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어드미턴스 기반 콘크리트 경화 모니터링의 실험 및 수치적 검증
김완철(Wan Cheol Kim),박규해(Gyuhae Park) 한국비파괴검사학회 2016 한국비파괴검사학회지 Vol.36 No.3
콘크리트는 건축물에 가장 많이 사용되는 재료 중 하나이다. 건축물 시공 시 적절한 하중 재하시점을 결정하기 위해 콘크리트의 경화 상태의 점검은 매우 중요한 사항이다. 또한 부정확한 경화 모니터링은 건축물의 부실공사 혹은 붕괴로 이어질 수 있다. 본 연구에서는 어드미턴스를 기반으로 한 압전체 센서 자가진단기법을 확장 적용한 콘크리트 경화 모니터링 기법을 개발하였다. 이 기법을 통해 콘크리트의 경화를 모니터링 하였으며 실험 결과 분석을 통해 본 기법의 상대강도 추정 가능성을 확인하였다. 또한 경화 시 발현강도에 따른 어드미턴스 신호 예측을 위해 수치적 모델링을 하였으며 실험 결과와 경화 진행 경향성을 비교하였다. 이를 통해 본 연구에서 개발한 기법의 효용성을 실험 및 수치적으로 확인하였다. This paper presents a new technique for monitoring the concrete curing process using embedded piezoelectric transducers via admittance measurements. When a piezoelectric transducer is embedded in a structure, the electrical impedance (admittance) of the transducer is coupled with the mechanical impedance of the host structure, which allows monitoring of the structural condition. In this study, the admittance signatures are used for monitoring the concrete curing process. This new method is based on an admittance-based sensor diagnostic process, in which the capacitance values of the piezoelectric transducers are dependent on the strength of the host structure. We numerically and experimentally investigated the variations in capacitive value during the curing process. The results demonstrate that there is a clear relationship between the concrete curing status and the slope, this indicates that the proposed method could be efficiently used for monitoring the curing status of a concrete structure.
김완철(Wan-Cheol Kim),이호준(Ho-Jun Lee),윤경식(Kyoung-Sik Yun),최승욱(Sung-Yug Choi),이장명(Jang Myung Lee) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.4
This paper proposes a modified and efficient method for tracking trajectory of moving objects in the dynamics image. This method could apply on the unmanned security system, the checker defected goods on Factory Automation and the unmanned automatic traffic control. Instead of using the expensive image processing board, an image grabber is used to transform the analog image to digital image. The low cost implementation expands the range of applications. To achieve the image processing in real time, a matrix method for detecting objects in this paper. After the segmentation process and finding a matrix coefficient, the matrix is multiplied by a coefficient - this is a convolution operation - and then the result is subtracted by the original background image. This subtracted value is used to determine the existence of objects.
Facing targets sputtering system으로 제조된 TbFeCo 박막의 광자기 특성 및 시효 영향
문정탁,김명한,김완철,Mun, Jeong-Tak,Kim, Myeong-Han,Kim, Wan-Cheol 한국재료학회 1995 한국재료학회지 Vol.5 No.4
TbFeCo 박막의 Facing Targets Sputtering System 조건, 조성 및 시효 처리에 따른 광자기적 특성과 산화 특성을 조사하였다. XPS와 AES를 통하여 보호막 없이 제조된 TbFeCo 박막의 표면에는 Co에 우선하여 Tb과 Fe가 안정한 산화물의 형태로 존재하며, 표면에서 3.2nm 깊이부터는 산화되지 않은 TbFeCo 박막이 존재함을 확인하였다. TbFeCo 박막을 시효 시킴에 따라 Fe 산화층의 두께는 거의 변화가 없었으며, Tb Oxide 층만이 증가하였다. TbFeCo 박막은 사용된 기판의 종류나 제조조건에 따라 열적 안정성에 큰 차이를 보였다.
투과전자현미경을 이용한 $SmZn_{0.67}Sb_2$의 3차원적 구조 분석
김진규,강성권,김완철,김윤중,Kim, Jin-Gyu,Kang, Sung-Kwon,Kim, Wan-Cheol,Kim, Youn-Joong 한국현미경학회 2004 Applied microscopy Vol.34 No.4
무기결정질인 $SmZn_{0.67}Sb_2$의 3차원적 구조 (공간군 P4/nmm, $a=4.26{\AA},\;c=10.37{\AA}$)를 전자결정학을 이용하여 분석하였다. 3차원적 정보를 얻기 위해서 주요 정대축인 세 방향의 고분해능 이미지의 정보와 16개의 정대축 방향의 회절도형을 조합하였다. 고분해능 이미지의 결정학적 화상처리(CIP)를 결정구조의 보다 정확한 분석을 위하여 사용하였다. 전자결정학을 이용한 분석 결과, [001], [100], [110] 방향에 대한 고분해능 이미지의 ${\Phi}_{res}$는 각각 $17.0^{\circ},\;8.3^{\circ},\;21.9^{\circ}$를 나타내었다. 전자결정학을 이용한 구조 분석 결과에 대한 정확도를 비교하기 위하여 X-ray 회절 분석을 시도하였다. $SmZn_{0.67}Sb_2$의 X-ray 구조 분석 결과, $a=4.276{\AA},\;c=10.287{\AA}$이고 신뢰도($R_{sym}$)는 4.16% 이었다. The three-dimensional (3D) structure of an inorganic crystal, $SmZn_{0.67}Sb_2$ (space group P4/nmm, $a=4.26{\AA}\;and\;c=10.37{\AA}$) was solved by electron crystallography. High resolution electron microscopy (HREM) images from 3 different major zone axes and selected-area electron diffraction patterns from 16 different zone axes were combined to obtain a 3D information. A crystallographic image processing (CIP) of HREM images was used for more accurate determination of the crystal structure. As a result of this electron crystallography, average phase errors (${\Phi}_{res}$) of [001], [100] and [110] HREM images are $17.0^{\circ},\;8.3^{\circ}\;and\;21.9^{\circ}$, respectively. Xray crystallography of $SmZn_{0.67}Sb_2$ has attempted to compare accuracy of the structure determination by electron crystallography, which resulted in the cell parameters of $a=4.2976(6){\AA}\;and\;c=10.287(2){\AA}$, and the R-factor ($R_{sym}$) of 4.16%.
박제민(Je-Min Park),김완철(Wan-Cheol Kim) 한국표면공학회 2010 한국표면공학회지 Vol.43 No.4
The Co-Cr alloys have clinical histories as dental and orthopaedic implants, and recently as cardiovascular stent applications because they exhibit a high elastic modulus and radiopacity. In order to improve their mechanical and corrosion resistance, electropolishing is employed as the final process. Electropolishing, an anodic dissolution process in the transpassive state, is sensitively affected by process conditions such as current density, machining time, and electrode gap. In this study, the effect of the electropolishing conditions on surface roughness and corrosion resistance is investigated for Co-Cr alloys (L605). The most smooth surface is obtained when electropolishing is performed at 15-20 V for 15-30 sec with a electrode gap of 3.5 ㎜. It is found out that electropolishing reduces corrosion rate about one-tenth as much.
갑상선 선종을 동반한 원발성 부갑상선 기능 항진증 1예
정성후(Sung Hoo Jung),김완철(Wan Cheol Kim),강남부(Nam Poo Kang) 대한두경부종양학회 1999 대한두경부 종양학회지 Vol.15 No.1
Primary hryperparathyroidism is a relatively rare disease entity in Korea. It's characterized by severe skeletal and renal changes due to hypersecretion of parathyroid hormone, and rarely shows peptic ulceration, hypertension, pancreatitis and impaired mentality. Recently the determination of the serum calcium level has become a routine laboratory test and the awareness of primary hyperparathyroidism has been incerased, the disease is being diagnosed with increasing frequency. Primary hyperparathyroidism is most commonly caused by parathyroid adenoma and rarely hyperplasia, cancer of parathyroid glands. The authors operated sucessfully a case of primary parathyroid adenoma by diagnosed by nuclear medical diagnostic work-up. The patient had anterior neck mass(soft, non tender nodule) on physical examination, multiple goiter on thyroid ultrasonogram and scan. The parathyroid lesion was difficult to find preoperatively.
급성 관상 동맥 증후군으로 오인된 식도 벽내 혈종 1예
유대곤 ( Dae Gon Ryu ),최철웅 ( Cheol Woong Choi ),강대환 ( Dae Hwan Kang ),김형욱 ( Hyung Wook Kim ),정동일 ( Dong Il Jeong ),김완철 ( Wan Chul Kim ),신재규 ( Jae Gyu Shin ),임태원 ( Tae Won Lim ) 대한소화기학회 2017 대한소화기학회지 Vol.69 No.4
Intramural hematoma of the esophagus is a rare condition that can be spontaneous or secondary to trauma, toxic ingestion, or intervention. If it is the spontaneous type, it usually presents initially with epigastric pain, hematemesis or dysphagia. We present a case of intramural hematoma of the esophagus mimicking acute coronary syndrome. A 63-year-old man presented with severe acute chest pain. He has four coronary stents that were inserted five years ago, from a different hospital, and is on dual antiplatelet agents. Coronary angiography was performed immediately under the suspicion of acute coronary syndrome, and we found that there was no obvious clogging of the coronary arteries. Next, chest computed tomography was performed due to suspected aortic dissection, and the result was also negative. Four days later, endoscopy was performed and intramural hematoma covered with large ulcers was diagnosed. (Korean J Gastroenterol 2017;69:239-242)