• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.694-695
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• 2013

An experimental study has been made with the use of time reversal concepts to recover the input waveform in a long range propagation of dispersive Lamb waves. Three techniques have been tested: Regular TR, 1 bit TR and Inverse filter (IF). The IF approach was found to completely recover the original input signal. Moreover, the IF technique significantly increases the contrast, i.e., the ratio of the recovered signal and the sideband signal.

• 과학교육연구지
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• 제34권2호
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• pp.203-210
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• 2010

본 연구에서는 은염 물질인 Slavich PFG-01을 사용하여 투과형 홀로그래피 회절격자를 제작하고, 고효율의 회절격자 제작을 위한 현상액의 조성 등과 같은 화학적 처리 과정의 조건들을 파악하고, 반전표백과 무정착 은염 재생성 표백에 의한 회절격자의 회절 효율 특성에 대해 알아보았다. 현상액 AAC를 사용하여 반전표백에서 89.0%과 무정착 은염 재생성 표백에서 82.1%의 최대회절효율을 얻었으며, 무정착 은염 재생성 표백의 경우는 반전표백에 비해 높은 노출에너지가 필요함을 알 수 있었다. 기존의 홀로그래피 기록물질인 Agfa 8E75HD나 BB-640로 보고된 회절효율에 비해 더 높은 회절효율 얻을 수 있었으며, 기록물질 특성 차이로 인해 더 높은 노출에너지가 필요함을 알 수 있었다. 한 가지 현상 주약으로 이루어진 현상액에 비해 두가지 현상 주약을 혼합한 경우 더 높은 회절효율을 얻을 수 있었으며, 대체로 반전표백에 비해 무정착 은염 재생성 표백에서 높은 회절효율을 나타내었다.

• 한국정밀공학회지
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• 제24권3호
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• pp.117-123
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• 2007

This paper describes a three-probe system that can be used to measure the parallelism and straightness of a pair of rails simultaneously. The parallelism is measured using a modified reversal method, while the straightness is measured using a sequential two-point method. The measurement algorithms were analyzed numerically using a pair of functionally defined rails to validate the three-probe system. Tests were also performed on a pair of straightedge rails with a length of 250 mm and a maximum straightness deviation of $0.05{\mu}m$, as certified by the supplier. The experimental results demonstrated that the parallelism-measurement algorithm had a cancellation effect on the probe stage motion error. They also confirmed that the proposed system could measure the slope of a pair of rails about $0.06{\mu}rad$. Therefore, by combining this technique with a sequential differential method to measure the straightness of the rails simultaneously, the surface profiles could be determined accurately and eliminate the stage error. The measured straightness deviation of each straight edge was less than $0.05{\mu}m$, consistent with the certified value.

• 한국전문물리치료학회지
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• 제4권2호
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• pp.66-76
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• 1997

The purpose of this study was to compare the integrated electromyographic activity ratios of vastus lateralis(VL); rectus femoris lateral portion (RFL); rectus femoris medial portion(RFM); and vastus medialis(VM) muscles of 30 healthy subjects under three proprioceptive neuromuscular facilitation(PNF) techniques. Each subject was randomly assigned to one of 3 PNF techniques groups : slow reversal(SR), slow reversal hold(SRH) and rhythmic stabilization (RS). Each person was positioned in supine with the right hip flexed to $45^{\circ}$ and the knee fully extended and received a total of 6 sessions. Each technique was applied to the right lower extremity in two diagonal patterns while electrical activity was monitored from the ipsilateral muscles VL, RFL, RFM, and VM, respectively. Comparison of normalized mean EMG magnitudes from VL, VM showed that RS demonstrated significantly greater activity than that of SR or SRH and that RFL and RFM did not demonstrate any greater relative EMG activity with the three PNF techniques than did VL or VM.

• 한국항공우주학회지
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• 제34권5호
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• pp.101-106
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• 2006

본 논문은 TCO(thrust cut-off) 시스템을 장착한 로켓 모터의 성능설계에 관한 연구로서, TCO 포트 크기에 따라 변화하는 로켓의 성능을 평가하였다. 시험용 로켓 모터를 제작하여 연소시험을 행하였고, TCO 포트 크기에 따른 추력변화의 경향을 분석하여 최대 역방향 추력점이 존재함을 밝혀내었으며 보존방정식을 이용하여 TCO 성능설계 및 시험분석을 행하였다. 이와 같은 성능설계 기법은 향후 유사한 TCO 시스템의 설계에 유용하게 적용될 수 있다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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• pp.53-56
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• 2006

본 논문은 TCO(thrust cut-off) 시스템을 장착한 로켓 모터의 성능설계에 관한 연구로서, TCO 포트 크기에 따라 변화하는 로켓의 성능을 평가하였다. 시험용 로켓 모터를 제작하여 연소시험을 행하였고, TCO 포트 크기에 따른 추력변화의 경향을 분석하여 최대 역방향 추력점이 존재함을 밝혀내었으며 보존방정식을 이용하여 TCO 성능설계 및 시험분석을 행하였다. 이와 같은 성능설계 기법은 향후 유사한 TCO 시스템의 설계에 유용하게 적용될 수 있다.

• 한국전자파학회지:전자파기술
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• 제6권2호
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• pp.45-53
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• 1995

이동통신에서 QAM변조방식은 레일리 페이딩채널의 특성으로 인해 채널의 추정 및 보상의 방법을 사용하여 페이딩에 대한 왜곡을 보정하더라도 페이덩이 심하게 타는 부분에 대해서는 연집에러가 생기게 되어 그 성능은 열악하다. 본 논문에서는 이 연집에리를 bit reversal 블럭 인터리버플 이용하여 분산시키고 컴퓨터 탐색의 방법으로 찾아낸 레일리 채널에 적합한 TCM을 이용하여 레일리 페이딩 채널에서의 3/4 16QAM TCM의 성능 을 분석하였다. 분석결과 인터리버의 효과는 $10^{-3}$의 오율에서 약 2dB, 변형된 비터비 복호기의 사용으로는 2 5 5dB 그리고 다이버시티의 사용으로는 약9dB의 이득이 있음을 얄 수 있었다. 이는 16QAM TCM이 디지틀 이 동통신에서 사용될 수 있음을 보인다.

• Smart Structures and Systems
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• 제4권4호
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• pp.391-406
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• 2008

This study attempts to develop a real-time debonding monitoring system for carbon fiber-reinforced polymer (CFRP) strengthened structures by continuously inspecting the bonding condition between the CFRP layer and the host structure. The uniqueness of this study is in developing a new concept and theoretical framework of nondestructive testing (NDT), in which debonding is detected without relying on previously-obtained baseline data. The proposed reference-free damage diagnosis is achieved based on the concept of time reversal acoustics (TRA). In TRA, an input signal at an excitation point can be reconstructed if the response signal measured at another point is reemitted to the original excitation point after being reversed in the time domain. Examining the deviation of the reconstructed signal from the known initial input signal allows instantaneous identification of damage without requiring a baseline signal representing the undamaged state for comparison. The concept of TRA has been extended to guided wave propagations within the CFRP-strengthened reinforced concrete (RC) beams to improve the detectibility of local debonding. Monotonic and fatigue load tests of large-scale CFRP-strengthened RC beams are conducted to demonstrate the potential of the proposed reference-free debonding monitoring system. Comparisons with an electro-mechanical impedance method and an inferred imaging technique are provided as well.

• PNF and Movement
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• 제4권1호
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• pp.1-7
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• 2006

Objective : The purpose of this study was conducted to find scapular movement instability related with shoulder complex and provide strengthening the scapular muscles with proprioceptive neuromuscular facilitation(PNF). Methods : This is a literature study with books and articles, seminar note and book for PNF international course. Results : The scapular serve as the platform for humeral motions. The scapulothoracic articulation is stabilized and controlled, in part, by the scapular muscles. Therefore, if scapular muscle function is altered, then dysfunctional scapulothoracic kinematics may result. Strengthening exercise for scapular muscles are a common part of rehabilitation programs designed for patients with scapular instability. Conclusion : Treatment of the scapular instability is provided. It is that treatment with combination of isotonic, stabilize reversal on different patient's positions.

• PNF and Movement
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• 제14권2호
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• pp.149-155
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• 2016

Purpose: The purpose of this study was to investigate the effects of using proprioceptive neuromuscular facilitation (PNF) exercise in the progressive sitting position on the dynamic balance ability of a patient with a cerebellar injury. Methods: The subject had ataxia due to cerebellar injury. The subject participated in a PNF bilateral scapular pattern exercise with stabilizing reversal technique during a progressive sitting position session as well as baseline for 20 minutes a day for 4 weeks. In the first session, PNF exercises were performed at a height of 40 cm for 10 minutes, and in the second session they were performed at 50 cm for 10 minutes from a lower center of gravity (COG) to a higher COG sitting position. We used the Berg Balance Scale (BBS), Five-Times-Sit-to-Stand Test (FTSST), and the Timed Up and Go Test (TUGT) to measure the subject's dynamic balance ability every two days through the entire session. Results: After participating in the program, the subject's dynamic balance ability improved compared to the first baseline, as measured by BBS (2 points increased), FTSST (5.3 sec decreased), and TUGT (2 sec decreased). The increase was also maintained in the second baseline session. Conclusion: PNF exercise using bilateral scapula patterns with a stabilizing reversal technique helps to enhance the dynamic balance ability of a cerebellar injury patient.