• Earthquakes and Structures
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• 제12권6호
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• pp.673-687
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• 2017

A three-dimensional; structural health monitoring; vertical; planar; cross-sample entropy; multiscaleA three-dimensional structural health monitoring (SHM) system based on multiscale entropy (MSE) and multiscale cross-sample entropy (MSCE) is proposed in this paper. The damage condition of a structure is rapidly screened through MSE analysis by measuring the ambient vibration signal on the roof of the structure. Subsequently, the vertical damage location is evaluated by analyzing individual signals on different floors through vertical MSCE analysis. The results are quantified using the vertical damage index (DI). Planar MSCE analysis is applied to detect the damage orientation of damaged floors by analyzing the biaxial signals in four directions on each damaged floor. The results are physically quantified using the planar DI. With progressive vertical and planar analysis methods, the damaged floors and damage locations can be accurately and efficiently diagnosed. To demonstrate the performance of the proposed system, performance evaluation was conducted on a three-dimensional seven-story steel structure. According to the results, the damage condition and elevation were reliably detected. Moreover, the damage location was efficiently quantified by the DI. Average accuracy rates of 93% (vertical) and 91% (planar) were achieved through the proposed DI method. A reference measurement of the current stage can initially launch the SHM system; therefore, structural damage can be reliably detected after major earthquakes.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.2160-2163
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• 2005

Solid freeform fabrication (SFF) technology plays a major role in industry and represents a reasonable percentage of industrial rapid prototyping/tooling/manufacturing (RP/RT/RM) development applications. However, SFF technology still has long way to progress to achieve satisfactory process speed, surface finish and overall quality improvement of its application. Today, three dimensional printing (3DP) technique that is one of SFF technology is receiving many interests, and is applied by various fields. It can fabricate three dimensional objects of solid freeform with high speed and low cost using ink jet printing technology. However, need long curing time after manufacture completion. And it must do post-processing process necessarily to heighten strength of objects because strength of fabricated objects is very weak. Therefore, in this study, we proposed an improved 3DP process that can solve problems of conventional 3DP process. The general 3DP process is method to spout binder simply through printer head on powder, but proposed process is method to cure jetted UV resin by UV lamp after jet UV resin using printhead on powder. The hardening of resin is achieved strongly at early time by UV lamp in proposed method. So, the proposed process can fabricate three dimensional objects with high speed without any post-processing.

• 한국지구과학회지
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• 제29권6호
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• pp.447-453
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• 2008

최근 제체 등의 수자원시설물에 대한 안정성 검토를 위해 전기비저항 탐사가 많이 수행되고 있다. 본 연구에서는 전기비저항 조사를 통해 제체의 안정성을 검토하고자할 때, 제체의 3차원 형상에 의한 효과를 정확히 분석하여야만 손상 구간을 파악할 수 있음을 제시하고자 한다. 이의 검토를 위해 3차원 전기비저항 모델링을 통해 3차원 형태의 제체 모양을 수치모델로 구현하고, 제체 내부의 상태에 따른 겉보기 비저항과 역산 결과를 분석하였다. 또한 실제 3차원 곡면 형태를 가진 제체에서 전기비저항 탐사를 수행하여 그 결과를 분석하였다. 그 결과, 단순히 2차원으로 해석하였을 때 이상대로 추정되었던 구간이, 실제로는 3차원 곡면에 의한 기하학적 효과였음이 밝혀졌으며, 3개월 뒤에 수행된 우기의 추가 조사와 추후 일부 굴착을 통하여 제체의 내부가 안전한 상태임을 확인하였다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.356-358
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• 2002

MRI, particularly diffusion weighted imaging (DWI), plays vital roles in detection of the acute brain infarction$\^$1-4/ and others metabolic changes of biological tissues. In general, every molecule in biological tissues may diffuse and move randomly in three-dimensional space. However, in clinical diagnosis, only 2D-DWI is used. The authors have developed a new method for rapid three-dimensional DWI (3D-DWI). In this method, by refocusing of the magnetized spin with the applied gradient field, direction of which is opposite to phase encoding field. Magnetized spin of $^1$H is kept under the SSFP (steady state free precession)$\^$5-6/. Under SSFP, in addition of FID, spin echo and stimulated echo are also generated, so the acquired signal is increased. The signal intensity is increased depending on flip angle (FA) of magnetized spin. This phenomenon is confirmed by human brain and phantom studies. The performance of this method is quantitatively analyzed by using both of conventional spin echo DWI and 3D-DWI. From experimental results, three dimensional diffusion weighted images are obtained correctly for liquid phantoms (water, acetone and oil), diffusion coefficient is enhanced in each image. Therefore, this method will provide useful information for clinical diagnosis.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.753-758
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• 2003

The purpose of the present study was to establish the mechanism of the generation of atherosclerosis by analyzing the hemodynamic variables in the coronary artery where atherosclerosis occurs frequently. From the previous results, the stenosis phenomena due to atherosclerosis were related to not only biochemical reaction between blood and blood vessel but also the hemodynamic factors like flow separation and oscillatory wall shear stress. The present study aimed to investigate the causes of the generation and progression of atherosclerosis in the coronary artery. This study also aimed to develop the softwares which generate automatically three dimensional vascular models obtained by the angiogram images and the computer vision techniques. In the present study, the flow patterns for full three-dimensional hemodynamic characteristics were analyzed. To understand the three-dimensional hemodynamic characteristics, the wall shear stress distributions and secondary flows were investigated quantitatively.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제21권3호
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• pp.125-142
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• 2017

In this paper, development of the three-dimensional structural analysis is performed by applying FETI-local method. In the FETI-local method, the penalty term is added as a preconditioner. The OPT-DKT shell element is used in the present structural analysis. Newmark-${\beta}$ method is employed to conduct the dynamic analysis. The three-dimensional FETI-local static structural analysis is conducted. The contour and the displacement of the results are compared following the different number of sub-domains. The computational time and memory usage are compared with respect to the number of CPUs used. The three-dimensional dynamic structural analysis is conducted while applying FETI-local method. The present results show appropriate scalability in terms of the computational time and memory usage. It is expected to improve the computational efficiency by combining the advantages of the original FETI method, i.e., FETI-mixed using the mixed local-global Lagrange multiplier.

• 대한인간공학회지
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• 제31권4호
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• pp.483-492
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• 2012

Objective: The aim of this study is to suggest three-dimensional(3D) hand gesture taxonomy to organize the user's intention of his/her decisions on deriving a certain gesture systematically. Background: With advanced technologies of gesture recognition, various researchers have studied to focus on deriving intuitive gestures for commands from users. In most of the previous studies, the users' reasons for deriving a certain gesture for a command were only used as a reference to group various gestures. Method: A total of eleven studies which categorized gestures accompanied by speech were investigated. Also a case study with thirty participants was conducted to understand gesture-features which derived from the users specifically. Results: Through the literature review, a total of nine gesture-features were extracted. After conducting the case study, the nine gesture-features were narrowed down a total of seven gesture-features. Conclusion: Three-dimensional hand gesture taxonomy including a total of seven gesture-features was developed. Application: Three-dimensional hand gesture taxonomy might be used as a check list to understand the users' reasons.

• 한국광학회지
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• 제20권6호
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• pp.328-333
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• 2009

본 논문에서는 복소수 홀로그램을 탈 축 홀로그램으로 변환해 쌍 영상 잡음 없이 3차원 홀로그램 디스플레이를 구현하는 방법 을 제안하고 실연하였다. 이러한 기술을 구현하기 위해, 서로 다른 깊이에 위치하는 슬라이드 패턴으로 구성된 3차원 물체의 복소수 홀로그램을 광 스캐닝 홀로그램 시스템을 이용해 추출한 후, 추출된 복소수 홀로그램에 공간 캐리어를 수치적인 방법으로 인가하고 실수 부분만을 추출해 복소수 홀로그램을 탈 축 홀로그램으로 변환한다. 변환된 탈 축 홀로그램을 진폭만을 변조하는 공간 광 변조기에 인가하고, 시준된 레이저 빔을 공간 광 변조기에 투사하여 탈 축 홀로그램을 복원하는 방식으로 3차원 디스플레이를 구현한다.

• 설비공학논문집
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• 제11권6호
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• pp.749-757
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• 1999

Holographic interferornetric tomography can provide reconstruction of instantaneous three dimensional gross flow fields. The technique however confronts ill-posed reconstruction problems in practical applications. Experimental data are usually limited in projection and angular scanning when a field is captured instantaneously or under the obstruction of test models and test section enclosures. An algorithm, based on a series expansion method, has been developed to improve the reconstruction under the ill-posed conditions. A three-dimensional natural convection flow around two interacting isothermal cubes is experimentally investigated. The flow can provide a challenging reconstruction problem and lend itself to accurate numerical solution for comparison. The refractive index fields at two horizontal sections of the thermal plume with and without an opaque object are reconstructed at a limited view angle of 80" The experimental reconstructions are then compared with those from numerical calculation and thermocouple thermometry. It confirms that the technique is applicable to reconstruction of reasonably complex, three-dimensional flow fields.elds.

• 한국측량학회지
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• 제21권4호
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• pp.341-346
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• 2003

인터넷으로 3차원 지도 정보를 제공하기 위해서는 먼저 웹 서버가 고려되어져야 하지만, 일반적으로, 어플리케이션의 소스코드는 비공개적이며 소스 기술에 대한 접근이 어려우므로 기술개발에 많은 한계가 있었다. 본 연구에서는 이런 문제를 해결하기 위해, 공개된 소스 체제인 Linux운영체제를 도입하였고, 웹 브라우저에서 3차원 공간데이터 실행이 가능한 VRLR을 활용하여 인터넷 3차원 지도 서버를 구축였다. 그 결과, 하드웨어 구입이외의 비용은 들지 않아 경제적이었으며, 개방된 소스를 이용하므로 능동적인 유지관리가 이루어 질 수 있었다.