• Communications of the Korean Mathematical Society
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• v.20 no.2
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• pp.351-358
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• 2005

We study asymptotic equivalence between nonlinear difference system $$\Delta\chi(n)=f(n,\chi(n))$$ and its variational system $${\Delta}v(n)=f_{\chi}(n,0)v(n)$$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10A
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• pp.788-795
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• 2003

We analyze the performance of a truncated power controlled CDMA(code division multiple access) cellular systems with base station antenna arrays. Erlang capacity and the channel capacity which is a maximum date rate to maintain almost error free communication are analytically derived. The numerical results show there can be a substantial increase in Erlang capacity and in channel capacity by antenna arrays incorporating with the truncated power control scheme.

• Communications for Statistical Applications and Methods
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• v.11 no.3
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• pp.447-454
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• 2004

In this paper, we consider the bootstrap method to the interval estimation of the difference of quantiles of right censored data. We showed the validity of bootstrap method and compare with others with real data example. In simulation various resampling schemes for right censored data are also considered.

• Journal of the Korean Statistical Society
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• v.32 no.1
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• pp.25-32
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• 2003

In this paper, we define the mean life process for the right censored data and show the asymptotic equivalence between two kinds of the mean life processes. We use the Kaplan-Meier and Susarla-Van Ryzin estimates as the estimates of survival function for the construction of the mean life processes. Also we show the asymptotic equivalence between two mean residual life processes as an application and finally discuss some difficulties caused by the censoring mechanism.

• 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.

• Journal of Korean Society of Transportation
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• v.10 no.3
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• pp.43-58
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• 1992

The purpose of this study is to analyse the changes in inter-regional accessibility according to the highway construction. Accessibility of the physical distance(APD), accessibility of the time distance(ATD) and accessibility of the weighted physical distance(AWPD), accessibility of the weighted time distance(AWTD) are used as accessibility index. The result shows that APD, ATD, AWPD and AWTD are improved in the Chechon, Sangju, Chomchon region by the construction of Chongju-Sangju Highway and Taegu-Chunchon Highway. Taechon, Sosan, Kunsan region also improved by the construction of Sohaean Highway and Konju-Sohaean Highway.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.1
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• pp.67-72
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• 1987

InSb TFT is fabricated by the vacuum evaporation method and I-V characteristics are measured. Employing Davidon Fletcher-Powell algorithm, the device parameters are extracted. The current-voltage relations calculated by extracdted parameters are in good agreement with experimental results. It is found that optimization technique may be more simple and accurate than curve fitting method in device parameters extration.

• Analytical Science and Technology
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• v.18 no.2
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• pp.112-119
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• 2005

This study reports on the efficiency of cleaning enameled magnet wire using a sulfuric acid $H_2SO_4$ and removal of dissolved organic material using hydrogen peroxide $H_2O_2$ and nitric acid $HNO_3$ at $80^{\circ}C$. The method involves the addition of pure $H_2SO_4$ and $H_2O_2$ or $HNO_3$. Layers of enameled organic material were dissolved by 90% $H_2SO_4$ and the solution was maintained as 35% $H_2O_2$ or 60% $HNO_3$. $H_2O_2$ content in aqueous $H_2O_2$ was maintained as 8.8 : 1.0. An initial concentration of $H_2SO_4$ in dissolution conditions was accomplished within 15 min, with a stripping time of about 2 h. The concentrations of $H_2O_2$ and $HNO_3$ in the processing bath were relatively low, but sufficient enough to produce an effective amount of power in the bath for the removal of the enamel material. The cleaning effect of enameled organic material involves the dehydration by $H_2SO_4$ and the oxidation by $H_2O_2$ or $HNO_3$.

• Journal of the Korean Society of Safety
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• v.22 no.4
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• pp.57-65
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• 2007

Effects on the stiffness of the embankment and sandmat on the construction safety of road embankment was investigated in this study by the numerical experiments using FEM. Two points was mainly focused in this study especially. First the deformation characteristics by the change of the stiffness of sand mat and embankment was investigated by the analyzing the consolidation settlement at the center of the embankment and the lateral displacement at the toe of the embankment. And, the effect of the stiffness on the stress distribution characteristics was also investigated in this study. Furthermore, slope stability analysis was carried out to gain the safe factor by change the stiffness of the sandmat and the embankment. The objective of the study is supplying the result of the numerical experiments for the geotechnical engineers who use the FEM for the safety design of the soil structures. As a result, the stiffness of the superstructures greatly affects on the deformation characteristics both in consolidation settlement and lateral displacement. However, it can be aware that it is not dominants to the stress distribution in the aspect that the no changes in the residual excess pore water pressure. Therefore, the decision of the stiffness has to be carried out deliberately considering not only the consolidation the magnitude of the settlement and the lateral displacement, but the slope stability.

• Korean Journal of Human Ecology
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• v.8 no.1
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• pp.179-192
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• 1999

The purposes of this study were to investigate the needs for the educational subjects of practitioners in apparel distribution industry and to examine the relationship between the needs and their socio-demographic variables. And it was intended to be used as basic data to develop the curriculum for continuing education in university. The subjects were consisted of 473 practitioners in apparel distribution industries in Taejon and Chongju. A questionnaire was used and classified into seven areas--basic area textile science, design, clothing construction, fashion marketing theory, fashion marketing practice and business management. Descriptive analysis, t-test and ANOVA were used for statistical analyses. The results of this study were as follows: First, the educational needs of subjects by practitioners were in the following order: 1)fashion marketing practice, 2)design, 3)fashion marketing theory, 4)business management, 5)clothing construction, 6)textile science, 7)basic area. Second, the educational needs of subjects by practitioners were also related to their socio-demographic variables like educational background, work area, type of market, total work experience, years in present job, and the role. It was implied that subject areas like fashion marketing and design with theory and practice we of most importance for practitioners in apparel distribution industry. Therefore, a university curriculum of continuing education for them should take into account of those factors mentioned above.