• 한국안광학회지
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• 제13권3호
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• pp.45-50
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• 2008

목적: 본 연구는 천연항균물질인 나린진을 소프트 콘택트렌즈 수지용액에 첨가하여 소프트 콘택트렌즈를 제조하고, 제조된 콘택트렌즈에서 용출된 용액의 광학적 특성과 나린진의 물리화학적인 상태 그리고 식염수에서의 용출 특성 등에 대해 살펴보고자 하였다. 방법: 나린진이 첨가된 콘택트렌즈는 벌크(bulk)중합 방식을 이용하여 제조하였고, 제조된 나린진이 첨가된 콘택트렌즈에서 나린진의 결합상태와 식염수로의 나린진 용출과정, 그리고 시간에 따른 나린진의 용출량 등은 적외선 스펙트럼(IR spectrum)과 고성능 액체 크로마토그래피(HPLC)를 이용하여 살펴보았다. 결과: 나린진이 첨가된 콘택트렌즈에서 나린진의 용출은 일정농도를 유지하면서 약 1개월 동안 지속되었고, 용출된 나린진은 첨가하기 전과 동일한 구조를 유지하고 있었으며 투과율과 같은 광학적 특성 변화는 관찰할 수 없었다. IR spectrum과 HPLC 결과로부터 콘택트렌즈 내에서 나린진의 구조와 결합상태를 확인하였다. 결론: 나린진이 첨가된 콘택트렌즈에서 나린진은 폴리머 분자와 반데르발스(van der Waals) 인력이나 나린진 분자의 수산기 (hydroxyl group)와 약한 수소결합(hydrogen bonding)에 의해 상호 결합되어 있는 것으로 판단되었다. 나린진이 첨가된 콘택트렌즈로부터 나린진은 약 1개월 동안 일정농도씩 꾸준히 용출되었으며 1개월 후에도 하루 동안 용출된 나린진의 농도가 약 10 ppm으로 나타나 일정기간 동안 항균력의 유지가 지속적으로 필요한 소프트 콘택트렌즈의 제조에 나린진을 첨가하는 방법이 매우 효과적임을 알 수 있었다.

• 환경위생공학
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• 제14권4호
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• pp.41-49
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• 1999

The water treatment by was performed to remove VOC and organic substances in the multi-stage ozone contactor. Ozone is mainly utilized to change the chemical structures of organic substance, of which finally has the purpose to degrad them. The removal efficiency of VOC has 20~60% at the ozone concentration of 3 ppm, in case of trichloroethylene, its efficiency is reduced by 85% at the ozone contact time of 8 min. Design factors such as the number of stage, ozone concentration, zone contact time are determined for optimal treatment in the multi-stage contactor.

• Computers and Concrete
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• 제26권2호
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• pp.107-114
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• 2020

In this study, a two dimensional model of receding contact problem has been analyzed using finite element method (FEM) based software ANSYS and ABAQUS. For this aim finite element modeling of elastic layer and two homogeneous, isotropic and symmetrical elastic quarter planes pressed by means of a rigid circular punch has been presented. Mass forces and friction are neglected in the solution. Since the problem is examined for the plane state, the thickness along the z-axis direction is taken as a unit. In order to check the accuracy of the present models, the obtained results are compared with the available results of the open literature as well as the results of two software are compared using Root Mean Square Error (RMSE) and good agreements are found. Numerical analyses are performed considering different values of the external load, rigid circular radius, quarter planes span length and material properties. The contact lengths and contact stresses of these values are examined, and their results are presented. Consequently, it is concluded that the considered non-dimensional quantities have noteworthy influence on the contact lengths and contact stress distributions, additionally if FEM analysis is used correctly, it can be an efficient alternative method to the analytical solutions that need time.

• Structural Engineering and Mechanics
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• 제44권1호
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• pp.61-72
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• 2012

The paper is on contact analysis of a spherical ball with a deformable flat, considering the effect of tangent modulus on the contact parameters of a non-adhesive frictionless elastic-plastic contact. The contact analysis of this model has been carried out using analysis software Ansys and Abaqus. The contact parameters such as area of contact between two consecutive steps, volume of bulged material are evaluated from the formulated equations. The effect of the tangent modulus is considered for determining these parameters. The tangent modulus are accounted between 0.1E and 0.5E of materials E/Y value greater than 500 and less than 1750. Result shows that upto an optimal tangent modulus values the elastic core push up to the free surface in the flat. The simulation is also carried out in Abaqus and result provide evidence for the volume of bulged material in the contact region move up and flow into the free surface of the flat from the contact edge between the ball and flat. The strain energy of the whole model is varied between 20 to 40 percentage of the stipulated time for analysis.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.188-191
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• 1997

In the recent sheet metal forming simulations, it increases to adopt the dynamic explicit method for an effective computation and the elastic-plastic formulation for stress recovery. It is inevitable in the dynamic explicit method that some noises occur and sometimes partly spoil results of simulations. It is severer when complicated contact conditions are included in simulations. An effective method to control these noises is introduction of damping effects. In this paper, the concept of contact damping is introduced in order to suppress noises due to complicated contact conditions. This is checked by analyzing a simple sheet metal forming process(U-bending). From the computational results, it is shown that the contact damping can effectively control the noises due to contacts and develop more reliable internal stress states.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.144-149
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• 2008

A transient finite element simulation is developed for the two-dimensional stationary elastoplastic layer between sliding layers, to investigate thermoelastoplastic instability(TEPI) due to frictional heating in the material. The analysis will show some differences between the case of thermoelastic instability and TEPI, especially according to the contact pressure above yield stress. A transient behavior of contact pressure is captured to explain the behavior of thermoplasticity of contact with different sliding velocity. The instability of contact pressure in the long range of braking time will be explored to understand the generation mechanism of hot spots.

• Smart Structures and Systems
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• 제18권4호
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• pp.643-662
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• 2016

The monitoring of structural integrity of pipeline tapered thread connections is of great significance in terms of safe operation in the industry. In order to detect effectively the loosening degree of tapered thread connection, an active sensing method using piezoceramic transducers was developed based on time reversal technique in this paper. As the piezoeramic transducers can be either as actuators or sensors to generate or detect stress waves, the energy transmission for tapered thread connection was analyzed. Subsequently, the detection principle for tapered thread connection based on time reversal was introduced. Finally, the inherent relationship between the contact area and tightness degree of tapered thread connection for the pipe structural model was investigated. Seven different contact area scenarios were tested. Each scenario was created by loosening connectors ranging from 3 turns to 4.5 turns in the right tapered threads when the contact area in the left tapered threads were 4.5 turns. The experiments were separately conducted with a highly noisy environment and various excitation signal amplitudes. The results show the focused peaks based on time reversal have the monotonously rising trend with the increase of the contact areas of tapered threads within an acceptable monitoring resolution for metal pipes. Compared with the energy method, the proposed time reversal based method to monitor tapered threads loosening demonstrates to be more robust in rejecting noise in Structural Health Monitoring (SHM) applications.

• 대한안전경영과학회지
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• 제19권1호
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• pp.211-217
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• 2017

In this study, we investigated to the heat transfer performance of coating nano-structure with various shapes and patterns on the heat transfer surface. As a result of the measurement of the 3D nano shape, it was confirmed that the roughness generally increases when the adhesive is sprayed on the coating surface and finished durability experiment. In the case of TEOS adhesive, the roughness increased by $0.074{\mu}m$, $0.012{\mu}m$ and $0.015{\mu}m$, and the contact angle decreased $12.64^{\circ}$, $1.31^{\circ}$, $9.84^{\circ}$ at the coating time of 120 seconds, 180 seconds and 240 seconds, respectively. In the case of PVA adhesive, the roughness increased by $0.069{\mu}m$, $0.056{\mu}m$ and $0.03{\mu}m$, and the contact angle decreased $2.85^{\circ}$, $4.82^{\circ}$, $6.96^{\circ}$ at the coating time of 120 seconds, 180 seconds and 240 seconds, respectively. In the case of DGEBF adhesive, the roughness increased by $0.042{\mu}m$, $0.053{\mu}m$ and $0{\mu}m$, and the contact angle decreased $0.81^{\circ}$ at the coating time of 120 seconds, increased $4.82^{\circ}$, $6.96^{\circ}$ at the coating time of 180 seconds and 240 seconds, respectively. As a result, the durability tends to decrease as more nano-structures are deposited, and 3D nano shapes, contact angles and SEM photographs showed that the performance of the PVA adhesive was superior among the three adhesives.

• 한국산림과학회지
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• 제83권1호
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• pp.32-37
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• 1994

리기다소나무와 잣나무 유묘에 인위적으로 산도를 조절한 인공산성우(pH 3.0, 4.0 및 5.0)와 지하수(pH 6.5)를 1992년 4월부터 1993년 8월까지, 생육기간 중에는 주 2회, 겨울철은 주 1회 1회 5mm의 강도로 처리하였다. 인공산성우를 처리하면서 수종별 침엽의 접촉각(contact angle)을 조사 비교하여 얻은 결과는 다음과 같다. 침엽의 표면과 물방울이 이루는 접촉각을 측정한 결과, 처리산성우의 산도수준이 높을수록 엽령이 높을수록 접촉각의 크기는 낮아졌다. 침엽의 접촉각을 측정 비교하는 방법은 야외에서 침엽수류에 대한 산성우 피해의 조기판단을 위한 매우 효과적인 기준이라 판단된다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.1336-1341
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• 2011

The pantograph-overhead contact line system is an interface that supplies power to high-speed trains used in many countries including Korea. Due to the fact that power is supplied through direct contact between contact wires and contact strips, wear may occur, increasing the possibility of accidents over periods of time. Therefore, there is a need to establish methods of effectively extracting safety related parameters. In this paper, an image processing based method that calculates and draws graphs of a pantograph's dynamic stagger is proposed. To assess reliability, the results were compared with data collected from conventional maintenance vehicles.