• Journal of Biosystems Engineering
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• 제5권1호
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• pp.43-50
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• 1980

The milling plants in Korea have been generally used the paddy-separator that operated in accordance with the principle of sieving action. This type of paddy separator was considered as inefficient, especially in relation to the new high-yielding varieties which have different size characteristics within their varieties and also as compared to traditional varieties. With the installation of modern paddy separator it may be possible to increase the overall milling system efficiency and to reduce the grain loss. This study was intended to identify and define important parameters required for assessing the separation performance of a tray-type paddy separator and to determine the optimum conditions of the inclination of separator-table. The results of the study were summarized as follows : (1) Separation performance can be given by use of many parameters found from the measurement of separator outputs. such as upper-tail recovery $(\varepsilon)$, purity of upper-tail $(\gamma)$ , separation recovery of brown rice $(\alpha)$, separation recovery paddy $(\beta)$, and efficiency of separator $(\epsilon)$, Among these para-meters , $\varepsilon$, $\gamma$, $\alpha$ and $\beta$, were designated , respectively, their independent properties of the paddy separator. In addition, their modes of variation due to a varied inclination of the separation table did not indicated in the same direction . However, the efficiency of separator had an advantage to indicate the overall characteristics of the separator performance with a clear optimum inclination condition of the separator table. (2) The optimum feed rate and maximum efficiency of the separator did not occur at the identical inclination of the separator table. Thus, for its practical operation it is necessary to compromise between the qualitative and quantitative performances of the separator. (3) The optimum setting of the separator table tested in the study showed to occur at its inclination of approximately $26^\circ<$/TEX> for the front and $8^\circ<$/TEX> for lateral.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권1호
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• pp.1-7
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• 2004

This paper presents a sensorless control strategy of a PMSM(Permanent Magnet Sycchoronous Motor). This method is very simple to compute the position angle of a rotor. A principle and a practical solution are described. A sensorless control algorithm is proposed to remove a mechanical position sensor. The theory is based on the superposition principle. The state equation of a motor is divided into two conditions: one is the state equation of exciting voltage and phase current in a constraint, the other is the state equation of back EMF(Electromotive Force) and phase current in a short circuit. Based on the analysis, short circuit current by back EMF is computed and then the information of position angle is calculated. The proposed method is verified by experimental results.

• 미국학
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• 제41권1호
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• pp.99-131
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• 2018

The United States of America is privileged in that social stratification is not directly linked to the division of powers. Nonetheless, America endured the devastating Civil War only to consolidate her national identity when a nation was not defined. In fact, state governments preexisted as a sovereign long before the federal government came into existence as a national government. As a consequence, intergovernmental relations have persistently been contested long after the Civil War ended. In contrast, the European Union was founded on the political will to establish regional integration such that her member states would never repeat the bloodshed in catastrophic wars. Since the principle of subsidiarity precipitated political endeavor in regional integration, the EU developed into a bifurcated system of transnational and international organizations. In this paper, I evaluate the US and the EU by applying the perspective of federalism in which separation and integration are perennially at tension.

• Environmental Engineering Research
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• 제16권1호
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• pp.35-39
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• 2011

An integrated gasification combined cycle (IGCC) system has been attracting attention due to its increased energy conversion efficiency and ability to treat various carbonaceous materials. IGCC is also expected to play an important role in the future supply of hydrogen energy. The use of a palladium-based membrane to separate the hydrogen from the synthesis gas stream has been intensively studied due to its exceptional hydrogen-separating capability. However, theoretical research on hydrogen separation is still an unfamiliar area in Korea. First-principle density functional theory was applied in this study to investigate the dissociative adsorption of hydrogen onto a palladium surface. The stability of hydrogen on the surface was theoretically evaluated with various adsorption configurations, partial pressures and temperatures. Further theoretical and experimental studies were also suggested to find a more hydrogen-selective material.

• Structural Engineering and Mechanics
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• 제2권3호
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• pp.295-309
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• 1994

The present paper concerns the mathematical study and the numerical treatment of the problem of semirigid connections in bolted steel column base plates by taking into account the possibility of appearance of separation phenomena on the contact surface under certain loading conditions. In order to obtain a convenient discrete form to simulate the structural behaviour of a steel column base plate, the continuous contact problem is first formulated as a variational inequality problem or, equivalently, as a quadratic programming problem. By applying an appropriate finite element scheme, the discrete problem is formulated as a quadratic optimization problem which expresses, from the standpoint of Mechanics, the principle of minimum potential energy of the semirigid connection at the state of equilibrium. For the numerical treatment of this problem, two effective and easy-to-use solution strategies based on quadratic optimization algorithms are proposed. This technique is illustrated by means of a numerical application.

• International Journal of Aeronautical and Space Sciences
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• 제16권4호
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• pp.602-613
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• 2015

As one of the mission payloads to be verified through the cube satellite mission of Cube Laboratory for Space Technology Experimental Project (STEP Cube Lab), we developed a hinge driving separation nut-type holding and releasing mechanism. The mechanism offers advantages, such as a large holding capacity and negligible induced shock, although its activation principle is based on a nylon cable cutting mechanism triggered by a nichrome burn wire generally used for cube satellite applications for the purpose of holding and releasing onboard appendages owing to its simplicity and low cost. The basic characteristics of the mechanism have been measured through a release function test, static load test under qualification temperature limits, and shock measurement test. In addition, the structural safety and operational functionality of the mechanism module under launch and on-orbit environments have been successfully demonstrated through a vibration test and thermal vacuum test.

• 한국철도학회논문집
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• 제11권3호
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• pp.263-271
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• 2008

본고는 철도선진국의 선로사용료가 어떻게 징수되고 있는가를 보고 한국철도에 대한 정책적 임플리케이션을 도출하는 것이다. 북미, 일본의 경우, 거액의 인프라스트럭처 정비비용의 일부를 회수하기 위해 선로사용료의 징수가 채산성의 관점에 징수된다. 반면, 유럽에서는 운행주체와 인프라스트럭처주체가 회계상 완전히 분리되어 한계비용 + 적정이윤 (MC+) 원칙에 따라 선로사용료가 책정된다 이에 대해, 한국에서는 Korail이 유지보수뿐만 아니라 고속철도 건설비 상환을 담당하고 있다. 이러한 점에서 상하분리방식을 포함한 철도개혁에 대한 재고가 필요하다.

• 멤브레인
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• 제7권2호
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• pp.57-64
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• 1997

새로운 분리공정으로서 Membrane Distillation(MD)에 대하여 고찰하였다. 정밀여과에서 이용되고 있는 소수성막이 MD공정에 적합한 막소재가 된다. MD는 고온보다는 완화된 온도에서 100%에 가까운 선택도를 가지면서 기존의 수처리 공정을 간소화시킬 수 있는 가능성이 있다. MD는 막표면의 기공에서 층기-액체간의 상분리가 일어나는 분리원리를 이용한다. 공급액 및 투과액의 온도, 조성, 막의 젖음현상, 열 및 물질전달이 MD의 선택도와 플럭스를 결정할 수 있다.

• 환경영향평가
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• 제7권1호
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• pp.109-116
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• 1998

As of July 1997, the registered number of automobiles exceeded 10 million and Korean auto industry produced 2,850,000 cars. Many environmentalists warn that the passenger cars are not sustainable urban transportation system in large cities. The cars produce about 80% of air pollutants, and consume 30% of petroleum imported. For the past 30 years the administration increased the road system, but the length of road per car is decreased from 813m in 1965 to 9m in 1995. The cost of traffic congestion was estimated to be \14.7 trillion in 1996, and is feared to increase without changing the present transportation system. The undesirable impact of cars include the casualties from traffic accidents, insurance loss, and separation of human relatioships. To construct sustainable urban transportation system, three principles should be followed. The first principle is to make the urban streets walkable for the people. The second principle is to encourage bicycling. Roads and traffic systems should be designed to let bicylces travel safely. The third principle is to supply more buses and construct integrated transportation system based on buses. The subway system is too expensive to construct and without the support of a well-organized bus system it may not work efficiently. The Brazilian city of Curitiba has constructed a very efficient bus system only with 1/80 of the estimated cost of subway system. The car-oriented transportation system does not seem to be an envrironmentally sustainable transportation system in most of the Korean cities.

• Bulletin of the Korean Chemical Society
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• 제30권10호
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• pp.2287-2293
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• 2009

Gas Chromatography-Mass Spectrometry (GC-MS) fingerprint analysis, Principle Components Analysis (PCA), and Hierarchical Cluster Analysis (HCA) were introduced for quality assessment of Curcuma longa L. (C. longa). The GC-MS fingerprint method was developed and validated by analyzing 33 batches of samples of C. longa from different geographic locations. 18 chromatographic peaks were selected as characteristic peaks and their relative peak areas (RPA) were calculated for quantitative expression. Two principal components (PCs) were extracted by PCA. C. longa collected from Guizhou and Fujian were separated from other samples by PC1, capturing 71.83% of variance. While, PC2 contributed for their further separation, capturing 11.13% of variance. HCA confirmed the result of PCA analysis. Therefore, GC-MS fingerprint study with chemometric techniques provides a very flexible and reliable method for quality assessment of C. longa.