• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.2
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• pp.211-217
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• 2010

This paper introduces the Hull Mounted Sonar Vertical Scanning(HMS Verscan) technique to overcome the limitation of target detection in short range shadow zone. Numerical experiments were done with the HMS Verscan taking advantage of the vertical beamforming technique for two-dimension hydrospace(range-depth). For numerical experiments, ray model and high-frequency monostatic reverberation model were used. HMS Verscan increased a sound pressure level at the short range shadow zone through reflections at the sea surface and seafloor. Inclusion of the boundary scattering improved target detection due to the sound reflected into the shadow zone.

• The KSFM Journal of Fluid Machinery
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• v.8 no.2 s.29
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• pp.9-15
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• 2005

This paper presents an experimental and numerical study on the overall performance and local flow characteristics of sirocco fan in a range hood. Measurement of overall performance for sirocco fans were conducted based on AMCA standard 210. The effects of flow blockages due to the motor inside the fan on the fan performance were investigated by experimentally and numerically and the results were compared with each other. The numerical and experimental results show the inlet flow blockage reduces the performance (ie. fan static pressure, design flow rate, maximum efficiency and free delivery flow rate) of fan. It is found that the blockage makes the flow field highly non-uniform through the blade and cause the efficiency decrement.

• Journal of Ocean Engineering and Technology
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• v.18 no.1
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• pp.1-6
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• 2004

In this paper, the performance of a wave absorbing system using an inclined punching plate, was investigated. Using the multi-domain boundary element method (BEM), the reflection coefficients of an inclined punching plate were tested with various design parameters, such as inclined angle, porosity, and wave frequencies. To confirm the numerical solutions, the systematic model test was conducted at 2-D tank and square tank. The numerical results were in good agreement with the experimental results within the entire frequency range. It was found that an inclined punching plate had an excellent wave absorbing efficiency, compared to a horizontal one. Also, the optimal range of an inclined angle had an excellent wave absorbing efficiency, compared to a horizontal one the optimal range of the inclined angle is 10°<β<20°. The developed wave absorber was installed at KRISO's square basin, and is working effectively for various model tests.

• Ocean Systems Engineering
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• v.8 no.1
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• pp.33-39
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• 2018

The paper presents a numerical underwater channel model developed in MATLAB for estimating the optical link budget between a light emitting diode (LED) based optical transmitter and a photo diode (PD) receiver when operated in the harbor, coastal and deep waters locations in the Bay of Bengal. The water samples are collected at different locations in the Bay of Bengal using a water sampler during an offshore research cruise. The optical attenuation, the main inherent parameter determining the range of the optical communication link is identified for the different waters using an underwater irradiance measurement system in the laboratory. The identified parameters are applied to the numerical model and found that a 10 W LED and a photo diode based system can provide the optical budget required for a horizontal underwater communication range of about 0.5, 14 and 35 m in the harbor, coastal and deep waters locations respectively. By increasing the transmitter power to 50 W, the operating range of the communication link could be increased up to 53 m in deep water locations in the Bay of Bengal.

• Journal of the Korean Statistical Society
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• v.12 no.2
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• pp.69-80
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• 1983

The purpose of this paper is to obtain representation of the mathematical special functions and the numerical values of the mean square errors for the quasi-ranges in random small smaples ($n \leq 30$) from the Weibull distribution with a shape and a scale parameters, and to estimate the scale parameter by use of unbiased estimator based on the quasi-range. It will be shown that the jackknife estimator of the range is worse than the range of random samples from the given distribution in the sense of the mean square error.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.4
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• pp.321-327
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• 2007

In an apartment house that is generally air-tight and well insulated, the combustion gas from cooking devices is the major source of air pollution in the kitchen. It spreads throughout the house affecting the overall Indoor all quality. In this study, the performance of the kitchen range hood which employs air induction and air curtain was investigated by numerical simulation. The results are compared with that of two other kitchen range hoods which are in general use. The two general types of range hoods considered in the present calculations are box and plate type range hoods. The former has a large capture space between the filter and suction duct, while the latter has little. It was found that the capture efficiency of the kitchen range hood with air induction and air curtain Is higher than that of the general types of range hoods by 20% approximately The reason may be because the air induction and the air curtain block the air stream escaping from the front and the side part of range hoods effectively and because an additional fan for air induction and air curtain increases suction flow rates.

• International Journal of Fluid Machinery and Systems
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• v.10 no.2
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• pp.176-188
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• 2017

The nozzle-flapper valves are widely applied as a pilot stage in aerospace and military system. A subject of the analysis presented in this work is to find out a reasonable range of null clearance between the nozzle and flapper. This paper has presented a numerical flow coefficient simulation. In every design point, a parameterized model is created for flow coefficient simulation and cavitation under different conditions with varying gap width and inlet pressure. Moreover, a new test device has been designed to measure the flow coefficient and for visualized cavitation. The numerical simulation and test results both indicate that cavitation intensity gets fierce initially and shrinks finally as the gap width varies from small to large. From the curve, the flow coefficient mostly has experienced three stages: linear throttle section, transition section and saturation section. The appropriate deflection of flapper is recommended to make the gap width drop into the linear throttle section. The flapper-nozzle null clearance is optionally recommended near the range of $D_N/16$. Finally through simulation it is also concluded that the inlet pressure plays a little role in the influence on the flow coefficient.

• Korean Journal of Cognitive Science
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• v.20 no.3
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• pp.335-355
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• 2009

We examined risk judgment and the accuracy of inference based on two kinds of probabilities in a Bayesian inference task: the death probability from a disease (base rates) and the probability of having a disease with positive results in the screening test (posterior probabilities). Risk information were presented in either a probability or a frequency format. In Study 1, we found a numerical format effect for both base rate and posterior probability. Participants rated information as riskier and inferred more accurately in the frequency condition than in the probability condition for both base rate and posterior probability. However, there was no frequency range effect, which suggested that the ranges of frequency format did not influence risk ratings. In order to find out how the analytic thought system influences risk ratings, we compared the ratings of a computation condition and those of a no-computation condition and still found the numerical format effect in computation condition. In Study 2, we examined the numerical format effect and frequency range effect in a high and a low probability condition and found the numerical format effect at each probability level. This result suggests that people feel riskier in the frequency format than in the probability format regardless of the base rates and the posterior probability. We also found a frequency range effect only for the low base rate condition. Our results were discussed in terms of the dual process theories.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.365-368
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• 2004

We present a family of elaborate numerical models for simulation and systematic optimization of complex LCDs for demanding applications (e.g. LCD-TV). These numerical models comprise modules for solving LCD-related problems in one, two and three dimensions. The three modules feature an intuitive graphical user surface for a jump-start into modeling, a common database for a range of materials and components as well as sophisticated and proven algorithms with more than 15 years of reliable performance in the LCD-industry. Methods for obtaining data required for the modeling of key components are presented.

• Journal of Environmental Science International
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• v.9 no.5
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• pp.397-402
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• 2000

Numerical simulation model using nesting method and considering topographic features was developed to predict atmospheric environments atmospheric flow temperature and diffusion of air pollutants in Kwangyang bay where having complex areas of point sources Korea. In addition developed simulation model was used tracing of spreading range of pollutants when a gas leaks suddenly from Yeo-cheon industrial complex. by comparing the measured and calculated data on atmospheric flow temperature and diffusion of air pollutants the results showed that this model can be well applied and complicated topography affected the diffusion of air pollutants.