• Journal of Korean Society for Quality Management
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• v.21 no.1
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• pp.108-120
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• 1993

In this article an economic life test sampling plan is considered for repairable products when the products in each lot have the same interfailure time distribution, but the mean time between failure (MTBF) of a lot varies from lot to lot according to a known prior distribution. A cost model is constructed which consists of test cost, accept cost, and reject cost. Determination of the optimal plan which minimizes the expected average cost per lot is discussed. Numerical examples are presented to illustrate the use of the proposed sampling plans and sensitivity analyses for parameters of the prior distribution are performed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.7 s.238
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• pp.921-929
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• 2005

This paper presents an accelerated life test for burnout of tungsten filament of incandescent lamp. From failure analyses of field samples, it is shown that their root causes are local heating or hot spots in the filament caused by tungsten evaporation and wire sag. Finite element analysis is performed to evaluate the effect of vibration and impact for burnout, but any points of stress concentration or structural weakness are not found in the sample. To estimate the burnout life of lamp, an accelerated life test is planned by using quality function deployment and fractional factorial design, where voltage, vibration, and temperature are selected as accelerating variables. We assumed that Weibull lifetime distribution and a generalized linear model of life-stress relationship hold through goodness of fit test and test for common shape parameter of the distribution. Using accelerated life testing software, we estimated the common shape parameter of Weibull distribution, life-stress relationship, and accelerating factor.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.4
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• pp.256-260
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• 2015

In this paper, achieved rise temperature distribution about degradation phenomenon of 24 MVA distribution cast resin transformer using CFD(Computational Fluid Dynamics). Usually, life of transformer is depended on temperature distribution of specification region than thermal special quality of transformer interior. Specially, life of transformer by decline of dielectric strength decreases rapidly in case rise by strangeness transformer interior hot spot temperature value permits. Because calculating high-voltage(HV) winding and low-voltage(LV) winding of cast resin transformer and Joule's loss of core for improvement these life, forecasted heat source, and HV winding and LV winding of cast transformer rise temperature distribution of core for supply of electric power and temperature distribution of highest point on the basis of the results. Also, calculated temperature rise limit of cast resin transformer and permission maximum temperature using analysis by electromagnetic heat source. Calculated and forecasted rise temperature distribution by heat source of thermal analysis with calculated result.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.10
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• pp.49-55
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• 2008

This paper presents a novel evaluation method of life expectancy of power system equipment. The life expectancy means expected remaining lifetime; it can be usefully utilized to maintenance planning, equipment replacement planning, and reliability assessment. The proposed method is composed of three steps. Firstly, a cumulative probability for future years is evaluated for targeted age year. Secondly, the cumulative probability is modeled by well-blown cumulative distribution function(CDF) such as Weibull distribution. Lastly, life expectancy is evaluated as the mean value of the model. Since the model CDF is established in the proposed method, it can also evaluate the probability of equipment retirement within specific years. The developed method is applied to examples of generators of combined cycle power plants to show its effectiveness.

• The Journal of Industrial Distribution & Business
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• v.10 no.10
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• pp.7-13
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• 2019

Purpose - This study is to verify the mediating effect of voluntariness in retirement and the moderating effects of leisure life to examine which parts of later life preparations have influence on the retired life. Research design, data, and methodology - In this study, the 6^th Korean Retirement and Income Study was conducted on 5,254 members of households with householders over the age of 50. To examine the relationship between later life preparation and retired life, this study used personal data based on the serial number of the household members. Results - First, physical preparation for later life had a positive influence on retired life satisfaction among retirement satisfaction. People showed higher retired life satisfaction. Secondly, physical preparation for later life had a positive influence on satisfaction over relationship after retirement among retirement satisfaction. People showed higher satisfaction over relationship after retirement when they were more physically prepared for later life. Conclusions - In particular, leisure life had a mediating effect for the influence of physical preparation for later life on the retired life. Also, leisure life and physical preparation for later life showed a close influencing relationship. People showed active leisure life and higher retired life satisfaction when they were more physically prepared for later life.

• Journal of Korean Society of Steel Construction
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• v.10 no.1 s.34
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• pp.37-45
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• 1998

The relational database system on fatigue strength was constructed, and the properties of fatigue life distribution were examined to analyze reliability and safety of metallic materials. Data manipulations were efficiently performed in relational fatigue strength database system using dependency diagram. Regardless of the distribution of fatigue strength, the proposed method, the Robust method and the complementary error function method using probability distribution, successfully estimated parameters of the 3-parameter Weibull distribution. The proposed criterion for estimating non-failure probability showed good results regardless of censoring time. The fatigue life distribution function described as a function of parameters of the Weibull distribution and applied stress ratio produced P-S-N characteristics reasonably.

• Journal of Applied Reliability
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• v.8 no.2
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• pp.75-85
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• 2008

In this paper, we compared domestic with foreign pilot lamps installed on the instrument board or electronic modules (car audio, air-conditional system, etc.) of an automotive vehicle by an accelerated life test in order to estimate the life of domestic pilot lamps. An accelerated life test method was developed and the relation of the life and voltage stress was analyzed. The main results are as follows; i) $B_{10}$ life of pilot lamp is above 5,000 hours, vehicle travel time for 10 years. ii) the life of domestic pilot lamp is longer than that of foreign thing. iii) the life distribution of domestic pilot lamp is wider than that of foreign thing. iv) it is possible to promote import replacement of automobile pilot lamp.

• KEPCO Journal on Electric Power and Energy
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• v.7 no.2
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• pp.241-248
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• 2021

High cycle fatigue life for the cables with two different types of clamps is estimated comparatively through acceleration testing. The high cycle fatigue fracture of overhead lines is caused mainly by the aeolian vibration which is induced by vortex shedding. It is necessary to manage the integrity of cables continuedly considering that the aeolian vibration is unavoidable since it occurs in steady and relatively low wind velocity. Two types of clamps which are largely used for overhead lines of the distribution grids are selected and failure data are obtained by step stress testing with a electrodynamic shaker with them. The inverse power law is assumed to describe the stress-life relationship and the fatigue limit at any specified life is supposed to follow Weibull distribution. The life of the cable is defined as the number of cycles to the time that one of strands is completely broken. Finally, the fatigue limits of the cables with two clamp types are estimated at the reference life of 500 Mcycles and compared each other based on a bending vibration amplitude.

• Journal of the Korean Geographical Society
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• v.36 no.3
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• pp.258-277
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• 2001

Agricultural Co-operation chain stores were highly the utility of distribution rationalization for commercial distribution by informatisation and by multi-polarizied of large physical distribution center of Inventory intensive type consisted of intensive physical distribution. and transportation of commodities from physical distribution center have act by outsourcing. Therefore, the methods of distribution of commodities of life and agricultural products are distinguished from route distribution and regular time collective distribution. the method of distribution is formated the distribution field b\ulcorner characteristic of commodity. On the other hand, spatial characteristics by sales activities of commodities was clarified by types of stole commodity according to level of paddy agriculture development and level of service industrial employment. But manufactured foodstuffs and miscellaneous goods. that is commodities of life clarified the fact selling that is not influenced by regional type.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.26 no.3
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• pp.165-171
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• 2020

Maintaining steady and low temperature during distribution process is a key technique to inhibit microbial growth, one of the most important factors in determining the shelf life. It is possible to provide high-quality fresh products to consumers only when precise and adequate temperature control is guaranteed throughout the entire distribution process for fresh seafood. This study investigated the shelf-life of packaged fresh flounder (Paralichthys Olivaceus) in order to learn the feasibility of super-chilled distribution of fresh seafood. To estimate the shelf life, weight, number of bacteria such as E. coli, pH, sensory test and volatile basic nitrogen were investigated. As a result of the study, the difference in shelf life of 6 days at the super-chilling temperature (0±1℃) and 1 day at the general refrigeration temperature (8±2℃) (based on volatile base nitrogen) showed the market possibility of super-chilling distribution. Through additional empirical studies such as packaging methods and economic feasibility, it is expected to promote commercialization of super-chilling containers and packaging system developed in the future and secure customer reliability.