• Asian-Australasian Journal of Animal Sciences
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• 제11권5호
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• pp.573-579
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• 1998

The effects of supplementation with mixed fodder or concentrate were investigated on the performance of a) growth of male lambs and kids grazing extensively under oil palm trees and b) reproduction of ewes and goats stall-fed with native herbage. Supplemented kids and lambs had higher average daily weight gain than controls but the effect was only significant for those which received concentrate (p < 0.05). Final body weight was only significantly different from controls for lambs supplemented with concentrate (p < 0.05). The ages at puberty, first mating, first conception and first kidding of supplemented goats were about 110 days earlier than those for controls (p < 0.05 or better). Supplemented goats had first mating and conceived at lower body weights (p < 0.01) than those in control groups. Different feeding regimes had no effects (p > 0.05) on the reproductive performance of ewes apart from highest body weight of first lambing in animals supplemented with concentrate (p < 0.05). Native herbage available under oil palm trees of 5 years old was sufficient for growth and reproduction of sheep and goats. Concentrate was better than mixed fodder as supplement for enhancing the reproductive performance of goats but both appeared to have limited effects on the performance of reproduction in ewes and growth in male kids.

• Asian-Australasian Journal of Animal Sciences
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• 제22권9호
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• pp.1328-1333
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• 2009

To evaluate different housing systems, 80 gilts were randomly allocated at puberty to four treatments: i) sow stall in gestation followed by farrowing crate (SC), ii) group housing with individual feeding in gestation followed by farrowing crate (GC), iii) ESF (Electronic Sow Feeding) system in gestation followed by farrowing crate (EC), and iv) ESF system followed by group farrowing pen (EG). The results showed that stalled sows had a longer interval between puberty and second estrus (p<0.001). The sows kept in the ESF system gained more body weight (p<0.01) and backfat (p<0.05) prior to service, and more backfat during gestation (p<0.05), but also had greater backfat losses in the subsequent lactation (p<0.01). Sows changing from loose housing to confinement at farrowing had longer gestation length (p<0.001). Total litter size did not differ significantly between gestation treatments, but the number of stillborn piglets was significantly higher in the SC treatment (p<0.01). After weaning, SC sows had the longest interval for rebreeding (p<0.001). Some EG sows came into heat before weaning, giving this treatment the shortest interval. These results indicate that gestation confinement in sow stalls had several detrimental effects on sow performance relative to group housing.

• 대한기계학회논문집B
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• 제27권12호
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• pp.1750-1757
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• 2003

This paper describes the flow measurements inside the blade passage of an axial flow fan by using a rotating hot-wire probe sensor from a relative flame of reference fixed to the rotor blades. The validity of fan rotor designed by a streamline curvature equation was performed by the measurement of the three-dimensional flow upstream and downstream of the fan rotor using a 5-hole pitot tube. The vortical flow structure near the rotor tip can be clearly observed by the measurements of a relative velocity and its fluctuation on quasi-orthogonal planes to a tip leakage vortex. Larger vortical flow, which results in higher blockage in the main flow, is formed according to decrease a flow rate. The vortical flow spreads out to the 30 percent span from the rotor tip at near stall condition. In the design operating condition, the tip leakage vortex is moved downstream while the center of the vortex keeps constant in the spanwise direction. Detailed characteristics of a velocity fluctuation with relation to the vortex were also analyzed.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.43-50
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• 2009

In order to reduce the download around Smart UAV(SUAV) at hovering and transition mode, flow control using synthetic jet has been performed. Many of the complex tilt rotor flow features are captured including wing leading and trailing edge separation, and the large region of separated flow beneath the wing. First, in order to control the trailing edge separation, synthetic jet is located at 30, 95% of flap chord length. The flow control using synthetic jet on flap shows that stall characteristics depending on several mode can be improved through separation vortices resizing. Also, a flap jet and a 0.01c jet which control the separation efficiently are applied at the same time at each test case because controlling the leading edge separation is essential for download reduction. As a result, time averaged download is reduced about 18% comparing with no control case at hovering mode and 48% at transition mode. These research results show that if flow control using leading edge jet and trailing edge jet is used effectively to the SUAV in overall flight mode, flight performance and stability can be improved.

• 대한조선학회논문집
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• 제44권1호
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• pp.8-15
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• 2007

In this paper, numerical calculations are performed to analyze the unsteady flow of NACA airfoil sections. In order to ease the flow computation for the fluid region changing in time, improve the quality of solution and simplify the grid generation for the oscillating foil flow, the computational method adopts a moving and deforming mesh with the multi-block grid topology. The multi-block, structured-unstructured hybrid grid is generated using the commercial meshing software Gridgen V15. The MDM (Moving & Deforming Mesh) and the UDF (User Define function) function of FLUENT 6 are adopted for computing turbulent flows of the foil in pitching motion. Computed unsteady lift and drag forces are compared with experimental data. in general, the characteristics of unsteady lift and drag of the experiments are reproduced well in the numerical analysis.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.396-401
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• 2002

The purpose of this 3-D numerical simulation is evaluate the application of a commercial CFD code to predict 3-D flow characteristics of wind turbine. The experimental approach, which has been main method of investigation, appears to be its limits, the cost increasing disproportionally with the size of the wind turbines, and is hence mostly limited to observing the phenomena. Hence, the use of Computational Fluid Dynamics (CFD) techniques and Wavier-Stokes solvers are considered a very serious contender. The flow solver CFX-TASCflow is employed in all computations presented in this paper. The 3-D flow separation and the wake distribution of 2 bladed Horizontal Axis Wind Turbines (HAWTs) are compared to Heuristic model and visualized result by NREL(National Renewable Energy Laboratory). Simulated 3-D flow separation structure on the rotor blade is very similar to Heuristic model and the wake structure of the wind turbine is good agree with visualized results.

• 대한기계학회논문집B
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• 제26권6호
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• pp.795-804
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• 2002

The optimal design code of an axial flow pump has been developed to determine geometric and fluid dynamic variables under hydrodynamic as well as mechanical design constraints. The design code includes the optimization of the complete radial distribution of the geometry by determining the coefficients of 2$^{nd}$ order polynomials to represent the three-dimensional geometry. The optimization problem has been formulated with a nonlinear multivariable objective function, maximizing the efficiency and stall margin, while minimizing the net positive suction head required. Calculation of the objective function is based on the mean streamline analysis and through-flow analysis using the present state-of-the-art model. The optimal solution is calculated using the penalty function method in which the genetic optimizer is employed. The optimized efficiency and design variables are presented in this paper as a function of non-dimensional specific speed in the range, 2$\leq$ $n_{s}$ $\leq$10. The results can be used in preliminary design of axial flow pumps.

• 한국문헌정보학회지
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• 제38권4호
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• pp.167-178
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• 2004

본 연구는 '장애인${\cdot}$노인${\cdot}$임산부 등의 편의증진보장에 관한 법률 시행규칙(1999)'에서 정한 공공도서관의 편의시설의 세부기준과 노인의 표준인체지수를 비교분석하여 시행규칙의 세부기준에서 제시한 수치가 노인에게도 적합한지를 조사 분석한다. 본 연구에서 조사대상으로 선정한 편의시설의 종류는 출입구(문), 복도 및 통로, 계단, 승강기, 에스컬레이터, 경사로, 대변기 소변기, 접수대 또는 작업대, 그리고 우체통으로 총 10가지이며, 이들 각각의 세부기준에 대한 적합성을 밝힌다.

• 한국자동차공학회논문집
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• 제10권1호
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• pp.244-254
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• 2002

To enhance the acceleration performance and fuel consumption rate of a vehicle, the torque converter is modified or newly-developed with reliable analysis model. Up to recently, the one dimensional performance model has been used for the analysis and design of torque converter. The model is described with constant parameters based on the concept of mean flow path. When it is used in practice, some experiential correction factors are needed to minimize tole estimated error. These factors have poor physical meaning and cannot be applied confidently to the other specification of torque converter. In this study, the detail dynamic model of torque converter is presented to establish the physical meaning of correction factors. To verify the validity of model, performance test was carried out with various input speed and oil temperature. The effect of oil temperature on the performance is analysed, and it is applied to the dynamic model. And, to obtain the internal flow pattern of torque converter, CFD(Computational Fluid Dyanmics) analysis is carried out on three-dimensional turbulent flow. Correction factors are determined from the internal flow pattern, and their variation is presented with the speed ratio of torque converter. Finally, the sensitivity of correction factors to the speed ratio is studied for the case of changing capacity factor with maintaining torque ratio.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1482-1489
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• 2007

In this paper, characteristics of infrasound and low-frequency noise emission from large modern wind turbines are experimentally investigated. The sound measurement procedures of IEC 61400-11 and ISO 7196 are utilized to field test and evaluation of noise emission from each of 1.5 MW and 660 kW wind turbines using the stall regulation and the pitch control for the power regulation, respectively. It was found that the G-weighted SPLs of low-frequency noise including infrasound shows positive correlation with the wind speeds, irrespective of methods of power regulation. This highlights the potential complaint of local community against the infrasound and low-frequency noise of wind turbines. The comparison of measured data with the existing hearing thresholds and criteria curves shows that it is highly probable that the low-frequency noise from the 1.5 MW and 660 kW wind turbines in the frequency range over 30 Hz leads to the psychological complaint of ordinary adults, and that the infrasound in the frequency range from 5 Hz to 8 Hz causes the complaint by rattling the house fitting such as doors and windows.