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991.
Jung Seo Park Jong Gye Shin Chung Min Hyun Young Chil Doh Kwang Hee Ko 《Computer aided design》2009,41(12):907-917
Various problems associated with localization during curved plate fabrication are discussed. Localization is a necessary step for automation of curved plate fabrication that aligns a designed shape with a fabricated one as closely as possible for comparison of their shapes. On top of this localization, various conditions are introduced to reflect requirements occurring during fabrication such as minimum cutting length, maintenance of cutting length, localization for non-penetration and data types for localization. Each condition is formulated as a constraint which is provided as input to the optimization problem for localization. Algorithms for localization with each constraint based on iteration are proposed. Examples are used to demonstrate the performance of the algorithms. 相似文献
992.
Hyun-Jung Kim Yu-Deok Seo Sung-Kie Youn 《Computer Methods in Applied Mechanics and Engineering》2010,199(45-48):2796-2812
Trimming technique is a powerful and efficacious way of endowing an arbitrary complex topology to CAD files created by using NURBS. In the present work, it is shown that any complex multiply-connected NURBS domain can be described by using trimming curves only. Isogeometric analysis for linear elasticity problems of complex topology described in this way is presented. For fully communicative interaction between CAD and CAE, a specific searching algorithm and an integration scheme of trimmed elements are introduced to utilize the IGES files exported from CAD system for Isogeometric analysis. Schemes for imposing essential and traction boundary conditions on trimming curves are presented. It has been demonstrated that with the presented schemes trimmed cases in any complicated situations can be successfully treated. With the examples of complex topology that could be described by employing trimming curves only, effectiveness and robustness of present method are demonstrated. 相似文献
993.
The development of a sliding joint for very flexible multibody dynamics using absolute nodal coordinate formulation 总被引:1,自引:0,他引:1
Soo-Ho Lee Tae-Won Park Jong-Hwi Seo Ji-Won Yoon Kab-Jin Jun 《Multibody System Dynamics》2008,20(3):223-237
In this paper, a formulation for a spatial sliding joint is derived using absolute nodal coordinates and non-generalized coordinate
and it allows a general multibody move along a very flexible cable. The large deformable motion of a spatial cable is presented
using absolute nodal coordinate formulation, which is based on the finite element procedures and the general continuum mechanics
theory to represent the elastic forces. And the nongeneralized coordinate, which is related to neither the inertia forces
nor the external forces, is used to describe an arbitrary position along the centerline of a very flexible cable. Hereby,
the non-generalized coordinate represents the arc-length parameter. The constraint equations for the sliding joint are expressed
in terms of generalized coordinate and nongeneralized coordinate. In the constraint equations for the sliding joint, one constraint
equation can be systematically eliminated. There are two independent Lagrange multipliers in the final system equations of
motion associated with the sliding joint. The development of this sliding joint is important to analyze many mechanical systems
such as pulley systems and pantograph-catenary systems for high speed-trains. 相似文献
994.
In optimization problems, the contribution of a variable to fitness often depends on the states of other variables. This phenomenon is referred to as epistasis or linkage. In this paper, we show that a new theory of epistasis can be established on the basis of Shannon's information theory. From this, we derive a new epistasis measure called entropic epistasis and some theoretical results. We also provide experimental results verifying the measure and showing how it can be used for designing efficient evolutionary algorithms. 相似文献
995.
Van Phuoc Phan Nam Seo Goo Hoon Cheol Park 《International Journal of Control, Automation and Systems》2009,7(2):243-251
The increasing demand for high-speed performance and low energy consumption has necessitated the design of lightweight mechanical
systems. The active vibration suppression of a flexible manipulator is important in many engineering applications, such as
robot manipulators and high-speed flexible mechanisms, because the flexibility of lightweight manipulators induces a vibration
problem. Frequently, the optimal parameters determined for a certain control algorithm might not cover a wide range of operating
conditions. Hence, we have proposed and developed a lookup table control method for a flexible manipulator that can tune itself
to optimal parameters on the basis of the initial maximum responses of the controlled system and a genetic algorithm. The
genetic algorithm is used to search for optimal parameters with regard to positive position feedback and thereby minimizes
the objective functions determined from the initial maximum responses. Our lookup table, which has the optimal parameters
of the positive position feedback as a function of the initial maximum responses, can be used in a real-time control algorithm.
Recommended by Editorial Board member Hyoukryeol Choi under the direction of Editor Jae-Bok Song. This work was supported
by the Korea Research Foundation under grant KRF 2006-005-J03302 and the Korea Science and Engineering Foundation under grant
KOSEF R0A-2007-000-20012-0.
Van Phuoc Phan received the BS (2006) from the Department of Aeronautical Engineering, HCM University of Technology, Vietnam. Currently,
he is a Master student at the Department of Advanced Technology Fusion, Konkuk University in Seoul, Korea. His interests are
structural dynamics of small systems, smart structure and material, and finite element analysis.
Nam Seo Goo graduated from the Department of Aeronautics Engineering of Seoul National University with honors in 1990, and got master
and Ph.D. degrees in Department of Aerospace Engineering at the same university in 1992 and 1996, respectively. His Ph.D.
degree was on the structural dynamics of aerospace systems. As soon as he got a Ph.D. degree, he entered the agency for defense
development as a Senior Researcher. After four years’ service, he joined Department of Aerospace Engineering in Konkuk University,
Seoul, Korea in 2002, currently serving an Associate Professor of Department of Advanced Technology Fusion. His current research
interests are structural dynamics of small systems, smart structure and material, and MEMS applications.
Hoon Cheol Park received his BS (1985) and MS(1987) degrees from Seoul National University in Seoul, Korea and Ph.D.(1994) degree from the
University of Maryland at College Park, MD, USA. He joined the Department of Aerospace Engineering, Konkuk University in Seoul,
Korea in 1995, and he is currently a Professor in the Department of Advanced Technology Fusion. His professional experience
includes Kia Motors (1986–1988) and Korea Aerospace Research Institute (1994–1995). His specialty is the finite element analysis
and recent research topic is mainly biomimetics. 相似文献
996.
Dongkyung Nam Yun Deuk Seo Lae-Jeong Park Cheol Hoon Park Burnsup Kim 《Evolutionary Computation, IEEE Transactions on》2001,5(4):414-421
This paper presents an application of evolutionary programming to parameter optimization in the design of a voltage reference circuit. Designing circuits consists of two steps: topological design and parameter determination. After designing a topology suitable for the circuit, the designer selects an appropriate value for each circuit element from a circuit analysis and his experience. This step is difficult and time consuming because the designer must consider many factors simultaneously. As more precise circuits are required, parameter optimization becomes more complex. The voltage reference circuit, which requires a precise reference voltage independent of power fluctuation and temperature change, is such an example. In this paper, evolutionary programming is used as an effective method of finding good parameter values for the elements of the voltage reference circuit. Simulation results show that this method provides good performance and can be used as an effective method for circuit design 相似文献
997.
Knowledge discovery in high-dimensional data is a challenging enterprise, but new visual analytic tools appear to offer users remarkable powers if they are ready to learn new concepts and interfaces. Our three-year effort to develop versions of the hierarchical clustering explorer (HCE) began with building an interactive tool for exploring clustering results. It expanded, based on user needs, to include other potent analytic and visualization tools for multivariate data, especially the rank-by-feature framework. Our own successes using HCE provided some testimonial evidence of its utility, but we felt it necessary to get beyond our subjective impressions. This paper presents an evaluation of the hierarchical clustering explorer (HCE) using three case studies and an e-mail user survey (n=57) to focus on skill acquisition with the novel concepts and interface for the rank-by-feature framework. Knowledgeable and motivated users in diverse fields provided multiple perspectives that refined our understanding of strengths and weaknesses. A user survey confirmed the benefits of HCE, but gave less guidance about improvements. Both evaluations suggested improved training methods. 相似文献
998.
We present an explicit form of nonlinear observers for a class of multi-input multi-output systems. Observer construction for multi-output nonlinear systems is not a trivial extension of single output case, especially when the global error convergence is of interest. In this paper, we consider a class of systems in which the subsystem for each output has a triangular dependence on the states of that subsystem itself, and the overall system has a block triangular form for each subsystem. Hence, the contribution is to extend the results existing in the literature in that interconnections between the subsystems are allowed. The construction is based on the saturation of some estimates, which is originated by Khalil and Esfandiari for the use of semi-global output feedback control. 相似文献
999.
Calibration-free augmented reality in perspective 总被引:3,自引:0,他引:3
Yongduek Seo Ki Sang Hong 《IEEE transactions on visualization and computer graphics》2000,6(4):346-359
This paper deals with video-based augmented reality and proposes an algorithm for augmenting a real video sequence with views of graphics objects without metric calibration of the video camera by representing the motion of the video camera in projective space. A virtual camera, by which views of graphics objects are generated, is attached to a real camera by specifying image locations of the world coordinate system of the virtual world. The virtual camera is decomposed into calibration and motion components in order to make full use of graphics tools. The projective motion of the real camera recovered from image matches has the function of transferring the virtual camera and makes the virtual camera move according to the motion of the real camera. The virtual camera also follows the change of the internal parameters of the real camera. This paper shows the theoretical and experimental results of our application of nonmetric vision to augmented reality 相似文献
1000.
Characterization of electromagnetic properties of polymeric composite materials with free space method 总被引:9,自引:0,他引:9
The introduction of microwave radars during the second World War altered the air defense scenario significantly, and this led to the development of the “stealth” techniques. By reducing the detectability of aircrafts or warships, of which the radar cross section (RCS) is a measure, they could evade radar detection, which affected not only the mission success rate but also survival of them in the hostile territory. In the very early stage of the research on stealth techniques, many researches were mainly concentrated on the reduction of RCS and development of radar absorbing materials (RAM), but nowadays studies on investigating the radar absorbing structures (RAS) using fiber reinforced polymeric composite materials are becoming popular research field.
In this study, electromagnetic characteristics of unidirectional E-glass fiber reinforced epoxy composites were tested with free space methods, which can overcome drawbacks of conventional cavity and waveguide methods. Complex relative permittivities of low-loss composite were measured with respect to the angle between the fiber orientation and the electric field vector of EM wave in X-band frequency range. From the experimental data, empirical relation between the dielectric properties of composites and test variable was suggested and verified. 相似文献