• Journal of the Korean Society of Systems Engineering
• /
• v.16 no.1
• /
• pp.84-97
• /
• 2020

This paper aims to develop an optimized inventory management method for safety critical Instrument and Control (I&C) components. In this regard, the paper focuses on estimating the consumption rate of I&C components using demand forecasting methods. The target component for this paper is the Foxboro SPEC-200 controller. This component was chosen because it has highest consumption rate among the safety critical I&C components in Korean OPR-1000 NPPs. Three analytical methods were chosen in order to develop the demand forecasting methods; Poisson, Generalized Linear Model (GLM) and Bootstrapping. The results show that the GLM gives better accuracy than the other analytical methods. This is because the GLM considers the maintenance level of the component by discriminating between corrective and preventive.

• Journal of Korean Society for Quality Management
• /
• v.18 no.2
• /
• pp.33-42
• /
• 1990

This paper proposes the maintenance model of multi-component system when the failure characteristics and types of components are considered. In this model, it is assumed that a system is composed of a critical component, a major component and a minor component. Also, failure types is classified into major failure and minor failure. If major failure occurs to critical component before system age replacement time, the system is renewed. If major failure does not occur until its age replacement time, preventive maintenance is performed at age replacement time T. Minimal repairs are carried out after each minor failure. Major component is minimal-repaired if any failure is discovered during operation. Minor component should be replaced as soon as any failure is found. This paper determines the optimal replacement time of the system which minimizes total maintenance cost. Numerical example illustrates these results.

• Progress in Superconductivity and Cryogenics
• /
• v.8 no.1
• /
• pp.39-44
• /
• 2006

Before applying HTS power cable to the real utility. system analysis should be carried out by some simulation tools . Hereby the electrical power system analysis is very important for practical use of HTS devices. Nowadays PSCAD/EMTDC simulation tool is one of the most popular and useful analysis tool for the electrical power system analysis. Unfortunately the model component for HTS power cable is not provided in the PSCAD/EMTDC simulation tool In this paper. the EMTDC model component for HTS power cable has been developed considering critical current, critical temperature and recovery time constant that depend on the sorts of HTS wire. The numerical model of HTS Power cable in PSCAD/EMTDC was designed by using the real experimented data obtained from the real HTS 1G wire test. The utility application analysis of HTS power cable was also performed using the developed model component and the parameters of the real utility network in this study. The author's got good results. The developed model component for HTS power cable could be variously used when the power system includes HTS power cable, especially it will be readily analyzed by PSCAD/EMTDC in order to obtain the data for the level of fault current power flow, and power losses, and so on.

• Journal of Korean Society for Quality Management
• /
• v.21 no.2
• /
• pp.109-120
• /
• 1993

Most systems are composed of components which have different failure chracteristics. Since the failure characteristics of components is different, it is rational and reasonable to establish a maintenance model to be considered repair and replacement policies which are proper to failure characteristics of these components. This paper proposes the age replacement time for a system composed of components which have different failure characteristics. In this model, it is assumed that a system is composed of a critical failure component, a major failure component, minor failure component. If any failure occurs to critical component before its age replacement time, the system should be replaced. If any failure does not occur until its age replacement time, preventive replacement should be performed at age replacement time T. Major component is minimal repaired if any failure occurs during operation. Minor component should be replaced as soon as failure is found. This paper determines the optimal replacement time of the system which minimize, total maintenance cost and initial stock Quantity of minor component within this optimal replacement time. Numerical example illustrates these results.

• Computational Structural Engineering : An International Journal
• /
• v.1 no.1
• /
• pp.71-80
• /
• 2001

A reliability approach to evaluate structural performance has gained increased acceptability and usage over the past two decades. Most reliability analyses are based on the reliability of an individual component without examining the entire structural system. These analyses often result in either unnecessary repairs or unsafe structures. This study uses examples of series, parallel, and series-parallel models of structural systems to illustrate how the component reliabilities affect the reliability of the entire system. The component-system reliability interaction can be used to develop optimum lifetime inspection and repair strategies for structural systems. These examples demonstrate that such strategies must be based on the reliability of the entire structural system. They also demonstrate that the location of an individual component in the system has a profound effect on the acceptable reliability of that component. Furthermore, when a structure is deteriorating over time, the reliability importance of various components is a1so changing with time. For this reason, the most critical component in the early life of the structure may not tie the most critical later.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2004.09a
• /
• pp.201-209
• /
• 2004

As the European Community's Directive on the Restriction of Hazardous Substances in Electrical and Electronic Equipment banning lead (Pb) in electronics products will take effect on July 1, 2006, most electronics manufacturers will be commencing with volume production of Pb-free components by the middle of 2004. Electrodeposited pure tin finishes on electronic components are a leading contender to replace the industry standard tin-lead. Commensurate with this shift will be a somewhat steep learning curve as manufacturers adapt a variety of equipment and processes to contend with the issues surrounding this critical, industry-wide material conversion. Since the electrodeposited finish directly influences the critical reliability characteristics of the component itself, the nature of the Pb-free component finish must be well characterized and understood. Only through a thorough examination of the attributes of the electroplated tin deposit can critical decisions be made regarding component finish reliability. This paper investigates the properties of electrodeposited tin that may have an effect on component reliability, namely, grain structure (size and shape), oxide formation, tin whisker formation, and solderability. Data will be presented from laboratory and production settings, with the objective being to enable manufacturers to draw their own conclusions regarding previously established perceptions and misconceptions about electrodeposited tin properties.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.18 no.6
• /
• pp.762-770
• /
• 2015

Fault tolerance is a crucial design for a mission-critical computer such as engagement control computer that has to maintain its operation for long mission time. In recent years, software fault-tolerant design is becoming important in terms of cost-effectiveness and high-efficiency. In this paper, we propose MPCMCC which is a model-based software component to implement fault tolerance in mission-critical computers. MPCMCC is a fault tolerance design that synchronizes shared data between two computers by using the one-way message-passing scheme which is easy to use and more stable than the shared memory scheme. In addition, MPCMCC can be easily reused for future work by employing the model based development methodology. We verified the functions of the software component and analyzed its performance in the simulation environment by using two mission-critical computers. The results show that MPCMCC is a suitable software component for fault tolerance in mission-critical computers.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.11 no.18
• /
• pp.35-39
• /
• 1988

In general, the characteristics of components which consist of multi component system can not be the same. This paper proposes a maintenance model of multi-component system according to the characteristics of each component. In this paper multi-component system is divided into three components-critical component, major component and minor component, respectively. Then we determine the optimal age replacement time of the system which minimizes total maintenance cost. Numerical examples are shown to illustrate the result.

• Journal of the Korea Society of Computer and Information
• /
• v.27 no.12
• /
• pp.285-292
• /
• 2022

This study examined the effects of professionalism and critical thinking disposition on job competency in nursing service workers. Furthermore, we explored the interactive impact of critical thinking disposition in terms of component factors in the relationship between the influence of professionalism on job performance. Our research results were as follows. First, we found that the self-concept of the profession and originality of the job in the professional view has a significant effect on job performance. Second, we discovered that systematicity and objectivity in the critical thinking disposition significantly affect job performance. Third, we found an interaction effect between each component of professionalism and critical thinking disposition. This study is significant because it is approached from the perspective of components of professionalism and the critical thinking disposition to improve job performance. In addition, the results of this study will contribute to the management of professionalism and essential dispositions of thinking to enhance nursing service workers' job performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.05a
• /
• pp.483-488
• /
• 2003

Frictional heating in brakes causes thermoelastic distortion of the contacting bodies and hence affects the contact pressure distribution. The resulting thermo-mechanical coupling can cause thermoelastic instability (TEI) if the sliding speed is sufficiently high, leading to non-uniform heating called hot spots and low frequency vibration known as hot judder. The vibration of brakes to the known phenomenon of frictionally-excited thermoelastic instability is estimated studying the interface temperature and pressure evolution with time. A simple model has been considered where a layer with half-thickness ${\alpha}$ slides with speed V between two half-planes which are rigid and non-conducting. The advantage of this properly simple model permits us to deduce analytically the critical conditions for the onset of instability, which is the relation between the critical speed and the growth rate of the interface temperature and pressure. Symmetrical component of pressure and temperature distribution at the layer interfaces can be more unstable than antisymmetrical component. As the thickness ${\alpha}$ reduces, the system becomes more apt to thermoelastic instability. Moreover, the evolution of the system beyond the critical conditions has shown that even if low frequency perturbations are associated with low critical speed, it might be less critical than high frequency perturbations if the working sliding speed is much larger than the actual critical speed of the system.