• 상하수도학회지
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• 제35권6호
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• pp.489-496
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• 2021

Water disinfection using UV-LED(Light emitting diode) has many advantages, such as smaller footprint and power consumption as well as relatively longer lifespan than those of conventional mercury-UV lamps. Moreover, UV-LED disinfection is considered an environmentally benign process due to its mercury-free nature. In this study, disinfection using an LED module emitting 275nm UV was carried out. 384 UV-LEDs were put into a cylinder tube with a capacity of 1.7 liters. The UV intensity of the UV-LED module was controlled from 1.7 to 8.4 mW/cm². The disinfection efficiency for the model microorganism solutions(E. coli ) was monitored. As the UV intensity(I) and contact time(t) varied, inactivation of the microorganisms from 2 to 4-log-removals(i.e., 99 to 99.99% of disinfection efficiency) was achieved. Disinfection using UV-LED was followed to 1^st order reaction and the reaction rate constant, k was determined. In addition, the relationship between UV intensity(I) and contact time(t) in order to obtain 99.99% of disinfection efficiency was modeled: I^1.2·t= 460, which indicates that the product of UV intensity and contact time requiring 4-log-removals is always constant.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 추계학술대회 논문집
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• pp.219-224
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• 1997

In surface grinding, the contact between the grinding wheel and the workpiece introduces heat and resistance, which restrict the self-dressing of the grits and result in burrs and cracks on the workpiece. Therefore, before or during th grinding wheel for more accurate performance. In order to determine the dressing time monitoring method of grinding wheel in surface grinding, a three-dimensional computer simulation of the grinding operation has been attempted based on the contact mechanism and surface-shaping system between the grinding wheel and the workpiece. The optimal dressing time is determined based on the amount of the grain wear and work surface roughness.

• 한국환경보건학회지
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• 제40권1호
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• pp.17-26
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• 2014

Background: Despite children's unique characteristics that distinguish them from adults, relatively few attempts have been made to measure exposure factors for characterization of children's exposure to hazardous chemicals in child-specific products (CSP). This study was conducted to establish the child-specific exposure factors for exposure and risk assessment of hazardous substances in CSP. Methods: We investigated the exposure factors (e.g., time use of child-products, time and frequency of object-to-body contact, time and frequency of object-to-mouth contact) influencing children's exposure to CSP (e.g., toys, playmats, oil pastels, etc.) in 650 children through a parent-completed questionnaire using a web-based survey. Participants were recruited in five age groups, <1, 1-2, 2-3, 3-6, and 6-12 years of age. Results: The child-specific exposure factors were presented as the mean, median, $95^{th}$ percentile, minimum, and maximum values. Time activity for play mats was the longest among CSP and infants spent more time on them than did elder age groups (189.3-224.7 min/day for <1-2 years vs. 91.2 min/day for 6-12 years). It is apparent that time and frequency of toy block- and plastic toy-to-mouth contact significantly decreased as a function of age. When the variation of CSP use patterns was compared by gender, the only variable that was statistically different between genders was time activity in child-products exposure space. Conclusion: We believe the five child-specific exposure factors suggested in the present study will be valuable for reducing uncertainty in the estimation of chemical exposure during risk assessment of CSP and furthermore, in the appropriate regulations to protect children's health.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.1106-1108
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• 2004

The arcing contact wear of circuit breakers can be the major cause for the maintenance requirement. The control of arcing times as short as possible but larger than the given minimum arcing time may be the effective way to mitigate the contact wear and to lessen the expenditure of a maintenance. In this paper the method for minimizing the arcing time is described. The basic concept used in the proposed method is the estimation of the current interruption instant from the informations such as the phase angle at the instant of trip commands and the magnitude of interrupted currents.

• 한국정밀공학회지
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• 제12권9호
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• pp.52-58
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• 1995

Conventional measurement methods for non-destructive testing(NDT) in nuclear power plants and other industrial plants have been performed as the methods of contact with objects to be inspect, but those methods have been taken relatively much time to be inspected. Holographic interferometry which is a non-contact optical measurement method using a coherent light can overcome these demerit, and also has an advantage that the quantitative measurement of small deformation for large areas can be accomplished at a time with high precision. In this paper the comparisons of the experimental results form holographic interferometry with those from the finite element method(FEM) and the analytical solutions of the elastic equation are discussed.

• 한국자동차공학회논문집
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• 제14권4호
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• pp.181-191
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• 2006

The most common kind of vehicular accident is the low-speed rear-end impact that result in high portion of insurance claims and Whiplash Associated Disorders(WAD). The low-speed collisions have specific characteristics that differ from high speed collisions and must be treated differently This paper presents a simple continuous contact force model for the low-speed rear-end impact to simulate the accelerations, velocities and the contact force as functions of time. A smoothed Coulomb friction force is used to represent the effect of braking, which was found to be significant in simulating low-speed rear end impact. The intervehicular contact force is modeled using nonlinear damping and spring elements with coefficients and exponents. This paper presents how to estimate analytically stiffness and damping coefficients. The exponent of the nonlinear contact force model was determined to match the overall acceleration pulse shape and magnitude. The model can be used to determine ${\Delta}Vs$ and peak accelerations for the purpose of accident reconstruction and for injury biomechanics studies.

• 구강회복응용과학지
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• 제29권1호
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• pp.59-68
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• 2013

이 논문의 목적은 시간에 따른 교합의 변화를 측정할 수 있는 T-scan system을 이용하여 젊은 성인 남성(33명)정상교합에서의 하악골 측방운동 시 교합접촉 양상을 분석하는 것이다. 정해진 하악 위치에서의 교합접촉이 아닌, 기능적 범위 내에서 비작업측 교합이개 시점에서의 교합접촉 양상을 분류하고 분류된 군 간에 교합이개 시간, 측방유도 시 견치가 담당하는 교합력의 비율, 측방운동 시 가해지는 교합력 등을 비교하였다. 연구 결과 기존의 분류와는 다른 측방접촉들이 존재하였고 군기능 유도가 우세하게 나타났다. 교합이개 시간, 측방유도 시 견치가 담당하는 교합력의 비율, 측방운동 시 가해지는 교합력 등에서 군 간의 유의한 차이를 나타내었다. T-scan system은 교합접촉 양상을 분류하고 교합력, 교합이개 시간, 견치가 담당하는 교합력 비율 등의 항목을 비교 분석하는데 있어서 유용한 도구이다.

• Corrosion Science and Technology
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• 제15권4호
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• pp.166-170
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• 2016

The combined process of porous type anodizing and desiccation treatment was applied to improve wettability of A1050 aluminum alloy. The water contact angles of anodized samples were increaseds considerably with desiccation treatment. However, there was no considerable effect of polishing and anodizing time on water contact angle. The corrosion behavior with the treatments was investigated electrochemically. The corrosion resistance of the samples in 3.5 mass% NaCl solutions increased with higher contact angle. Anodized and desiccated samples showed better corrosion resistance than un-desiccated samples around rest potential region.

• 설비공학논문집
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• 제22권5호
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• pp.282-288
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• 2010

Experiment on the surface characteristics of polymer films treated by atmospheric pressure plasma has been conducted. We chose the process parameters as frequency, gas flow, treatment time, and scrutinized the effects of the process parameters on the surface characteristics of polymer materials by measuring the contact angle and examining SEM. As the result, the surface characteristics highly depends on frequency, reaction gas and treatment time. In the case of PC substrate, the contact angle was changed from $83.5^{\circ}$ (before plasma treatment) to $30^{\circ}$ (after plasma treatment) at 30 kHz, CDA 0.6%, and number of repeat 7. In the case of PET substrate, the contact angle change was found from $59^{\circ}$ to $23.5^{\circ}$ at 20 kHz, CDA 0.6%, and number of repeat 7. In the case of EVA substrate, it shows from $84^{\circ}$ to $44.2^{\circ}$ at 30 kHz, CDA 0.6%, and number of repeat 7.

• 한국표면공학회지
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• 제25권4호
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• pp.189-206
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• 1992

The effect of activation and electroless nickel plating conditions on contact properties was investi-gated for selective electroless nickel plating of Si wafers in order to obtain an optimum condition of con-tact hole filling. According to RCA prosess, p-type silicon (100) surface was cleaned out and activated. The effects of temperature, DMAB concentration, time, and strirring were investigated for activation of p-type Si(100) surface. The optimal activation condition was 0.2M HF, 1mM PdCl2, 2mM EDTA,$ 70^{\circ}C$, and 90sec under ultrasonic vibration. In electroless nickel plating, the effect of temperature, DMAB concentra-tion, pH, and plating time were studied. The optimal plating condition found was 0.10M NiSO4.H2O, 0.11M Citrate, pH 6.8, $60^{\circ}C$, 30minutes. The contact resistance of films was comparatively low. It took 30minutes to obtain 1$\mu\textrm{m}$ thick film with 8mM DMAB concentration. The film surface roughness was improved with decreasing temperature and decreasing pH of the plating solution. The best quality of the film was obtained at the condition of temperature $60^{\circ}C$ and pH 6.0. The micro-vickers hardness of film was about 800Hv. Plating rate of nickel on the hole pattern was slower than that of nickel on the line pattern.