• Transactions of the Society of Information Storage Systems
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• v.1 no.1
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• pp.42-47
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• 2005

We developed an optical pickup system which is used fer Blu-ray Disc. A liquid crystal element was used to make compensation for spherical aberration. Spherical aberration is a difficult problem in the optical pickup system for Blu-ray Disc. To reduce the effects of wavelength variation from the laser source, we designed a diffraction optical element. We took a measurement of all of the parts used to make a pickup system and validated the performance of each part. Then, we made a performance test fur the optical pickup system which we developed for Blu-ray Disc and the results were satisfactory.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.153-154
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• 1998

As the fundamental study to set up the algorithm of the X-ray dosimeter, we obtained the data using the designed X-ray input circuit and the semiconductor sensor. We measured the data of the ten time in the various kVp, mA and sec and then the obtained each data is averaged. After the data obtained under the circumstances of total 600, these data saved the database. We developed the algorithm of the X-ray dosimeter using the saved data. Later the result of this study is so important to design X-ray dosimeter.

• Journal of Biomedical Engineering Research
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• v.29 no.5
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• pp.364-370
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• 2008

Recent development in large area flat-panel x-ray detector technology enables clinical application of digital tomosyntesis. Unlike conventional motion tomography using x-ray films, flat-panel x-ray detectors provide projection images in digital formats so that tomographic images can be synthesized in a more flexible way. For the digital tomosynthesis, precise movements of the x-ray source and the x-ray detector with respect to a fulcrum point are necessary. In this study, we apply the digital tomosynthesis technique to the flat-panel detector based micro-CT in which the flat-panel detector and the x-ray source rotate together on a circular arc. The experimental results suggest that flat-panel detector based 3D CTs can be used for digital tomosynthesis in the clinical environment.

• Journal of Astronomy and Space Sciences
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• v.33 no.3
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• pp.147-166
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• 2016

A radio-quiet γ-ray pulsar is a neutron star that has significant γ-ray pulsation but without observed radio emission or only limited emission detected by high sensitivity radio surveys. The launch of the Fermi spacecraft in 2008 opened a new epoch to study the population of these pulsars. In the 2^nd Fermi Large Area Telescope catalog of γ-ray pulsars, there are 35 (30 % of the 117 pulsars in the catalog) known samples classified as radio-quiet γ-ray pulsars with radio flux density (S₁₄₀₀) of less than 30 μJy. Accompanying the observations obtained in various wavelengths, astronomers not only have the opportunity to study the emitting nature of radio-quiet γ-ray pulsars but also have proposed different models to explain their radiation mechanism. This article will review the history of the discovery, the emission properties, and the previous efforts to study pulsars in this population. Some particular cases known as Geminga-like pulsars (e.g., PSR J0633+1746, PSR J0007+7303, PSR J2021+4026, and so on) are also specified to discuss their common and specific features.

• Journal of the Korean Society of Industry Convergence
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• v.11 no.4
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• pp.195-199
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• 2008

The carbon fiber has low x-ray absorption property and high stiffness. This is the reason why many CT(Computed Tomography) manufacturer use carbon fiber in couch tabletop for CT scanner. In this paper, we design and make the couch tabletop made of carbon fiber composite, and verify the validity in CT scanner. In designing the couch tabletop, to determine the aluminum equivalent thickness of couch tabletop, we evaluate X-ray the transmissivity of aluminum and carbon plate in 80-120kVp X-ray energy range. And we perform structural analysis and mechanical design using determined thickness of carbon sheet. In conclusion, it was evaluated that manufactured couch tabletop satisfies X-ray transmissivity and mechanical requirements in CT scanner.

• The Korean Journal of Zoology
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• v.8 no.2
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• pp.33-36
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• 1965

We have carried out a study on the modification of the frequency of X-ray induced lethal and slow growing mutations by colchincine treatment before and after X-ray irradiation in Paramecium aurelia. 1. Lethal and slow-growing mutation induced by X-ray in Paramecium aurelia were reduced by colchicine treatment. 2. The effects of colchicine on the X-ray induced mutations were remarkable in the radiosensitive stages of cell division. 3. The pre-irradiation treatment with colchicine showed no significant influence on the frequency of mutations. 4. It is believed that the reduction of mutation induced by X-ray after treatment with colchicine was due to the fact that the delay of the cell division allowed more time for the pre-mutational damage to recover.

• Annual Conference of KIPS
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• 2017.11a
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• pp.915-916
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• 2017

본 연구에서는 X-ray 영상에서 산란선의 영향을 보정하는 소프트웨어 기법을 제시한다. 영상에서 픽셀값과 에지 요소가 연관된 에너지함수를 정의하고 이를 최적화 하는 방법을 통하여 X-ray 영상을 개선한다. 영상개선 과정에서 추출하는 에지정보의 신뢰성은 응용의 특성과 연관하여 성능에 민감한 영향을 준다. 이에 본 연구에서는 기존의 에지 추출 기법을 통합한 에지 정보 개선 기법을 적용하였으며 실제 X-ray 영상을 사용한 실험결과로부터 제안된 이론의 타당성을 고찰하였다. 이는 X-ray를 사용한 의료진단에서 산란선 보정을 위한 하드웨어의 기능을 대치할 수 있는 방법으로서 의미를 갖는다.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.10
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• pp.886-890
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• 2013

In this paper, a 3D coordinates acquisition method for a mechanical assembly is developed by using multiview X-ray images. The multi-view X-ray images of an object are obtained by a rotary table. From the rotation transformation, it is possible to obtain the 3D coordinates of corresponding edge points on multi-view X-ray images by triangulation. The edge detection algorithm in this paper is based on the attenuation characteristic of the X-ray. The 3D coordinates of the object points are represented on a graphic display, which is used for the inspection of a mechanical assembly.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.2
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• pp.263-268
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• 2001

This paper analyzes error probability performance adopted the Ray Tracing method efficiently analyzing millimeter wave or optic wave in Inter Vehicle Communication(IVC). Analysis environment analyzed bit error characteristic in 60㎓ band with very powerful to multipath wave, to be large to oxygen absorption and to be good to frequency reuse efficiency. We analyzed bit error characteristic of DS/CDMA system by multi access user in Two-Ray rician channel adopted reflect wave of grand, reflect wave of concrete wall and reflect wave of driving vehicle at side road. Improvement performance is adopted MRC diversity.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1693-1696
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• 2004

Synchrotron X-ray micro-imaging technique was employed to monitor non-invasively the refilling process of water inside the xylem vessels in bamboo leaves. The consecutive phase-contrast X-ray images clearly show both plant anatomy and the transport of water inside the xylem vessels. Traces of water-rise, vapor bubbles and variations of contact angle between the water front and the xylem wall were measured in real time. During the refilling process, air bubbles are removed when the rising water front halts at a vessel end for a while. Subsequently, it starts rising again at a higher velocity than the normal refilling speed. Repeated cavitation seems to deteriorate the refilling ability in xylem vessels. In dark environment, the water refilling process in xylem vessels is facilitated more effectively than in bright illuminated conditions. Finally, X-ray micro-imaging was famed to be a powerful, high resolution, real time imaging tool to investigate the water refilling process in xylem vessels.