• Tribology and Lubricants
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• 제32권1호
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• pp.1-8
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• 2016

This paper focuses on the thermal deformation induced preload change in the tilting pad journal bearing, using a three-dimensional (3D) thermo-hydro-dynamic (THD) approach. Preload is considered as a critical factor in designing the tilting pad journal bearing. The initial preload measured under nil external load and nil thermal gradient is influenced by two factors, namely, the thermal deformation and elastic deformation. Thermal deformation is due to a temperature distribution in the bearing pads, whereas the elastic deformation is due to fluid forces acting on the pads. This study focuses on the changes induced in preload and film clearance due to thermal deformation. The generalized Reynolds equation is used to evaluate the force of the fluid and the 3D energy equation is used to calculate the temperature of the lubricant. The abovementioned equations are combined by establishing a relationship between viscosity and temperature. The heat transfer within the bearing pads, the lubricant, and the spinning journal is calculated using the heat flux boundary condition. The 3D Finite Element Method (FEM) is used in modeling the (1) heat conduction in the spinning journal and bearing pads, (2) thermal gradient induced thermal distortion of the spinning journal and pads, and (3) viscous shearing, and heat conduction and convection in a thin film. This evaluation method has an increased fidelity, and it can prove to be a cost-effective tool that can be used by designers to predict the dynamic behavior of a bearing.

• 환경영향평가
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• 제21권5호
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• pp.725-734
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• 2012

The outbreak of foot and mouth disease in November 2010 raised many social, economic and environmental issues and water contaminations by leachate from carcass disposal sites particularly emerged as a serious concern. In oder to efficiently handle these problems, a critical method is required to transport leachate to livestock manure and sewage treatment plants and purify it. This study aims to present the best applicable method to transport leachate from carcass disposal sites into livestock manure and sewage treatment facilities. We investigated the biological and chemical characteristics such as BOD, COD, SS, TN, TP and Total coliforms. Current conjugated treatments in livestock manure and sewage treatment plants was studied by surveying the operations of those facilities. The NIER-MASS(National Institute of Environmental Research - Mass Balance Evaluation System of Sewage Treatment Facilities) program was applied to present the best conjugated treatment method through estimating the maximum daily load to meet the water quality standards in effluent.

• 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
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• 제26권3호
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• pp.17-26
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• 2020

Purpose: This paper presents research evidence that the environmental design of the doffing area in a biocontainment unit (BCU) can have a measurable impact on increasing the safety of frontline healthcare workers (HCW) during doffing of high-level personal protective equipment (PPE), and proposes optimized biocontainment unit design. Methods: From 2016 to 2019, The SimTigrate Design Lab conducted 3 consecutive studies, focusing on ways in which the built environment may support or hinder safe doffing. In the first study, to identify the risky behaviors, we observed 56 simulation exercises with HCWs in 4 BCUs and 1 high-fidelity BCU mockup. In the second study, we tested the effectiveness of a redesigned doffing area on improving the HCWs performance and used simulation, observation, and rapid prototyping in 1 high-fidelity mockup of a doffing area. In a follow-up study, we used simulation and co-design with HCWs to optimize the design of a safer doffing area in a full-size pediatric BCU mock-up. Results: We identified 11 specific risky behaviors potentially leading to occupational injury, or contamination of the PPE, or of the environment. We developed design strategies to create a space for safer doffing. In the second study, in a redesigned doffing area, the overall performance of HCW improved, and we observed a significant decrease in the number of risky behaviors; some risky behaviors were eliminated. There was a significant decrease in physical and cognitive load for the HCWs. Finally, we propose an optimized layout of a BCU for a safer process of PPE doffing. Implications: The proposed BCU design supports better staff communication, efficiency, and automates safer behaviors. Our findings can be used to develop design guidelines for spaces where patients with other highly infectious diseases are treated when the safety of the patient-facing HCWs is of critical importance.

• 열처리공학회지
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• 제16권6호
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• pp.329-334
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• 2003

Microstructure and mechanical properties of $(Ti_{1-x}Alx)N$ films, Produced by the the Ion Beam Sputtering(IBS) method, were studied by changing the Ti, Al contents. The compositions of films determined by RBS were $(Ti_{0.75}Al_{0.25})N$, $(Ti_{0.61}Al_{0.39})N$ and $(Ti_{0.5}Al_{0.5})N$, and XPS binding energies of Ti2P, A12p and N1s shifted to higher energies than those of pure Ti, Al and N, which indicated that nitrides were formed. XRD results indicated that the NaCl structure for $$x{\leq_-}0.39$$ changed into amorphous structure at x=0.5. For films with $$x{\leq_-}0.39$$, the lattice parameter decreased in proportion to the Al content. Nanoindentation hardness value were above HV=3300 at Al content up to x=0.39. However, the hardness of films with x=0.5 abruptly decreased to HV=1800, and this lower hardness values were attributed to different crystal structure. Critical load(Lc) in scratch test showed 23N at x=0.25, 22N at x=0.39 and 22N at x=0.5, which indicated that films with different Al contents showed similar adhesion behavior.

• Structural Engineering and Mechanics
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• 제38권4호
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• pp.479-501
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• 2011

Even though fiber reinforced polymer (FRP) has been widely used as a retrofitting material, the FRP behavior and effect in FRP retrofitted structure under blast loading, impulsive loading with instantaneous time duration, has not been accurately examined. The past studies have focused on the performance of FRP retrofitted structures by making simplifications in modeling, without incorporating accurate failure mechanisms of FRP. Therefore, it is critical to establish an analytical model that can properly consider the specific features of FRP material in evaluating the response of retrofitted concrete structures under blast loading. In this study, debonding failure analysis technique for FRP retrofitted concrete structure under blast loading is suggested by considering FRP material characteristics and debonding failure mechanisms as well as rate dependent failure mechanism based on a blast resisting design concept. In addition, blast simulation of FRP retrofitted RC panel is performed to validate the proposed model and analysis method. For validation of the proposed model and analysis method, the reported experimental results are compared with the debonding failure analysis results. From the comparative verification, it is confirmed that the proposed analytical model considering debonding failure of FRP is able to reasonably predict the behavior of FRP retrofitted concrete panel under blast loading.

• 오토저널
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• 제5권1호
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• pp.32-44
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• 1983

In case of $K_{Imax}$ < $K_{Iscc}$, the corrosion fatigue of high strength steel in 0.1N $H_{2}$S $O_{4}$ solution and 3.5% salt water is as follows. 1. The fatigue life shortens in order of 3.5% salt water and 0.1N $H_{2}$S $o_{4}$ solution. 2. The fatigue crack growth rate in air is obtained as the following equation. (dc/dN)$_{atr}$=7.23*10$^{-6}$ (.DELTA. K)$^{2.23}$ 3. The corrosion fatigue crack growth rate in environment is divided into three regions, that is, First Region, Second Region and Third Region from the small cyclic stress intensity. 4. The formation rate of the active surface on metal is slower than the mechano-chemical reaction rate in First Region. The crack growth rate depends on time and the cyclic stress intensity and is expressed as the following equation. (dc/dN)$_{I}$=C(/DELTA. K)$^{\delta}$ 5. The formation rate of the active surface is faster than the mechano-chemical reaction rate in Second Region and the synergistic effect by stress and corrosion becomes slow. In case the fatigue load is large, we have the critical crack growth rate which is not related to the cyclic stress intensity. 6. The corrosion crack growth rate by the mechano-chemical reaction is the same in $H_{2}$S $O_{4}$ solution and salt water, so Hydrogen accelerates the crack growth. 7. The environment has no effect on the corrosion fatigue crack growth rate in Third Region. 8. In First Region and Second Region, dimple is observed on the fatigue fracture surface in 0.1N $H_{2}$S $O_{4}$ solution. 9. The striation is observed in any environment as in air in Third Region and its interval approximately coincide with the crack growth rate.ate.e.e.

• 한국정보과학회논문지:시스템및이론
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• 제27권5호
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• pp.450-463
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• 2000

배열 재분산은 분산 메모리 컴퓨팅 환경에서 응용 프로그램의 수행 속도를 빠르게 하기 위해 많이 사용되고 있다. 특히 GEN BLOCK간 재분산은 동적으로 부하가 변화하는 경우 최적화된 성능을 보이기 위해 필요하다. 배열 재분산에 관한 기존 연구들은 대부분 CYCLIC(N)등과 같은 정규 분산 패턴간 재분산에 대해서만 이루어져 왔다. 그러나 GEN BLOCK등과 같은 비정규 분산 패턴간 재분산에서 발생하는 메시지패싱들은 정규 분산 패턴간 재분산과는 다른 특정을 보이기 때문에 이에 대한 새로운 연구가 필요하다. 본 논문은 GEN BLOCK간 재분산에서 발생하는 메시지패싱들에 정규 분산 패턴간 재분산에서 발견되 는 규칙성은 없는 반면 공간 지역성 (spacial locality)이 존재함을 보이고, 이를 기반으로 최소 스텝 정리와 최소 크기 정리가 재분산의 성능을 향상시키는데 중요함을 증병하였으며, 기존의 리스트 스케줄링 방식에 재구성 단계(relocation phase)를 추가함으로써 최적 스케줄을 생성하는 알고리즘을 제시하였다. 마지막으로 제안한 알고리즘의 성능을 평가하기 위해 ， CRAY T3E와 IBM SP2에서 성능 평가를 수행 하였으며， 그 결과 분산 메모리 병렬 머신에서 최소 스텝 정리와 최소 크기 정리를 만족하는 스케줄이 GEN BLOCK간 재분산의 성능 향상에 중요함을 보였다.

• 한국해양환경ㆍ에너지학회지
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• 제7권4호
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• pp.216-223
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• 2004

본 논문에서는 3차원 비선형 슬러싱 유동에 대한 수치해법을 개발하였다. 탱크내에서 과도한 슬러싱 유동이 일어나는 경우에는 슬러싱 유동에 의해 유기되는 유체 충격력에 의해 탱크 내부 부재나 탱크 자체의 손상을 야기할 수 있다. 비선형 슬러싱 유동을 포텐셜 유동 이론에 근거한 자유표면파 문제로 정식화하고, 엄밀한 비선형 자유표면 경계조건을 적용하여 수치적으로 해석하였다. 안정된 수치 해법 개발을 위해 해밀톤 원리에 근거한 변분법을 사용하였으며 얻어진 변분식에 유한 요소법을 적용하여 해석하였다. 비선형 자유표면 유동은 시간영역에서의 초기치 문제로 해석하였으며 자유표면의 위치는 매 계산 시간 간격마다 반복계산에 의해 결정되었다. 수치 해석 결과로는 탱크내에 위치한 파이프에 비선형 슬러싱 유동에 의해 야기되는 유체 충격력을 구하였다.

• 항공우주시스템공학회지
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• 제14권1호
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• pp.16-20
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• 2020

차량이 주행 중에 그리고 항공기가 활주로에 착륙하는 순간과 활주 중에 발생하는 피로는 착륙장치, 기체와 차량의 현가장치 등에 수명 주기와 밀접한 관련이 있다. 휠에 작용하는 하중들은 종축 힘, 횡력, 수직력과 제동력이다. 차량의 동특성과 내구성을 연구하기 위해 본 논문의 시뮬레이터는 시험실에서 실제 노면 형상을 재현에 사용된다. 그러므로 제품 개발 시간과 비용을 절감할 수 있다. 하드웨어적으로 유압 피로 시뮬레이터 구조의 중요한 요소는 각 축을 분리하고 여러 하중과 진동을 견뎌내는 것이다. 본 논문의 역기구학적 해석 방법은 Dummy wheel 중심에서 축 방향으로 최대 동작 변위를 준 후 커플링에 의한 유압 서보 작동기의 작동 크기를 도출한다. 해석의 결과는 실제 노면 형상을 정확하게 재현하기 위해 축 간의 커플링이 미약함을 확인하는 것이다.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2008년도 추계학술발표대회 논문집
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• pp.90-95
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• 2008

An SHGC(Solar Heat Gain Coefficient) is a determinant of total flux of solar radiation coming indoor and a critical factor in evaluating heating and cooling load. U-value represents heat loss while SHGC denominates heat gain. Recently, windows with high solar gain, mid solar gain or low solar gain are being produced with the development of Low-E coating technology. This study evaluated changes in energy consumption for heating and cooling according to changes in SHGC when using double-layered Low-E glass and triple layered Low-E glass in relation to double layered clear glass as base glass. An Office was chosen for the evaluation. For deriving optical properties of each window, WINDOW 5 by LBNL, an U.S. based company. and the results were analyzed to evaluate performance of heat and cooling energy on anannual basis using ESP-r, an energy interpretation program. Compared to the energy consumption of the double layered clear glass, the double layered Low-E glass with high solar gain consumed $69.5kWh/m^2,yr$, 9% more than the double layered clear glass in cooling energy. The one with mid solar gain consumed $63.1kWh/m^2,yr$, 1% less than the base glass while the one with low solar gain consumed $57.6kWh/m^2,yr$, 10% less than the base glass. When it comes to tripled layered glass, the ones with high solar showed 2% of increase respectively while the one with mid solar gain and low solar gain resulted 5% and 11% in decrease in energy consumption due to low acquisition of solar radiation. With respect to cooling energy. it was found that the lower the SHGC. the less energy consumption becomes.