• Journal of Industrial Technology
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• v.36
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• pp.17-22
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• 2016

A circular pin fin (CPF) and a half circular pin fin (HCPF) are by using the one-dimensional analytic method. For these two fins, 90% of the maximum heat loss, Corresponding fin length for 90% of the maximum heat loss, fin effectiveness and fin efficiency are compared as functions of convection characteristic number and fin radius. Also, the ratio of heat loss from the HCPF to that from CPF listed with variation of fin length when the fin volumes are the same. One of the results shows that the efficiency of a CPF is larger than that of a HCPF while the effectiveness of a CPF is smaller than that of a HCPF when convection characteristic number, fin length and fin radius are the same.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.816-818
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• 2001

This paper shows the characteristic analysis for an inverter fed induction motor by the 2-D F.E.A. in variation of the air gap length. Harmonic effects of the induction rioter with different air gap length driven by the 6 step voltage of inverter ate investigated. And the results of the characteristic analysis on the inverter fed induction motor are compared with those of sinusoidal voltage fed motor.

• International Journal of Control, Automation, and Systems
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• v.4 no.4
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• pp.486-494
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• 2006

In this paper, we present the complete isotropy analysis of a caster wheeled omnidirectional mobile robot (COMR) with nonredundant/redundant actuation. It is desirable for robust motion control to keep a COMR close to the isotropy but away from the singularity as much as possible. First, with the characteristic length introduced, the kinematic model of a COMR is obtained based on the orthogonal decomposition of the wheel velocities. Second, a general form of the isotropy conditions of a COMR is given in terms of physically meaningful vector quantities which specify the wheel configuration. Third, for all possible nonredundant and redundant actuation sets, the algebraic expressions of the isotropy conditions are derived so as to identify the isotropic configurations of a COMR. Fourth, the number of the isotropic configurations, the isotropic characteristic length, and the optimal initial configuration are discussed.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1306-1308
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• 2005

The characteristic of line start permanent magnet(LSPM) motor with overhang structure is analyzed using 3dimensional finite element method(3D FEM). We propose the appropriate overhang length by considering the magnetic flux distribution according to changing overhang length and manufacturing process. 3D FEM analysis is inevitable because the increase of the total flux cannot be appropriately considered in 2D FEM. In equal model specification total flux is recalculated at 3D FEM, because of considering lamination length. This paper compares the characteristic of Back-emf with and without overhang by permanent magnet that has identical volume.

• Journal of the Institute of Convergence Signal Processing
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• v.7 no.4
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• pp.214-220
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• 2006

This paper presents the systematic isotropy analysis of a fully actuated caster wheeled omnidirectional mobile robot (COMR) with the steering link offset different from the wheel radius, which can be considered as the generalization of the previous analysis. First with the characteristic length introduced, the kinematic model of a COMR is obtained based on the orthogonal decomposition of the wheel velocities. Second, the necessary and sufficient conditions for the isotropy of a COMR are derived and examined to categorize there different groups, each of which can be dealt with in a similar way. Third, for each group, the isotropy conditions are further explored so as to identify four different sets of all possible isotropic configurations. Fourth, for each set the expressions of the isotropic characteristic length required for the isotropy of a COMR are elaborated.

• International Journal of Fluid Machinery and Systems
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• v.1 no.1
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• pp.38-46
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• 2008

Studies on cavitation instabilities of hydrofoils and cascades are reviewed to obtain fundamental understandings of the instabilities observed in turbopump inducers. Most of them are based on the stability analysis of two-dimensional inviscid cavitating flow. The most important finding of the analysis is that the cavitation instabilities depend only on the mean cavity length. For a hydrofoil, the characteristic length is the chord length and partial/transitional cavity oscillation occurs with shorter/longer cavity than 75% of the chord length. For cascades, the characteristic length is the blade spacing and various modes of instabilities are predicted when the mean cavity is longer than 65% of the spacing. In the last part, rotating choke is shown to occur when the cavity becomes longer than the spacing.

• Journal of the Ergonomics Society of Korea
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• v.18 no.1
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• pp.91-108
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• 1999

In our previous work using a motion analyzer and 3-dimensional sonic digitizer, the arm shapes for 23 women in their early twenties were classified into three characteristic types. In order to design sleeves, suitable for arm movements for the three characteristic arm shapes, a relationship between arm length variation and shoulder/elbow angles has been investigated for four cases of arm movements (flexion, extension, adduction and abduction). Each arm movement can be characterized by the changes in shoulder angle and the changes in elbow angle at the maximal shoulder angle. In all the four cases of arm movements, the changes of shoulder length and cap height are largest at the maximal shoulder angle. These changes were little affected by changes in elbow angle. The changes in the lower arm length and the difference between cap height and upper arm length are the largest at the maximal elbow angle of the maximal shoulder angle. There is a linear relationship between cap height and shoulder angle during arm movements; thus, in designing sleeves the cap height can be determined from the regression of cap height vs. shoulder angle.

• Water for future
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• v.20 no.1
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• pp.55-61
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• 1987

This Study is to estimate depth-length ratios by the frequency analysis of simultaneous rainfall data on fixed points in the Han -River basin. The depth-length ratios are based on examination of spatial and temporal correlation structures of the Han-River basin's rainfall. This Study reveals that the depth-length ratios are decreasing as the distance of the basin increases and that they are increasing as the duration of rainfall increases. This study also shows that the ratios tend to decrease as the return period increase. The results present general equations and characteristic equations of depth-length ratios, figures and characteristic parameter tables which explain the temporal and spatial structures of rainfall in the Han-River basin.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.3
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• pp.229-235
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• 2010

Optimum values of fin performance and dimensions for an annular fin with a rectangular profile and a pipe with variable inner radius are determined by using a variable separation method. The range of ambient convection characteristic number that results in optimum heat loss is listed. The optimum heat loss, corresponding optimum fin effectiveness, fin length, and fin height are presented as a function of the inner radius of the pipe, inner fluid convection characteristic number, fin volume, and ambient convection characteristic number. One of the results shows that the optimum heat loss, fin effectiveness and fin length increase linearly with the inner radius of the pipe when both the fin volume and fin-base radius are fixed.

• Journal of the Korean Society of Propulsion Engineers
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• v.1 no.1
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• pp.111-121
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• 1997

An investigation was performed to study the predicting the joint strength of mechanical fasteners. Bearing failure is most important failure mode for designing joint. So in this study, the prediction method in consideration with bearing failure was chosen. In the proposed method, the characteristic length is combined with the Yamada-Sun failure criterion, Tsai-Hill failure criterion and characteristic length for Tension and Compression is determined from investigation. Especially the length of compression is determined from the "bearing failure test" that newly conceived to take bearing failure into consideration. The proposed prediction method was applied to quasi-isotropic carbon/epoxy joint showing net-tension and bearing failure experimentally. Good agreement was found between the predicted and experimental result for each joint geometry. geometry.