• Steel and Composite Structures
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• 제49권4호
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• pp.419-430
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• 2023

This paper is aimed at investigating the effect of multiple longitudinal stiffeners on the patch loading resistance of slender steel plate girders. Firstly, a numerical study is conducted through geometrically and materially nonlinear analysis with imperfections included (GMNIA), the model is validated with experimental results taken from the literature. The structural responses of girders with multiple longitudinal stiffeners are compared to the one of girders with a single longitudinal stiffener. Thereafter, a patch loading resistance model is developed through machine learning (ML) using symbolic regression (SR). An extensive numerical dataset covering a wide range of bridge girder geometries is employed to fit the resistance model using SR. Finally, the performance of the SR prediction model is evaluated by comparison of the resistances predicted using available formulae from the literature.

• Steel and Composite Structures
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• 제49권3호
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• pp.271-280
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• 2023

In this study, the three-dimensional finite element method is used to analyze the behavior of corner cracks in finite-thickness plates repaired with a composite patch. The normalized stress intensity factor at the crack front is used as fracture criterion. Comparison of stress intensity factor values at the internal and external positions of repaired quarter-elliptical corner crack was done, for three repair techniques. The influence of mechanical and geometrical properties of the adhesive layer and the composite patch on the variation of the stress intensity factor (SIF) at the crack-front was highlighted. The obtained results show that the application of double patch leads to a remarkable reduction of SIF at the crack front, compared to facial and lateral repairs.

• 한국인터넷방송통신학회논문지
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• 제21권2호
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• pp.73-78
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• 2021

본 연구에서는 기존 설계 공식을 이용하여 Inset 급전 구조를 갖는 마이크로스트립 패치 안테나를 설계하였을 때 발생하는 공진주파수의 오차를 최소화하고자 하였다. 안테나의 여러 가지 파라미터 중, 특히 패치 폭을 변화하였을 때 공진주파수의 오차가 일정한 비율로 변하는 것을 확인하였다. 이를 토대로 기존 설계 공식을 통한 공진주파수의 계산값과 안테나의 패치 폭을 변경하여 얻은 실험값을 시뮬레이션을 통하여 비교분석하였다. 결과적으로 2~10 GHz 주파수 대역에서 더 정확한 공진주파수를 얻기 위한 안테나 패치 폭의 보정 식을 도출하였으며, 도출된 식을 토대로 평균 공진주파수 오차를 2.52%만큼 감소시켰다. 또한 시뮬레이션 환경과 동일한 안테나를 제작하고 측정함으로써 그 보정 식의 효용성을 입증하였다.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2001년도 학술대회 논문집
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• pp.142-144
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• 2001

We designed superconducting four-element patch array antenna which has single-feed circularly polarization and a resonance frequency of 11.85 GHz for DBS receiving system. Antennas have been fabricated from both gold conductor and $YBa_{2}$$Cu_{3}$$O_{7-x}$(YBCO) superconductor (thin films) for comparison. Simulated and measured results, and analysis on resonant frequency(fr), return loss, and bandwidth are presented.

• 한국인터넷방송통신학회논문지
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• 제23권1호
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• pp.131-137
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• 2023

본 논문에서는 8개의 단위 안테나로 구성된 원형배열안테나(Circular Array)의 편파(Polarization) 특성을 고려한 위상 비교 방향탐지에 대해 고찰하였다. 단위 안테나는 6 ~ 12 GHz의 광대역에서 동작하는 Cavity-Backed 패치 안테나를 적용하였으며, 다양한 편파를 수신할 수 있도록 Radial 방향으로 배치하였다. 위상 비교 시 정밀한 각도를 얻기 위해 넓은 간격의 소자들을, 모호성을 해결하기 위해 좁은 간격의 소자들을 적용하였다. 방위각과 고각 모두 ±20° 영역에 대해 2차원의 방향 탐지를 수행하였으며 정면 근처에서는 0.5°, 15° 근방 영역에서는 1.6° 이하의 도래각(DOA) 오차가 있음을 확인하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 추계학술대회 논문요약집
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• pp.175-175
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• 2003

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 1999년도 춘계종합학술대회
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• pp.276-279
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• 1999

This paper proposes a design for microstrip patch antenna with dual resonance and dual polarization fed by proximity coupled quarter wavelength stub. The antenna characteristics are analyzed by the FDTD method with Mur's 2nd order ABC. From the simulation results based on the FDTD method, frequency characteristics of structure parameters such as the patch size and the offset feed are investigated. The numerical results are compared with the experimental results, and the comparison shows reasonable agreement for a design frequency.

• 대한전자공학회논문지TC
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• 제37권10호
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• pp.37-42
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• 2000

마이크로스트립 패치를 이용하여 안테나의 대역을 증가시키는 방법이 꾸준히 연구되고 있다. 본 연구에서 구형 패치를 이용하여 LMDS용 안테나를 설계하기 위하여 패치의 구조를 변형시킨 형태로 구형 패치 외부 에 밴드를 설치하여 프린징 효과에 의한 전자계의 외부 발산을 최소화하였으며, 이로 인한 안테나 효율의 증가와 원하는 대역의 안테나의 설계 파라미터 값과 실제 시뮬레이션 결과와의 차를 줄일 수 있는 장점을 갖고 있다. 또한 종래의 적층 패치 안테나구조에 비하여 본 연구에서 제시한 외부 밴드를 갖은 구조의 대역폭이 더 넓어짐을 확인 할 수 있었다.

• 한국환경보건학회지
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• 제34권6호
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• pp.403-413
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• 2008

Toxic effect of methyl tert-butyl ether (MTBE), tert-butyl alcohol (TBA) and formaldehyde (FA) on microbial activity and diversity was compared in rice field, leek patch, and tidal mud flat soil samples. MTBE, TBA and FA with different concentrations were added into microcosms containing these soil samples, and placed at room temperature for 30 days. Then the microbial activities such as dehydrogenase and viable cell numbers and microbial community using a DGGE (Denaturing gradient gel electrophoresis) fingerprinting method were measured. Among the samples, dehydrogenase activity in rice field was inhibited the most by MTBE, TBA and FA. The toxic effect was higher according to the following orders: FA > MTBE > TBA. Dominant species in the microcosms contaminated with MTBE, TBA and FA were Chloroflex, Bacilli, gamma-proteobacteria in the rice field sample, Sphingobacteria, Flavobacteria, Actinobacteria, Bacilli, gamma-proteobacteria in the leek patch sample, and Sphingobacteria, Flavobacteria, delta-proteobacteria, gamma-proteobacteria in the tidal mud flat sample.

• The Korean Journal of Pain
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• 제2권2호
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• pp.194-197
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• 1989

Epidural morphine provides excellent analgesia for the management of postoperative pain, but nausea and vomiting are a commonly reported side effect. Scopolamine, a belladona alkaloid, is an effective antiemetic when nausea is induced by morphine. Transdermal scopolamine patches have the advantage of delivering a constant low dosage of the drug over a prolonged period. To evaluate the efficacy of prophylacitic transdermal scopolamine in reducing nausea or vomiting associated with postoperative epidural morphine analgesia, I studied 60 healthy adult patients. The patients were divided into 3 groups, each group consisting of 20 patients. Group 1; no scopolamine for control Group 2; transdermal scopolamine placebo patch Group 3; transdermal scopolamine patch All patients were anesthetized by epidural injection of 2% lidocaine 15 ml and 0.5% bupivacaine 10 ml with morphine 4 mg. A Comparison with the control group, the placebo group, and Group 3, indicated, that the transdermal scopolamine reduced the incidence of nausea or vomiting associated with postoperative epidural morphine analgesia (group 1; 35%, group 2; 25%, group 3; 10%). However there were no statistically significant differences between groups at a level of p>0.05.