• Journal of applied mathematics & informatics
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• 제39권1_2호
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• pp.31-43
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• 2021

A homogeneous circular disk undergoing a contact force is considered to investigate the thermo-elastic characteristics, and the inquiry is based on the variations of outer surface temperature and angular velocity. The intensity of stresses grows with the increase of outer surface temperature, and the circumferential strain reacts more sensitively to the change of outer surface temperature than the radial strain. In general, higher angular velocity produces; (i) larger expansion in the radial direction, (ii) smaller displacement in the circumferential, (iii) diminished intensity in the stresses. It is demonstrated that outer surface temperature and angular velocity are critical factors in the determination of thermo-elastic characteristics of homogeneous circular disks subjecting to a contact force. The results obtained can be applied on the design of a homogeneous circular cutter to promote proper and reliable thermos-elastic characteristics in service by the proper operation of these parameters.

• 상하수도학회지
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• 제30권2호
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• pp.139-145
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• 2016

Disinfection of microorganisms using UV light is widely used in the field of water supply and wastewater treatment plant, In spite of high germicidal effect and relatively clean by-product, UV disinfection has fundamental defeat that is accumulation of fouling materials at the interface of water and lamp sleeve. Non-contact type of UV photoreactor which can avoid this fouling generation was developed and the experimental performance evaluation of the system was carried out in this study. Log inactivation rate of E. coli was selected as a disinfection index. The concentration of E. coli of second clarifier effluent was $8.2{\times}10^1-8.2{\times}10^3$ colony per mL and was well inactivated by the non-contact type of UV photoreactor. Under the UV intensity condition of $2.1-2.5mW/cm^2$, E. coli removal rate was observed in the range of 54 - 95% when the HRT was increased from 10 to 52 seconds. Experimental results showed that log inactivation of E. coli was proportional to UV dosage and $200mJ/cm^2$ of UV dose is expected for the 2.0 log inactivation of E. coli from the second clarifier effluent. Between the two parameters of UV intensity and contact time which are consist of UV dose, UV intensity was 4 times more effective than contact time.

• The Korean Journal of Ecology
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• 제16권4호
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• pp.417-428
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• 1993

백목련의 가지 생장유형은 두 가지의 생장전략에 의해 이루어지는 것으로 보인가. 하나는 환경 극복 전략이고 다른 하나는 생명 유지 전략으로 구분할 수 있는데, 이러한 전략은 한 그루의 나무 안에서도 같이 일어나고 있었다. 가지의 생장율은 조도에 밀접한 관련이 있었고(P<0.001) 물리적인 접촉의 유무와도 상당히 관련(P<0.01)되어 있는 반면에 방위별로는 우의차가 없었다. 상대 조도 1%미만의 경우는 주변 가지들과 거의 물리적인 접촉으로 대부분 생장이 제한되어 있었고, 10% 초과의 경우는 접촉에 의해 생장 제한이 거의 일어나지 않았다. 가지간의 물리적인 접촉의 유무는 분지율에 영향을 미치고 있었으나(P<0.05), 분지율은 조도에 무관하고, 방위별로도 유의차가 없었다. 생장 초기에는 주가지에서 부가지로의 물질 분배비가 크게 나타났으나 나무가 자라면서 환겨의 제한을 받게 됨에 따라 분배비는 다양하고 때로는 아주 적은 값을 보이기도 하였다. 이러한 다양한 생장율, 즉 물질의분배비의 다양(0.16~0.98)은 생장과 더불어 빚어지는 제약을 극복하여 태양 에너지를 최대한 효율적으로 흡수하기 위한 가지의 배치로 해석되며, 주어진 환경하에서 백목련이 택하는 최적의 생장 전략인 것으로 생각되다.

• 한국운동역학회지
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• 제26권4호
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• pp.427-432
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• 2016

Objective: The goal of this study was to systematically investigate the postural stability of dancers by providing unexpected perturbations. Method: Six female dancers and college students participated in this study. Unpredictable wait-pull balance perturbations in the anterior direction were provided to the participants during standing. Three different perturbation intensities (low, moderate, and high intensity) were used by increasing perturbation forces. Spatial and temporal stability of postural control were measured by using margin of stability (MoS) and time to contact (TtC), respectively. Results: Both MoS and TtC at moderate intensity were significantly greater in the dancer group than in the control group, but no significant differences were found at low and high intensities between the groups. Conclusion: The present study showed spatial and temporal stability of dynamic postural control in dancers. We found that the dancers were more spatially and temporally stable than the ordinary participants in response to unexpected external perturbation when the perturbation intensity was moderate at two extreme intensity levels (low and high).

• 한국정밀공학회지
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• 제16권2호통권95호
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• pp.145-152
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• 1999

This paper presents the principle and experimental results of a non-contact surface roughness measurement by means of screen projected pattern of lase beam reflected from a polished surface. In the reflected laser beam pattern especially from a fine surface like ground or polished one, light intensity varies from the center fo the image to its boundary as the Gaussian distribution. The standard deviation of a light intensity distribution is assumed to be a good non-contact estimator for measuring the surface roughnes, because the light reflectivity is known to be well related with the surface roughness. This method doesn't need to discriminate between the specularly reflected light and the diffusely reflected one, whereas the scattered laser intensity method must do. Nor it needs to adjust the change of light intensity caused by environmental lights or specimen materials. Reflected laser beam pattern narrowly spreads out in the vertical direction to tiny scratches on the polished surface due to abrasives. The deeper the scratch the more the dispersion, which means the rougher surface. The standard deviation of the pattern is nearly in proportion to the surface roughness. Measurement errors by this method are shown to be below 10 percent compared with those obtained by a common contact method. The inclination of measuring unit from the normal axis causes the measurement errors up to 10 percent for an angle of 4 degree. Therefore the proposed method can be used as an on-the-machine quick roughness estimator within 10 percent measurement error.

• 대한치과보철학회지
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• 제31권1호
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• pp.51-61
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• 1993

The purpose of this study was to evaluate a possible occlusal contributing factor on the pathogenesis of temporomandibular joint sound by a new computer aided method for analysis of occlusal contact. 20 subjects without temporomandibular joint sound as control group and 20 subjects with temporomandibular joint sound as experimental group in the TMJ clinic, dental infirmary, School of Dentistry, Chosun University were selected so as to investigate the distribution and intensity of the bilateral occlusal contacts on silicone rubber bites in habitual intercusal position through a computer aided system. The following results were obtained : 1. The distribution and intensity of the occlusal contact could be analyzed and expressed as color density value per levels by this computer aided method. 2. There was not statistical significance between control and experimental group in total occlusal contacts. 3. There was statistical significance between control and experimental group In the total difference of right and left occlusal contacts.(P<0.05).

• E2M - 전기 전자와 첨단 소재
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• 제8권6호
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• pp.774-779
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• 1995

Process optimization experiments based on the Taguchi method were performed in order to set up the optimal process conditions for the contact oxide etching process module which was built in order to be attached to the cluster system of multi-processing purpose. In order to compare with Taguchi method, the contact oxide etching process carried out with different process parameters(CHF$_{3}$/CF$_{4}$ gas flow rate, chamber pressure, RF power and magnetic field intensity). Optimal etching characteristics were evaluated in terms of etch rate, selectivity, uniformity and etched profile. In this paper, as a final analysis of experimental results the optimal etching characteristics were obtained at the process conditions of CHF3/CF4 gas flow rate = 72/8 sccm, chamber pressure = 50 mTorr, RF power = 500 watts, and magnetic field intensity = 90 gauss.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.727-730
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• 2001

In many structures a common method of construction is to make use of bolted or riveted joints. With this type of joint the load is transmitted through a pin from one section of the structure to another. Fatigue cracks often start from the edges of holes, due to local stress concentration. In order to predict the fatigue crack growth, the stress intensity factor K for hole-edge cracks should be available. In this paper the stress intensity factors are computed for cracks in bolt-joint region considering the contact condition.

• 한국정밀공학회지
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• 제27권3호
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• pp.80-88
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• 2010

A simple computational model for modeling of subsurface crack growth under cyclic contact loading is presented. In this model, it is assumed that the initial fatigue crack will initiate in the region of the maximum equivalent stress at certain depth under the contacting surface. The position and magnitude of the maximum equivalent stress are determined by using the equivalent contact model, which is based on the Hertzian contact conditions with frictional forces. The virtual crack extension method is used for simulation of the fatigue crack growth from the initial crack up to the formation of the surface pit due to contact fatigue. The relationships between the stress intensity factor and crack length are then determined for various combinations of equivalent contact radii and loadings.

• 대한기계학회논문집A
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• 제31권3호
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• pp.380-387
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• 2007

We carried out an image analysis of living cells forming their contacts at the bottom of the cell culturing substrate. In order to visualize the contact area selectively, we adopted total-internal-reflection-fluorescence (TIRF) method, which can illuminate the specimen volume within only several hundred nano-meters above the substrate. From the fluorescent intensity of the TRF image, we could calculate the distance of the cell surface from the substrate. As a result, we visualized the origin of cell contacts, their movements, and the change of cell-contact type from the close-contact into focal-contact with information of its vertical displacement representing the temporal evolution process of the three-dimensional cell-surface-profile near the contact area during this metamorphosis.