• Journal of the Korea Computer Graphics Society
• /
• v.21 no.5
• /
• pp.11-19
• /
• 2015

Our research introduces a novel system for creating 3D vehicle animation. Our system is for intuitively authoring vehicle accident scenes according to videos or based on user-drawn trajectories. Our system has been implemented by combining three existing ideas. The first part is for obtaining 3D trajectory of a vehicle from black-box videos. The second part is a tracking algorithm that controls a vehicle to follow a given trajectory with small errors. The last part optimizes the vehicle control parameters so that the error between the input trajectory and simulated vehicle trajectory is minimized. We also simulate the deformation of the car due to an impact to achieve believable results in real-time.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.41 no.2
• /
• pp.145-152
• /
• 2017

Mixing of molecular grains having different characteristics is very important in many industries such as the food and pharmaceutical industries. With the development of computer simulations, it is common practice to find the optimal mixing conditions through a simulation before the actual mixing task to estimate the proper level of mixing. Accordingly, there has been an increasing need for a mixing index to measure the mix of particles in the simulation process. Mixing indices, which have been widely used so far, can largely be classified into two types: first is the statistical-based mixing index, which is prepared using the sampling method, and the second is the mixing index that is prepared using all the particles. In this paper, we calculated mixing indices in different ways for the data in the course of mixing the particles using the DEM simulation. Additionally, we compared the performance, advantages, and disadvantages of each mixing index. Therefore, I propose a standard that can be used to select an appropriate mixing index.

• Journal of Navigation and Port Research
• /
• v.41 no.4
• /
• pp.173-180
• /
• 2017

Underwater communications are degraded as a result of inter symbol interference in multipath channels. Therefore, a channel coding scheme is essential for underwater communications. Packets consist of a PN sequence and a data field, and the uncoded PN sequence is used to estimate the frequency and phase offset using a Doppler and phase estimation algorithm. The estimated frequency and phase offset are fed to a coded data field to compensate for the Doppler and phase offset. The PN sequence is generally utilized to acquire the synchronization information, and the bit error rate of an uncoded PN sequence predicts the performance of the coded data field. To ensure few errors, we resort to powerful BCJR decoding algorithms of convolutional codes with rates of 1/2, 2/3, and 3/4. We use this powerful channel coding algorithm to present an efficient receiver structure based on the relation between the bit error of the uncoded PN sequence and coded data field in computer simulations and lake experiments.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.7
• /
• pp.1713-1720
• /
• 2014

RFID technology has evolved from basic operation like the acquisition of tag IDs into a more complicated operation such as the simultaneous acquisition of tag IDs and their positions and recently, is raising the possibility of obtaining additional informations, which include their velocities, directions and distances. In this paper, we present a RFID system that can fullfil aforementioned advanced functions. In the proposed system, a tag transmits a sequence of FMCW pulses modulated by ID signals and a reader separates the tag signals in azimuth direction using an array antenna, followed by the FMCW demodulation from which distances, velocities as well as the tag IDs are extracted. We propose a receiver structure of the reader and theoretically analyze its operability. Moreover, its performance is examined by simulation.

• Journal of the Korea Computer Graphics Society
• /
• v.24 no.3
• /
• pp.73-81
• /
• 2018

In this paper, we present a motion-driven rowing simulation framework that allows multiple players to row a boat together by their harmonized movements. In the actual rowing game, it is crucial for the players to synchronize their rowing with respect to time and pose so as to accelerate the boat. Inspired by this interesting feature, we measure the motion similarity among multiple players in real time while they are doing rowing motions and use it to control the velocity of the boat in a virtual environment. We also employ game components such as catching an item which can accelerate or decelerate the boat depending on its type for a moment once it has been obtained by synchronized catching behaviors of the players. By these components, the players can be encouraged to more actively participate in the training for a good teamwork to produce harmonized rowing movements Our methods for the motion recognition for rowing and item catch require the tracking data only for the head and the both hands and are fast enough to facilitate the real-time performance. In order to enhance immersiveness of the virtual environment, we project the rowing simulation result on a wide curved screen.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.9A
• /
• pp.758-766
• /
• 2011

Cooperative communications are adopted as a promising solution to achieve high data rate over large areas in the future 40 wireless system and the relay station (RS) is the key concept in cooperative communications. However, most existing works in this area focus only on optimal RS selections. In addition, there are only few works consider another crucial issue: how many relay stations we need to place. Only when the number of relay stations is defined, the relay station selection can be performed well. In this paper we derive a formula which describes the impact of varying number of RS on end-to-end link throughput assuming a clustering scheme which is based on Voronoi tessellation. In addition to mathematical analysis on the feasibility of the formula, we also examine its performance through a set of simulations under the Erceg path loss model. Simulation results verify that the link throughput gain of our proposed scheme is promising.

• Bulletin of the Korean Space Science Society
• /
• 2010.04a
• /
• pp.35.3-35.3
• /
• 2010

항공용 지역위성항법 보강시스템(Ground Based Augmentation System, GBAS)은 지상에서 위성항법시스템에 대한 위치보정정보와 무결성 정보를 생성 및 제공하여 공항 주변 항공기의 정밀 이착륙을 돕는 지상기반의 시스템이다. 이 시스템은 기본적으로 위성항법신호를 사용하기 때문에 전리층 영향을 받게 되는데 특히 전리층 폭풍(Ionospheric storm)의 경우 공간적으로 급격한 위치오차 차이를 발생시키기 때문에 안정적인 항공기의 정밀이착륙을 위해서는 전리층 폭풍의 영향을 최소화 하는 것이 중요하다. 이를 위하여 현재 항공용 지역위성항법 보강시스템의 지상시스템(Ground Facility)과 항공기 탑재시스템에서의 전리층 폭풍에 대한 정확한 감시와 전리층 폭풍의 지배적 영향을 받는 위상항법신호를 제거하거나 보완하는 방식 등 전리층 폭풍의 영향을 최소화하기 위한 기법들이 계속해서 연구 중이다. 이 논문에서는 2001년과 2003년 미국에서 발생한 전리층 폭풍에 대한 위성항법데이터 분석 결과와 기존의 연구결과를 기반으로 전리층 폭풍에 대한 모델링과 지상시스템과 항공기 간의 공간적 상이현상(Spacial decorrelation)을 고려하여 전리층 폭풍이 항공기 이착륙에 미치는 영향에 대한 분석 결과를 제시한다. 전리층 폭풍에 대한 수학적 모델링을 하기 위해서는 전리층 폭풍의 물리적 특성에 대한 이해와 전리층 폭풍 발생 시 획득한 위성항법 데이터를 이용한 통계학적 분석이 선행되며 이러한 분석결과와 항공기 이착륙에 절차를 반영하여 항공기에 미치는 영향 분석을 위한 수학적 모델을 완성하였다. 완성된 모델을 국내 공항에서 실제 비행시험을 통하여 획득한 위성항법데이터에 적용하여 전리층 폭풍이 국내 공항에서 항공기 이착륙에 어떠한 영향을 미치는지를 분석하였다. 또한, 대표적 전리층 폭풍 감지기법 중 하나인 Code-Carrier Divergence Test 알고리즘을 적용한 결과도 함께 제시하였다. 이 논문의 결과는 항공용 지역위성항법 보강시스템에 대한 전리층 폭풍의 영향을 최소화하기 위한 기법 연구의 기반이 되며 시스템의 성능평가를 위한 다양한 시뮬레이션환경의 하나로서도 활용이 가능할 것이다.

• Journal of the Korea Society for Simulation
• /
• v.27 no.2
• /
• pp.49-59
• /
• 2018

The simulation-based weapon system effectiveness analysis is to support the decision making in the acquisition process of the defense domain. The effectiveness of the weapon system is a complexly influenced indicator from various factors such as environment, doctrine and so on. And the measurement of effectiveness can be defined differently in compliance with major issues in the weapon system. Because of this, the weapon system effectiveness analysis requires the comparative experiment of various alternatives based on the underlying assumption. This paper presents the efficient approach to reconfigure the simulation using the reflection technique. The proposed method contains the recoupling and resetting the simulation entity using DEVS(Discrete EVent System specification) formalism-based dynamic plug-in method. With the proposed method, this paper designs the effectiveness analysis environment that can efficiently handle the various alternatives of the weapon system.

• Progress in Medical Physics
• /
• v.23 no.1
• /
• pp.42-47
• /
• 2012

In this paper, Acousto-Optical tomography is modeled by a linear integral equation and an inverse problem involving a diffusion equation in n-spatial dimensions. We make two-step mathematical model. First, we solve a linear integral equation. Assuming the optical energy fluence rate has been recovered from the previous equation, the absorption coefficient ${\mu}$ is then reconstructed by solving an inverse problem. Numerical experiments are presented for the case n=2. The traditional gradient descent method is used for the numerical simulations. The result of the gradient descent method produces the blurring effect. To get rid of the blurring effect, we suggest the total variation regularization for the minimization problem.

• Journal of the Korea Society for Simulation
• /
• v.26 no.3
• /
• pp.73-86
• /
• 2017

Environmental data plays an important role to enhance the reliability of experimental results in M&S(Modeling and Simulation). Especially in Military M&S, extreme weather events can be used for virtual training and simulation importantly. However, the environmental data is huge and it is dispersed among multiple organizations. It is difficult for M&S operators to select the date and area where the weather phenomenon occurs in the real environmental data and to acquire them. Environmental data retrieval technology based on Fuzzy criteria is one of the important technologies for developing Environmental Scenario Generator. As a result of this study, a fuzzy retrieval algorithm composed of four main parameters(RV, MF, FRA, and MRV) was presented. This study suggests that the RV can be used as 14 m/s for wind speed and 80 mm/d for precipitation to search the date of storm accompanied by high wind. The MF, the FRA, and MRV can be used sigmoid, 0.2, and 1 respectively. The algorithm proposed in this study is expected to be very useful for searching the date on which weather phenomena necessary for simulation occurred.