• 한국안광학회지
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• 제12권4호
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• pp.119-125
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• 2007

본 연구는 콘택트렌즈 착용자와 안경 장용자 그리고 정시안의 대비감도를 비교하기 위해 시행되었다. 조사 대상은 만 19-26세로 근시 70안과 정시 30안을 대상으로 시행하였다, 근시안 그룹은 안경장용자 48안과 콘택트렌즈 착용자 22안으로 모두 교정시력이 1.0 이상인 안구를 대상으로 시행하였다. 공간 대비감도는 EyeView$^{(R)}$ Functional Vision Analysis software가 포함된 Optec 6500 Vision Tester$^{(R)}$ (Stereo Optical. USA)을 이용하여 Photopic (85cd)과 mesopic (3cd) 상태에서 대비 감도를 조사하여 비교하였다. 안경장용자는 정시안과 비교하여 모든 조건에서 대비감도에서 의의 있는 차이가 없었다. 소프트 콘택트렌즈 착용자는 정시안에 비해 1.5와 12cpd에서 통계적으로 낮은 대비감도를 보였다. 본 연구의 콘택트렌즈 착용자에서 대비감도가 낮게 나온 것은 콘택트렌즈 착용자의 각막 병리로 진행하기 전단계에서 나타나는 각막 문제의 증거로 해석될 수도 있다. 이러한 대비감도 검사는 소프트렌즈 콘택트렌즈 평가하는데 유용한 방법이 될 수 있는 것으로 사료된다.

• PNF and Movement
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• 제6권1호
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• pp.21-25
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• 2008

Purpose : The purpose of this study was conducted to find out observation at gait analysis of the stroke patient with proprioceptive neuromuscular facilitation(PNF) concept. Methods : This is a literature study with books, seminar note and international PNF course book. Results : Stroke patient gait was poor initial contact by weakness of tibialis anterior or weakness of contralateral plantar flexor, poor loading response by loss of deep sensation, poor mid stance by loss of deep sensation, weakness of tibialis anterior and weakness of plantar flexors eccentric control, poor terminal stance, pre-swing, initial swing by loss of deep sensation and stiffness fo deep toe flexors. Conclusion : Stroke patient gait determine on loss of mobility, pain, fear, trunk muscle weakness, loss of coordination, loss of deep sensation, neglect and apraxia. Therefore observational gait analysis of the stroke patient focus on gait cycle and take out hypotheses from the gait cycle. These hypotheses have to define accept or not by parameters. Treatment plan made with the hypotheses.

• 한국자동차공학회논문집
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• 제11권2호
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• pp.96-103
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• 2003

In this paper, the heat loss to the constant volume vessel wall was investigated using instantaneous heat flux sensor, schlieren visualization, pressure rise curve. And the heat loss characteristics of plasma jet ignition were compared with conventional spark ignition. In case of plasma jet ignition, the flame kernel moves toward the center of combustion vessel in the initial period of combustion, and the flame surface spread out to the vessel wall. However, in case of conventional spark ignition, the flame surface contact with combustion vessel wall in the initial period of combustion. As a result, heat loss in the combustion duration for conventional spark ignition increase faster than that of plasma jet ignition. And the combustion enhancement rate of plasma jet ignition is higher than that of conventional spark ignition, and it was found that the heat loss rate is inversely proportional to the combustion enhancement rate.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.551-555
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• 2010

Electrowetting is a versatile tool to handle tiny droplets and forms a backbone of digital microfluidics. Numerical analysis is necessary to fully understand the dynamics of electrowetting, especially in designing electrowetting-based devices, such as liquid lenses and reflective displays. We developed a numerical method to analyze the general contact-line problems, incorporating dynamic contact angle models. The method is based on the conservative level set method to capture the interface of two fluids without loss of mass. We applied the method to the analysis of spreading process of a sessile droplet for step input voltages and oscillation of the droplet for alternating input voltages in electrowetting. The result was compared with experimental data. It is shown that contact line friction significantly affects the contact line motion and the oscillation amplitude. The pinning process of contact line was well represented by including the hysteresis effect in the contact angle models. In level set method, in the mean time, material properties are made to change smoothly across an interface of two materials with different properties by introducing an interpolation or smoothing scheme. So far, the weighted arithmetic mean (WAM) method has been exclusively adopted in level set method, without complete assessment for its validity. We viscosity, thermal conductivity, electrical conductivity, and permittivity, can be an alternative. I.e., the WHM gives more accurate results than the WAM method in certain circumstances. The interpolation scheme should be selected considering various characteristics including type of property, ratio of property of two fluids, geometry of interface, and so on.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.250-253
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• 2007

An evaporated Ti/Pd/Ag contact system is most widely used to make high-efficiency silicon solar cells, however, the system is not cost effective due to expensive materials and vacuum techniques. Commercial solar cells with screen-printed contacts formed by using Ag paste suffer from a low fill factor and a high shading loss because of high contact resistance and low aspect ratio. Low-cost Ni and Cu metal contacts have been formed by using electroless plating and electroplating techniques to replace the Ti/Pd/Ag and screen-printed Ag contacts. Ni/Cu alloy is plated on a silicon substrate by electro-deposition of the alloy from an acetate electrolyte solution, and nickel-silicide formation at the interface between the silicon and the nickel enhances stability and reduces the contact resistance. It was, therefore, found that nickel-silicide was suitable for high-efficiency solar cell applications. The Ni contact was formed on the front grid pattern by electroless plating followed by anneal ing at $380{\sim}400^{\circ}C$ for $15{\sim}30$ min at $N_{2}$ gas to allow formation of a nickel-silicide in a tube furnace or a rapid thermal processing(RTP) chamber because nickel is transformed to NiSi at $380{\sim}400^{\circ}C$. The Ni plating solution is composed of a mixture of $NiCl_{2}$ as a main nickel source. Cu was electroplated on the Ni layer by using a light induced plating method. The Cu electroplating solution was made up of a commercially available acid sulfate bath and additives to reduce the stress of the copper layer. The Ni/Cu contact was found to be well suited for high-efficiency solar cells and was successfully formed by using electroless plating and electroplating, which are more cost effective than vacuum evaporation. In this paper, we investigated low-cost Ni/Cu contact formation by electroless and electroplating for crystalline silicon solar cells.

• Geomechanics and Engineering
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• 제8권4호
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• pp.477-493
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• 2015

In rock drilling, the most important characteristic to clarify is the wear of the drill bits. The reason that the rock drill bits fail with time is wear. In dry sliding contact adhesive wear deteriorates the materials in contact, quickly, and is the result of shear fracture in the momentary contact joins between the surfaces. This paper aims at presenting an overview of the assessment of WC/Co cemented carbide (CC) tricone bit in rotary drilling. To study wear of these bits, two approaches have been used in this research. Firstly, the new bits were weighted before they mounted on the drill rigs and also after completion their useful life to obtain bit weight loss percentage. The characteristics of the rock types drilled by using such this bit were measured, simultaneously. Alternatively, to measure contact wear, namely, matrix wear a micrometer has been used with a resolution of 0.02 mm at different direction on the tricone bits. Equivalent quartz content (EQC), net quartz content (QC), muscovite content (Mu), coarseness index (CI) of drill cuttings and compressive strength of rocks (UCS) were obtained along with thin sections to investigate mineralogical properties in detail. The correlation between effective parameters and bit wear were obtained as result of this study. It was observed that UCS shows no significant correlation with bit wear. By increasing CI and cutting size of rocks wear of bit increases.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.515-518
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• 2006

This paper presents the friction and wear characteristics of contact type sealing unit for a water turbine of a small hydro-power generation, which Is to stop a leakage of a circulating water from a outside of an impeller to an inside of a rolling bearing. The surface wear strongly affect to the seal life of a mechanical face seal. In this study, the hardness of a stainless steel in which is a heat-treated is 892.8 in Vickers hardness and the hardness of silicone carbide of SiC is 714.1 in Vickers hardness. The surface hardness of a heat-treated stainless steel is 25% high compared with that of a ceramic material of SiC. The contact modes of rubbing surfaces aye a dry friction a water film friction and a mixed friction that is contaminated by a dust, silt and moistures, etc. These two factors of a contact rubbing modes and a material property are very important parameters on the tribological performance such as a friction and wear between a seal ring and a seal seat. The experimental result shows that the surface hardness of a seal material is very important on the friction coefficient and a wear volume. Thus, the results recommend higher hardness of a seal material, which may reduce a friction loss and increase a wear life of primary seal components

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.679-685
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• 2001

In this paper, the dynamic response of the pantograph system that supplies electrical power to a high-speed rail vehicle were investigated. The analysis of the catenary based on the Finite Element Method (FEM) is executed to develop a pantograph fits well in high-speed focused on the dynamic characteristic analysis of the pantograph system. By simulation of the pantograph-catenary system, the static deflection of the catenary, the stiffness variation in contact lines, the dynamic response of the catenary undergoing constant moving load and the contact force analysis were executed. In order to consider the design variables that effects on the dynamic characteristic of the pantograph system performed the dynamic sensitivity analysis. From the pantograph-catenary analysis, the design parameters of a pantograph could be improved. From the results of the sensitivity analysis, a pantograph with improved parameters is suitable for a high-speed rail vehicle from the design-parameter analysis.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.154-155
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• 2007

PRAM(Phase-Change RAM) is a promising memory that can solve the problem of conventional memory and has the nearly ideal memory characteristics. We reviewed the issues for high density PRAM integration. Writing current reduction is the most urgent problem for high density PRAM realization. So, we studied new constitution of $Ge_1Se_1Te_2$ chalcogenide material and presented the method of reducing the contact size between $Ge_1Se_1Te_2$ and electrode. A small-contact-area electrode is used primarily to supply current into and minimize heat loss from the chalcogenide. In this letter, we expect the method of reducing the contact size between $Ge_1Se_1Te_2$ and electrode to decrease writing current.

• 조명전기설비학회논문지
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• 제15권2호
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• pp.64-72
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• 2001

본 논문에서는 비접촉 충전 에너지 전달을 위한 포워드 ZVS MRC(Zero Voltage Switching Multi Resonant Converter)를 제안하였다. 포워드 ZVS MRC는 기생성분을 흡수하는데 그리고 스위칭손실을 최소화하는데 효과적이다. 이것은 높은 주파수동작에 적합하며 따라서 이것을 비접촉 충전에너지 전달에 적용하였다. 사용된 컨버터는 분리형 트랜스포머와 동기식정류기를 이용하였다. 갭의 크기에 따른 결합계수(k), 누설인덕턴스, 결합인 덕턴스 그리고 공진 주파수를 측정하였다. 구해진 값을 이용하여 회로를 설계, 구현하였으며 제안된 회로는 PSPICE로 시뮬레이션하였고 실험하였다. 주스위치의 전압 스트래스와 출력전력을 측정하였으며 제안된 컨버터가 비접촉 충전 에너지 전달에 적합함을 보였다.