• Journal of KIISE:Computer Systems and Theory
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• v.31 no.3_4
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• pp.247-256
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• 2004

This paper presents an efficient collision detection algorithm the performance of which is independent of animation speed. Most of the previous collision detection algorithms are incremental and discrete methods, which find out the neighborhood of the extreme vertex at the previous time instance in order to get an extreme vertex at each time instance. However, if an object collides with another one with a high torque, then the angular speed becomes faster. Hence, the candidate by the incremental algorithms may be farther from the real extreme vertex at this time instance. Therefore, the worst time complexity nay be $O(n^2)$, where n is the number of faces. Moreover, the total time complexity of incremental algorithms is dependent on the time step size of animation because a smaller time step yields more frequent evaluation of Euclidean distance. In this paper, we propose a new method to overcome these drawbacks. We construct a spherical extreme vertex diagram on Gauss Sphere, which has geometric properties, and then generate the distance function of a polyhedron and a plane by using this diagram. In order to efficiently compute the exact collision time, we apply the interval Newton method to the distance function.

• The Journal of the Korea Contents Association
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• v.11 no.4
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• pp.92-100
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• 2011

In this paper, we propose a novel blind digital watermarking method based on a cellular automata transform (CAT). CAT is based on dynamic systems known as cellular automata(CA) and uses transform bases which are differently defined by a rule number, the number of neighbors, the number of cells, and an initial state, etc. The proposed CAT based method is compared with a blind watermarking method based on DWT which is commonly used for a domain transform in signal processing. We analyse properties on changes of DWT coefficients and CAT coefficients under various attacks and determine optimal parameters for a watermarking method robust to attacks. The simulations show that the watermarked images with high PSNR and MSSIM look visually identical to originals and are robust against most of typical image processing attacks. Moreover, the proposed CAT based watermarking method is superior to the DWT based one in robustness to most of typical image processing attacks including JPEG compression, median and average filtering, scaling, cropping, and histogram equalization.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.5
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• pp.321-328
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• 2017

In this study, vortex tube system model is developed to predict the temperature of the hot and the cold sides. The vortex tube model is developed based on the system identification method, and the model utilized in this work to design the vortex tube is ARX type (Auto-Regressive with eXtra inputs). The derived polynomial model is validated against experimental data to verify the overall model accuracy. It is also shown that the derived model passes the stability test. It is confirmed that the derived model closely mimics the physical behavior of the vortex tube from both the static and dynamic numerical experiments by changing the angles of the low-temperature side throttle valve, clearly showing temperature separation. These results imply that the system identification based modeling can be a promising approach for the prediction of complex physical systems, including the vortex tube.

• Journal of Korean Society of Transportation
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• v.33 no.2
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• pp.204-213
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• 2015

The congestion of pedestrians impedes the utilization efficiency of a subway station. Conflicts among pedestrians due to unseparated pedestrian flows not only increase the impedance of pedestrian mobility but also negatively affect on pedestrian safety. This paper analyzes the travel characteristics of bi-directional pedestrian flow based on microscopic movements, and evaluates the operation efficiency on separating the traffic line. The subway station was simulated in a 2-D grid structure by applying Discrete Element Method, and the movement is organized in each cell of the grid. As a result, the model explicates that separating the traffic line and encouraging the 'Keep right rule' would be mostly effective for the conflicting flows. Therefore, applying the 'Walking Guidance System' would be efficient to improve the pedestrian convenience and mobility.

• The Journal of the Korea Contents Association
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• v.17 no.3
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• pp.589-595
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• 2017

We present an estimation model for optimal channel capacity required to data traffic transmission. The optimal channel capacity should be calculated in order to satisfy the permitted transmission delay of each wireless data services. Considering the discrete-time operation of digital communication systems and batch arrival of packet-switched traffic for various wireless services, $Geo^x$/G/1 non-preemptive priority queueing model is analyzed. Based on the heuristic interpretation of the mean waiting time, the mean waiting times of various data packets which have the service priority. Using the mean waiting times of service classes, we propose the procedure of determining the optimal channel capacity to satisfy the quality of service requirement of the mean delay of wireless services. We look forward to applying our results to improvement in wireless data services and economic operation of the network facilities.

• Journal of the Korean Society of Safety
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• v.27 no.5
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• pp.64-69
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• 2012

The concept of SIL is applied in the most of all standards relating to functional system safety. However there are problems for the people to apply SIL to their plants. as these standards don't include sufficient informations. In this regards, this paper will suggest the direction of SIL application and concept based on IEC 61508 and IEC 61511. A Safety Integrity Level(SIL) is the discrete level(one out of possible fours), corresponding to a range of the probability of an E/E/PE (Electric/Electrical/Programmable Electrical) safety-related system satisfactorily performing the specific safety functions under all the stated conditions within a stated period of time. SIL can be divided into the target SIL(or required SIL) and the result SIL. The target SIL is determined by the risk analysis at the analysis phase of safety lifecycle and the result SIL is calculated during SIL verification at the realization phase of safety lifecycle. The target SIL is determined by the risk analysis like LOPA(Layer Of Protection Analysis), Risk Graph, Risk Matrix and the result SIL is calculated by HFT(Hardware Fault Tolerance), SFF(Safe Failure Fraction) and PFDavg(average Probability of dangerous Failure on Demand). SIL is applied to various areas such as process safety, machinery(road vehicles, railway application, rotating equipment, etc), nuclear sector which functional safety is applied. The functional safety is the part of the overall safety relating to the EUC and the EUC control system that depends on the correct functioning of the E/E/PE safety-related systems and other risk reduction measures. SIL is applied only to the functional safety of SIS(Safety Instrumented System) in safety. EUC is the abbreviation of Equipment Under Control and is the equipment, machinery, apparatus or plant used for manufacturing, process, transportation, medical or other activities.

• Geomechanics and Engineering
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• v.12 no.4
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• pp.723-738
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• 2017

Rock is a heterogeneous material, which introduces complexity in the analysis of rock slopes, since both the existing discontinuities within the rock mass and the intact rock contribute to the degradation of strength. Rock failure is often catastrophic due to the brittle nature of the material, involving the sliding along structural planes and the fracturing of rock bridge. This paper proposes an advanced discretization method of rock mass based on block theory. An in-house software, GeoSMA-3D, has been developed to generate the discrete fracture network (DFN) model, considering both measured and artificial joints. Measured joints are obtained from the photogrammetry analysis on the excavation face. Statistical tools then facilitate to derive artificial joints within the rock mass. Key blocks are searched to provide guidance on potential reinforcement measures. The discretized blocky system is subsequently implemented into a discontinuous deformation analysis (DDA) code. Strength reduction technique is employed to analyze the stability of the slope, where the factor of safety can be obtained once excessive deformation of slope profile is observed. The combined analysis approach also provides the failure mode, which can be used to guide the choice of strengthening strategy if needed. Finally, an illustrated example is presented for the analysis of a rock slope of 20 m height inclined at $60^{\circ}$ using combined GeoSMA-3D and DDA calculation.

• Journal of Advanced Navigation Technology
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• v.20 no.3
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• pp.196-202
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• 2016

In this paper, a stationary wavelet transform method is proposed for improving the altitude control performance of quadrotor UAV using an ultrasonic rangefinder. A ground tests are conducted using an ultrasonic rangefinder that is much used for vertical takeoff and landing. An ultrasonic rangefinder suffers from signal's spike due to specular reflectance and acoustic noise. The occurred spikes in short time span need to be analyzed at both sides time and frequency domain. It was known that stationary wavelet transform is the transferring solution to the problem occurred by down sampling from DWT also more efficient to remove noise than DWT. The analyzed spikes of the ultrasonic rangefinder using a stationary wavelet transform and experimental results show that it can effectively remove the spikes of the ultrasonic rangefinder.

• The Journal of the Korea Contents Association
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• v.3 no.3
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• pp.40-46
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• 2003

In the paper, designed digital contents security module to check unlawfulness reproduction and distribution of digital contents. This paper applied Diffie-Hellman algorithm that use discrete logarithm and random number as primary for public key application to create encryption key that agree each other through communication channel between DCPS and HOST, and applied Triple DES repeat DES 3 times through 2 different encryption key that is selecting ANSI X9.17 that is key management standard, ISO 8732 and PEM(Privacy-Enhanced Mail) etc. by secondary protection for safe transmission of digital contents in transmission line. Designed security module consist of key exchange module, key derivation module and copy protection processing module. Digital contents security module that design in this thesis checks reproduction and distribution of digital contents by unauthenticated user through user certification function and digital contents encryption function, and protect digital contents transmission line.

• Journal of the Korean Professional Engineers Association
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• v.24 no.6
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• pp.106-112
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• 1991

Electronics has different meanings to different people and in different countries. Hence, let me difine the term in the sense that it is used here. Electronics in the science and the technology of the passage of charged particles in a gas, in a vacumn, or in a semiconductor. The beginning of electronics came in 1895 when H. A. Lorentz postulated the existence of discrete charges called electrons. Two years later J.J. Thompson found these electrons experimentally. In the same year (1897) Braun built what was probaly the first electron tube, essentially a primitive cathode-ray tube. It was not until the start of the 20th century that electronics began to take technological shape. In 1904 Fleming invented the diode which he called a valve. This era begins with the invention of the transistor about 30 years ago. The history of this invention is interesting. M.J. Kelly, director of research(and later president of Bell Laboratories), had the foresight to realize that the telephone system needed electronic switching and better amplifiers. Vacuum tubes were not very reliable, principally because they generated a great deal of heat even when they were not being used, and, particularly, because filaments burned out and the tubes had to be replaced. In 1945 a solid-state physics group wa formed. The foregoing completes the history of electronics and electronic industries up to 1978. There is already a start toward a merging of the computer and the communication industries which might be called information manipulation. This includes storage of information, sorting, computation, information retrieval, and transmission of data. This combination of the computer and the communication fields will penetrate many disciplines. Applications will be made in the fields of law, medicine, biological sciences, engineering, library services publishing banking, reservation systems, management control, education, and defense.