• 설비공학논문집
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• 제18권1호
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• pp.24-30
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• 2006

Three liquid cooling heat exchangers for cooling of telecommunication equipment were designed and their cooling performances were tested. The liquid cooling heat exchangers had twelve rectangular channels $(5\times3 mm)$ with different flow paths of 1, 4, and 12. Silicon rubber heaters were used to provide heat flux to the test section. Heat input was varied from 75 to 400 W, while flow rate and inlet temperature of working fluid were altered from 1.2 to 4.0 liter/fin and from 15 to 3$30^{\circ}C$, respectively. The 4-path heat exchanger showed lower and more uniform average inner temperatures between heaters and the surface of heat exchanger than those of the others. To obtain optimal distribution of working fluid to each channels of liquid cooling heat exchangers, 2-3-2 and 4-3 type tube distributors were designed, and their distribution performances of working fluid were numerically and experimentally investigated. The distributor of the 2-3-2 type showed superior distribution performance compared with those of the 4-3 type distributor.

• Wind and Structures
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• 제25권2호
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• pp.101-129
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• 2017

Local transient extreme wind loads caused by group tower-related interference are among the major reasons that lead to wind-induced damage of super-large cooling towers. Four-tower arrangements are the most commonly seen patterns for super-large cooling towers. We considered five typical four-tower arrangements in engineering practice, namely, single row, rectangular, rhombic, L-shaped, and oblique L-shaped. Wind tunnel tests for rigid body were performed to determine the influence of different arrangements on static and dynamic wind loads and extreme interference effect. The most unfavorable working conditions (i.e., the largest overall wind loads) were determined based on the overall aerodynamic coefficient under different four-tower arrangements. Then we calculated the one-, two- and three-dimensional aerodynamic loads under different four-tower arrangements. Statistical analyses were performed on the wind pressure signals in the amplitude and time domains under the most unfavorable working conditions. On this basis, the non-Gaussian distribution characteristics of aerodynamic loads on the surface of the cooling towers under different four-tower arrangements were analyzed. We applied the Sadek-Simiu procedure to the calculation of two- and three-dimensional aerodynamic loads in the cooling towers under the four-tower arrangements, and the extreme wind load distribution patterns under the most unfavorable working conditions in each arrangement were compared. Finally, we proposed a uniform equation for fitting the extreme wind loads under the four-tower arrangements; the accuracy and reliability of the equation were verified. Our research findings will contribute to the optimization of the four-tower arrangements and the determination of extreme wind loads of super-large cooling towers.

• 마이크로전자및패키징학회지
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• 제23권3호
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• pp.37-41
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• 2016

본 논문에서는 긴 작동거리(working distance, WD)를 가지는 근적외선 형광 이미징 시스템을 소개하고, gain, 노출시간, 작동거리, 확대배율 등 측정 변수에 의한 형광 영상의 차이에 대해 분석하였다. 노출시간이 길수록, 확대배율이 클수록 형광신호는 더욱 강해지고, gain이 클수록 형광신호도 강해지지만, 배경신호도 함께 증가하여 SBR은 나빠질 수 있다. 제안한 시스템은 레이저 조사 방식으로 인해 작동거리가 짧은 경우 레이저 조사 영역의 강도 분포가 균일하지 못해서 형광신호가 약해지며, 그에 따른 해결방안을 제안하였다.

• Structural Engineering and Mechanics
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• 제70권4호
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• pp.479-497
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• 2019

In the current code design, the use of a uniform internal pressure coefficient of cooling towers as internal suction cannot reflect the 3D characteristics of flow field inside the tower body with different ventilation rate of shutters. Moreover, extreme weather such as heavy rain also has a direct impact on aerodynamic force on the internal surface and changes the turbulence effect of pulsating wind. In this study, the world's tallest cooling tower under construction, which stands 210m, is taken as the research object. The algorithm for two-way coupling between wind and rain is adopted. Simulation of wind field and raindrops is performed iteratively using continuous phase and discrete phase models, respectively, under the general principles of computational fluid dynamics (CFD). Firstly, the rule of influence of 9 combinations of wind speed and rainfall intensity on the volume of wind-driven rain, additional action force of raindrops and equivalent internal pressure coefficient of the tower body is analyzed. The combination of wind velocity and rainfall intensity that is most unfavorable to the cooling tower in terms of distribution of internal pressure coefficient is identified. On this basis, the wind/rain loads, distribution of aerodynamic force and working mechanism of internal pressures of the cooling tower under the most unfavorable working condition are compared between the four ventilation rates of shutters (0%, 15%, 30% and 100%). The results show that the amount of raindrops captured by the internal surface of the tower decreases as the wind velocity increases, and increases along with the rainfall intensity and ventilation rate of the shutters. The maximum value of rain-induced pressure coefficient is 0.013. The research findings lay the basis for determining the precise values of internal surface loads of cooling tower under extreme weather conditions.

• Journal of Yeungnam Medical Science
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• 제13권2호
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• pp.324-346
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• 1996

의사와 간호사의 복장에 대한 견해를 파악하기 위하여 1996년 3월1일부터 1996년 3월31일까지 영남대학교 의료원에 근무하는 의사 130명, 간호사 147명과 입원환자 211명을 대상으로 자기기입식 설문조사를 실시하였다. 의상의 복장에서는 의사와 간호사 모두 기존 코트 형태의 가운보다 다른 형태의 가운을 선호하였고, 특히, 의사보다 간호사들이 더 선호하였다. 환자에서 전체적으로 기존 형태와 다른 형태의 가운에 대한 선호도의 차이는 없었으나, 학력이 높을수록 다른 형태의 가운을 더 선호하였다(p<0.01). 의사의 가운 색상에 있어 의사와 간호사의 73.6%는 흰색을 선호하였으며, 환자는 86.3%가 흰색을 선호하였다. 남자의사가 여자의사와 간호사에 비해 흰색을 더 선호하였고(p<0.01), 환자에서는 색상 선호도에 대한 유의한 차이는 없었다. 진료시 넥타이를 착용해야 한다라는 응답률이 남자의사, 40세 이상 의사, 내과계 근무 의사, 그리고 교수에서 다른 군보다 유의하게 높았다(p<0.01). 환자에서는 여자가 남자보다, 60세 이상군이 다른 연령군보다, 초등졸 이하군이 다른 학력군보다, 기타 시지역 거주자와 군지역 거주자가 대구시 거주자보다 더 높았다(p<0.01). 주말 및 휴일 진료시 의사의 캐주얼 복장에 대해서는 전체적으로 찬성하는 편이었고, 의사의 연령이 젊을수록 유의하게 선호도가 높았다(p<0.05). 간호사 복장에 대해서는 의사와 간호사 전체의 78%가 바지 착용을 선호하였고, 간호사는 96%가 바지 착용을 선호하였으며, 특히, 40세 이상군과 외래, 지원 및 행정부서에 근무하는 간호사들은 100% 선호하였다. 환자들은 학력이 낮을수록 스커트를 선호하였고, 고학력군일수록 바지 착용을 선호하였다. 간호사의 가운 색상에 대해서는 의사와 간호사 전체의 46.7%가 흰색을 선호하였고, 의사들은 흰색을, 간호사들은 다른 색을 더 선호하였다(p<0.01). 환자들은 79.1%가 흰색을 선호하였다. 캡 착용에 대한 문항에서 간호사들은 95.9%가 착용하지 않아도 좋다고 응답하였으며, 특히, 40세 이상군과 외래 및 특수부서에 근무하는 간호사들은 전원 캡을 착용하지 않아도 좋다라고 응답하였다. 반면에 환자들은 77.7%가 캡을 착용하여야 한다라고 응답하였다. 이상의 결과로 보아 의사와 간호사의 복장은 기존의 전통적인 형태와 색상만을 고집할 것이 아니라, 의사와 간호사 본인들과 환자들의 의견을 만족시킬 뿐만 아니라 시대적 흐름과 현실감각에 맞게 가운의 형태와 색상에 변화를 주는 것을 고려하는 것이 좋을 것이라고 사료되었다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.1298-1302
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• 2011

The present study deals with the results of a thermo-fluid analysis applied to the cooling plate of the water cooling system developed for IGBT stacks, which was designed to keep the power semi-conductors from over heating problems. The cooling plate is to absorb a maximum quantity of 10kW from 4 IGBTs which are to be placed on both sides of the cooling plate, 2 IGBTs of them on each surface. For the analysis, Adina of CFD Program was used and an analysis was conducted to obtain the knowledges on heat and mass flow at both the plate and fluid flow inside. For the simulation, the operational conditions of a temperature difference of $15^{\circ}C$ for the working fluid and a uniform heat flux of about 92000 $W/m^2$ on the surface in contact with an IGBTs.

• 소성∙가공
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• 제14권4호
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• pp.375-383
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• 2005

The shear spinning process, where the plastic deformation zone is localized in a very small portion of the workpiece, shows a promise for increasingly broader application to the production of axially symmetric parts. In this paper, the three components of the working force are calculated by a newly proposed deformation model in which the spinning process is understood as shearing deformation after uniaxial yielding by bending, and shear stress, $\tau_{rz}$, becomes k, yield limit in pure shear, in the deformation zone. The tangential force are first calculated and the feed force and the normal force are obtained by the assumption of uniform distribution of roller pressure on the contact surface. The optimum contact area is obtained by minimizing the bending energy required to get the assumed deformation of the blank. The calculated forces are compared with experimental results. A comparison shows that theoretical prediction is reasonably in good agreement with experimental results

• 소성∙가공
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• 제7권5호
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• pp.489-495
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• 1998

Spinning is a chipless forming method for producing axially symmetric parts by using axial-radial motions of a spinning roller. This process has still some advantages in such a view point that a variety of complex shapes which can not be formed in a press can be easily spun at a low cost although it is one of the oldest forming methods for spinning mainly cookware parts for a long time. This study is to investigate the optimum roller path in order to obtain the maximum spinnability in producing cylindrical cups of Aluminum(A1050-H16) sheet metal. Working conditions applicable to any size of blank were predetermined through preliminary spinning tests. 9 types of roller path were proposed and experiments were carried out. The modified involute curve was shown to give the maximum drawing ration and more uniform quality of spun cups as compared with other results of this study. in addition thickness distribution and dimensional accuracy of spun cups were examined and discussed.

• Journal of Advanced Marine Engineering and Technology
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• 제29권1호
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• pp.25-33
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• 2005

When a circular tube with uniform heat generation within the wall was placed in a cross flow, heat flows by conduction in the circumferential direction due to the asymmetric nature of the fluid flow around the perimeter of the circular tube The circumferential heat flow affects the wall temperature distribution to such an extent that. in some cases, significantly different results may be obtained for geometrically similar surfaces. In the present investigation, the effect of circumferential wall heat conduction is investigated for forced convection around circular tube in cross flow of air and water Two-dimensional temperature distribution $T_w(r,{\theta})$ is calculated through the numerical analysis. The difference between one-dimensional and two-dimensional solutions is demonstrated on the graph of local heat transfer coefficients. It is observed that the effect of working fluid is very remarkable.

• 가정과삶의질연구
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• 제18권2호
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• pp.15-27
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• 2000

This study puts an emphasis on the importance clothing and its reuse, dealing with the unmarried women workers who will be main domestic consumers. Questionnaire survey method was used in this research. The sample was taken from 546 unmarried women workers. The major findings are summarized as follows, it was found that Factor I was the cause of unplanned clothing management, Factor II was the cause of clothing modification and body type changes and Factors III was the cause of fashionmongering. Second, it was shown that as for experiences in hoarded clothing recycling disposition behavior subjective social strate had the high level, the group of sale and technical jobs / self-employed jobs had the higher level than the group of specialized skil / management jobs, the group in office-going and leaving clothing had the higher level than the group of people in separate uniform as working dress and the group of those experienced in environmental education had the high level.