is often ignored in software testing research. Secondly, many software development organisations use an iterative and incremental process, known as evolutionary development, to write software. Following release, software continues evolving as customers demand new features and improvements to existing ones5. This evolution means that automated test suites must be maintained throughout the life ofthe software. A contribution of this research is a methodology that addresses automatic generation of the test cases, execution of the test cases and evaluation of the outcomes from running each test. "Predecessor" software is used to solve the oracle problem. This is software that already exists, such as a previous version of evolving software, or software from a different vendor that solves the same, or similar, problems. However, the resulting oracle is assumed not be perfect, so rules are defined in an interface, which are used by the evaluator in the test evaluation stage to handle the expected differences. The interface also specifies functional inputs and outputs to the SUT. An algorithm has been developed that creates a Markov Chain Transition Matrix (MCTM) model of the SUT from the interface. Tests are then generated automatically by making a random walk of the MCTM. This means that instead of maintaining a large suite of tests, or a large model of the SUT, only the interface needs to be maintained. 1) NERC Steering Group (2004). Technical Analysis ofthe August 14,2003, Blackout: What Happened, Why, and What Did We Learn? July 13th 2004. Available from: ftp:/ /www.nerc.com/pub/sys/all_ updl/docslblackoutINERC ]inatBlackout_Report _ 07_13_ 04.pdf 2) Leveson N. G., Turner C. S. (1993) An investigation of the Therac-25 accidents. IEEE Computer, Vo126, No 7, Pages 18-41. 3) LogicaCMG (2005) Testing Times for Board Rooms. Available from http://www.logicacmg.com/pdf/trackeditestingTimesBoardRooms.pdf 4) Bertolino, A. (2003) Software Testing Research and Practice, ASM 2003, Lecture Notes in Computer Science, Vol 2589, Pages 1-21. 5) Sommerville, 1. (2004) Software Engineering, 7th Edition. Addison Wesley. ISBN 0-321-21026-3

    Testability and redundancy techniques for improved yield and reliability of CMOS VLSI circuits

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    The research presented in this thesis is concerned with the design of fault-tolerant integrated circuits as a contribution to the design of fault-tolerant systems. The economical manufacture of very large area ICs will necessitate the incorporation of fault-tolerance features which are routinely employed in current high density dynamic random access memories. Furthermore, the growing use of ICs in safety-critical applications and/or hostile environments in addition to the prospect of single-chip systems will mandate the use of fault-tolerance for improved reliability. A fault-tolerant IC must be able to detect and correct all possible faults that may affect its operation. The ability of a chip to detect its own faults is not only necessary for fault-tolerance, but it is also regarded as the ultimate solution to the problem of testing. Off-line periodic testing is selected for this research because it achieves better coverage of physical faults and it requires less extra hardware than on-line error detection techniques. Tests for CMOS stuck-open faults are shown to detect all other faults. Simple test sequence generation procedures for the detection of all faults are derived. The test sequences generated by these procedures produce a trivial output, thereby, greatly simplifying the task of test response analysis. A further advantage of the proposed test generation procedures is that they do not require the enumeration of faults. The implementation of built-in self-test is considered and it is shown that the hardware overhead is comparable to that associated with pseudo-random and pseudo-exhaustive techniques while achieving a much higher fault coverage through-the use of the proposed test generation procedures. The consideration of the problem of testing the test circuitry led to the conclusion that complete test coverage may be achieved if separate chips cooperate in testing each other's untested parts. An alternative approach towards complete test coverage would be to design the test circuitry so that it is as distributed as possible and so that it is tested as it performs its function. Fault correction relies on the provision of spare units and a means of reconfiguring the circuit so that the faulty units are discarded. This raises the question of what is the optimum size of a unit? A mathematical model, linking yield and reliability is therefore developed to answer such a question and also to study the effects of such parameters as the amount of redundancy, the size of the additional circuitry required for testing and reconfiguration, and the effect of periodic testing on reliability. The stringent requirement on the size of the reconfiguration logic is illustrated by the application of the model to a typical example. Another important result concerns the effect of periodic testing on reliability. It is shown that periodic off-line testing can achieve approximately the same level of reliability as on-line testing, even when the time between tests is many hundreds of hours

    An Analysis on the Applicability of Meta-Heuristic Searching Techniques for Automated Test Data Generation in Automatic Programming Assessment

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    حظي تقييم البرمجة التلقائي (APA) بالكثير من الاهتمام بين الباحثين بشكل أساسي لدعم الدرجات الآلية ووضع علامات على المهامالمكلف بادائها الطلاب أو التدريبات بشكل منهجي. يتم تعريف APA بشكل شائع كطريقة يمكن أن تعزز الدقة والكفاءة والاتساق وكذلك تقديمملاحظات فورية لحلول للطلاب. في تحقيق APA ، تعد عملية إنشاء بيانات الاختبار مهمة للغاية وذلك لإجراء اختبار ديناميكي لمهمةالطلاب. في مجال اختبار البرمجيات ، أوضحت العديد من الأبحاث التي تركز على توليد بيانات الاختبار نجاح اعتماد تقنيات البحث الفوقية(MHST) من أجل تعزيز إجراءات استنباط بيانات الاختبار المناسبة للاختبار الفعال. ومع ذلك، فإن الأبحاث التي أجريت على APA حتىالآن لم تستغل بعد التقنيات المفيدة لتشمل تغطية اختبار جودة برنامج أفضل. لذلك ، أجرت هذه الدراسة تقييماً مقارنا لتحديد أي تقنية بحثفوقي قابلة للتطبيق لدعم كفاءة توليد بيانات الاختبار الآلي (ATDG) في تنفيذ اختبار وظيفي ديناميكي. في تقييم البرمجة التلقائي يتم تضمينالعديد من تقنيات البحث الفوقية الحديثة في التقييم المقارن الذي يجمع بين كل من خوارزميات البحث المحلية والعالمية من عام 2000 حتىعام 2018 .تشير نتيجة هذه الدراسة إلى أن تهجين Cuckoo Search مع Tabu Search و lévy flight كواحدة من طرق البحث الفوقية الواعدةليتم تطبيقها ، حيث أنه يتفوق على الطرق الفوقية الأخرى فيما يتعلق بعدد التكرارات ونطاق المدخلات.Automatic Programming Assessment (APA) has been gaining lots of attention among researchers mainly to support automated grading and marking of students’ programming assignments or exercises systematically. APA is commonly identified as a method that can enhance accuracy, efficiency and consistency as well as providing instant feedback on students’ programming solutions. In achieving APA, test data generation process is very important so as to perform a dynamic testing on students’ assignment. In software testing field, many researches that focus on test data generation have demonstrated the successful of adoption of Meta-Heuristic Search Techniques (MHST) so as to enhance the procedure of deriving adequate test data for efficient testing. Nonetheless, thus far the researches on APA have not yet usefully exploited the techniques accordingly to include a better quality program testing coverage. Therefore, this study has conducted a comparative evaluation to identify any applicable MHST to support efficient Automated Test Data Generation (ATDG) in executing a dynamic-functional testing in APA. Several recent MHST are included in the comparative evaluation combining both the local and global search algorithms ranging from the year of 2000 until 2018. Result of this study suggests that the hybridization of Cuckoo Search with Tabu Search and lévy flight as one of promising MHST to be applied, as it’s outperforms other MHST with regards to number of iterations and range of inputs

    The Telecommunications and Data Acquisition Report

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    Deep Space Network advanced systems, very large scale integration architecture for decoders, radar interface and control units, microwave time delays, microwave antenna holography, and a radio frequency interference survey are among the topics discussed
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