Improved Methods for Determining the 3 Dimensional Initial Shapes of Cable-Supported Bridges

김문영,김동영,정명락,Mario M. Attard 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.1

The TCUD method (Kim and Lee, 2001) can minimize undesirable lateral displacements in cable bridge structures byincluding the unstrained lengths of the cable members as unknowns and introducing additional constraint conditions. The axialdeformations in the girder and the main tower deviating from the target configuration are, however, unavoidable when selfanchoredcable bridges are considered. On the other hand, the IFM (initial force method) can be used to adjust the axialdeformations to conform to the initial shape but it is critical that the unstrained lengths of the cables are accurately evaluated. In this study, improved schemes for the TCUD method and the IFM for finding the initial shape of 3 dimensional cablesupportedbridges under dead load, are presented. For this purpose, the TCUD method and the initial force method are firstlyreviewed. Two improved algorithms, which can overcome shortcomings of the previous initial-shaping analysis methods, aredeveloped based on an elastic catenary cable element and a nonlinear space frame element. Finally, the accuracy andeffectiveness of the proposed analysis algorithms are demonstrated through the numerical application to 3 dimensional initialshape problems for self-anchored suspension and cable-stayed bridges.

Automatic Initialization Active Contour Model for the Segmentation of the Chest Wall on Chest CT

최석윤,김창수 대한의료정보학회 2010 Healthcare Informatics Research Vol.16 No.1

Objectives: Snake or active contours are extensively used in computer vision and medical image processing applications, and particularly to locate object boundaries. Yet problems associated with initialization and the poor convergence to boundary concavities have limited their utility. The new method of external force for active contours, which is called gradient vector flow (GVF), was recently introduced to address the problems. Methods: This paper presents an automatic initialization value of the snake algorithm for the segmentation of the chest wall. Snake algorithms are required to have manually drawn initial contours, so this needs automatic initialization. In this paper, our proposed algorithm is the mean shape for automatic initialization in the GVF. Results: The GVF is calculated as a diffusion of the gradient vectors of a gray-level or binary edge map derived from the medical images. Finally, the mean shape coordinates are used to automatic initialize thepoint of the snake. The proposed algorithm is composed of three phases: the landmark phase, the procrustes shape distance metric phase and aligning a set of shapes phase. The experiments showed the good performance of our algorithm in segmenting the chest wall by chest computed tomography. Conclusions: An error analysis for the active contours results on simulated test medical images is also presented. We showed that GVF has a large capture range and it is able to move a snake into boundary concavities. Therefore, the suggested algorithm is better than the traditional potential forces of image segmentation.

기하학적 방법을 이용한 초기 박판형상 추정

정동원,안현길 제주대학교 공과대학 첨단기술연구소 2005 尖端技術硏究所論文集 Vol.16 No.2

A method is described for mapping a three-dimensional computer modelled surface into the two-dimensional plane. The technique is referred to as geometric modelling and provides in the computer a transformation between the flat sheet and the final surface. The initial blank shape represents an approximate development of the final formed three dimensional surface. It was used the initial constant area mapping hypothesis in this paper. This technique is intended to be developed as the basis of an interactive computer design capable of dealing with typical stamping process, including deep parts and complex shapes.

기하학적 방법을 이용한 초기 박판형상 추정

정동원(Dong-Won Jung),이상제(Sang-Je Lee) 한국해양공학회 1999 韓國海洋工學會誌 Vol.13 No.3(Ⅰ)

In this paper, method for mapping a three-dimensional shape into the two-dimensional plane will be introduced. This method is referred to geometric modelling and means a transformation between the flat sheet and the final surface. The initial blank shape represents the original configuration of the final shape formed into three dimensional surface. The initial constant area mapping hypothesis was used in this paper. This technique will be applied to the basic data for an interactive computer design capable of dealing with typical stamping process, including deep parts and complex shapes.

막 구조물의 비선형해석을 통한 안전성 검토와 파손면의 응력집중

전진형,정을석,손수덕,김승덕 대한건축학회지회연합회 2005 대한건축학회지회연합회 학술발표대회논문집 Vol.1 No.1

membrane has strong axial stiffness, but little bending stiffness. Therefore membrane structures are unstable structures initially. These soft structures need to be introduced initial stresses first because of its initial unstable state, and it happens large deformation phenomenon. To find the structural shape after large deformation caused by initial stiffness introduced, we need the shape analysis considering geometric nonlinearity in structural design procedure. In this study, we have done the shape analysis and the stress-deformation analysis of the membrane structures and then study the safety by the NASS(Nonlinear Analysis for Spatial Structures) which is the program for nonlinear analysis. And also we investigate into the stress concentration at crack of the structures and stress distribution for creak length investigate

A Python-based Docking Program Utilizing a Receptor Bound Ligand Shape: PythDock

정재윤,하정미,조승주 대한약학회 2011 Archives of Pharmacal Research Vol.34 No.9

PythDock is a heuristic docking program that uses Python programming language with a simple scoring function and a population based search engine. The scoring function considers electrostatic and dispersion/repulsion terms. The search engine utilizes a particle swarm optimization algorithm. A grid potential map is generated using the shape information of a bound ligand within the active site. Therefore, the searching area is more relevant to the ligand binding. To evaluate the docking performance of PythDock, two well-known docking programs (AutoDock and DOCK) were also used with the same data. The accuracy of docked results were measured by the difference of the ligand structure between x-ray structure, and docked pose, i.e., average root mean squared deviation values of the bound ligand were compared for fourteen protein-ligand complexes. Since the number of ligands’ rotational flexibility is an important factor affecting the accuracy of a docking, the data set was chosen to have various degrees of flexibility. Although PythDock has a scoring function simpler than those of other programs (AutoDock and DOCK), our results showed that PythDock predicted more accurate poses than both AutoDock4.2 and DOCK6.2. This indicates that PythDock could be a useful tool to study ligand-receptor interactions and could also be beneficial in structure based drug design.

Coronal flaring 전, 후 초기근관장 파일크기의 분석

황호길,박찬호,배성철 大韓齒科保存學會 2003 Restorative Dentistry & Endodontics Vol.28 No.1

The purpose of this study was to compare the inital apical file(IAF) first file that fits to the apex in each canal before and after early flaring to analyze if the size of file to fit to the apex would increase after flaring. Eighty anterior teeth with complete apical formation and patent foramens were selected. The samples were randomly divided into 4 groups(GG, OS, GT, PT Group) of 20 teeth each. A file was fit to the apex in each canal and that size recorded. Radicular flaring were completed using different types of instruments. After flaring a file was again fit to the apex in the same manner as before and its size recorded. The results of this study were as follows: 1. The mean diameter of IAF before flaring(file diameters in mm ×10^-2) was 19.81±8.32 before and 25.94±9.21 after(p<0.05). 2. The increase in diameter of IAF was approximately one file size for all groups. 3. Ranking of increasing diameter of IAF were GG>GT>OS>PT Group. There was a statistically significant difference between before and after flaring(p<0.05). 4. Ranking of the time for flaring were GG>GT>OS>PT group. There was a statistically significant difference between GG group and other groups(p<0.05). 5. In the case without change of IAF diameter, they showed decrease in force after flaring when IAF was pulled out from root canal(p<0.05). This study suggested that early radicular flaring increases the file size that is snug at the apex, and awareness of that difference gives the clinical a better sense of canal size. Early flaring of the canal provides better apical size information and with this awareness, a better decision can be made concerning the appropriate final diameter needed for complete apical shaping.

Finite element procedure of initial shape determination for hyperelasticity

Yamada, Takahiro Techno-Press 1998 Structural Engineering and Mechanics, An Int'l Jou Vol.6 No.2

In the shape design of flexible structures, it is useful to predict the initial shape from the desirable large deformed shapes under some loading conditions. In this paper, we present a numerical procedure of an initial shape determination problem for hyperelastic materials which enables us to calculate an initial shape corresponding to the prescribed deformed shape and boundary condition. The present procedure is based on an Arbitrary Lagrangian-Eulerian (ALE) finite element method for hyperelasticity, in which arbitrary change of shapes in both the initial and deformed states can be treated by considering the variation of geometric mappings in the equilibrium equation. Then the determination problem of the initial shape can be formulated as a nonlinear problem to solve the unknown initial shape for the specified deformed shape that satisfies the equilibrium equation. The present approach can be implemented easily to the finite element method by employing the isoparametric hypothesis. Some basic numerical results are also given to characterize the present procedure.

Investigation on deck-stay interaction of cable-stayed bridges with appropriate initial shapes

Liu, Ming-Yi,Lin, Li-Chin,Wang, Pao-Hsii Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.5

This paper provides a variety of viewpoints to illustrate the mechanism of the deck-stay interaction with the appropriate initial shapes of cable-stayed bridges. Based on the smooth and convergent bridge shapes obtained by the initial shape analysis, the one-element cable system (OECS) and multi-element cable system (MECS) models of the Kao Ping Hsi Bridge in Taiwan are developed to verify the applicability of the analytical model and numerical formulation from the field observations in the authors' previous work. For this purpose, the modal analysis of the two finite element models are conducted to calculate the natural frequency and normalized mode shape of the individual modes of the bridge. The modal coupling assessment is also performed to obtain the generalized mass ratios among the structural components for each mode of the bridge. The findings indicate that the coupled modes are attributed to the frequency loci veering and mode localization when the "pure" deck-tower frequency and the "pure" stay cable frequency approach one another, implying that the mode shapes of such coupled modes are simply different from those of the deck-tower system or stay cables alone. The distribution of the generalized mass ratios between the deck-tower system and stay cables are useful indices for quantitatively assessing the degree of coupling for each mode. These results are demonstrated to fully understand the mechanism of the deck-stay interaction with the appropriate initial shapes of cable-stayed bridges.

Investigation on deck-stay interaction of cable-stayed bridges with appropriate initial shapes

Ming-Yi Liu,Li-Chin Lin,Pao-Hsii Wang 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.5

This paper provides a variety of viewpoints to illustrate the mechanism of the deck-stay interaction with the appropriate initial shapes of cable-stayed bridges. Based on the smooth and convergent bridge shapes obtained by the initial shape analysis, the one-element cable system (OECS) and multi-element cable system (MECS) models of the Kao Ping Hsi Bridge in Taiwan are developed to verify the applicability of the analytical model and numerical formulation from the field observations in the authors’ previous work. For this purpose, the modal analysis of the two finite element models are conducted to calculate the natural frequency and normalized mode shape of the individual modes of the bridge. The modal coupling assessment is also performed to obtain the generalized mass ratios among the structural components for each mode of the bridge. The findings indicate that the coupled modes are attributed to the frequency loci veering and mode localization when the “pure” deck-tower frequency and the “pure” stay cable frequency approach one another, implying that the mode shapes of such coupled modes are simply different from those of the deck-tower system or stay cables alone. The distribution of the generalized mass ratios between the deck-tower system and stay cables are useful indices for quantitatively assessing the degree of coupling for each mode. These results are demonstrated to fully understand the mechanism of the deck-stay interaction with the appropriate initial shapes of cable-stayed bridges.