• 대한간호학회지
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• 제39권2호
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• pp.198-206
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• 2009

Purpose: The purposes of this study were to identify the prevalence of postprandial hypotension (PPH) and risk factors for PPH in Korean elderly people. Methods: A cross-sectional descriptive study was conducted with community dwelling and nursing home residents. The blood pressure of 162 adults aged 65 yr or older was measured before meal as a baseline and then at 15 min intervals from immediately after the meal through 90 min after the meal. Descriptive statistics and logistic regression with the SPSS WIN 14.0 program were used to analyze the data. Results: The prevalence of PPH was 29% and the PPH occurred immediately after the meal continuously through 90 min after the meal. The biggest drop in systolic blood pressure occurred at 45 min after the meal. Risk factors for PPH were age, base line systolic blood pressure, and presence of cardiovascular disease. Conclusion: To prevent side effects of PPH such as falls and syncope, nurses should provide careful management of PPH and prohibit activities until at least 90 min after a meal. We also recommend that risk of PPH should be included in fall prevention guidelines for elderly people.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1945-1950
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• 2004

In this paper, The performance of Kim-Chi refrigerator with three evaporator and one compressor was investigated in employing 55% propane and 45% isobutane (R290/R600a) refrigerant mixture as an alternative refrigerant of R134a. The drop in test was performed by varying both refrigerant charge amount and capillary tube length in order to find both the performance and reliability of a small multi-refrigeration system. As a result, Both the power consumption and COP is increased by about 15% and 10%, respectively as compared to the baseline R134a system. In addition, the propane/isobutene refrigerant mixture system took advantage of the minimization of modification and redesigning of system components because of similar thermodynamic properties with R134a such as saturation pressure, temperature, normal boiling point(NBP) characteristics

• International Journal of Air-Conditioning and Refrigeration
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• 제16권2호
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• pp.44-50
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• 2008

This study presents test results of a mobile air-conditioning system using a potential alternative refrigerant, R152a. A series of performance tests have been carried out and cycle characteristics such as cooling capacity, energy efficiency ratio, suction and discharge pressures, and temperatures are presented, compared to those for the baseline R134a system. Tests were conducted with evaporation temperature of $5^{\circ}C$, condensation temperature of $45^{\circ}C$, subcooling temperature of $5^{\circ}C$, superheating temperature of $5^{\circ}C$, and compressor speed of 500-1500 rpm. The performance of R152a system with readjustment of an expansion valve showed better than those of R134a. The effect of oil on the pressure drop in the evaporator was also addressed.

• 한국전산유체공학회지
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• 제21권2호
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• pp.112-119
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• 2016

NEXTSat-1 is the next-generation small-size artificial satellite system planed by the Satellite Technology Research Center(SatTReC) in Korea Advanced Institute of Science and Technology(KAIST). For the control of attitude and transition of the orbit, the system has adopted a RHM(Resisto-jet Head Module), which has a very simple geometry with a reasonable efficiency. An axisymmetric model is devised with two coil-resistance heaters using xenon(Xe) gas, and the minimum required specific impulse is 60 seconds under the thrust more than 30 milli-Newton. To design the module, seven basic parameters should be decided: the nozzle shape, the power distribution of heater, the pressure drop of filter, the diameter of nozzle throat, the slant length and the angle of nozzle, and the size of reservoir, etc. After quasi one-dimensional analysis, a theoretical value of specific impulse is calculated, and the optima of parameters are found out from the baseline with a series of multi-physical numerical simulations based on the compressible Navier-Stokes equations for gas and the heat conduction energy equation for solid. A commercial code, COMSOL Multiphysics is used for the computation with a FEM (finite element method) based numerical scheme. The final values of design parameters indicate 5.8% better performance than those of baseline design after the verification with all the tuned parameters. The present method should be effective to reduce the time cost of trial and error in the development of RHM, the thruster of NEXTSat-1.

• 설비공학논문집
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• 제27권6호
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• pp.321-327
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• 2015

This study presents an HFC152a refrigerant air conditioner as an alternative to HFC134a, which is currently used in mobile air conditioning systems. Cool-down performance tests of an HFC152a air conditioning system were conducted and compared to a baseline HFC134a air conditioner. The experimental set-up consisted of a belt-driven compressor, a sub-cooled type condenser, an evaporator, and a block-type thermal expansion valve (TXV). A drop-in test was carried out on the mobile air conditioning system under various vehicle running speeds in a climate-controlled wind tunnel (CWT). Additionally, to optimize the HFC152a air conditioning system, the effects of the TXVs on the performance were studied. The results show that compared to the HFC134a air conditioning system, the refrigerant charge quantity was reduced by approximately 20%, the discharge pressure was reduced by about 350~430 kPa, and the air discharge temperature at vehicle running conditions was $0.5{\sim}1.5^{\circ}C$ lower. In addition, good compressor durability was expected due to the lower compression ratio.

• 대한기계학회논문집B
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• 제29권2호
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• pp.271-278
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• 2005

In this paper, the performance of Kim-chi refrigerator with three evaporator and one compressor was investigated in employing $55\%$ propane and $45\%$ isobutane (R290/R600a) refrigerant mixture as an alternative refrigerant of R134a. The drop-in test was performed by varying both refrigerant charge and capillary tube length in order to find both the performance and reliability of a small multi-refrigeration system. Results show that the power consumption is decreased by about $15\%$ and COP is increased by about $10\%$, respectively as compared to the baseline system using R-134a. In addition, the propane/isobutane refrigerant mixture system took advantage of the minimization of modification and redesigning of system components because thermodynamic properties such as saturation pressure, temperature, normal boiling point(NBP) characteristics are similar to those of R134a. The reduction of sales cost is caused by the decrease of refrigerant cost per unit mass and refrigerant charge amount necessary for the refrigeration system.

• 셀메드
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• 제3권2호
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• pp.13.1-13.6
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• 2013

The objective of the current study was to find out the effect of Integrated Amrita Meditation Technique (IAM) on blood pressure (BP), heart rate (HR), respiratory rate (RR) and IgA. One hundred and fifty subjects were randomized into three groups IAM, Progressive Muscle Relaxation (PMR) and Control. Baseline values were collected before giving the training for all the subjects and the IAM and PMR groups were given training in the respective techniques. BP, HR, RR and IgA were recorded manually at 0 h, 48 h, 2 months and 8 months after the first visit. HR was found to be reduced in the IAM group 48 h onwards and the fall sustained till 8 months (p < 0.05). IAM group showed significant drop when compared to the PMR group and control group in all the subsequent visits (p < 0.05). RR decreased significantly in the IAM group in the third and fourth visits (p < 0.05). RR of IAM showed significant decrease when compared to PMR and control from the third visit onwards. IgA showed significant increase in comparison with PMR and control in the third and fourth visits. BP did not show any difference in any of the visits. There was subject dropout from randomization to completion of the study, in all the three groups. The significant decrease in HR and RR and increase in IgA in the IAM group when compared to the PMR and control group shows the efficacy of the technique in reducing the physiological stress indicators for up to 8 months.