• International Journal of Aeronautical and Space Sciences
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• 제13권3호
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• pp.361-368
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• 2012

This paper presents an approach on the design of a nonlinear controller to track a reference velocity for an air-breathing supersonic vehicle. The nonlinear control scheme involves an adaptation of propulsive and aerodynamic characteristics in the equations of motion. In this paper, the coefficients of given thrust and drag functions are estimated and they are used to approximate the equations of motion under varying flight conditions. The form of the function of propulsive thrust is extracted from a thrust database which is given by preliminary engine input/output performance analysis. The aerodynamic drag is approximated as a function of angle of attack and fin deflection. The nonlinear controller, designed by using the approximated nonlinear control model equations, provides engine fuel supply command to follow the desired velocity varying with time. On the other hand, the stabilization of altitude, separated from the velocity control scheme, is done by a classical altitude hold autopilot design. Finally, several simulations are performed in order to demonstrate the relevance of the controller design regarding the vehicle.

• 한국환경과학회지
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• 제23권6호
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• pp.1067-1074
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• 2014

Life Cycle Assessment(LCA) has been carried out to evaluate the environmental impacts of glass bottle recycle. The LCA consists of four stages such as Goal and Scope Definition, Life Cycle Inventory(LCI) Analysis, Life Cycle Impact Assessment(LCIA), and Interpretation. The LCI analysis showed that the major input materials were water, materials, sand, and crude oil, whereas the major output ones were wastewater, $CO_2$, and non-hazardous wastes. The LCIA was conducted for the six impact categories including 'Abiotic Resource Depletion', 'Acidification', 'Eutrophication', 'Global Warming', 'Ozone Depletion', and 'Photochemical Oxidant Creation'. As for Abiotic Resource Depletion, Acidification, and Photochemical Oxidant Creation, Bunker fuel oil C and LNG were major effects. As for Eutrophication, electricity and Bunker fuel oil C were major effects. As for Global Warming, electricity and LNG were major effects. As for Ozone Depletion, plate glasses were major effects. Among the six categories, the biggest impact potential was found to be Global Warming as 97% of total, but the rest could be negligible.

• International Journal of Railway
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• 제5권2호
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• pp.55-64
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• 2012

Subject of the paper is a particular configuration of overhead line, in which noise barrier structure is used as supports of the catenary instead of standard poles. This configuration is foreseen in case the noise barrier position is in conflict with the poles location. If the catenary is supported by the noise barrier, the motion that the latter undergo due to wave pressure associated to train transit is transmitted to the overhead line, so that potentially it influences the interaction between the catenary itself and the pantograph of the passing train. The paper focuses on the influence of such peculiar configuration on the quality of the current collection of high speed pantograph, for single and double current collection. The study has been carried out first with an experimental investigation on the pressure distribution on noise barrier, both in wind tunnel and with in-field tests. Subsequently a numerical analysis of the dynamics of the barrier subjected to the wave pressure due to train transit has been carried out, and the output of such analysis has been used as input data for the simulation of the pantograph-dynamic interaction at different speeds and with front or rear pantograph in operation. Consideration of structural modifications was then highlighted, in order to reduce the influence on the contact loss percentage.

• International Journal of Fluid Machinery and Systems
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• 제9권1호
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• pp.47-55
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• 2016

The portable hydraulic turbine we previously developed for open channels comprises an axial flow runner with an appended collection device and a diffuser section. The output power of this hydraulic turbine was improved by catching and accelerating an open-channel water flow using the kinetic energy of the water. This study aimed to further improve the performance of the hydraulic turbine. Using numerical analysis, we examined the performances and flow fields of a single runner and a composite body consisting of the runner and collection device by varying the airfoil and number of blades. Consequently, the maximum values of input power coefficient of the Runner D composite body with two blades (which adopts the MEL031 airfoil and alters the blade angle) are equivalent to those of the composite body with two blades (MEL021 airfoil). We found that the Runner D composite body has the highest turbine efficiency and thus the largest power coefficient. Furthermore, the performance of the Runner D composite body calculated from the numerical analysis was verified experimentally in an open-channel water flow test.

• 한국유기농업학회지
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• 제29권4호
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• pp.459-469
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• 2021

Until now, research on inter-Korean economic cooperation and economic integration has been limited to the areas of the two Koreas. However, Korea is connected with many countries in Asia through the global value chain. Thus, if inter-Korean trade deepens, it may affect the trade structure of neighboring countries. In order to establish a specific inter-Korean economic integration policy when North Korea becomes a normal state in the future, an analysis that reflects the trade structure including Northeast Asia must be preceded. Therefore, in this paper, the impact of inter-Korean trade on Korea, China and Japan was analyzed using the international input and output table containing actual trade data. The scope of analysis was limited to agriculture, reflecting North Korea's demand for economic cooperation. The results show that trade in the agricultural sector between the two Koreas did not have a significant effect of production and value added. but when China and Japan participate in trade with North Korea, the production effect was calculated to be as high as 4 million dollars in Korea and up to 10 million dollars in Japan. And China showed up to 520 million dollars. In addition, the value-added effect was calculated up to $1 million in Korea, up to $4 million in Japan, and up to $250 million in China.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권6호
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• pp.1044-1055
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• 2015

DPCap analysis can assist in determining the maximum environmental forces the DP system can counteract for a given heading. DPCap analysis results are highly affected by the thrust forces provided by the thrust system which consists of several kinds of thrusters. The thrust forces and moment are determined by the maximum thrust of the thrusters as well as the thruster configuration. In this paper, a novel local optimization of thruster configuration based on a synthesized positioning capability criterion is proposed. The combination of the discrete locations of the thrusters forms the thruster configuration and is the input, and the synthesized positioning capability is the output. The quantified synthesized positioning capability of the corresponding thruster configuration can be generated as the output. The optimal thruster configuration is the one which makes the vessel has the best positioning capability. A software program was developed based on the present study. A local optimization of thruster configuration for a supply vessel was performed to demonstrate the effectiveness and efficiency of the program. Even though the program cannot find the global optimal thruster configuration, its high efficiency makes it essentially practical in an engineering point. It may be used as a marine research tool and give guidance to the designer of the thrust system.

• 한국항만경제학회지
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• 제26권1호
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• pp.131-143
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• 2010

본 논문은 세계 주요 컨테이너 항만의 효율성을 분석하기 위해 Containerisation International Yearbook에 수록된 컨테이너 항만 가운데 컨테이너 물동량 처리기준(2007년)으로 20대 항만을 선정하여 DEA(CCR, BCC, 규모효율성)분석을 실시하였다. 항만의 효율성에 영향을 미칠 수 있는 변수를 국내외 기존 연구를 참고하여 선정하였다. 투입변수는 선석수, 수심, 크레인수, 총면적을, 산출변수는 컨테이너 화물처리량을 선정하였다. 분석결과를 요약하면, 첫째, DEA-CCR효율성은 선전항(중국)이 1.0으로서 분석대상 항만 중 가장 효율적인 항만으로 분석되었다. 둘째, DEA-BCC효율성을 분석한 결과 싱가포르, 선전항(중국), 닝보(중국), 탄중펠레파스(말레이시아)가 효율성 1.0으로서 분석대상 항만 중 효율적인 항만으로 분석되었다. 셋째, 규모의 효율성 분석결과는 선전항(중국) 만이 2004년부터 2007년까지 4년 연속효율성 1.0으로서 분석대상 항만 중 가장 효율적인 항만으로 분석되었다.

• 한국산학기술학회논문지
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• 제20권9호
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• pp.323-332
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• 2019

본 연구의 목적은 제주국제관악제에 대한 지역경제파급효과를 측정하는 데 있다. 이를 위하여 '2013년 제주지역 투입산출표'에 기반 한 두 지역(제주-전국) 산업연관모형을 활용하여 제주국제관악제 개최로 인한 지역경제에 파급되는 효과를 알아보았다. 또한 지역에 미치는 효과를 알아보기 위하여 2017년과 2018년 비교를 통하여 제주국제관악제가 얼마나 성장하고 지역경제에 어떠한 효과를 주는지 비교해보았다. 제주국제관악제 개최에 투입된 투자 지출액을 분석한 지역 내 유발된 산업의 생산, 부가가치 효과분석 결과를 비교해보면 생산유발효과는 2017년 9,056,430천원이고 2018년 18,709,179천원으로 2.1배가 증가하였다. 부가가치유발효과는 2017년 4,229,480천원이고 2018년 9,199,030천원으로 2.2배 증가하였다. 분석결과를 살펴보면 제주국제관악제는 지역주민의 소득증대에 많은 기여를 하고 있음을 알 수 있다. 이를 활용하여 관악제의 효과를 높이기 위해서는 제주지역 문화와 관광지를 연결하는 정책들이 필요할 것이다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권4호
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• pp.559-568
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• 2013

Increased worldwide concerns about fossil fuel costs and effects on the environment lead many governments and scientific societies to consider the hydrogen as the fuel of the future. Many researches have been made to assess the suitability of using the hydrogen gas as fuel for internal combustion engines and gas turbines; this suitability was assessed from several viewpoints including the combustion characteristics, the fuel production and storage and also the thermodynamic cycle changes with the application of hydrogen instead of ordinary fossil fuels. This paper introduces the basic environmental differences happening when changing the fuel of a marine gas turbine from marine diesel fuel to gaseous hydrogen for the same power output. Environmentally, the hydrogen is the best when the $CO_2$ emissions are considered, zero carbon dioxide emissions can be theoretically attained. But when the $NO_x$ emissions are considered, the hydrogen is not the best based on the unit heat input. The hydrogen produces 270% more $NO_x$ than the diesel case without any control measures. This is primarily due to the increased air flow rate bringing more nitrogen into the combustion chamber and the increased combustion temperature (10% more than the diesel case). Efficient and of course expensive $NO_x$ control measures are a must to control these emissions levels.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2010년도 춘계 학술논문 발표대회 1부
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• pp.243-246
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• 2010

Recently, global warming problem is a major issue in international community. The carbon dioxide ($CO_2$) emissions in the construction industry is one of the main factors causing a global warming problem. Accordingly, various researches on $CO_2$ emissions caused by the construction industry is needed and construction methods which is low $CO_2$ emissions should be developed. In this study, $CO_2$emission cost is compared with roof waterproofing types in construction phase. As a result, the $CO_2$ emission costs of asphalt waterproofing is the highest. This research is to provide basic information for selecting appropriate construction methods in aspect of low $CO_2$ emission cost.