• Journal of information and communication convergence engineering
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• 제13권2호
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• pp.81-85
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• 2015

A 94-GHz phased array antenna using a log-periodic antenna has been developed on a GaAs substrate. The developed phased array antenna comprises four log-periodic antennas, a phase shifter, and a Wilkinson power divider. This antenna was fabricated using the standard microwave monolithic integrated circuit (MMIC) process including an air bridge for unipolar circuit implementations on the same GaAs substrate. The total chip size of the fabricated phased array antenna is 4.8 mm × 4.5 mm. Measurement results showed that the fabricated phased array antenna had a very wide band performance from 80 GHz to 110 GHz with return loss characteristics better than -10 dB. In the center frequency of 94 GHz, the fabricated phased array antenna showed a return loss of -16 dB and a gain of 4.43 dBi. The developed antenna is expected to be widely applied in many applications at W-band frequency.

• 한국전자통신학회논문지
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• 제14권3호
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• pp.519-528
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• 2019

현재의 브레이크 시스템은 운동에너지를 열에너지로 변경하여 거의 마찰형 브레이크로 공기 중에 발산하여 제동한다. 시스템 내에는 제동력을 발생시키는 리타더라는 장치가 있다. 전기에너지의 소모를 절약하기 위해 리타더의 제동에너지 일부를 활용하는 리타더의 고속 응답 특성에 관한 고도기술 연구는 이미 선진국에서 진행 중이다. 본 논문에서는 배터리 충전을 위해 리타더에서 발생한 3상 전압을 24V 직류 전압으로 변환하고 실험을 통해 타당성을 검증하는 DC-DC 컨버터를 제안한다.

• 한국전자통신학회논문지
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• 제18권2호
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• pp.269-276
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• 2023

본 연구에서는 1시간 이상 체공이 가능하도록 드론에 적용하기 위한 하이브리드 동력시스템을 제안한다. 이 동력시스템은 발전기에서 발생되는 교류를 다이오드 브리지 회로를 통해 직류로 변환하여 배터리를 충전시키고 동력시스템의 높은 제어성능을 얻기 위하여 분리된 셀을 갖는 배터리시스템을 사용한다. 본 논문에서는 부하별 연비와 출력을 분석하였으며, 또한 선정된 발전기의 성능을 연구하였다. 제안된 하이브리드 동력시스템을 장착한 드론은 중량 대비 출력 비율이 0.82로 계산되었으며, 비행시간은 4,179초 동안 비행하였다.

• Ocean Systems Engineering
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• 제14권1호
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• pp.53-72
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• 2024

The interaction of the blade of surface-piercing propellers (SPPs) with the water/air surface is a physical phenomenon that is difficult to model mathematically, so that such propellers are usually designed using empirical approaches. In this paper, a newly developed mechanism for measuring the torque of SPPs in an open water circuit is presented. The mechanism includes a single-component load cell and a deformable torque sensor to detect the forces exerted on the propeller. Deformations in the sensor elements lead to changes in the strain gauge resistance, which are converted into voltage using a Wheatstone bridge. The amplified signal is then recorded by a 16-channel data recording system. The mechanism is calibrated using a 6-DoF calibration system and a Box-Behnken design, achieving 99% accuracy through multivariate regression and ANOVA. Finally, the results of performance tests on a 4-blade propeller were presented in the form of changes in the torque coefficient as a function of feed rate. The results show that the new mechanism is 8% more accurate than conventional empirical methods.

• 대한기관식도과학회:학술대회논문집
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• 대한기관식도과학회 1977년도 제11차 학술대회연제 순서 및 초록
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• pp.4.4-5
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• 1977

중이의 impedance는 고막, 이소골연쇄 및 중이강.유양동.함기봉와의 공기강에 의해 결정되는 바, 저자는 우선 신선한 개의 중이를 재료로 하여 중이강의 강기체적을 변동시킴으로써 중이강의 공기체적인자가 중이의 impedance를 어떻게 변동시키는가를 조사하였고, 다음으로 과거력과 현재상태에서 외이도, 고막 및 중이에 병변이 없는 환자에서 중이의 impedance를 측정하고 아울러 측두골의 X-녹상을 언어 측두골의 함기도에 따라 중이의 static compliance의 변동을 조사하여 이과학의 임상적인 면에서의 중이의 static compliance의 또 하나의 이용가치를 구명하여 다음과 같은 결론을 얻었다. 1. 개의 중이는 control state에서 Type A의 tympanogram을 보였으며, 중이강의 공기체적의 변동에 의해 tympanogram curve의 채형은 변동하지 않았다. 2. 개의 중이에 있어서 중이의 static complance는 중이강의 공기체적의 변동에 의해 유의한 직선적인 증가를 보였으며, 중이강의 공기체적 1cc의 증가에 대해 $0.5{\pm}0.1$cc의 증가율을 보였다. 3. 측두골의 함기도가 양호해짐에 따른 중이의 static compliance의 증가경향과 개의 측두골표본에서의 실험적인 근거로부터 측두골의 함기도(x)와 중이의 static compliance (y)사이에 $y=0.19x+0.16{\pm}0.05$의 회귀방정식을 얻을 수 있었다. 따라서 중이강의 공기체적의 변동은 유의한 중이의 static compliance의 변동을 일으키며, electroacoustic impedance bridge (Madsen ZO 70, 220 Hz 의 probe tone을 사용)를 사용하였 중이의 static compliance를 측정함으로써 임상적으로 측두골의 X-선상을 촬영하지 아니하고도 간단히 측두골의 함기도를 알 수 있을 것으로 생각되어, impedance audiometry의 임상진단학적인 견지에서의 또 하나의 가치를 보고하는 바이다.

• Physical Therapy Rehabilitation Science
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• 제5권4호
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• pp.210-214
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• 2016

Objective: The aim of this study was to measure the muscle architectural parameters of abdominal muscles in healthy individuals by rehabilitative ultrasound imaging (RUSI) and to investigate their changes after bridging exercise in various environments. Design: Cross-sectional study. Methods: The study included 40 healthy participants (19 men, 21 women). Subjects were randomly allocated to a stable surface group (SG, n=20) or an unstable surface group (UG, n=20). The participants assumed three positions in rest, bridging exercise with knee flexion $60^{\circ}$, and bridging exercise with knee flexion $90^{\circ}$ for the measurement of abdominal muscle thickness by RUSI. For the resting position, the participants held the head neutral in a hook-lying position and the dominant side was measured. For contraction, the participants performed the bridging exercise with the knee joint in $60^{\circ}$ and $90^{\circ}$ of flexion for 10 seconds each. Results: For transversus abdominis, external oblique muscle thickness, within the stable surface group and the unstable surface group, no significant contraction difference was observed in both the $60^{\circ}$ and $90^{\circ}$ bridge exercise conditions. Contraction difference of internal oblique muscle was significantly larger at $90^{\circ}$ than at $60^{\circ}$ within the SG (p<0.05). But within the UG, no significant contraction difference was shown. There was no significant contraction difference between the surface group and the unstable SG at $60^{\circ}$ condition and at $90^{\circ}$ condition in all measured muscles. Conclusions: The contraction difference is different for each muscle during bridge exercise with knee flexion $60^{\circ}$ and bridging exercise with knee flexion $90^{\circ}$. Muscle contraction difference is generally large when exercised on an unstable surface than a stable surface, but these are not statistically significant when bridging exercise is performed using dynamic air cushion for unstable surface.

• 대한교통학회지
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• 제22권5호
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• pp.75-87
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• 2004

우리나라 해안지역은 강풍의 빈도가 높고 세기도 크지만 아직까지 바람을 고려한 적정속도를 안내하는 시스템은 전무한 상태이다. 강풍이 부는 곳에서의 무리한 주행은 핸들 조작의 어려움으로 인한 사고 위험과 풍속을 고려하지 않은 과속으로 인한 전복사고 등의 위험이 크다. 이러한 측면에서 바람 잦은 곳 중 주요지점에 기상정보센서(WIS:Weather Information Sensor)를 설치하고 이로부터 실시간으로 측정된 기상정보를 바탕으로 차량의 구동력과 주행저항의 크기를 극대화하는 적정속도를 VMS를 통하여 제공하는 방안이 필요하다. 목포시에 건설예정인 목포대교를 대상으로 풍속별 적정 속도를 산출한 결과, 연중 평균 풍향인 남풍일 경우 교량의 입지(정남-북)에 따라 남측으로 주행하는 차량에 대하여 풍속이 8m/h이상일 경우에는 평상시와 달리 돌풍을 대비한 여유구동력이 큰 60km/h의 속도를 안내해 주는 것이 바람직 한 것으로 나타났다. 또한 2003년도에 발생한 태풍 매미 시 목포시의 풍속인 18m/s 일 경우 시속 40km/s에서의 주행저항은 1131N으로써, 이미 변속 4단에서의 구동력(약 1054N)으로는 극복할 수 없으므로 3단 이하에서 변속을 하여야 하며, 이때의 적정속도는 주행저항과 구동력간의 차이가 가장 크게 발생하는 40km/h인 것으로 분석되었다.

• Restorative Dentistry and Endodontics
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• 제20권2호
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• pp.399-422
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• 1995

The purpose of this study was to investigate a fragment of possibility of pulpotomy with the Nd-YAG laser by the observation of pulpal healing process and the fine structural changes of the fibroblasts of the remaining pulpal tissues. Class V cavities on !55 teeth from 4 adult dogs were prepared and the pulp chambers were opened with a sterilized round bur. In the control group(19 teeth), the exposed coronal pulps were excised by a sharp excarvator. After bleeding was controlled with the sterilized cotton pellets, calcium hydroxide powder was applied on the remaining pulpal tissues and the cavities were sealed with Z.O.E. In the experimental group 1 : the pulpotomy with laser-calcium hydroxide powder application group(l9 teeth), the exposed coronal pulps were excised by Nd-YAG laser(10 watts power, 2 psi water, 20 psi air) for 2 or 3 seconds and calcium hydroxide powder was applied on the remaining pulpal tissues and the cavities were sealed with Z.O.E. In the experimental group 2 : the pulpotomy with laser-no calcium hydroxide powder application group(17 teeth), after amputating the coronal pulps with Nd-YAG laser as the experimental group 1, the remaining pulpal tissues were covered with stenilized aluminum foil and the cavities were filled with Z.O.E. The animals were sacrificed at the intervals of 1, 2, 3 and 4 weeks. All the teeth were rouutinely processed and the remaining pulpal tissues were observed by the light microscope and electron microscope. The results were as follows : 1. In light microscopic findings, there was no significant difference of the inflammatory response in the remaining pulpal tissues between the control group and the experimental groups. In both of the experimental group 1 : pulpotomy with laser-calcium hydroxide powder application group and the control group, the dentin bridges were observed after 2 weeks and the structure of the dentin bridge was almost same. In the experimental group 2 : pulpotomy with laser-no calcium hydroxide powder application group, the fibrous layers instead of dentin bridge were observed on the superficial portion of the remaining pulpal tissues after 2 weeks and they were consisted with densely crowded active fibroblasts. 2. In the electronmicroscopic findings, the active fibroblasts in the experimental groups were more frequently observed than in the control group at 1 week. But active fibroblasts were found with same frequency after 2 weeks in all of the control group and the experimental groups. 3. General distortions of the cell such as loss of the cell membrane, vaculoization of the cell etc. were observed at the suberficial layer of the remaining pulpal tissues and the carbonization was found in the dentinal wall in 1 week of the experimental groups. 4. In the experimental group 2 : pulpotomy with laser-no calcium hydroxide powder application group, the activity and the density of the fibroblasts in the fibrous layer were more than those in the deep portion of the remaining pulpal tissues after 2 weeks. 5. In the control group, bacteria such as cocci and bacilli were observed frequently, but in the experimntal groups, they could not be observed.

• 대한치과기공학회지
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• 제10권1호
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• pp.11-24
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• 1988

The purpose of this study was to determine the concentration of cadmium, nickel and chromium in the air of the work-place, blood of and urine of workers and compare the level of those heavy metals by the duration of work, work-place, process of work, smoking and other factors. In this study, 48 male dental laboratory technicans and 72 office workers as the control group were subjected. The concentration of cadmium, nickel and chromium in their blood sand urine, and that of heavy metals in the air of their work-rooms were examined and analyzed from June I 1987 to September 30, 1987. The results were as follows : 1. The concentration of cadmium in the air was the highest in the porcelain part, $0.0087{\pm}0.0016mg/m^3$, that of nickel was the highest in the crown bridge part, $0.4253{\pm}0.0052mg/m^3$, and that of chrnmium was highest in the partial denture part, $0.1063{\pm}0.0024mg/m^3$. 2. cadmium, nickel and chromium concentrations in the blood and urine of dental laboratory techincians were higher that in the office workers'. Especially the concentration of cadmium in the blood($1.92{\pm}1.23{\mu}g$/100ml) of th dental laboratory techician was about two times as high as that in the office workers'($0.90{\pm}0.73{\mu}g$/100ml), and the concentration of nickel in the urine($48.53{\pm}38.83{\mu}g$/e) of the dental laboratory thchnician was about two times as high as that in the office worker's($20.24{\pm}15.35{\mu}g$/e). 3. there was no difference in the concentration of cadmium, nickel and chromium in the blood and urine with a longer duration of work. 4. The concentration of cadmium and chromium in the blood and urine differed significantly depending upon the place of work. The concentration of cadmium was the highest in the blood of dental laboratory technicians working kin the poreclain part marking at $2.53{\pm}1.08{\mu}g$/100ml. The chromium level was the heighest in the blood of partial denture park workers with a concentration of $3.60{\pm}1.02{\mu}g$/100ml. Concerning the level of cadmium in urine, it was the highest in the porcelain part workers with a concentration of $3.41{\pm}3.15{\mu}g$/e. 5. The concentration of cadmium in the urine of metal trimming and polishing group($2.64{\pm}2.41{\mu}g$/e) was higher than that of non-metal trimming and polishing group($1.39{\pm}1.18{\mu}g$/e). 6. The concentration of chromium in the blood of smoking group($2.46{\pm}1.54{\mu}g$/100ml)was higher than that lf non-smoking group($1.54{\pm}1.25{\mu}g$/100ml). 7. The height positive correlation coefficient was shown between the concentration of nickel and chromium in the blood among the all correlations between 3metals(Cd, Ni, Cr) in the blood and those in urine. The correlation coefficient was relatively high(r=0.605,,p<0.01). In general, the higher the concentration of heavy metals in the air of work places the higher the concention lf them in the blood and urine of workers, mere attention should be paid to the working environment of dental laboratory workers, Furthermore, continuous biological monitoring and further research are required for an efficient health management for dental laboratory workers.

• 한국통신학회논문지
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• 제27권4B호
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• pp.365-371
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• 2002

본 논문에서는 전자선 묘화 장비를 이용하여 게이트 길이가 0.2 $\mu\textrm{m}$ 이하인 밀리미터파용 전력 PHEMT 소자를 제작하고 DC 특성과 주파수 특성 그리고 전력 특성을 측정하고 분석하였다. PHEMT의 제작에 사용된 단위공정은 저 저항 오믹 접촉, 에어 브릿지 및 후면 가공 공정기술 등을 이용하였다. 제작된 전력용 PHEMT는 35 GHz의 중심주파수에서 4 dB의 S21 이득과 317 mS/mm의 최대 전달컨덕턴스 그리고 62 GHz의 차단주파수와 12G GHz의 최대 공진주파수를 나타내었다. 또한 측정된 전력 특성은 35.5 %의 드레인 효율과 16 dB의 최대 출력전력 그리고 4 dB의 전력 이득을 나타내었다.