• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.87-89
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• 2009

In the present paper, transition turbulence model is applied to the NACA64(3)618 and detailed flow features are studied. The turbulence model is sensitive to the boundary layer grid quality and y+ of the grid was limited to 1. The prediction of the transition region is dependent on the local flow condition. The pressure coefficient distribution of the transition turbulence model is compared with that of the fully turbulent mode and the drag distribution of the transition turbulence model was compared with that of the wind tunnel test.

• 한국자동차공학회논문집
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• 제8권1호
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• pp.40-47
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• 2000

A model for the prediction of combustion and exhaust emissions of DI diesel engine has been formulated and developed. This model is a quasi-dimensional phenomenological one and is based on multi-zone combustion modelling concept. This model is developed based on the concept of Hiroyasu's multizone combustion models. It takes nozzle injection (spray) parameters, induction swirl into consideration and the models of zone velocity, air entrainment, fuel droplet evaporation and mixture combustion are upgraded. Various parameters, such as cylinder pressure, heat release rate, Nox and soot emission, and these parameters in the zone are simulated. The results are compared with the experimental ones, too.

• 한국농공학회논문집
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• 제52권2호
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• pp.1-9
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• 2010

This study was carried out to comparison of coefficient of consolidation and the prediction of excess pore water pressure in agricultural reservoir on soft clay ground. For the purpose of verification of the proposed equation, laboratory model tests and field tests were performed and excess pore water pressure was compared to those predicted with the Terzaghi's method. The predicted excess pore water pressure according to ponding was very applicable to practice because it was close to the observed data. Also, for the comparison of coefficient of consolidation, the oedometer, constant rate of strain (CRS), and Rowe cell tests were performed. The coefficient of consolidation at the Rowe cell and CRS tests showed a greate increase than in the oedometer test. The ratio of the vertical and horizontal coefficient of consolidation showed a large difference according to various tests method and mixing ratio. Therefore, it is recommended that careful attention should be paid to predicting the required consolidation period in agricultural reservoir.

• 한국유체기계학회 논문집
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• 제3권3호
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• pp.31-40
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• 2000

A computer program is developed for the prediction of the aerodynamic performance and the noise characteristics in the basic design step of axial flow fan. The flow field and the performance of fan are analyzed by using the streamline curvature computing scheme with total pressure loss and flow deviation models. Fan noise is assumed to be generated due to the pressure fluctuations induced by wake vortices of fan blades and to radiate via dipole distribution. The vortex-induced fluctuating pressure on blade surface is calculated by combining thin airfoil theory and the predicted flow field data. The predicted performances, sound pressure level and noise directivity patterns of fan by the present method are favorably compared with the test data of actual fan. Furthermore, the present method is shown to be very useful in optimizing design variables of fan with high efficiency and low noise level.

• 대한기계학회논문집B
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• 제20권8호
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• pp.2572-2592
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• 1996

A low-Reynolds-number second moment turbulence closure was developed with the aid of DNS data. Model coefficients of nonlinear return to isotropy term were derived by use of Cayley-Hamilton theorem and two component turbulence limit condition as the functions of invariances of anisotropy and turbulent Reynolds number. Launder and Tselepidakis' cubic mean pressure strain model was modified to fit the predicted pressure-strain components to the DNS data. Two component turbulence limit condition was the precondition to be satisfied in developing the second moment turbulence closure for the realizable Reynolds stress prediction. But the satisfactions of Reynolds stress level and pressure-strain level of each component were compromised because the satisfaction of both levels was impossible.

• 대한기계학회논문집
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• 제18권3호
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• pp.584-590
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• 1994

A theoretical model has been developed to analyze the jet-edge interaction and the sound radiation. The edge responding to the sinuous impinging jet is regarded as an array of dipoles and their strength is determined by the boundary condition on the edge surface. The surface pressure distribution and the edgeforce are estimated using these dipoles. Then the pressure amplitude and directivity of the sound field is obtained by summing the radiating sounds from the dipole sources. It is found that the effective source is located a little distance downstream from the edge tip. And the directivity of the sound radiation is cardioid pattern near the edge but dipole pattern far from the edge. The theoretical model is confirmed by comparing the theoretical prediction of the edgeforce and sound pressure level with available experimental data.

• 대한기계학회논문집
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• 제17권7호
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• pp.1841-1850
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• 1993

A simplified one-dimensional analysis has been performed to predict the local pressure distributions in Y-Jet twin-fluid atomizers. Fluid compressibility was considered both in the gas(air) and two-phase(mixing) ports. The annular-mist flow model was adopted to analyze the flow in the mixing port. A series of experiments also has been performed; the results show that the air flow rate increases and the liquid flow rate decreases with the increase of the air injection pressure and/or with the decrease of the liquid injection pressure. From the measured injection pressures and flow rates, the appropriate constants for the correlations of the pressure loss coefficients and the rate of drop entrainment were decided. The local pressures inside the nozzle by prediction reasonably agree with those by the experiments.

• 대한간호학회지
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• 제41권3호
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• pp.423-431
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• 2011

Purpose: The study was designed to determine the discriminating ability of a Bayesian network (BN) for predicting risk for pressure ulcers. Methods: Analysis was done using a retrospective cohort, nursing records representing 21,114 hospital days, 3,348 patients at risk for ulcers, admitted to the intensive care unit of a tertiary teaching hospital between January 2004 and January 2007. A BN model and two logistic regression (LR) versions, model-I and .II, were compared, varying the nature, number and quality of input variables. Classification competence and case coverage of the models were tested and compared using a threefold cross validation method. Results: Average incidence of ulcers was 6.12%. Of the two LR models, model-I demonstrated better indexes of statistical model fits. The BN model had a sensitivity of 81.95%, specificity of 75.63%, positive and negative predictive values of 35.62% and 96.22% respectively. The area under the receiver operating characteristic (AUROC) was 85.01% implying moderate to good overall performance, which was similar to LR model-I. However, regarding case coverage, the BN model was 100% compared to 15.88% of LR. Conclusion: Discriminating ability of the BN model was found to be acceptable and case coverage proved to be excellent for clinical use.

• 소성∙가공
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• 제23권1호
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• pp.29-34
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• 2014

The damage level of the die surface was predicted by estimating the surface roughness with a finite element analysis and the wear characteristics. Wear and friction tests were conducted to compare the wear characteristics for three kinds of surface treatments - CrN, TiAlN and AlCrN coatings. A prediction model was derived from the surface roughness results with respect to contact pressure and sliding speed which were obtained from the wear test. Surface roughness values for the damage regions of the die surface were compared between the experiments and the prediction model, which shows fairly good agreement with each other.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2009년도 정보 및 제어 심포지움 논문집
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• pp.132-134
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• 2009

Hemorrhagic shock is a common cause of death in emergency rooms. Since the symptoms of hemorrhagic shock occur after shock has considerably progressed, it is difficult to diagnose shock early. The purpose of this study was to improve early diagnosis of hemorrhagic shock using a survival prediction model in rats. We measured ECG, blood pressure, respiration and temperature in 45 Sprague-Dawley rats, and then obtained a logistic regression equation predicting survival rates. Area under the ROC curves was 0.99. The Hosmer-Lemeshow goodness-of-fit chi-square was 0.86(degree of freedom=8, p=0.999). Applying the determined optimal boundary value of 0.25, the accuracy of survival prediction was 94.7%