• Journal of the Korean Geosynthetics Society
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• v.16 no.1
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• pp.1-8
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• 2017

Displacement of dams by various instrumentations has been monitored for its safety management and analyzing the behavior after a dam collapse accident. However, unknown displacement of dam has frequently been occurred and it's difficult to analyze behavior of dams more accurately. In this study, improvement of reliabilities for displacement of dams measured by a total station was suggested by calibrating the monitoring system. The position of total station was initially measured through 2-3 given points and the coordinate of the total station was considered as an absolute value. Also, base horizontal and vertical angles had not been considered even if they are important factors when displacement was estimated. In this study, location of the total station and variations of base horizontal and vertical angles were investigated during measuring displacements of targeting points. From the results of this study, they are important factors which are affecting measurements of dam displacements. Before the calibrating, the displacement at 50 m from total station was ${\pm}20mm$. After the calibrating, the displacement was decreased by ${\pm}5mm$.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.2
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• pp.135-140
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• 2010

A new treatment is proposed to handle a deflection limit in the open-loop-onset-point (OLOP), which is commonly used in the prediction of pilot in-the-loop oscillation (PIO) due to a rate saturation. The new approach is motivated by the frequency response of a stand-alone actuator in that, unlike the suggestion by the original OLOP procedure, the rate limit onset is not delayed to a higher frequency by a deflection limit. Indeed, if a feedback control loop is closed, the rate limit onset can be shifted to a lower frequency since the controller tends to react with larger commands when deflection limited. The amplitude of the command at this onset frequency is combined with the deflection limit to estimate the associated gain reduction in the open-loop-onset-point in the final step of the OLOP process. The comparison of the new approach with the previous method reveals that an inaccurate optimism which can occur in the previous method is corrected by the proposed treatment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1201-1207
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• 2010

In this study, a fatigue testing system capable of performing load-controlled tension-tension tests for micro-specimens was developed by using an electro-magnetic actuator. Using this system, fatigue testing as well as tensile testing can be performed over a wide range of loading frequencies. Further, a new laser interferometric strain/displacement gage was used during fatigue testing to obtain high-resolution measurements of the cyclic deformation of thin films. Since the testing machine and the displacement gage are stable and show quick responses, the displacement can be measured instantaneously and continuously during fatigue testing, and high-resolution results can be obtained.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.397-401
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• 2005

In this paper, we have developed a frequency mixer which can be used as a microwave phase conjugator in the retrodirective array antenna. The retrodirective array, which can reflect the incident wave retrodirertively back to the source direction without any priori information, requires phase conjugators to achieve the phase change of 180 degrees for the incoming signal. frequency mixers can efficiently serve as phase conjugators. The circuit topology is of the 2-port structure to avoid the complexity of LO and Rf signal combination and matching circuits, using a pseudomorphic HEU device. The operating frequencies are 4.0 CHz, 2.01 CHz, and 1.99 CHz for LO, RF, and If signals, respectively. Conversion loss is measured to be -ldB and 1-dB compression point -l5 dBm at the LO power of -10 dBm.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.3
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• pp.158-164
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• 2002

2-6 GHz digital phase shifter module has been designed and fabricated. For the broadband operation and performance, MMIC phase shifter chip for phase shifter module was designed and fabricated by using the reflection-type circuits with Lange coupler. The fabricated phase shifter module shows 6.1$^{\circ}$RMS phase error, 13.5 dB maximum insertion loss, and 8 dB and 10 dB input and output return losses, respectively. Computer controlled measurement systems are realized in order to get the measured data of 32 phase states. The RMS insertion phase error and the average insertion loss deviation among 8${\times}$8 modules for the phased-array system are less than ${\pm}$0.5$^{\circ}$and ${\pm}$0.5 dB, respectively. The size of fabricated phase shifter module is 45 ${\times}$ 22.5 ${\times}$60㎣.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.10
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• pp.34-39
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• 2003

Morphing wing sections actuated by piezoceramic actuator LIPCA have been designed and their actuation displacements estimated by using the therml analogy and MSC/NASTRAN based on the linear elasticity. The wing sections are fabricated as the design and tested for evaluation. Measured actuation displacements were larger than the estimated values mainly due to the material non-linearity of the PIT wafer. The morphing wing sections can be used for control surfaces of small scale UAVs or MAVs.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.59-63
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• 2004

In this paper, we have developed a 2-port resistive frequency mixer for the retrodirective active array. The circuit topology is consisted of 2-port to avoid the complexity of LO and RF signal combination, using a pseudomorphic HEMT device. The operating frequencies are 4.0 GHz, 2.01 GHz, and 1.99 GHz for LO, RF, and IF, respectively. Conversion loss is measured to be -1㏈ and 1-㏈ compression point -15 ㏈m at the LO power of -10 ㏈m.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2554-2556
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• 2000

기존의 게임기를 포함한 여러 입력장치들의 대부분이 미세한 조작과 변위의 변화, 특히 가속도와 변위의 세분화가 어려웠다. 또한 외부의 충격에 내구성이 약한 단점들이 있었다. 본 연구에서는 최근 게임기 산업에서 3차원 입력장치를 필요로 함에 따라 기존의 2차원 변위에 더해서 3차원 입력장치의 구현을 기반으로 저가형의 소형 다축load cell 센서방식을 채택하여 부분 변위의 조작, 내구성과 기존 하드웨어의 단순화 등 여러 면에서 개선이 되었으며, 보다 정밀하고 다양한 입력에 대응하기 위하여 센싱 신호처리 회로의 개선과 디지털 통신방식을 부가하였다. 본 논문에서는 이 구현을 위한 하드웨어와 소프트웨어에 대한 연구결과를 소개하고자 한다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.91-91
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• 2011

본 개발에서는 초고속 복합 분자펌프 구동을 위한 디지털 구동장치를 설계 하였다. 초고속 모터구동을 위한 핵심제어 보드 설계 및 모듈을 설계하여 기본성능을 평가하였다. 또한 초고속 전동기 운전시 급가속 성능을 향상 하기 위해 홀센서에 의한 위치측정 오차를 최소화하는 관측기를 설계하여 모터제어기를 설계하여 고속회전 시험을 하였다. AMB 구동을 위한 전류제어기를 제작하여 성능시험을 하였다. AMB 구동을 위한 와전류식 변위센서 구동부를 설계 제작하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.140-143
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• 2011

본 연구에서는 준능동형 제진장치로 복합형 제진장치(HMD, Hybrid Mass Damper)의 운용에 요구되는 제어알고리즘 개발에 대한 연구를 진행하였다. 제어력을 산정하기 위한 알고리즘 내장화 과정에서 구조물의 상태를 피드백하기 위해서는 구조물의 가속도를 계측하고 이로부터 변위, 속도를 추정하게 되는데 여기서 발생하는 오차의 문제점을 개선하기 위하여 GPS의 실시간 변위측정기술을 활용하여 변위를 직접 입력하면서 구조물의 응답을 제어할 수 있는 알고리즘을 구성하려 한다. 이 때 측정된 데이터의 값에는 잡음이 발생하고 미분기의 동적특성을 가지고 있는 HMD에 입력신호로 사용하는 경우 상당한 오차가 생기는 변위 되먹임(Feedback)의 문제점을 확인하였다. 이러한 문제점을 개선하기 위해 제진장치 입력신호의 시간간격(Time-interval)을 조정하여 오차를 줄일 수 있는 방안을 제안하였다. 수치해석결과, 입력신호에는 최적의 시간간격(Time-Interval)이 존재하였으며 이를 적용할 경우 건물의 변위와 가속도 응답을 크게 줄일 수 있음을 확인하였다.