• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.7
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• pp.945-952
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• 2018

Recently, bass fishing has become a marine leisure sport in Korea. There are 4 major fishing associations in Korea, and each association holds 10-15 tournaments each year. However, supply of 17 ft bass boats, which are preferred in leagues, depends 100 % on imports. In this study, we have derived the main specifications to develop the initial hull forms of a 18.5ft bass boat through statistical analysis based on mothership data. In addition, CFD numerical analysis was carried out according to deadrise angle and longitudinal center of gravity, which strongly influenced the resistance and planing performance. For numerical analysis, design speed was set to $Fn=3.284 (Re=9.858{\times}10^7)$, the deadrise angle was set from 12 to $20^{\circ}$, and the longitudinal center of gravity was set in the range of 0 to $8%L_{wL}$ from the center of buoyancy to the stern. Based on the numerical results, we first set the range of these factors by resistance performance and immersion keel length. Furthermore, using a correlation graph of Savitsky's Drag-Lift ratio, we derived the deadrise angle ($14-16^{\circ}$) and longitudinal center of gravity ($4-6%L_{wL}$).

• Journal of the Korean Vacuum Society
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• v.20 no.6
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• pp.395-402
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• 2011

The nanomechanical properties of fully lithiated and unlithiated silicon nanowire deposited on silicon substrate have been studied with atomic force microscopy. Silicon nanowires were synthesized using the vapor-liquid-solid process on stainless steel substrates using Au catalyst. Fully lithiated silicon nanowires were obtained by using the electrochemical method, followed by drop-casting on the silicon substrate. The roughness, derived from a line profile of the surface measured in contact mode atomic force microscopy, has a smaller value ($0.65{\pm}0.05$ nm) for lithiated silicon nanowire and a higher value ($1.72{\pm}0.16$ nm) for unlithiated silicon nanowire. Force spectroscopy was utilitzed to study the influence of lithiation on the tip-surface adhesion force. Lithiated silicon nanowire revealed a smaller value (~15 nN) than that of the Si nanowire substrate (~60 nN) by a factor of two, while the adhesion force of the silicon nanowire is similar to that of the silicon substrate. The elastic local spring constants obtained from the force-distance curve, also shows that the unlithiated silicon nanowire has a relatively smaller value (16.98 N/m) than lithiated silicon nanowire (66.30 N/m) due to the elastically soft amorphous structures. The frictional forces of lithiated and unlithiated silicon nanowire were obtained within the range of 0.5-4.0 Hz and 0.01-200 nN for velocity and load dependency, respectively. We explain the trend of adhesion and modulus in light of the materials properties of silicon and lithiated silicon. The results suggest a useful method for chemical identification of the lithiated region during the charging and discharging process.

• Progress in Medical Physics
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• v.18 no.1
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• pp.48-54
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• 2007

This study is to develope a phantom for MOSFET (Metal Oxide Semiconductors Field Effect Transistors) dosimetry and compare the dosimetric properties of standard MOSFET and microMOSFET with the phantom. In this study, the developed phantom have two shape: one is the shape of semi-sphere with 10cm diameters and the other one is the flat slab of $30{\times}30cm$with 1 cm thickness. The slab phantom was used for calibration and characterization measurements of reproducibility, linearity and dose rate dependency. The semi-sphere phantom was used for angular and directional dependence on the types of MOSFETs. The measurements were conducted under $10{\times}10cm^2$ fields at 100cm SSD with 6MV photon of Clinac (21EX, Varian, USA). For calibration and reproducibility, five standard MOSFETS and microMOSFETs were repeatedly Irradiated by 200cGy five times. The average calibration factor was a range of $1.09{\pm}0.01{\sim}1.12{\pm}0.02mV/cGy$ for standard MOSFETS and $2.81{\pm}0.03{\sim}2.85{\pm}0.04 mV/cGy$ for microMOSFETs. The response of reproducibility in the two types of MOSFETS was found to be maximum 2% variation. Dose linearity was evaluated In the range of 5 to 600 cGy and showed good linear response with $R^2$ value of 0.997 and 0.999. The dose rate dependence of standard MOSFET and microMOSFET was within 1% for 200 cGy from 100 to 500MU/min. For linearity, reproducibility and calibration factor, two types of MOSFETS showed similar results. On the other hand, the standard MOSFET and microMOSFET were found to be remarkable difference in angular and directional dependence. The measured angular dependence of standard MOSFET and microMOSFET was also found to be the variation of 13%, 10% and standard deviation of ${\pm}4.4%,\;{\pm}2.1%$. The directional dependence was found to be the variation of 5%, 2% and standard deviation of ${\pm}2.1%,\;{\pm}1.5%$. Therefore, dose verification of radiation therapy used multidirectional X-ray beam treatments allows for better the use of microMOSFET which has a reduced angular and directional dependence than that of standard MOSFET.

• Korean Journal of Cognitive Science
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• v.27 no.3
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• pp.355-376
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• 2016

We used holes defined by color similarity (Experiment 1) and binocular disparity (Experiment 2) to study how the inner contour of an object (i.e., boundary of a hole in it) is encoded in visual working memory. Many studies in VWM have shown that an object's boundary properties can be integrated with its surface properties via their shared spatial location, yielding an object-based encoding benefit. However, encoding of the hole contours has rarely been tested. We presented objects (squares or circles) containing a bar under a change detection paradigm, and relevant features to be remembered were the color of objects and the orientation of bars (or holes). If the contour of a hole belongs to the surrounding object rather than to the hole itself, the object-based feature binding hypothesis predicts that the shape of it can be integrated with color of an outer object, via their shared spatial location. Thus, in the hole display, change detection performance was expected to better than in the conjunction display where orientation and color features to be remembered were assigned to different parts of a conjunction object, and comparable to that in a single bar display where both orientation and color were assigned into a single bar. However, the results revealed that performance in the hole display did not differ from that in the conjunction display. This suggests that the shape of holes is not automatically encoded together with the surface properties of the outer object via object-based feature binding, but encoded independently from the surrounding object.

• Journal of radiological science and technology
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• v.28 no.4
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• pp.267-272
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• 2005

The effects of As addition in amorphous selenium (a-Se) films for digital X-ray conversion material have been studied using the moving photocarrier grating (MPG) technique. This method utilizes the moving interference pattern generated by the superposition of the two frequency shifted laser beams for the illumination of the sample. This moving intensity grating induces a short circuit current, jsc in a-Se:As film. The transport parameters of the sample are extracted from the grating-velocity dependent short circuit current induced in the sample along the modulation direction. The electron and hole mobility, and recombination lifetime of a-Se films with arsenic (As) additions have been obtained. We have found an increase in hole drift mobility and recombination lifetime, especially when 0.3% As is added into a-Se film, whereas electron mobility decreases with As addition due to the defect density. The transport properties for As doped a-Se films obtained by using MPG technique have been compared with X-ray sensitivity for a-Se:As device. The fabricated a-Se(0.3% As) device film exhibited the highest X-ray sensitivity out of 5 samples.

• Journal of the Korean Chemical Society
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• v.27 no.4
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• pp.244-254
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• 1983

Single crystals of sodium thiosulfate $(Na_2S_2O_3) have been grown from the saturated solution by the evaporation method at the optimum condition. Radiation damages in the crystal by ${\gamma}$-irradiation of $20{\times}10^6$ Rontgen have given rise to paramagnetic centers. The anisotropic spectra of each paramagnetic species have been obtained with the X-band EPR spectrometer at room temperature. When an isotropic D.P.P.H. at g value of 2.0036 is based on. ESR Spectra of the single crystal are recorded for each rotation about the perpendicular a, b and c axis with intervals of $10^{\circ}$ from $0^{\circ}$to $180^{\circ}$ in order to find out the properties of the crystal for anglar variation of the anisotropic peaks. The g values are calculated from the line position between the anisotropic peaks and the isotropic peaks of D.P.P.H. and then principal g values and their direction cosines of the species is obtained by the diagonalization of 9 matrix elements of the corresponding g values. From the analysis of the characteristic principal g values and direction cosines for ${\gamma}$-irradiated $Na_2S_2O_3$ crystal, anisotropic peaks corresponding to $SO_2^+, SO_2^- $are identified and the existences of unidentified and unstable paramagnetic defects are verified.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1921-1925
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• 2010

개수로의 흐름을 측정하는 유속계는 유체역학 및 수리학적 연구와 유량 측정 등의 업무에 필수적인 장비이다. 그동안 국내에서는 일부 전자파표면유속계(이상호 등, 1997)와 영상처리 기반의 LSPIV(김영근 등, 2004)와 같은 비접촉식 유속측정 장치가 개발되어 활용되고 있지만, 유속 및 유량 측정에 보다 널리 사용되고 있는 수중 투입식 유속계의 경우 거의 개발되지 않았다. 특히 유속 분포를 측정하는데 활용될 수 있는 초음파 방식 유속 프로파일러는 거의 전적으로 외국제품에 의존하고 있다. 일반 유속계가 점유속을 측정하는데 비해 유속 프로파일러는 센서가 지향하는 방향선을 따라 공간적인 유속분포를 동시에 획득할 수 있으므로 측정 효율성이 높다는 장점을 지닌다. 본 연구에서는 국내 기술로 개수로 흐름 측정에 활용할 수 있는 초음파 유속 프로파일러를 개발하였다. 이 유속 프로파일러는 초음파 펄스를 반복적으로 송수신하는 PRF 기법을 이용하여 개발하였다. 개발된 유속 프로파일러는 직사각형 수로에서 유속 분포를 측정하기 위해 적용하였으며, 기존의 2차원 유속계와 그 결과를 비교하였다. 본 연구에서 개발한 유속 프로파일러는 실제 하천에 활용하기에는 측정 가능한 유속 및 수심 범위의 한계가 있으나 PRF 기법의 한계 범위에서는 실측 유속분포를 비교적 잘 재현하는 것으로 나타났다.

• Journal of Korean Society of Transportation
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• v.20 no.5
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• pp.163-174
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• 2002

Speeding has been reported as one of the major causes for fatal traffic accidents in Korea. The resolution against this dangerous speeding comes to make the automated speed enforcement system an enforcement tool. The speed detection device, which measures speeds of each incoming vehicles using double loop sensors, requires high accuracy. The object of this study is to develop an accurate speed measurement algorithm using double loop detectors. Some important findings are summarized as follows: 1) It was found that speed measurement errors are caused by scanning rate, distance of two loops, irregular vehicle trajectories, multiple vehicles in detection zone. 2) A proposed algorithm using two signal set proved to reduce variance as well as mean of speed measurement. 3) A proposed filtering algorithm was effective to filter irregular driving vehicles and multiple vehicles in detection zone. A comprehensive field test of developed algorithm resulted in significant improvement of speed measurement accuracy.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.4 s.316
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• pp.86-92
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• 2007

A discrete dynamic model for tracking feature points in 2D images is developed. Conventional snake approaches deform a contour to lock onto features of interest within an image by finding a minimum of its energy functional, composed of internal and external forces. The neighborhood around center snaxel is a space matrix, typically rectangular. The structure of the model proposed in this paper is a set of connected vertices. Energy model is designed for its local minima to comprise the set of alternative solutions available to active process. Block on tracking is one dimension, line type. Initial starting points are defined to the satisfaction of indent states, which is then automatically modified by an energy minimizing process. The track is influenced by curvature constraints, ascent/descent or upper/lower points. The advantages and effectiveness of this layer approach may also be applied to feature points tracking of digital image whose pixels have one directional properties with high autocorrelation between adjacent data lines, vertically or horizontally. The test image is the ultrasonic carotid artery image of human body, and we have verified its effect on intima/adventitia starting points tracking.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1373-1377
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• 2007

준설은 수중굴착, 운반(배송), 매립 기술로 구분되는데, 국내에서는 아직까지 각 기술을 통합한 체계적인 연구가 수행되지 못하고 있다. 준설분야는 토질, 수리 등의 토목 분야 기술뿐만 아니라 기계, 제어, 환경 등 여러 분야의 기술들이 매우 복잡하게 연계되어 있으며, 제한된 소수의 기술자들과 특수 대형 장비-준설선에 의해 수행되기 때문이다. 최근에는 장비의 대형화, 첨단화가 진행되면서 선진국과의 기술격차로 인해 국제 경쟁력이 약화되어 심각한 위기에 처해있는 현장기술 분야이다. 유럽의 델프트 공대, IHC, 준설협회(CEDA)는 세계 기술 개발을 주도하고 있으며, 미국에서는 육군공병단의 수로국에서 준설을 담당하고 있으며 DOER(Dredging Operation & Environmental Research) 기술 개발을 주도하는 등 선진국에서는 이미 여러 연구가 진행되었으며 준설기술이 정착되어있다. 본 연구에서는 현재 현대건설에서 보유중인 아산3호를 모델로 축소모형을 제작하여 실험하였다. 본 연구에서는 선행실험으로 성층형성 및 석션펌프 작동시 물입자의 운동방향을 PIV로 촬영한 결과에 커터헤드를 추가 장착 시행하여 이를 바탕으로 수치해석시 발생할 수 있는 오류를 수정 보완 할 것이다. 차후 실험에서는 준설토의 조건과 기계적 조건 및 환경적인 영향력을 고려한 여러 가지 방법으로 진행할 계획이며, 실험 조건에서는 각 매개변수를 달리하여 이를 토대로 데이터를 구성하고, 측정을 통해서 얻어지는 결과 값을 기초로 하여 준설시에 환경과 매개변수의 조건에 따른 준설량의 특성을 파악하고 효율을 향상시킬 수 있는 방향을 제시할 것이며, 이를 통해서 기본적인 메뉴얼을 구성할 계획이다. 수리실험의 결과값을 바탕으로 이를 현실무 작업에 적용할 경우 효율적인 준설작업을 수행할 수 있을 것으로 판단된다. HDL-콜레스테롤 함량은 유의차가 없었다. 간조직 중 총지질, 총콜레스테롤 및 중성 지방 함량은 HC군이 NC군에 비하여 유의하게 증가되었다. HC-LREL 군과 HC-LREH군은 HC군에 비하여 간조직 중 총지질 함량만이 유의하게 저하되었다. 이상의 결과 연근 에탄올 추출물은 in vitro에서 HMG-CoA reductase 활성을 농도 의존적으로 저하시켰으며, in vivo 에서는 고콜레스테롤 식이급여로 증가되어진 LDL-콜레스테롤 및 중성지질 함량을 감소시키고, 감소되어진 인지질 함량을 증가시킴으로써 고콜레스테롤 혈증 및 지방간의 예방과 치료에 효과가 있을 것으로 사료되나 연근의 어떠한 성분의 작용 기전에 의한 것인지에 대해서는 더욱 체계적인 연구가 요구된다.}nlein$ nephritis가 3례로 가장 많았다. 미세변화 신증후군 71명 중 비재발군이 16명으로 22.5%, 비빈발 재발군 49.3%, 빈발 재발군 18.3%, 스테로이드 의존군 9.9%를 보였다. 결론 : 대전시에서의 신증후군 환아의 발생빈도는 15세이하 소아 10만명당 약 5명으로 추정되었으며 10여 년전과 비교하여 큰 변화를 보이지는 않았다. 또한 저자들의 임상병리학적 연구결과가 다른 문헌에서 보고된 소아 신증후군의 연구결과와 큰 차이를 보이지 않음을 알 수 있었다. 자극에 차이가 있지 않나 추측되며 이에 관한 추후 연구가 요망된다. 총대장통과시간의 단축은 결장 분절 모두에서 줄어들어 나타났으나 좌측결장 통과시간의 감소 및 이로 인한 이 부위의 통과시간 비율의 저하가 가장 주요하였다. 이러한 결과는 차가운 생수 섭취가 주로 결장 근위부를 자극하는 효과를 발휘하는 것이 아닌가 해석된다. 이와 같은 연구결과를 통해 생다시마를 주원료로 개발된 생다시마차와 생다시마 음료가 만성 기능성 변비 증세를 개선하는 효