• 한국전자통신학회논문지
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• 제19권1호
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• pp.127-136
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• 2024

뿌리산업의 유해한 작업 환경과 높은 작업 강도는 작업자의 건강에 영향을 미칠 수 있기 때문에 기존에는 유해한 물질로부터 현장 작업자를 보호하기 위해 반년 단위로 작성한 환경을 측정하여 규제하고 있다. 그러나 작업환경 외에 작업자 건강 상태 등에 대해서는 정량화된 관련 기준이 부재하여 상시로 피해를 주는 임계치 이하 유해 물질의 지속적인 노출에 따른 직업병을 예방하는데 어려움이 상존하고 있다. 따라서 본 논문에서는 기계학습을 이용한 뿌리산업 작업 환경의 위험도 피크레벨 결정방법을 제안하고 이를 토대로 작업장의 실시간 안전 평가를 가능하게 하였다.

• 대한소아치과학회지
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• 제30권3호
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• pp.385-390
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• 2003

청소년기에는 두개악안면부위의 외상성 손상이 흔하다. 그러나 상아질, 백악질, 치수를 포함하는 치아파절로 정의되는 치근파절은 비교적 드물다. 치근파절에 대하여 취 할 수 있는 적절한 조치는 파절편의 치관부위를 재위치시키고, $2{\sim}3$달간 레진강선 고정술을 시행하는 것이다. 치수괴사나 치근흡수의 징후가 나타날때까지 근관치료를 보류해야 하는데 대부분의 증례에서 파절편의 치근부위는 그 생활력을 유지하기 때문이다. 본 증례의 10세 4개월된 남아는 상악영구중절치의 치근파절을 주소로 연세대학교 치과병원에 내원하였으며, 그후 7년동안 동일부위에 2번의 반복적인 외상이 있었으나 파절편 치관부의 재위치, 레진 강선 고정술, 근관치료 시행 후 임상적으로 방사선학적으로 비교적 양호한 치료결과를 얻었기에 보고하는 바이다.

• Journal of Periodontal and Implant Science
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• 제30권2호
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• pp.455-472
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• 2000

Instrumentation for periodontal therapy may induce marginal damage which increases plaque accumulation and result in periodontal disease. But there have not been many reports of instrumentations on the artificial crown so far. Therefore this study is conducted to evaluate the effects of various repeated instrumentations on the porcelain crown marginal portion. Of the 10 extracted periodontally diseased maxillary first premolars, were 12 proximal surface used in this study. The finishing line of the preparation was placed on the root surface below CEJ and then the crown was cast and cemented in usual manner. Every 4 surfaces of the 3 instruments-curet, ultrasonic scaler, and ultrasonic curet- is used. and four samples used in each instruments. The relevant procedures and measurements were repeated 3 times in each surfaces. Marginal gap is measured by the microscope and surface roughness, Scannig Probe Microscope. Measurements are made at 5 points in each surfaces, making 20 points in each instrument. The results evaluated statistically were as follows 1. As instrumentation was repeated, both marginal gap and roughness were increased in all group 2. In the hand curet, marginal gap was increased every instrumentation and roughness was increased after second. 3. In the ultrasonic scaler, both marginal gap and roughness were increased every instrumentation. 4. In the ultrasonic curet, marginal gap was increased after third instrumentation and roughness was increased after second. 5. Marginal gap and roughness used by the ultrasonic curet were lower than the others and no difference was seen between the hand curet and ultrasonic scaler From the results of this study, the ultrasonic curet was useful in some aspect, but careful instrumentation was needed. Furthermore it was important to minimize the instrumentation through complete periodontal therapy before setting and adequate plaque control.

• 한국전자파학회논문지
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• 제14권1호
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• pp.1-7
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• 2003

Davidenko 방법으로 정확하게 구하여진 정규화 복소 전파 상수로부터 원형 유전체 봉의 누설 모드를 조사하였다. 도파 모드의 차단 주파수 아래에서 nonphysical 영역, 안테나 모드 영역, Reactive 모드 영역, spectral gap영역 등의 독특한 주파수 영역이 관찰되었다.

• Journal of Welding and Joining
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• 제21권3호
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• pp.40-45
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• 2003

The high-speed rotating arc process forms a flat bead surface with decreased penetration depth because the molten droplets are deflected by centrifugal force. Therefore the rotating arc welding for horizontal fillet welding increases the leg length with the increase of rotation frequency and prevents the deflection of weld bead and overlap. In this study, the relationship between the welding parameters and the weld bead shape - leg length and undercut - are investigated experimentally. Consequently, the weld quality could be improved by rotating arc welding, and sound weld bead was achieved when applied to horizontal fillet welding with 4mm gap by avoiding the undercut which is inevitable for the conventional GMA welding methods.

• Journal of Welding and Joining
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• 제21권3호
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• pp.46-50
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• 2003

The horizontal fillet joint is one of the most important weld joints in the shipbuilding industry. High-speed rotating arc welding, which can increase the leg length, is an effective way to improve the weld productivity and quality for the horizontal fillet welding. Based on the Taguchi method, the effects of welding parameters on bead characteristics - leg length, asymmetry, undercut, overlap - are investigated fur high-speed welding process. As a result, the adequate welding parameters are selected for the required leg length, symmetric bead and no undercut. Besides, considerably consistent leg length is observed for the horizontal fillet welding with gap variation up to 3mm.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.858-864
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• 2017

This study aims to restrain free conducting wire-type particles which are commonly and dangerously existing within DC gas-insulated transmission lines. A realistic platform of a coaxial cylindrical electrode was established by using a high-speed camera and a partial discharge (PD) monitor to observe the motion, PD, and breakdown of these particles. The probabilities of standing or bouncing, which can be affected by the length of the particles, were also quantitatively examined. The corona images of the particles were recorded, and particle-triggered PD signals were monitored and extracted. Breakdown images were also obtained. The air-gap breakdown with the particles was subjected to mechanism analysis on the basis of stream theory. Results reveal that the lifting voltage of the wire particles is almost irrelevant to their length but is proportional to the square root of their radius. Short particles correspond to high bouncing probability. The intensity and frequency of PD and the micro-discharge gap increase as the length of the particles increases. The breakdown voltage decreases as the length of the particles decreases.

• Agricultural and Biosystems Engineering
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• 제2권2호
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• pp.75-80
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• 2001

This paper describes method to diagnose abiotic stresses such ad low root temperature, low light intensity and high salinity in cucumber plants with several physiological instruments. The stresses could be detected by measuring and analyzing the differences in chlorophyll content, temperature difference between leaf and atmosphere and light absorptance at wavelengths of 480, 560, 710, 1420 and 1650nm. It was concluded that the stresses could be first diagnosed from the 3rd to 10th day after treatment and the overall accuracy of diagnosis was estimated between 25 and 75%. near-infrared spectrometer showed better and earlier detection than the other instruments investigated.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 봄 학술발표회 논문집
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• pp.343-350
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• 1999

Orthotropic steel bridge decks are potentially liable to cause fatigue cracks due to weld defects, residual stresses, and in-plane or out-of-plane stresses. In particular, the cracks propagated through deckplate in longitudinal rib to deckplate joints occur at weld toe and weld root due to stress concentrations. Numerical parametric studies are performed to show the Influence of the parameters on the stress concentration at the connection between the longitudinal rib and the deckplate. The parameters include root gap, toe angle $\theta$, toe radius $\rho$, and weld penetration. This study provides a fundamental point for the improvement of fatigue resistance and the estimation of the fatigue crack propagation in wekded joint details.

• 대한소아치과학회지
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• 제10권1호
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• pp.67-76
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• 1983

The state of pulp and dental hard tissue during the process of resorption and shedding of 104 non-carious primary teeth was assessed by histomorphologic study. The teeth were extracted from the Korean school children aged 5 to 15 and classified into preshedding, shedding, delayed shedding groups according to the age of the child at the time of extraction, The results were as follows: 1. The inflammatory cell infiltration in primary pulp tissues occurred in 61.5% of observed teeth and were increased in the order of preshedding, shedding and delayed shedding stages. 2. The odontoclasts were appeared in 43.3% of observed teeth and were increased in the order of preshedding, shedding and delayed shedding stages. 3. The polymorphonuclear leukocytes and odontoclasts couldn't be observed in the exfoliated primary pulp tissues before the process of resorption has involved the root surface about 1.8mm subjacent to the cemento-enamel junction. 4. The intact root surface was the longest and largest in the preshedding stage. 5. The resorption process of primary teeth roots occurred mainly in the stage of preshedding and shedding stages. 6. There was a tendency of repair of resorbing root surfaces in the delayed shedding stage.