• Journal of the Korean Society of Mechanical Technology
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• v.13 no.3
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• pp.93-98
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• 2011

To analyze and evaluate the performance of developing air to water multi heat pump, the heat pump was installed and tested at low energy house in Daejeon, korea. Heating capacity of heat pump is 16.5KW and cooling capacity is 14.0KW. Space heating/cooling, floor heating and hot water is available. The results performance evaluation of heat pump in lab test showed that the coefficient of performance (cop) was 3.75, and heating capacity was 16.0KW in ambient temperature $7^{\circ}C$. Also at ambient temperature $-15^{\circ}C$, the COP was 1.69. At a low energy house, floor heating is controled by a floor heating water temperature and a room temperature. The COP of heat pump is decreased with frequent on/off operation for controlling of floor heating water temperature.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.1119-1124
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• 2006

The objectives of this paper are to investigate the performance of silica gel-water adsorption refrigeration system with heat recovery process from the system experiment. This system can be driven by waste heat at near ambient temperature from $60^{\circ}C$ to $90^{\circ}C$. The cooling capacity and coefficient of performance(COP) were measured from various experimental conditions. An experimental results revealed the influence of operating temperatures(hot, cooling and chilled water), water flow rates, and adsorption-desorption cycle times on cooling capacity and COP. Under the standard conditions of $80^{\circ}C$ hot water, $25^{\circ}C$ cooling water, $14^{\circ}C$ chilled water inlet temperatures and 420sec cycle time, a cooling capacity of 1.14kW and a COP for cooling of 0.55 can be achieved.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.14 no.3
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• pp.200-211
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• 1985

The paper discusses the problem of the reduction in Coefficient of Performance (COP) in a refrigerator due to the inadequate position or some flow obstacles such as shelves in a room. The propriety of the present numerical method has teen proved by experiments using the flow visualization technique. The COP are calculated from the temperature rise of the condenser whose temperature indicates the condensing temperature of refrigerant The temperature rise is predicted by the theory of the steady two-dimensional laminar natural convection. In a room size of $2m\;{\times}\;2m$ the COP are decreased by 0.3 when the gap between the wall and condenser are decreased from 10cm to 2cm. While the COP are decreased by 0.55 as the shelf length increases from 0 to 75cm.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.7
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• pp.828-833
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• 2014

In this paper, the performance characteristics for newly developed ejector refrigeration system, which is that the part of saturated vapor from liquid-vapor separator after ejector expansion process is entrained in ejector, and the saturated liquid flows in the evaporator and compressed with the rest of vapor in separator, is studied. The reasons of the performance improvement of refrigeration system are that the refrigeration capacity is increased due to quality reduction after iso-entropic expansion process by ejector and the compression work is reduced because of the relatively high pressure of vapor refrigerant before compression process. The comparison results of the ejector system entraining expansion gases with the present residential freezer show that the COP increases to 27.8% maximum in case of the pressure drop to 65% of high pressure of freezer, and to 40.1% for 75% pressure drop of refrigerant R401A. The COP improvement rate with 20%~60% pressure lift in diffuser of ejector is only 2.6%~3%.

• Journal of Korean Foot and Ankle Society
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• v.24 no.1
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• pp.14-18
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• 2020

Purpose: Chronic ankle instability is a very common abnormality of the ankle, but there is still controversy regarding its evaluation criteria. The stress view has difficulties in reflecting the patient's symptoms and treatment progress. Therefore, this study examined the relationship between the center of pressure (COP) measured by a pedobarograph and the symptoms of the patient. Materials and Methods: Thirty patients with chronic ankle instability from February to August 2018 were included. Each patient was surveyed with the foot and ankle outcome score (FAOS). The COP was measured with a foot pressure scanner, and the travel distance and ellipse area of the COP were calculated. Each patient was measured on one foot and on two feet with his or her eyes closed and open. The relationship between the COP measurement and FAOS score was analyzed using the Pearson correlation coefficient. Results: The participants were consisted of 21 male and nine female, with a mean age of 30 years, mean weight of 72 kg, and mean foot size of 259 mm. With the eyes open, the correlation coefficient between the FAOS and travel distance of the affected side was -0.394 (p<0.05) and that between the FAOS and the ellipse area of the affected side was -0.425 (p<0.05). On the other hand, no significant correlations were found between the travel distance and ellipse area of the affected side when patients closed their eyes. Conclusion: Measurement of the COP using foot pressure scanner could evaluate objectively patients with chronic ankle instability, with measurements in patients with their eyes open being more significant. Based on the findings of this study, an analysis of the COP with the patients with their eyes open and standing on one foot may help determine the management strategy and assess the progress of the patients.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.2
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• pp.182-188
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• 2011

In this paper, analysis on the performance characteristics of R744-R404A cascade refrigeration system is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooling and superheating degree, compressor efficiency, and condensing and evaporating temperature in R404A high- and R744 low-temperature cycle, respectively. The main results were summarized as follows : It was observed that the highest COP of the system is achieved by higher superheating degree in R744 cycle than that in R404A cycle. The COP of the system increased by giving the subcooling degree in both cycles. The COP of the cascade system is the highest value when the system is operated at an optimum evaporation temperature.

• The Journal of Internal Korean Medicine
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• v.36 no.4
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• pp.478-485
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• 2015

Objectives: The purpose of this study was to analyze the change of area and average velocity of the center of pressure (COP) according to gait improvement in post-stroke hemiplegic patients.Methods: We measured the area and the average velocity of COP displacement of ten post-stroke hemiplegic patients while they stood quietly on a force plate at the time of dependent and independent gait . We also measured the area and the average velocity of COP displacement of normal persons to verify differences between them and post-stroke hemiplegic patients.Results: The area of COP displacement decreased significantly, and the average velocity of COP displacement tended to decrease, but not significantly. There were significant differences in the area and the average velocity of COP displacement between post-stroke hemiplegic patients and normal persons.Conclusions: The results of this study show that postural control ability improves as gait improves.

• The Journal of Churna Manual Medicine for Spine and Nerves
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• v.8 no.2
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• pp.39-46
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• 2013

Objectives : To identify the association between cross-sectional area of lumbar regional muscle and stability(ST), center of pressure(COP) assessed by tetrax. Methods : Patients(n=55) who had taken L-SPINE MRI and Tetrax(Sunlight, Israel) were analyzed retrospectively. To evaluate the cross-sectional area of lumbar regional muscle, L-SPINE MRI was used. Data of ST, COP were accumulated by using dynamic equilibrium analysis by Tetrax. Of the lumbar regional muscles, the Psoas muscles and the Paraspinalis muscles were examined. Using Pearson correlation, we analyzed COP, ST and the difference between the cross-sectional area of lumbar regional muscles. Results : The variance of cross-sectional area of both sides of Psoas muscle and COP had moderate positive correlation(r=0.621). Between variance of cross-sectional area of both sides of Paraspinalis and lumbar regional muscle and COP there was low positive correlation(r=0.287, r=0.329) ST also had low correlation with variance of cross-sectional area of both sides of Psoas muscle. Conclusion : The variance of cross-sectional area between both sides of Psoas muscle had moderate correlation with COP.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.12
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• pp.5457-5463
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• 2011

The objective of this study is to investigate cooling performance characteristics of mobile air conditioning system using R744 as an alternative of R-134a. In order to analyze the cooling performance characteristics of the air conditioning system using R744 for a passenger vehicle, the developed air conditioning system using R744 was applied in a real passenger vehicle and tested under various operating conditions with the variation of gas-cooler inlet air conditions, evaporator inlet air temperatures and compressor speeds. As a result, cooling capacity and coefficient of performance (COP) of the tested air conditioning system decreased with the rise of the inlet air temperature of the gas cooler but increased with the rise of the inlet air temperature of the evaporator. In addition, cooling capacity and coefficient of performance (COP) increased by 42.2 % with the rise of the compressor speed from 900 rev/min to 1800 rev/min, but it decreased by 55.4%.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2146-2148
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• 2005

The 2.5GeV linac of the Pohang Light Source(PLS) is planed to be converted to a XFEL. The PAL XFEL requires a new 1.2-GeV linac that will be combined to the existing linac to increase a beam energy upto 3.7GeV. This stability is mainly determined by a low level RF drive system and klystron-modulators. The stability level of the modulator has to be improved 10 times better to meet the pulse stability of 0.02 %. The regulation methods such as traditional de-Qing and precision inverter charging technology are reviewed to find out suitable upgrade scheme of the modulators. In order to obtain electron beam of the consequently stability for XFEL linac, the pulse-to-pulse beam voltage regulation is less than +/-0.5%. To get the reliable stability of the modulator which is less than +/-0.2%, a charging section is improved in a modulator which has been operated with inverter power supply and de-Q'ing.