• Korean Journal of Applied Biomechanics
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• v.21 no.3
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• pp.269-279
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• 2011

This study was analyzed the characteristics on the stability of posture while conducting a through two and half rotation technic of pench$\acute{e}$ in rhythmic gymnastics. Two rhythmical gymnastics player(LKH and SSJ) who is a member of the national team were selected, and for obtain the kinematic and kinetic variables were used a ProReflex MCU 240 infrared camera(Qualisys, Sweden) and a Type9286A force platform(Kistler, Switzerland). The mechanical factors were computed by using Visual3D program and Matlab R2009a. During the landing and rotation phase the results showed following characteristics; 1) In medial-lateral and horizontal displacement of the support foot, LKH showed smaller movement than SSJ, but SSJ showed smaller movement than LKH in swing foot. LKH showed bigger movement in medial-lateral axis of COP and vertical axis of COG, but SSJ showed bigger movement in horizontal axis of COP and medial-lateral axis of COG. 2) SSJ showed bigger maximum horizontal and vertical velocity at P1 and P2 than LKH. 3) In the inclination angle of COP and COG, SSJ showed smaller change than LKH, but within medial-lateral tilt of the shoulder, LKH performed rotation motion in horizontal position than SSJ. There was no differences in each force components during rotation, but on landing phase, the results showed a characteristic that SSJ exerted bigger breaking force and vertical force than LKH.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4B
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• pp.413-420
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• 2006

The construction of a submerged breakwater has become increasing due to their multiple effects on the coastal zone. Recently, marker rocks have been installed on the submerged breakwater to indicate its position to the vessels instead of buoy systems, since a buoy is not only improper for the ocean view, but also its mooring system may be damaged by the impulsive wave force caused by wave breaking on the breakwater. The accurate estimation of wave forces on such rocks is deemed necessary for their stability design. In this study, the characteristics of irregular wave forces acting on a marker rock, which was installed on a submerged breakwater, was investigated on the basis of laboratory experiments. It was revealed that the dimensionless highest one-third wave force tends to decrease with increasing the installation distance of a marker rock from the leading crown edge of a submerged breakwater. Also, the drag and inertia coefficients for irregular wave forces, which were obtained using the Morison equation, were investigated in relation to K.C. number.

• The Research Journal of the Costume Culture
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• v.21 no.6
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• pp.967-973
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• 2013

During high speed sewing, the needle thread is exposed to dynamic loading, short strike loading, inertia forces, friction, rubbing, force of check spring, bending, pressure, friction, impact, shock and thermal influence. The dynamic thread loading/tension alters throughout the stitch formation cycle and along its passage through the machine. The greatest tensile force occurs at the moment of stitch stretching, when the take up lever pulls for required thread length through the tension regulator. These stresses act on the thread repeatedly and the thread passes 50-80 times through the fabric, the needle eye and the bobbin case mechanism, before getting incorporated into the seam, which result in upto 40% loss in tensile strength of the sewing thread. This damage in the sewing thread adversely affects its processing and functional performance. In this paper, the contribution of dynamic loading, passage through needle and fabric, and bobbin thread interaction in the loss in tensile properties has been studied. It is observed that the loss in tensile properties occurs mainly due to the bobbin thread interaction. Dynamic loading due to the action of take up lever also causes substantial loss in tenacity and breaking elongation of cotton threads.

• Journal of Fashion Business
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• v.11 no.5
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• pp.51-63
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• 2007

Chitosan, a natural cationic macromolecular material, has been known for its moisturizing and healing effect due to the coating action based on strong ionic bonding when the chitosan is treated on hair strands. In this study, the acidic aqueous chitosan solution was prepared to treat healthy hair, and damaged hair due to bleaching, relatively thin hair and thick hair specimens. The chitosan treatment effect was reviewed by comparing spectrophotometric and mechanical characteristics of the chitosan treated and untreated specimens. Electrostatic voltage was somewhat reduced after the chitosan treatment. Smoothly coated surface was observed, in the SEM images, especially for damaged hair specimens. The values of breaking strength, which is one of the indicators of the internal characteristics of hair, was high in the case of chitosan treated samples. The values of elongation was also high in the case of chitosan treated samples, which proves the chitosan treatment effect. The friction force, one of the indicators of surface characteristics, was reduced for the case of chitosan treated samples.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.160.2-160.2
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• 2014

Recently silicon has attracted intense interest as a promising anode material of lithium-ion batteries due to its extremely high capacity of 4200 mA/g (for Li4.2Si) that is much higher than 372 mAh/g (for LiC6) of graphite. However, it seriously suffers from large volume change (even up to 300%) of the electrode upon lithiation, leading to its pulverization or mechanical failure during lithiation/delithiation processes and the rapid capacity fading. To overcome this problem, Si nanowires have been considered. Use of such Si nanowires provides their facile relaxation during lithiation/delithiation without mechanical breaking. To design better Si electrodes, a study to unveil atomic-scale mechanisms involving the volume expansion and the phase transformation upon lithiation is critical. In order to investigate the lithiation mechanism in Si nanowires, we have developed a reactive force field (ReaxFF) for Si-Li systems based on density functional theory calculations. The ReaxFF method provides a highly transferable simulation method for atomistic scale simulation on chemical reactions at the nanosecond and nanometer scale. Molecular dynamics (MD) simulations with the ReaxFF reproduces well experimental anisotropic volume expansion of Si nanowires during lithiation and diffusion behaviors of lithium atoms, indicating that it would be definitely helpful to investigate lithiation mechanism of Si electrodes and then design new Si electrodes.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.325-325
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• 2011

Very initial stage of oxidation process of Si (001) surface at room temperature (300 K) and high temperature (1200 K) was investigated using large scale molecular dynamics simulation. Reactive force field potential [1] was used for the simulation owing to its ability to handle charge variation as well as breaking and forming of bonds associated with the oxidation reaction. The results show that oxygen molecules adsorb dissociatively or otherwise leave the silicon surface. Initial position and orientation of oxygen molecule above the surface play important role in determining final state and time needed to dissociate. At 300 K, continuous transformation of ion $Si^+$ (or suboxide Si2O) to $Si2^+$ (SiO), $Si3^+$ (Si2O3) and finally to $Si4^+$ (SiO2) clearly observed. High temperature silicon surface provide heat energy that enable oxygen atom to penetrate into deeper silicon surface. The heat energy also retards adsorption process. As a result, transformation of ion $Si^+$ is impeded at 1200 K.

• Bulletin of the Society of Naval Architects of Korea
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• v.20 no.1
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• pp.47-58
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• 1983

A study is made, in the framework of linear potential theory, to investigate the hydrodynamic characteristics of two-dimensional wave-energy absorbers as like the Salter's duck and an oscillating cam with Lewis-form section, which undergo uncoupled heaving and rolling motions in an incident linear gravity wave in deep water. Wave energy is supposed to be extracted by a linearly damped generator with an spring. Some well-known formulae in ship hydrodynamics such as Haskind-Newman relation and Bessho-Newman relation are utilized in forms of Kochin functions to derived expressions for efficiency, breaking effect and drift force of the absorber. Maximum ideal efficiency of 100% can be arrived at an prescribed tuning frequency. Coupling effect is also examined to assess the detrimental effect of sway on efficiency. From numerical calculations for both types of two-dimensional devices it may be concluded that a wave-energy absorber functions at the same time as a wave breaker and that the drift force acting on the device becomes smaller when it absorbs wave energy than as it oscillates freely. Finally the study is extended to an infinite array system, equivalent to a body in a canal, to show that all incident wave energy can be absorbed regardless of the absorber's size, only if the optimum space and the optimum condition of control are realized.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.3 s.96
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• pp.30-37
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• 1999

This paper represents the development of the brake system for the inline skate using bellows. The inline skate that is used at present has defects due to frequent impulse, which weakens the breaking force by damaging the parts. Therefore to solve these problems a break system for the inline skates using hydraulics is suggested. To solve the oil leakage problems, bellows is used. Also to prevent the breaks from not touching the ground when skating the bellows is placed at the heel, high as possible. To obtain fast response speed, the ratio of inner diameter of the bellows is changed so that with only a small displacement from the bellows the rubber pad attached to the bellows will touch the ground fast. The performance of the break system using bellows depends on the optimal design of the bellows. Therefore the parameters that changes the form of the bellows are tested and also the interaction between the forces are investigated. The performance of new model brake system with bellows and old model system with only a rubber pad without bellows was estimated through observation of braking posture.

• Asian-Australasian Journal of Animal Sciences
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• v.9 no.6
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• pp.723-726
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• 1996

A water loaded pressure device using water as the breaking force was developed to evaluate eggshell strength and compared with a dropping ball techniques. Further, relationships of shell thickness and weight of eggs to shell strength were also studied. Values for both of the shell strength measuring methods showed a highly significant correlation (p < 0.001) with shell thickness. The water loaded pressure method had a much higher simple correlation coefficient for shell thickness (r = + 0.786) than the dropping ball method (r = + 0.577). The shell strength measured by the water loaded pressure method appeared not to be correlated to egg weight. On the other hand, the negative sign of the standard partial regression coefficient and the partial regression coefficient of egg weight in the estimated multiple regression equation implied that for a given shell thickness a larger egg tended to have less shell strength than a smaller egg.

• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.765-769
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• 2003

The effect of surimi gel containing the useful polysaccharides(WSP and CBP) from marine bacterium Zoogloea sp. were investigated. The optimum polysaccharide concentration, pH, and salt concentration of both WSP and CBP were 0.02 %, 7.5 and 1.5 %(w/w), respectively. The properties of surimi gel containing WSP and CBP significantly (p < 0.05) lower than control. The breaking force, whiteness and deformation of surimi gel containing WSP and CBP higher than control.