• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.393-398
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• 2008

In order to protect the environment from the refrigerant pollution, the $CO_2$ may be regarded as one of the most attractive alternative refrigerants for an automotive air-conditioning system. Control methods for a $CO_2$ system should be different because of the unique property of a $CO_2$ as a refrigerant. Especially, the high-side pressure of a $CO_2$ system should be controlled for the efficient operation. The high-side pressure algorithm being composed of the pressure setpoint algorithm and the pressure setpoint reset algorithm was developed. The pressure setpoint algorithm, by using a least square method, was developed. The pressure setpoint reset algorithm, by using a fuzzy logic and by using a proportional logic, was also developed and compared. Simulation results showed that a proportional logic was more practical than a fuzzy logic for the pressure setpoint reset algorithm.

• International Journal of Advanced Culture Technology
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• 제6권4호
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• pp.205-213
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• 2018

This research is about effects of obesity adults participating in 12weeks of boxing diets program on weight loss, blood pressure and blood sugar improvements. The exercise program was conducted three times a week with a maximum heart rate of 50 to 65 percent for first to forth weeks and 65 to 85 percent for fifth to twelfth. The study included 59 obese people in their 20s and 50s, with a BMI of 25kg/m2 or higher, blood pressure of 140/90mmHg, and high blood pressure and diabetes patients of 125 mg/dl per fasting blood sugar. The following results were obtained by observing the results before and after the boxing exercise program. High blood pressure, diabetes, high blood pressure + diabetes after 12 weeks showed significant weight, BMI and body fat reduction, as well as significant decrease in blood pressure and fasting blood sugar. Consequently, through this study, obese adults can lower their weight, blood pressure, and blasting fasting blood sugar through a 12-week high-strength boxing exercise program and it is believed to help improve and prevent obesity, cardiovascular disease and metabolic diseases.

• 가정과삶의질연구
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• 제27권5호
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• pp.195-206
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• 2009

The main purpose of this study was to examine the effects of maternal achievement pressure and emotional support on adolescents' achievement motivation. A total of 241 adolescents in the second grade of two middle schools in Seoul and their mothers participated in the study, and completed questionnaires on mothers' achievement pressure and emotional support. Adolescents also answered a questionnaire on achievement motivation. Sohn's(1997) Achievement Pressure Scale, Sung's(1993) Social Support Scale and Hermans'(1970) Prestatie Motivatie Scale were used for this survey. Data were analyzed by Pearson's correlation coefficients, t-tests, regressions, and one-way ANOVA with Duncan's multiple range tests. Results showed that maternal achievement pressure and emotional support and adolescents' achievement motivation did not vary as a function of sex. Maternal achievement pressure and emotional support had positive effects on achievement motivation of adolescents, and maternal achievement pressure played a more influential role on the motivation of adolescents than emotional support. Among four groups divided by the level of maternal achievement pressure and emotional support, high/high, high/low, low/high, and low/low, adolescents in the high/high group were perceived to have the highest achievement motivation. Findings suggest that both maternal achievement pressure and emotional support are important in improving adolescents' achievement motivation.

• 한국자동차공학회논문집
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• 제8권4호
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• pp.10-17
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• 2000

This work presents an investigation of aerodynamic characteristics of fuel spray injected from a high pressure hollow cone swirl injector into a constant volume chamber. Laser tomography visualization was used to interrogate the fuel and air mixing characteristics and the effect of chamber pressure and temperature increase was analyzed, Preliminary results on spray development showed that mixing effect tends to increase with the increase of injection pressure and chamber gas pressure yielding a decrease of spray penetration and an attenuation of well-defined vortex structure. Topological analysis of the spray structure has been performed to initiate the understanding of mixing and vaporization process. For the present experimental conditions fuel injection pressure and chamber gas pressure appear as the dominant factors which govern the transient mixing characteristics. Moreover spray atmixation characteristics are improved by increasing chamber gas temperature.

• 한국유체기계학회 논문집
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• 제3권2호
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• pp.57-65
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• 2000

The aim of this paper is to understand the unsteady flow phenomena in a high speed centrifugal compressor channel diffuser. Instantaneous pressures aye measured at six locations in the diffuser using fast-response pressure transducers. Instantaneous pressure ratio decomposition was applied to analyze the pressure signal. In vaneless space where impeller-vaned diffuser interaction is strong, aperiodic unsteadiness is high and periodic pressure waveforms by blade passing are not clear at low flow rates, especially near vane suction side. High aperiodic unsteadiness decreases downstream of diffuser. The blade-to-blade pressure wave does not disappear in surge flow condition. In surge there exist not only large scale periodic surge wave but also blade-to-blade pressure wave.

• 한국자동차공학회논문집
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• 제4권2호
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• pp.137-146
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• 1996

Behaviour of ultra-high pressure diesel spray and its structure in a constant-volume pressure chamber were studied with injection pressure ranging from 35 to 110MPa. Sprays were observed by using the back illumination scattering method and righ angle scattering method. The spray process mechanism were investigated with both photographs. As a result, the spray angle and air entrainment angle was larger as injection pressure and back pressure increase. It becomes clear that mean air-fuel ratio is increased by increasing the injection pressure.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.812-817
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• 2001

Impinging spray characteristics were investigated to find suitable injection pressure by using high pressure injection system. Spray radius and spray height were increased continuously until 2,500bar but the rate of enhancement was decreased suddenly over this injection pressure region. It is expected that the maximum suitable injection pressure of impinging spray exists at around 2,500bar.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1999년도 유체기계 연구개발 발표회 논문집
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• pp.69-77
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• 1999

The aim of this paper is to understand the unsteady flow phenomena in a high speed centrifugal compressor channel diffuser. Instantaneous pressures are measured at six locations in the diffuser using fast-response pressure transducers. Instantaneous pressure ratio decomposition was applied to analyze the pressure signal. In vaneless space where impeller-vaned diffuser interaction is strong, aperiodic unsteadiness is high and periodic pressure waveforms by blade passing are not clear at low flow rates, especially near vane suction side. High aperiodic unsteadiness decreases downstream of diffuser. The blade-to-blade pressure wave does not disappear in surge flow condition. In surge there exist not only large scale periodic surge wave but also blade-to-blade pressure wave.

• 대한치과기공학회지
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• 제16권1호
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• pp.5-11
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• 1994

On purpose of relative comparison of between air-vent attached pattern and non attached one, casting tests were accomplished by castability analysis unrig wax screen mesh pattern. Experimental specimens are divided Into 4groups. 1) Air-vent attached pattern with high casting pressure(coil spring type centrifugal casting machine 2.5turn). 2) Air-vent attached pattern with low casting pressure(coil spring type centrifugal casting machine 1.5turn). 3) Air vent non attached pattern with high casting pressure(coil spring type centrifugal casting machine 2.5turn). 4) Air-vent non attached pattern with low casting pressure(coil spring type centrifrgal casting machine 1.5turn). The main results are as follows : 1) The condition of high casting pressure no.1, no.3 were showed perfect castability. 2) The condition of low-casting pressure, there is a wide difference between no.2, no.4 group. Castability of no.2 group preferable to no.4 group(p<0.001). 3) Low casting pressure and complex shape cause the low-castability. So it is recommanded that use of air-vent in case of complex shaped wax pattern with low easting pressure.

• 한국분무공학회지
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• 제20권1호
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• pp.43-52
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• 2015

Experimental study was conducted to investigate the effects of ultra-high injection pressure and nozzle hole diameter on diesel flow and spray characteristics. Electronically controlled ultra-high pressure fuel injection system was made to supply the fuel of ultra-high pressure consistently. Three injection pressures, 80, 160, and 250MPa were applied. Four type of injectors with identical eight nozzle holes were used. The four injectors have nozzle hole diameters of 115, 105, 95, and $85{\mu}m$ respectively. Injection quantity and rate were measured to investigate flow characteristics according to injection pressures and nozzle hole diameters. Mie-scattering and shadowgraph were performed to visualize liquid and vapor phases of diesel spray in a constant volume combustion chamber (CVCC). Ambient conditions of high pressure and high temperature in a diesel engine were simulated by using CVCC.