• 한국정보통신학회논문지
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• 제21권4호
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• pp.672-678
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• 2017

본 논문에서는 지상파 디지털 TV방송 수신용 광대역 준-야기 안테나(quasi-Yagi antenna; QYA)의 설계방법에 대해 연구하였다. 제안된 안테나는 FR4 기판의 한 면에 인쇄된 다이폴 투사기(driver)와 이에 근접하는 직사각형 패치모양의 도파기(director), 접지면 반사기(reflector)로 구성된다. 마이크로스트립(microstrip; MS) 선로와 코플래너스트립(coplanar strip; CPS) 선로 간의 밸런(balun)은 CPS 선로 중앙을 따라 삽입된 직사각형 MS 패치이고 종단의 한쪽은 CPS 선로에 단락 핀으로 연결되어 있다. DTV용 주파수 대역(470-806 MHz) 동작에 적합하도록 안테나를 설계하고 여러 가지 특성을 관찰하였다. 설계된 안테나는 전압정재파비가 2 이하인 주파수 대역 430-842 MHz, DTV 대역 내 배열 축 방향으로의 이득 > 3.7 dBi, 전후방비 > 7.4 dB 인 양호한 특성을 보인다.

• 한국전자파학회논문지
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• 제19권12호
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• pp.1427-1434
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• 2008

본 논문에서는 원형 편파를 가지는 GPS 수신용 소형 4중 Inverted-F 안테나(QIFA)를 제안한다. 소형화된 4-포트 안테나의 효율이 감소하는 문제를 해결하기 위하여 포트에서의 반사 계수와 포트 간의 상호 결합을 함께 고려하는 새로운 정합 방법을 이론적 해석을 통해 제안하고, 모의 실험을 통해 입증한다. 제안하는 QIFA는 $120^{\circ}$ 이상의 3-dB 빔 폭을 가지며, 15 dB 이상의 전후전계비 특성을 보인다. 또한, 제안하는 QIFA는 $10{\times}10{\times}12\;mm^3$에서 -2.5 dBic의 최대 이득과 0.5 dB 이하의 축비를 가진다.

• 한국정보통신학회논문지
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• 제21권5호
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• pp.906-912
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• 2017

본 논문에서는 실내 디지털 TV(DTV) 수신용 3소자 광대역 준-야기 안테나 (quasi-Yagi antenna; QYA) 설계 방법에 대해 연구하였다. 제안된 QYA는 마이크로스트립(microstrip; MS) 선로와 다이폴 투사기를 급전하는 코플래너스트립(coplanar strip; CPS) 선로 간 밸런을 새로운 형태로 구성하였다. 제안된 밸런은 MS 선로 종단을 CPS에 단락핀으로 연결하여 구성하였으며, CPS 선로와 반사기를 원형 링 도체로 연결하였다. 제안된 구조의 안테나를 지상파 DTV 방송 주파수 대역인 470-806 MHz 대역에서 동작하도록 설계하였다. FR4 기판 상에 $270mm{\times}150mm$ 크기로 제작된 안테나는 전압정재파비가 2 이하인 주파수 대역 470-820 MHz, DTV 대역 내 배열 축 방향으로의 이득 > 4.0 dBi, 전후방비 > 8.4 dB 인 양호한 특성을 보인다.

• 한국의류학회지
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• 제36권11호
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• pp.1197-1207
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• 2012

This study provides information for the design of pediatric inpatient uniforms with functionality and aesthetic beauty through a questionnaire-survey of the conditions of providing, wearing, preferences and improvement requirements for pediatric inpatient uniforms. As a result of the survey, intravenous injections were mostly given on the back of the hand, and the method of changing uniforms after intravenous injections was (in most cases) to pass the injection bottle through a sleeve or pant leg while the needle is inserted. The respondents answered that the sleeve length and pant length did not match. As a result of the preference of the pediatric inpatient design survey, respondents indicated they preferred pajama type, yellow color and medium size animal patterns. A similar ratio of set-in and raglan with no collar but with 3/4 length sleeve of round neck, front end, sleeve top opening, button closing and two pockets were preferred for shirts; however, a 3/4 length with rubber string on the waist, no opening and inner opening were preferred at the same ratio for pants. As for the method to adjust the length to assign functionality to pediatric inpatient uniforms, the most preferred sleeve was a roll-up sleeve with a strap and the most preferred pants were length adjusted pants that used a strap for both shirts and pants with a both sides strap. In addition, the majority of the respondents answered that a hand wrapper that protects the injection location during intravenous injections needs be developed. As for the development type, a half glove type and glove type were preferred in sequential order.

• 한국전기전자재료학회논문지
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• 제26권3호
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• pp.246-251
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• 2013

Screen printing is commonly used to form the front/back electrodes in silicon solar cell. But it has caused high resistance and low aspect ratio, resulting in decreased conversion efficiency in solar cell. Recently the plating method has been combined with screen-printed c-Si solar cell to reduce the resistance and improve the aspect ratio. In this paper, we investigated the effect of light induced silver plating with screen-printed c-Si solar cells and compared their electrical properties. All wafers were textured, doped, and coated with anti-reflection layer. The metallization process was carried out with screen-printing, followed by co-fired. Then we performed light induced Ag plating by changing the plating time in the range of 20 sec~5min with/without external light. For comparison, we measured the light I-V characteristics and electrode width by optical microscope. During plating, silver ions fill the porous structure established in rapid silver particle sintering during co-firing step, which results in resistance decrease and efficiency improvement. The plating rate was increased in presence of light lamp, resulting in widening the electrode with and reducing the short-circuit current by shadowing loss. With the optimized plating condition, the conversion efficiency of solar cells was increased by 0.4% due to decreased series resistance. Finally we obtained the short-circuit current of 8.66 A, open-circuit voltage of 0.632 V, fill factor of 78.2%, and efficiency of 17.8% on a silicon solar cell.

• 한국항행학회논문지
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• 제26권5호
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• pp.344-349
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• 2022

UWB 응용을 위해 스트립이 추가된 직각 삼각형-모양의 다이폴 소자로 구성된 소형 대수 주기 다이폴 배열 (LPDA; log periodic dipole array) 안테나를 제안하였다. 첫째, LPDA 안테나의 폭을 줄이기 위해 기존의 스트립 다이폴 소자 대신에 직각 삼각형-모양 다이폴 소자를 사용하였다. 둘째, 소자 사이의 간격을 줄여 LPDA 안테나의 길이를 줄였다. 마지막으로, 안테나의 폭을 더 줄이기 위해 직각 삼각형-모양 다이폴 소자의 양 팔의 끝에 스트립을 추가하였다. 16개의 다이폴 소자와 4 dBi 이상의 이득을 가지도록 제안된 안테나의 시제품을 FR4 기판에 44mm×30mm 크기로 제작하였다. 제작된 안테나의 전압 정재파비가 (VSWR; voltage standing wave ratio) 2 이하인 주파수 대역은 2.99-14.76 GHz로 UWB 대역을 만족하며, 측정된 이득은 4.0-5.5dBi이고 전후방비는 10 dB 이상이다. 제안된 소형 LPDA 안테나의 길이와 너비는 기존 LPDA에 비해 각각 40.9%와 20.6% 감소하였다.

• 한국지반공학회논문집
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• 제22권10호
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• pp.165-172
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• 2006

본 연구에서는 합천사에 매설되어 측방변형을 받는 무리말뚝의 거동특성을 분석하였다. 무리말뚝의 위치, 말뚝의 간격과 말뚝배열이 미치는 무리말뚝의 영향을 알고자 하였다. 실험결과는 다음과 같다. 무리말뚝에서는 모멘트 형상은 단독말뚝과 유사하나 최대 휨모멘트의 발생깊이가 깊어지고, 그 크기는 감소하였다. 말뚝의 중심간격이 증가할수록 최대휨모멘트비$(R_M)$와 수평력분담비$(R_F)$는 증가하였다. 지반변형에 따른 $R_M$은 열방향에서는 후열, 전열, 중간열의 순으로 크게 나타났고 줄방향에서는 내측보다 외측이보다 크게 나타났다.

• Geomechanics and Engineering
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• 제37권1호
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• pp.73-84
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• 2024

Owing to the high strength and abrasive characteristics of cobble-boulders, cutters are easily worn and damaged during shield tunneling, making construction inefficient. In the present work, the stress on the ripper and scraper on the cutterhead was analyzed by the PFC3D-FLAC3D coupling model of shield tunneling to get insight into the performance of the cutterhead for cutting underground cobble and boulders. The numerical calculation results revealed that the increase in trajectory radius leads to a rising stress on the cutters, and the stress on the front cutting surface is greater than that on the back of the cutters. Moreover, the correlation between cutter wear and stress is revealed based on field measurement data. The distribution of the cutter stress is consistent with the cutter wear and breakage characteristics in actual construction, in which more extensive cutter stress is exhibited, extreme cutter wear appears, and more cutter breakage occurs. Finally, the relationship between the cutterhead opening area's layout and cutter wear distribution was investigated, indicating that the cutter wear extent is the most severe in the region where the radial opening ratio dropped sharply.

• Geomechanics and Engineering
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• 제38권2호
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• pp.139-155
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• 2024

The piled raft foundations are subjected to lateral loading under the action of wind and earthquake loads. Their bearing behavior and flexural responses under these loadings are of prime concern for researchers and practitioners. The insufficient experimental studies on piled rafts subjected to lateral loading lead to a limited understanding of this foundation system. Lateral load sharing between pile and raft in a laterally loaded piled raft is scarce in literature. In the present study, lateral load-displacement, load sharing, bending moment distribution, and raft inclinations of the piled raft foundations have been discussed through an instrumented scaled down model test in 1 g condition. The contribution of raft in a laterally loaded piled raft has been evaluated from the responses of pile group and piled raft foundations attributing a variety of influential system parameters such as pile spacing, slenderness ratio, group area ratio, and raft embedment. The study shows that the raft contributes 28-49% to the overall lateral capacity of the piled raft foundation. The results show that the front pile experiences 20-66% higher bending moments in comparison to the back pile under different conditions in the pile group and piled raft. The piles in the piled raft exhibit lower bending moments in the range of 45-50% as compared to piles in the pile group. The raft inclination in the piled raft is 30-70% less as compared to the pile group foundation. The lateral load-displacement and bending moment distribution in piles of the single pile, pile group, and piled raft has been presented to compare their bearing behavior and flexural responses subjected to lateral loading conditions. This study provides substantial technical aid for the understanding of piled rafts in onshore and offshore structures to withstand lateral loadings, such as those induced by wind and earthquake loads.

• 한국운동역학회지
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• 제15권1호
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• pp.29-44
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• 2005

The purpose of this study is to reveal the effects of two different kicks, the drop kick and the punt kick, into the kicking motion, through the kinetic comparative analysis of the kicking motion, which is conducted when one kicks a soccer goal. To grasp kinetic changing factors, which is performed by individual's each body segment, I connected kicking motions, which were analyzed by a two dimension co-ordination, into the personal computer to concrete the digits of it and smoothed by 10Hz. Using the smoothed data, I found a needed kinematical data by inputting an analytical program into the computer. The result of comparative analysis of two kicking motions can be summarized as below. 1. There was not a big difference between the time of the loading phase and the time of the swing phase, which can affect the exact impact and the angle of balls aviation direction. 2. The two kicks were not affected the timing and the velocity of the kicking leg's segment. 3. In the goal kick motion, the maximum velocity timing of the kicking leg's lower segment showed the following orders: the thigh(-0.06sec), the lower leg(-0.05sec), the foot(-0.018sec) in the drop kick, and the thigh(-0.06sec), the lower leg(-0.05sec), the foot(-0.015sec) in the punt kick. It showed that whipping motion increases the velocity of the foot at the time of impact. 4. At the time of impact, there was not a significant difference in the supporting leg's knee and ankle. When one does the punt kick, the subject spreads out his hip joint more at the time of impact. 5. When the impact performed, kicking leg's every segment was similar. Because the height of the ball is higher in the punt kick than in the drop kick, the subject has to stretch the knees more when he kicks a ball, so there is a significant affect on the angle and the distance of the ball's flying. 6. When one performs the drop kick, the stride is 0.02m shorter than the punt kick, and the ratio of height of the drop kick is 0.05 smaller than the punt kick. This difference greatly affects the center of the ball, the supporting leg's location, and the location of the center of gravity with the center of the ball at the time of impact. 7. Right before the moment of the impact, the center of gravity was located from the center of the ball, the height of the drop kick was 0.67m ratio of height was 0.37, and the height of the punt kick was 0.65m ratio of height was 0.36. The drop kick was located more to the back 0.21m ratio of height was 0.12, the punt kick was located more to the back 0.28m ratio of height was 0.16. 8. There was not a significant difference in the absolute angle of incidence and the maximum distance, but the absolute velocity of incidence showed a significant difference. This difference is caused from that whether players have the time to perform of not; the drop kick is used when the players have time to perform, and punt kick is used when the players launch a shifting attack. 9. The surface reaction force of the supporting leg had some relation with the approaching angle. Vertical reaction force (Fz) showed some differences in the two movements(p<0.05). The maximum force of the right and left surface reaction force (Fx) didn't have much differences (p<0.05), but it showed the tendency that the maximum force occurs before the peak force of the front and back surface (Fy) occurs.