• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.1097-1102
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• 2001

Seismic safety of continuous span concrete bridge can be enhanced by distributing a large seismic lateral load to each supporting pier. A new viscoelastic device called Shock Transmission Unit(STU), which is a simple cylinder-piston assembly packed with a so-called silicone putty compound, enables the lateral seismic load to be transmitted to the pier by installation of the device to movable bearings of the bridge. The seismic safety of concrete bridges having the STU depends on not only safety of the bridges globally but also safety of anchor systems which anchors the STU to concrete pier. An experimental investigation is performed to study the behavior of cast-in-place anchor and post-installed anchor subjected to shear load statically and cyclically according to different edge distance, embedment length, and anchor spacing. Finally, the experimental results are compared with results by design methods of ACI and CCD, and results by FEM analysis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.281-283
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• 2006

This paper presents two new circuit topologies of DC bus lineside active edge resonant snubber assisted soft-switching PWM full-bridge DC-DC converter acceptable for either utility AC 200V-rms or AC 400V-rms input voltage source. All the active power switches in the full-bridge arms and DC busline can achieve ZCS turn-on and ZVS turn-off commutations and the total turn-off switching power losses of all active switches can be reduced for high-frequency switching action. The effectiveness of these new DC-DC converters topologies is proved for low voltage and large current high efficiency DC-DC power supplies as TIG arc welding machine from a practical point of view.

• 전력전자학회논문지
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• 제12권3호
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• pp.241-247
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• 2007

LLC 하프브리지 다중 출력용 컨버터의 보조 출력부와 같이, 펄스 전압을 입력으로 갖는 PWM 컨버터에서는 출력 정전압 제어를 위하여 스위치의 턴 온 제어 방식을 필요로 한다. 본 논문에서는 전류 불연속 모드로 동작하는 벅 컨버터의 새로운 도통시간 턴 온 제어방식에 대하여 논하였다. 제안된 LEM 제어 방식의 PWM 동작 원리를 설명하였으며, 임펄스 응답 이론을 근거로 인덕터 전류의 소신호 주파수 응답 특성을 고찰하였다. 또한 60인치 PDP 어드레스용 100W급 파워 모듈에 적용함으로서 제안된 제어 방식의 타당성을 검증하였다.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제12권12호
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• pp.357-362
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• 2023

교량은 중요한 교통 인프라지만 다양한 환경적 요인과 지속적인 교통 부하로 손상 및 균열을 겪게 되며, 이러한 요인들은 교량의 노후화를 가속화시킨다. 현재 건설한 지 오래된 교량이 많아지면서 안전성을 보장하고 노후화를 진단하기 위한 시스템의 필요성이 대두되고 있다. 이미 교량에서는 실시간 또는 주기적으로 교량의 상태를 모니터링하기 위해 구조물 건전도 모니터링(SHM) 기술이 활용되고 있다. 이 기술과 함께 인공지능과 사물인터넷 기술을 활용한 지능형 교량 모니터링 기술 개발이 진행 중이다. 본 논문에서는 노후화된 교량의 유지관리를 위해 고속 푸리에 변환과 차원 축소 알고리즘을 활용한 교량 안전성을 예측 엣지 시스템 기법을 연구한다. 특히, 기존 연구와는 다르게 실제 교량에서 수집된 센서 데이터를 이용하여 데이터셋을 형성하고 교량의 안전성을 확인할 수 있는지 알아본다.

• Steel and Composite Structures
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• 제35권6호
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• pp.799-813
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• 2020

Fatigue cracks of rib-to-deck (RD) joints have been frequently observed in the orthotropic steel decks (OSD) using conventional U-ribs (CU). Thickened edge U-rib (TEU) is proposed to enhance the fatigue strength of RD joints, and its effectiveness has been proved through fatigue tests. In-depth full-scale tests are further carried out to investigate both the fatigue strength and fractography of RD joints. Based on the test result, the mean fatigue strength of TEU specimens is 21% and 17% higher than that of CU specimens in terms of nominal and hot spot stress, respectively. Meanwhile, the development of fatigue cracks has been measured using the strain gauges installed along the welded joint. It is found that such the crack remains almost in semi-elliptical shape during the initiation and propagation. For the further application of TEUs, the design curve under the specific survival rate is required for the RD joints using TEUs. Since the fatigue strength of welded joints is highly scattered, the design curves derived by using the limited test data only are not reliable enough to be used as the reference. On this ground, an experiment-numerical hybrid approach is employed. Basing on the fatigue test, a probabilistic assessment model has been established to predict the fatigue strength of RD joints. In the model, the randomness in material properties, initial flaws and local geometries has been taken into consideration. The multiple-site initiation and coalescence of fatigue cracks are also considered to improve the accuracy. Validation of the model has been rigorously conducted using the test data. By extending the validated model, large-scale databases of fatigue life could be generated in a short period. Through the regression analysis on the generated database, design curves of the RD joint have been derived under the 95% survival rate. As the result, FAT 85 and FAT 110 curves with the power index m of 2.89 are recommended in the fatigue evaluation on the RD joint using TEUs in terms of nominal stress and hot spot stress respectively. Meanwhile, FAT 70 and FAT 90 curves with m of 2.92 are suggested in the evaluation on the RD joint using CUs in terms of nominal stress and hot spot stress, respectively.

• 한국구조물진단유지관리공학회 논문집
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• 제28권3호
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• pp.66-73
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• 2024

사장교에서 케이블 부재는 하중을 전달하는 가장 중요한 부재 중 하나이다. 따라서 사장교의 구조적 상태 및 안정성을 평가하기 위해서는 케이블의 상태를 파악하기 위해 지속적인 모니터링을 수행하는 것이 중요하다. 이러한 모니터링 시스템은 케이블에 부착된 가속도계를 통해 진동을 측정하고 이를 토대로 케이블 장력과 감쇠비를 추정하고, 이를 토대로 케이블의 상태 평가의 기초자료로 활용한다. 이러한 상시 모니터링 시스템은 지속적으로 진동 데이터를 측정하기 때문에 데이터 수집 시스템을 포함한 하드웨어가 안정적이고 전력 효율성이 높아야 한다. 또한 지속적으로 생성되는 대량의 진동 신호들을 사람의 개입을 최소화하며 안정적으로 분석할 수 있는 자율모니터링 시스템이 요구된다. 본 연구에서는 IoT를 활용한 도메인 지식 기반 자율 모니터링 시스템을 개발하였다. 케이블 자율 모니터링 시스템을 구현하기 위한 가장 중요한 요소는 케이블의 장력과 감쇠비의 추정을 위한 진동 신호의 주파수 영역 내 발생하는 첨두의 자동 추정이다. 본 연구에서는 도메인 지식 기반 첨두 자동 추정 알고리즘을 데이터 수집 및 On-Board Processing이 가능한 IoT 시스템에 내장하여 IoT 센서 단에서 Edge computing이 가능한 효율적인 IoT 자율 모니터링 시스템을 구현하였다. 개발된 자율 모니터링 시스템을 국내 사장교에 설치하여 장기간 현장 운영 성능을 평가하였으며, 그 결과 장기 데이터 수신률, 장력 추정의 정확성, 효율성 측면에서 기존 시스템과 비교하여 작동 성능을 확인하고 검증하였다.

• 대한전자공학회논문지
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• 제25권3호
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• pp.307-314
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• 1988

The thin, square-diaphragm silicon pressure sensor utilizing shear piezoresistance effect was designed and fabricated and its characteristics were examined. The sensor has only one diffused resistor, whereas conventional full-bridge sensor has four. Sensitivity is somewhat lower but temperature compensation is easier than the latter. The proposed sensor was fabricated with only one p-type diffused resistor of the dimension of 113x85\ulcorner\ulcornerlocated near the center of the edge of the diaphragm. The resistor was at 45\ulcornerwith the edge of the diaphragm. The sensitivity of the sensor was 36\ulcorner/V\ulcornermHg and was linear in the pressure range from 0 to 300 mmHg. The temperature coefficient without temperature compensation was 55 ppm/\ulcorner and it was decreased to about 0.17 mmHg/\ulcorner with compensation in the range from 10 to 60\ulcorner.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.179-185
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• 2005

This paper presents a novel circuit topology of a high efficiency single-phase power conditioner. This power conditioner is composed of time-sharing sinewave absolute pulse width modulated boost chopper with a bypass diode in the first power processing stage and time-sharing sinewave pulse width modulated full-bridge inverter in the second power processing stage operated by time-sharing dual mode pulse pattern control scheme. The unique operating principle of the two power processing stage with time-sharing dual mode sinewave modulation scheme is described with a design example. This paper proposes also a sinewave tracking voltage controlled soft switching PWM boost chopper with a passive auxiliary edge-resonant snubber. The new conceptual operating principle of this novel power conditioner related to new energy utilization system is presented and discussed through the experimental results.

• 전자공학회논문지D
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• 제35D권5호
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• pp.63-68
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• 1998

The absolute pressure sensor using SDB wafer has been fabricated. the structure of the sensor consists of two wheatstone bridges and a diaphragm. One of the two wheatstone bridges is located on the edge of diaphragm, and the other is located on the center of diaphragm. The diaphragm cavity is sealted in vacuum (~10$^{5}$ Torr) to reduce the effect of temperature due to the vapor in the cavity on the sensitivity of pressure sensor. This is the minor method of temperature compensation method. In this experiment the main compensation method is to use the difference of the two bridge offset voltages. The drift of offset voltage with temperature is reduced by using this method so that temperature charcteristics is improved. In this method the temperature effect in the range of 22~100.deg. C was compensated over 80%.

• 천문학회보
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• 제42권2호
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• pp.83.2-83.2
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• 2017

We report observations of light bridge (LB) jets taken with the New Solar Telescope. Jets as dark, fine threads occurred lined along both edges of a LB of a sunspot, which is a bright and elongated structure that divides a sunspot's umbra into two or more parts. This LB jets are observed for about three hours with $H{\alpha}$ filtergraph at ${\pm}0.4{\AA}$, ${\pm}0.8{\AA}$ from the line center, TiO filtergraph, and near infra-red imaging spectropolarimeter (NIRIS). High resolution $H{\alpha}$ data revealed that subsequent ejection of LB jets were associated with subsequent brightening along the edge of the LB. Also, this subsequent brightening was spatially correlated with both photospheric flow and magnetic field change detected from the TiO and NIRIS data, respectively. Preliminary results of LB jet observation and discussions on its formation mechanism will be presented.