• 농업과학연구
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• 제37권1호
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• pp.81-86
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• 2010

The urban thermal environment can be an important index to detect heat island phenomena and manage it to improve urban life quality. Cheongju is a typical plain-city that main part has been formed and developed in lowland. The Mushim stream crosses the city from south to north. We reviewed the use of thermal remote sensing in stream around areas and the thermal environments, focusing primarily on the Urban Heat Island(UHI) effect. The purpose of this study is to determine the relationship between the stream nearby urban area and the stream cooling effect of UHI. The objectives are to determine the usefulness of KOMPSAT-2 bands MS3 and MS4 for vegetation cover mapping, and the usefulness of LANDSAT TM band 6 in identifying thermal environmental characteristics and UHI. Land Surface Temperatures (LST) are retrieved by single-channel algorithm to study the UHI from the 6th band (thermal infrared band) of LANDSAT TM images and thermal radiance thermometer based on remote sensing method and the LST distribution maps are accomplished according to the retrieval results. There is also comparison of satellite-derived and in situ measured temperature. The results indicated that the LST of urban center is higher than that of suburban area, the temperature of mountain and water are the lowest area, so it is clearly proved that there are obvious UHI effects by stream. The surface temperature distribution of Mushim stream is detected $2^{\circ}C$ lower than urban area.

• 연구논문집
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• 통권27호
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• pp.87-99
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• 1997

Present paper describes on/off design performance of a 50KW turbogenerator gas turbine engine for hybrid vehicle application. For optimum design point selection, relevant parameter study is carried out. The turbogenerator gas turbine engine for a hybrid vehicle is expected to be designed for maximum fuel economy, ultra low emissions, and very low cost. Compressor, combustor, turbine, and permanent-magnet generator will be mounted on a single high speed (82,000 rpm) shaft that will be supported on air bearings. As the generator is built into the shaft, gearbox and other moving parts become unnecessary and thus will increase the system's reliability and reduce the manufacturing cost. The engine has a radial compressor and turbine with design point pressure ratio of 4.0. This pressure ratio was set based on calculation of specific fuel consumption and specific power variation with pressure ratio. For the given turbine inlet temperature, a rather conservative value of $1100^\circK$ was selected. Designed mass flow rate was 0.5 kg/sec. Parametric study of the cycle indicates that specific work and efficiency increase at a given pressure ratio and turbine inlet temperature. Off design analysis shows that the gas turbine system reaches self operating condition at N/$N_{DP}$ = 0.53. Bleeding air for turbine stator cooling is omitted considering low TIT and for a simple geometric structure. Various engine performance simulations including, ambient temperature influence, surging at part load condition. Transient analysis were performed to secure the optimum engine operating characteristics. Surge margin throughout the performance analysis were maintained to be over 80% approximately. Validation of present results are yet to be seen as the performance tests are scheduled by the end of 1998 for comparison.

• 천문학회보
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• 제37권1호
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• pp.73.2-73.2
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• 2012

The far ultraviolet (FUV) wavelength (900-1750A) range includes a wealth of important astrophysical information related to the cooling of hot gas, fluorescent emission from H2 molecules, and starlight scattered off dust particles. Among these, we would like to focus on the scattered emission of the central star by dust with the example of the FUV halo surrounding ${\alpha}$ Vir (Spica). While scattering properties of dust have been studied with the GALEX data, the improved dataset of STSAT-1 revealed many detailed structures of this interesting region. For example, the FUV continuum map obtained from the STSAT-1 observations shows enhanced emission in the southern part of the Spica halo region, where the dust level is also high. In fact, the FUV continuum intensity is seen to have a good correlation with the IRAS 100${\mu}m$ emission data. It is also seen that the scattered spectrum is softer than the original one emitted by the central star, which is attributed to the increase in the dust-scattering albedo with wavelength. We have developed a Monte Carlo code that simulates dust scattering of light including multiple encounters. The code is applied to the present Spica halo region to obtain the scattering properties such as the albedo and the phase function asymmetry factor.

• 대한기계학회논문집B
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• 제26권11호
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• pp.1622-1629
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• 2002

To enhance isothermal characteristics of glass-farming surface, a rectangular parallelepiped heat pipes was fabricated, tested, and analyzed. The working fluid was sodium and the wall material was stainless steel 304. The dimension of the heat pipe was 210 (L) $\times$ 140(W) $\times$ 92(H)mm. A lattice structure covered with screen mesh was inserted to promote return of working fluid. The bottom side of heat pipe was heated electrically and the top side was cooled by liquid circulation. The temperature distribution at the bottom surface was of major concern and was monitored to determine isothermal characteristics. A frozen start-up of rectangular parallelepiped liquid metal heat pipe was tested. The operating mode of the sodium heat pipe was affected by the temperature of cooling zone, input heat flux, and the operating temperature of heat pipe. The heat pipe operated in a normal fashion as long as the heat flux was over 5.78W/cm$^2$, and the inside wall temperature of condenser part was above 95$^{\circ}C$ The maximum temperature difference at the bottom surface was observed to be 32$^{\circ}C$ when the operating temperature of the heat pipe was operating normally around 50$0^{\circ}C$. The result showed that a sodium heat pipe was very effective in reducing significantly the temperature difference in the glass-forming surface.

• 한국기계가공학회지
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• 제15권6호
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• pp.129-135
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• 2016

There have been many types of development and commercialization efforts for superconducting power applications with the continuous development of High Temperature Superconducting (HTS) conductors. In particular, HTS power cables are going to be commercialized in real power grids. A cryogenic refrigeration system should be used to keep it below 77 K, and its required cooling capacity continuously increases as the unit length of the HTS power cable increases. Among the many kinds of cryogenic refrigerator, a reverse Brayton refrigerator that uses turbo expanders is a promising refrigerator due to its efficiency and reliability. Among the various components in refrigerators, the cryogenic turbo-expander is the most important part for increasing efficiency and assuring reliability. The design of a 300 W class turbo-expander is described in this paper prior to the development of a 10 kW class turbo expander, which is the required capability for the commercialization of a HTS power cable. The impeller shape and rotation speed are determined based on the cycle analysis. The Eigen frequency and harmonic analysis are conducted with gas bearings at cryogenic temperatures to determine the operational stability.

• Ocean and Polar Research
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• 제27권1호
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• pp.35-44
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• 2005

The bathymetric and gravity data were obtained in 2001 and 2003 during a survey of seamounts in the northwest of the Marshall Islands, western Pacific. The study areas are located in the Pigafetta Basin which is the oldest part of the Pacific plate and in the Ogasawara Fracture Zone which formed from the spreading ridge between the Izanagi and Pacific plates in the Jurassic. The densities of seamounts and the elastic thickness values of the lithosphere are calculated by using three-dimensional flexure modeling considering the constant sediment layer in the infinite plate model. Very low elastic thickness values (5km), relatively young seamounts, and old lithosphere in the east study area suggest the possibility of the rejuvenation of lithosphere by widespread volcanisms, whereas the elastic thickness values (15km), relatively old seamounts, and young lithosphere of the west study area are suitable for a simple cooling plate model of $300-600^{\circ}C$ isotherm. The gravity residuals of OSM6-1 and OSM6-2 suggest the possibility of different load density or elastic thickness. Relatively older OSM6-2 formed on the younger lithosphere with relatively thin elastic thickness, while younger OSM6-1 on the older lithosphere with relatively thick elastic thickness.

• 대한기계학회논문집A
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• 제20권11호
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• pp.3538-3548
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• 1996

In this study, as a part of basic study for developing the simulation program for the assemssment of reliability of electronic EMC packaging which covers from EMC mixing step to thermal analysis, comparison between a measured and predicted values of material properties of EMC and finitde element analysis of thermal stress are performed. For the experimental testing specimens of fifty, sixty hive and eighty percent filler($13\mu m$, spherical silica) weight fraction are fabricated using tranfer molding. Coefficient of thermal expansion, elastic modulus and thermla conductivity are measured using these specimens and then these measured values are compared with the predicted values by various equations ( such as dilute suspension method. self consistent method, generalized self consistent method, Hashin-Shtrikman's bounds. Shapery's bounds, Nielsen's method and others). Measured values are distributed within the upper and lower bounds of equations. Measured elastic modulus and coefficient of thermal expansion approaches closely the perdicted values with self consisten mehtod and upper bound of Shaperys equation respectively. However small differences of thermal conductivity between the different filler volume fraction are obserbed. FEM analysis indicates that firstly stress is concentrated at the corner section of EMC and secondly EMC with eighty percent filler weight fraction shows less thermal stress when package is cooling down and relatively high thermal stress when package is heating up.

• 에너지공학
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• 제7권1호
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• pp.96-102
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• 1998

원자력 안전계통의 일부분인 컴퓨터의 사용은 일반 산업분야에서 명시되지 않은 부가적인 요건 즉 소프트웨어의 확인 및 검증, 하드웨어의 품질요건이 요구된다. 원자력 발전소에서 사용되는 컴퓨터는 컴퓨터 하드웨어, 소프트웨어, 펌웨어 및 연계장치를 포함하는 시스템이다. 원자력 안전등급을 갖는 컴퓨터 시스템을 개발하기 위해서는 우선적으로 개발환경이 요구되고 개발된 소프트웨어는 원자력 코드 및 표준에 따라 확인 및 검증되어야 한다. 이러한 요건 때문에 원자력 발전소 안전계통의 하나인 부적절노심감시계통에 대한 시험설비가 개발되었다. 시험설비는 입출력 모의설비, 자료수집계통 케비넷 및 감시컴퓨터의 3부분으로 구성된다. 이 시스템의 성능을 수동시험절차에 따라 검증되었다.

• 한국환경과학회지
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• 제28권12호
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• pp.1147-1156
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• 2019

The purpose of this study was to analyze examples of green infrastructure presented by the American Society of Landscape Architects as a part of basic research to assess hub green spaces in cities. With the specific goal of green infrasturcture in mind, the study samples were classified according to their purpose: 'humanities', 'hydrology', 'ecology', and 'environment'. Based on this we assessed the elements of planning for the target sites and obtained the following results. With regard to the aspect of humanities, planning urban hub green spaces was related to the satisfaction in leisure activities and the 'quality of life' that people expect to enjoy at parks or other green areas in general. Rather than focusing on direct and visible benefits, which might come from green infrastructure's technological elements, people hoped that parks and green areas have macroscopic values. For hydrological characteristics, the 'ecologically manages stormwater' was applied the most in planning hub green spaces in cities, and it mainly took the form of technological elements or factors. Third, the planning elements pertaining to ecological characteristics were identified as a combination of strategies and technological elements that 'reintroduces native plants' and 'habitat for wildlife'. As for the plans to instill eco-friendly aspects, the study found that the research on air, climate, weather, heat reaction, soil, energy efficiency, and use and application of resources is important. However, it was difficult to measure the potential quantitative benefits of 'reusing or recycling materials', 'reducing urban heat', and 'cooling air temperature'. The result of this study is meaningful in that it can be used for the assessment of urban hub green spaces in the future.

• 한국의류산업학회지
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• 제19권1호
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• pp.90-100
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• 2017

In this research, consumer awareness investigation and wearing test were carried out for obtaining useful data on the development of thermo-sensitive functional clothing material. A survey involved 216 people in Seoul and Kyeonggi-do, and 200 questionnaires data were analyzed by descriptive statistics and frequency using SPSS 17.0. Four healthy men in twenties were participated for wearing test. Subjects in normal loungewear were exposed to temperature change from the initial temperature $30^{\circ}C$ down to $5^{\circ}C$ for an hour in a climate chamber. The environmental temperature, surface temperature of garment and skin were measured. As a result, most of respondents have all season clothing products such as underwear, hosiery, and jogging suit for loungewear. Also, thermo regulator y functional clothes are frequently used as underwear and sweat shirt. The consumer awareness investigation on thermo regulatory functional clothing showed that the most important key buying factor is quick climate temperature response, easy maintenance, design and cost, in that order. Surface temperature of garment went down with the cooling down of environmental temperature. The lower environmental temperature, the greater temperature difference by body part showed. Skin temperature change by environmental temperature showed similar tendency of garment surface temperature. In comparison between garment surface and body skin, temperature difference became larger under the lower environmental temperature.