• Steel and Composite Structures
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• 제44권6호
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• pp.829-843
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• 2022

This manuscript work presents a comprehensive continuum model capable to investigate the effect of porosity on vibro-acoustic behaviour of functionally graded (FG) beams resting on an elastic foundation subjected to thermal and mechanical loadings. Effects of uniform temperature rise and edge compressive load on the sound radiation characteristics are studied in a comparative manner. The numerical analysis is carried out by combining finite element method with Rayleigh's integral. Detailed parametric studies are accomplished, and influences of power law index, porosity volume, porosity distribution and boundary conditions on the vibro-acoustic response characteristics are analyzed. It is found that the vibro-acoustic response under mechanical edge compression is entirely different compared to from that under the thermal load. Furthermore, nature of grading of porosity affects the sound radiation behaviour for both the loads. The proposed model can be used to obtain the suppression performance of vibration and noise FG porous beams under thermal and mechanical loads.

• 한국태양에너지학회 논문집
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• 제26권4호
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• pp.9-16
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• 2006

Geothermal-energy has been getting popular as a natural energy source for green buildings these days. Public building with gross area more than $3000m^2$, planned after March, 2005, should spend about 5% of total building cost for equipment run by natural energy source (e.g. geothermal, solar heat, solar power, etc) according to renewable energy promotion law in Korea. As a result geothermal-energy using heat pump system is emerging as a effective alternative for realistic and economic plan although design guidelines and construction code for the system is in progress and technical data is far from sufficient. The quantitative analysis on the performance of geothermal-energy using heat pump system is insufficient for appropriate design of it. In this paper, cooling performance of geothermal-energy using heat pump system of residential and retail etc. mixed-use building has been analyzed on the basis of temperature comparison between inlet and outlet of heat exchangers of the operating system. Additionally, dry-bulb temperature and relative humidity have been measured and analyzed together as an index of indoor thermal environment.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.665-670
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• 2002

Pleasantness or quietness becomes one of the most important factors for residential designs recently. Especially for apartments, the noise generated by falling objects becomes a sensitive issue these days. To overcome the problem of the impact noise in apartments, the floor design has been changed. To reduce the transmissibility of the noise, composite floor structures are devised and implemented for the construction of apartments. In this paper, the noise reduction performance of a composite floor plate with holes is analyzed. Computational modelings for the structures are developed and its performance is evaluated by using the finite element method. The results show that the noise can be well reduced with the multi-layer composite floor plates with holes.

• 한국자동차공학회논문집
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• 제18권1호
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• pp.131-138
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• 2010

Because real flow of engine exhaust is very hot and highly transient, it may cause thermal and inertial loads on catalyzed filters in DPF. Transient and detailed flow and thermal simulations are necessary in this field. To assess the importance of time dependent phenomena, typical cone-type configuration such as an underbody DPF is selected for steady and transient analysis. User defined functions of FLUENT by sinusoidal inlet velocities are written and integrated with main solver for realistic simulation. Also, 4-cylinder and 6-cylinder engines for 3,000 L class are considered for the dynamic exhaust effect of engine type. Key parameters to understanding of catalyst performance and durability issues such as flow uniformity index and peak velocity are investigated. Also, pressure drop for engine power are considered. From the simulation results for three different cases, proper approach is recommended.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.152-157
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• 2003

This study represents the newly advanced formulation of hydraulic fluids for extended drain interval and introduces the performance results of used oil samples from various excavators. The used oil samples, in this paper show that there is a sharp change in viscosity drop and moderate additive depletion when viscosity index of hydraulic oil is very high. For the extension of hydraulic fluid life, it is necessary to improve the stability of viscosity and oxidation. New target properties from the used oil analysis were proposed for extended life. Performance of newly developed hydraulic oil based on used oil analysis is compared with previously used one. The properties of new formulation are the viscosity index of 140 and improved thermal stability consists of VHVI base oil. Field test results showed the possibility of extension of fluid life. Additionally, for development of high performance product, new required properties and performances were discussed.

• Current Optics and Photonics
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• 제7권2호
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• pp.213-221
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• 2023

The optical window, as a part of the collimator system, is the connector between the outside light source and the optical system inside a vacuum tank. The temperature and pressure difference between the two sides of the optical window cause not only thermoelastic deformation, but also refractive-index irregularities. To suppress the influence of these two changes on the performance of the collimator system, thermo-optical analysis is employed. Coefficients that characterize the deformations and refractive-index distributions are derived through finite-element analysis, and then imported into the collimator system using a user-defined surface in ZEMAX. The temperature and pressure difference imposed on the window seriously degrade the system performance of the collimator. A decentered and tilted lens group is designed to correct both field aberrations and the thermal effects of the window. Through lens-interval adjustment of the lens group, the diffraction-limited performance of the collimator can be maintained with a vacuum level of 10^-5 Pa and inside temperature ranging from -100 ℃ to 20 ℃.

• 한국해양공학회지
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• 제2권1호
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• pp.176-182
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• 1988

The exergy analysis on the heat storage performance of the senible heat storage unit which consists of the heat storage material in the concentric annulus and the hot fluid flowing through the inner tube is performed. Heat transfer characteristics which are necessary for the performance of the exergy analysis is obtained from the energy balance equations and the second law of thermodynamics. As the index of heat storage performance, the exergy lossnumber $N_{s}$, and exergy storage ratio from the concepts of the second law of thermodynamics are defined. Results are ovtained for the grometry of the storage unit, the Biot number Bi, ambient temperature $T_{o}$ as parameters. From these results the exergy storage ratio can be considered as the efficiency of the hat storage unit and is introduced as a guide to design.

• 한국화재소방학회논문지
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• 제17권1호
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• pp.33-39
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• 2003

본 논문에서는 벽지의 방염성능 및 열 안정성을 평가하고 연소가스인 CO, $CO_2$, HCN, HCl의 독성지수를 정량적으로 독성평가를 하여 벽지의 종합적 화재 위험성을 평가하였다. 방염성능은 방염성능기준인 45。 연소실험방법으로 열 안정성은 DSC분석과 TGA분석으로 평가하였다. 그리고 독성평가는 CO, $CO_2$, HCN, HCl 연소가스의 농도를 NIST N-GAS Model에 적용하여 독성지수로서 평가하였다. 위의 평가로 얻은 연구결과는 다음과 같다. 첫째, 방염성능 평가결과 방염한 종이벽지, 콜크벽지, PVC벽지는 방염성능 기준에 적합한 것으로 나타났다. 둘째, 열 안정성 평가인 DSC분석 결과 미방염한 종이벽지, 콜크벽지, PVC벽지가 방염한 것보다 상대적으로 저온부에서 발열개시가 되었으며, 더 많은 발열량을 내었으므로 열적으로 더 위험하였다. 그리고 TGA분석 결과 미방염한 종이벽지, 콜크벽지, PVC벽지의 분해속도가 방염한 것보다 휠씬 빨랐으므로 열 분해 위험성이 더 크다고 판단된다. 셋째, 연소가스 독성평가 결과는 방염한 종이벽지, 콜크벽지, PVC벽지가 미방염한 것보다 독성지수가 더 높게 나타났다. 또한 종이벽지와 콜크벽지보다 PVC벽지가 상대적으로 독성지수가 더 높음을 알 수 있었다.

• 교육녹색환경연구
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• 제4권4호
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• pp.1-18
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• 2004

Research has been carried out to study thermal environment in a classroom under three kinds of air diffusion temperature and six kinds of air diffusion direction for ceiling type air conditioner. The velocity and temperature distributions of air in the room calculated by 3-dimensional numerical method(PHOENICS), This present study was also conducted to calculate the Air Diffusion Performance Index(ADPI) for cooling conditions and Predicted Percentage of Dissatisfied(PPD) for heating conditions. This analysis shows that the optimum angle of ceiling type air conditioner's diffusion is $15{\sim}30^{\circ}$ for cooling mode and about $15{\sim}45^{\circ}$ for heating mode in these calculating conditions. And also analysis has been carried out to evaluate thermal comfort of vertical and horizontal cross section of classroom.

• Composites Research
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• 제23권6호
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• pp.47-54
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• 2010

위성체에 장착된 얇은 벽 복합재보에 대한 열 진동 특성에 대한 연구를 수행하였다. 복합재 보는 얇은 벽과 원주 방향으로 강성이 일정하다고 가정을 하였으며, 기존에 우주사용 적합성이 증명된 T300/Epoxy, YS90A/Epoxy와 같은 소재를 채택하여 모델링을 하였다. 자세제어 오차각 및 복합재 보의 끝단 변위에 대한 정적상태 및 정점-정점 오차를 열 진동 특성의 성능지수로 하여 평가하였으며, 평가결과 YS90A 복합재가 자세제어 오차각의 정점-정점 각도에서 2배 정도의 우수한 성능을 보여 주었다.