• 소성∙가공
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• 제15권5호
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• pp.387-394
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• 2006

In order to see the effect of die deformation on the forming analysis of sheet metals, the draw-ins, strains, and spring-backs of an automotive fender panels are numerically simulated by considering the die deformation found by the simultaneous structural analysis of press and dies. By coupling the forming analysis and the structural analysis, the die deformation is simultaneously taken into account in the forming process. Furthermore, for the consideration of load difference transferred among the upper die, punch, and blank holder due to the changes in sheet thickness, the gap elements are employed instead of the blank sheet in the structural analysis. The numerical simulation results of an automotive finder draw panel are compared with the measurements. The comparison of the forming and spring-back analysis results between the rigid die and the deformed die shows that the consideration of tool deformation can predict more accurately the forming and spring-back of sheet metals.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 추계학술발표대회 논문집
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• pp.147-152
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• 2000

This paper presents the thermoelastic analysis and 3-D failure analysis of the carbon/carbon brake disk. The mechanical properties of the carbon/carbon brake disk were measured for both in-plane and out of plane directions. The mechanical properties were used as the input of the thermoelastic analysis and 3-D stress analysis for the brake disk. The gap between rotor clip and clip retainer was an important parameter in the loading transfer mechanism of the rotor. The change of gap was considered separating the mechanical deformation and thermal deformation. Because the rotor clip and clip retainers were not contacted, the clip retainers and rivets were excluded from the rotor analysis model. The disk was modeled by using the cyclic symmetry condition and the contact problem between the rotor disk and rotor clip was considered. From the results of the 3-D stress analysis, the stress concentration at the key hole of the brake disk was confirmed.

• 대한기계학회논문집A
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• 제39권3호
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• pp.249-257
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• 2015

원자력 발전소의 반응로에는 핵분열 에너지를 생성하고 방사성 물질의 유출을 막는 핵연료 집합체가 있으며, 이러한 집합체는 핵연료와 피복관으로 구성되어 있는 핵 연료봉으로 구성되어 있다. 원자로에서 핵연료봉 거동의 안전성을 평가하기 위해 해석적인 방법을 적용하며 이러한 평가 코드를 핵 연료 성능 코드라 한다. 경수로 핵연료 해석에서는 간극의 두께에 따라 열전도도가 크게 영향을 받는 간극 열전도도가 주요 거동해석에 영향을 미친다. 본 연구에서는 간극 두께에 따라 열전도도가 변화하는 3 차원 간극 요소(Gap element)를 제안하였으며, 이를 적용하기 위해 3 차원 열탄성 모듈을 FORTRAN90을 이용하여 개발하였다. 제안된 3 차원 간극 요소를 이용하여 핵 연료봉에서 발생할 수 있는 비대칭적인 형상인 핵 연료 표면에 결함이 생긴 경우 MPS(Missing Pellet Surface)와 핵연료봉의 편심(Eccentricity of the nuclear fuel rod) 형상에 대하여 3 차원 해석을 진행하였다.

• 공업화학
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• 제30권1호
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• pp.81-87
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• 2019

에너지화 열가소성 탄성체 제조에 사용될 수 있는 새로운 계열의 glycidyl azide polymer (GAP)을 모색하기 위해 전구체인 poly(epichlorohydrin) (PECH)에 친핵체인 아지드기와 알콕시 및 알킬 아민을 도입하여 4가지 GAP copolymer polyol을 합성하고 물성에 대하여 고찰하였다. 이 GAP copolymer 합성반응은 이종의 친핵체를 1단계 반응으로 동시에 치환하여 미반응 sodium azide가 남지 않는 친환경적이며 효율적인 합성법으로 평가할 수 있다. 역개폐 짝풀림(inverse gated decoupling) $^{13}C$ NMR 분석법과 Fourier transform infrared (FT-IR) 분석법으로 상대적 치환율을 정량적으로 분석하였으며 반응 진행도를 모니터링 하였다. 합성된 GAP copolymer의 유리전이온도와 분자량은 differential scanning calorimetry (DSC)와 gel permeation chromatography (GPC)로 분석하였다. 합성된 poly($GA_{0.8}-butoxide_{0.2}$), poly($GA_{0.7}-n-butylamine_{0.3}$), poly($GA_{0.7}-dipropylamine_{0.3}$), poly($GA_{0.7}-morpholine_{0.3}$)의 유리전이온도는 $-39^{\circ}C$에서 $-26^{\circ}C$ 범위의 값을 나타내었다.

• 대한영양사협회학술지
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• 제14권2호
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• pp.114-126
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• 2008

The purpose of this study was to gauge customers' satisfaction with the hospital, university, factory, and office foodservices from a contracted provider. Importance-performance analysis (IPA) evaluations were conducted. Questionnaires were returned from 1,808 customers in 46 foodservice locations. The average total scores of the importance and performance of seventeen quality characteristics were 4.14 and 3.23, respectively, on 5-point scales. The average total score of gap (gap = performance - importance) was -0.92. Analysis of significant difference according to the type of foodservices revealed that, hospital foodservices had more items with significant high scores than those of other groups in the average total scores concerning importance (p<0.01) and performance (p<0.01). The average total scores of gap showed no significant difference. Significant differences were evident in the food and personal service dimensions, and the scores of hospital foodservices trended significantly higher than those of other groups. Importance-performance analysis (IPA) analyses for hospital foodservice implicate 'variety of menu', 'cleanness of dishes', and 'taste of food' as items requiring prompt attention and improvement.

• 한국해양공학회지
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• 제33권6호
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• pp.504-509
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• 2019

The wave-generation performance of a piston-type wave maker was analyzed using the numerical wave tank technique, and the numerical results were compared with theoretical solutions. A two-dimensional frequency domain analysis was conducted based on the Rankine panel method. Various parameters were used to examine the wave-generation performance, such as the width and gap of the wave board. The effects of the thickness of the wave board and of the gap from the bottom of the tank were evaluated. The difference in the amplitude of the generated wave between the analytical solution and the numerical result was examined, and its causes were addressed due to the gap flow between the bottom of the tank and the wave board. This parametric analysis can be utilized to design an optimum wave make parametric analysis to design an optimum wave maker that can generate waves with amplitudes that can be predicted accurately.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1523-1525
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• 1996

Partial discharges(PD) in air insulated electric power systems cause power loss, produce interfering electromagnetic radiation, and can indicate incipient failure. An understanding of PD in air gap is clearly important. The Wavelet transformation is an extended method of fourier transformation. The fourier method is a powerful tool for signal analysis, but it can't include informations for time. However tile wavelet transformation analysis can include on the informations of time and frequency at the same time. In this paper we apply the wavelet transformation to the PD signals in needle-plane air gap for tile purpose of analysis of developing aspects of PD. We can analyze the developing aspects of PD, namely, PD current, repetition rates, width of pulse distribution region, pulseless region and frequencies distribution of PD pulses.

• 한국콘텐츠학회논문지
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• 제7권12호
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• pp.157-166
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• 2007

최근 행정기관의 정보화에 관한 연구들이 많이 발표되고 있으나, 실제 행정정보를 생산, 활용, 평가하는 공무원의 정보화 적응에 관한 연구는 미미한 실정이다. 정보화 과정에 있어서 공무원의 정보기술 적응은 정보화 투자와 더불어 업무의 효율성을 위해 매우 중요한 변수이다. 이러한 측면에서 본 논문은 지방공무원의 행정정보화 적응 부분을 조사하는 한편, 연구대상을 지방정부로 한정하였으나, 향후 중앙정부 차원의 연구를 진행할 수 있는 자료를 마련하고자 하였으며, 조사결과를 바탕으로 공무원의 정보화 교육에 대한 기초자료로 활용될 수 있을 것이다. 공무원의 정보화에 대한 인식을 파악함으로써 향후 지방정부의 효율적인 정보화를 위한 제안방안을 마련하고자 한다.

• Steel and Composite Structures
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• 제26권2호
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• pp.139-150
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• 2018

In this paper, two kinds of buckling restrained braces (BRBs) are designed to improve the mechanical properties and fatigue life, the reserved gap and viscoelastic filler with high energy dissipation capacity are employed as the sliding element, respectively. The fatigue life of BRBs considering the effect of sliding element is predicted based on Manson-Coffin model. The property tests under different displacement amplitudes are carried out to evaluate the mechanical properties and fatigue life of BRBs. At last, the finite element analysis is performed to study the effects of the gap and viscoelastic filler on mechanical properties BRBs. Experimental and simulation results indicate that BRB employed with viscoelastic filler has a higher fatigue life and more stable mechanical property compared to BRB employed with gap, and the smaller reserved gap can more effectively improve the energy dissipation capacity of BRB.

• 한국전산유체공학회지
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• 제11권3호
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• pp.64-70
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• 2006

A Computational study was carried out in order to investigate the moving wall effect of a circular cylinder at a Reynolds number of $2.0{\times}10^4$. The viscous-incompressible Navier-Stokes equations and Spalart-Almaras turbulent model of the commercial CFD code were adopted for this numerical analysis. The moving wall was set parallel with the freestream, and moving speed was equal to the freestream velocity. The gap ratio is defined as the distance ratio between the circular cylinder diameter and the height from the moving wall. The results show that there is vortex shedding over the critical gap ratio and aerodynamic loads including amplitude and the Strouhal number change according to the gap ratio.