• Wind and Structures
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• v.7 no.1
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• pp.55-70
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• 2004

Aerostatic instability of a suspension bridge may suddenly appears when the deformed shape of the structure produces an increase in the value of the three components of displacement-dependent wind loads distributed in the structure. This paper investigates the aerostatic stability of suspension bridges using an advanced nonlinear method based on the concept of limit point instability. Particular attention is devoted to aerostatic stability analysis of symmetrical suspension bridges. A long-span symmetrical suspension bridge (Hu Men Bridge) with a main span of 888 m is chosen for analysis. It is found that the initial configuration (symmetry or asymmetry) may affect the instability configuration of structure. A finite element software for the nonlinear aerostatic stability analysis of cable-supported bridges (NASAB) is presented and discussed. The aerostatic failure mechanism of suspension bridges is also explained by tracing aerostatic instability path.

• The Journal of the Acoustical Society of Korea
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• v.1 no.1
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• pp.19-26
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• 1982

n optimization technique is adapted to determine the stage enclosure configuration preferred by performers. The merit function which quantifies the ease of ensemble among the performers is derived from a set of qualitative conditions recommended by researchers of hall acoustics. The ray path tracing technique based on the modified method of images is used to analyze acoustical characteristics at any locations of performers in stage enclosure. The gradient search technique is employed to find the geometric parameters which maximmize the merit function. As an example, optimum stage enclosure configuration of the trio chamber music is obtained using the computer program developed. The developed technique can be used in the design of concert hall stage and also in forming a special enclosure with movable reflecting surfaces.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.381-386
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• 2007

The present study is concerned with the application of Constant arc-length method that proposed by Crisfield in the investigation of the geometrically nonlinear behaviour of spatial structures composed by truss or beam element. The arc-length method can trace the full nonlinear equilibrium path of Spatial structure far beyond the critical point such as limit or bifurcation point. So, we have developed the constant arc-length method of Crisfield to analysis spatial structure. The finite element formulation is used to develop the 3d truss/beam element including the geometrical nonlinear effect. In an effort to evaluate the merits of the methods, extensive numerical studies were carried out on a number of selected structural systems. The advantages of Constant arc length method in tracing the post-buckling behavior of spatial structures, are demonstrated.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.2
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• pp.38-44
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• 2009

Recently, automobile industry expands from mechatronics area through intelligent information area, and the telematics technology is one of the greatest developing points. The telematics is utilizing the on-board-unit of vehicle's communication system, and it provides necessary information and value-added service to vehicles as well as drivers. Most of the telematics offers the solution of searching a route or generates an optimal path. This paper investigates telematics with the logistics point of view, such as freight location tracking, vehicle emergency information, etc. The telematics is a core technology of automobile industry, and it becomes new business paradigm of IP(information provider). Especially, ETA(estimated arrival time) of freight and distribution tracing information are critical issues in the logistics industry. The successful integration with telematics is introduced in the paper.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.1
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• pp.9-15
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• 2011

Highly pathogenic avian influenza could not be identified visually. It takes time to identify the symptoms by its incubation period. Without taking a quick step, the diffusion area of HPAI has dramatically increased, the extent of damage becomes bigger. In network research, the algorithm of finding the central node on the network applied to various diffusion of epidemic problems, was used in control system of tracing the diffusion path, blocking central nodes. This study tried to make the diffusion of HPAI network model for the crowded farms area, and reduce the diffusion rate to control the high-risk farms.

• Current Optics and Photonics
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• v.3 no.3
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• pp.236-242
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• 2019

An Nd:YAG slab structure was designed for a high-power zigzag slab laser amplifier based on computational simulation of the wavefront distortion. For the simulation, the temperature distribution in the slab was calculated at first by thermal analysis. Then, the optical path length (OPL) was obtained by a ray tracing method for the corresponding refractive index variation inside the slab. After that, the OPL distribution of the double-pass amplified beam was calculated by summing the results obtained for the first and second passes. The amount of wavefront distortion was finally obtained as the peak-to-valley value of the OPL distribution. As a result of this study, the length and position of the gain medium were optimized by minimizing the transverse wavefront distortion. Under the optimized conditions, the transverse wavefront distortion of the double-pass amplified beam was less than $0.2{\mu}m$ for pump power of 14 kW.

• Journal of Information Processing Systems
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• v.17 no.4
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• pp.737-753
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• 2021

As the demand for high-quality rendering for mixed reality, videogame, and simulation has increased, global illumination has been actively researched. Monte Carlo path tracing can realize global illumination and produce photorealistic scenes that include critical effects such as color bleeding, caustics, multiple light, and shadows. If the sampling rate is insufficient, however, the rendered results have a large amount of noise. The most successful approach to eliminating or reducing Monte Carlo noise uses a feature-based filter. It exploits the scene characteristics such as a position within a world coordinate and a shading normal. In general, the techniques are based on the denoised pixel or sample and are computationally expensive. However, the main challenge for all of them is to find the appropriate weights for every feature while preserving the details of the scene. In this paper, we compare the recent algorithms for removing Monte Carlo noise in terms of their performance and quality. We also describe their advantages and disadvantages. As far as we know, this study is the first in the world to compare the artificial intelligence-based denoising methods for Monte Carlo rendering.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.3
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• pp.254-263
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• 2012

The survivability of warship is assessed by susceptibility, vulnerability and recoverability. Essentially, a vulnerability assessment is a measure of the effectiveness of a warship to resist hostile weapon effects. Considering the shot line and its penetration effect on the warship, present study introduces the procedural aspects of vulnerability assessments of warship. Present study also considers the prediction of penetration damage to a target caused by the impact of projectiles. It reflects the interaction between the weapon and the target from a perspective of vulnerable area method and COVART model. The shotline and tracing calculation have been directly integrated into the vulnerability assessment method based on the penetration equation empirically obtained. A simplified geometric description of the desired target and specification of a threat type is incorporated with the penetration effect. This study describes how to expand the vulnerable area assessment method to the penetration effect. Finally, an example shows that the proposed method can provide the vulnerability parameters of the warship or its component under threat being hit through tracing the shotline path thereby enabling the vulnerability calculation. In addition, the proposed procedure enabling the calculation of the component's multi-hit vulnerability introduces a propulsion system in dealing with redundant Non-overlapping components.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.306-311
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• 2003

In this paper, we modeled the incident beam in order to analyze and evaluate the optical thin film device for wavelength division multiplexing in optical telecommunication network. As applied ray tracing method to the optical path, we were compared the accuracy of coupling efficiency simulated by two modeling methods. In the results of sinulation, ceil modeling method was preferred to annual modeling method in micro-optic device because of accuracy for coupling efficiency and Gaussian intensity distribution. In the results of optimal simulation for optical device using thin film filter, the distance (d1) between optical fiber and GRIN lens, the distance (d2) between GRIN lens and thin film filter and the coupling efficiency were 0.24 mm, 0.25 mm and -0.11 ㏈ respectively. As d2 was displaced at 0.25 mm and d1 was varied in order to evaluate the optimal value, d1 and maximum coupling efficiency were 0.24 mm and -0.35㏈, respectively. Then the results of experiment were corresponded to that of optimal simulation by cell modeling and it was possible to analyze the performance for optical device using thin film filter by the simulation.

• The Journal of the Korea Contents Association
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• v.7 no.1
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• pp.103-115
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• 2007

The vulnerability issue on IEEE 802.1x wireless LAN has been permits the malicious attack such as Auth/Deauth flooding more serious rather than we expected. Attacker can generate huge volume of malicious traffic as the same methods on existing wired network. The objective of wireless IP Traceback is to determine the real attack sources, as well as the full path taken by the wireless attack packets. Existing IP Traceback methods can be categorized as proactive or reactive tracing. But, these existing schemes did not provide enhanced performance against DoS attack on wireless traffic. In this paper, we propose a 'TTL based advanced Packet Marking' mechanism for wireless IP Packet Traceback with wireless Classification function. Proposed mechanism can detect and control DoS traffic on AP and can generate marked packet for reconstructing on the real path from the non-spoofed wireless attack source, by which we can construct secure wireless network based on AP with enhance traceback performance.