• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.163-168
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• 2006

In a micro-unit of electronic-machine, vibration can be excited by a small impact, and this vibration acts as a fatigue load. To measure the vibration effect on the micro unit, a micro dynamic tester is needed to test a micro specimen. In this paper, it has confirmed a movement of the PZT(piezo actuator) to use a sine signal. And, it has confirmed a fracture of specimens by using a tension-tension input signal in PZT. A metal-material property in the micro scale has been tested to compare with the macro scale. A fatigue test has been conducted by using PZT actuator to give a bending-tension effect.

• 한국경영과학회지
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• 제23권2호
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• pp.201-217
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• 1998

This paper attempts to show how DEA(data envelopment analysis), a nonparametric productivity analysis method, can be employed for insurance companies to improve their respective efficiencies and competitiveness. Specifically, we measured relative technical efficiencies and returns to scale of 11 Korean property-liability insurance companies using BCC model, and raised several issues including the cause of inefficiency, benchmarking toward reference set and resource allocation concerning the insurance companies. Also, in order to monitor the variability of the research results over periods, we employed longitudinal analysis to see the moving patterns of technical efficiencies, returns to scale and frequencies included in the reference set of the individual insurance companies under consideration. The methodology and the results in this paper may also serve as a useful guideline for individual insurance companies to set their respective business strategies.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.311-318
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• 2000

In constructions of dams and ports structure, gravels are used as principle structural materials. Gravels have different material property compared with other materials like soil and concretes, etc. For example, material properties of gravels obtained from normal triaxial compression test are usually overestimated due to scale and penetration effects. Also, material properties of gravels under dynamic loads are the main interest when structural behavior of rockfill dam under earthquake loads is analyzed. The development of large triaxial compression apparatus is needed for the better estimation of material property of gravel. This paper reports work in progress to development of large triaxial compression apparatus.

• 대한전자공학회논문지
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• 제20권3호
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• pp.45-51
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• 1983

본 논문에서는 대규모 시스템을 위한 준최적 저감도성 비집중형 제어기를 설계하기 위하여 준최적 이득 행렬을 구하기 위한 필요조건과 알고리즘을 유도하였다. 또한 감도를 고려하지 않은 종래의 비집중제어기와의 비교를 위하여 수치적 예를 들어 보였다.

• 한국의류학회지
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• 제23권8호
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• pp.1139-1148
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• 1999

This paper discussed the assessment of hand of denim fabrics finished by enzymatic hydrolysis. The semantic differential scale established using the database collected from university students. Analyzing the subjective rating by common factor analysis with oblimin rotation five factors expressing the hand were induced. Factor one was the surface property related to the surface roughness or softness Factor two was the durability which was related to the compactness and bearing strength Factor three was the sense of weight which was related to the thickness and weight. The moisture related properties and the sense of shape recovery were the forth and fifth factors respectively. the evaluations on the surface property weight and moisture related properties were similar by men and women However the shape recovery and the durability were evaluated differently. Surface and weight related properties were important factors judging the hand of fabrics by both group.

• Communications for Statistical Applications and Methods
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• 제25권1호
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• pp.79-89
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• 2018

In this paper, we study the maximal property of the volume of the convex hull of d-dimensional independent random vectors. We show that the volume of the random convex hull from a multivariate location-scale family indexed by ${\Sigma}$ is stochastically maximized in simple stochastic order when ${\Sigma}$ is diagonal. The claim can be applied to a broad class of multivariate distributions that include skewed/unskewed multivariate t-distributions. We numerically investigate the proven stochastic relationship between the dependent and independent random convex hulls with the Gaussian random convex hull. The numerical results confirm our theoretical findings and the maximal property of the volume of the independent random convex hull.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.217-222
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• 2004

The aim of this paper is to investigate the effect of micro-dimple size on reduction friction and to understand the potential of friction reduction through micro-scale dimple to fabricate by photolithography on pin-on-disk test using flat-on-flat contact geometry. It was verify that the friction property with respect to the same pitch has been influence on the size of dimple under lubricated sliding contact. Also, we can recognize from Stribeck curve that the friction property has a connection with the size of dimple. It can explain a relationship between the friction coefficient and a dimensionless parameter for lubrication condition. The friction property has been an effect on the size of surface texture on reduction friction, not only because the density of dimple, but also because the ratio of diameter/pitch. This ratio of approximately 0.5 is recommend under the tested friction condition. It suggested that the ratio of d/p is an important parameter for surface texture design.

• 한국자동차공학회논문집
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• 제8권1호
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• pp.135-147
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• 2000

Section design of vehicle structure has been developed by two methods. One is the section property method which uses section property as a design variable. This method shows the tendency of an optimum section approximately. The other method is the section shape method which utilizes geometric parameter of section as a design variable. Practical solutions are obtained by this method. However, it is very expensive for large-scale problems due to the large number of geometric parameters. These two methods are compared through several sample problems. The finite element method is used for the structural and sensitivity analyses. The results are analyzed based on the number of function evaluations, the quality of cost function, the complexity of programing, and etc. The applications of both methods are also discussed.

• 소성∙가공
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• 제14권6호
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• pp.509-513
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• 2005

This paper is concerned with manufacturing technology of thin foil tensile specimen using CIP(Cold Isostatic Press) and measurement of precision mechanical properties using micro tensile testing. We can get a burr free micro metallic thin foil specimen using this technology. For testing mechanical property of this micro thin foil, we use a nano scale material testing machine that was developed by KITECH. In this paper, micro tensile specimens of nickel and copper thin foil are fabricated with CIP and precision mechanical properties of these materials could be measured. We will expect precision mechanical property of micro/nano material and component.

• 대한기계학회논문집B
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• 제20권9호
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• pp.3015-3029
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• 1996

The notion of effective transport property of a heterogeneous medium implies that the medium is large enough that the ergodic theorem holds and local fluctuation of the property can be neglected. In case that the medium is not large enough compared to its characteristic microstructure length scale, the effective property fluctuates and differs from the value of the medium being large enough. As a representative transport phenomenon, diffusion was considered and the fluctuation of varying effective diffusion property, diffusion coarseness $C_k$, was defined as a quantifying parameter. Scaled effective diffusion property, $^*$>/k$_1$ and $C_k$ were computed for the two phase random media consisting of matrix of diffusion coefficient k$_1$ and spheres of diffusion coefficient k$_2$. Numerical simulations were performed by use of the so-called first passage time technique and data were collected for existing microstructure models of hard spheres(HS), overlapping spheres(OS) and penetrable concentric shells(PCS).