• Journal of the Korean Institute of Landscape Architecture
• /
• v.29 no.2
• /
• pp.50-60
• /
• 2001

교량설계에 있어서는 교량의 기능과 안전성, 경제성 등 구조 광학적인 면을 고려하여 설계하게 되는데 최근에는 교량의 경관설계에 관해서도 많은 관심을 갖고 있다. 그러나, 국내에선 교량의 구조적인 측면에서의 연구는 활발하게 이루어지고 있으나 교량의 경관설계에 대한 연구는 거의 이루어지고 있지 않다. 따라서, 본 연구의 목적은 교량의 구조 공학적인 판단과 경관 공학적인 판단에 의해서 교량 형식을 결정하는 방법과 선호도가 높은 현수교의 시점장을 분석하는데 있다. 교량형식을 결정하는 방법은 기초설계단계에서 Seen 경관을 고려하여 교량의 유형을 결정하고, 교량의 구조적인 정.동역학적 검토와 Seen경관.Sequence 경관 등을 고려하여 교종의 형식을 결정하게 되는 각 단계별 설계조건에 따른 교량설계 방법을 흐름도로 제시하였다. 또한, 현수교의 시점장의 범위를 정량적으로 나타내기 위해서 교량전체에 대한 시선입사각, 가까운 쪽의 주탑에 대한 시선입사각, 가까운 쪽 주탑의 외관 크기에 대한 연직시각, 교량전체가 시야에 들어올 수 있는 수평시각 등을 주시실험 자료와 Professional 현수교의 사진에 의한 구조형태의 비율 등을 측정하여 분석 교차한 결과 교량전체에 대한 시선입사각 $\alpha$=(15$\pm$7.5)$^{\circ}$, 가까운 쪽의 주탑에 대한 시선입사각 V=(30$\pm$7.5)$^{\circ}$, 가까운 쪽 주탑의 외관 크기에 대한 연직시각 18$^{\circ}$$\leq$$\delta$27$^{\circ}$, 교량전체가 시야에 들어올 수 있는 수평시각 $\theta$$\leq$60$^{\circ}$의 시점장을 얻을 수 있었다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.11
• /
• pp.801-805
• /
• 2013

In this study, electrocaloric effects of Pb-free $(Ba_{0.85}Ca_{0.15})(Ti_{0.92}Zr_{0.08})O_3$ ferroelectric ceramics were investigated and discussed using the characteristics of P-E hysteresis loops at wide temperature range from room temperature to $140^{\circ}C$. The remnant polarization $P_r$ and coercive field $E_c$ were decreased with increasing temperature. The temperature change ${\Delta}T$ by the electrcaloric effect was calculated by Maxwell's relations, and reached the maximum of ~0.15 at $120^{\circ}C$ under applied electric field of 30 kV/cm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.30 no.4
• /
• pp.223-228
• /
• 2017

In this study, in order to develop composition ceramics for refrigeration device application at a temperature of less than $90^{\circ}C$, a $Ba(Ti_{1-x}Zr_x)O_3$ composition was fabricated using a conventional solid-state method. Electrocaloric properties of these ceramics were investigated using the characteristics of P-E hysteresis loops in a wide temperature range from room temperature to $150^{\circ}C$. The Curie temperature of $Ba(Ti_{1-x}Zr_x)O_3$ ceramics decreased with the increase of x. The maximum value of ${\Delta}T=0.07^{\circ}C$ in an ambient temperature of $85^{\circ}C$ under 30 kV/cm appeared when x = 0.125. It was concluded that the composition (x = 0.125) ceramics can be used for refrigeration device applications.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2009.10a
• /
• pp.1077-1080
• /
• 2009

In this paper, we propose a new method for measuring image sticking of an OLED display using a human visual test. We determined that the perceptual image sticking threshold is 2% of luminance difference at 200 nits and 1% at 100 nits, respectively. Color shift must also be considered when evaluating image sticking, as a ${\Delta}$(u', v') shift of just over 0.002 can be recognized regardless of background brightness. Perception of image sticking is affected by the background level, test pattern, and ambient illumination conditions. The evaluation standard must consider both luminance variation and color shift simultaneously.

• Proceedings of the KIEE Conference
• /
• 1998.07a
• /
• pp.107-109
• /
• 1998

This paper presents mechanical analysis of gas turbine generator (113MVA, $3{\phi}$, 2P, 0.9PF, F class, 3600rpm, 60Hz, 13.8kV, 4.72kA, Air-Cooling) field coil deformation. Rotor end coil deformation is only appeared on turbine end but collector end coil is normal. Expansion direction of end coil is tangential not axial. Deformation appears more severe at top turn. Retaining ling is expanded by centrifugal force of coil and itself. In case friction coefficient between coil top surface and retaining ring insulation inner surface is small, coil end length ${\ell}$ does not change. However, in case friction coefficient big condition, coil end is expanded ${\Delta}{\ell}$ due to start and stop. Deformation is assumed about 30mm by watching photograph inner surface of retaining ring is coated by Teflon at manufacturing condition. Usually Teflon coating insulation surface is small friction coefficient. It's value 0.08${\sim}$0.15. However it's value exceeds more than 0.297. Since top turn deformation appears. The distortion and subsequent failure have occurred because of the lack of a sufficient slip-plane between the top field coil conductors and the inside surface of the retaining ring insulation on the turbine end of the field-winding.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.13 no.4
• /
• pp.22-29
• /
• 2009

Development of Moon Explorer-1 (orbiter) is supposed to be commenced in 2017 and launched in 2020. In case of Moon Explorer-2 (lander), it would be slated to start in 2021 and launch in 2025. In this paper conceptual feasibility studies are conducted for the propulsion system applicable to a Moon Explorer. In the first place the availability of monopropellant/bipropellant/electric propulsion system is examined with domestic as well as overseas precedents. Secondly ${\Delta}V$ is estimated by the mission analysis and the propellant budget is calculated accordingly. Subsequently feasibility of a chemical propulsion system for a Moon Explorer is evaluated.

• Journal of Aerospace System Engineering
• /
• v.9 no.4
• /
• pp.16-22
• /
• 2015

Korea Aerospace Research Institute(here after KARI) has a plan to launch experimental lunar orbiter in 2018, and lunar orbiter and lander in 2020. There are several ways to go to the moon. Which one is direct transfer trajectory and another one is phasing loop transfer trajectory and the other one is WSB trajectory. Regardless of the transfer trajectories, LOI maneuver is the most important maneuver of all mission sequences because if this burn is failed, it is too difficult to get into the lunar orbit in the future. This paper describes first LOI target value of foreign lunar orbiters and analyzes orbital variations of experimental lunar orbiter according to various target values. By analyzing the variation of orbiter parameter after first LOI, proper orbital period for LOI target value are recommended to meet the inclination, apoapsis and periapsis altitude constraints.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.420-420
• /
• 2010

AC PDP에서 유전체 보호막으로 사용되는 MgO 박막은 높은 이차전자방출계수($\gamma$)로 인해 방전전압을 낮춰주는 중요한 역할을 하고 있다. 이러한 MgO 보호막의 이차전자방출계수를 증가시키기 위해 MgO 의 Energy Band Structure 규명이 중요한 연구 주제가 되고 있다. MgO의 이차전자방출계수($\gamma$)는 Auger 중화 이론에 의해 방출 메커니즘이 설명이 되고, 그 원리는 다음과 같다. 고유의 이온화 에너지를 가진 이온이 MgO 표면에 입사 되면, Tunneling Effect에 의해 전자와 이온 사이에 중화가 일어나고, 중화가 되고 남은 에너지가 MgO Valance Band 내의 전자에게 전달되면 이때 남은 에너지(${\Delta}E$)가 MgO의 일함수(Work function) 보다 크게 되면 이차전자로 방출된다. 본 실험 에서는 $\gamma$-FIB System을 이용하여 결정 방향이 (100), (110), (111)을 갖는 Single Crystal MgO에 이온화 에너지가 24.58eV인 He Ion source를 주사 하였을 때 Auger self-convolution을 통해 이차전자의 운동 에너지 분포를 구하고, 이를 통해 MgO 내의 Energy Band Structure를 실험적으로 측정하였다. 이를 통해 MgO Single Crystal의 일함수 및 Defect Level의 분포를 확인하였다.

• Structural Engineering and Mechanics
• /
• v.73 no.1
• /
• pp.17-25
• /
• 2020

A finite element (FE) model for analyzing slender reinforced high-strength concrete (HSC) columns under biaxial eccentric loading is formulated in terms of the Euler-Bernoulli theory. The cross section of columns is divided into discrete concrete and reinforcing steel fibers so as to account for varied material properties over the section. The interaction between axial and bending fields is introduced in the FE formulation so as to take the large-displacement or P-delta effects into consideration. The proposed model aims to be simple, user-friendly, and capable of simulating the full-range inelastic behavior of reinforced HSC slender columns. The nonlinear model is calibrated against the experimental data for slender column specimens available in the technical literature. By using the proposed model, a numerical study is carried out on pin-ended slender HSC square columns under axial compression and biaxial bending, with investigation variables including the load eccentricity and eccentricity angle. The calibrated model is expected to provide a valuable tool for more efficiently designing HSC columns.

• Bulletin of the Korean Chemical Society
• /
• v.21 no.8
• /
• pp.779-784
• /
• 2000

Comparing the adsorption properties and dissociation on a Pt(111) iththat ona Fe(111) surface, we have con-sidered seven coordination modes of the adsorbed binding site: $di-${\sigma}$${\Delta}$\mu\pi/\mu$, 1-fbld,2-fold, and 3-fbld sites. On the Pt(111) surface, t he adsorbed binding site of carbon dioxide was strongestat the1-fold site and weakest at the $\pi/\mu-site.$ The adsorbed binding site on the Fe(111) surface was strongest at the di-бsite and weakest at the 3-fold site. We have found that the binding energy at each site that excepted 3-fold on the Fe(111) surface was stronger than the binding energy on the Pt(111) surface and that chemisorbed $CO_2bends$ because of metal mixing with $2\piu${\rightarrow}$6a_1CO_2orbital.$, The dissociation reaction occured in two steps, with an intermediate com-plex composed of atomic oxygen and ${\pi}bonding$ CO forming. The OCO angles of reaction intermediate com-plex structure for the dissociation reaction $were115^{\circ}Con$ the Pt(111), and $117^{\circ}C$ on the Fe(111) surface. We have found that the $CO_2dissociation$ rea11) surface proceeds easily,with an activationenergy about 0.2 eV lower than that on the Pt(111) surface.