• 한국정밀공학회지
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• 제17권3호
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• pp.129-135
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• 2000

Air-dynamic bearings are increasingly used in supporting small high-speed rotating bodies. This study investigates the effects of design parameters on the axial stiffness of spiral-grooved air bearings of various curvatures. Design parameters are fundamental clearance, groove depth, and bearing number. The pressure distribution at the clearance between the stator and rotor of the bearing is obtained by solving the Reynolds equation, and the supporting load and the axial linear stiffness are calculated from the pressure distribution. It is found that a larger curvature increases the axial linear stiffness more and that there exist an optimal groove depth for the linear stiffness of the air bearing. It is also found that the linear stiffness has a linear relationship with the bearing number.

• Tribology and Lubricants
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• 제19권6호
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• pp.342-348
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• 2003

The purpose of the paper is to investigate the noise characteristics of cylindrical roller bearings. For the sake of simplicity, it is assumed that the cylindrical roller bearing is infinitely long, and there is no outside force acting on the bearing. The effects of radial clearance of the bearing, viscosity of the lubricant and number of the roller on the noise of the bearing are also examined. Results show that the fundamental frequency of the bearing noise corresponds to the multiplication of number of the roller and whirling frequency of the roller center or the retainer. The acoustical frequency spectra of the roller bearing are pure tone spectra, containing the fundamental frequency of the bearing and its super­harmonics. The low viscosity of the lubricant, high radial clearance of the bearing, and low number of the roller decrease the bearing noise. The results and discussions of the present paper could aid in the low­noise design of the cylindrical roller bearing.

• 대한약학회:학술대회논문집
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• 대한약학회 2002년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2
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• pp.411.3-412
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• 2002

On the basis of recognizing that physicochemical properties (lipophilic/hydrophilic), intestinal absorption clearance and pharmacokinetic characteristics of drug are the fundamental parameters controlling the rate and the extent of drug absorption, the biopharmaceutics classification system for the correlation between drug lipid- solubility and intestinal absorption clearance is proposed. (omitted)

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.195-199
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• 2001

The flow turning process, an incremental forming process, is a cost-effective forming method for axi-symmetric intricate parts to net shape. However, the flow turning process shows a fairly complicated deformation, it is very difficult to obtain satisfactory results. Therefore extensive experimental and analytical research has not been carried out. In this study, an fundamental experiment was conducted to improve productivity with process parameters such as tool path, angle of roller holder($\alpha$), feed rate(v ) and comer radius of forming roller(Rr). These factors were selected as variables in the experiment because they were most likely expected to have an effect on spring back. The clearance was controlled in order to achieve the precision product which is comparable to deep drawing one. And also thickness and diameter distributions of a multistage cup obtained by flow turning process were observed and compared with those of a commercial product produced by conventional deep drawing.

• Clinical and Experimental Pediatrics
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• 제52권9호
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• pp.999-1004
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• 2009

목 적 : cystatin C가 creatinine보다 연령, 성별, 근육량, 약물 등에 영향을 적게 받는 등 사구체 여과율 추정에 더 우수하다는 연구가 많이 나오면서 cystatin C를 이용하여 사구체 여과율을 추정하는 방법이 많이 나오고 있다. 그러나 이런 사구체 여과율을 추정하는 여러 방법들 간에 어느 정도 차이가 있는지에 대해 실제적인 데이터가 많지 않아 대표적으로 이용되고 있는 creatinine 청소율과 이외 다른 식에 의한 사구체 여과율 값의 관계 및 cystatin C의 유용성에 대해 확인해 보고자 하였다. 방 법 : 2005년 1월부터 2008년 3월까지 중앙대학교 용산병원 소아청소년과를 내원한 20세 미만의 환아들로서 다양한 신질환을 가지고 있는 211명을 대상으로 하였다. 사구체 여과율을 구하기 위한 여러 가지 추정 식 중 혈중 creatinine을 사용한 Schwartz 식, Counahan-Barratt 식 그리고 cystatin C를 이용한 Filler & Lepage식, Bokencamp식, Grubb 식에 의한 값을 creatinine 청소율과 비교하였다. 결 과 : 각 식에 의한 사구체 여과율과의 상관계수를 구한 결과 Schwartz식으로 구한 사구체 여과율이 Counahan식으로 구한 사구체 여과율보다 상관성이 더 높고, 또한 cystatin C를 기초로 한 세가지 식(Filler, Bokencamp, Grubb)으로 구한 사구체 여과율보다 creatinine을 기초로 한 식으로 구한 사구체 여과율 값이 상관성이 더 높은 것을 알 수 있다. 또한 진단적 정확성을 분석한 결과 Schwartz 식으로 구한 사구체 여과율이 더 진단적 가치가 있었다. 결 론 : 사구체 여과율 감소를 진단하는데 있어서도 cystatin C를 이용한 경우가 혈청 creatinine을 이용한 식보다 더 좋다고 말할 수 없다. 또한 신기능 저하가 심하지 않을 것으로 예측되는 환아들의 사구체 여과율의 추정에서 cystatin C의 유용성을 확인할 수 없었다.

• 한국정밀공학회지
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• 제9권2호
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• pp.36-43
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• 1992

In this paper, a robot assembly wrist, which is able to assemble chamferless parts, has been developed. The RCC (Remote Center Compliance) structure is used as a basic structure. 5 position sensors and 4 pneumatic actuators are installed additionally to measure the deformation of RCC structure and correct the errors actively. Due to the restricted direction of actuation, a decision rule which selects the suitable actuator according to the position sensor signals is needed. For this purpose, a neural network is used and it is experimentally shown that the nerual network overcomes system's nonlinearity. This paper presents fundamental experiment results for the insertion of parts with several clearance.

• Tribology and Lubricants
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• 제19권5호
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• pp.292-297
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• 2003

The fundamental fluid mechanics associated with the rotation of a smooth plane disk enclosed within a cylindrical chamber have been studied experimentally. In order to acquire systematic information pertinent to this problem torque and friction loss data were obtained over a wide range of disk Reynolds numbers for axial clearance-disk radius ratio H/R from 0.025 to 0.2 and radial tip gap-disk radius ratio s/R from 0.021 to 0.105. Loss analysis of hard disk drive (HDD) is presented to describe the contribution of windage loss of a rotating disk. The minimum loss form factor of HDD can be obtained from this analysis at each operation conditions.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.1016-1020
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• 2001

The spinning is a very effective manufacturing technology for short production runs in a variety of sizes and shapes, because it can form the cross-section or tubular parts various shapes. However extensive experimental and analytical research has not been carried out. In this study, and fundamental experiment was conducted to improve productivity with process parameter such as tool path, angle of roller holder(a), feed rate(v) and corner radius of forming roller(Rr). These factors were selected as variables in the experiment because they were most likely expected to have and effect on spring back. The clearance was controlled in order to achieve the precision product which is comparable to deep drawing one. And also thickness and diameter distribution of a multistage cup obtained by shear spinning process were observed and compared with those of a commercial product produced by conventional deep drawing.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제34회 추계학술대회 개최
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• pp.159-165
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• 2001

The fundamental fluid mechanics associated with the rotation of a smooth plane disk enclosed within a cylindrical chamber have been studied experimentally. In order to acquire systematic information pertinent to this problem torque and friction loss data were obtained over a wide range of disk Reynolds numbers for axial clearance-disk radius ratio H/R from 0.025 to 0.2 and radial tip gap-disk radius ratio s/R from 0.021 to 0.105. Loss analysis of hard disk drive(HDD) is presented to describe the contribution of windage loss of a rotating disk. The minimum loss from factor of HDD can be obtained from this analysis at each operation conditions.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.295-300
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• 2001

The progressive die performs a series of fundamental sheet metal working, particularly this study regards to develop the center carrier feeding type die for thick sheet metal(SS41, 2.5mm) production that is a specific division. In order to prevent defect on the production, the analysis of production part, optimum design of strip process layout, die design and die making and tryout etc. are necessary. In this study, we designed and predicted a progressive die of multi stages by wide collected data base and computer aided method.