• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.361-365
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• 2002

This research is presented for optimizing the coefficients of spring and damper by impulse which is applied to AGV when the two containers are loaded on AGV. The suspension is estimated to the condition that two containers, initial velocity of container, initial height of container and maximum of suspension stroke. The coefficients of spring and damper are calculated numerically through Newmark method uses finite difference expansions. The procedure of calculation is applied by one DOFs of mass-spring-damper system. The coefficients of spring and damper have large value as increase of height or decrease of stroke. The result of calculation is shown in graph and the investigation is used AGV design.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.710-715
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• 2001

This research is presented for optimizing the coefficients of spring and damper by impact load which is applied to a trailer when the containers are loaded up trailer. The procedure utilize the condition that two containers, initial velocity of container, initial height of container and maximum of suspension stroke. The coefficients of spring and damper are calculated numerically through Newmark method uses finite difference expansions. The procedure of calculation is applied by one DOFs of mass-spring-damper system. The coefficients of spring and damper have large value as increase of height or decrease of stroke. The result of calculation is investigated and is used AGV design.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.8
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• pp.813-818
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• 2009

Design analysis and computer experiments (DACE) model is widely used to express efficiently nonlinear responses in the field of engineering design. As a DACE model, kriging model can approximately replace a simulation model that is very expensive or highly nonlinear. The kriging model is composed of the summation of a global model and a local model representing deviation from the global model. The local model is determined by correlation coefficient with the pre-sampled points, where the accuracy and robustness of the kriging model depends on the selection of proper correlation coefficients. Therefore, to achieve the robust kriging model, the range of the correlation coefficients is explored with respect to the degrees of the global model. Based on this study we propose the proper orders of the global model and range of parameters to make accurate and robust kriging model.

• Journal of Bio-Environment Control
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• v.1 no.1
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• pp.28-36
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• 1992

The wind pressure distributions were analyzed to provide fundamental criteria for the structural design on e single-span arched house according to the wind directions through the wind tunnel experiment. In order to investigate the wind force distributions, the variation of the wind force coefficients, the mean wind force coefficients, the drag force coefficients and the lift force coefficients were estimated by using the experimental data. The results obtained are as follows: 1. When the wind direction was normal to the wall, the maximum positive wind pressure along the height of the wall occurred approximately at two-thirds of the wall height because of the effects of boundary layer flow. 2. When the wind direction was 30$^{\circ}$ to the wall, the maximum positive wind force occurred at the windward edge of the wall. When the wind direction was parallel to the wall, the maximum negative wind force occurred at the windward edge of the wall. 3. The maximum negative wind force along the width of the roof appeared around the width ratio, 0.4, and that along the length of the roof appeared around the length ratio, 0.5. 4. According to the results of the mean wind force coefficients analysis, the maximum negative wind force occurred on the roof at the wind direction of 30$^{\circ}$. 5. The wind forces at the wind direction of 30$^{\circ}$ instead of 0$^{\circ}$ are recommended in the structural design of supports for a house. 6. To prevent partial damage of a house structure by wind forces, the local wind forces should be considered to the structural design of a house.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.2
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• pp.29-37
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• 1998

Linear equations of motion for submersibles are one of the rest important design parameters, which are used as a governing equation for the shape design and the controller design. But, the estimated maneuvering coefficients in equations of motion by using empirical formulae, theoretical calculations or model tests might have some errors. Therefore the maneuvering coefficients should be verified from sea trial test. In this study, parallel extended Kalman filter method, Nelder & Mead Simplex method and genetic algorithm were applied to the parameter identification of roll maneuvering coefficients based on sea trial data. As a result, it was verified that Nelder & Mead Simplex method gave the most satisfactory results for the mathmatical models and the sea trial data used in this study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.21-24
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• 2008

This study proposes a optimized shape of diffuser profile through investigating the scattering and diffusion characteristics of diffusers. The scattering coefficient according to ISO 17497-1 evaluates uniformity of reverberant sound field of late reflections, while the diffusion coefficient according to AES-4id-2001 evaluates polar response of early reflections. Thus both scattering and diffusion characteristics should contribute to design shape of diffusers to maximize physical performance. To find out design method, the previous results on hemisphere diffusers are reviewed. The frequency characteristics of scattering coefficients depended on the structural height of the diffusers, while amount of scattering coefficients depended on the surface coverage density of the diffusers. However absorptive properties also increased with augment of surface coverage density, thus optimum coverage density should be considered. For the directional diffuser, three types of 2D-diffusers are proposed; semicylinder of h=5mm, semi-truncated cone of h=5-25mm and semicylinder of h=25mm. As results, diffusers with the maximum height of 25mm show the highest scattering coefficients, while diffuser of h=5mm shows high scattering coefficients only at the high-frequency bands. Diffusion coefficient will be investigated for diffusive properties of the early reflection.

• Magazine of the Korean Society of Agricultural Engineers
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• v.35 no.4
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• pp.76-85
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• 1993

The purpose of this study was to analyze the wind force distribution on the two single-span arched plastic house depending upon the house spacing and wind direction, which may provide the fundamental criteria for the structural design. In order to specify the wind force distribution, the variation of the wind force coefficients, the mean wind force coefficients and the drag force coefficients were estimated from the wind tunnel test data. The results obtained are as follows : 1. At the wind direction of 90$^{\circ}$, there was a typical span interval at which the maximum negative pressure was occured at the edge of the inside walls. 2. In the consideration of wind loads, the wind force coefficients estimated from independent single-span arched plastic house should not be directly applied to the structural design on the double houses separated. 3. The average maximum negative wind force on the inside walls was occured at the wind direction of 90$^{\circ}$, and the variations depending on the span intervals was not significant. 4. The average maximum drag force was occured at the wind direction of 300, and the magnitude of drag force was more significant at the first house. As the distance between two houses was increased, the drag force was slightly increased for every wind direction.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.6
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• pp.635-645
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• 2014

The changes of rainfall pattern and impervious covers have increased disaster risks in urbanized areas. Impervious covers such as roads and building roofs have been dramatically increased. So, it is falling the ability safety of flood defense equipments to exist. Runoff coefficient means ratio of runoff by whole rainfall which is able to directly contribute at surface runoff during rainfall event. The application of accurate runoff coefficients is very important in sewer pipelines design. This study has been performed to estimate runoff characteristics change which are applicable to the process of sewer pipelines design or various public facilities design. It has used the SHER model, a long-term runoff model, to analyze the impact of a rising impervious covers on runoff coefficient change. It thus analyzed the long-term runoff to analyze rainfall basins extraction. Consequently, it was found that impervious surfaces could be a important factor for urban flood control. We could suggest the application of accurate runoff coefficients in accordance to the land Impervious covers. The average increase rates of runoff coefficients increased 0.011 for 1% increase of impervious covers. By having the application of the results, we could improve plans for facilities design.

• Journal of the Korean Solar Energy Society
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• v.33 no.1
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• pp.40-47
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• 2013

An aerodynamic design tool was developed for small wind turbine blades based on the blade element momentum theory. The lift and drag coefficients of blades that are needed for aerodynamic blade design were obtained in real time from the Xfoil program developed at University of Illinois. While running, the developed tool automatically accesses the Xfoil program, runs it with proper aerodynamic and airfoil properties, and finally obtains lift and drag coefficients. The obtained aerodynamic coefficients are then used to find out optimal twist angles and chord lengths of the airfoils. The developed tool was used to design a wind turbine blade using low Reynolds number airfoils, SG6040 and SG6043 to have its maximum power coefficient at a specified tip speed ratio. The performance of the blade was verified by a commercial code well known for its prediction accuracies.

• Wind and Structures
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• v.32 no.5
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• pp.439-452
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• 2021

The concept of Performance objective assessment is extended to wind engineering. This approach applies using the Database-Assisted Design technique, relying on the aerodynamic database provided by the National Institute of Standards and Technology (NIST). A structural model of a low-rise building is analyzed to obtain influence coefficients for internal forces and displacements. Combining these coefficients with time histories of pressure coefficients on the envelope produces time histories of load effects on the structure, for example knee and ridge bending moments, and eave lateral drift. The peak values of such effects are represented by an extreme-value Type I Distribution, which allows the estimation of the gust wind speed leading to the mean hourly extreme loading that cause specific performance objective compromises. Firstly a fully correlated wind field over large tributary areas is assumed and then relaxed to utilize the denser pressure tap data available but with considerably more computational effort. The performance objectives are determined in accordance with the limit state load combinations given in the ASCE 7-16 provisions, particularly the Load and Resistance Factor Design (LRFD) method. The procedure is then repeated for several wind directions and different dominant opening scenarios to determine the cases that produce performance objective criteria. Comparisons with two approaches in ASCE 7 are made.