• The korean journal of orthodontics
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• v.38 no.3
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• pp.214-222
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• 2008

Objective: The aim of this study was to investigate the experimental brush wear pattern of a light cured surface sealant, Biscover (Bisco, Schaumburg, IL), and to evaluate its cariostatic effect. Methods: Caries-free human premolars were used for the Biscover coating group (n = 90) and the control group (n = 10). The Biscover coating group was randomly assigned to nine subgroups of 10 each and the control group was assigned to two subgroups of 5 each according to the number of brushing strokes. An experimental 3-body wear test was conducted under different strokes of wear test. Tooth-brushing was accomplished with movement of each brush head set at a frequency of 100 rpm under a force of 1.5N, Surface roughness was tested before, and after Biscover coating, and after brushing. Then, each of the 10 teeth of both groups were placed in artificial caries inducing solution for 7 days. All tooth surfaces were assessed using scanning electron microscopy. Results: Biscover coated surfaces showed a smoother texture than enamel surfaces. The roughness was increased after experimental brushing and after 10,800 brushing strokes, the whole layer of Biscover wore out. However, teeth in the Biscover coating group had a cariostatic effect in cariogenic conditions. Conclusions: We suggest that white lesions in orthodontic patients can be suppressed by topical applications of Biscover.

• Journal of Preventive Medicine and Public Health
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• v.29 no.1 s.52
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• pp.1-14
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• 1996

To evaluate the health risk of the workplace environment of a general hospital toward the hospital workers, a questionnaire survey on the perception of risk at the workplace environment and environmental measurements at 27 locations with 240 workers in the hospital were made from October 25th, 1993 to October 30th, 1994. The results were as follows ; 1. By the environmental measurements, 86 workers(36%) were found to be exposed to poor or harmful degree of general illumination, 193 workers(80%) were exposed to poor or harmful local illumination, 34 workers(14%) were exposed to poor or harmful degree of thermal condition and 180 workers(75%) were exposed to poor or harmful noise level, but nobody was exposed to poor or harmful dust and toluene concentration. Also nobody was exposed to poor or harmful level of radiation or anticancer/antibiotic agents. 2. The subjective perceptions on the environmental conditions felt by the workers were different from the objective findings by the environmental measurements. The workers underscored the poor illumination state and overscored the dust concentrations. Also workers oversensitized about the thermal condition, the noise level, the radiation level, the toluene concentration and anticancer/antibiotic agents 3. The sources of noise were the dialogue(179 workers) and the office instruments(131 workers). The sources of dust came from the clothes(108 workers) and the building materials(79 workers). 4. The questionnaire survey showed that the 28 workers were exposed to poor or harmful level of the antibiotics, 10 workers to alkali or acid and 6 workers to drug dust in the pharmacy but the above findings could not be proved by the environmental measurements.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.29 no.2
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• pp.417-422
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• 1999

Purpose : The aim of this study was to assess the validity of standard deviation of gray scale histogram in digital subtraction radiography as a test parameter for superimposition error. Materials and Methods : Twenty periapical radiographs were used as baseline images and they were copied to exclude the influence of exposure geomety and contrast differences. These subsequent images were linearly displaced by 0.1-0.5 mm in the x-. y- and xy-directions, rotated by 0.5-3° and distorted by angular contraction of 1-5° in x- and y-axis before subtraction. The standard deviations of gray levels in the subtraction images were obtained and paired t-tests were performed. Pearson correlation coefficients(r) were calculated between the standard deviations and the superimposition errors. Results : Linear displacement showed high correlation coefficients of 0.997, 0.997 and 0.995 in x-. y- and xy-axis respectively. Statistically significant different standard deviation existed among all linearly displaced groups(p<0.05). Distortion showed relatively low correlation coefficients of 0.982 and 0.959 in x- and y-axis. The standard deviations between the two distortion groups were statistically significant different(p<0.05). Conclusion : Standard deviation of gray level distribution in digital subtraction images is satisfactory but not perfect similarity measure to assess the superimposition errors.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.125-125
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• 2012

물리증착(physical vapor deposition; PVD)은 진공 또는 특정 가스 분위기에서 고상의 물질을 기화시켜 기판에 피막을 형성하는 방법으로 증발과 스퍼터링 그리고 이온플레이팅 등이 있다. PVD 방법으로 박막을 제작하면 대부분의 박막은 주상정 구조로 성장하게 된다. 이러한 주상정의 조직을 제어하는 방법으로 빗각 증착(oblique angle deposition; OAD) 기술이 있다. OAD는 타겟(증발원)에 대해서 기판을 평행하게 배치하는 일반적인 코팅방법과는 달리 기판의 수직성분과 타겟의 수직성분이 이루는 각도가 0도 이상이 되도록 조절하여 기판을 기울인 상태로 코팅하는 방법을 말한다. OAD 방법을 이용하면 기판으로 입사하는 증기가 초기에 생성된 핵(seed)에 의해 shadowing이 발생하면서 증기가 수직으로 입사하는 normal 증착과는 다른 형상의 성장 조직이 만들어지게 된다. 본 논문에서는 OAD 방법을 이용하여 Al과 TiN 박막을 제조하고 그 특성을 비교하였다. Al 박막은 UBM (Un-Balanced Magnetron) 스퍼터링 소스를 이용하여 빗각을 각각 0, 30, 45, 60 및 90도의 각도에서 강판 및 실리콘 웨이퍼 상에 시편을 제조하되 단층 및 다층으로 시편을 제조하고 치밀도와 함께 조도와 반사율을 비교하고 염수분무시험을 이용하여 내식성을 평가하였다. TiN 박막은 Cathodic Arc 방식을 이용하되 Al 박막과 동일한 방법으로 코팅을 하고 내식성 및 경도 등의 특성을 비교하였다. TiN 박막은 경사각이 커지면서 경도가 낮아졌으나 바이어스 전압을 이용하여 다층으로 제조함에 의해 경도는 유지하면서 modulus를 낮출 수 있어서 박막의 신뢰성을 나타내는 H3/E2 값은 증가함을 알 수 있었다.

• Clean Technology
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• v.11 no.2
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• pp.83-90
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• 2005

This paper is about a new method of synthesis organic tanning agent (polymer, polyphenol, polyresin) and discusses their tanning property. It was found that properties of the leather manufactured with application of organic tanning agent were similar to those applied with conventional chrome tanning agent and reducing effects of Cr, T-N, COD, SS concentrations in the effluent.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.251-255
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• 2008

We have developed an electronic aids, called SmartWand, which can help visually impaired people walk safely and tell them an object's color and environmental brightness SmartWand can inform visually impaired people of the dangerous obstacles around which they can't notice by the white cane such as a large panel with supporting poles on the street. Especially we have lmproved the previous version of SmartWand by reflecting the result of user study.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.744-748
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• 2008

우리의 삶의 터전이 도시화됨에 따라 수문현상에도 많은 변화가 생겼다. 이로 인해 기존의 수문해석을 위한 방법을 대신해 도시화된 유역의 새로운 수문해석 방법의 개발이 불가피하게 되었다. 이에 따라 본 연구에서는 도시유출 모형인 SWMM의 대표적 프로그램인 XP-SWMM을 이용하여 도시유역의 유출모의를 하였다. 대상유역으로 선정한 곳은가양천배수분구로 전형적인 도시 하천 유역모습을 하고 있다. 이 유역의 특성치와 확률강우량 산정 후 XP-SWMM 모형에 적용시켜 재현기간별 첨두홍수량을 구하고, 동일 유역을 HEC-HMS로 모의하여 그 차이를 분석하였다. 도시화가 진행되면서 대규모 시설 등이 들어서면서 도로와 인도가 포장되므로 침투는 감소하고, 따라서 유역내 조도계수가 감소되며, 수로망 정비 등에 의해 유입시간이 빨라져 첨두홍수량이 증가하게 되었다. 이와 같은 변화로 인해 기존 홍수량을 구하기 위한 방법의 변화는 필수 불가결하게 되었다. 따라서 본 연구의 중점과제인 저류지에 의한 홍수조절능력에 대한 분석은 대상 유역내에 일정한 크기의 저류지를 상 중 하류위치에 따라 지점선정 후 그에 따른 홍수량과 침수량의 변화를 비교..분석하여 저류지 위치별 홍수조절능력에 대한 평가를 실시하였다.

• Korean Journal of Optics and Photonics
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• v.15 no.2
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• pp.158-170
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• 2004

Wireless optical communication is expected for high-speed optical communication in the areas of saturated optical fiber communication and low population density. In this paper, we present an optical transmitter system for wireless optical communication with new design concepts different from the usual optical imaging system. The specifications are the following: the source is a laser diode(LD) of wavelength 830 nm in which the divergent angle from the tangential plane differs from that from the sagittal plane. Here, the requested transmission distances are very long range such as 500 m to 1500 m and beam diameter is 3 m at the receiver with symmetrical energy distribution. For the evaluation characteristics of this kind of non-imaging system, two optical quantities, the relative illumination distribution and energy transfer efficiency, are numerically calculated through lots of ray tracing.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2007.05a
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• pp.447-449
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• 2007

유해성 적조생물인 C. polykrikoides에 대한 해역별 적조잠재력 평가를 위하여 유해성 적조가 자주 발생하는 남해안의 소리도 부근해역, 광양만, 남해도 주변해역, 거제만, 부산연안의 해수 및 해저퇴적물을 채집하여 배양실험을 실시하였다. 실험을 위한 기본배지는 f/2배지에서 배양조건은 온도 $20^{\circ}C$, 염분 34, 조도 2000Lux, 그리고 실험생물은 대수증식기의 C. polykrikoides를 $300cells/m{\ell}$접종하였다. 해역별 해수에 대한 적조생물 성장은 광양만에서 가장 높아 적조발생 잠재력이 가장 높았고, 다음은 부산 기장, 거제, 남해연안 순서로 성장이 높게 나타났으며, 질산성 질소 농도는 $0.35{\sim}24.74{\mu}M$ 범위로 적조생물의 성장과 같은 순서를 나타내었다. 한편 해저 퇴적물 용출액은 적조생물의 성장을 현저히 촉진시켰으며, 남해도 미조연안의 해저 퇴적물 용출액에서 적조발생 잠재력이 가장 높았고, 부산 형제도연안, 광양만, 거제만, 소리도연안의 해저퇴적물 순서로 적조생물의 성장을 촉진시키는 결과를 나타내었다. 그리고 적조생물의 성장은 인산염의 농도에 의해서 성장이 결정되었던 것으로 추정되며, 용출된 인산염의 농도 $1.59{\sim}10.39{\mu}M$ 범위로 남해 미조연안, 부산 형제도 연안, 광양만, 거제만, 소리도 연안 순서로 C. polykrikoides의 성장과 같은 순서로 나타났다.

• KIEAE Journal
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• v.12 no.2
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• pp.25-32
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• 2012

This paper focused on the daylighting performance of residential high-rise buildings in South-Korea. the purpose of this study is to estimate the visual environment of sunlight coming into opening according to sky conditions, orientation of windows and each space of Apartment buildings. Season of the year, weather, and time of day combine with predictable movement patterns of the sun to create highly variable and dynamic daylighting conditions. Daylighting design is usually based on the dominant sky condition and the micro-climate for the building site. There are three common sky conditions: clear sky, overcast sky, and partly cloudy sky. The clear sky includes sunshine and is intense and brighter at the horizon than at the zenith, except in the area around the sun. Daylight received within a building is directly dependent upon the sun's position and the atmospheric conditions. Easily used charts, diagrams, and software programs allow study of solar geometry for any geographic location and time of day. on the other hand, the overcast sky is characterized by diffuse and variable levels of light and has dense cloud cover over 90% of the sky. This paper was calculated by a Desktop Radiance program. The space dimensions were based on a unit module of real constructed apartment having divided into five sections such as living room, room1, room2, room3 and kitchen.