• 한국해양공학회지
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• 제13권3호통권33호
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• pp.12-20
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• 1999

In this paper, method for mapping a three-dimensional shape into the two-dimensional plane will be introduced. This method is referred to geometric modelling and means a transformation between the flat sheet and final surface. The initial blank shape represents the original configuration of the final shape formed into three dimensional surface. The initial constant constant area mapping hypothesis was used in this paper. This technique will be applied to the basic data for an interactive computer design capable of dealing with typical stamping process, including deep parts and complex shapes.

• 한국전산유체공학회지
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• 제13권2호
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• pp.42-47
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• 2008

Heat transfer on two identical nearby circular cylinders immersed in the uniform cross flow at Re=120 and Pr=0.7 was numerically studied. We consider all possible types of arrangements of the two circular cylinders in terms of the distance between the two cylinders and the inclination angle with respect to the direction of the main flow. It turns out that significant changes in the characteristics of heat transfer are noticed depending on how the two circular cylinders are positioned, resulting in quantitative changes of heat transfer coefficients on both cylinders. Collecting all the numerical results obtained, we propose a contour diagram for averaged Nusselt number for each of the two cylinders. The perfect geometrical symmetry implied in the flow configuration allows one to use those diagrams to estimate heat transfer rates on two identical circular cylinders arbitrarily positioned in physical space with respect to the main flow direction.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 Proceedings of the Korea Automatic Control Conference, 11th (KACC); Pohang, Korea; 24-26 Oct. 1996
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• pp.77-82
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• 1996

This paper is concerned with how to utilize kinematic redundancy to reconstruct the inverse kinematic solution which is not attainable due to hardware limitations. By analyzing the error due to hardware limitations, we are to show that the recoverability of limitation reduces to the solvability of a reconstruction equation under the feasibility condition. It will be next shown that the reconstruction equation is solvable if the configuration is not a joint-limit singularity. The reconstruction method will be proposed based on the geometrical analysis of recoverability of hardware limitations. The method has the feature that no task motion error is induced by the hardware limitations while minimizing a possible null motion error, under the recoverability assumed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1424-1429
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• 2004

In this paper a mathematical framework for deriving acceleration bounds from given joint torque limits of multiple cooperating robots are described. Especially when the different frictional contacts for every contact are assumed and the torque limits are given in 2-norm sense, we show that the resultant geometrical configuration for the acceleration is composed of corresponding parts of ellipsoids. Since the frictional forces at the contacts are proportional to the normal squeezing forces, the key points of the work includes how to determine internal forces exerted by each robot in order not to cause slip at the contacts while the object is carried by external forces. A set of examples composed of two robot systems are shown with point-contact-with-friction model and insufficient or proper degree of freedom robots.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 V
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• pp.2717-2720
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• 2003

A mathematical framework for deriving acceleration bounds from given joint torque limits of two cooperating robots are described in this paper. Especially when the torque limits are given in 2-norm, the resultant geometrical configuration is ellipsoid(the ellipsoid is often called manipulability ellipsoid in many works). At first, the mathematical derivation starts from the dynamics of both object and robots as well as the kinematics of the robots, and is finally arranged in a form of equation relating joint torques to object acceleration through a complete constraint contact(or “very-soft contact”). To show the usefulness of the proposed method, two examples are included, and especially the case where friction effects the ellipsoid shape is also considered In the example.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.347-354
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• 2009

Plate Heat Exchnager(PHE) has recently become widely adopted for cogeneration systems owing to its small installation space and high thermal efficiency. The gap between plates can be changed depending on its assemble type, i.e. gasket or blazing. The gap is known to affect thermal efficiency and working pressure drop in PHE with complicated geometrical features. Numerical simulation techniques have been developed to deal with PHE with complex configuration of chevron plates. The present study is aiming at identifying the gap effect on pressure drop and thermal efficiency of the PHE. The numerical simulation results show that the gap has relatively large effects on working pressure drop than thermal efficiency in performance of PHE.

• 전산구조공학
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• 제6권4호
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• pp.99-105
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• 1993

본 연구에서는 보울트-너트 체결기구의 체결장력 설계(Pre-Load Design)시 중요한 인자의 하나인 체결체의 강성(Stiffness)을 유한요소법을 이용하여 해석하였다. 비선형 간극요소(Non-linear Gap Element)와 최적화 기법(Optimization Technique)을 도입하여 유한요소해석 과정에서 요구되는 경계조건(Boundary Condition)의 설정과정을 일반화하였으며, 체결체간의 기밀성 상실 현상을 입증하였다. 변형량과 응력분포로부터 체결체의 강성을 해석하고, 기존의 경험식의 적용범위를 검토하였다.

• Journal of Radiation Protection and Research
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• 제6권1호
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• pp.41-44
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• 1981

A method is presented by which precise evaluation of radioactive concentrations in liquid or gaseous effluent released from large nuclear facilities is possible. Calculations have been made of the calibration constants at different energies for a commonly used liquid and gaseous effluent monitors as well. It is expected that the method could be applicable to the particular monitors with different geometrical configuration with simple modifications.

• 한국전산유체공학회지
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• 제13권3호
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• pp.14-20
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• 2008

In this investigation, flow patterns past two identical nearby spheres at Re=300 were numerically studied. We considered all possible arrangements of the two spheres in terms of the distance between the spheres and, the angle inclined with respect to the main flow direction. It turns out that significant changes in shedding characteristics are noticed depending on how the two spheres are positioned. Collecting all the numerical results obtained, we propose a diagram for flow pattern on the distance vs. angle plane. The perfect geometrical symmetry implied in the flow configuration allows one to use that diagram to identify flow patterns past two identical spheres arbitrarily positioned in physical space with respect to the main flow direction.

• 대한기계학회논문집B
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• 제31권8호
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• pp.724-732
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• 2007

Flow patterns in the presence of two identical nearby circular cylinders at Re=100 were numerically studied. We considered all possible arrangements of the two circular cylinders in terms of the distance between the two cylinders and the inclination angle with respect to the direction of the main flow. Eight distinct flow patterns were identified based on vorticity contours and streamlines, which are Base-Bleed, Biased-Base-Bleed, Shear-Layer-Reattachment, Induced-Separation, Vortex-Impingement, Flip-Flopping, Modulated Periodic, and Synchronized-Vortex-Shedding. Collecting all the numerical results, we propose a general flow pattern diagram for flows past two nearby cylinders. The perfect geometrical symmetry implied in the flow configuration allows one to use this diagram to distinguish flow patterns in the presence of two identical circular cylinders arbitrarily positioned in physical space with respect to the main flow direction.