• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.12
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• pp.1668-1677
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• 2013

This paper deals with the power loss and thermal characteristics of induction motor for machine tools according to the rated power and speed. To reduce the fabrication error by thermal strain in rotational machine tools, we calculated the power loss and thermal behavior of induction motors. Firstly, the inverse design of general induction motors for machine tool spindle has been performed. The inverse design results are compared with the torque-speed characteristic curve in motor's catalog. The power loss are calculated by finite element method(FEM) at rated condition. Secondary, the transient thermal characteristics of induction motors are calculated by equivalent thermal resistance model from Motor-CAD S/W. The inverse design, power loss and thermal behavior calculation for induction motors with various rated power and speed has been performed. Finally, to verify the design and calculation process of induction motor, we implemented the experimental set with 0.4kW 1710rpm class industrial induction motor model. The obtained thermal characteristics of experimental model confirmed that the design and power loss calculation processes are appropriate to the prediction of thermal strain in rotational machine tools.

• Proceedings of the Korean Magnestics Society Conference
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• 1997.05a
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• pp.100-101
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• 1997

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.10
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• pp.511-520
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• 2006

Recently, more attention has been paid to the development of high-speed permanent magnet (PM) synchronous motors, since they are conductive to high efficiency, high power density, small size, and low weight. In high-speed PM machines, core loss and windage loss form a larger proportion of the total losses than usual in conventional mid- or low speed machines. This article deals with the analysis on the core loss and windage loss in PM synchronous motor for high-speed application. Using the data information from a manufacturer and non-linear curve fitting, this paper investigates the magnetic behavior and its core losses in the stator core using the electrical steels. And, the windage loss is calculated according to the variation of the rotational speed, motor inner pressure and temperature.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.55-57
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• 2009

This paper deals with an improved core loss calculation under the load conditions, namely, no-load, AC-load and DC-load of multi-pole PM generator from curve fitting method using modified Steinmetz equation considered anomalous loss. For an accurate calculation, magnetic field analyses in stator core considering the time harmonics are performed. And using the nonlinear finite element analysis (FEA), we applied separated rotating and alternating magnetic field to core loss calculation. In order to verify the core loss results by proposed method, the experimental system for no-load core loss measurement has been implemented with DC motor, power analyzer and manufactured PM generator. And, the analysis results with rotational speed agree extremely well with those obtained by measurement.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.69-72
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• 2004

The performance of the centrifugal fan in a vacuum cleaner is affected by the hydraulic loss, such as the friction loss, the recirculation loss and the impact loss etc., Those losses depend on the rotational speed of the impeller, the inlet and exit widths, the relative flow angles to the blade, the number of the blades and the geometry of the shroud and the diffuser. These parameters are complicatedly interrelated, so the experimental means in analyzing the fans are rather limited. In the present study, the flow analysis are done numerically by changing the relevant fan parameters. A commercial code, STAR-CD, is used for the calculations. It is seen from the analyses that the computational results agree well with the experimental results. The results obtained can be used for the basic design of a centrifugal fan.

• Proceedings of the Korean Magnestics Society Conference
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• 1996.05a
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• pp.80-81
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• 1996

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.365-366
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• 2002

The sliding wear behavior of ultra high molecular weight polyethylene (UHMWPE) was examined on a novel low temperature degradation-free zirconia/alumina composite material and conventional alumina and zirconia ceramics used for femoral head in total hip joint replacement. The wear of UHMWPE pins against these ceramic disks was evaluated by performing linear reciprocal sliding and repeat pass rotational sliding tests for one million cycles in bovine serum. The weight loss of polyethylene against the novel low temperature degradation-free zirconia/alumina composite disks was much less than those against conventional ceramics for all tests. The mean weight loss of the polyethylene pins was more io the linear reciprocal sliding test than in the repeal pass rotational sliding lest for all kinds of disk materials. Neither the coherent transfer film nor the surface damage was observed on the surface of the novel zirconia/alumina composite disks during the test. The observed r,'stilts indicated that the wear of the polyethylene was closely related to contacting materials and kinematic motions. In conclusion, the novel zirconia/alumina composite leads the least wear of polyethylene among the tested ceramics and demonstrates the potential as lhe alternative materials for femoral head in total hip joint replacement.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.13-16
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• 2000

In this study, we have fabricated nonequilibrium $Fe_{85.6}Zr_{3.3}B_{5.7}Ag_{5.4}$ thin film, which contains an additional insoluble element Ag, by using DC magnetron sputtering method. We have investigated the magnetic properties of amorphous $Fe_{85.6}Zr_{3.3}B_{5.7}Ag_{5.4}$ thin film as a function of rotational field annealing(RFA). After deposition, the amorphous $Fe_{85.6}Zr_{3.3}B_{5.7}Ag_{5.4}$ thin film annealed by rotational field annealing method at $350^{\circ}C$ for an hour was founded to have high permeability of 8680 of 100 MHz, 0.2 mOe, low coercivity of 0.86 De and very low core loss of 1.3 W/cc at 1 MHz, 0.1T.

• Physical Therapy Korea
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• v.25 no.1
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• pp.47-52
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• 2018

Background: A limited hip rotational range of motion (ROM) has been considered to be one of characteristics of low back pain (LBP) in athletes. Although LBP frequently occurs in jiu-jitsu athletes, no previous has compared hip rotational ROM between jiu-jitsu athletes with and without LBP. Objects: The aim of the study was to compare ROM for hip internal rotation (IR) and external rotation (ER), and total hip rotation between jiu-jitsu athletes with and without LBP. Methods: Jiu-jitsu athletes were recruited for the LBP group ($n_1=15$) and control group without LBP ($n_2=15$). IR, ER, and total rotational range of hip joint were measured using a goniometer. Analysis of variance was used to compare the ROM between groups and sides. Results: The LBP group showed a significantly lower range of passive hip IR, passive total rotation, active IR, active ER, and active total rotation than the control group (p<.05). Dominant side of passive hip IR and active IR had a significantly lower ROM than non-dominant side (p<.05). In passive ER ROM, non-dominant side was significantly greater than dominant side (p<.05). Conclusion: Compared to jiu-jitsu athletes without LBP, athletes with LBP exhibit a loss of hip rotational ROM. Based on these results, clinicians and athletic trainers should measure hip rotational ROM when designing the management plan for jiu-jitsu athletes with LBP.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.3
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• pp.22-33
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• 1993

A theoretical analysis of predicting the detailed motion of a piston-crank mechanism within piston-guide clearance is presented, and the analysis is applied to the piston motion in a gasoline engine. A piston movement program is developed to calculate the piston attitude relative to the bore, the piston to bore impact velocity and kinetic energy loss and the net transverse force acting on the piston. This paper presents the formulation of a set of differential equations governing the transverse and rotational motion of a piston. These equations of motion were solved by well established Runge-Kutta method. As a result of this study, it is possible to predict the effects of piston geometry and piston pin offset on a piston motion and kinetic energy loss.