• Nuclear Engineering and Technology
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• v.44 no.6
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• pp.663-672
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• 2012

As software based digital I&C (Instrumentation and Control) systems are used more prevalently in nuclear plants, enhancement of software dependability has become an important issue in the area of nuclear I&C systems. Critical attributes of software dependability are safety and reliability. These attributes are tightly related to software failures caused by faults. Software testing and V&V (Verification and Validation) activities are hence important for enhancing software dependability. If the risky modules of safety-critical software can be predicted, it will be possible to focus on testing and V&V activities more efficiently and effectively. It should also make it possible to better allocate resources for regulation activities. We propose a prediction technique to estimate risky software modules by adopting machine learning models based on software complexity metrics. An empirical study with various machine learning algorithms was executed for comparing the prediction performance. Experimental results show SVMs (Support Vector Machines) perform as well or better than the other methods.

• Nuclear Engineering and Technology
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• v.29 no.6
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• pp.433-443
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• 1997

In this work, an analytic approach to the dependability of software in the operational phase is suggested with special attention to the hardware fault effects on the software behavior : The hardware faults considered are memory faults and the dependability measure in question is the reliability. The model is based on the simple reliability theory and the graph theory which represents the software with graph composed of nodes and arcs. Through proper transformation, the graph can be reduced to a simple two-node graph and the software reliability is derived from this graph. Using this model, we predict the reliability of an application software in the digital system (ILS) in the nuclear power plant and show the sensitivity of the software reliability to the major physical parameters which affect the software failure in the normal operation phase. We also found that the effects of the hardware faults on the software failure should be considered for predicting the software dependability accurately in operation phase, especially for the software which is executed frequently. This modeling method is particularly attractive for the medium size programs such as the microprocessor-based nuclear safety logic program.

• Proceedings of the Korean Reliability Society Conference
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• 2001.06a
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• pp.215-218
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• 2001

We consider Part 2 of IEC300(IEC300-2), which describes the elements of a dependability programme and gives guidance on the selection of tasks necessary to achieve specified dependability of products. This standard cross-references and complements ISO 9004-1. It is applicable to hardware and systems containing software product.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7B
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• pp.744-750
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• 2009

In this paper, the unified Markov modeling of hardware and software for AVTMR(AlI Voting Triple Modular Redundancy) system is proposed and the dependability is analyzed. In hardware case, a failure rate is fixed to no time varying parameter. But, in software case, failure rate is applied with time varying parameter. Especially, the dependability(Reliability, Availability, Maintainability, Safety) of software is analyzed with G-O/NHPP for Markov modeling. The dependability of single and AVTMR system is analyzed and simulated with a unified Markov modeling method, and the characteristic of each system is compared accroding to failure rate. This kind of fault tolerat system can be applied to an airplane and life critical system to meet the requirement for a specific requirement.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.725-730
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• 1996

In this work, the software behavior under memory faults in operation phase is modeled and simulated using the stochastic activity network, generalized stochastic Petri nets. This networks permit the representation of concurrency, timeliness, fault tolerance, and degradable performance of system and provide a means for determining the stochastic behavior of a complex system. We estimate the reliability of an application software in the digitized system in nuclear power plants and show the sensitivity of the software reliability to the major physical parameters which affect the software failure in normal operation phase. We found that the effects of the hardware faults on the software failure should be considered for predicting the software dependability accurately in operation phase.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.6
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• pp.435-439
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• 2009

Software used in safety-critical system must have high dependability. Software testing and V&V (Verification and Validation) activities are very important for assuring high software quality. If we can predict the risky modules of safety-critical software, we can focus testing activities and regulation activities more efficiently such as resource distribution. In this paper, we classified the estimated risk class which can be used for deep testing and V&V. We predicted the risk class for each module using support vector machines. We can consider that the modules classified to risk class 5 and 4 are more risky than others relatively. For all classification error rates, we expect that the results can be useful and practical for software testing, V&V, and activities for regulatory reviews.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.2
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• pp.65-72
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• 2007

As embedded system has strict cost and space constraints, it is impossible to apply conventional fault-tolerant techniques directly for increasing the dependability of embedded system. In this paper, we propose software fault-tolerant mechanism which requires only minimum redundancy of system component. We define an utility metric that reflects the dependability of each embedded system component, and then measure the defined utility of each reconfiguration combinations to provide fault tolerance. The proposed utility evaluation process shows exponential complexity. However we reduce the complexity by hierachical subgrouping at the software level of each component. When some components of embedded system are tailed, reconfiguration operation changes the system state from current faulty state to pre-calculated one which has maximum utility combination.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10b
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• pp.33-37
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• 2007

최근 디지털 컴퓨터와 정보처리기술의 발전과 더불어 원자력 발전소의 계측제어시스템과 같은 안전-필수 시스템에서도 디지털 기술을 채택하기 시작했다. 안전-필수 시스템에 사용되는 소프트웨어는 높은 신뢰도(dependability)가 요구된다. 소프트웨어의 신뢰도는 신뢰성(reliability), 안전성, 보안 등 다양한 속성들로 설명될 수 있다. 소프트웨어의 신뢰도 향상을 위한 프로세스는 결함예방프로세스, 결함허용프로세스, 결함제거프로세스 그리고 결함예측프로세스가 있으며 이들 프로세스는 소프트웨어 수명주기 초반부터 수행되어야 한다. 본 논문에서는 소프트웨어 신뢰도향상을 위한 신뢰도 프로세스 모델과 개발 단계별로 수행되어야 할 신뢰도 태스크를 제시한다.

• Journal of information and communication convergence engineering
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• v.17 no.2
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• pp.117-127
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• 2019

In software engineering, to ensure reliability between systems, describing both system architecture and assurance arguments between system elements is considered necessary. There are proposals for system architecture assurance, but use of these traditional methods often requires development of different diagrams using different editors. Because the visual sense of the traditional methods is inadequate, errors readily occur when manipulating different diagrams. Therefore, it is essential that the assurance of dependability between components and systems is visualized and easy to understand. In this paper, an integrated approach to describe the relationship between system actors and system architecture is proposed, and this approach is clarified using an enterprise architecture modeling language. A case study is carried out and comparison to the traditional approach $d^*$ framework is explained. The comparison results show that the proposed approach is more suitable for ensuring dependability in system architecture.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.05a
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• pp.219-219
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• 2001