• Journal of Biomedical Engineering Research
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• v.37 no.1
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• pp.39-45
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• 2016

A pressure measurement system was developed to verify magnitude and position of transferred pressure on the body surface during the intermittent pneumatic compression (IPC) which is one of the most well-known methods for the prevention of deep vein thrombosis (DVT). Eighty force sensing resistors (FSR) were arranged on a mannequin leg and a hardware controller sensed, digitized, and transferred pressure data every second while IPC was being applied. Finally, sensed pressure data were color coded and visualized on the 3D model with lab-developed software. The pressure data were also saved to files for further analysis. Using this measurement system, the changing pattern of pressure was measured on the mannequin leg by changing both chamber pressure and cuff tightness. As a result, net pressure transferred onto the body surface is dependent on chamber pressure and cuff tightness. Under the same chamber pressure, the tighter a cuff was worn, the wider compressed area was and the shorter compression cycle was. Also transferred pressure was proportional to both chamber pressure and cuff tightness.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.251-256
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• 2003

The detailed flow characteristics inside a compression chamber due to the orbiting motion of a scroll is studied numerically. The orbiting motion of a scroll is modelled at 7 orbiting angles. At each orbit angle, the central compression chamber is modelled. All computations are carried by using an in-house code. It is based on the SIMPLE algorithm. Computation results show that the flow structure inside the compression chamber is dependent on the orbit angle. The pressure variation inside the compression chamber also shows great dependence on the orbit angle. The pressure variation shows local maxima when the orbiting motion of a scroll directs toward the center of the compression chamber.

• Journal of Ocean Engineering and Technology
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• v.33 no.6
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• pp.535-546
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• 2019

The paper presents a closed-form analytical solution for the ultimate strength of sandwich panels with metal faces and an elastic isotropic core during combined in-plane compression and lateral pressure under clamped boundary condition. By using the principle of minimum potential energy, the stress distribution in the faces during uni-axial edge compression and constant lateral pressure was obtained. Then, the ultimate edge compression was derived on the basis that collapse occurs when yield has spread from the mid-length of the sides of the face plates to the center of the convex face plates. The results were validated by nonlinear finite element analysis. Because the solution is analytical and closed-form, it is rapid and efficient and is well-suited for use in practical structural design methods, including repetitive use in structural optimization. The solution applies for any elastic isotropic core material, but the application that stimulated this study was an elastomer-cored steel sandwich panel that had excellent energy absorbing and protective properties against fire, collisions, ballistic projectiles, and explosions.

• 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.7 no.1
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• pp.35-42
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• 1985

This paper describes an experimental study of the effect of injection timing on the combustion characteristics in four stroke cycle diesel engine with direct injection type combustion chamber. The effect of injection timing and compression ratio of engine on the combustion characteristics are investigated. Experimental results of combustion characteristics in cylinder show that the combustion pressure and the rate of pressure rise decrease in accordance with the retard of fuel injection timing. It is observed that the rate of pressure rise in cylinder is increased an increase in the compression ratio of engine. The effect of the fuel injection timing on the frequency of cylinder pressure brings about the same trend of the maximum rate of pressure rise in cylinder.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.4
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• pp.151-158
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• 2008

Gasoline Homogeneous Charge Compression Ignition (HCCI) combustion is a new combustion concept. Unlike the conventional internal combustion engine, the premixed fuel mixture with high residual gas rate is auto-ignited and burned without flame propagation. There are several operating factors which affect HCCI combustion such as start of combustion (SOC), residual gas fraction, engine rpm, etc. Among these factors SOC is a critical factor in the combustion because it affects exhaust gas emissions, engine power, fuel economy and combustion characteristics. Therefore SOC of gasoline HCCI should be controlled precisely, and SOC detection should be preceded SOC control. This paper presents a control oriented SOC detection method using 50 percent normalized difference pressure. Normalized difference pressure is defined as the normalized value of difference pressure and difference pressure is difference between the in-cylinder firing pressure and the motoring pressure. These methods were verified through the HCCI combustion experiments. The SOC detection method using difference pressure provides a fast and precise SOC detection.

• The Journal of the Acoustical Society of Korea
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• v.31 no.5
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• pp.273-279
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• 2012

In this thesis, a nonlinear compression fitting method was studied for each frequency channel of a 64 channel digital hearing aid. Unlike conventional fitting formula method done from the result of the hearing loss test, the present fitting method uses the auditory threshold of sound pressure measured near the tympanic membrane while ITE (In-The-Ear) hearing aid is fitted into the user's ear canal. Also, the spectral distribution of the voice sound pressure was used for realizing of output sound pressure compression curves against input sound pressure level. Theoretical research results of FFT-iFFT compression algorithm has been evaluated by experimental gain measurements at each different input sound pressure level 50 dB, 70 dB, 90 dB respectively.

• The Research Journal of the Costume Culture
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• v.20 no.4
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• pp.549-559
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• 2012

The purpose of this study was to analyze the comfort of sports bras by style and bra cup size. The comfort of wear was measured with compression level. The displacement of breast points (BP) after wearing a sports bra was measured. Study subjects evaluated the comfort level of the compression type and encapsulation type sports bras after walking and running. The results showed that all types of experimental sports bras provided more coverage than everyday bras. The compression type bra placed more pressure on the breast, chest, and under-bust than the encapsulation type bra. The BP distance decreased for all types. The C cup subjects' breasts were raised after wearing the sports bras. The B cup subjects had less comfort with the compression style bra than C cup subjects. The racer back style bra with high neckline and small band girth placed more pressure than others. They were difficult to don and doff and the least comfortable. These results imply that the racer back compression style sports bra was uncomfortable for women with large breast, while the encapsulation style bra with the compressing panel at upper chest was the most comfortable. The bras that shortened BP distance placed more pressure on the breast. But the bra that raised and shorted the distance of BP provided better comfort for large-breasted subjects.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2355-2363
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• 2002

The accompanying paper, Part 1, has presented the physical modeling and basic numerical analysis results of both the flow-induced and thermally-induced residual stress and birefringence in injection molded center gated disks. The present paper, Part II, has attempted to investigate the effects of various processing conditions of injection/compression molding process on the residual stress and birefringence. The birefringence is significantly affected by injection melt temperature, packing pressure and packing time. Birefringence in the shell layer increases as melt temperature gets lower. The inner peak of birefringence increases with packing time and packing pressure. On the other hand, packing pressure, packing time and mold wall temperature affect the thermally-induced residual stress rather significantly in the shell layer, but insignificantly in the core region. Injection/compression molding has been found to reduce the birefringence in comparison with the conventional injection molding process. In particular, mold closing velocity and initial opening thickness in the compression stage of injection/compression molding process have significant effect on the flow-induced birefringence, but not on tile thermal residual stress and the thermally induced birefringence.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.1
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• pp.89-98
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• 1997

Compression waves propagating in a high speed railway tunnel impose large pressure fluctuations on the train body or tunnel structures. The pressure fluctuations can cause ear discomfort for the passengers and increase the aerodynamic resistance of trains. As a fundamental research to resolve the pressure wave phenomenon in the tunnel, a steady theory of Chester-Chisnell- Whitham was applied to a simple shock tube with a sudden cross-sectional area reduction to model trains inside the tunnel. The results of the present theoretical analysis were compared with the experiments of the shock tube. The results show that the reflected compression wave from the model becomes stronger as the strength of incident compression wave and the blockage ratio increase. However, the compression wave passing through the model is not strongly dependent on the blockage ratio. The theoretical results are in good agreement with the experiments.