• 한국안전학회지
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• 제14권4호
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• pp.3-12
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• 1999

This research concentrates on the influence of non-linearities associated with impact for the nonlinear rocking behavior of rigid block subjected to one dimensional sinusoidal excitation of horizontal direction. The transition of two governing rocking equations, the abrupt reduction in the kinetic energy associated with impact, and sliding motion of block. In this study, two type of rocking vibration system are considered. One is the undamped rocking vibration system, disregarding energy dissipation at impact and the other is the damped rocking system, including energy dissipation and sliding motion. The response analysis using non-dimensional rocking equation is carried out for the change of excitation parameters and friction coefficient. The chaos responses were discovered in the wide response region, particularly, for the case of high excitation amplitude and their chaos characteristics were examined by the time history, Poincare map, power spectra and Lyapunov Exponent of rocking responses. The complex behavior of chaos response, in the phase space, were illustrated by Poincare map. The bifurcation diagram and Poincare map were shown to be effective in order to understand chaos of rocking system.

• Advances in pediatric surgery
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• 제19권2호
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• pp.156-161
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• 2013

Congenital segmental dilatation of the colon is a very rare entity of unknown etiology, characterized by a localized dilatation of a bowel segment of the colon of variable length and an abrupt transition between the normal and dilated intestine. It can affect any part of the colon, with the rectosigmoid colon being the most commonly affected site. The clinical and radiological features may resemble that of Hirschsprung disease, but differ in that the normal ganglion cells are found in the dilated and normal segment of the colon. We performed laparoscopic-assisted transanal endorectal pull-through for segmental dilatation of rectosigmoid colon in an 8-year-old boy with chronic constipation since the age of 5 months.

• 천문학회보
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• 제42권2호
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• pp.78.2-78.2
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• 2017

Post-starburst (E+A) galaxies are thought to be in the green valley transition phase between star-forming blue galaxies and quiescent red galaxies. They are identified by their unusual spectra characterized by strong Balmer absorption lines and weak emission lines, indicating a period of starburst followed by abrupt quenching. However, the underlying mechanism that drives the formation of E+A galaxies still remains contradictory or inconclusive. Thus, in order to differentiate between the different formation scenarios of E+A galaxies, we perform a statistical analysis of the environments of E+A galaxies. We spectroscopically identify a large sample of post-starburst galaxies from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) using a selection criteria based on $H{\delta}$ equivalent width. We report our findings and discuss their implications in the context of post-starburst galaxy formation.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.178-178
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• 1999

Low temperature Si epitaxy can provide flexibility for a device designer to tailor or optimize the device performance. It is better method for controlling the doping thickness, concentration and profile than ion implantation and diffusion. But there is a limited growth thickness in this method. At a given temperature, the film grows epitaxially for a certain limiting thickness(hepi) and becomes amorphous. The transition from crystalline Si to amorphous Si is abrupt. In this study, Si film was deposited by ion beam sputter deposition on Si (0001) above a limiting thickness and measure the strain in the interface between crystalline Si and amorphous Si. The strain was compressive and the maximum value was about 2%.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1424-1427
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• 1996

The pressure-area isotherm(${\pi}$-A isotherm) of 8A5H(4-octyl-4'-(5-Carboxyl-pentamethyleneoxy)-azobenzene) at the air/water interface were obtained. Using the Xe/Hg Xe 500w(93' model 68811), an activities of molecule at the air/water interface were certified. In addition, using a current-measuring technique, we investigated the abrupt changes of a current observed at the liquid-to-solid phase transition in a current-area (I-A) isotherm of a fatty acid monolayer at the air/water interface

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 추계학술대회 논문집
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• pp.52-55
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• 1997

In this study, PLZT stock solutions were prepared by sol-gel processing to fabricate PLZT thin films. The stock solutions were spin-coated on ITO-glass and the film were annealed by rapid thermal annealing(RTA). The variation of tile crystallographic structure of the thin films and the phase transition with respect to it were observed using Raman spectra. Raman result showed that the band of spectra are broad as the amount of Zr substitution increased and specially, abrupt change occurs in the raman spectra upon crossing the tetragonal-rhombohedral phase boundry at 2/55/45 PLZT thin film. So, the fact that the crystallographic structure was transitted from tetragonal to rhombohedral structure was certified.

• 한국표면공학회지
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• 제23권2호
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• pp.1-10
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• 1990

Metal-Organic Vapor Phase Epitaxy (MOVPE) is an epitaxial process utilizaing ane or more of organometallice as reactnte to grow compound semicond semiconductror layers. MOVPE is basically a cold wall process in which reactants are delivered without reacting with each other to the heated substrate where reactants are thermally decomposed to from compound semiconductors through chemical reaction. Since reactants are delivered as gas phase and the formation of the single crystal compunds depends on the thermal decomposition of the reactants, details of MOVPE relies on the hydrodynamics and pyroltsis and chemical reation of reactants inside on reaction chamber. It has been demonstrated that MOVPE is capable of growing virtually all of the III-V, II-VI and IV-VI compound semiconductrs, fabricating ultrathin epilayers, for ming abrupt hetrointerfaces with monolayer transition width, and is suitable for multi-wafer operation yilding a high throghtput. Overiew of reactror componts and layer, characteristics, and status of MOVPE are discussed.

• 대한교통학회지
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• 제25권1호
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• pp.23-35
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• 2007

고속도로 분류부는 고속에서 저속으로의 급격한 감속, 양호한 기하구조에서 취약한 기하구조로의 급격한 선형변화가 발생하는 구간으로, 고속도로 구성요소 중 사고위험이 매우 높은 구간에 해당된다 따라서 분류부 설계시는 안전하고 원활한 교통흐름이 이루어지도록 세심한 주의를 기울여야 함은 물론 이의 달성을 위한 설계기준이 수립되어야 한다. 이에 따라 현 도로설계기준에서는 차로변경을 위한 변이구간, 감속을 위한 감속구간 그리고 무한 곡선반경에서 유한곡선반경으로의 원활한 차량주행궤적 변경을 위한 완화곡선 등 이를 위한 설계기준을 제시하고 있으나, 실제 그 적용에 있어서는 설계기준상의 각 구간별 구성에 대한 정의가 명확하지 않아 분류부의 각 구성요소가 중첩되어 설계되고 있다. 이러한 설계기준상의 문제로 인한 각 구성요소간 혼재는 현 설계기준에서 의도하고 있는 분류부에서의 역할을 충분히 발휘하지 못하게 하는 결과를 초래하고 있으며 일관된 선형을 기대하는 운전자에게 혼동을 야기시키는 등 많은 고속도로 분류부 현장에서 안전상 문제점으로 작용하고 있다. 따라서 본 연구에서는 고속도로 분류부에서의 실측 현장조사 데이터를 바탕으로 분류부 차량주행행태 특성 분석 및 사고예측모형의 개발을 통해 다양한 교통조건 및 기하구조 조건을 고려한 분류부 설계기준 개선안을 제시하였다.

• Elastomers and Composites
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• 제39권2호
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• pp.95-104
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• 2004

방진고무의 내한성을 향상시키기 위하여 NR 컴파운드에 유리전이온도가 상대적으로 낮은 BR을 섞거나 오일 함량을 늘리는 방법을 이용하여 새로운 컴파운드를 제작하였다. 저온환경에서 기계적물성 실험을 수행하여 NR/BR 조성비 및 오일 함량에 따른 영향을 조사하였다. BR 함량이 증가할수록 경도 및 모듈러스가 증가한 반면 인장강도 및 신율은 감소하였고, 오일 함량이 많을수록 경도, 모듈러스 및 인장강도는 감소하였으나 신율은 거의 변화가 없었다. NR/BR 블렌드 고무컴파운드는 NR과 BR의 유리 전이 온도인 $-50^{\circ}C$와 $-90^{\circ}C$에서 저장탄성계수의 급격한 전이와 손실계수인 tan ${\delta}$가 최대값을 보여 두 컴파운드간의 비상용성을 나타내었다.

• 대한기계학회논문집A
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• 제25권3호
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• pp.510-519
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• 2001

The tensile and fracture toughness tests have been conducted to investigate the degradations of mechanical properties induced mainly by neutron irradiations in Zr-2.5Nb CANDU pressure tube materials operated in Wolsung Unit-1. the tests were performed at room, 150, 200, 250, 300 $\^{C}$ for the irradiated and unirradiated specimens in hot cell. The specimens were directly machined from the tube retaining original curvature using specially designed electric discharge machine(EDM). From the tensile tests of the irradiated specimens, it was found that tensile strength was increased and total elongation was decreased compared to those of the unirradiated ones. The active voltages in the fracture toughness tests for the irradiated showed the discontinuous abrupt increases caused by crack jumping in lower temperature. In the crack resistance curves we found the stable crack growth in the unirradiated, whereas the unstable and three crack growth stages in the irradiated specimens due to the accumulated irradiation defects. The various fracture characteristic values in the irradiated are remarkably lower than those of the unirradiated. Through the fractography, we found in the irradiated that smaller dimple and shorter fissures than the unirradiated, and that the fractured surface had three regions that were flat, transition and slant/shear area. These can explain the difference in the crack growth characteristic values of the irradiated and the unirradiated ones.