• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.109-114
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• 2003

It is the common practice to reinforce excessively the secondary tunnel lining due to the lack of rational insights into the ground loosening loads. The main load of the secondary lining for drained-type tunnels is the ground loosening. The main cause of the load for secondary tunnel lining is the deterioration of the primary support members such as shotcrete, steel ribs, and rockbolts. Accordingly, the development of the analysis model to consider the ground-primary supports-secondary lining interaction is very important for the rational design of the secondary tunnel lining. In this paper, the interaction is conceptually described by the simple mass-spring model and the load transfer from the primary supports to the ground and the secondary lining is showed by the characteristic curves including the secondary lining reaction curve for the theoretical solution of a circular tunnel. And also, the application of this model to numerical analysis is verified in order to review the potential tool for practical tunnel problems with the complex conditions like non-circular shaped tunnels, multi-layered ground, sequential excavation and so on.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1710-1712
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• 1996

This paper was practiced insulation failure test forcing to accelerate on frequency of 420 HZ. There was manufactured generator stator windings for 500MVA thermal plants and selected accelerating deterioration voltage of 5.5kV/mm for electrical aging. Moreover, so as to verification of this experiments, we carried out modeling analysis due to finite element method using to ANSYS5.0 program for common package and imitated multi-stress aging for analyzing electrical and mechanical stress distribution.

• 한국안전학회지
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• 제24권2호
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• pp.1-6
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• 2009

침식마모로 인하여 손상되어 차량화재를 유발한 차량용 워터펌프의 성능저하를 CFX프로그램을 이용하여 해석하였다. 손상에 따른 성능저하를 해석하기 위하여, 블레이드의 굽힘 변형과 간극의 증가를 고려하였다. 캐비테이션 해석 시에는 포화증기 발생과 응축 과정을 모델링하기 위하여 Rayleigh-Plesset 모델을 적용하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.289-292
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• 2007

To prevent the damage of glass lens molds and deterioration of glass lenses using in progressive GMP process, a thermal stress and a deformation of the glass lens molds at forming temperature should be considered in the design step. In this study, as a fundamental study to develop a multi cavity mold used in an aspheric glass lens molding, a heat transfer and a thermal stress analysis were carried out for the case of one cavity glass lens mold used in progressive GMP process. Finally, using analysis results, we estimated the thermal stress in a glass lens mold and predicted a modified height of guide ring that determines the forming height of a glass lens.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.1001-1006
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• 2004

Railroad disasters are frequently occurred by man-made causes or natural causes. In general, man-made causes are illegal construction practices, deterioration with the lapse of time and railroad crossing accidents, and natural causes are rainfall. snow, wind, earthquake, etc. Of cause, railroad disasters by man-made causes are prevented from keeping the safety principle, constructing multi-level crossing, securing enough men of ability and financial resources and making a thorough check using equipments with high capacity. And railroad disasters by natural causes are also minimized by construction of disaster prevention facilities, introduction and operation of general disaster prevention system and reasonable train passage control. Therefore, to setup the criterion of train passage control for train safety at railroad bridge under heavy rainfall, risky factors, national and oversea criteria under such circumstances are reviewed and a scheme to setup the criterion is suggested.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.417-422
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• 2002

One of the major limitations of productivity and quality in metal cutting is the machining accuracy of machine tools. The machining accuracy is affected by geometric errors, thermally-induced errors, and the deterioration of the machine tools. Geometric and thermal errors of machine tools should be measured and compensated to manufacture high quality products. In metal cutting, the machining accuracy is more affected by thermal errors than by geometric errors. In this study, the compensation device and temperature-based algorithm have been implemented on the machining center in order to compensate thermal error of machine tools under the real-time. The thermal errors are predicted using the neural network and multi-regression modeling methods. In order to compensate thermal characteristics under several operating conditions, experiments performed with five gap sensors and manufactured compensation device on the horizontal machining center.

• Steel and Composite Structures
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• 제10권4호
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• pp.331-348
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• 2010

Ample research effort has been oriented into developing damage indices with the aim of estimating in a reasonable manner the consequences, in terms of structural damage and deterioration, of severe plastic cycling. Although several studies have been devoted to calibrate damage indices for steel and reinforced concrete members; currently, there is a challenge to study and calibrate the use of such indices for the practical evaluation of complex structures. The aim of this paper is to introduce an energy-based damage index for multi-degree-of-freedom steel buildings that accounts explicitly for the effects of cumulative plastic deformation demands. The model has been developed by complementing the results obtained from experimental testing of steel members with those derived from analytical studies regarding the distribution of plastic demands on several steel frames designed according to the Mexico City Building Code. It is concluded that the approach discussed herein is a promising tool for practical structural evaluation of framed structures subjected to large energy demands.

• 산업경영시스템학회지
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• 제10권16호
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• pp.113-119
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• 1987

다단계 생산-재고문제에 관하여 일반적인 해법으로서 Dynamic Programming이 이용되고 있으나 C. L. Hwang과 L. T. Fan은 Pontryagin의 최대원리에 의해 보다 효율적인 방법을 제시하였다. 본 연구는 상기의 문제를 제품의 진부화가 있는 모델로 확장하여 난산형 최대원리를 적용하는 것으로서, 특히 수요 및 진부화율이 기간마다 변화하는 다단계 생산-재고시스템에 있어서의 최적 생산-재고정책을 수립하는 효율적인 앨고리듬을 제시한다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1999년도 유체기계 연구개발 발표회 논문집
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• pp.46-51
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• 1999

This paper describes the control charcteristics of thermal/flow systems. In thermal/flow systems, the transport lag plays as a dead time causing a deterioration of the controllability. Besides this, such many parameters including the temperature, pressure, and flow rate affect the system response that a control scheme which can deal with multi-input is required. Particularly in a refrigerant compressor test facility, the evaporator and condenser interact each other so that the change in the evaporator pressure cause the condenser pressure to change or vice versa. Therefore, to control the evaporator pressure, not only the cooling water flow rate in the evaporator but also the coolant flow rate in the condenser is considered. Meanwhile, the conventional PID controllers, which is suitable for a single input system, shows a large overshoot for a disturbance input. In this work, the predictive control scheme is introduced and its applicability is discussed for thermal/flow systems.

• Structural Engineering and Mechanics
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• 제78권3호
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• pp.281-296
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• 2021

This article analyzed the modulus degradation of concrete subjected to multi-level compressive cyclic loading. The evolution of secant elastic modulus is investigated based on measurements from top loading platen and LVDT in the middle part of concrete. The difference value of the two secant elastic moduli is reduced when close to failure and could be used as a fatigue failure precursor. The fatigue hardening is observed for concrete during cyclic loading. When the maximum stress is smaller the fatigue hardening is more obvious. The slight increase of maximum stress will lead to the "periodic hardening". The tangent elastic modulus shows a specific "bowknot" shape during cyclic loading, which can characterize the hysteresis of stress-strain and is influenced by the cyclic loading stresses. The deterioration of secant elastic modulus acts a similar role with respect to the P-wave speed during cyclic loading, can both characterize the degradation of the concrete properties.