• Nuclear Engineering and Technology
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• 제32권2호
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• pp.142-156
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• 2000

An experimental study of steam condensation on a subcooled thick water layer (0.018 ~0.032 m) in a countercurrent stratified flow has been performed using a nearly horizontal circular pipe. A total of 103 average interfacial condensation heat transfer coefficients were obtained and parametric effects of steam and water flow rates and the degree of subcooling on condensation heat transfer were examined. The measured local temperature and velocity distributions in the thick water layer revealed that there was a thermal stratification due to the lack of full turbulent thermal mixing in the lower region of the water layer Two empirical Nusselt number correlations, one in terms of average steam and water Reynolds numbers, and the water Prandtl number, and the other in terms of the Jakob number in place of the Prandtl number, which agree with most of the data within $\pm$ 25%, were developed based on the bulk flow properties. Comparisons of the present data with existing correlations showed that the present data were significantly lower than the values predicted by existing correlations.

• 제어로봇시스템학회논문지
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• 제19권10호
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• pp.907-914
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• 2013

A FastSLAM is an algorithm for SLAM (Simultaneous Localization and Mapping) using a Rao-Blackwellized particle filter and its performance is known to degenerate over time due to the loss of particle diversity, mainly caused by the particle depletion problem in the resampling phase. In this paper, the GeSPIR (Geographically Stratified Particle Information-based Resampling) technique is proposed to solve the particle depletion problem. The proposed algorithm consists of the following four steps : the first step involves the grouping of particles divided into K regions, the second obtaining the normal weight of each region, the third specifying the protected areas, and the fourth resampling using regional equalization weight. Simulations show that the proposed algorithm obtains lower RMS errors in both robot and feature positions than the conventional FastSLAM algorithm.

• Nuclear Engineering and Technology
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• 제44권1호
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• pp.33-42
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• 2012

In the present study, CFD is employed to investigate phenomena occurring during a process of thermal stratification in U-bent pipes at transitional Reynolds number. URANS evaluation had been chosen for its low computational costs during transient analysis and for the evaluation of modeling performance in these conditions. Application of CFD at transitional Reynolds number and buoyancy driven flows indeed contains deeper uncertainties in relation to the range of applicability for hydrodynamic and thermal models. The methodology applied in the work points out, through validations with the basic problems constituting the complex stratified phenomenon, the applicability of the current turbulence modeling. Accurate predictions have been found in relation to transitional Reynolds number in bent pipes and region of stability induced by the gravitational field. On the other hand the defects introduced in the unstable region of the U bent pipe, are discussed in relation to the adopted modeling.

• 천문학회보
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• 제36권1호
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• pp.88.2-88.2
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• 2011

The far-ultraviolet (FUV) continuum and spectral images of C IV and H2 emission lines for the region of Orion-Eridanus Superbubble (OES) are hereby presented and compared with the maps obtained in other wavelengths. While the region shows complex structures, consisting of hot gases and cold dust, a close examination reveals that the FUV emission in this region can be understood reasonably as the result of their interactions. We confirm the origin of most diffuse FUV continuum to be starlight scattered by dust, but we also find that the ionized gas also contributes 50-70% of the total FUV intensity in the regions of H_alpha arcs. We note the bright diffuse FUV continuum in the eastern part of the northern dust-rich region, and attribute it to the bright early-type stars more abundant in this region than in the west as the amount of dust itself does not seem to be much different across 'arc A' that separates the two regions. In addition, two P Cygni-type stars are identified in this eastern region and their peculiar spectral profiles around the C IV emission line are anifested in the scattered diffuse spectrum. Besides this, the C IV emission is generally enhanced at the boundaries of the hot X-ray cavities where thin dust regions are located, confirming the thermal interface nature of the origin of this cooling emission line. The morphology of the H2 emission shows a general correlation with dust extinction features but its intensity peaks are rather located in thin dust areas, off the peak dust regions. Furthermore, H2 emission is seen to be weak in the arc A region though the arc passes through the center of the dust-rich area. Hence, the H2 emission and dust features, together with those of X-ray and ion lines emissions, show stratified structure of arc A quite well, again confirming its thermal interface nature.

• 한국수산과학회지
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• 제17권2호
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• pp.83-91
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• 1984

$1982{\sim}83$년과 $1966{\sim}70$년의 해양관측자료를 사용하여 하계 우리나라 서해 연안에서 형성되는 조석전선의 형성원인과 그 위치 및 구조를 조사하였다. 하계에 형성되는 전선은 조류에 의한 해저 난류로 연직혼합이 일어나는 곳과 외해와의 경계성이며, 그 위치는 수온, 염분, 용존산소의 수평경도와 수색 및 투명도로써 조사한 결과, G선($35^{\circ}31^'N$)과 S선($35^{\circ}25^'N$)의 연안에서 약 20mile 떨어진 해역이었다. 성층상태를 고려한 위치에너지는 V=10 $Joule/m^3$였으며, 수온, 염분, 용존산소와 수색 및 투명도로 조사한 전선의 위치는 이와 대체로 일치하였다. 따라서 이 역을 경계로 연안쪽은 물리, 화학적인 특성이 연직적으로 균일한 혼합층을 형성한다. 외해쪽에는 수면에서 약 $10{\sim}20m$까지 표면 혼합층, 약층, 그리고 저층 혼합층의 순으로 수괴의 구조가 형성되 어 있다. 동계에는 서해 전역이 표면냉각으로 인하여 전 해역에서 연직혼합이 일어나므로 하계의 구조와 같은 전선은 명확하게 형성되지 않는다.

• 대한기계학회논문집B
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• 제30권5호
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• pp.465-471
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• 2006

Controlled auto-ignition(CAI) combustion, offers the potential to improve fuel economy and reduce emission simultaneously. In this study, CAI-combustion was achieved in a single cylinder gasoline DI engine with modified camshafts in order to restrict the gas exchange process. We investigated the effects of air-fuel ratio, residual EGR rate and injection timing such as early injection and late injection on the attainable CAI combustion region. The effect of injection timings on combustion characteristic such as start of combustion, combustion duration and heat release rate was also investigated. From the result early injection causes the mixture to ignite earlier and burn more quickly due to the exothermic reaction during the recompression and gives rise to good mixing of the fuel/air. On the other hand, late injection extended the operation region more than early injection but the emissions of HC and NOx were more or less increased than early injection.

• 한국환경과학회지
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• 제6권6호
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• pp.563-578
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• 1997

The purpose of this study is to suggest the estimation model of' amenity environment' by Perceived Envionmental Quality Index(PEQI) model. A questionnaire survey was carried out for 연e study area of Taegu-Kyungbuk region. Sampling size was 838(427 of Taegu and 411 of Kyungbuk residents by stratified sampling of each region's(7 Gu for Tae-gu, 7 Cities 61 Gun far Kyungbuk) population. The survey was done during Sep. to Nov, of 1996. The suggested model was composed of four estimation categories and 16 Indicators. The four categories were 'Cleanness 61 Quietness', 'Naturalness & Harmony', 'Beauty 61 Comfort' and 'Environmental Conservation Efforts'. And each category has several individual Indicators. The weighted means of satisfaction were different by each region. Suseong-gu, Dalseogu, Joong-gu(Taegu), Bumcheon, Andong, and Cheondo(Kyungbuk) showed high enoronmental satisfaction, but Dong-gu. Seo-gu(taegu), Youngcheon, and Pohang(Kyungbuk) showed lower environmental satisfaction. By Analytic Hierarchy Process(AHP) of weighting values for each categorirs, 'Enoronmental Conservation Efforts' was estimated as the most Important(value of 0.367), and 'Naturalness 61 Harmony'(0. 242),'Clenness & guletness'(0.225), and 'Beauty & Comfort'(0.166) were Important respectively. Total PEQI's were estimated as 48.0 for Taegu, and 53.3 for Kyungbuk. PEQI's for each regions were between 46.2(Dong-gu) and 59.9(Kimcheon). The validity of the suggested model was verined by factor analysis. The four factors were identnied as the same categories and indicators. Finally, The LISREL+7 model was suggested as estimauon model of 'Amenity Environment' for Taegu-Kyungbuk region.

• 한국산림과학회지
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• 제105권1호
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• pp.63-72
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• 2016

본 연구는 산림자원 유용식물인 곰취 종자의 채집지역(강원도 봉평 해발 690 m, 제주도 한라산해발 1,085 m), 전처리(저온습윤처리, 증류수 및 $GA_3$ 침지처리) 및 차광처리(50%, 80%, 대조구)가 발아율, 유묘 특성 및 분화묘 활착에 미치는 영향을 조사하기 위해 수행되었다. 그 결과 곰취 종자의 발아율 범위는 6.9~75.5%였으며, 이 중 강원도 봉평지역에서 수집한 곰취 종자(강원곰취)의 발아율 범위는 6.9~32.8%, 한라산에서 수집한 곰취 종자(한라곰취)의 발아율 범위는 22.2~75.5%이었다. 강원곰취는 저온습윤처리와 증류수 침지처리 후 차광처리 대조구에서 가장 높은 발아율(32.8%)을 나타낸 반면, 한라곰취는 저온습윤처리와 $GA_3$ 100 ppm 침지처리 후 80% 차광처리에서 가장 높은 발아율(75.5%)을 나타내었다. 유묘활력지수의 경우 강원곰취와 한라곰취 모두 저온습윤처리와 증류수 침지처리 후 50% 차광처리에서 가장 우수하였다. 분화묘 생육특성의 경우, 한라곰취는 모든 차광처리에서 100% 적응하여 활착한 반면, 강원곰취는 차광처리가 높아짐(대조구, 50%, 80%) 에 따라 활착률이 77.8%, 61.1%, 55.6%로 감소하였다. 따라서 본 연구에서 곰취 종자로부터 우수한 유묘 생산과 분화묘 활착을 위해서는 한라곰취종자를 저온습윤처리하여 증류수 침지 후 파종하여 50% 차광처리에서 발아시키고 이를 분화묘로 이식하는 것으로 나타났다.

• 대한설비공학회지:설비저널
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• 제17권4호
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• pp.382-394
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• 1988

Dynamic characteristics of thermally-forced stratification process in a square enclosure with a linear temperature profile at the side walls have been investigated through flow visualization experiment and numerical analysis. The experiment was performed on air with the Rayleigh numbers of order $10^5$. A particle tracer method is used for the flow visualization and to obtain a sudden linear temperature profile at the side walls copper blocks which already have a linear temperature profile are come into contact with the thin copper plates of the test section. Immediately a meridional circulation is developed and heat transfer takes place from the wall to the interior region by circulation of fluid and finally a thermal stratification is achieved. In the numerical study, QUICK scheme for convective terms, SIMPLE algorithm for pressure correction, and the implicit method for the time marching are adopted for the integration of conservation equations. Comparison of flow visualization and numerical results shows that the developing flow patterns are very similar in dynamic nature even though there is a time lag due to the inevitable time delay in setting up a linear temperature profile. For high Rayleigh numbers, the oscillatory motion is likely to take place and stratified region is extended. However, initial temperature adjustment process is much slower than that for low Rayleigh numbers.

• Environmental Analysis Health and Toxicology
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• 제31권
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• pp.3.1-3.11
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• 2016

Objectives This study was conducted to describe the regional malaria incidence in relation to the geographic and climatic conditions and describe the effect of altitude on the expansion of malaria over the last decade in Papua New Guinea. Methods Malaria incidence was estimated in five provinces from 1996 to 2008 using national health surveillance data. Time trend of malaria incidence was compared with rainfall and minimum/maximum temperature. In the Eastern Highland Province, time trend of malaria incidence over the study period was stratified by altitude. Spatio-temporal pattern of malaria was analyzed. Results Nationwide, malaria incidence was stationary. Regionally, the incidence increased markedly in the highland region (292.0/100000/yr, p =0.021), and remained stationary in the other regions. Seasonality of the malaria incidence was related with rainfall. Decreasing incidence of malaria was associated with decreasing rainfall in the southern coastal region, whereas it was not evident in the northern coastal region. In the Eastern Highland Province, malaria incidence increased in areas below 1700 m, with the rate of increase being steeper at higher altitudes. Conclusions Increasing trend of malaria incidence was prominent in the highland region of Papua New Guinea, while long-term trend was dependent upon baseline level of rainfall in coastal regions.