• Wind and Structures
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• v.20 no.4
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• pp.579-607
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• 2015

A Combination Random Flow Generation (CRFG) technique for obtaining the fluctuating inflow boundary conditions for Large Eddy Simulation (LES) is proposed. The CRFG technique was developed by combining the typical RFG technique with a novel calculation of k and ${\varepsilon}$ to estimate the length- and time-scales (l, ${\tau}$) of the target fluctuating turbulence field used as the inflow boundary conditions. Through comparatively analyzing the CRFG technique and other existing numerical/experimental results, the CRFG technique was verified for the generation of turbulent wind velocity fields with prescribed turbulent statistics. Using the turbulent velocity fluctuations generated by the CRFG technique, a series of LESs were conducted to investigate the wind flow around S-, R-, L- and U-shaped building models. As the pressures of the models were also measured in wind tunnel tests, the validity of the LES, and the effectiveness of the inflow boundary generated by the CRFG techniques were evaluated through comparing the simulation results to the wind tunnel measurements. The comparison showed that the LES accurately and reliably simulates the wind-induced pressure distributions on the building surfaces, which indirectly validates the CRFG technique in generating realistic fluctuating wind velocities for use in the LES. In addition to the pressure distribution, the LES results were investigated in terms of wind velocity profiles around the building models to reveal the wind flow dynamics around bluff bodies. The LES results quantitatively showed the decay of the bluff body influence when the flow moves away from the building model.

• Journal of Magnetics
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• v.22 no.1
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• pp.55-59
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• 2017

The purpose of this study was to quantitatively evaluate image quality using intensity profile, coefficient of variation (COV), and peak signal to noise ratio (PSNR) with respect to noise reduction techniques in the ultrasound images. For that purpose, we compared with the median filter, Rudin-Osher-Fatemi (ROF), Anscombe and proposed patch group prior based denoising (PGPD) techniques. To evaluate image quality, the Shepp-Logan phantom and the ultrasound image were acquired using simulation and experiment, respectively. According to the results, the difference of intensity profile using PGPD technique is lowest compared with original Shepp-Logan phantom. In simulation, the measured COV was 0.249, 0.198, 0.198, 0.177, and 0.080 using noisy, median, ROF, Anscombe and PGPD technique, respectively. Also, in experimental image, the measured COV was 0.245, 0.230, 0.231, 0.242 and 0.187 using noisy, median, ROF, Anscombe and PGPD technique, respectively. Especially, when we used PGPD technique, the PSNR has highest value in both simulation and experiment. In this study, we performed simulation and experiment study to compare various denoising techniques in the ultrasound image. We can expect the PGPD technique to improve in medical diagnosis with excellent noise reduction.

• Korean Journal of Remote Sensing
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• v.25 no.2
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• pp.107-112
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• 2009

A technique for the simulation of various kinds of ground based SAR system was developed. This is an ancillary research for the development of an ArcSAR system which uses an arc-rail as a platform for the antenna movement instead of linear rail. The results of applying conventional Deramp FFT based SAR focusing algorithm to the simulated raw signal of linear rail type ground based SAR for the point targets showed that the developed simulation technique generated accurate GB-SAR raw signal. The developed technique is now being used for the development and verification of SAR focusing algorithm for the arc-rail type ground based SAR. The simulation technique is also expected to be very useful for the purpose oriented system design and operation planning of ground based SAR technique.

• Journal of the Korea Computer Graphics Society
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• v.2 no.1
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• pp.48-60
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• 1996

This paper present a new technique for doing realistic computer animation. The method is based on forward dynamic simulation and nonlinear problem solving (parameter optimization) technique. Objects are modelled physically and simulated faithfully while satisfying kinematic and geometric constraints. This forward dynamic simulation gives us very realistic motions especially for non-voluntary motions. Then we extend simulation technique to do animation using parameter optimization. The basic idea is to add motion control over the entire animation. The motion control is finding optimal solutions while satisfying user's animation goals. We provide two different animation technique; one is for rigid body without joint actuators and the other is for rigid body with linear joint actuators. To achieve motion control, we convert single simulation to single nonliner function evaluation while either setting initial conditions as variables for the function or allocating control variables in terms of time. This method is presented with two animation examples: dice-magic and human stand-up.

• Journal of International Society for Simulation Surgery
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• v.1 no.2
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• pp.67-70
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• 2014

3-D medical image reconstruction technique using computer simulation technology has been used in the knowledge of the anatomical features and the biomechanical characteristics with the advancement of computer hardware and software. Especially, the use of 3-D image reconstruction technique in orthopaedics demonstrates that this technique is useful to improve surgical technique as well as to help inform the knowledge of shoulder joint anatomy. The purpose of this article is to introduce the utilization of 3-D image technology in shoulder surgeries.

• Journal of Electrical Engineering and Technology
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• v.6 no.3
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• pp.408-413
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• 2011

In this paper, a real-coefficient approach to Adaptive Frequency Sampling (AFS) technique is developed for efficient equivalent circuit modeling of RF components. This proposed method is advantageous than the vector fitting technique and the conventional AFS method in terms of fewer samples leading to a lower order of a rational function on a given data and to a direct conversion to an equivalent circuit for PSPICE(Personal Simulation Program with Integrated Circuit Emphsis) simulation, respectively. To validate the proposed method, the distributed equivalent circuit of a presented multi-layered RF low-pass filter is obtained using the proposed real-coefficient AFS, and then comparisons with EM simulation and circuit simulation for the device under consideration are achieved.

• Journal of the Korea Safety Management & Science
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• v.1 no.1
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• pp.207-216
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• 1999

Too many big accidents have been occurring in Korea during '90. Those were accidents of Sung-Soo Bridge in 1994 and Sam-Poong Department Store in 1995. It was confirmed that the causes of the accident were unreliable construction or building. Therefore, in this study are to use technique of virtual reality(VR) simulation in order to prevent construction accidents. To set up the VR in safety construction, Date Base of variables, VR model and expert system are needed. This system is to build expert system, to visualize of the VR system and navigation, and to find out design errors of construction. Therefore, the purpose of this was to analyze accident type of construction, and apply VR system for simulation technique.

• Journal of the Korea Society for Simulation
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• v.7 no.2
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• pp.125-136
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• 1998

To upgrade railway traffic density without any change of signal block length between stations on existing railway lines, a new signalling system of train control "the pattern control technique" is suggested. It needs very little change to computerize the cab signal using transponders. A computer simulation system is developed to experiment the new control method. The new signalling system shows much increase of the railway traffic efficiency. The train head-way time by the fixed signalling system and the new pattern control system is analyzed. The pattern control technique shows 35% increasement of trair operation under same condition of railway and trains.nd trains.

• Proceedings of the Safety Management and Science Conference
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• 1999.11a
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• pp.291-301
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• 1999

Too many big accidents have been occurring in Korea during '90. Those were accidents of Sung-Soo Bridge in 1994 and Sam-Poong Department Store in 1995. It was confirmed that the causes of the accident were unreliable construction or building. Therefore, in this study are to use technique of virtual reality(VR) simulation in order to prevent construction accidents. To set up the VR in safety construction, Date Base of variables, VR model and expert system are needed. This system is to build expert system, to visualize of the VR system and navigation, and to find out design errors of construction. Therefore, the purpose of this was to analyze accident type of construction, and apply VR system for simulation technique.

• Journal of the Korea Society for Simulation
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• v.6 no.1
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• pp.53-60
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• 1997

Results from a nonequilibrium molecular dynamics (NEMD) simulation are presented for an argon liquid subject to a shear flow. The segmented molecular dynamics method and the subtraction technique used in NEMD program to reduce the thermal fluctuation noise in data are studied with different shear rates. The standard deviation in the shear stress reduced from 0.030 to 0.004 by the segmented molecular dynamics method for 50 repeated segments. On the other hand, the standard deviation of the data remained the same when the subtraction technique was applied, where as the results of shear stress by constant value in a random way.