• Title/Summary/Keyword: Laser safety

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Intrapulpal Temperature Change during Cavity Preparation on the Enamel and Dentin with an Er:YAG Laser (Er:YAG 레이저를 이용한 법랑질 및 상아질 와동 형성시의 치수내 온도변화)

  • Yang, Hee-Young;Kim, Mee-Eun;Kim, Ki-Suk
    • Journal of Oral Medicine and Pain
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    • v.30 no.4
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    • pp.457-464
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    • 2005
  • The purpose of our study was to investigate whether the intrapulpal temperature during cavity preparation of enamel or dentin with Er:YAG laser still remained in range of safety for dental pulp protection when combined with appropriate water flow rate. The effect of different pulse repetition rates at the same pulse energy during ablation was evaluated as well. Caries-free, restoration-free extracted human molar teeth were prepared for the specimen and divided two experimental groups of enamel and dentin. Each group comprised 5 specimens and each of tooth specimens were embedded into a resin block each and measuring probe was placed on the irradiated pulpal walls. For experiments of dentin ablation, enamel layers were prepared to produce dentin specimen with a same dentin thickness of 2 mm. A pulse energy of Er:YAG laser was set to 300 mJ and three different pulse repetition rates of 20 Hz, 15 Hz and 10 Hz were employed. Laser beam was delivered with 3 seconds and less per application over enamel and dentin surfaces constant sized by $3\;mm{\times}2\;mm$ and water spray added during irradiation was a rate of 1.6 ml/min. Temperature change induced by Er:YAG laser irradiation was monitored and recorded While enamel was ablated, there was no significant difference of temperature related to pulse repetition rates(p=0.358) and temperature change at any pulse repetition rate was negligible. Significant statistical difference in temperature changes during cavity preparation in dentin existed among three different pulse groups(p=0.001). While temperature rise was noticeable when the dentinal wall was perforated, actual change of temperature due to Er:YAG laser irradiation was not enough to compromise safety of dental pulp when irradiation was conjugated with appropriate water spray. Conclusively, it can be said that cavity preparation on enamel or dentin with an Er:YAG laser is performed safely without pulp damage if appropriate volume of water is sprayed properly over the irradiated site.

Development of Tilt Module for Object Detection of Excavator (굴삭기의 장애물 탐지용 틸트 모듈 개발)

  • Choi, Chang-Hoon;Soh, Ji-Yune;Lee, Jun-Bok;Han, Choong-Hee
    • Journal of the Korea Institute of Building Construction
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    • v.11 no.3
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    • pp.276-282
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    • 2011
  • The construction industry has achieved many benefits through the mechanization of the construction. However, due to accidents for construction machinery, the mortality rate has increased rapidly. Thus, the objective of this study is to develop of tilt modules for object detection system of excavator. The modified laser sensor that increase the efficiency of object detection system was tested. Based on these results, tilt modules were developed through the conceptual design and detailed design. Then, this tilt modules can be applied to the safety management system of excavator and using this tilt modules will be able to improve the efficiency of the system.

Research of Vehicles Longitudinal Adaptive Control using V2I Situated Cognition based on LiDAR for Accident Prone Areas (LiDAR 기반 차량-인프라 연계 상황인지를 통한 사고다발지역에서의 차량 종방향 능동제어 시스템 연구)

  • Kim, Jae-Hwan;Lee, Je-Wook;Yoon, Bok-Joong;Park, Jae-Ung;Kim, Jung-Ha
    • Journal of Institute of Control, Robotics and Systems
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    • v.18 no.5
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    • pp.453-464
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    • 2012
  • This is a research of an adaptive longitudinal control system for situated cognition in wide range, traffic accidents reduction and safety driving environment by integrated system which graft a road infrastructure's information based on IT onto the intelligent vehicle combined automobile and IT technology. The road infrastructure installed by laser scanner in intersection, speed limited area and sharp curve area where is many risk of traffic accident. The road infra conducts objects recognition, segmentation, and tracking for determining dangerous situation and communicates real-time information by Ethernet with vehicle. Also, the data which transmitted from infrastructure supports safety driving by integrated with laser scanner's data on vehicle bumper.

Electrical Properties of Low Density Polyethylene Film by Superstructure Change (고차구조 변화에 따른 저밀도폴리에틸렌 박막의 전기적 특성)

  • Shin, Jong-Yeol;Shin, Hyun-Taek;Lee, Soo-Won;Hong, Jin-Woong
    • Journal of the Korean Society of Safety
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    • v.17 no.4
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    • pp.101-109
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    • 2002
  • The electrical properties of polyethylene are changed by the superstructure. Such crystalline polymer as polyethylene or polypropylene changes crystallinity and products spherulite or trans-crystal when it is cooled slowly. In this study, after thermal treatment of LDPE at 100[${circ}C$], in silicone oil for an hour, we made specimens in order of slow cooling, water cooling, quenching according to cooling speed. Also, to study the influence of electrical properties due to the superstructure change, we analyzed physical properties and performed dielectric breakdown experiments using DC and impulse voltage Moreover we measured space charges in bulk using Laser Induced Pressure Pulse(LIPP) method. Trap level of specimen is 0.064[eV] at the low temperature region 0.31[eV] at the high temperature region in DC dielectric strength, 0.03[eV] at the low temperature region 0.0925[eV] at the high temperature region in impulse dielectric strength. As its result shows that the quantity of charges induced from the electrode surface increases with applied voltage time, and the distribution of space charges in samples increases the quantity of charges in proportion to applied voltage.

Development of Rapid Analytical Method for Heavy Metals (Cd, Pb) in Meju using fs LA-ICP-MS (fs LA-ICP-MS를 이용한 메주의 유해중금속(Cd, Pb) 신속 분석법 개발)

  • Shin, Hee-Chang;Choi, Ji-Hye;Kim, Yong-Kyoung;Kim, Dae-Jung;An, Jae-Min;Kim, Sung-Youn
    • Journal of Food Hygiene and Safety
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    • v.37 no.3
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    • pp.129-135
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    • 2022
  • The official analytical method for the analysis of harmful heavy metals in Meju, distributed in Korea, employs a strong acid to decompose the organic components. This analysis is time consuming and harmful to the users and/or the environment. This study aimed to develop a new pre-treatment technology using laser ablation, to rapidly analyze harmful heavy metals without using strong acids. The results obtained from this method were validated by the National Institute of Food and Drug Safety Evaluation guideline (NIFDS, 2016). Moreover, a comparison of the two methods showed that the analytical time for 55 Meju samples was shortened by 96% or more in the new method. The results showed no significant difference in the recovery ranging from 90-120%. The proposed method proved suitable for detecting harmful heavy metals in Meju.

The Characterization and Coatings on 304 Stainless Steel by Laser Induced Fluorescence Spectroscopy using the High Resolution Charge Coupled Device (레이저 유도형광분광기에서 고정밀 전하장치를 이용한 304 스테인레스 스틸의 코팅과 특성)

  • Kim, Ki-Jun;Lee, Jou-Youb;Sung, Wan-Mo
    • Journal of the Korean Applied Science and Technology
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    • v.33 no.2
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    • pp.385-390
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    • 2016
  • In our study, ceramics coatings by additives of nano alumina and magnesia have cured on 304 stainless steel at $170^{\circ}C$ 2h. We designed and experimented the coated specimens that were characterized by laser induced fluorescence spectroscopy using the charge coupled device and scanning electronic microscopy(SEM). The result was revealed the ceramic coatings added fillers has more excellent on adhesive property and scratch resistance, and less weight loss in acid solution than ceramic coatings non-added fillers. Therefore, this study has designed and manufactured the electromagnetic spectrometry with CCD and then analyzed the coatings on 304 stainless steel using the High Resolution Charge Coupled Device in improving the corrosion resistance of 304 stainless steel. Nowadays, coatings of stainless steel have increased by industrial demand in hygienes, aviation, instrumentations and robotics as the industry special application develops.

Oil Thickness Measurement by Light Absorption Analysis (흡광 광도 분석법을 이용한 기름의 두께 측정 연구)

  • Oh, Sangwoo;Lee, Moonjin
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.16 no.4
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    • pp.263-267
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    • 2013
  • In this research, a novel optical measuring methodology for the measurement of oil thickness in seawater is suggested by evaluating the light absorption which is occurred in the process of penetrating through oil layer on seawater. Laser having monochromatic wave is used as a light source and photodiode which can convert the intensity of the light into an electrical signal is applied to measure the intensity of the penetrating light through the oil-water mixtures. In the experiment, bunker C and lubricating oil are used, and three different lasers having different wavelengths are applied and compared for the selection of an optimal light source. As a result, it is observed that in the case of blue laser, the intensity of the light on the optical sensor decreases with an increase in the oil thickness. Through this relation, both the presence of oil and the thickness of oil can be determined.

Experimental Study on Soot Formation in Opposed-Flow Ethylene Diffusion Flames by Mixing DME as an Alternative Fuel (대체 연료인 DME 혼합에 의한 대향류 에틸렌 확산화염내 매연 생성에 대한 실험적 연구)

  • Yoon, Doo-Ho;Yoon, Seok-Hun;Choi, Jae-Hyuk
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.16 no.3
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    • pp.301-306
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    • 2010
  • DME(Di-Methyl Ehter, $CH_3OCH$) is currently attracting worldwide attention due to its environmentally friendly characteristics. Until now it was researched as a major alternative fuel of diesel automobile because it is a clean fuel producing low soot. Therefore, in this study, in order to investigate the effect of DME mixing on number density and size of soot particle, DME has been mixed in opposed-flow ethylene diffusion flame with the mixture ratios 5%, 14% and 30%. A laser extinction/scattering technique has been adopted to measure the volume fraction, number density, and size of soot particles. The experimental results showed that the soot concentration of mixture flames with the mixture ratios 5% and 14% produces soot more, even though that of 30% was decreased. This means that even though DME has been known to be a clean fuel for soot formation, the mixing of DME in diffusion flame of ethylene, where acetylene maintains high concentration in soot formation regions, could produce enhanced production of soot.

Object Detection From 3D Terrain Data Gener Ated by Laser Scanner of Intelligent Excavating System(IES) (굴삭 자동화를 위한 레이저 스캐너 기반의 3차원 객체 탐지 알고리즘의 개발)

  • Yoo, Hyun-Seok;Park, Ji-Woon;Choi, Youn-Nyung;Kim, Young-Suk
    • Korean Journal of Construction Engineering and Management
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    • v.12 no.6
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    • pp.130-141
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    • 2011
  • The intelligent excavating system(IES), the development in South Korea of which has been underway since 2006, aims for the full-scale automation of the excavation process that includes a series of tasks such as movement, excavation and loading. The core elements to ensure the quality and safety of the automated excavation equipment include 3D modeling of terrain that surrounds the excavating robot and the technology for detecting objects accurately(i.e., for detecting the location of nearby loading trucks and humans as well as of obstacles positioned on the movement paths). Therefore the purpose of this research is to ensure the quality and safety of automated excavation detecting the objects surrounding the excavating robot via a 3D laser scanning system. In this paper, an algorithm for estimating the location, height, width, and shape of objects in the 3D-realized terrain that surrounds the location of the excavator was proposed. The performance of the algorithm was verified via tests in an actual earthwork field.

Sterilization Effect of Microbial Strains by using Non-ionizing Radiation (비전리방사선을 이용한 미생물 균주 멸균효과)

  • Jeong, Kyeonghwan;Seo, Jeongmin
    • Journal of the Korean Society of Radiology
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    • v.14 no.6
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    • pp.833-839
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    • 2020
  • Globally, infection prevention and social awareness have been greatly changed by the severe acute respiratory syndrome coronavirus, and as a result, the infection control guidelines and procedures for patients with high exposure to hospital-acquired infection are further strengthened and management and monitoring are more thorough. In order to prevent infection, sterilization should be carried out with the highest priority, and we will find a sterilization method that is low in cost, easy to install, and easy to operate, to present appropriate sterilization effects. In this study, the UV sterilizer was used to contaminate the caries bacteria with an output of 4 W and irradiation time of 60, 150, and 300 sec, and the laser was irradiated with outputs of 0.8 and 1.5 W at wavelengths of 266 and 355 nm, respectively. Ultraviolet sterilizer showed safety in infection prevention at over 150 sec, and laser showed safety in prevention at 1.5 W, 0.8 W, and 266 nm. As a result, the higher the output and the wavelength closer to 253.7 nm, the better the sterilization effect.