• 대한치과보철학회지
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• 제41권4호
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• pp.503-518
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• 2003

Statement of problem : There have been previous studies about considerable variations in machining accuracy and consistency in the implant-abutment-screw interfaces. Purpose : The purpose of this study was to evaluate the machining accuracy and consistency of implant/abutment/screw combinations on two randomly selected implants from each of four manufactures. Material and methods : In this study, screws were respectively used to secure a cemented abutment, to a hexlock implant fixture ; teflon coated titanium alloy screw(Torq-Tite) and titanium alloy screw in Steri--Oss system, gold-plated gold-palladium alloy screw(Gold-Tite) and titanium alloy screw in 3i system gild screw ana titanium screw in AVANA Dental Implant system, and titanium screws in Paragon System. The implants were perpendicularly mounted in polymethyl methacrylate autopolymerizing acrylic resin block(Orthodontic resin, Densply International Inc. USA) by use of dental surveyer. Each abutment screw was secured to the implant with recommended torque value using a digital torque controller. Each screw was again tightened after 10 minutes. All samples were cross sectioned with grinder-polisher unit(Omnilap 2000 SBT Inc) after embeded in liquid unsaturated polyester (Epovia, Cray Valley Inc) Results : There were the largest gaps in the neck areas of screws in hexagonal extension implants which were examined in this study. The leading edge of the abutment screw thread (superior surface) was in contact with the implant body thread, and the majority of the contacting surfaces were localized to the middle portion of the mating threads. Considerable variation in the contacting surfaces was noted in the samples evaluated. Amounts of contact in the abutment screw thread were larger for assemblies with Gold-Tite screw, gold alloy screw. Torq-Tite screw than those with titanium screws. The findings of intimate contact between the screw and screw seat were seen in all samples, regardless of manufacturers. However, microgap between the head and lateral neck surface of the screw and the abutment could be dectected in all samples. The findings of intimate contact between the platform of the implant and the bottom of the abutment were consistent in all samples, regardless of manufacturers. However, microgaps between the lateral surface of external hex of the fixture and the abutment could be dectected in all samples. Conclusion : Considerable variations in machining accuracy and consistency were noted in the samples and the implant-abutment-screw interfaces were incomplete. From the results of this study, further development of the system will be required, including improvements in pattern design.

• 한국환경농학회지
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• 제20권3호
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• pp.143-149
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• 2001

침전지를 갖는 접촉산화수로 시스템을 이용한 수질 정화효과를 2000년 9월부터 11월까지 조사하였다. 본 시스템은 노즐로 폭기하여 플라스틱여재의 표면에서 오염물질과 공기를 접촉시켜 물을 정화하기 위한 시설이다. 1차 침전지의 수리학적 체류시간은 60분이며, 여기에서는 물속에 있는 오염물이 침전되고 침전물은 바닥에 설치한 배수암거로 배출되도록 설계하였다. 산화수로의 유량, 수리학적 체류시간, 길이는 각각 $200\;m^3/day$, 90 min, 20 m이다. 산화수로에는 플라스틱 접촉여재를 채웠다. 탈질소를 위한 무산소 조건이 확보되지 않았기 때문에 T-N의 처리효율은 다른 수질항목에 비해 낮았다. 그러나 이 처리시스템에서 SS는 $25.0%{\sim}89.6%$, BOD는 $75.0%{\sim}91.5%$, T-P는 $44.3%{\sim}95.3%$의 처리효율을 나타냈다. 이 실험의 결과는 본 연구에서 고안된 침전접촉 산화수로 시스템의 저수지나 수로에서의 수질정화 가능성을 보여주고 있다.

• Journal of Biosystems Engineering
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• 제26권5호
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• pp.461-468
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• 2001

Impact between fruits and other materials is a major cause of product damage in harvesting and handling systems. The oriental pears are more susceptible to bruising than other fruits such as European pears and apples, and are required more careful handling. The interest in the handling of the pears for the processing systems has raised the question of the allowable drop height to which pears can be dropped without causing objectionable damage. Drop tests on pears were conducted using an impact device developed by authors to estimate the allowable drop height without bruising. The impact device was constructed to hold in a selected orientation and to release a fruit by vacuum for dropping on to a force transducer. The drop height was adjustable for zero to 60 cm to achieve the desired distance between the bottom of the fruits and the top of the impact force transducer. The transducer was secured to 150 kg$\sub$f/ concrete block. The transducer signal was sampled every 0.17 ms with a strain gage measurement board in the micro computer where it was digitaly stored for later analysis. The selected sample fruit was Niitaka cultivar of pears which is one of the most promising fruit for export in Korea. The pears were harvested during the 1998 harvest season from an orchard in Daejeon. The sample fruit was selected from two groups which were stored for 3 months and 5 months respectively by the method of current commercial practice. The pears were allowed to stabilize at environmental condition(18$^{\circ}C$, 65% rh) of the experimental room. One hundred fifty six pears were tested from the heights of 5, 7.5. 10 and 12.5 cm while measurement were made of impact peak force, contact time, time to peak force, dwell time, pear diameter and mass. The bioyield strength and modulus of elasticity were measured using UTM immediately after each drop test. The allowable drop height was estimated on the base of bioyield strength of the pears in two ways. One was assumed the peak force during impact test increasing linearly with time, and the other was based on the actual drop test results. The computer program was developed for measuring the impact characteristics of the pears and analyzing the data obtained in the study. The peak force increased while contact times decreased with increasing drop height and contact times of the sample from the hard tissue group. The allowable drop height increased with increasing bioyield strength and contact times, and also varied with Poisson\`s ratio, mass and equilibrium radius of the pears. The allowable drop height calculated by a theoretical method was in the range from 1 to 4 cm, meanwhile, the estimated drop height considering the result of the impact test was in the range from 1 to 6 cm. Since the physical properties of fruits affected significantly the allowable drop height, the physical properties of the fruits should be considered when estimating the allowable drop height.

• 스마트미디어저널
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• 제4권1호
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• pp.9-15
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• 2015

언어를 사용하지 않고 몸짓이나 손짓, 표정 등 신체의 동작으로 의사나 감정을 표현하고 전달하는 비언어적 전달 방법은 중요한 의사전달 방법 중 하나이다. 이러한 몸짓이나, 손짓, 시선 맞춤 그리고 손동작은 때론 말보다 더 강력한 의사전달의 방법으로 작용한다. 비언어적 의사전달 방법에서 시선 맞춤은 그중에서도 가장 중요한 의사전달 방법이다. 하지만 화상회의를 할 때 디스플레이 상에서의 눈과 카메라의 차이 때문에 상호간에 시선 맞춤이 되지 않는다. 만약 상호간에 시선 맞춤을 하지 않고 대화를 하면 정확한 의사전달이 힘들고 서로의 이야기에 집중하기 어려워진다. 본 논문에서는 화상회의 상황에서 시선 맞춤을 개선하는 방법을 제안한다. 시선 맞춤을 개선하기 위해 두 대의 카메라를 텔레비전의 위, 아래에 설치하였다. 동시에 두 영상을 촬영하여 2D 워핑을 하여 가상의 중간시점으로 옮기고, 뷰 모핑을 한다. 모핑된 얼굴과 배경영상을 합성하여 화상회의를 위해 개선된 시선 맞춤 영상을 만든다. 실험 결과를 통하여 제안한 알고리즘이 시선 맞춤을 개선하고 자연스러운 중간 시점 영상을 합성하는 것을 확인 할 수 있다.

• 한국운동역학회지
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• 제22권4호
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• pp.387-394
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• 2012

The purpose of this study was to compare and analyze the finger pressure and kinematic variables in the forehand hairpin net shot between skilled elite players and less skilled recreational players. Eight elite players(age: $18.1{\pm}0.8yrs$, height: $176.8{\pm}1.5cm$, weight: $640.9{\pm}48.6N$) with minimum of 6 years of experience and eight recreational players(age: $27.9{\pm}1.6yrs$, height: $177.1{\pm}6.1cm$, weight: $820.5{\pm}62.8N$) with less than one year experience were recruited in this study. For each trial being analyzed, four critical instants were identified from the video recordings: Right heel contact1 (E1), Right toe-off (E2), Right heel contact2 (E3), and Shuttlecock Impact (E4). Each hairpin net shot was broken into consecutive phases: E1~E2 (Right Landing Phase: RLP), E2~E3 (Sliding Step Phase: SSP), and E3~E4 (Impact Phase: IP). Temporal parameters, shuttlecock speed, linear and angular kinematics of body segments, and finger pressures were computed for this study. The results showed that The finger pressure of the ring finger and the middle finger for the skilled group during an impact had significantly greater than those of unskilled group. It is possible that all fingers were not used in the same manner when the racket was gripped in forehand hairpin. The result also suggested that the ring finger and the middle finger pushed the racket from top to bottom while having the mid-phalanx and proximal phalanx of index finger as an axis.

• Geomechanics and Engineering
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• 제31권6호
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• pp.573-582
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• 2022

The geometry of the gravity-type anchorage changes depends on various factors such as the installation location, ground type, and relationship with the upper structure. In particular, the anchorage geometry embedded in the ground is an important design factor because it affects the pull-out resistance of the anchorage. This study examined the effect of four parameters, related to anchorage geometry and embedded ground conditions, on the pull-out resistance in the gravity-type anchorage through two-dimensional finite element analysis, and presented a guide for major design variables. The four parameters include the 1) flight length of the stepped anchorage (m), 2) flight height of the stepped anchorage (n), 3) the anchorage heel height (b), and 4) the thickness of the soil (e). It was found that as the values of m increased and the values of n decreased, the pull-out resistance of the gravity-type anchorage increased. This trend is related to the size of the contact surface between the anchorage and the rock, and it was confirmed that the value of n, which has the largest change rate of the contact surface between the anchorage and the rock, has the greatest effect on the pull-out resistance of the anchorage. Additionally, the most effective design was achieved when the ratio of the step to the bottom of the anchorage (m) was greater than 0.7, and m was found to be an important factor in the pull-out resistance behavior of the anchorage.

• International Journal of Stem Cells
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• 제16권2호
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• pp.244-249
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• 2023

Background and Objectives: To examine whether ischemic retinal ganglion cells (RGCs) will be salvaged from cell death by human adipose-derived mesenchymal stem cells (ADSCs) in an organotypic retina model. Methods and Results: Deprived of arterial oxygen supply, whole mice retinas were cultured as an ex vivo organotypic cultures on an insert membrane in a 24-well plate. The therapeutic potential of ADSCs was examined by co-culture with organotypic retinas. ADSCs were seeded on top of the RGCs allowing direct contact, or at the bottom of the well, sharing the same culture media and allowing a paracrine activity. The number of surviving RGCs was assessed using Brn3a staining and confocal microscopy. Cytokine secretion of ADSCs to medium was analyzed by cytokine array. When co-cultured with ADSCs, the number of surviving RGCs was similarly significantly higher in both treatment groups compared to controls. Analysis of ADSCs cytokines secretion profile, showed secretion of anti-apoptotic and pro-proliferative cytokines (threshold>1.4). Transplantation of ADSCs in a co-culture system with organotypic ischemic retinas resulted in RGCs recovery. Since there was no advantage to direct contact of ADSCs with RGCs, the beneficial effect seen may be related to paracrine activity of ADSCs. Conclusions: These data correlated with secretion profile of ADSCs' anti-apoptotic and pro-proliferative cytokines.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.109-109
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• 2009

This paper represented driving characteristic of a thin-type ultrasonic motor by fabricating and utilizing two kinds of drivers which could generate sinusoidal wave, square wave, respectively. A thin brass plate was used as a cross shaped vibrator and sixteen ceramic plates were attached on upper and bottom side of the brass plate. From the thin stator, elliptical displacements of the four contact tips were obtained. Speed, torque, and current were measured by applying sinusoidal waves through driving equipment such as function generator, power amplifier: to measure characteristic of the motor. As a result, the speed and the torque changed linearly at either driving frequency of 88.6 ~ 87.6[kHz] or voltage of 24~36[V]. Two-drivers which generate sinusoidal waves and square waves were designed respectively, and then were compared through some experiments in order to be put to practical use. In conclusion, the drivers had similar characteristic of speed-torque at similar frequency and voltage. It was able to control the motor linearly by using the driver generating square wave among two-drivers. Besides, it also was possible to make the drivers smaller.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.230-230
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• 2012

Graphene have showed promising performance as electrodes of organic devices such as organic transistors, light-emitting diodes, and photovoltaic solar cells. In particular, among various organic materials of graphene-based organic devices, pentacene has been regarded as one of the promising organic material because of its high mobility, chemical stability. In the bottom-contact device configuration generally used as graphene based pentacene devices, the morphology of the organic semiconductors at the interface between a channel and electrode is crucial to efficient charge transport from the electrode to the channel. For the high quality morphology, understanding of initial stages of pentacene growth is essential. In this study, we investigate self-assembly of pentacene molecules on graphene formed on a 6H-SiC (0001) substrate by scanning tunneling microscopy. At sub-monolayer coverage, adsorption of pentacene molecules on epitaxial graphene is affected by $6{\times}6$ pattern originates from the underlying buffer layer. And the orientation of pentacene in the ordered structure is aligned with the zigzag direction of the edge structure of single layer graphene. As coverage increased, intermolecular interactions become stronger than molecule-substrate interaction. As a result, herringbone structures the consequence of higher intermolecular interaction are observed.

• 한국전기전자재료학회논문지
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• 제30권6호
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• pp.401-405
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• 2017

Because silicon thin film solar cells have a high absorption coefficient in visible light, they can absorb 90% of the solar spectrum in a $1-{\mu}m$-thick layer. Silicon thin film solar cells also have high transparency and are lightweight. Therefore, they can be used for building integrated photovoltaic (BIPV) systems. However, the contact electrode needs to be replaced for fabricating silicon thin film solar cells in BIPV systems, because most of the silicon thin film solar cells use metal electrodes that have a high reflectivity and low transmittance. In this study, we replace the conventional aluminum top electrode with a transparent aluminum-doped zinc oxide (AZO) electrode, the band level of which matches well with that of the intrinsic layer of the silicon thin film solar cell and has high transmittance. We show that the AZO effectively replaces the top metal electrode and the bottom fluorine-doped tin oxide (FTO) substrate without a noticeable degradation of the photovoltaic characteristics.