• 설비공학논문집
• /
• 제15권10호
• /
• pp.809-820
• /
• 2003

The present study investigates effects of flow velocity on the convective heat/mass transfer characteristics in wavy ducts of a primary surface heat exchanger application. Local heat/mass transfer coefficients on the wavy duct sidewall are determined by using a naphthalene sublimation technique. The flow visualization technique is used to understand the overall flow structures inside the duct. The aspect ratio and corrugation angle of the wavy duct is fixed at 7.3 and 145$^{\circ}$ respectively, and the Reynolds numbers, based on the duct hydraulic diameter, vary from 100 to 5,000. The results show that there exist complex secondary flows and transfer processes resulting in non-uniform distributions of the heat/mass transfer coefficients on the duct side walls. At low Re (Re<1000), relatively high heat/mass transfer regions like cell shape appear on both pressure and suction side wall due to the secondary vortex flows called Taylor-Gortler vortices perpendicular to the main flow direction. However, at high Re (Re>1000), these secondary flow cells disappear and boundary layer type flow characteristics are observed on pressure side wall and high heat/mass transfer region by the flow reattachment appears on the suction side wall. The average heat/mass transfer coefficients are higher than those of the smooth circular duct due to the secondary flows inside wavy duct. And also friction factors are about two times greater than those of the smooth circular duct.

• 한국농공학회논문집
• /
• 제65권6호
• /
• pp.51-63
• /
• 2023

To improve the problem that the settlement curve of the consolidation theory of Terzaghi does not match well with the actual settlement curve, we included a secondary compression settlement and analyzed it by varying the beginning point and then obtained the following results. The current methods of calculating the compression index from the  log𝜎 curve and the coefficient of consolidation from the time-dependent settlement curve for each consolidation pressure proved that the final settlement amount will be consistent after a long time, but the actual settlement amount will always be smaller than the predicted settlement amount during the settlement progress stage. The consolidation factors estimated by the curve fitting with the condition that the secondary compression begins in the second half of the primary compression showed similar values to the consolidation factors estimated by the curve fitting for the primary compression only, and the settlement curves were in better agreement throughout the compression. It showed different values, showing low validity. It can be inferred that secondary compression acts from the point when a significant portion of the excess pore water pressure is dissipated, and the loading stress begins to have more influence on the skeletal structure of the soil. Analysis results show that secondary compression begins at the range of 91 % to 98 % on the average degree of primary consolidation.

• 한국유체기계학회 논문집
• /
• 제15권3호
• /
• pp.25-31
• /
• 2012

A computational study on the improvement of the pressure loss of intake system, which is located at engine manifold of the combat vehicle, has been conducted using a finite-volume-based, Reynolds-Averaged Navier-Stokes (RANS) solver. The computational result of the pressure loss through the air cleaner is in good agreement with equivalent experimental data. A parametric study was done for improving of the pressure loss of intake system over the baseline case. The effects of five primary parameters such as the height of inlet, the width of interconnection pipe, the shape of drain chamber and the diameter of filter housing were considered in this study. Consequently, this computational investigation can contribute to finding an optimal guideline for the idea of improvement in the pressure loss of intake system.

• Journal of Nutrition and Health
• /
• 제27권5호
• /
• pp.460-472
• /
• 1994

Prevalences of hypertension and obesity of primary school children in Kangnung were investigated, and the correlations between blood perssure and measured anthropometry were also studied to identify the factors that influence on blood pressure. 1,164 children (602 boys and 562 girls) from five elementary schools were chosen for this study. Anthropometric measurements were taken for blood pressure, body weight, height, triceps skinfold, and circumferences of chest and arm. Data of family history of hypertension were obtained by means of prepared questionnaires. Prevalences of hypertension were 3.3% in boys and 3.1% in girls. The group with elevated blood pressure had relatively a greater frequency of familial hypertension and significantly higher mean body weight and obesity index. The prevalence of obesity was defined as percentage of children whose rates of current weight to standard weight for height and sex in Korean children were more than 120%. Prevalence of obesity were 16.3% in boys, 10.3% in girls. There findings clearly revealed the influences of above-average weight and familial hypertension on blood pressure. These results suggest that children with familial hypertension should be avoid excess adiposity and be measured blood pressure regularly.

• Journal of Mechanical Science and Technology
• /
• 제14권6호
• /
• pp.645-654
• /
• 2000

In this paper, low level control algorithms of a metal belt CVT are suggested. A feedforward PID control algorithm is adopted for line pressure based on a steady state relationship between the input duty and the line pressure. Experimental results show that feedforward PID control of the line pressure guarantees a fast response while reducing the pressure undershoot which may result in belt slip. For ratio control, a fuzzy logic is suggested by considering the CVT shift dynamics and on-off characteristics of the ratio control valve. It is found from experimental results that a desired speed ratio can be achieved at steady state in spite of the fluctuating primary pressure. It is expected that the low level control algorithms for the line pressure and speed ratio suggested in this study can be implemented in a prototype CVT.

• 한국자동차공학회논문집
• /
• 제11권5호
• /
• pp.1-6
• /
• 2003

The torque is an important measure that represents the performance of a particular engine. Furthermore the information of engine torque can be used as a primary feedback parameter in modem engine management system. In this paper, a methodology is proposed for torque estimation of SI-engine. Since the proposed method uses cylinder pressure sensor, the torque can be estimated in a simple manner. The indicated torque is estimated from the peak pressure and its location, and the load torque is observed by the state observer based on the estimated indicated torque. The proposed method is accurate and robust against the variations that affect the torque production such as spark timing, mass air flow and others. This torque estimation method may be an alternative solution to the use of engine torque maps in a modem torque-based engine management system.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집B
• /
• pp.546-551
• /
• 2001

In this paper, an algorithm to improve the optimal engine operation is suggested by increasing the CVT shift speed. By rearranging the CVT shift dynamic equation, it is found that the CVT shift speed depends on the line pressure as well as the primary pressure. Based on the shift dynamics, an algorithm to accomplish a faster shift speed is presented by increasing the line pressure. In order to apply the algorithm, dynamic models of the line pressure control valve and the ratio control valve are obtained by considering the CVT shift dynamics and model based controllers are designed. It is found from the simulation results that fuel economy can be improved by 2% in spite of the increased hydraulic loss due to the increased line pressure.

• Journal of Advanced Marine Engineering and Technology
• /
• 제7권1호
• /
• pp.14-22
• /
• 1983

The Bourdon tube pressure gauge is the most widely used primary detector for pressure in various kinds of fields recently. However in many cases lots of difficulties are encountered in telemetering, measuring the continuously changing pressure and recording as time goes by, etc. In this paper a Bourdon tube of flat-oval section is considered. On the basis of Wolf's theory, the very sensitive places are selected on the tube and full bridge arrangement is used. Then all of the characteristics are examined in order to use the pressure transducer practically into which the pressure gauge is converted. From the results, the error in meter reading is about $\pm$3% F.S., on the other hand, when measured with strain gauge, the error is within $\pm$1% F.S.. Also external acceleration on Bourdon tube hardly affect practical use.

• 한국산학기술학회논문지
• /
• 제21권7호
• /
• pp.331-341
• /
• 2020

본 연구는 고혈압, 당뇨 환자를 대상으로 경험공유 자가관리 프로그램을 시행하여 대상자들의 생리적 지수, 지식, 자가관리 이행도에 미치는 효과를 파악하기 위해 시도된 비동등성 유사실험연구이다. 2018년 5월 1일부터 10월 31일까지 G시 보건진료소에 등록된 고혈압, 당뇨병 환자 실험군 30명, 대조군 25명을 대상으로 시행하였다. 실험군은 12주간의 경험공유 자가관리 프로그램에 참여하였고 대조군은 일반적인 보건진료소의 서비스를 제공하였다. 자료분석은 SPSS/WIN 22.0 프로그램을 이용하여 x² test (Fisher's exact test), Mann-Whitney test, Ranked ANCOVA로 분석하였다. 연구결과 경험공유 자가관리 프로그램 적용 후 고혈압환자의 수축기혈압(F=14.56, p<.001), 이완기혈압((F=7.05, p=.012), 지식(F=14.30, p=.001), 자가관리 이행도(F=29.73, p<.001)에서 두 군간에 유의한 차이가 있었고, 당뇨병 환자의 지식(F=7.92, p=.010), 자가관리 이행도(F=4.54, p=.044)에서 두 군간에 유의한 차이가 있었다. 따라서 지역사회 고혈압 환자의 혈압감소와 고혈압, 당뇨병 환자의 지식향상, 자가관리 이행증진을 위해 경험공유를 활용한 자가관리 프로그램은 효과적이라 생각된다.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1997년도 춘계학술발표회논문집(1)
• /
• pp.310-315
• /
• 1997

System-Integrated Modular Advanced Reactor (SMART), where major primary components such as modular helical steam generator and self regulating pressurizer are integrated into reactor vessel, is currently under development. The pressurizer is designed to control the primary pressure mainly with partial pressure of nitrogen gas and to maintain the fluid temperature as low as possible for the purpose of minimizing steam contribution. The steam generator (SG) is designed to produce super-heated steam inside tube at power operation. Because the in-vessel pressurizer and in-vessel SG are classified as the characteristic components of SMART, it is important to perform a steady state calculation of these components in order to evaluate the adoption of these components. A steady state analysis of the in-vessel pressurizer and in-vessel SG has been performed under normal power operation and the results show an acceptable performance of the components.