• 전기학회논문지P
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• 제65권4호
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• pp.262-267
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• 2016

This paper describes a design of a hair drier to improve its performance. the performance of the hair drier can be improved by increasing the wind velocity of its discharge port. the design of the hair drier is accomplished by using the CFD. the validity of design results were verified by comparison with the dry change of the hair drier. In this paper, the initial condition of the applied hair drier is as follows, the number of the blade is 9, the diameter of the suction port is 40[mm], the tip clearance is 12.5[mm], the con angle is $28.5^{\circ}$ and the fan angle is 27.5R. From design results, the enhanced condition of the hair drier can be obtained as follows, the number of the blade is 3, the diameter of the suction port is 50[mm], the tip clearance is 10.5[mm], the con angle is $21.5^{\circ}$ and the fan angle is 75R. At the enhanced condition of the hair drier, the wind velocity of the hair drier is 29[%] increase, and the dry time is 40[%] increase compare to the initial condition of the hair drier.

• 한국항해항만학회지
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• 제33권1호
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• pp.79-90
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• 2009

컨테이너 터미널의 핵심 기능은 컨테이너 화물을 선반에 싣고 내기는 것이다. 이러한 기능에 대한 생산성을 향상시키기 위해서는 보유한 자원을 효과적으로 사용해야 하는데, 본 연구는 RMGC (rail mounted gantry crane) 유형 야드 크레인의 배치 방안에 대해서 논한다. 먼저, 컨테이너 터미널의 장치계획을 고려한 야드 크레인 배치 문제에 대한 수리모형을 개발한다. 수리 모형은 한 기간 내에서 블록간 야드 크레인의 이동 허용여부에 따라서 2가지로 나누어진다. 제시한 모형을 검증하기 위하여 수치 예제를 풀어서 결과를 분석한다. 또한 장치계획만을 다루는 기존 모형과의 성능 차이를 분석하기 위한 비교 실험을 수행한다.

• 전기학회논문지
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• 제60권2호
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• pp.357-361
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• 2011

The terminal current in voltage driven systems is an essential role for characterizing the pattern of electric discharge such as corona, breakdown, etc. Until now, to evaluate this terminal current, Sato's equation has been widely used in areas of high voltage and plasma discharge. Basically Sato's equation was derived by using the energy balance equation and its final form described physical meaning explicitly. To give more general abilities in Sato's equation, we present a generalized approach by directly using the Poynting's theorem incorporating the finite element method. When the magnetic field effect or the time-dependent voltage source is considered, this generalized energy method can be easily applicable to those problems with any dielectric media such as gas, fluid, and solid. As an alternative approach, the integral Ohm's law resulting in small numerical errors has an ability to be applied to multi-port systems. To test the generalized energy method and integral Ohm's law, first, the results from two prosed methods were compared to those from Sato's approach and an analytic solution in parallel plane electrodes. After verification, the generalized method was applied to the tip-sphere electrodes for evaluating the terminal current with three carriers and the Fowler-Nordheim field emission condition. From these results, we concluded that the generalized energy method can be a consistent technique for evaluating the discharge current with various dielectric materials or large magnetic field.

• 한국해양공학회지
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• 제32권4호
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• pp.272-278
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• 2018

Recently, the use of hazardous chemicals has been continuously increasing. Therefore, the international trade volume is growing and chemical accidents have increased. Nowadays, the safety awareness of the public has increased. As a result, the management and supervision of hazardous chemicals have been strengthened. However, the port policy of Korea has focused on increasing the volume of cargo through facility development. Thus, the port management of hazardous chemicals has been relatively neglected. For national economic growth and society, the port management of hazardous chemicals should be considered to efficiently ensure safety and economic growth. Therefore, this study assumed scenarios where hazardous materials were moved in a dangerous container, not only on appropriate wharfs but also in ports that were close to a big city. The BTX substances were selected among the toxic chemicals with large import and export volumes, and the risk distance and damage effects were predicted using various risk assessment programs. It is expected that this could be used to improve a port safety management system and could be utilized to determine the safety distance in case of an accident.

• Journal of Advanced Marine Engineering and Technology
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• 제40권9호
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• pp.756-761
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• 2016

본 연구에서는 소형 단기통 4행정 농용 디젤엔진에 장착될 수 있는 플런저 직경 4 mm, 행정 7 mm의 연료펌프를 설계 및 제작하여 성능특성을 조사하는 것이 목적이다. 실린더 내 연소압력은 자체 제작한 모형 실린더 내에 질소가스를 사용하여 1, 6, 11, 16 및 21 bar의 배압을 형성시켜 모사했다. 실험에 있어서는 연료펌프 회전속도를 600, 800, 1000, 1200 및 1400 rpm로 변화시키면서 개발된 연료펌프의 토출구에서 1 cm 떨어진 지점의 토출압력, 30 cm 떨어진 지점의 송출압력과 송출유량을 배압에 대해 측정하였고, 펌프효율을 계산하였다. 그 결과, 연료펌프 회전속도가 증가하면 펌프의 송출유량은 증가하였고, 실린더 내의 압축압력인 배압이 증가하면 송출유량은 감소하였다. 또한, 연료펌프의 회전속도가 증가할수록 펌프효율이 감소되었고, 실린더 내의 배압이 증가함에 따라 펌프효율은 감소되었다.

• 한국항해항만학회지
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• 제43권1호
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• pp.64-71
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• 2019

낙동강 하구의 지형변화 메커니즘을 파악하는 것은 하구의 관리방안과 처리방법 연구에 매우 중요하다. 본 연구에서는 낙동강 하구의 지형변화에 관여하는 강우, 하천유량, 유사량과 같은 육역으로부터 영향과 조석, 조류, 파랑, 표층퇴적물 등과 같은 해역으로부터의 영향을 조사 분석하였다. 분석된 자료에 근거하여 지형변화 실험을 수행하고, 지형변화와 외력조건별 기여도를 분석하였다. 수치실험 결과 지형변화는 하굿둑 방류 영향을 직접적으로 받는 수로부를 중심으로 침식이, 간접 영향권인 간석지를 중심으로 퇴적이 우세하게 나타났다. 수로부를 따라 이동되는 퇴적물이 파랑에 의해 분급, 배분되면서 울타리선 전면부에는 퇴적이 우세하였다. 지형변화 실험결과인 퇴적 우세현상과 비교하여, 외력조건별로 침식의 기여도가 크게 나타나고 있으나 각 외력조건의 복합적인 영향은 퇴적이 우세하게 나타나고 있다. 따라서, 낙동강 하구의 지형변화는 여러 복합적인 외력인자의 결과로 판단된다. 또한, 각 외력조건별 영향은 구역별로 상이한 기여도를 보이므로 하구관리방안 수립시 이러한 결과를 고려해야 하고, 반드시 복합적인 상호작용의 결과로 이해하고 있어야 할 것으로 사료된다.

• 한국항해항만학회지
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• 제44권2호
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• pp.128-135
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• 2020

Long-term shipping contracts represent the cooperative and coexisting relationships between the shipping and steel industries. Yet, differences between the contract forms for iron ore and steel products have emerged. Specifically, the large proportion of consecutive voyage charters (CVC) is being applied in the iron ore trade, whereas the contract of affreightment (COA) is proportionally higher for shipping steel products. The literature review and in-depth interviews in this study identified through the research model, the characteristics of the shipping and market structure in both markets have significantly contributed to the preference of different long-term contracts. It has been determined that the mutual oligopoly market structure and the characteristics of shipping such as, the small number of suitable vessels in the market, the single fixed load/discharge ports, the long-distance voyages, and the potential risks for fatal accidents because of cargo liquefaction, for the iron ore trade, provide higher contribution to the preference of CVC contracts. In contrast, the consignor oligopoly market structure and the shipping characteristics, such as the greater number of suitable vessels available in the market, the variation in ports, the cargo quantity per shipment, the various load/discharge ports, and the need for experienced carriers for steel product loading in the steel product trade has shown higher preference on the COA contracts as the consignors with superiority over the shipowners, resulting in favorable contract types and conditions for the consignors.

• 한국자동차공학회논문집
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• 제17권3호
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• pp.110-116
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• 2009

Research for climate control seats is being vigorously pursued because requests for passenger's thermal comfort are increasing. Recently, thermoelectric devices have been applied to automotive seats for both cooling and heating operations. The climate control seats using thermoelectric devices can rapidly control the air temperature passing through the devices and directly affect the thermal comfort of passengers. The performance characteristics of the climate control seats were analyzed by experiments for two different types of a leather covered seat and a mesh applied seat. Experimental results show that the cooling and heating performance for the mesh applied seat by using the discharge port of the shape of nozzle was improved significantly in comparison with that for the leather covered seat. The variation of temperature between the inlet air and the outlet air of the climate control seat for the enhanced mesh applied type was by $-3.5^{\circ}C$ at cooling mode, and was by $15.0^{\circ}C$ at heating mode, after about 30 minutes, respectively. Also, it is possible to provide rapid thermal comfort to passengers sitting on the seat in the vehicle cabin by using the proposed climate control seat.

• 한국항해항만학회지
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• 제34권3호
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• pp.205-211
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• 2010

밸러스트수 처리를 위한 Plasma Gun의 전기적 특성과 오존 생성에 미치는 주요 운전변수들의 영향에 관해 실험실 규모 연구를 수행하였다. 방전개시전압보다 높은 전압이 인가되면 방전이 시작되고 오존이 생성되었으며 전압이 증가함에 따라 기체로 전달되는 에너지 및 오존 농도가 거의 선형적으로 증가하였다. 오존 생성 측면에서 최적의 에너지 효율성을 얻을 수 있는 전극간 거리가 존재하였으며 실험된 장치에서는 1.95 mm의 전극간 거리에서 최적 효율이 얻어졌다. 전기에너지 특성에 미치는 내부전극 재질의 영향은 무시할만한 수준이었으나 내부전극의 전기전도도와 열전도도 차이가 오존 생성에 큰 영향을 미치는 것으로 나타났다. 일정한 Plasma Gun 구조에서 오존 생성은 기체로 전달되는 에너지밀도에 의해 중요한 영향을 받는 것으로 나타났으며 유입되는 기체의 산소함량이 증가할수록 오존 생성이 증가하는 것으로 나타났다.

• 한국전산유체공학회지
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• 제21권1호
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• pp.50-57
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• 2016

In various industries related with construction and military machinery, a large amount of power is normally required because such machinery operations, such as digging or breaking, take place under difficult working conditions in a rough environment. Thus, a hydraulic system needs to be applied as the major power transfer system. To produce and supply hydraulic power depending on the various load conditions, a hydraulic piston pump is utilized as a typical power source for a hydraulic system. In the present study, numerical simulations were conducted using the commercial program, Ansys CFX 14.5. To lubricate the moving parts as the pump starts to operate, a small amount of oil leaks out through the clearance between the orifice in the piston-shoe and the recess at the swash-plate. Taking this into consideration, a cylindrically shaped computational domain was modeled to maintain the same equivalent leakage area. To validate the numerical method applied herein, the numerical results of the flow rate at the discharge port were compared with the experimental data, and a good agreement between them was shown. Using the verified method, the effects of the discharge pressure and the angle of the swash-plate were also evaluated under several load conditions. The results of the present study can be useful information for a hydraulic piston pump used in many different manufacturing industries.