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.

포스타토의 ( A ) : 30 . 비조직에서 CD34 의 면역조직학적 규명

김영기,윤건식,김영민,( Young Ki Kim,Kyun Sik Yoon,Young Min Kim,J . A . Denburg ) 대한천식 및 알레르기학회 ( 구 대한알레르기학회 ) 1998 춘계학술대회 초록집 Vol.1998 No.-

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.

한국 문헌정보학의 현실적합성과 실천성

김영기,Kim, Young-Ki 한국문헌정보학회 2000 한국문헌정보학회지 Vol.34 No.2

지난 50년간 우리나라 문헌정보학은 외국의 이론과 기술을 별다른 여과과정 없이 도입해왔다. 연구방법론은 물론 연구주제까지도 우리 현실에 적용시키려는 경향이 우리나라 문헌정보학 연구의 주된 흐름이 되었다. 그렇지만 나라마다 발전단계나 문화적 전통이 다르기 때문에 우리나라 고유의 도서관 현장과 그 환경에 대한 이해의 부족은 실천적 연구를 수행하는데 더 큰 문제로 다가올 것이다. 따라서 연구자들은 외국 이론의 적용에 신중하여야 하며, 연구방법의 선택 역시 그 연구주제에 적합한 방법을 선택해야 할 것이다. 과거 우리나라에는 이런 식의 여과의 과정이 무시되어 왔다고 볼 수 있다. 또한 문헌정보학 연구는 도서관 현장과 밀접히 연관되어야 하며, 우리나라 문헌정보학의 이론과 실천은 우리 현실의 요구에 기초해야 한다. 우리나라에는 우리나라 도서관의 현실을 설명하고 개발할 수 있는 문헌정보학 이론이 필요한 것이다. For the past 50 years, Korean library researchers have zealously absorbed foreign thoughts and techniques without filtering them discreetly. Both research themes and methods have been freely borrowed and put into practice. This practice has been taken for granted for LIS researchers in Korea. But, lack of understanding of our own library field, has produced problems for researchers. This is because libraries of each country have its own developmental stage and cultural heritage. Therefore, I would say that researchers should be cautious in the application of foreign theories. In Korea, this kinds of filtering process has been neglected in the past. LIS research must have close relations with practical library work. LIS theories and practices in Korea should be hopefully based on the needs of the Korean society. In short, Korea should have a LIS, which serve the needs and ideals of the library and society of Korea.

제사기(第四紀) 화산암(火山岩) 분포지역(分布地域)에 빈발(頻發)하는 지질재해(地質災害)에 관(關)하여

김영기,Kim, Young Ki 대한자원환경지질학회 1980 자원환경지질 Vol.13 No.2

A geologic disasters in Ulreung-island is forming along the slope of pyroclastic, deposits and this paper discusses soil mechanics and properties and morphologies of pyroclastic soil. The typers of degradation are determined by cutting the soil and classified genetically. Finally, the range of stability is deduced from dip of slope (${\alpha}$) and lengh of slope (l) as the following;.

e-learning 컨텐츠 품질에 관한 연구

김영기,박성택,이승준,Kim, Young-Ki,Park, Seong-Taek,Lee, Seung-Jun 한국디지털정책학회 2008 디지털융복합연구 Vol.6 No.2

The remarkable growth of the Internet since mid-l990s has expanded the e-learning market and brought the transformation of educational environments and methodology. It can be said that the e-learning has changed the educational paradigm. Korean government is firmly determined to support the diffusion of e-learning because of the benefits of e-learning. People seem to accept the e-learning when its contents have high quality. A lot of research have been conducted on e-learning, however, it was mostly about user's usage intention, satisfaction and educational effect. It can't seem that sufficient research efforts have been put into figuring out the role of e-learning contents quality in the expansion of e-learning. In this paper, we present the empirical study on the influence of e-learning contents quality on user's satisfaction and educational effect. We conducted an questionnaire survey on college students to collect data and found that the quality of e-learning contents has significant influence on the users' satisfaction.

Patent Valuation for Fair Royalty Distribution in Patent Pool

김영기,박성택,이승준,Kim, Young-Ki,Park, Seong-Taek,Lee, Seung-Jun The Society of Digital Policy and Management 2010 디지털융복합연구 Vol.8 No.1

In this paper, we discuss patent pool and a patent valuation scheme for fair royalty distribution among the patents in a pool. In the knowledge-based economy, intellectual capital-the accumulation of technology and know-how-is recognized as the most important source of company's competitive advantage and economic growth. By providing exclusive rights to patent holders, the patent system aims to encourage innovation-invention & commercialization of new technologies-in order to raise the standard of living. However, drawbacks of patent system, which occur as the number of patents issued increases rapidly and patent ownership is fragmented, may slow down the innovation efforts seriously. A promising solution is the patent pool approach, which was for instance employed by the U.S. congress during World War I to free the airplane manufacturers from the patent tangle by letting them license all the patents for a fee. It is necessary to figure out relative technological contribution of patent for fair distribution of royalty revenues among patent holders. The Rating/Ranking Method seems to fit to that valuation purpose. We examined technology valuation models from various organizations and selected a set of more influential valuation factors which can be incorporated as scoring criteria in the Rating/Ranking Method.

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.

대구(大邱) 지역(地域)의 사암(砂岩) 및 규장암(珪長岩)에 대(對)한 분리면(分離面)의 활동성(活動性)

김영기,최일환,정교철,Kim, Young Ki,Choi, El Whan,Jeong, Gyo Cheol 대한자원환경지질학회 1983 자원환경지질 Vol.16 No.4

The Cretaceous sandstone and felsite distributed in north-western border part of Taegu city were studied in the viewpoint of engineering geology with an emphasis of their discontinuities. The probability of continuity of sandstone is 0.69 and that of felsite is 0.56. The correlation coefficients of sandstone are 0.52 and 0.54. Those of felsite are 0.47 and 0.48. These values reflect that the rocks have been strongly jointed. $K_0$ value of the sandstone is close to its $K_a$ value and the test suggests that the sandstone has been in active state. On the other hand, $K_0$ value of the felsite is close to its $K_p$ value, which reflects that the felsite has been in passive state, in order to maintain the stability of the sandstone. $\delta$ value should be changed to be less than 13.2.

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.