• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.33 no.2
• /
• pp.135-140
• /
• 2020

An experimental study was conducted using the tracking wheel test (IEC 62217) method for evaluating the performance of insulator materials, in particular ethylene propylene diene monomer (EPDM) and silicone rubber. In addition, we studied the tracking characteristics resulting from applying the same method for the shape of the insulator housing, that is, the performance of regular and alternating sheds. The evaluation parameters were leakage current, surface characteristics, SEM, EDX, hydrophobicity, and temperature distribution; likewise, we applied the commercial frequency dry (and wet) flashover voltage test. We found that the regular shed had a greater leakage current than the alternating shed and that the recovery of the hydrophobicity in terms of rest time was greater than that of the EPDM in terms of leakage current. All of the regular-shed insulators of silicone rubber had tracking traces and choking on the sheath parting line, while the alternating shed showed only choking at the interface but no tracking traces. Therefore, it can be concluded that the commercial frequency wet flashover voltage of the silicone rubber with regular shed before and after the tracking wheel test is higher than that of the alternating shed.

• Journal of the Korean Society of Safety
• /
• v.19 no.1
• /
• pp.38-43
• /
• 2004

Many analysis methods, including finite element method, have been suggested and used for assessing the integrity of cracked structures. In the paper, in order to analyze arbitrary three dimensional cracks, the finite element alternating method is extended. The crack is modeled by the symmetric Galerkin boundary element method as a distribution of displacement discontinuities, which is formulated as singularity-reduced integral equations. And the finite element method is used to calculate the stress values for the uncracked body only. Applied the proposed method to several example problems for planner cracks in finite bodies, the accuracy and efficiency of the method were demonstrated.

• Physical Therapy Korea
• /
• v.9 no.2
• /
• pp.115-131
• /
• 2002

Functional electrical stimulation (FES) training of the knee extensors is a useful way to rehabilitate the ability to stand and walk. However, training using FES has not been able to solve the problem of fatigue; clinical application of FES quickly produces muscle fatigue, due to the continuous activation of the muscles of the lower extremity. Therefore, reduction of muscle fatigue is an important factor in increasing the effectiveness of FES training in paraplegia. Intermittent high frequency alternating stimulation is a method that combines the advantages of high frequency (leading to strong muscle contractions) and alternating stimulation (reducing muscle fatigue), thereby continuously strengthening muscles. It is not known whether low frequency simultaneous stimulation results in stronger muscle contraction than high frequency alternating stimulation. This study compared the effectiveness of high frequency alternating stimulation with low frequency synchronized stimulation. Muscle power using FES on the quadriceps of 20 normal subjects were compared. Intermittent high frequency alternating stimulation did not produce more powerful muscle contraction than intermittent low frequency synchronized stimulation, because the muscle characteristics differed individually. Significant individual variation according to muscle characteristics was founded when applying FES. Accordingly, when physical therapists use FES to treat patients, they must be aware of individual variation in muscle characteristics.

• Proceedings of the IEEK Conference
• /
• 2002.07a
• /
• pp.137-140
• /
• 2002

In this paper, a new algorithm for two-dimensional (2-D) finite-difference time-domain (FDTD) method is presented. By this new method, the maximum time step size can be increased over the Courant-Friedrich-Levy (CFL) condition restraint. This new algorithm is adapted from an Alternating-Direction Implicit FDTD (ADI-FDTD) method. However, unlike the ADI-FDTD algorithm. the alternation is performed with respect to the blocks of fields rather than with respect to each respective coordinate direction. Moreover. this method can be efficiently simulated with parallel computation. and it is more efficient than the conventional FDTD method in terms of CPU time. Numerical formulations are shown and simulation results are presented to demonstrate the effectiveness and efficiency of our proposed method.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.278-283
• /
• 2004

Many analysis methods, including finite element method, have been suggested and used for assessing the integrity of cracked structures. In the paper, in order to analyze arbitrarily shaped three dimensional cracks in an infinite body, the finite element alternating method is extended. The cracks are modeled as a distribution of displacement discontinuities by the displacement discontinuity method and the symmetric Galerkin boundary element method. Applied the proposed method to several example problems for planner cracks in finite bodies, the accuracy and efficiency of the method were demonstrated.

• Journal of Institute of Convergence Technology
• /
• v.1 no.1
• /
• pp.1-4
• /
• 2011

The object of this experimental study is to investigate the effect on frost prevention and delay by the method of alternating the function of outdoor coil rows under the frost conditions ($2^{\circ}C/1^{\circ}C$). The heat pump system with the new method can make frost delay time longer and eliminate frost effectively. It is withstand over 280 minutes without a conventional defrosting method. Maximum COP in case of adopting new method is 13% higher than that in case of reverse cycle defrosting method. Also in case of moving air injection duct faster, the frost delay time is lengthened and its COP is enhanced more.

• Transactions on Electrical and Electronic Materials
• /
• v.14 no.4
• /
• pp.177-181
• /
• 2013

In this paper, silicon solar cells are analyzed regarding power conversion efficiency by changed capacitance in the depletion region. For the capacitance control in the depletion region of silicon solar cell was applied for 10, 20, 40, 80, 160 and 320 Hz frequency band character and alternating current(AC) voltage with square wave of 0.2~1.4 V. Academically, symmetry formation of positive and negative change of the p-n junction is similar to the physical effect of capacitance. According to the experiment result, because input of square wave with alternating current(AC) voltage could be observed to changed capacitance effect by indirectly method through non-linear power conversion (Voltage-Current) output. In addition, when input alternating current(AC) voltage in the silicon solar cell, changed capacitance of depletion region with the forward bias condition and reverse bias condition gave a direct effect to the charge mobility.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.5
• /
• pp.2347-2352
• /
• 2012

In this paper, a new alternating equalizer and its differential adjustment algorithm are proposed. The proposed alternating equalizer achieves equalization effectively using an algorithm performing symbol decisions based on soft/hard decision. In addition, it is possible to improve the initial blind convergence speed and steady-state error performance simultaneously by adjusting the equalizer differentially according to the relative reliability of the symbol decisions by soft/hard decision devices. The simulation results on 16/64-QAM constellations under multipath propagation channel and additive noise conditions confirmed to support usefulness of the proposed method.

• Journal of electromagnetic engineering and science
• /
• v.9 no.4
• /
• pp.211-217
• /
• 2009

A three-dimensional locally one-dimensional multiresolution time-domain(LOD-MRTD) method is introduced and unconditional stability is proved analytically. The updating formulations have fewer terms on the right-hand side than those of an alternating direction implicit MRTD(ADI-MRTD). The validation of the method is presented using the resonance frequency problem of an empty cavity. The reduction of the numerical dispersion technique is also combined with the proposed method. The numerical examples show that the combined method can improve the accuracy significantly.

• Journal of applied mathematics & informatics
• /
• v.28 no.5_6
• /
• pp.1249-1262
• /
• 2010

An approximate alternating linearization decomposition method, for minimizing the sum of two convex functions with some separable structures, is presented in this paper. It can be viewed as an extension of the method with exact solutions proposed by Kiwiel, Rosa and Ruszczynski(1999). In this paper we use inexact optimal solutions instead of the exact ones that are not easily computed to construct the linear models and get the inexact solutions of both subproblems, and also we prove that the inexact optimal solution tends to proximal point, i.e., the inexact optimal solution tends to optimal solution.