• Journal of the Optical Society of Korea
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• v.14 no.1
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• pp.42-48
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• 2010

We used video-rate Confocal Laser Scanning Microscopy (CLSM) to observe the motion of blood cells in a micro-channel. Video-rate CLSM allowed us to acquire images at the rate of 30 frames per second. The acquired images were used to perform Particle Image Velocimetry (PIV), thus providing the velocity profile of the blood in a micro-channel. While previous confocal microscopy-assisted PIV required exogenous micro/nano particles as the tracing particles, we employed blood cells as tracing particles for the CLSM in the reflection mode, which uses light back-scattered from the sample. The blood flow at various depths of the micro-channel was observed by adjusting the image plane of the microscope. The velocity profile at different depths of the channel was measured. The confocal micro-PIV technique used in the study was able to measure blood velocity up to a few hundreds ${\mu}m/sec$, equivalent to the blood velocity in the capillaries of a live animal. It is expected that the technique presented can be applied for in vivo blood flow measurement in the capillaries of live animals.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.53-56
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• 2003

For identifying how a sample knit fabric is woven a method to obtain positional information of each yarn of the sample from voxel data made out of its x-ray CT images is newly proposed in this paper. The positional information is obtained by tracing the each yarn. The each yarn is traced by estimating a direction of the yarn in a certain small region in which the yarn can be regarded as straight and moving the region slightly along the estimated direction alternately. The yarn direction is estimated by correlating the voxel data in the region with a three-dimensional yarn model. The effectiveness of this method is confirmed by applying the method to voxel data made out of CT images of a knit fabric experimentally.

• The Journal of the Acoustical Society of Korea
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• v.14 no.3
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• pp.82-89
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• 1995

A sound field simulator is constructed to obtain the sound field paramaters such as the magnitudes and directions of early reflections with moderate efforts. The proposed simulator is based on the hybrid ray tracing method that traces rays reached the listener position and convert them to image sound sources. By this approach, we can obtain the directional impulse response relatively easily with minimum casts. Simulation experiment results of several performace places are reported to how the versatility of the proposed simulator system.

• Current Optics and Photonics
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• v.4 no.1
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• pp.23-30
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• 2020

This paper presents a new method for designing a lens system stable against chromatic variation at a specified wavelength. Conventional lenses are corrected for chromatic aberration, but the new method suppresses chromatic changes of the marginal ray in the image-side. By doing so, paraxial properties of the lens system are stabilized against chromatic variation. Since the new method is based on paraxial ray tracing, the stabilizing conditions against chromatic variation are given by recurrence formulas. However, there is an analytic solution for the case of a cemented doublet in the air. A stable doublet at 405 nm wavelength is designed and analyzed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1444-1449
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• 2000

This environmental influence of the noise produced by a number of air-conditioner out-door units in a multi-unit housing is predicted and evaluated. The method based on Ray tracing theory and mirror image source theory is utilized. Each ventilation window in a machine room is considered as a sound source which contributes to the overall noise level of the surrounding environment. The adopted method has been found a very efficient tool to assess the environmental noise impact.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.15 no.2
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• pp.215-219
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• 1997

It is very difficult to conduct a tracing survey of a forest fire because the affected area is huge and the topology of the mountain defies access of investigators. As a result, remote sensing technique is used to get consecutive information about the range and ecological change of the affected area. Therefore, this study investigates the change of activity condition of vegetation by getting vegetation index, hinted by the fact that activities of plants decline after the fire.

• ETRI Journal
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• v.28 no.2
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• pp.247-249
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• 2006

In the development of a new wireless communications system, a versatile and accurate radio channel for indoor communications is needed. In particular, the investigation of radio transmission into buildings is very important. In this letter, we present an improved three-dimensional electromagnetic wave propagation prediction model for indoor wireless communications that takes into consideration building penetration loss. A ray tracing technique based on an image method is also employed in this study. Three-dimensional models can predict any complex indoor environment composed of arbitrarily shaped walls. A speed-up algorithm, which is a modified deterministic ray tube method, is also introduced for efficient prediction and computation.

• Journal of Korea Multimedia Society
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• v.22 no.2
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• pp.311-321
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• 2019

Virtual reality applications in Head-Mounted Displays require high frame rates and low latency rendering techniques. Ray tracing offers many benefits, such as high-quality image generation, but has not been utilized due to lower performance than rasterization. But that can obtain good result combined with gaze-tracking technology and human visual system's operation principle. In this paper, we propose a method to optimize the foveated sampling map and to maintain the visual quality through the fast voronoi nearest interpolation. The proposed method further reduces the computational cost that has been improved by the previous foveated sampling. It also smoothes the voronoi boundary using adaptive sibson interpolation, which was not possible in real-time. As a result, the proposed method can render real-time high-quality images with low visual difference.

• Journal of the Korea Computer Graphics Society
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• v.2 no.1
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• pp.24-30
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• 1996

The ray tracing method, which is one of many photorealistic rendering techniques, requires heavy computational processing to synthesize images. Parallel processing can be used to reduce the computational processing time. A parallel algorithm for the ray tracing has been implemented and executed for various images on transputer systems. In order to develop a scalable parallel algorithm, a processor farming technique has been exploited. Since each image is divided and distributed to each farming processor, the scalability of the parallel system and load balancing are achieved naturally in the proposed algorithm. Efficiency of the parallel algorithm is obtained up to 95% for nine processors. However, the best size of a distributed task is much higher in simple images due to less computational requirement for every pixel. Efficiency degradation is observed for large granularity tasks because of load unbalancing caused by the large task. Overall, transputer systems behave as good scalable parallel processing system with respect to the cost-performance ratio.

• The Transactions of the Korea Information Processing Society
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• v.4 no.2
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• pp.596-605
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• 1997

The synamic systrm emplohing the self-squared function, , $f(Z)=z^2+c$, provides the Mandelbrot set which classifies constants c using the divergence of the sequence starting from the origin.To speed-up the generation of Mandelbrot set images, two approaches , called as the divide-and-conquer technique and the triangular boundary tracing technique, have been developed.However , the divede-and-conquer technique genrates sequences of some pixels that so not affect graphical representations of the Mandelbrot set.The triangular boundary tracing tech-mique does noot represent some 8-connected components of the Mandelbrost set.In this paper, we prorose a new ;method which solves the 8-connectivity problem of triangular boundary tracing technique.This algorithm considers the divergence for only pixels which are essential to the graphical repressentation of the Mandelbrot set.It also foves good representations for 8-connected components like hairly structures.