• Title/Summary/Keyword: 조도측정

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Change of Refractive Error after Watching Smart-phone under Low Intensity of Illumination (낮은 조도에서 스마트폰 시청 후 시력 변화)

  • Kim, Bong-Hwan;Han, Sun-Hee;Kwon, Sang-Jin;Kim, Do-Hun;Kim, Mi-Sung;Jeong, Hyun-Seung;Kim, Hak-Jun
    • Journal of Korean Ophthalmic Optics Society
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    • v.19 no.1
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    • pp.105-109
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    • 2014
  • Purpose: To compare the change of visual acuity and NIBUT after watching smart-phone in 1 hour under low intensity of illumination. Methods: 50 subjects (male 22, female 28) aged 20's years old ($20.7{\pm}2.4$ years) who do not have eye disease and have a good eye condition were participated for this study. Objective refraction, corrected distance visual acuity and NIBUT were measured before and after watching smart-phone (Galaxy 2, Samsung, KOREA) under low intensity of illumination (0 lx.) Objective refraction was carried out using auto-chart project (CP-1000, Dongyang, Korea), phoropter (VT-20, Dongyang, Korea) and auto refractor-keratometer (MRK-3100, Huvitz, Korea). Results: Refractive error was changed from $-3.20{\pm}2.00$ D to $-3.38{\pm}2.00$ D (p=0.006) and corrected distance visual acuity was changed from $0.93{\pm}0.08$ to $0.91{\pm}0.10$ (p=0.000) and NIBUT was changed from $10.48{\pm}7.00$ seconds to $10.29{\pm}6.47$ seconds (p=0.761) before and after watching smart-phone under low intensity of illumination. Conclusions: Continuous watching smart-phone under low intensity of illumination lead to temporal change of distance visual acuity and suitable rest may reduce the influence of distance visual acuity and tear safety.

A study of illumination of dental laboratories (치과 기공실의 조명에 관한 실태 조사 연구)

  • Lee, Hyo-Jung;Choi, Jong-In;Kim, Sung-Sook;Dong, Jin-Keun
    • Journal of Dental Rehabilitation and Applied Science
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    • v.30 no.4
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    • pp.289-298
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    • 2014
  • Purpose: This study was designed to investigate the present conditions of illumination techniques in dental laboratories in order to distinguish colors for esthetic dentistry. Materials and Methods: A total of forty-eight local dental laboratories were selected for sampling a) luminous intensity and b) color temperature. We measured the luminous intensity and the color temperature on a center point of porcelain table with lux meter and color meter respectively. The measurements were performed twice, once on a clear day and on a cloudy day between 12 pm and 2 pm (day light and artificial illumination) and between 7 pm and 10 pm (artificial illumination only). Results: The results obtained were as follows. 1. The average luminous intensity in dental laboratories lighting was 1871 lx, and 67% of dental laboratories had luminous intensity greater than 1600 lx, which was appropriate for operations related to colors, while 33% of dental laboratories had in sufficient lighting for appropriate luminous intensity. 2. The average color temperature in dental laboratories lighting was 6506 K, which was inappropriate for operations related to color. None of the dental laboratories had a color temperature range of 5000 - 5500 K, which is appropriate for operations related to colors. 3. Between daytime and nighttime, also between clear day and cloudy day, the average luminous intensity and color temperature in dental laboratories were not significantly different. Conclusion: Illumination in most dental laboratories selected in this study was inappropriate for operations related to color.

Changes in surface roughness of bracket and wire after experimental sliding - preliminary study using an atomic force microscopy (브라켓과 탄선 간의 마찰 전후 표면 변화 분석 - 원자현미경을 이용한 예비연구)

  • Lee, Tae-Hee;Park, Ki-Ho;Jeon, Ji-Yun;Kim, Su-Jung;Park, Hun-Kuk;Park, Young-Guk
    • The korean journal of orthodontics
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    • v.40 no.3
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    • pp.156-166
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    • 2010
  • Objective: The surface roughness of orthodontic materials is an essential factor that determines the coefficient of friction and the effectiveness of tooth movement. The aim of this study is to evaluate the surface roughness change of the brackets and wires after experimental sliding quantitatively. Methods: Before and after experimental sliding tests, the surface roughness of stainless steel brackets, ceramic brackets, stainless steel wires, and beta-titanium (TMA) wires were investigated and compared using atomic force microscopy (AFM). Results: After sliding tests, changes in the surface of the wire were greater than changes in the bracket slot surface. The surface roughness of the stainless steel bracket was not significantly increased after sliding test, whereas the roughness of ceramic brackets was decreased. Both the surface roughness of stainless steel and TMA wires were increased after sliding test. More changes were observed on the ceramic bracket than the stainless steel bracket. Conclusions: AFM is a valuable research tool when analyzing the surface roughness of the brackets and wires quantitatively.

Measuring Technique For Acoustic Roughness of Rail Surface With Homogeneous Displacement Sensors (동일 변위센서를 사용한 레일표면 음향조도의 측정방법)

  • Jeong, Wootae;Jang, Seungho;Kho, Hyo-In
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.11
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    • pp.7941-7948
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    • 2015
  • Rolling noises during train operation are caused by vibration excited from irregularities of surface roughness between wheel and rail. Therefore, a proper measurement and analysis techniques of acoustic roughness between wheel and rail surface are required for transmission, prediction, and analysis of the train rolling noise. However, since current measuring devices and methods use trolley-based manual handling devices, the measurements induce unstable measuring speed and vibrational interface that increases errors and disturbances. In this paper, a new automatic rail surface exploring platform with a speed controller has been developed for improving measurement accuracy and reducing inconsistency of measurements. In addition, we propose a data integration method of the rail surface roughness with multiple homogeneous displacement sensors and verified the accuracy of the integrated data through standard test-bed railway track investigation.

Investigation of Road Lighting by following Luminaire (조명기구 종류에 따른 도로조명 실태 조사)

  • Lee, Min-Wook;Lee, Chang-Mo;Seok, Dae-II;Jung, Seung-Gyun;Oh, Seok-Sik;Kim, Ki-Nam;Choi, Joo-Yong;Kim, Hoon
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2009.10a
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    • pp.173-176
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    • 2009
  • 조명기구의 종류에 따른 도로조명 실태를 조사하기 위하여 최근 조명기구가 새롭게 교체된 도심지의 도로를 대상으로 조도와 휘도를 측정하였다. 도로조명기준에 제시된 측정법에 맞도록 장비를 구성하여 측정되었으며, 측정결과를 비교 분석하였다.

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Development of a Precision Management System for Quality Control of Progressive die (프로그레시브 금형의 품질관리를 위한 정도관리 시스템 개발)

  • Park, Jong-Nam
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.15 no.9
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    • pp.5434-5439
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    • 2014
  • The surface management of metals was performed with a tool microscope or surface roughness measurement instruments. These methods were not efficient for checking the surface status of the die in the production field. For this reason, an analysis system or measurement system to monitor the wear, defects and surface status as a die ages is required. This study, developed surface analysis software for automatic analysis and standardization of a die or processed products. Software was designed to measure the basic features, such as circles, dots, and lines. The captured images were rendered as three-dimensional representations so that the depth of the grooves on the die and segmental profiles could be estimated. As a result of experimental analysis, the surface roughness was measured with an accuracy more than 93.2%, and the maximum deviation in the surface roughness for the brightness of the lighting was within $3{\mu}m$. The confidence in the device's precision was assured. These results show quality control through efficient surface analysis.

Comparative Study on Feature Extraction Schemes for Feature-based Structural Displacement Measurement (특징점 추출 기법에 따른 구조물 동적 변위 측정 성능에 관한 연구)

  • Junho Gong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.28 no.3
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    • pp.74-82
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    • 2024
  • In this study, feature point detection and displacement measurement performance depending on feature extraction algorithms were compared and analyzed according to environmental changes and target types in the feature point-based displacement measurement algorithm. A three-story frame structure was designed for performance evaluation, and the displacement response of the structure was digitized into FHD (1920×1080) resolution. For performance analysis, the initial measurement distance was set to 10m, and increased up to 40m with an increment of 10m. During the experiments, illuminance was fixed to 450lux or 120lux. The artificial and natural targets mounted on the structure were set as regions of interest and used for feature point detection. Various feature detection algorithms were implemented for performance comparisons. As a result of the feature point detection performance analysis, the Shi-Tomasi corner and KAZE algorithm were found that they were robust to the target type, illuminance change, and increase in measurement distance. The displacement measurement accuracy using those two algorithms was also the highest. However, when using natural targets, the displacement measurement accuracy is lower than that of artificial targets. This indicated the limitation in extracting feature points as the resolution of the natural target decreased as the measurement distance increased.

이온빔 식각을 통한 저마찰용 표면 구조 제어 연구

  • Lee, Seung-Hun;Yun, Seong-Hwan;Choe, Min-Gi;Gwon, Jeong-Dae;Kim, Do-Geun;Kim, Jong-Guk
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.02a
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    • pp.370-370
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    • 2010
  • 최근 자연모사를 통한 초저마찰 연구가 활발히 진행되고 있으며 리소그라피, 레이져 가공법 등의 다양한 방법을 통해 표면구조 제어가 시도되고 있다. 본 연구에서는 자장여과 아크 플라즈마 이온 소스를 이용한 WC-Co 및 SCM 415 금속소재의 표면구조 형상제어를 통해 저마찰 특성을 시도하였다. 자장여과 아크 소스는 90도 꺽힘형이며 5개의 자장 코일을 통해 아크 음극에서 발생된 고밀도($10^{13}\;cm^{-3}$ 이상) 플라즈마를 표면처리 대상 기판까지 확산시켰다. 공정 압력은 알곤가스 1 mTorr, 아크 방전 전류는 25 A, 플라즈마 수송 덕트 전압은 10 V이다. 기판 전압은 비대칭 펄스 (-80 %/+5 %)로 -600 V에서 -800 V까지 인가되었으며 -600 V 비대칭 펄스 인가시기판으로 입사하는 알곤 이온 전류 밀도는 약 $4.5\;mA/cm^2$ 이다. WC-Co 시편의 경우 -600 V 전압 인가시, 이온빔 처리 전 46.4 nm(${\pm}12.7\;nm$)의 조도를 갖는 시편이 5분, 10분, 20분동안 이온빔 처리함에 따라 72.8 nm(${\pm}3\;nm$), 108.2 nm(${\pm}5.9\;nm$), 257.8 nm(${\pm}24.4\;nm$)의 조도를 나타내었다. SCM415 시편의 경우 -800 V 인가시, 이온빔 처리 전 20.4 nm(${\pm}2.9\;nm$)의 조도를 갖는 시편이 20분동안 이온빔 처리함에 따라 275.1 nm(${\pm}43\;nm$)의 조도를 나타내었다. 또한 주사전자현미경을 통한 표면 형상 관찰 결과, 이온빔 식각을 통해 생성된 거친 표면에 $3-5\;{\mu}m$ 직경의 돌기들이 산발적으로 생성됨을 확인했다. 마찰계수 측정 결과 SCM415 시편의 경우, 이온빔 처리전 마찰계수 0.65에서 조도 275.1 nm 시편의 경우 0.48로 감소하였다. 본 연구를 통해 이온빔 식각을 이용한 금속표면 제어 및 저마찰 특성 향상의 가능성을 확인하였다.

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Self-Cleaning of Mortar Mixed with Photocatalyst by Using Methylene Blue Solution (메틸렌블루 용액을 이용한 광촉매 혼입 모르타르의 방오성능 평가)

  • Yang, In-Hwan;Park, Ji-Hun;Park, Hee-Woong;Jung, Hoe-Won
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.8 no.3
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    • pp.356-364
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    • 2020
  • An experimental study to investigate the effect of self-cleaning of mortar mixed with photocatalyst was performed out in this study. Test parameters included the photocatalyst content and surface roughness of the specimens. The experimental mortar specimens were manufactured by mixing a photocatalyst by cement weight of 2.5%, 5.0%, 7.5% and 10.0%. In addition, the surface roughness was categorized into three cases. They included flat surface condition, little surface roughness(medium roughness), and high surface roughness. After mortar specimens were cured for 28 days, they were illuminated by an ultraviolet lamp for 24 hours and immersed in a methylene blue conditioning solution for 12 hours. Thereafter, an ultraviolet(UV) lamp was illuminated on the specimens for 48 hours in an experimental chamber and then the color change of methylene blue solution was measured by using a spectrophotometer over illuminating time of UV lamp. The color change of methylene blue tended to increase as photocatalyst contents increased. Test results meant that photocatalyst was effective for self-cleaning in mortar. However, the color change of the methylene blue solution did not show a noticeable tendency at different surface roughness conditions. It might be due to the uneven photocatalyst distribution on the surface of mortar specimens.