• The Journal of Natural Sciences
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• v.16 no.1
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• pp.31-37
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• 2005

We have developed an algorithm to determine the position from the image points in a lensmeter with 6-sided prism lens. The positions of the image points which are formed by six prisms depends on the decenter position of a test lens and can be calculated by skew ray tracing. The optical characteristics of the lens meter was analyzed using the Code V program and the positions of the image points was expressed as a function of the decenter position of the test lens. By minimizing the expectation error, we can determine the decenter position position of a test lens from the image positions.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.49.4-50
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• 2009

We report stray light modeling and analysis results for the current and proposed next generation ocean color imagers with Sun and the target area around Korean penninsular as viewed from geostationary orbit. The imagers used in this study are GOCI of 140mm in diameter and a proposed next generation GOCI (GOCI-II) of about 300mm in diameter. First, we built complete GOCI and GOCI-II 3D optical system models with the realistic surface characteristics. These optical models were incorporated into the in-house built Intergrated Ray Tracing (IRT) algorithm, connecting the Sun, the measurement target area and the instruments via single ray tracing computation for radiative transfer and scattering. The stray light level was then estimated for possible orbital configurations for science measurement and in-orbit calibration operation. The simulation details, results and their implications are presented.

• Proceedings of the IEEK Conference
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• 2000.07b
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• pp.1092-1095
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• 2000

Computer graphics(CG) is one of the most useful tools by which we can easily understand visible/invisible natural phenomena. Namely, phenomena in the universe is attractive one because of its beauty and invisibility on the earth. For gravitational tensing phenomena, a ray tracing algorithm is proposed based on a lens-plane. In the method, position of gravitational sources is restricted. In this paper an improved visualization method is proposed, which can represent more complex situation than the previous method.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10a
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• pp.130-134
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• 2006

본 논문에서는 메타 테이블(meta table)을 이용한 광선(ray)과 삼각형(triangle)들의 교차검사를 할 수 있는 효율적인 레이트레이싱 알고리즘을 제안한다. 기존의 kd-tree 탐색은 깊이 우선 탐색을 하면서 이미 방문했던 노드들을 방문하지 않기 위해서 스택을 이용하는 방법을 택하고 있는데, 본 논문에서 제안하는 알고리즘은 스택을 사용하지 않고 읽기 전용으로만 쓰이는 메타 테이블을 둠으로써 기존의 트리 탐색 과정보다 효율적으로 트리의 리프 노드들에 접근할 수 있도록 하였다. 실험결과 제안된 레이트레이싱 알고리즘이 기존의 kd-tree의 트리 탐색보다 노드 방문을 5배 이상 적게 하였고, 이미지 렌더링 시간도 총 2배 정도 향상됨을 볼 수 있었다.

• Current Optics and Photonics
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• v.1 no.4
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• pp.336-343
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• 2017

A wide field-of-view (FOV) image contains more visual information than a conventional image. This study proposes a new type of hyperbolic mirror for wide FOV image acquisition. The proposed mirror consists of a hyperbolic cylindrical section and a bowl-shaped hyperbolic omnidirectional section. Using an imaging system with this mirror, it is possible to achieve a $213.8^{\circ}$ horizontal and a $126.94^{\circ}$ vertical maximum FOV. Parameters of each section of the mirror are designed to be continuous at the junction of the two parts, and the resultant image is seamless. The image-acquisition model is obtained using ray-tracing optics. To rectify the geometrical distortion of the original image due to the mirror, an image-restoration algorithm based on conformal projection is presented in this study. The performance of the proposed imaging system with the hyperbolic mirror and its image-restoration algorithm are verified by experiments.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.3-7
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• 2006

Development of light sources has been constantly grown for a high efficacy and long life. And, the design of luminaires has ben developed for the reflection and refraction of light mechanism. But it has been not enough to study for the refraction of light mechanism. Therefore, this study aims to study for the refraction of light mechanism to using Monte-Carlo method and Ray-tracing method. In addition, the purpose of this study is to shu calculation process for development of 3 dimensional planar prism design algorithm in orer to use the results of photometric data that is able to obtain various luminous intensity distribution.

• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.3
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• pp.329-337
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• 2024

Free-space optical communication technology enables the high-speed data transmission and excellent anti-jamming security. We conduct research on satellite-to-ground free-space optical communication links for high-speed transmission of large-capacity surveillance and reconnaissance data. Since the satellite continues to move along its orbit while the optical signal is transmitted between the satellite and the ground, the pointing angle of the beam from the ground terminal needs to be corrected by Point Ahead Angle(PAA) so that the transmitted light reaches the expected location of the satellite. In this paper, we present the algorithm for PAA estimation and control.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.2
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• pp.326-354
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• 2014

In this paper, a new green clustering algorithm is proposed to be as a first approach in the framework of an energy efficient strategy for centralized enterprise high-density WLANs. Traditionally, in order to maintain the network coverage, all the APs within the WLAN have to be powered-on. Nevertheless, the new algorithm can power-off a large proportion of APs while the coverage is maintained as its always-on counterpart. The two main components of the new approach are the faster procedure based on K-means and the more accurate procedure based on Evolutionary Algorithm (EA), respectively. The two procedures are processes in parallel for different designed requirements and there is information interaction in between. In order to implement the new algorithm, EA is applied to handle the optimization of multiple objectives. Moreover, we adapt the method for selection and recombination, and then introduce a new operator for mutation. This paper also presents simulations in scenarios modeled with ray-tracing method and FDTD technique, and the results show that about 67% to 90% of energy consumption can be saved while it is able to maintain the original network coverage during periods when few users are online or the traffic load is low.

• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2625-2634
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• 2022

Discretization errors are extremely challenging conundrums of discrete ordinates calculations for radiation transport problems with void regions. In previous work, we have presented a multi-collision source method (MCS) to overcome discretization errors, but the efficiency needs to be improved. This paper proposes a goal-oriented algorithm for the MCS method to adaptively determine the partitioning of the geometry and dynamically change the angular quadrature in remaining iterations. The importance factor based on the adjoint transport calculation obtains the response function to get a problem-dependent, goal-oriented spatial decomposition. The difference in the scalar fluxes from one high-order quadrature set to a lower one provides the error estimation as a driving force behind the dynamic quadrature. The goal-oriented algorithm allows optimizing by using ray-tracing technology or high-order quadrature sets in the first few iterations and arranging the integration order of the remaining iterations from high to low. The algorithm has been implemented in the 3D transport code ARES and was tested on the Kobayashi benchmarks. The numerical results show a reduction in computation time on these problems for the same desired level of accuracy as compared to the standard ARES code, and it has clear advantages over the traditional MCS method in solving radiation transport problems with reflective boundary conditions.

• The Journal of the Acoustical Society of Korea
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• v.22 no.1
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• pp.7-13
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• 2003

Numerous investigations have demonstrated that diffused reflection is one of the most important factors in predicting room acoustics by computer simulation. Recent studies have suggested several computational algorithms in order to account for diffused reflections in the ray tracing or beam tracing method. In this study, a computational algorithm for the calculation of diffuse sound reflections in the image method is suggested and a computer simulation system is developed based on the suggested algorithm. The methodology adopted in our computer simulation system is similar to the extended radiosity method, which is developed for the computer graphics. In a real room, sound energy is reflected in a partially diffused manner which results in four reflection combinations: diffuse-diffuse, specular-specular, diffuse-specular and specular-diffuse. In this study, higher order form factor is introduced to handle the four types of reflection combinations so that the partially diffused reflection could be modeled. In this paper, the concept of extended radiosity method is described and the approximate method of calculating higher order form factor is suggested. Finally, the effect of higher order form factors on the simulation of reverberation time is investigated.