• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.1033-1039
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• 2012

Artificial joints are used when joints lose their function because of either the destruction or damage of the composing bones of the joints. To evaluate the primary stability of a femur-implant system, the relative displacement caused by a repeated load is measured immediately after the insertion of the artificial joint. For more accurate stability evaluation, the accurate measurement of the penetration displacement of the artificial joint to the bone and the rotation angle of the artificial joint is essential. In this study, to evaluate the primary stability of the femur-implant system, we propose a new relative displacement measurement method. By using this new method, we comparatively evaluate the primary stability for various surgical methods and the varying stiffness of the cadaver femur-implant itself.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1110-1122
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• 2018

This paper proposes an alternative method to evaluate the effect of wind power to the power system stability with small disturbance. Alternatively, available techniques for stability analysis of a power system based on deterministic methods are less accurate for high penetration of wind power. Numerical simulations of random behaviors are computationally expensive. A stochastic stability index (SSI) is proposed for the power system stability evaluation based on the theory of stochastic stability and energy function, specifically the stochastic derivative of the relative well-defined energy function and the critical energy. The SSI is implemented on the modified nine-bus system including wind turbines under different conditions. A doubly-fed induction generator (DFIG) wind turbine is characterized and modeled using measured wind data from several sites in Thailand. Each of the obtained wind power data is analyzed. The wind power effect is modeled considering the aggregated effect of wind turbines. With the proposed method, the system behavior is properly predicted and the stability is quantitatively evaluated with less computational effort compared with conventional numerical simulation methods.

• Journal of the Korean Society of Physical Medicine
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• v.6 no.2
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• pp.135-143
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• 2011

Purpose: The purpose of this study was to investigate onset timing of vastus medialis oblique(VMO) relative to vastus lateralis(VL) the VMO/VL electromyographic(EMG) ratio according to heel height Methods: A repeated measures design was used. Fifteen healthy female college students with no known knee musculoskeletal dysfunction were recruited this study. They carried out a standardised stair acent activity under 4 conditions; barefoot, and with heel height of 1, 3, 7 cm. Muscle activity was measured by surface EMG (Myosystem 1400A, Noraxon Inc., U.S.A). Data were analysed using $1{\times}4$ repeated measures ANOVA. Results: Onset timing differed with heel height(p<.05). However, the VMO/VL EMG ratio was not significantly difference between conditions. Conclusion: We found that 7 cm heel height delayed in VMO onset compared with 3 cm heel height during stair ascent, but no change in the relative EMG intensity of VMO and VL as measured by th VMO/VL ratio. The findings indicate that high-heeled shoes may have disadvantages in knee stability because of delayed onset of VMO. Due to a lack of knee joint stability, wearing of high heeled shoes should be avoided.

• Bulletin of the Korean Chemical Society
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• v.30 no.4
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• pp.837-845
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• 2009

We have performed DFT calculations to investigate the conformational characteristics and hydrogen bonds of the calix[6]arene (1) and p-tert-butylcalix[6]arene (2). The structures of various conformers of 1 were optimized by using the B3LYP/6-31G(d,p) and /6-31+G(d,p) methods followed by single point calculation of MPW1PW91/ 6-31G(d,p). The relative stability of the conformers of 1 is in the following order: cone (pinched: most stable) > partial-cone > cone (winged) $\sim$ 1,2-alternate $\sim$ 1,2,3-alternate > 1,4-alternate > 1,3-alternate > 1,3,5-alternate. The structures of different conformers of 2 were optimized by using the B3LYP/6-31G(d,p) method followed by single point calculation of MPW1PW91/6-31G(d,p). The relative stability of the conformers of 2 is in the following order: cone (pinched) > 1,2-alternate > cone (winged) > 1,4-alternate $\sim$ partial-cone > 1,2,3-alternate > 1,3,5alternate > 1,3-alternate. One of the important factors affecting the relative stabilities of the various conformers of the 1 and 2 is the number and strength of the intramolecular hydrogen bonds.

• Tribology and Lubricants
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• v.16 no.5
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• pp.365-372
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• 2000

Tribological behavior of novolac resin-based friction materials with three different relative amounts of graphite and zirconium silicate was investigated by using a pad-on-disk type friction tester. The goal of this paper is to examine the effects of the relative amount of a lubricant and an abrasive in the automotive friction material on friction and wear characteristics at elevated temperature. Friction and wear of friction materials were affected by the existence of transfer film(3$\^$rd/ body layer) at friction interface and the composition of friction material, especially lubricant amount. The friction material with higher content of graphite indicated homogenized and durable transfer film, and resulted in stable friction coefficient regardless of the increase in friction heat. The experimental result also showed that the higher concentration of ZrSiO$_4$ in friction material aggravated friction stability and wear resistance due to the higher friction heat generated at fiction interface during high temperature friction test.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.265-271
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• 1999

The effects of solid lubricants on wear and friction characteristics of friction materials were studied using a pad-on-disk type friction tester. Friction materials with four different formulations containing different relative amounts of solid lubricants(graphite, MoS$_2$, and Sb$_2$S$_3$) were investigated. Results of this work showed that each formulation with different lubricants had unique friction characteristics. Friction material containing rich MoS$_2$ showed excellent friction stability at different friction conditions. However friction material containing rich Sb$_2$S$_3$revealed high wear of friction materials.

• Bulletin of the Korean Chemical Society
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• v.25 no.4
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• pp.553-556
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• 2004

In this study we have performed ab initio computer simulations to investigate the conformational characteristics of the tetraethyl (1) and triethyl ester (2) of p-tert-butylcalix[4]arene. The structures of different conformational isomers for each compound have been optimized using ab initio RHF/6-31G methods. After optimization, B3LYP/6-31+G(d,p) single point calculations of the final structures are done to include the effect of electron correlation and the basis set with diffuse function and polarization function. Relative stability of tetraethyl ester (1) of p-tert-butylcalix[4]arene is in following order: cone (most stable) > partial cone > 1,3- alternate > 1,2-alternate isomer. Relative stability of triethyl ester (2) of p-tert-butylcalix[4]arene is in following order: cone (most stable) > 2-partial cone > 1-partial cone > 3-partial cone ~ 1,3-alternate ~ 1,2- alternate isomer.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2310-2314
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• 2007

Stable molecular conformations were calculated for the p-tert-butylcalix[4]arene crown ether bridged at the lower rim with pyridyl unit (1) in the various conformers and their potassium-ion complexes. The structures of three distinct conformations have been optimized using DFT B3LYP/6-31G(d,p) method. Relative stability of free host 1 is in following order: cone (most stable) > partial-cone > 1,3-alternate conformer. For two different kinds of complexation mode, the potassium cation in the crown-ether moiety (cr) has much better complexation efficiency than in the benzene-rings (bz) pocket for all three kinds of conformation of host molecule 1. The relative stability of complex (1+K+) in the cr-binding mode is in following order: partial-cone (most stable) ~ cone > 1,3-alternate conformer.

• Proceedings of the KSPS conference
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• 2007.05a
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• pp.213-216
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• 2007

The purpose of this study is to observe how Korean learners with low (KL) and high (KH) English proficiency manifest English rhythm with respect to the relative temporal stability or temporal constraint of syllable. In this study, speech cycling task, repeating a short phrase with the series of beeps of same interval, was used to examine temporal distribution of stressed beats.

• Bulletin of the Korean Chemical Society
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• v.26 no.6
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• pp.909-912
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• 2005

Calculations are presented for the structures of various conformers of the bare proline and proline –($H_2O$) cluster. The effects of hydrogen bonding with a water molecule on the relative stability of the low energy conformers of proline are examined. Microsolvation by a water molecule is predicted to affect the relative stability, structures and the infrared frequencies of the conformers to a large degree.