• 한국정밀공학회지
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• 제9권4호
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• pp.44-57
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• 1992

Ball screw systems have been used for positioning elements of machine tools and precision tables. In order to maintain the high rigidity and accuracy, a certain amount of preload is applied between the nut and the screw of ball screw systems. However, large amount of the preload oncreases the frictional heat. The temperature rises remarkably at the high speed motion, and the thermal expansion degrades the positioning accuracy. In this paper, a finite difference method is applied to analyse temperature distributions and thermal expansions of the ball screw system according to preload conditions and rotational speeds. Some simulation results show that the developed methodology is appropriate to study the thermal expansion characteristics of ball screw systems.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.7-11
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• 2008

Future electric lights will be composed of white LEDs (Light Emitting Diodes). Indoor wireless optical communication systems utilizing white LED lights have been studying about it. Generally, plural lights are installed in room. Therefore, their optical path difference must be considered. In this paper, the influence of an optical path difference has been investigated and two approaches against this problem are introduced. One uses OOK-RZ (On-Off Keying, Return-to-Zero) coding and the other uses optical OFDM (Orthogonal Frequency Division Multiplexing). From the results of computer simulations, we have found that these approaches are feasible for the wireless optical communication systems utilizing white LED lights.

• International Journal of Aeronautical and Space Sciences
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• 제18권4호
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• pp.816-826
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• 2017

In this paper, a generalized discretization scheme is proposed that can derive general-order finite difference equations representing the joint probability density function of dynamic response of stochastic systems. The various order of finite difference equations are applied to solutions of the Fokker-Planck-Kolmogorov (FPK) equation. The finite difference equations derived by the proposed method can greatly increase accuracy even at the tail parts of the probability density function, giving accurate reliability estimations. Compared with exact solutions and finite element solutions, the generalized finite difference method showed increasing accuracy as the order increases. With the proposed method, it is allowed to use different orders and types (i.e. forward, central or backward) of discretization in the finite difference method to solve FPK and other partial differential equations in various engineering fields having requirements of accuracy or specific boundary conditions.

• 충청수학회지
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• 제20권3호
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• pp.311-320
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• 2007

We obtain a discrete analogue of Nohel's result in [5] about asymptotic equivalence between perturbed Volterra system and unperturbed system.

• 전기의세계
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• 제19권5호
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• pp.1-7
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• 1970

Starting from the review of signal flow graphs and flow graphs, this paper gives an example of sampled-data systems for Sedlar & Bekey's formulation. In this purpose it discussed the difference between Mason's signal-flow graphs and Coates flow graphs for drawing th flow graph of a linear system, and then a new flow-graph symbol introduced in order to distinguish between continuous and discrete systems. Thus, the paper is analysed and compared with a sampled-data systems between conventional methods and new method of signal flow graphs.

• 경영과정보연구
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• 제32권2호
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• pp.47-58
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• 2013

본 연구는 부산에 소재하는 한 대학병원의 건강검진센터에서 건강검진을 받은 이용자들의 검진금액에 대해 성별, 연령별, 지역별로 차이가 있는지를 분석하였으며 그 결과는 다음과 같이 요약할 수 있다. 첫째, 성별 분석의 경우 남성과 여성간의 검진금액에는 차이가 없는 것으로 나타났다. 둘째, 연령별 분석의 경우 50 60대의 연령군이 건강검진을 위해 가장 많은 금액을 지불하고 있는 것으로 나타났으며, 사후 검증과 집단별 검증을 추가로 한 결과 30대 미만과 30대 그리고 60대와 70대 이상의 연령군을 제외한 연령군에서 유의적인 차이를 보였으며, 집단별로는 40대 미만집단, 40대 집단 50대 이상 집단의 3개 집단 간 유의적이 차이를 보여 검진금액에 대한 연령집단군별 차이가 있는 것으로 나타났다. 셋째, 검진금액에 대한 지역별 차이분석에 대한 사후 검증 결과 부산과 울산 경남 지역만 통계적으로 유의한 차이를 보여주었을 뿐 나머지 지역 간에는 통계적으로 유의한 차이를 제시하지 못하였다. 이러한 연구 결과는 의료기관의 건강검진 센터의 효율적 운영에 대한 기초적 정보를 제공할 수 있을 것이다.

• 한국정보시스템학회지:정보시스템연구
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• 제27권3호
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• pp.81-102
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• 2018

Purpose The purpose of this study is to investigate the reason why smartphone users do not use mobile banking based on Status Quo Bias and to find out whether there is a difference between passive resistance and active resistance. Design/methodology/approach This study made a design of the research model based on Status Quo Bias. SPSS 23.0 and SmartPLS 2.0 were used for the analysis. Multiple group analysis was performed to identify differences between groups. Findings According to the empirical analysis result, this study confirmed that inertia and perceived risk affected smartphone users who do not use mobile banking. According to the type of resistance, the active resistance group(64.2%) was more than the passive resistance group(35.8%), and it was confirmed that there was a difference in the reasons for not using mobile banking between passive and active resistance group. That is, the greatest difference between passive and active resistance groups was found to be perceived risk, which is an assessment of risk.

• 경영과정보연구
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• 제13권
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• pp.71-97
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• 2003

As an electronic commerce grows in a rapid speed today, it has a great effect on not only our consuming lives but also the marketing activities. The study on involvement levels and consumer satisfaction in physical market in the existing studying papers in home was made progress rapidly. But, the study on involvement levels and consumer satisfaction in virtual market leaves much to be desired. This paper aims at considering the relationship between the involvement levels and the consumer satisfaction factors in the electronic commerce through the internet shopping mall whose importance is emphasized day by day. In this paper, three following questions were studied: (1) what is the difference among the factors(product/service/image) of consumer's satisfaction in accordance with consumers' involvement levels, (2) what is the difference in an intention of repurchase in accordance with the consumers' satisfaction factors, and (3) what is the difference in an intention of repurchase in accordance with the involvement levels and the consumers' satisfaction factors. As a result of analysis, only the service one of the factors of consumer's satisfaction has a difference in accordance with high/low involvement, and also, the factors which have an effect on the intention of repurchase were product, service and image.

• Journal of applied mathematics & informatics
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• 제31권1_2호
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• pp.277-284
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• 2013

In this paper, we investigate $h$-stability of the nonlinear perturbed difference system via $n_{\infty}$-similarity.

• 대한수학회보
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• 제44권1호
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• pp.177-184
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• 2007

We study the asymptotic behavior of nonlinear Volterra difference system $$x(n+1)=f(n,x(n))+{\sum\limits^{n}_{s=n_{o}}\;g(n,s,x(s)),\;x(n_{o})=xo$$ by using the resolvent matrix R(n, m) of the corresponding linear Volterra system and the comparison principle.