• Structural Engineering and Mechanics
• /
• 제15권3호
• /
• pp.331-344
• /
• 2003

The plane contact problem for two infinite elastic layers whose elastic constants and heights are different is considered. The layers lying on a Winkler foundation are acted upon by symmetrical distributed loads whose lengths are 2a applied to the upper layer and uniform vertical body forces due to the effect of gravity in the layers. It is assumed that the contact between two elastic layers is frictionless and that only compressive normal tractions can be transmitted through the interface. The contact along the interface will be continuous if the value of the load factor, ${\lambda}$, is less than a critical value. However, interface separation takes place if it exceeds this critical value. First, the problem of continuous contact is solved and the value of the critical load factor, ${\lambda}_{cr}$, is determined. Then, the discontinuous contact problem is formulated in terms of a singular integral equation. Numerical solutions for contact stress distribution, the size of the separation areas, critical load factor and separation distance, and vertical displacement in the separation zone are given for various dimensionless quantities and distributed loads.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제7권3호
• /
• pp.177-182
• /
• 2007

This paper presents the see-saw type RF MEMS switch based on a single crystalline silicon structure with narrow gap vertical comb. Low actuation voltage and high isolation are key features to be solved in electrostatic RF MEMS switch design. Since these parameters in conventional parallel plate RF MEMS switch designs are in trade-off relationship, both requirements cannot be met simultaneously. In the vertical comb design, however, the actuation voltage is independent of the vertical separation distance between the contact electrodes. Therefore, the large separation gap between contact electrodes is implemented to achieve high isolation. We have designed and fabricated RF MEMS switch which has 46dB isolation at 5GHz, 0.9dB insertion loss at 5GHz and 40V actuation voltage.

• 대한치과보철학회지
• /
• 제34권3호
• /
• pp.632-649
• /
• 1996

The purpose of this study was to examine, by the method of 3-dimentional finite element analysis. how infraocclusion affected the stress distribution in surrounding bone and osseointegrated prosthesis. The 3-dimentional finite element mandibular models were made, in which the first and second molars were removed and the two osseointegrated implants were placed in the first and second molar sites and implant supported fixed prostheses were constructed. Analysis of equivalent stress and displacement induced by strong occlusion or infraocclusion was performed under vertical or inclined distributed loads. The results were as follows; 1. Under vertical load of 50N or 500N, the model in which infraocclusion had not been allowed showed greater stress on implants and the supporting bone than on natural teeth. 2. In the model in which infraocclusion of $30{\mu}m$ had been allowed, implant-prosthesis on the molars had no contact with opposing teeth under vertical load of 50N, However with the same allowed infraocclusion and the model under vertical load of 500N, implant prosthesis on the second molar had contact with opposing teeth, and stress distribution occured properly on natural teeth and implants. 3. Under $45^{\circ}$ inclined load, the model in which infraocclusion had not been allowed showed greater stress on implants and the supporting bone than on natural teeth. There was greater stress in the case of $45^{\circ}$ inclined load than in the case of vertical load. 4. Under $45^{\circ}$ inclined load of 50N or 500N, the model in which infraocclusion of $30{\mu}m$, had been allowed showed no occlusal contact on the implants and occlusal contact on the natural teeth. 5. In partially edentulous cases with implant supported prosthesis, we can prevent excessive load on implants by allowing infraocclusion.

• Journal of Oral Medicine and Pain
• /
• 제23권2호
• /
• pp.143-155
• /
• 1998

This study was performed to investigate the factor that might affect mandibualr body rotation. For the study, 115 patients with temporomandibular disorders and 35 dental students without angy signs and symptoms of temporomandibular disorders were randomly selected as the patient group and the contreol group, respectively. Preferred chewing side, Angle' classification, lateral guidance pattern, and affected side were clinically recorded, and the amount of Mandibular body rotational torque movement was measured in wide opening and closure, in right and left excursion with vertical and lateral distance in frontal plane, right and left rotational angel in horizontal and in frontal plane. Masticatory muscle activity of anteriorocclusal contact pattern on maximal hard biting were also observed synchronously with BioEMG and T-Scan , respectively. The observed items were muscle activity of anterior temporalis and superficial masseter, and tooth contact status related to contact number, force, duration, and occlusal unbalance between right and left arch. The data collected were analyzed by SAS statistical program. The results of this study were as follows : 1. Mean value of vertical distance in frontal plane in wide opening and closure was more in control subjects than in patients, but there was no difference for rotational angle. In right excursion, rotational angles were greater in patient group than in control group. 2. Comparison among the subjects by preferred chewing side did not reveal any significant difference, but comparison among patients by affected side showed more rotational amount in bilaterally affected patients than in unilaterally affected patients. 3. Comparison among the subjects by Angle's classification or lateral guidance pattern revealed no difference. There was also no difference between preferred chewing side and contralateral side, and between affected side and contralateral side. 4. Positive correlation in madibular rotational torque movements were observed among vertical distance, total horizontal rotation angle, electromyographic activity of anterior temporalis, tooth contact number, and tooth contact force but total frontal rotation angle almost did not show any correlation with other variables except vertical distance.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회A
• /
• pp.1730-1733
• /
• 2007

As semiconductor and MEMS devices become smaller, testing process during their production should follow such a high density trend. A circuit inspection tool "probe card" makes contact with electrode pads of the device under test (DUT). Nowadays, electrode pads are irregularly arranged and have height difference. In order to absorb variations in the heights of electrode pads and to generate contact loads, contact probes must have some levels of mechanical spring properties. Contact probes must also yield a force to break the surface native oxide layer or contamination layer on the electrodes to make electric contact. In this research, new vertical micro contact probe with bellows shape is developed to overcome shortage of prior work. Especially, novel bellows shape is used to reduce stress concentration in this design and stopper is used to change the stiffness of micro contact probe. Variable stiffness can be one solution to overcome the height difference of electrode pads.

• 펄프종이기술
• /
• 제48권3호
• /
• pp.5-13
• /
• 2016

This study investigated the effects of different factors on the migration of a fluorescent whitening agent (FWA) from paper treated with FWAs to non-fluorescent papers. FWA migration experiments were carried out in vertical and friction contacts between the papers dyed with FWAs and non-fluorescent papers. During the experiments, we identified the effects of the addition and types of FWAs, contact time, temperature, and relative humidity (RH) on FWA migration. The fluorescence indices of the non-fluorescent papers were measured before and after the migration experiments, and the Student's t test, a statistical tool, was utilized to compare results from different migration experiments. In vertical contact experiments, FWA migration to non-fluorescent paper was observed at $30^{\circ}C$ and 70% RH; this was attributed to the high moisture content of the paper. FWA migration did not occur significantly at $23^{\circ}C$ and 50% RH. In the friction contact experiments, FWA migrations were identified at both temperature conditions and RH percentages. The addition and types of FWAs did not increase the fluorescence index of non-fluorescent papers. Therefore, it was concluded that the moisture content of paper and the friction contact affected FWA migration from the papers containing internal and surface FWAs.

• 마이크로전자및패키징학회지
• /
• 제22권4호
• /
• pp.71-76
• /
• 2015

최근 Light Emitting Diode (LED)의 효율을 높이기 위한 연구가 활발히 진행 되고 있다. 특히 소자 측면에서는 수평형 LED, 수직형 LED, via-hole 구조의 수직형 LED 등의 다양한 구조가 제시되었다. 본 논문에서는 시뮬레이션을 통해 via-hole 구조의 수직형 LED의 새로운 전극 디자인을 제시하였다. 기존 Via-hole 구조의 수직형 LED의 n-contact hole 주변에 전류가 밀집되는 문제점을 해결하면서 유효 발광면적을 극대화 시켜 소자 전체에 균일한 전류를 주입할 수 있는 소자 디자인에 대해 평가하였다. 시뮬레이션 결과를 바탕으로 최적의 전극 디자인을 실제 디바이스로 제작하여 기존의 via-hole 구조의 수직형 LED와 비교 분석하였다. 최적화된 디자인이 적용된 via hole type 수직형 LED의 경우 기존 디자인에 비해 350 mA 주입시 약 0.2 V의 Forward Voltage 감소하였지만 광 출력은 비슷하여 최종적으로 4.2%의 WPE (Wall plug efficiency)가 향상됨을 보였다.

• 대한기계학회논문집B
• /
• 제21권9호
• /
• pp.1165-1173
• /
• 1997

The steady state close-contact melting phenomenon occurring between a phase change material and an isothermally heated flat plate with relative motion is investigated analytically, in which the effects of vertical convection in the liquid film and solid-liquid density difference are incorporated simultaneously. Not only the scale analysis is conducted to estimate a priori qualitative dependence of system variables on characteristic parameters, but also an analytical solution to a set of simplified model equations is obtained to specify the effects under consideration. These two results are consistent with each other, in that the vertical convection affects both the solid descending velocity and the film thickness, and that the density difference alters only the solid descending velocity. While the effect of vertical convection can be characterized conveniently by a newly introduced temperature gradient factor which asymptotically approaches the unity/zero with decreasing/increasing the Stefan number, that of density difference is represented by the liquid-to-solid density ratio. It is shown that the solid descending velocity depends linearly on the density ratio, and that the ratios of solid descending velocity, film thickness and friction coefficient to the conduction solution are proportional to 3/4, 1/4 and -1/4 powers of the temperature gradient factor, respectively. Also, established is the fact that the effect of convection can be legitimately neglected in the analysis for the range of the Stefan number less than 0.1.

• 한국안광학회지
• /
• 제19권3호
• /
• pp.285-293
• /
• 2014

목적: 초등학생에서 일반인을 대상으로 가시홍채직경(수평, 수직) 및 검열의 폭과 길이를 측정하여 이들의 상관관계 및 소프트콘택트렌즈 크기의 연령별 적합성을 알아보고자 하였다. 방법: 안질환이 없고 외형적으로 미용을 포함한 눈 수술을 하지 않은 초등학생에서 일반인 총 514명(1028안)을 대상으로 가시홍채직경(수평, 수직)과 검열의 폭과 길이를 측정하고 분석하였다. 결과: 가시홍채수평직경과 수직직경은 연령별 남녀 간의 유의한 차이는 없었으나, 중학생과 대학생의 검열의 길이와 고등학생의 검열의 폭은 남학생과 여학생 간 유의한 차이가 있었다(p<0.05). 또한, 남녀 모두 가시홍채수평직경, 가시홍채수직직경, 검열의 길이 그리고 검열의 폭에서 연령별로 유의한 차이를 보였다. 가시홍채직경과 검열의 크기는 문헌에 기준한 정상범위 근사치보다 검열의 폭은 남녀를 포함한 전체 대상자의 27.9%, 가시홍채직경은 36.0%가 작은 것으로 나타났다. 결론: 가시홍채직경과 검열의 크기는 소프트콘택트렌즈의 직경 결정에 영향을 미치며, 특히 렌즈 삽입시 피검자의 불편함을 덜어주기 위해서 좀 더 세심하게 고려되어야 할 사항이라고 사료된다.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2005년도 추계종합학술대회
• /
• pp.953-956
• /
• 2005

Low voltage actuation and high isolation characteristics are key features to be solved in electrostatic RF switch design. Since these parameters in the conventional parallel plate MEMS switch design are in trade-off relation, both requirements cannot be met simultaneously. In vertical comb design, however, the actuation voltage is independent to the vertical separation distance between the contact electrodes. Then, we can design the large separation distance between contact electrodes to get high isolation. We have designed an RF MEMS switch which has -40dB isolation at 5 GHz and 6 V operation voltages. The characteristics of the fabricated switch are being evaluate.