• Journal of Bio-Environment Control
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• v.15 no.4
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• pp.289-295
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• 2006

A computational fluid dynamics (CFD) numerical model has been developed to effectively study the ventilation efficiency of multi-span greenhouses with internal crops. As the first step of the study, the internal plants of the CFD model had to be designed as a porous media because of the complexity of its physical shapes. In this paper, the results of the wind tunnel tests were introduced to find the aerodynamic resistance of the plant canopy. The Seogun tomato was used for this study which made significant effects on thermal and mass exchanges with the adjacent air as well as internal airflow resistance. With the main factors of wind speed, static pressure, and density of plant canopy, the aerodynamic resistance factor was statically found. It was finally found to be 0.26 which will be used later as an input data of the CFD model. Moreover, the experimental procedure of how to find the aerodynamic resistance of various plants using, wind tunnel was established through this study.

• Journal of the Korean Geotechnical Society
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• v.39 no.12
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• pp.115-125
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• 2023

In this study, we evaluated the behavior of frozen soil using an electrical resistivity survey method-a nondestructive technique-and examined its characteristics through field experiments. Frozen soil was artificially prepared by injecting fluid to accelerate the freezing process, and naturally frozen soil was selected in a nearby area for comparison. A dynamic cone penetration test (DCPT) was performed to compare the reliability of the electrical resistivity survey, and time-domain reflectometry surveys were performed to assess the moisture content of the ground. Field experiments were conducted in February-when the atmosphere temperature was below freezing-and May-when the temperature was above freezing. This temperature-compensated method was used to determine reliability because the behavior of frozen soil depends on the underlying temperature. In the resistivity survey method, a section of high electrical resistivity was observed under freezing conditions due to the frozen water and converted into porosity. The converted porosity was compared with the porosity inferred from the DCPT, and the results showed that the measured electrical resistivity was valid.

• Journal of Power System Engineering
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• v.13 no.2
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• pp.36-41
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• 2009

An experimental investigation was conducted to examine the fluid flow resistance in the rectangular channel with two inclined wire screen baffles. Two different types of wire screens; dutch weave and plain weave, were used as baffle devices in this experiment. Three kinds of baffles with different mesh specifications were made up of dutch type and four different kinds of baffles were made up of plain weave type. The stainless steel wire screen baffles were mounted on the bottom wall with varied angle inclination. Reynolds numbers were varied from 23,000 to 57,000. Results show that the mesh number of baffles plays an important role on friction factor behaviour. It is found that the baffle with the most number of meshes (type SA) has the highest fluid flow resistance.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.2
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• pp.151-157
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• 2012

The present study explored the possibilities of the applications of open source libraries to shipbuilding and marine engineering industries. A computational fluid dynamics (CFD) code, termed SNUFOAM, was developed and tested for turbulent flow around a ship, free surface flow around a hull, cavitating flow, and vortex shedding dynamics around a cylinder. The results using the developed CFD codes were compared against existing experimental data and solution of commercial CFD codes. SNUFOAM showed the nearly same results as commercial CFD codes and proved to be an alternative to commercial CFD codes for shipbuilding and marine engineering industries.

• Journal of Industrial Technology
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• v.22 no.A
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• pp.37-42
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• 2002

The shearing process for the sheet metal is normally used in the precision elements such as a frame of TFT-LCD or lead frame of IC chips. In these precision elements, the burr formation prevents the system assembly and needs the additional burr removing process. In this study, we have developed the novel ultrasonic deburring system to remove the small burr came from shearing of the sheet metal effectively. The deburring tool is driven by the stepping motor and alumina and SiC particles are used as abrasives. Ultrasonic power and the flowing resistance of the abrasives make ti possible to abrasive the burr.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.572-578
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• 2001

This study is to research the heat transfer characteristics in copper-water heat pipes with screen wick, #100. Recently, the semiconductor capacity of an electronic unit has been larger, on the contrary, its size is smaller than before. As a result, a high-performance cooling system is needed. Experimental variables are inclination angle and temperature of cooling water. The distilled water was used for the working fluid. At a inclination angle ${-6}^{\circ}$, #100 2layer screen mesh is shown the best heat transfer performance.

• Bulletin of the Society of Naval Architects of Korea
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• v.30 no.4
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• pp.14-17
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• 1993

본 연구는 CSDP-초기설계 시스템 개발'3' 세부과제로 수행되었으며 선박의 기본 성능 및 사양을 결정하는데 필요한 제반 기본 계산을 수행하고 설계자의 의사결정을 지원하는 대화식 초기 설계 전산 시스템의 개발에 그 목적이 있으며, 크게 개념설계 분야와 선형 설계분야로 나누어 개발 되어왔다.(Fig. 4.1 참조). 이번 4차년도에는, 프로그램을 보다 효율적으로 사용할 수 잇도록 하기 위하여 개년설계 시스템을 구성하는 단위 모듈들을 단독으로 사용 가능하도록 독립성을 유지 함과 동시에, 시스템 차원의 상위 레벨에서 각각의 모듈들을 통합 제어하는 수퍼어플리케이션 개념을 이용한 유연화된 대화형 개념설계 프로그램(BASCON-3)을 개발하였다. 그리고 선박의 주기관 선정과 관련한 경험적 지식을 도출하여 지식베이스를 구성하고, 주기관 데이터베이스 및 저항.추진성능 추정 모듈들과의 통합을 통한 시험형의 주기관 선정 지원 시스템(ME-ASSIST )을 개발하였다. 또한 그래픽 사용자 인터페이스(GUI)를 채택한 확장형 선형 정의 및 변환 프 로그램(MBASTRANS)을 개발하였다. 형상 모델러인 ACIS를 도입하여, 조선 분야에의 활용 가 능성을 연구하였고, 조선소에 GUI개발 기술과 시스템 통합 기술을 이전하였다.

• Journal of Power System Engineering
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• v.20 no.1
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• pp.24-29
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• 2016

Remotely operated vehicles or autonomous underwater vehicles have been used for exploiting seabed natural resources. In this study, the autonomous underwater vehicle of hovering type(HAUV) is developed to observe underwater objects in close distance. A dynamic model with six degrees of freedom is established, capturing the motion characteristics of the HAUV. The equations of motion are generated for the dynamic control simulation of the HAUV. The added mass, drag and lift forces are included in the computer model. Computational fluid dynamics simulation is carried out using this computer model. The drag coefficients are produced from the CFD.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2007.12a
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• pp.138-140
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• 2007

폰툰형 레저보트는 쌍동식 또는 삼동선식의 안전성이 확보된 선체와, 다양한 기능을 만족할 수 있는 상부구조로 구성, 건조비 뿐만 아니라 레저 접근성이 용이한 보트로서, 해양레저 선진국에서는 내수면뿐만 아니라 해수면에서도 함께 즐길 수 있는 가족형 레저보트로 인식되어 최근 보급이 확대되고 있는 추세이다. 그러나 폰툰형 레저보트는 최적의 공간활용을 위해 사각모양의 갑판형태로 인해 유체의 저항에 취약한 단점이 있다. 이로 인해 선저형상, 추진시스템 및 조향운전장치 뿐만아니라 선수선저부의 슬래밍 충격에 대비한 구조강도 등 체계적인 연구를 통한 개발이 필요하다. 이에 본 연구에서는 2가구 4인 가족단위로 함께 즐길 수 있는 안전성이 높고, 낚시, 스쿠버 둥을 위한 편의시설이 확보한 선형 최적형상 연구 및 구조강조 해석을 통한 9인승 규모의 폰툰형 레저보트를 개발하고자 한다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.15 no.2
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• pp.61-66
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• 1979

Skipjack, Katsuowonus vagans, yellow tail Seriola quinqueradiata and Scomberomorus sinensis are largely caught by trolling gear in the coastal waters of Jeju Island. The author determined the hydrodynamic resistance of the trolling gears uscd in the waters, estimated the pulling force of the fish species above mentioned by use of body weight, and then calculated the minimum diameter of the lines of trolling gears. The results obtained are as follows: 1. The hydrodynamic resistance of the trolling gears present linear relationship in accordance with the towing speed of the gears. 2. The diameter of seizing leader, leader gut and branch line used in the waters might be durable to catch skipjack and yellow tail, whereas the diameter of those must be weak in intensity for Scomberomorus zinensis.