• 오토저널
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• 제10권6호
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• pp.85-91
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• 1988

The purpose of this study is to investigate the flow through the intake and exhaust system of a spark ignition engine. The flow was assumed to be one-dimensional, compressible and unsteady, and carburetor, muffler, valve and junction are modelled as boundary conditions according to their flow characteristics. In the experiment, four cylinder gasoline engine is used and the pressures in the intake and exhaust pipes and in the cylinder are measured and compared with the results of numerical analysis. In consequence of the comparison, four periods of pressure wave in a cycle are observed in both case of experiment and prediction. In case of exhaust pipe, the results obtained from the experiment are in accord with that from calculation. The results of the intake system show some differences with each other due to the complication in shape, but the periods of both case concur well.

• 한국자동차공학회논문집
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• 제5권6호
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• pp.1-12
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• 1997

In an SI engine, the characteristics of the air flow is important not only for the design of the intake system geometry but also for the accurate measurement of the induction air mass. In this study, an air flow rate measurement using the ultrasonic flow meter and hot wire flow meter was conducted at the upstream of the intake port and the throttle. At the upstream of the intake port, the pulsating flow into the cylinder affected by the pressure wave was detected directly with the flow meters instead of pressure sensors. At the upstream of the throttle, the reverse flow phenomena were showed by comparing the flow pattern measured by the hot wire air flow meter and the ultrasonic air flow meter. The results of this study can be used for the analysis of the tuning effect in the intake manifold and estimation of the error in real time measurement for the air flow rate.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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• pp.132-135
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• 2011

초음속 흡입구의 충격파 안정성과 높은 압축효율을 획득하기 위한 버즈여유 결정기법을 제안하였다. 충격파 평형 방정식을 이용하여 자유흐름 및 배압에 의한 종말 충격파 위치의 민감도를 유도하였고, 외란의 크기를 통계적 방법에 의해 정량화 하였다. 수치적 계산결과 종말 충격파의 운동은 마하수에 비례하는 민감도 특성을 보였고, 후단 배압에 의한 그 영향이 가능 큰 것으로 나타났다.

• Journal of Nutrition and Health
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• 제31권4호
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• pp.777-786
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• 1998

The purpose of this study to investigate the relationship between nutrient intake and serum lipid levels in 165 healthy women in Taegu. A convenient method was to assess nutritional intake. Anthropometric measurement of body weight and height were measured and average energy expenditure calculated . The mean body mass index (BMI) was 23.4$\pm$3.1 and it was higher than the mean BMI of Korean women. Obesity rates for the study subjects were 15.7% by RBW (relative body weight : >120%) and 28.5% by BMI(body mass index) ; >25). Daily energy intake was sufficient at 106% of recommended dietary allowances and the energy percentage ration of carbohydrate , fat and protein was 68 : 18 : 14. Mean intake of vitamin A, B1 , niacin , and Ca were higher than RDA. The incidence of hypertension(>140mmHg) and hypercholoesterolemia(>240mg/dl) as 18.2% and 23.6% of the subjects, respectively . Postmenopasusal women showed significantly higher blood pressure, RBW, and ALP (alkaline phosphatase) than premenopausal women. The concentration of cholesterol and average blood pressure in the irregular meal eater group were significantly higher than in the regular meal eater group. Skipping meals and unenvendurnal distribution(no breakfast, or no lunch , and large evening meals) are associated with high total cholesterol level in this population . Especially, the atherogenic index was significantly lower in the regular meal eater group than that in irregular meal eaters. The values for serum cholesterol, triglyceride, blood pressure, BMI, and atherogenic index increased with age in middle-aged women. There was a highly significant correlation between body weight and plasma lipids. HDL -cholesterol was inversely correlated with BMI. The above dta provides valuable information for community program planning and health providers who work with individual female and adults to meet their nutrietional needs to control blood lipids.

• Journal of Nutrition and Health
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• 제30권2호
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• pp.170-176
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• 1997

Twenty two hypertensive and thirty normotensive in-patients were participated in this study to investigate the relationship between plasma renin activity and metabolism of Ca and Na, Prior to pharmacological treatments, renin activity, aldosterone and parathyroid hormone(PTH) levels were measured from the fasting blood samles. Twenty four hour urine samples were collected to analyze urinary levels of creatinine, Ca, Na and K. Habitual intake of Na and Ca were also measured for hypertensive and normotensive patients. Hypertensive subjects were classified into higher reinin hypertensive (HH), medium renin hypertensive(MH) and low renin hypertensive (LH) group according to their renin activities. PTH level of LH group was the highest among three hypertensive groups. It appeared that aldosterone levels of HH group were significantly higher than LH or MH groups(p<0.05). However there were no significan시 differences in aldosterone level between LH group and normotensive group. Habitual intake of Na and Ca were highest in LH group but lowest in HH group, however, they were not statistically different. Positive correlations of systolic blood pressure with PTH(r=0.2597) and aldosterone(r=0.26480existed(p<0.05). Urinary Ca level was positively correlated with urinary Na(r=0.5619), K(r=0.4533) and habitual Na intake(r=0.3253). Above results suggested the possible relationships among renin activity, habitual Ca intake and Na intake and suggested a further study on the interrelationship between the hormonal control of Ca and Na metabolism and blood pressure in hypertension.

• Journal of Nutrition and Health
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• 제30권3호
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• pp.277-285
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• 1997

The purpose of this study was to investigate the relationship among nutrient intake, life style, and serum lipids level in 108 healthy middle-aged men in Taegu. A convenient method was to assess nutritional intake. Anthropometric measuement of body weight and hight were measured and average energy expenditure was calculated. The mean body mass index(BMI) was 22.8$\pm$2.4 and it was in the middle of the mean BMI of Korean men. Obesity rate of study subject were 13.2%. Daily energy intake was not sufficient as 88.4% of recommended dietary allowances and the energy percentage of carboydrate, fat protein was 65 : 21 : 14. Mean intake of vitamin A, B1, C and Ca were lower than RDA. There was a highly significant negative correlation between the systolic blood pressure and calcium intake(r=-0.28, p<0.05). Smokers showed significantly higher blood glucose than non-smokers. Skipping meals and uneven diurnal distribution(no breakfast and large evening meals) are associated with high triglyceride level in this population. There was a highly significant correlation between body weight and plasma lipids. Energy expenditure was negatively correlated with plasma triglyceride level. Especially, atherogenic index was significantly lower in job-time physically active worker than that in sedentary worker. Above data provides valuable imformation to the community for program planning as well as to health providers who work individual male adults to meet their nutrition needs and to control blood lipids.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.207-210
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• 2008

본 논문에서는 램제트 기관의 성능을 결정짓는 공기흡입구를 램제트 엔진의 비행 목적에 맞게 비행 마하속도 4에서 기본설계를 수행하였다. 순항고도 12km, Mach $2{\sim}6$의 넓은 영역에서의 운용을 가능하게 하기 위하여 가변형 공기흡입구의 개념을 도입하였다.

• 한국분무공학회지
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• 제23권2호
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• pp.58-65
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• 2018

An analytic strategy to control the variable valve actuation applied to two intake valves (flow port intake valve and swirl port intake valve) was performed in this study. we considered the variation in phasing of intake valve profiles by using the Cam-in-Cam technology. The analytic model was implemented in the GT-Power simulation program and analyzed the result of regulated emissions such as, NOx and Soot, especially with IMEP characteristics. Namely, we meticulously investigated the sources of having effect on the amount of NOx and soot formation under the test conditions with retard timing of both flow port and swirl port intake valves for decreasing the opening duration by 35CAD. Also, we analyzed the effect of incylinder pressure and temperature with NOx variations and in-cylinder pressure and temperature on NOx variations and normalized turbulent intensity. Through this analysis, some useful results on the combustion and flow characteristics of the swirl port and flow port control of the intake valve were obtained by this study.

• Journal of Advanced Marine Engineering and Technology
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• 제32권8호
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• pp.1141-1148
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• 2008

One of the methods to increase the efficiency of an engine is to expand pressures obtained from combustions equal to the pressure of atmosphere as much as possible and then convert thermal energy into mechanical energy also as much as possible. In this research, the Diesel cycle was thermodynamically interpreted to evaluate the possibility of high efficiency by converting Diesel engines to the Atkinson cycle, and general cycle features were analyzed after comparing these two cycles. In the case of fuel air the Diesel-Atkinson cycle considering intake and exhaust similar to real cycles, the value of thermal efficiency and average effective pressure increased, though their values were smaller than those of standard air amount cycle, when expansion compression ratio increased. When normal Diesel engines of which compression stroke and expansion stroke are all the same, was converted to the Atkinson cycle by changing the time of intake value close, combustion pressure reduced due to reduced expansion compression ratio and intake air amount due to decreased effective cycle volume.

• 한국수소및신에너지학회논문집
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• 제26권1호
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• pp.28-34
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• 2015

HCCI (Homogeneous Charged Compression Ignition) hydrogen engine has relatively narrower operation range caused by backfire occurrence due to the rapid pressure rising by using higher compression ratio and significant reaction velocity. In this study, to grasp of backfire process and characteristic in the HCCI research hydrogen engine, in-cylinder pressure, intake pressure and backfire limit range are analyzed with compression ratio and intake valve open timing, experimentally. As the result, it is observed that knock is occurred just before backfire occurrence in HCCI hydrogen engine but not spark igntion type, this phenomenon is always the same for the above variables. Also backfire limit range are expanded up to 50% for the more retarding intake valve open timing in this operating conditions.