• International Journal of Naval Architecture and Ocean Engineering
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• 제4권4호
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• pp.335-352
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• 2012

An underwater hull cleaning robot can be a desirable choice for the cleaning of large ships. It can make the cleaning process safe and economical. This paper presents a hydrodynamic design of an underwater cleaning robot and its evaluation for an underwater ship hull cleaning robot. The hydrodynamic design process of the robot body is described in detail. Optimal body design process with compromises among conflicting design requirements is given. Experimental results on the hydrodynamic performance of the robot are given.

• Journal of Advanced Marine Engineering and Technology
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• 제36권5호
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• pp.627-634
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• 2012

본 연구는 개발된 인플래터블 카약의 유체역학적인 성능평가를 위한 수조시험 및 그 결과에 대한 내용을 포함하고 있다. 개발된 인플래터블 카약과 해외제품에 대한 경사시험, 선회시험은 해양공학수조에서 시제품에 대한 시험이 수행되었고 저항시험은 회류수조에서 축소된 모형선을 이용한 시험이 수행되어졌다. 다음과 같은 성능평가 방법을 이용하여 개발된 카약과 해외제품에 대한 각각의 장 단점이 비교되어졌다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1990년도 추계학술대회논문집; 한양대학교, 서울; 24 Nov. 1990
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• pp.107-112
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• 1990

In the vibration analysis of structure in fluid such as ships and offshore structures, the hydrodynamic added mass considerably affects the result of analysis. Therefore correct evaluation of the hydrodynamic added mass effect is required for an accurate analysis. But the correct evaluation of the effect is not simple because the added mass varies with the mode shape of vibration as well as the configuration of the structure. The universal method employed to evaluate added mass in ship hull vibration is Lewis's method via the introduction of 3 dimensional correction factor. But this conventional method is valid only for beam-like vibration.

• 대한의용생체공학회:의공학회지
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• 제18권2호
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• pp.147-156
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• 1997

Various prosthetic heart valves have been developed and used clinically, but they have problems, such as thrombogenecity, hemoltsis, high cost and low durability. New types of trileaflet polymer heart valves have been developed in order to use them as inlet and outlet valves in a ventricular assist device. The aim of this study is to determine the hydrodynamic effectiveness of the newly designed trileaflet polymer valves and their feasibility for temporary use in the blood pumps. Trileaflet polymer valves are made of polyurethane, because of its good blood compatibility, high tonsil strength and good resistance to fatigue. An in vitro experimental investigation was perf'ormed in order to ev91ua1e hydrodynamic performance of the trileaflet polymer valves having different design and fabrication tech- niques. The St. Jude Medical valve (SJMV) and floating-type monoleaflet polymer valve (MLPV) were also tested The pressure drop across the valve, leakage volume, and the flow patterns mere investigated for valves. The result of comparative tests showed that the trileaflet polymer valves had a better hydrodynamic performance than the others. TPV which has two stable membrane shape showed the lowest back flow. The pressure hops of TPVs were lower than that of MLPV, but slightly higher than SJMV. The hydrodynamic performance of valves under the pulastile flow showed the similar results as steady flow. The velocity profiles and turbulent intensities were measured at the distal sites of valves using a hot-film anemometer. Central flow was maintained in trileaflet polymer valves, and the maximum turbulent intensities were lower in TPVs comparing to MLPV.

• Journal of Advanced Marine Engineering and Technology
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• 제37권6호
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• pp.623-630
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• 2013

본 연구는 기 개발된 인플래터블 카약(RPO-2)과 새롭게 개발된 인플래터블 카약(RD-FK-11, RD-FK-12)의 유체역학적인 성능평가를 위하여 경사시험과 선회시험은 해양공학수조에서 저항시험은 축소된 모형선을 제작하여 회류수조에서 수행되었다. 결론적으로 각각의 카약에 대한 다양한 성능시험결과 복원성 측면에서는 KONA가 유리하고, 선회력과 무게중심 측면에서는 RD-FK-12가 우수하고, 저항성능 측면에서는 RD-FK-11이 KONA와 RPO-2에 비해 우수하였다.

• 한국정밀공학회지
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• 제28권10호
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• pp.1159-1165
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• 2011

The recording density of HDD is increasing in ratio of 100% each year. Because the increasing of recording density requires the feature of high rotation, fixation and low-noise, fluid hydrodynamic bearing(FDB) has been paid attention to overcome a limitation in ball bearing. Most of researches related to improving performance of FDB have been studied in Japan which has 80% more market share of HDD spindle motor assembly. Main subject of studies are about for the design of the groove shape, manufacturing process of fluid dynamic bearing, performance evaluation and measurement. In HDD, non-repeatable runout(NRRO) is most important parameter which determines the performance of HDD spindle system because NRRO is unpredictable that cannot be compensated in head/slider servo system. In this study, performance evaluation system can measure dynamic behaviors were designed and methodology for calculating imbalance, RRO, and NRRO were proposed.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.66-68
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• 2009

Most hard disk spindles currently used are supported by oil lubricated hydrodynamic bearings. However, in the trend of increasing spindle speed and reducing size and cost, dynamic behaviors of the bearing such as RRO and NRRO are more important. A novel system evaluating dynamic behavior of hydrodynamic bearings in had disk drive was developed to analyze the effect of groove shapes and parameters.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.930-935
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• 2001

The experimental characterization of hydrodynamic bearing spindle motor is performed for the practical implementation of high-performance hard disk drive system. Firstly, the design concept of hydrodynamic bearing for the disk drive system is addressed including the herringbone grooved journal bearing, the spiral grooved thrust bearing, capillary seal design, and the viscous pumping of fluid. Secondly, the experimental evaluation is performed for the disk drive system in which the hydrodynamic bearing spindle motor is implemented and its dynamic performances are compared with conventional ball-bearing spindle motor. The key parameters include NRRO(Non Repeatable Run-Out), disk dynamics, acoustics, and resultant PES (Position Error Signal). Finally, the external gyro-exciting test results including 200k CSS(Continuous Start-Stop) on three angular attitudes(0,90, 180 degree) are presented in order to verify the practical reliability of disk drive system subject to the gyro-motion of hydrodynamic bearing spindle motor.

• 한국수자원학회논문집
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• 제33권1호
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• pp.39-50
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• 2000

일반적으로 동수역학 모형은 마찰인자(조도계수 또는 Chezy계수)와 와점성계수를 필요로 하고 수치계산에서 이들 계수의 갑은 통상 가정 또는 반복계산을 통하여 결정된다. 수치모형에서 와점성계수는 물리적인 확산뿐만 아니라 수치점성의 효과도 가지고 있어서 수치계산의 안정성에 영향을 미치므로 이들 계수의 일관된 결정방법이 필요하다. 수위 및 유량자료, 1차원 모형인 HEC-2와 NETWORK, 2차원 모형인 SMS를 이용하여 한강하류 구간에 대한 조도계수의 산정결과와 와점성 계수의 산정식이 제시되었으며 실측수위와 비교를 통해 검증되었다.

• 한국해안해양공학회지
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• 제2권3호
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• pp.152-161
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• 1990

본 논문에서는 임의형상 3-차원 해양구조물의 동적응답산정을 위한 복합요소법에 대해서 연구하였다. 유체의 동압에 의한 하중은 관성력이 중요하다고 가정하여 점성효과는 무시하였다. 해석적고유급수해를 사용하여 회절 및 방사문제를 해결하는 복합요소법의 수식화과정을 체계적으로 정리하였으며, 임의형상 3-차원 구조물의 회절 및 방사문제를 해결할 수 있는 전산프로그램을 개발하여 여러 형상의 구조물에 대해서 예제해석을 수행하였다. 타문헌의 결과와의 비교를 통하여, 복합요소법을 이용한 파랑하중 산정기법 및 본 연구에서 개발한 전산프로그램의 타당성을 입증하였다.