초음파 tomography를 응용한 콘크리트 구조물의 비파괴 시험에 관한 연구

김영기,윤영득,윤종열,김정수,김운경,송문호,Kim, Young-Ki,Yoon, Young-Deuk,Yoon, Chong-Yul,Kim, Jung-Soo,Kim, Woon-Kyung,Song, Moon-Ho 대한전자공학회 2000 電子工學會論文誌-SP (Signal processing) Vol.37 No.1

As a potential approach for non-destructive testing of concrete structures, we evaluate the time-of-flight (TOF) ultrasound tomography technique In conventional X ray tomography, the reconstructed Image corresponds to the internal attenuation coefficient However, in TOF ultrasound tomography, the reconstructed Image is proportional to the retractive index of the medium Because refractive effects are minimal for X-rays, conventional reconstruction techniques are applied to reconstruct the Image in X-ray tomography However, since ultrasound travels in curved path, due to the spatial variations in the refractive index of the medium, the path must be known to correctly reconstruct the Image. Algorithm for determining the ultrasound path is developed from a Geometrical Optics point view and the image reconstruction algorithm, since the paths are curved It requires the algebraic approach, namely the ART or the SIRT Here, the difference between the computed and the measured TOP data is used as a basis, for the iteration process First the initial image is reconstructed assuming straight paths. It then updates the path based on the recently reconstructed image This process of reconstruction and path determination repeats until convergence The proposed algorithm is evaluated by computer simulations, and in addition is applied to a real concrete structure. 본 연구에서는 초음파와 tomography 기법을 기반으로 콘크리트 구조물의 비파괴 시험에 대한 방법론을 정립하고 검증하였다 일반적인 X-ray tomography에서는 물체를 통과하는 파동의 감쇠(attenuation) 데이터에 기초를 두고있는 반면에, 본 연구에서는 time-of-flight(TOF) 데이터를 사용하여 매질의 굴절률(refractive index)을 포괄적으로 표현하는 단층영상을 복원한다 X-ray tomography에서는 측정된 감쇠 데이터를 영상복원(Image reconstruction) 알고리즘에 의해서 처리하며, 파동의 굴절은 고려할 필요가 없다 그러나 초음파는 매질(medium)의 굴절률(refractive index)에 따라 초음파의 경보가 변경되므로 초음파 tomography에서는 초음파 경로의 연산이 선행되어야만 단층영상을 복원할 수 있게 된다 초음파 정보의 연산은 가하광학(Geometrical Optic)에서 사용되는 굴절률과 경로의 관계에 기초를 둔다 영상 복원은 대수학적 접근 방법인 ART (algebraic reconstruction technique) 또는 SIRT(simultaneous iterative reconstruction technique)를 기초로 연산된 초음파의 경로를 따라 선적분한 TOF 값과 측정된 TOF 값의 차이를 기반으로 수행된다 실제 구현에서는 초음파가 직진한다는 가정하에 영상을 복원하고, 이를 기반으로 초음파의 경로를 연산하였다 본 논문에서는 이들 두 과정(경로연산 및 영상복원)의 반복연산을 통하여 영상을 복원하였다. 세안하는 알고리즘을 모의실험으로 평가하였고, 실제 콘크리트 구조물에 적용하여 본 방법론의 무한한 가능성을 입증하였다.

'95 통신산업 전망

김영기,Kim, Yeong-Gi 한국전자정보통신산업진흥회 1995 電子振興 Vol.15 No.1

새로운 금송 국내재배 성공 -살아있는 신생대 신비의 조경수

김영기,Kim, Yeong-Gi 한국조경수협회 2001 造景樹 Vol.65 No.11

친환경농업육성법 개정에 부쳐

김영기,Kim, Yeong-Gi 전국농업기술자협회 2006 농업기술회보 Vol.43 No.3

현상학적으로 본 부산지역 공공도서관 장서형성 요인 - 한국사회 지식흐름의 문제와 관련하여

김영기,Kim Young-Ki 한국문헌정보학회 1998 한국문헌정보학회지 Vol.32 No.3

이 연구는 부산지역 공공도서관의 사회사를 추적하는 과정에 나타난 <도서변상사건>과 <금서사건>이 장서의 축적 과정에 미친 영향을 현상학적으로 분석한 것이다. 도서관의 장서는 그 도서관이 추구하는 목적과 이용자의 요구를 두 축으로 하여 축적되는 것이 원칙이지만, 우리 나라 공공도서관의 경우 사회${\cdot}$정치적인 상황이 오히려 더 큰 영향을 미쳐왔다고 볼 수 있다. <도서변상사건>과 <금서사건>은 이런 사회 정치적인 상황이 도서관에 발현된 대표적인 사례라 할만하다. 이들 사건은 공공도서관 직원들의 창의성을 말살시키면서 수동적이고 순응적인 성향으로 변질시켜 버리는 결과를 낳았을 뿐만 아니라, 공공도서관의 장서가 편향성을 띤 채 축적될 수밖에 없는 중요한 요인이 되었다고 볼 수 있다. This paper examines the influence of <Book-compensation Event> and <Banned Books Event> in the process of collection building in public libraries. These events resulted in depriving library workers of their voluntary spirit. And these events have also become a main cause of ideological prejudices as reflected in collection building.

고유동 일반강도 콘크리트의 요변성 부여에 따른 거푸집 누출 저감 성능 분석

김영기,이유정,김인태,한동엽,Kim, Young-Ki,Lee, Yu-Jeong,Kim, In-Tae,Han, Dong-Yeop 한국건축시공학회 2023 한국건축시공학회지 Vol.23 No.4

The central objective of this study is to curtail the leakage of mortar or cement paste, often resultant of ill-constructed formwork, by implementing thixotropy in the formulation of high-fluidity, standard-strength concrete. When such concrete is utilized in smaller scale construction projects, instances of formwork gaps due to suboptimal construction precision may lead to significant leakage of mortar and paste, a problem not typically encountered with traditional slump-flow concrete. In this investigation, Polyvinyl Alcohol(PVA) and borax are incorporated into the concrete mixture to induce thixotropy. The experimental design includes varying methodologies for integrating PVA and borax, while assessing alterations in diverse concrete performances, including thixotropy and leakage reduction potential that simulates formwork gap conditions. Under the experimental conditions defined within this study, it was found that replacing, rather than merely adding PVA and borax, aids in averting water addition via suspensions. This approach yielded promising results in terms of concrete properties and proved efficacious in stemming leakage in concrete possessing sufficient thixotropy. Notably, when a 6% PVA suspension was substituted, a significant reduction in leakage was observed. Consequently, it is projected that construction quality can be ensured, even with lower precision formwork, by applying thixotropy to concrete through the use of PVA and borax.

'93 통신산업 전망

김영기,Kim, Yeong-Gi 한국전자정보통신산업진흥회 1992 電子振興 Vol.12 No.12

대구지방(大邱地方)의 확률일우량(確率日雨量)에 관(關)한 연구(硏究)

김영기,나인엽,Kim, Young Ki,Na, In Yup 대한자원환경지질학회 1971 자원환경지질 Vol.4 No.4

With the advance of civilization and steadily increasing population rivalry and competition for the use of the sewage, culverts, farm irrigation and control of various types of flood discharge have developed and will be come more and more keen in the future. The author has tried to calculated a formula that could adjust these conflicts and bring about proper solutions for many problems arising in connection with these conditions. The purpose of this study is to find out effective sewage, culvert, drainage, farm irrigation, flood discharge and other engineering needs in the Taegu area. If demands expand further a new formula will have to be calculated. For the above the author estimated methods of control for the probable expected rainfall using a formula based on data collected over a long period of time. The formula is determined on the basis of the maximum daily rainfall data from 1921 to 1971 in the Taegu area. 1. Iwai methods shows a highly significant correlation among the variations of Hazen, Thomas, Gumbel methods and logarithmic normal distribution. 2. This study obtained the following major formula: ${\log}(x-2.6)=0.241{\xi}+1.92049{\cdots}{\cdots}$(I.M) by using the relation $F(x)=\frac{1}{\sqrt{\pi}}{\int}_{-{\infty}}^{\xi}e^{-{\xi}^2}d{\xi}$. ${\xi}=a{\log}_{10}\(\frac{x+b}{x_0+b}\)$ ($-b<x<{\infty}$) ${\log}(x_0+b)=2.0448$ $\frac{1}{a}=\sqrt{\frac{2N}{N-1}}S_x=0.1954$. $b=\frac{1}{m}\sum\limits_{i=1}^{m}b_s=-2.6$ $S_x=\sqrt{\frac{1}{N}\sum\limits^N_{i=1}\{{\log}(x_i+b)\}^2-\{{\log}(x_0+b)\}^2}=0.169$ This formule may be advantageously applicable to the estimation of flood discharge, sewage, culverts and drainage in the Taegu area. Notation for general terms has been denoted by the following. Other notations for general terms was used as needed. $W_{(x)}$ : probability of occurranec, $W_{(x)}=\int_{x}^{\infty}f_{(n)}dx$ $S_{(x)}$ : probability of noneoccurrance. $S_{(x)}=\int_{-\infty}^{x}f_(x)dx=1-W_{(x)}$ T : Return period $T=\frac{1}{nW_{(x)}}$ or $T=\frac{1}{nS_{(x)}}$ $W_n$ : Hazen plot $W_n=\frac{2n-1}{2N}$ $F_n=1-W_x=1-\(\frac{2n-1}{2N}\)$ n : Number of observation (annual maximum series) P : Probability $P=\frac{N!}{{t!}(N-t)}F{_i}^{N-t}(1-F_i)^t$ $F_n$ : Thomas plot $F_n=\(1-\frac{n}{N+1}\)$ N : Total number of sample size $X_l$ : $X_s$ : maximum, minumum value of total number of sample size.

Clean Room 위험과 대책 - 화재.폭발.산재 재해를 중심으로

김영기,Kim, Yeong-Gi 한국화재보험협회 1994 防災와 保險 Vol.63 No.-

전자공업에서의 도장 작업

김영기,Kim, Yeong-Gi 한국화재보험협회 1993 防災와 保險 Vol.58 No.-