• The Journal of Korean Society for Radiation Therapy
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• v.13 no.1
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• pp.109-112
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• 2001

1. 목적 : head and neck cancer 환자의, C-T 영상을 이용한 방사선치료계획시 치과 보철물에 의해 발생하는 artifact가 선량 계산에 미치는 영향을 분석하고자 한다. 2. 재료 및 방법:두 경부와 유사한 크기의 Polystyrenes Phantom ($20{\times}20{\times}25cm^3$) 을 제작하고, 팬톰내에 금으로 인공보철물을 제작하여 보철물 부착 전.후를 C-T Scan (High Speed Advantage, GE, US) 하였다. artifact에 의한 영향을 쉽게 분석하기위해 팬톰내에 다른 구조물은 만들지 않았으며 두가지 방법으로 얻어진 영상을 이용하여 조사면의 크기와 조사 방향을 변화 시켜 가며 1문 조사(SSD 100 cm)에 의한 치료 계획(3D RTP system, Prowess, US)을 수립하여 기준점(5,10 cm depth)에서의 선량 변화를 비교 분석하였다. 아울러 3회 반복 scan하여 artifact에 발생 유형과 CTNo을 이용한 density을 분석하였다. 3. 결과: C-T Scan으로 얻어진 image 상에 나타난 Artifact는 CT no $-1000{\sim}+2775$(기준 $-1000{\sim}+3700$)까지의 다양한 값을 가지며 보철물을 기준으로 방사형태로 분포하였다. artifact가 선량 계산에 미치는 영향을 분석한 결과 보철물 사용시 5cm깊이의 기준점에서 절대선량은 평균 $+1.5{\pm}2.8\%$, 10 cm 깊이에서는 $+1.8{\pm}3.5\%$의 오차를 보였다. 조사방향에 의한 오차는 artifact에 대해 측면 조사한(gantry $270^{\circ}$)경우에서 높게 관찰되었다. 4. 결론: 두 경부 종양의 방사선 치료시 치과 보철물에 의한 artifact는 흔히 관찰가능하며 본 실험을 통해 다양한 형태와 다양한 density을 가짐을 알수있었다. 영상에 나타난 정도에 비해 선량계산에 미치는 평균 오차는 낮게 평가되었지만 조사 방향과 보철물의 위치에 따라 변동이 크게 나타날 수 있어 치료 계획시 가능한 artifact의 영향을 적게 받는 빔의 선택이 정확한 선량 계산에 도움을 줄 것으로 사료된다.

• Journal of the Korean Geographical Society
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• v.49 no.5
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• pp.747-760
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• 2014

This study presents the extent of disparity of human capital across regions, its trend, and the impact of aging on it, using Korean census data of years 1985, 1995, and 2005. Main results are as follows. First, the absolute level of human capital in cities and districts have increased, but the relative positions of those regions have not changed over time. Second, the proportion of college graduated tends to increase as the size of cities increases. Third, following Berry and Glaeser(2005), the increase in the proportion of college graduated is regressed on the initial proportion and the estimates indicate that the disparity of human capital across regions has increased over time. Fourth, the proportion of aging population is shown to have a negative relationship with the proportion of college graduated. Finally, using a counter-factual scenario that there were no differences in proportions of aging population across regions, it is shown that the disparity of human capital across regions could be reduced substantially.

• 전자공학회논문지 IE
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• v.43 no.4
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• pp.65-75
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• 2006

This thesis deals with a wavelet-based method of denoising of infrared images contaminated with impulse noise and Gaussian noise, he method of thresholding the wavelet coefficients using derivatives and median absolute deviations of the wavelet coefficients of the detail subbands was proposed to effectively denoise infrared images with noises. Particularly, in order to eliminate the impulse noise the method of generating binary masks indicating locations of the impulse noise was selected. By this method, the threshold values dividing edges and noises were obtained more effectively proving the validity of the denoising method compared with the conventional wavelet shrinkage method.

• Economic and Environmental Geology
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• v.14 no.4
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• pp.183-191
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• 1981

Major and trace elements analyses are presented for 13 amphibolites by wet chemical and emission spectroscopic methods. These chemical data were compared with limestone and quartzite closely associated with the amphibolites. The chemical similarity of the amphibolites studied to the basic igneous rock and low oxidation ratios (<30) are indicative of the igneous intrusive, especially middle stage differentiates. Petrographic and stratigraphic study of the rocks suggest the more igneous features rather than those of sedimentary progenitors.

• Polymer(Korea)
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• v.36 no.6
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• pp.761-767
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• 2012

The polycarbonate (PC)-based optical diffusers for direct-lit LED backlight unit were prepared by using extrusion compounding followed by compression molding process. The application of inorganic porous silica particles as a diffusing agent in addition to conventional poly(methyl methacrylate) (PMMA) beads was attempted, and the optical, thermal, and mechanical properties of the prepared diffusers were investigated. The morphological observations revealed that the diffusing agents could be uniformly dispersed in the PC matrix without agglomeration by high shear stress generated during extrusion process. The incorporation of the porous silica particles mixed with PMMA beads remarkably enhanced the luminance uniformity with respect to both location and view angle for the diffuser, while minimizing the reduction in the absolute luminance, as compared with the diffuser containing only PMMA beads. In addition, thermal and mechanical properties of the diffusers were shown to be improved upon addition of the porous silica particles.

• Journal of Korean Library and Information Science Society
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• v.35 no.4
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• pp.293-316
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• 2004

The best way of getting knowledge is reading in the Cho-sun dynasty, so getting books is the most interesting thing to the scholars. The most important way of getting books for scholars in Cho-sun dynasty is taking Bansabon published and given to scholars by government. but there is few data and few concrete studies of it. This study deals with the object and the scale of distribution of books on the basis of Bansagi ; king Jeong-jo published 『Kyujangjeonun』 distributed about 1,500 volumes to scholars and govermment agencies.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2010.04a
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• pp.370-371
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• 2010

The Long Range Navigation (LORAN) had been mainly used world-wide until GPS (Global Positioning System) activation. In particular. it was essential junctionality for the ships to sail the oceans. However, according to the industry's developing, the current accuracy of Loran is insufficient for the utilization such as the harbour approach, the land navigation and the field of precise timing. Therefore it is necessary the study on the improvement of the positioning accuracy of Loran. The method of its improvement is to measure and compensate the propagation time delay, that is, additional secondary factor (ASF) between the transmitter and user's receiver. This study shows the technique for the absolute time delay measurement without a time of coincidence (TOC) table, and represents the ASF measurement result between Pohang transmitter station(9930M) and each measure points.

• Journal of Korea Multimedia Society
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• v.8 no.3
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• pp.345-354
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• 2005

Since motion estimation and motion compensation methods remove the redundant data to employ the temporal redundancy in images, it plays an important role in digital video compression. Because of its high computational complexity, however, it is difficult to apply to high-resolution applications in real time environments. If we have a priori knowledge about the motion of an image block before the motion estimation, the location of a better starting point for the search of an exact motion vector can be determined to expedite the searching process. In this paper presents the motion detection algorithm that can run robustly about recusive motion. The motion detection compares and analyzes two frames each other, motion of whether happened judge. Through experiments, we show significant improvements in the reduction of the computational time in terms of the number of search steps without much quality degradation in the predicted image.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.5
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• pp.421-426
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• 2009

The emissivity is different because the emitted angle changes according to the position of the infrared thermography camera and object. Because of this, the temperature distribution expressed when measuring the temperature by using the infrared thermography system is not the accuracy temperature. Although the real surface temperature is constant, the temperature measured by using infrared thermography camera have error in accordance with the value of emissivity. In this paper, the temperatures of the round cylindrical object and the flat square object that heated to the equal temperature were measured by infrared thermography camera. The emissivity calibration formula and correction table are made with the affect of the view angle and emission angle form the surface temperature value. The error of measured temperature values are corrected by using the emissivity calibration formula and correction table, and apply to defect detection of the nuclear power plant pipe. From the calibration method, reliability surface temperature values were obtained.

• 한국해양학회지
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• v.29 no.1
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• pp.42-49
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• 1994

A series of radiocarbon dating from intertidal, subtidal, and inner continental shelf deposits investigated along the west coast of Korea as well as from its offshore sea floor (namely, the eastern Yellow Sea Basin) how (1) the Holocene sea level rise, i.e., the ecstatic sea-level history during the oxygen isotope stage 1, and (2) pre-Holocene sea-level fluctuations during the oxygen isotope stages 2 and 3. Marine geophysical investigations in the Yellow Sea reported a possible development of desert and loses deposits due to dieselization under the cold and dry climate during the Last Glacial Maximum. The Kanweoldo deposit overlain unconformably by the Holocene intertidal deposits, which is mainly exposed along the tidal channels and intertidal flats in the Cheonsu Bay, the west coast of Korea, shows the characteristic cryogenic structure (cryoturbation). Such cryoturbation structure of the Kanweoldo deposit appears to indicate the cold and dry climate under the ecstatic sea-level paleoshoreline standing before and after of the pre-Holocene interstitial period (about 30000 y BP is suggested and its shoreline curve is constructed.