• PNF and Movement
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• v.15 no.3
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• pp.353-360
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• 2017

Purpose: This study aimed to measure static balance of low back pain patients while one-leg standing in abdominal compression belts. Methods: The study included 40 adult males and females at J university, divided into a low back pain patient group and a normal group through the Oswestry disability questionnaire (ODQ). The subjects were instructed to hold a one-leg standing posture for 15 seconds on a balance measurement plate while wearing an abdominal compression belt. Shifting distance (0.1 cm), mean velocity (cm/s), pressure, and contact area were analyzed using BioRescue (BioRescue, RMINGEIEIRIE, Rodez, France). The average value was used to measure the result 3 times for each condition. Results: Both normal and low back pain groups significantly decreased in the speed of sway while wearing the abdominal compression belt. Furthermore, the pressure of the center of motion significantly decreased in the low back pain groups while wearing abdominal compression belt. However, there were no significant differences in the speed of sway or the pressure of center of motion between groups after wearing the abdominal pressure belt. Conclusion: These results suggest that abdominal compression belts are one option for improving balance temporarily. However, balance after wearing abdominal compression vests depends on onset of back pain, age, and symptoms of pain in the groups with low back pain. Further research is needed to investigate muscle activity, dynamic balance, and the effect of the period of wearing abdominal compression belts in the variety of low back pain patients.

• Transactions of Materials Processing
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• v.20 no.2
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• pp.99-103
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• 2011

Many parameters influence the frictional behavior of steel sheet during stamping. The contact pressure between a die and a sheet during stamping is one of them. Thus, this parameter is investigated for high strength steel (HSS) sheets, which are widely used for auto body panels due to their potential for weight reduction. Since HSS extend the limits of contact pressure for mild steel, the effect of this parameter on friction cannot be ignored. To investigate the influence of contact pressure on the frictional behavior of steel sheets, a flat type of friction test was conducted on three different steel sheets under various contact pressures. For bare steel sheets, the curve representing the relationship between contact pressure and friction coefficient exhibits a U shape. Coated steel sheets show a similar tendency except at low contact pressure. For these materials, when the contact pressure is very low, the friction coefficient slightly increases with pressure before it starts to decrease. The test results show that the effect of contact pressure on frictional behavior of steel sheet is not negligible even for contact pressures that are lower than the strength of HSS sheet.

• Wind and Structures
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• v.16 no.1
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• pp.1-23
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• 2013

The wind-induced transient response of internal pressure following the creation of a sudden dominant opening during the occurrence of high external pressure, in low-rise residential and industrial buildings was numerically investigated. The values of the ill-defined parameters namely the flow contraction coefficient, loss coefficient and the effective slug length were calibrated by matching the analytical response with the computational fluid dynamics predictions. The effect of a sudden i.e., "instantaneously created" windward opening in the Texas Technical University (TTU) test building envelope was studied for two different envelope flexibility-leakage combinations namely: (1) a quasi-statically flexible and non-porous envelope and (2) a quasi-statically flexible and porous envelope. The responses forced by creating the openings at different time leads/lags with respect to the occurrence of the peak external pressure showed that for cases where the openings are created in close temporal proximity to the peak pressure, the transient overshoot values of internal pressure could be higher than the peak values of internal pressure in the pre-sequent or subsequent resonant response. In addition, the influence of time taken for opening creation on the level of overshoot was also investigated for the TTU building for the two different envelope characteristics. Non-dimensional overshoot factors are presented for a variety of cavity volume-opening area combinations for (1) buildings with rigid/quasi-statically flexible non-porous envelope, and (2) buildings with rigid/quasi-statically flexible and porous envelope (representing most low rise residential and industrial buildings). While the factors appear slightly on the high side due to conservative assumptions made in the analysis, a careful consideration regarding the implication of the timing and magnitude of such overshoots during strong gusts, in relation to the steady state internal pressure response in cyclonic regions, is warranted.

• Restorative Dentistry and Endodontics
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• v.35 no.4
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• pp.285-294
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• 2010

The purpose of this study was to evaluate the viability of periodontal ligament cells of rat teeth after low-temperature preservation under high pressure by means of MTT assay, WST-1 assay. 12 teeth of Sprague-Dawley white female rats of 4 week-old were used for each group. Both side of the first and second maxillary molars were extracted as atraumatically as possible under tiletamine anesthesia. The experimental groups were group 1 (Immediate extraction), group 2 (Slow freezing under pressure of 3 MPa), group 3 (Slow freezing under pressure of 2 MPa), group 4 (Slow freezing under no additional pressure), group 5 (Rapid freezing in liquid nitrogen under pressure of 2 MPa), group 6 (Rapid freezing in liquid nitrogen under no additional pressure), group 7 (low-temperature preservation at $0^{\circ}C$ under pressure of 2 MPa), group 8 (low-temperature preservation at $0^{\circ}C$ under no additional pressure), group 9 (low-temperature preservation at $-5^{\circ}C$ under pressure of 90 MPa). F-medium and 10% DMSO were used as preservation medium and cryo-protectant. For cryo-preservation groups, thawing was performed in $37^{\circ}C$ water bath, then MTT assay, WST-1 assay were processed. One way ANOVA and Tukey HSD method were performed at the 95% level of confidence. The values of optical density obtained by MTT assay and WST-1 were divided by the values of eosin staining for tissue volume standardization. In both MTT and WST-1 assay, group 7 ($0^{\circ}C$/2 MPa) showed higher viability of periodontal ligament cells than other group (2-6, 8) and this was statistically significant (p < 0.05), but showed lower viability than group 1, immediate extraction group (no statistical significance). By the results of this study, low-temperature preservation at $0^{\circ}C$ under pressure of 2 MPa suggest the possibility for long term preservation of teeth.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.231-237
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• 2004

Vacuum carburizing continues to gain acceptance as an alternative to atmosphere carburizing particularly in the car industry. The advantages of low-pressure carburization over atmospheric gas carburization is not only the creation of a surface entirely free of oxide and the environmentally friendly nature of these methods but also an improvement in deformation behaviour achieved by combining carburization with gas quenching, a reduction in batch times by increasing the carburization temperature, low gas and energy consumption and the prevention of soot to a large extent. In present study, an improved vacuum carburizing method is provided which is effective to deposit carbon in the surface of materials and to reduce cycle time. Also LPC process simulator was made to optimize to process controls parameters such as pulse/pause cycles of pressure pattern, temperature, carburizing time, diffusion time. The carburizing process was simulated by a diffusion calculation program, where as the model parameters are proposed with help the experimental results and allows the control of the carburizing process with good accordance to the practical results. Thus it can be concluded that LPC process control method based on the theoretical simulation and experimental datas appears to provide a reasonable tool for prototype LPC system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.4 s.247
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• pp.373-378
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• 2006

We present the design, fabrication, and characterization of a multi-chip microelectrofluidic bench, achieving both electrical and fluidic interconnections with a simple, low-loss and low-temperature electrofluidic interconnection method. We design 4-chip microelectrofluidic bench, having three electrical pads and two fluidic I/O ports. Each device chip, having three electrical interconnections and a pair of two fluidic I/O interconnections, can be assembled to the microelectofluidic bench with electrical and fluidic interconnections. In the fluidic and electrical characterization, we measure the average pressure drop of $13.6{\sim}125.4$ Pa/mm with the nonlinearity of 3.1 % for the flow-rates of $10{\sim}100{\mu}l/min$ in the fluidic line. The pressure drop per fluidic interconnection is measured as 0.19kPa. Experimentally, there are no significant differences in pressure drops between straight channels and elbow channels. The measured average electrical resistance is $0.26{\Omega}/mm$ in the electrical line. The electrical resistance per each electrical interconnection is measured as $0.64{\Omega}$. Mechanically, the maximum pressure, where the microelectrofluidic bench endures, reaches up to $115{\pm}11kPa$.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.152-157
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• 2002

A cross-flow fan is widely used on many industrial fields: a blower for the general industry, mining industry, automobile and home appliances. The design point of the cross-flow fan is generally chosen by based on the region within low static pressure and high flow rate. It relatively makes high dynamic pressure at low speed because a working fluid passes through an impeller blade twice. However, it has low static pressure efficiency between $30\%$ and $40\%$ because of relative high impact loss. Recently, in the air-conditioning systems, the operating behaviors at the off-design points are highly regarded to broaden the application area for various air-cooling loads. Especially, at the low flow rate, there exists a rapid pressure head reduction, a noise increase and an irregular flow against a rearguider as a scroll of centrifugal fan. Numerical analyses are carried out for cross-flow fan including the impeller, the rearguider and the stabilizer. Numerical domains are discretized by hexahedral cells. Three-dimensional, unsteady governing equations are solved using FVM, SIMPLE algorithm, sliding grid system and standard k-$\epsilon$ turbulence model.

• 한국태양에너지학회:학술대회논문집
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• 2008.11a
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• pp.280-287
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• 2008

In case of low pressure steam turbine used in power plant, it was operated in wet steam and high stress condition. Therefore, it is possible that the corrosion damage of low pressure was induced by this condition. According to previous study, about 30% of total blade failure correspond to corrosion fatigue or SCC(stress corrosion cracking) in low pressure turbine. Especially, LSB(last stage bucket) of low pressure turbine has a higher hardness to prevent erosion damage due to water droplet however, generally this is more dangerous for SCC damage. Therefore, to improve reliability of turbine blade. various methods for SCC evaluation has been developed. In this study, the crack found in LSB during in-service inspection was evaluated using microstructure analysis and stress analysis. From the stress analysis, the optimum size of fillet to remove the crack was proposed. And also, the reliability was evaluated for modified LSB using GOODMAN diagram.

• Korean Journal of Materials Research
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• v.16 no.9
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• pp.538-542
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• 2006

Nano-sized cobalt oxide powders were prepared by low pressure spray pyrolysis process. The precursor powders obtained by low pressure spray pyrolysis process from the spray solution with ethylene glycol had several microns size and hollow structure. The precursor powders obtained from the spray solution with optimum concentration of ethylene glycol formed the nano-sized cobalt oxide powders with regular morphology after post-treatment without milling process. On the other hand, the cobalt oxide powders obtained from the spray solution without ethylene glycol had submicron size and spherical shape before and after posttreatment. The mean size of the cobalt oxide powders formed from the spray solution with concentration of ethylene glycol of 0.7M was 180 nm after post-treatment at temperature of $800^{\circ}C$. The mean size of the powders could be controlled from several tens nanometer to micron sizes by changing the post-treatment temperatures in the preparation of cobalt oxide powders by low pressure spray pyrolysis process.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.1
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• pp.61-72
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• 2014

Study on effluent organic matter (EfOM) characteristic and removal efficiency is required, because EfOM is important in regard to the stability of effluents reuse, quality issues of artificial recharge and water conservation of aqueous system. UV technology is widely used in wastewater treatment. Many reports have been conducted on microbial disinfection and micro pollutant reduction with UV treatment. However, the study on EfOM with UV has limited because low/medium pressure UV lamp is not sufficient to affect refractory organics. The high intensity of pulsed UV would mineralize EfOM itself as well as change the characteristics of EfOM. Chlorine demand and DBPs formation is affected on the changed amounts and properties of EfOM. The objective of this study is to investigate the effect on EfOM, chlorine residual, and chlorinated DBPs formation with low pressure and pulsed UV treatment. The removal of organic matter through low pressure UV treatment is insignificant effect. Pulsed UV treatment effectively removes/transforms EfOM. As a result, the chlorine consumption is changed and chlorine DBPs formation is decreased. However, excessive UV treatment caused problems of increasing chlorine consumption and generating unknown by-products.