• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.103-107
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• 2009

Recently, injection/compression molding process became more popular than ever to produce many transparent optical products of high precision. Especially, optical disk for read/write is the best example. But those optical disks can cause sensorial problems because of high birefringence or deformation from the residual stresses in the media. Therefore, it is necessary to study the effects of various process conditions on the final birefringence structure in injection-only and injection/compression molded disks for producing precision injection-molded products. In the present paper we have focused on the effect of injection, holding and compression processes on the optical anisotropy(i.e. birefringence) remaining in the MOD by examining the gapwise distribution of birefringence and extinction angle. The effect of holding pressure was found to form the inner two birefringence peaks. But the effect of compression pressure on the birefringence distribution was found to make the uniform distribution near the center in the gapwise direction and inversion of extinction angle far from the gate.

• Journal of the Korean Society of Clothing and Textiles
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• v.38 no.4
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• pp.440-454
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• 2014

This study examined the wearing effect of 3D compression suits on quantitative electroencephalogram (EEG) during walking and rest. Ten males in their 20s wore three types of experimental clothing, a loose-fit wear (BS), a 3D compression suit (3D CS), and a power film welded on CS (3D WCS); in addition, EEG signals were measured during resting, walking, after walking, and after sit-ups. The results showed that a higher pressure (due to 3D CS and 3D WCS) increased the 'Concentration' level and the 'Cognitive load' of brain waves during treadmill walking due to a higher cortex activity level when walking. Differentiation was shown between two compression suits and BS was enhanced during walking on a treadmill; however, the brain waves of 'Relaxation' between two compression suits were significantly different after walking, i.e., 'Relaxation' level of 3D WCS was the highest. Rigorous exercise such as sit-ups was inefficient to distinguish the effect of compression suits on EEG. Participants perceived a higher pressure due to compression suits; however, the wear comfort of two compression suits was maintained. Two compression suits were rated as supportive and helpful during walking. Various EEG parameters such as the indices of 'Relaxation', 'Concentration' and 'Cognitive load' were effective to observe the effect of 3D compression suits on wearers' brain waves during and after walking.

• Journal of the korean Society of Automotive Engineers
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• v.5 no.1
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• pp.89-93
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• 1983

This paper describes on experimental investigation into the heat dissipation of Diesel engine, placing emphasis on the variations of compression ratio and cooling water temperature. The engine used for this test was a vertical single-cylinder four-cycle type, having a direct injection. Engine performance and heat transfer rates was tested under the compression ratio 14.3 and 17.4. In this study, the results showed that output and transfer rates of engine decrease in accordance with the decrease of compression ratio. The effect of cooling water temperature and injection delay of fuel on the heat dissipation brings about the decrease of heat transfer rates from cylinder to cooling water.

• Transactions of Materials Processing
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• v.19 no.5
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• pp.296-304
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• 2010

It is still needed to study the effect of process conditions on the final properties of injection-molded parts for producing precision optical products. Especially, the optical anisotropy, i.e., birefringence, is a significant factor to affect the function of many optical components. In the present study we have focused on the effect of holding and compression processes on the birefringence remaining in the transparent disc by examining the gap-wise distribution of birefringence and extinction angle. As a result, two extra birefringence and extinction peaks near the center in thickness direction showed the effect of holding pressure, which came from the flow in packing stage. However, more uniform birefringence distribution than injection-only cases could be found in injection/compression cases. Depends on the process condition even the flow reversal could be found from the distribution of extinction angle. Finally, graphical representation of optical indicatrix was added for better understanding the final structure of injection-only and injection/compression cases.

• Speech Sciences
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• v.9 no.1
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• pp.173-184
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• 2002

The question of Korean rhythmic type is still a controversial issue (syllable-timed; stress-timed; word-timed). As a step toward solving the question, an experiment was carried out to examine compression effects in Korean. There has been a general belief that the increase of the number of following or preceding syllables causes compression of a vowel (or syllable) in many languages, and a marked anticipatory compression effect can be especially indicative of stress timing. The purpose of this research, therefore, was to obtain some evidence to determine whether or not Korean is stress-timed. The durations of the target vowel/a/ of the monosyllabic word /pap/ were measured at both word and sentence level. In general, marked anticipatory and backward compression effects on the target vowel were observed across one-, two- and three-syllable words in citation form, whereas the effects were neither marked nor consistent at sentence level. These results led us to claim that Korean is not stress-timed.

• Geomechanics and Engineering
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• v.2 no.4
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• pp.303-319
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• 2010

The effect of grain crushing on the deformation of sand in 1D compression and 1D creep at high stresses was investigated theoretically and experimentally. An approach was proposed to formulate the process of grain crushing in sand in accordance with the laws of fracture mechanics and energy conservation. With this approach, the relation between the void ratio and the amount of grains crushed in 1D compression was derived. Laboratory test data were used to verify this derived relation. In addition, it was observed that there are similarities in evolution of grain size distribution in 1D compression and 1D creep tests. This implies that the changes in microstructure in sand under 1D compression and 1D creep are comparable.

• Journal of the Ergonomics Society of Korea
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• v.31 no.2
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• pp.337-343
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• 2012

Objective: The aim of this study was to determine the effect of abdominal-compression belt in one leg standing on balance in normal adult. Background: With the effects of increased intra-abdominal pressure, the abdominal-compression belt is contributing to a static balance control. However, specific study is still insufficient. Method: Forty subjects were randomly allocated to two groups: control(n=20) and experimental group(n=20), respectively. The experimental group used an abdominal-compression belt, whereas the control group did not that. All subjects were educated using pressure biofeedback unit and ultrasound imaging for exact application by abdominal-compression belt. Main outcome measurement was used a general stability index, fourier harmony index, weight distribution index, and fall index in tetrax balance system. Results: Experimental group improved significantly on general stability, only 2 factors(eyes closed with head turned forward and eyes closed with head turned backward) among fourier harmony index, and fall index, However, weight distribution index did not revealed significant difference. Conclusion: The findings suggest that application of abdominal-compression belt could be effective on improving balance ability in one leg standing of normal adults. Application: The results of the abdominal-compression belt might help to control balance in workers.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.7
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• pp.2315-2325
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• 1996

A compression wave is attenuated or distorted as it propagates in a tube. The present study investigated the propagation characteristics of the compression waves which are generated by a train in a high-speed railway tunnel. A Total Variation Diminishing (TVD) difference scheme was applied to one-dimensional, unsteady viscous compressible flow. The numerical calculation involved the effects of wall friction, heat transfer and energy loss due to the friction heat in the boundary layer behind the propagating compression wave, and compared with the measurement results of a shock tube and a real tunnel. The present results show that attenuation of the compression wave in turbulent boundary layer is stronger than in laminar boundary layer, but nonlinear effect of the compression wave is greater in the laminar boundary layer. The energy loss due to the frictional heat had not influence on attenuation and distortion of the propagating compression waves.

• Transactions of Materials Processing
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• v.21 no.5
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• pp.285-290
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• 2012

In spite of progress in predicting ductile failure, the development of a macroscopic yield criterion to describe damage evolution in HCP (hexagonal close-packed) materials remains a challenge. HCP materials display strength differential effects (i.e., different behavior in tension versus compression) in their plastic response due to twinning. Cazacu and Stewart(2009) developed an analytical yield criterion for porous material containing randomly distributed spherical voids in an isotropic, incompressible matrix that shows tension-compression asymmetry. The goal of the calculations in this paper is to investigate the effect of the tension-compression asymmetry on necking induced by void nucleation, evolution and consolidation. In order to investigate the effect of the tension-compression asymmetry of the matrix on necking and fracture initiation, three isotropic materials A, B, and C were examined with different ratios of tension-compression asymmetry. The various types of material had BCC, FCC, and HCP crystal structures, respectively. The ratio between tension and compression in plastic flow significantly influences the fracture shape produced by damage propagation as well as affecting the localized neck.

• The Journal of Korean Academy of Sensory Integration
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• v.2 no.1
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• pp.21-32
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• 2004

Objective : Effect of treadmill exercise on hippocampal neural cell proliferation under normal conditions and alcohol intoxication conditions has been recently studied; however, this effect under sensory stimulation application has not clarified yet. In the present study, the effect of compression stimulation application on hippocampal neural cell proliferation in the dentate gyrus in normal and alcohol intoxicated rats was investigated. Methods : Experimental design: comparative investigation on number of 5-Bromo-2'-deoxyuridine(BrdU)B-positive cells in dentate gyrus 5 days after commencement. Setting: animal laboratory. Participants: male Sprague-Dawley rats of 3weeks old in age weighing $80{\pm}10gm$. Intervention: animals were randomly assigned into 4 groups; control-rest group(n=8), control-compression group(n=8), alcohol intoxication-rest group(n=8) and alcohol intoxication-compression group(n=8). Animals of the alcohol intoxicated groups were injected intraperitoneally with alcohol(2g/kg) twice per day for 3 days. All animals were injected BrdU(50mg/kg) intraperitoneally, and rats compression stimulation application groups were compressed using sphygmomanometer cuff times per day, for 5 days following alcohol administration. Measures: mean number of BrdU-positive cells in dentate gyrus was observed via immunohistochemistry. Results : Compression stimulation application significantly increased the number of BrdU-positive cells in the dentate gyrus. Also, treatment with alcohol for 3 days inhibited cell proliferation, and compression stimulation application alleviated alcohol-induced inhibition of new cell formation. Conclusion : These results suggest the possibility that compression stimulation application may help in improvement following alcohol-induced brain damaged.