• Wind and Structures
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• v.9 no.1
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• pp.23-35
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• 2006

The effect of buildings on flow in urban canopy is one of the most important problems in local/micro-scale meteorology. A large eddy simulation model is used to simulate the flow structure in an urban neighborhood and the bulk effect of the buildings on surrounding flows is analyzed. The results demonstrate that: (a) The inflow conditions affect the detailed flow characteristics much in the building group, including: the distortion or disappearance of the wake vortexes, the change of funneling effect area and the change of location, size of the static-wind area. (b) The bulk effect of the buildings leads to a loss of wind speed in the low layer where height is less than four times of the average building height, and this loss effect changes little when the inflow direction changes. (c) In the bulk effect to environmental fields, the change of inflow direction affects the vertical distribution of turbulence greatly. The peak value of the turbulence energy appears at the height of the average building height. The attribution of fluctuations of different components to turbulence changes greatly at different height levels, in the low levels the horizontal speed fluctuation attribute mostly, while the vertical speed fluctuation does in high levels.

• Structural Engineering and Mechanics
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• v.49 no.4
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• pp.523-536
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• 2014

Before incorporating the earthquake-resistance design in design standard (1988) in South Korea, most of existing residential buildings were built without having lateral resistance capacity in addition to their structural peculiarity, such as exterior stair ways, exterior elevator room. For these reasons, the demands on retrofitting research for existing buildings arise recently and many retrofitting methods are proposed. These tasks are important to reduce the enormous economic loss and environmental issues. As the main purpose, this study was intended to examine the performance improvement in terms of ductility and strength in the wake of retrofitting and to suggest retrofitting details.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.91-98
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• 2000

Developed is a computer program for the prediction of the aero-acoustic performance characteristics such as discharge pressure, efficiency, power and noise level in the basic design step of axial flow fan. The flow field and the aerodynamic 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 aerodynamic performances, sound pressure level and noise directivity patterns of fan by the present computer program are favorably compared with the test data of actual fan. Furthermore, the present computer program is shown to be very useful in optimizing design variables of fan with high efficiency and low noise level and in analyzing their design sensitivities.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.11
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• pp.1552-1558
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• 2002

The blade leading edge is modified to control the secondary flow generated in the turbine cascade with fence by intensifying the suction side branch of the horseshoe vortex. The incompressible Navier-Stokes equations are numerically solved with a high Reynolds number k-$\varepsilon$ turbulence closure model for investigating the vortical flows in the turbine cascade. The computational results of total pressure loss coefficients in the wake region are first compared with experiments for validation. The structure and strength of the passage vortex near the suction surface are examined by testing various geometrical parameters of the turbine blade leading edge.

• Sleep Medicine and Psychophysiology
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• v.1 no.2
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• pp.182-187
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• 1994

The Authors report a case of sleep paralysis patient who is 25-years old man. He complained that he has been experiencing episode "being suffocated" during sleep and could not move by himself while semiconsciousness state. He was a only son of divorced parents and could not attach anybody from yong childhood. His symptoms was began intermittently after his early teens. Medical history and physical examination revealed no significant finding. A nocturnal polysomnogram showed loss of muscle tone during terminal REM period and sudden hyperventilation attack followed by wake-up. Psychosocial stress and insufficient sleep were presumed to be an etiological factors. Imipramine 50mg per day almost completely relieved symptoms.

• Health Policy and Management
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• v.28 no.3
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• pp.308-314
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• 2018

Injury is a serious problem that not only causes death but also significantly degrades the quality of life of the people and causes loss of socioeconomic opportunities and costs. Damage occurs as a result of an accident. Among them, natural disasters and artificial disasters take lives of many people in a short time and threaten their physical and mental health. The United States has responded to the disaster by establishing relevant laws and regulations and a response system with the recognition that health is recognised soon to be as national security in the wake of the 9/11 terrorist attacks and the Katrina disaster. It is necessary to build a knowledge infrastructure to train disaster response experts in public health area and to have health competence to cope with disasters.

• The KSFM Journal of Fluid Machinery
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• v.7 no.6 s.27
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• pp.15-20
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• 2004

Numerical analysis of the partial admission turbine in the KARI turbopump has been performed. Flow field of the partial admission turbine is intrinsically unsteady and three dimensional. To avoid heavy computational efforts, the frozen rotor method is adopted in computation and compared with the mixing plane approach. The frozen rotor method can represent the variation of a flow field along the circumferential direction of rotor blades, which have the different relative positions to the nozzle with one another. It also illustrates the wake loss mechanism starting from the lip of a nozzle, which is not captured in the mixing plane method. The frozen rotor method has proven to be an efficient tool for the design of a partial admission turbine.

• Journal of the Korean Solar Energy Society
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• v.24 no.3
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• pp.1-7
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• 2004

Using WAsP, which is PC-program for the vertical and horizontal extrapolation of wind data, annual energy production as well as wind energy density has been predicted for Haengwon wind farm in Jeju island. The predicted results were compared with real data derived from wind turbines in Haengwon wind farm. As the results, in order to produce more electric power, new wind turbines should be located along coastal line, which has comparatively high wind energy density. Also, the roughness length should be inputted to the Map Editor program for better agreement with real annual energy production.

• International Journal of Naval Architecture and Ocean Engineering
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• v.1 no.1
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• pp.29-38
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• 2009

A ship's screw-propeller produces thrust by rotation and, at the same time, generates rotational flow behind the propeller. This rotational flow has no contribution to the generation of thrust, but instead produces energy loss. By recovering part of the lost energy in the rotational flow, therefore, it is possible to improve the propulsion efficiency. The contra-rotating propeller (CRP) system is the representing example of such devices. Unfortunately, however, neither a design method nor a full-scale performance prediction procedure for the CRP system has been well established yet. The authors have long performed studies on the CRP system, and some of the results from the authors' studies shall be presented and discussed.

• Journal of the Korean Society of Visualization
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• v.21 no.2
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• pp.91-101
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• 2023

In this study, we investigated how the performance of a Venturi changes when a hemispherical bump is applied to the divergent part of the Venturi tube and what causes the performance difference. The Venturi-tunnel experiment was conducted in the Reynolds number range of 0.2 × 10⁵ - 1.2 × 10⁵ and cavitation number range of 0.9 - 10. The bump was found to reduce the pressure loss coefficient and increase the discharge coefficient by shortening the cavitation length. The decrease in the cavitation length by the bump was explained by the strengthening of the re-entrant jet. The wake generated from the hemispherical bump seems to increase the adverse pressure gradient on the Venturi surface, thereby strengthening the re-entrant jet.