• 한국유통학회지:유통연구
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• 제1권1호
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• pp.41-63
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• 1996

In spite of economy has a critical cycle such as, production, distribution and consumption, we hardly concentrated our study to distributional system and behavior. Especially in Korea, Traditional idea had tried to ignore the people who work in this economic value at all. Manufacturers, other than retailers and wholesalers, had a belief that the manufacturing can control distributional channels forever. Unfortunately, technological and educational advances caused the quality equalization among developing and developed countries as well as among big and small manufacturers in their products. By this reason, economists are searching the economists dark continet' mentioned by Peter Drucker as a new source of wealth. According to a report by well-known economic research institute in Switzerland, Korea has classified in the lower level group in terms of international compatitive power. At the same time, business firms complain that they are suffering from lack of SOC and infrastructures. As an important mean to overcome the economic bottleneck, economists suggest in improve our distributional atmosphere. Basically, distributional study has two sub-fields as: commercial and physical distributions, Distributional system mainly concerns about to shorten the distances of time and space between production and consumption. The closer the distances, the higher efficiency can be achieved. Building distributional system will cost, but tile results will save social costs. Based on this idea, economists proposed several ways to cut the distances and to save costs, Naturally, they hope their beliefs can be adapted by business firms and governments. But frequently, their theories doesn't make any fruit. This paper has studied about the composition of joint transportational and distributional systems. And, even though there's no Marshall in tile real world at this point authors are trying to define the transportational and physical distributional costs, the most powerful factor that can impact to economic decision making.

• International Journal of Vascular Biomedical Engineering
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• 제1권1호
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• pp.41-47
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• 2003

The patency rates of small diameter vascular grafts are disappointing because of the formation of thrombus and intimal hyperplasia. Among the various factors influencing the success of graft surgery, the compliance and the size of a graft are believed to be the most important physical properties of a vascular graft. Mismatch of compliance and size between an artery and a graft alters anastomotic flow characteristics, which may affect the formation of intimal hyperplasia. Among the hemodynamic factors influencing the development of intimal hyperplasia, the wall shear stress is suspected as the most important one. The wall shear stress distributions are experimentally measured near the end-to-end anastomosis models in order to clarify the effects of compliance and diameter mismatch on the hemodynamics near the anastomosis. The effects of radial wall motion, diameter mismatch and impedance phase angle on the wall shear rate distributions near the anastomosis are considered. Compliance mismatch generates both different radial wall motion and instantaneous diameter mismatch between the arterial portion and the graft portion during a flow cycle. Mismatch in diameter seems to be affecting the wall shear rate distribution more significantly compared to radial wall motion. The impedance phase angle also affects the wall shear rate distribution.

• 대한방사선치료학회지
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• 제9권1호
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• pp.71-81
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• 1997

I. Objective and Importance of the Project We have been using MC-50 cyclotron and NT-50 neutron therapy machine for treating cancer patients since 1986 at Korea Cancer Center Hospital. It is mandatory to measure accurately the dose distribution and the total absorbed dose of fast neutron for putting it to the clinical use. At present the methods of measurement of fast neutron are proposed largely by American Associations of Physicists in Medicine (Task Group 18), European Clinical Neutron Dosimetry Group, and International Commission on Radiation Units and Measurements. The complexity of measurement, however, induce the methodological differences between them. In our study, therefore, we tried to establish a unique technique of measurement by means of measuring the emitted doses and the dose distribution of fast neutron beam from neutron therapy machine, and to invent a standard method of measurement adequate to our situation. II. Scope and Contents of the Project For establishing a unique technique of measurement and inventing a standard method of measurement of fast neutron beam, 1. to grasp the physical characteristics of neutron therapy machine 2. to study the principles for measrement of fast neutron beam 3. to get the dose distribution (dose rate, percent-depth dose, flatness etc) throught the actual measurement 4. to compare our data with those being cited world-widely.

• 한국환경과학회지
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• 제11권9호
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• pp.881-895
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• 2002

Sediments and river waters form the channel of Hwasun-cheon were studied in sedimentological size and geochemical analyses of metallic elements for the purposes of identification of depositional environments and geochemical characteristics. The sizes of sediments are assigned to pebble to coarse sand in mean size and polymodal in distribution. And the sediments are poorly to very poorly sorted and positively skewed. According to the grain size distributions of the sediments, the Hwasun-cheon belongs to gravel-bed river on the basis of the grain size distribution of the sediments. The behaviors of metallic elements in the sediments mainly depend on not grain size distribution but the geology connected with geomorphological reliefs near the stream. Contamination indices(CI) of Zn, Cu and Pb are 2.83 to 6.96 with average 4.31 in the sediments. Hwasun-cheon is assigned to general stream type in accordance with water quality of physical factors and chemical characteristics by Piper's diagram. Though meaningful values of BOD, T-N, T-P were locally depicted near Masan-ri, Hwasun-eup and Jiseok-cheon areas, artificial metal concentration do not represent in the most area of the stream. Sediments and river water are considered that the relatively more or less high metallic contents in the stream are originated from coal mine and urban area.

• 한국환경과학회지
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• 제33권6호
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• pp.367-382
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• 2024

Alpine and subalpine plants are isolated and distributed in mountaintop areas at high altitudes and, are among the species most vulnerable to global warming. If the rate of warming continues at its current rate, it is highly likely that this species will be unable to find new refugia and will be the last to go extinct in their current habitats. Therefore, research on the distribution and diversity of alpine and subalpine plants is urgently needed and is important from the perspective of biodiversity conservation. Therefore, this study focused on the distribution of alpine and subalpine plants native to national parks. Alpine and subalpine plants distributed across the 12 national parks accounted for approximately half (47.78%) of all alpine plants in Korea. The average relative frequency of occurrence was 0.23, plant similarity between national parks was 37.19%, and beta diversity was 0.63. The number of species was positively correlated with the latitude, elevation, and area of the national park. Thus the geographical distributions of alpine and subalpine plants haves distinct spatial specificities and physical environmental differences.

• 대한방사선기술학회지:방사선기술과학
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• 제35권2호
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• pp.157-164
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• 2012

본 논문의 목적은 쐐기필터를 사용한 방사선조사면에서 다양한 조직전자밀도가 선량분포에 미치는 영향을 분석하고자 함이다. 구성된 물질에 따라 밀도가 다른 고체 팬텀, 코르크팬텀, 그리고 공기층에서 동적쐐기필터와 금속쐐기필터를 이용하여 선량분포의 변형정도를 평가하였다. 본 실험에서는 매질 내 삽입이 용이하고 우수한 선량특성을 가지고 있는 레디오크로믹 필름(Gafchromic EBT2, International Speciality Products, NJ)을 사용하였다. 선형가속기 6 MV 광자선을 이용해서 $10{\times}10cm^2$ 조사면에 400 MU를 조사하였다. 필름의 선량분포는 선량 분석프로그램을 이용하여 조사면 내 영역과 반음영 영역을 분석하였다. 조직의 밀도가 같을 때 동적쐐기필터와 금속 쐐기필터의 선량분포는 금속 쐐기필터 선량이 동적쐐기필터 선량보다 높게 나타났다. 조직전자밀도가 다른 부위에 쐐기필터의 종류에 따른 선량분포는 고체팬텀과 코르크 팬텀에서 2% 이내 차이를 나타내고 있었다. 그러나 공기층에서 선량분포는 고체팬텀이나 코르크 팬텀의 선량분포와 큰 차이를 보이고 있다. 공기층에서 쐐기필터의 선량분포는 쐐기 사용 효과가 나타나지 않고 있다. 쐐기필터의 두꺼운 부분과 얇은 부분 밖에서 반음영의 크기는 1 cm에서 2 cm 정도 크게 두꺼운 부분에서 크게 나타났다. 그리고 금속 쐐기필터에서 반음영이 동적쐐기필터 보다 평균 6.4%정도 높게 반음영이 나타났다. 본 실험을 통해 공기층과 같이 조직전자밀도 현저히 작은 매질에서는 쐐기필터의 효과가 크게 떨어지는 것과 불균질 물질에 따라 흡수되는 선량분포가 크게 변형되는 것을 알 수 있었다. 따라서 조직전자밀도의 차이가 큰 부위의 방사선치료계획 시 쐐기필터의 적용에 따른 적절한 보정이 이루어져야 한다.

• 한국응용과학기술학회지
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• 제35권4호
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• pp.1327-1337
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• 2018

항공유는 문제가 발생 시 대형사고로 이어질 수 있기 때문에 다른 수송용 연료보다 더 엄격히 관리되고 있다. 항공유의 품질기준은 국내의 한국산업표준(KS), 미국재료협회(ASTM)와 국제운송협회(IATA)에서 각각 규정하고 있다. 2016년부터 2017년까지 국내 정유사의 5개 공장에서 생산되는 항공유에 대하여 방향족 함량, 황 함량 및 증류성상 등 6개 항목에 대하여 품질분석을 실시하였다. 국내에서 생산된 항공유는 품질기준에 적합한 것으로 나타났으며, 연간 일정하게 유지되고 있었다. 국제기준인 ASTM과 IATA의 품질기준과 비교했을 때, 방향족 함량은 국내 KS 기준이 ASTM 및 IATA 설정기준보다 1.5 wt% 엄격하게 설정되어 있으나 이 기준을 충분히 만족시키는 것으로 나타났다. 또한, 황 함량, 증류성상 및 인화점 등 나머지 항목들도 국내와 국제기준을 모두 충족하는 것으로 나타났다.

• 에너지공학
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• 제24권4호
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• pp.24-32
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• 2015

국내외적으로 디젤엔진에 대한 배출가스 규제가 강화되고 있고 다양한 방식의 엔진연소 및 후처리 시스템에 대한 연구가 진행되고 있다. 질소산화물(NOx)의 제거방법으로는 HC-SCR, LNT, Urea-SCR 등이 있으며, Urea-SCR은 높은 변환 효율 및 연비특성으로 향후 NOx의 저감을 위한 유력한 기술로 많은 기술개발이 진행되고 있다. 본 연구에서는 요소함량의 변화에 따른 요소수의 물리적/화학적 특성을 조사하고 배출가스의 특성을 분석하였다. 요소함량의 증가에 따른 요소수의 뷰렛, 알데히드, 인산염 함량은 증가하였으며, 배출가스 중 일산화탄소(CO), 탄화수소(HC) 및 입자상물질(PM)의 배출량 변화는 미미하였다. 질소산화물(NOx)의 배출량은 요소함량이 증가함에 따라 감소하였으며, 30.0 wt%이상의 요소수에서는 질소산화물의 저감효율이 80 %이상을 나타내었다.

• Coupled systems mechanics
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• 제7권4호
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• pp.373-393
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• 2018

This paper is concerned with the wave propagation behavior of rotating functionally graded temperature-dependent nanoscale beams subjected to thermal loading based on nonlocal strain gradient stress field. Uniform, linear and nonlinear temperature distributions across the thickness are investigated. Thermo-elastic properties of FG beam change gradually according to the Mori-Tanaka distribution model in the spatial coordinate. The nanobeam is modeled via a higher-order shear deformable refined beam theory which has a trigonometric shear stress function. The governing equations are derived by Hamilton's principle as a function of axial force due to centrifugal stiffening and displacement. By applying an analytical solution and solving an eigenvalue problem, the dispersion relations of rotating FG nanobeam are obtained. Numerical results illustrate that various parameters including temperature change, angular velocity, nonlocality parameter, wave number and gradient index have significant effect on the wave dispersion characteristics of the understudy nanobeam. The outcome of this study can provide beneficial information for the next generation researches and exact design of nano-machines including nanoscale molecular bearings and nanogears, etc.

• Agribusiness and Information Management
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• 제4권2호
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• pp.1-13
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• 2012

This study aims to subdivide consumers by attributes determined mainly by consumers of fresh ginseng. It is to compare and analyze the characteristics by cluster, and to deduce the implications on distribution and marketing. For this study, a survey was conducted targeting 250 consumers of fresh ginseng. The factors were deduced through performing the exploratory factor analysis on the results of the survey, and the consumers of fresh ginseng were classified through cluster analysis. As a result of the study, the attributes considered for the purchase of fresh ginseng were condensed to the three factors: physical characteristic factor, safety factor, and cultivation indication information factor. With these as the standard, the consumers of fresh ginseng were subdivided into the three clusters: safety-oriented consumption type, label-centered consumption type, and high involvement consumption type. It was found that there were differences in demographic characteristics and attributes considered for purchase of fresh ginseng by cluster analysis. This study suggests the implications for revitalization of the fresh ginseng industry by subdividing consumers of fresh ginseng and suggesting the characteristics by cluster.