• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.1
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• pp.185-194
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• 2014

This study investigates the methodology to evaluate the quantified performance of pavement markings and traffic guide signs using digital images. This methodology is significant to attempt to quantify their performance without large brightness photometer at the nighttime and bad weather. The retroreflective performance of pavement markings are evaluated through the contrast of gray levels of pavements and markings in collected digital images under the case of rain, dampness, and dryness. In addition, the appraisal of retroreflective performance of traffic guide signs are implemented through the comparison between interior illuminated and the existing retroreflective traffic guide signs using the contrast of luminance extracted from the value of RGB of backgrounds and legends in collected digital images according to geometric design, driving lanes, and the distance between the car and the sign. As a result, the retroreflective performance of pavement markings deteriorates about 3.5 times and 2 times under the case of rain and dampness respectively than dryness. Also, the performance of the existing traffic guide signs is significantly influenced by geometric design, driving lanes, and the distance, otherwise interior illuminated traffic guide signs. This methodology can be utilized to construct objective information of performance of traffic safety facilities to select appropriate position of expensive high reflective pavement markings and interior illuminated traffic guide signs considering diverse weather and geometric design.

• Journal for History of Mathematics
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• v.22 no.3
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• pp.79-102
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• 2009

Most who have heard of Sang-Seol Lee know him for his contribution to the Korean independence movement nearly a hundred years ago. This paper, however, will discuss Lee's other great contribution to his country; that of being "The father of modern mathematical education in Korea". Lee passed the rigorous government officer examination with the highest honor and became a teacher for the royal prince. Later he became the president of Sunkyunkwan, a national institute of higher learning since 1398, and eventually a well-known university bearing the same name. Lee was also a highly regarded Confucian scholar and well versed in foreign languages. He wanted Korea to become a modern country and felt that the areas of science and engineering were studies that needed improving in order to achieve modernization. While researching Western textbooks on the subjects he realized that Western mathematics would be especially important for Korea. With that, it became his mission to integrate Western mathematics into the Korean educational system. This paper will explain the importance of Sang-Seol Lee's contributions to mathematic education in Korea and how it helped Korea become the modern nation it is today.

• Journal of the Speleological Society of Korea
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• v.45 no.46
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• pp.69-79
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• 1996

동굴은 미지의 세계이고, 암흑의 신비로운 지하세계이기 때문에 우리 인간에게는 매우 흥미로운 공간이라고 할 수 있다. 그러므로 이러한 공간을 관광자원으로 활용하여 지역주민이 소득을 올리고, 청소년에게 탐험의 세계, 모험의 세계는 물론 자연학습의 현장으로 활용할 수 있게 하는 바람직한 경우도 있다. 그러나 이러한 경우 동굴이 개발되면 전자와 같은 긍정적인 면이 있는 반면에 동굴의 파괴, 오손 및 오염과 같은 악영향을 가져오게 되므로 동굴을 개발할 당시부터 악영향을 최소하기 위해서는 환경보전과 환경보호에 커다란 관심을 가져야 한다. 따라서 본 연구에서는 이제 동굴 개장이 2개월밖에 되지 않은 천곡동굴이 관광지로 개방됨으로써 나타나게 될 환경변화를 미리 살펴보고 그에 대한 대책을 마련하려고 하였다. 그 결과는 다음과 같다. 첫째, 천곡동굴의 경우 동굴 공간이 넓고 관광통로가 왕복통로로 되어 있어 체동인구가 2배가 되므로 많은 관광객의 출입시 동굴 내부의 기온이 상승하기 때문에 동시에 관람할 수 있는 적정 관람객 수를 조절해야 한다. 둘째, 천곡동굴은 개장 시일이 오래 경과하지 않았기 때문에 퇴적물의 파손이 전무하다고 할 수 있다. 따라서 이 상태를 계속 유지하기 위해서 동굴 내부에 관리인을 상주시킨다거나, 입동객의 소지품을 보관할 수 있는 장소를 마련하여 동굴퇴적물을 훼손할 수 있는 물건의 반입을 애초에 방지하는 방안도 필요하다고 본다. 마지막으로, 동굴 개발 당시 조명을 너무 가깝게 설치한 때문에 개방 후 얼마 되지 않았음에도 불구하고 몇 군데에서 녹색균류가 관측되고 있으므로 조명시설의 원거리 조정이나 간접조명 대책을 강구해야 한다.만 아니라 오류의 크기도 확률적으로 변하는 상황을 모형에 반영하여 보다 현실성있게 모형화하였다.균 6.5점(2-9점)으로 대체로 높게 나타났는데 이는 대중매체와 신문, 잡지류를 통한 지식의 정보가 많기 때문으로 생각된다 비만 정도에 따라서는 유의적인 차이를 보이지 않았다. 5. 비만 정도와 상호간의 관계를 보면 BMI 수치가 높을수록 비만인 형제수가 많았으며, 자신의 비만 자각도도 높았다. 편식율은 비만 정도가 낮을수록 높았으며, 식품섭취 빈도 점수는 비만군에서 높았으나, 저녁식사 후 간식섭취는 BMI가 높은 군에서 하지 않는 비율이 더 높았는데 이것은 감수성이 예민한 여학생들이 자신의 외모에 대한 의식적인 노력으로 보인다. 이상과 같은 결과를 종합해 볼 때 중학교 여학생들은 학교수업을 중심으로 비교적 규칙적인 생활을 하고 따로 운동을 할 시간이 많지 않은 것으로 나타났다. 비만과 관련하여서는 유전적인 요인도 중요하지만 식습관 개선과 식품이 적절한 선택 등을 강조하여 연령과 생활환경에 맞는 영양교육이 필요하다고 본다.알 수 있으며, 현미 30% 첨가한 B2가 그 다음 순위로 선호되어, 백설기 제조에서 율무와 현미의 첨가량은 10%가 권장된다.농촌 지역 여고생보다 많이 섭취하였고, 탄수화물은 농촌지역 여고생이 대도시 지역 여고생에 비하여 유의적으로 많이 섭취하였다. 지역별 여고생의 에너지섭취 비율은 탄수화물 : 단백질 : 지방의 섭취 비율이 대도시 60.75% : 16.4% 22.9%이며, 중소도시가 62.7% : 15.7% : 21.5%,농촌이66.8% : 14. l% : 19.1%이었다. 영양지식의 정확도나 인지도는 영양소 섭취와 유의적인

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.2
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• pp.179-186
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• 2013

Purpose: To compare corneal asphericity, visual acuity (VA), and ocular and corneal higher-order aberrations (HOAs) between myopic refractive surgery and emmetropia groups. Methods: Twenty three subjects ($23.0{\pm}2.5$ years) who underwent myopic refractive surgery and twenty emmetropia ($21.0{\pm}206$ years) were enrolled. The subjects'criteria were best unaided monocular VA of 20/20 or better in both two groups. High and low contrast log MAR visual acuities were measured under photopic and mesopic conditions. Corneal and ocular HOAs were measured using Wavefront Analyzer (KR-1W, Topcon) for 4 mm and 6 mm pupils. Corneal asphericity was taken by topography in KR-1W. Results: There was no significant difference in VA between two groups under either photopic or mesopic conditions. In ocular aberrations, there were significant differences in total HOAs, fourthorder and spherical aberration (SA) for a 6 mm between two groups (p=0.045, p<0.001, and p<0.001, respectively). In corneal aberrations, there was a significant difference in SA for 4 mm (p=0.001) and 6 mm (p<0.001) pupils between two groups and there were statistically significant differences in total HOAs (p<0.001) and fourth-order aberrations (p<0.001) between two groups for a 6 mm pupil. There was a significant correlation in emmetropia between Q-value and SA in ocular aberrations for 4 mm and 6 mm pupils (r=0.442, p=0.004, and r=0.519, p<0.001) and in corneal aberrations for 4 mm and 6 mm pupils (r=0.358, p=0.023, and r=0.646, p<0.001). No significant correlations were found between Q-value and SA in refractive surgery group. Conclusions: VA in myopic refractive surgery is better than or similar to emmetropia. Nevertheless, the more increasing pupil size is, the more increasing aberrations are. Thus, it could have an influence on the quality of vision at night.

• Journal of Preventive Medicine and Public Health
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• v.25 no.3 s.39
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• pp.247-268
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• 1992

This study was conducted to evaluate the effect of VDT work on eyes and vision among workers in a TV manufacturing plant. The study subjects consisted of 264 screen workers and 74 non-screen workers who were less than 40 years old male and had no history of opthalmic diseases such as corneal opacities, trauma, keratitis, etc and whose visual acuity on pre-employment health examination by Han's test chart was 1.0 or above. The screen workers were divided into two groups by actual time for screen work in a day : Group I, 60 workers, lesser than 4 hours a day and group II, 204 workers, more than 4 hours a day. From July to October 1992 a questionnaire was administered to all the study subjects for the general charateristics and subjective eye symptoms after which the opthalmologic tests such as visual acuity, spherical equivalent, lacrimal function, ocular pressure, slit lamp test, fundoscopy were conducted by one opthalmologist. The proportion of workers whose present visual acuity was decreased more than 0.15 in comparison with that on the pre-employment health examination by Han's test chart was 20.6% in Group II. 15.0% in Group I and 14.9% in non-screen workers. However, the differences in proportion were not statistically significant. The proportion of workers with decreased visual acuity was not associated with the age, working duration, use of magnifying glass and type of shift work (independent variables) in all of the three groups. However, screen workers working under poor illumination had a higher proportion of persons with decreased visual acuity than those working under adequate illumination (P<0.05) . The proportion of workers whose near vision was decreased was 27.5% in Group II, 18.3% in Group I, and 28.4% in non-screen workers and these differences in proportion were not statistically significant. Changes of near vision were not associated with 4 independent variables in all of the three groups. Six out of seven subjective eye symptoms except tearing were more common in Group I than in non-screen workers and more common in Group II than in Group I (P<0.01). Mean of the total scores for seven subjective symptoms of each worker(2 points for always, 1 point for sometimes, 0 point for never) was not significantly different between workers with decreased visual acuity and workers with no vision change. However, mean of the total scores for Group II was higher than those for the Group I and non-screen workers (P<0.01). Total eye symptom scores were significantly correlated with the grade of screen work, use of magnifying glass, and type of shift work. There was no independent variable which was correlated with the difference in visual acuity between the pre-employment health examination and the present state, the difference between far and near visions, lacrimal function, ocular pressure, and spherical equivalent. Multiple linear regression analysis for the subjective eye symptom scores revealed a positive linear relationship with actual time for screen work and shift work(P<0.01). In this study it was not observed that the VDT work decreased visual acuity but it induces subjective eye symptoms such as eye fatigue, blurred vision, ocular discomfort, etc. Maintenance of adequate illumination in the work place and control of excessive VDT work are recommended to prevent such eye symptoms.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.356-356
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• 2012

InGaN/GaN LEDs는 1993년에 처음 소개 된 이래로, 성장, 제품 면에서 끊임없는 발전을 이루어 왔다. 따라서 GaN 기반의 LED는 조명, 디스플레이 그리고 후광 발광판 등 다양한 분야에서 사용되고 있다. 현재 GaN 기반의 LED는 낮은 작동전류에서 높은 내부, 외부 효율을 보인다고 알려져 있다. 그러나 LED는 보통 높은 작동 전류에서 사용하고 있는데 이 전류 값에서 'Efficiency Droop'이라 하는 효율 저하가 나타난다. 이 현상의 원인으로는 결함, Auger 영향, 캐리어 누설, 격자 불일치로 인한 내부 장 효과, 그리고 온도의 영향 등이 이 효율저하를 일으키는 주된 원인으로 생각되고 있다. 하지만 최근 효율저하의 원인에 대하여 결함, 그리고 온도 변화의 실험 등을 통하여 실험적으로 Auger 영향은 효율 저하의 원인으로 가능성이 매우 낮고 누설 전류가 효율저하의 주된 원인의 가능성이 높다고 많은 그룹에서 문제제기를 하고 있는 추세이다. 이 연구에서, 효율저하의 특성을 분석하기 위하여 GaN 기반의 EBL이 있는 LED와 없는 LED를 이용하였다. I-V 곡선, 주입 전류에 따른 반치폭의 변화와 스펙트럼의 변화, 그리고 외부 효율 등의 비교 분석을 통하여 효율 저하의 원인이 누설 전류에 의함이라고 분석을 할 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.289-289
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• 2009

Light emitting diode(LED) has many advantages including lower energy consumption and longer lifetime and eco-friendly in comparison with traditional light sources. Spheric plastic lens generally used in LED lighting occurs aberration and ghost image which give displeasure and deteriorate vision quality in human eyes. Using the optical program (LightTools$^{TM}$, CodeV$^{TM}$), we were confirm the aberration and ghost image in optical simulation and employed aspheric lens form in the lens design to improve these problems. From the comparison of the simulation results between the aspheric lens and the spheric lens, we were ascertain to be improved both aberration and Ghost image.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.51-52
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• 2006

FFL의 내구성 및 신뢰성 확보를 위해 Lamp 상태에서 원하는 부위에 $-15^{\circ}C$를 유지하기 위한 Cold Spot을 부착하여 Lamp안의 Hg이 완전히 포집되도록 한다. 이후 이 Cold Spot을 제거하여 Hg peak과 Ne Peak의 Ratio의 변화를 관찰하며 Hg이 이동하는 것을 관잘 하여 Lamp 내에서 이동 속도와 Lamp 간에 이동 속도를 확인 할 수 있다. Lamp 내에서는 80분이 경과한 후에 Hg 이동이 Saturation되는 것을 확인 할 수 있고, Lamp 간에는 100시간이 경과후에 Saturation 되는 것을 확인 할 수 있었고, Ratio는 Channel내는 70 ~ 150, Channel간에는 6~10 정도임을 확인하여 Hg이 이동되는 속도와 회복되는 수준을 알 수 있었다.

• Journal of the Korea Computer Graphics Society
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• v.20 no.4
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• pp.1-7
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• 2014

The volume rendering has become an important technique in many applications along with hardware development. Understanding and perception of volume visualization benefit from visual cues which are available from shading. Better visual cues can be obtained from global illumination models but it's huge amount of computation and extra GPU memory need cause a lack of interactivity. In this paper, in order to improve visual cues on volume rendering, we propose an image space occlusion shading model which requires no additional resources.

• Transactions of Materials Processing
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• v.24 no.6
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• pp.437-442
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• 2015

The development of polishing technology has enabled the production of injection molds with high quality surfaces and shapes. For products such as mobile phones which require high quality performance the use of plastic materials has many constraints such as shrinkage and deflection. The purpose of the current research is to use reverse engineering in order to find and analyze the data of a selected aspherical lens and then creating a process to design an improved lens. Additionally, the improved lenses are subject to molding analysis. In order to solve this problem, the lens construction program, Zemax, was used to analyze and optimize performance. In the case of optimization, the object was to eliminate spherical aberration and to find good MTF data. The result of the optimization data was similar to the MTF data found from a random lens. Specific resin and analysis conditions were selected and CAD modeling was done to enhance the injection molding analysis.