• International Journal of CAD/CAM
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• v.8 no.1
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• pp.29-36
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• 2009

Domain mapping is a bijective transformation of one domain to another, usually from a complicated general domain to a chosen convex domain. This is directly useful in many application problems like shape modeling, morphing, texture mapping, shape matching, remeshing, path planning etc. A new approach considering the domain as made up of structural elements, like membranes or trusses, is developed and implemented using the nonlinear finite element formulation. The mapping is performed in two stages, boundary mapping and inside mapping. The boundary of the 3-D domain is mapped to the surface of a convex domain (in this case, a sphere) in the first stage and then the displacement/distortion of this boundary is used as boundary conditions for mapping the interior of the domain in the second stage. This is a general method and it develops a bijective mapping in all cases with judicious choice of material properties and finite element analysis. The consistent global parameterization produced by this method for an arbitrary genus zero closed surface is useful in shape modeling. Results are convincing to accept this finite element structural approach for domain mapping as a good method for many purposes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.9
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• pp.859-869
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• 2015

In this study, we analyze the problem of wedge cracks, which are geometrically unsymmetrical in transversely piezoelectric materials. A single concentrated antiplane mechanical load and inplane electrical load are applied at the point of the wedge surface, while one concentrated antiplane load is applied at the crack surface. The crack surfaces are considered as permeable thin slits, where both the normal component of electric displacement and the electric potential are assumed to be continuous across these slits. Using Mellin transform method, the problem is formulated and the Wiener-Hopf equation is derived. By solving the equation, the solution is obtained in a closed form. The intensity factors of the stress and the electric displacement are obtained for any crack length as well as inclined and wedge angles. Based on the results, the intensity factors are independent of the applied electric loads. The electric displacement intensity factor is always dependent on that of stress intensity factor, while the electric field intensity factor is zero. In addition, the energy release rate is computed. These solutions can be used as fundamental solutions which can be superposed to arbitrary electromechanical loadings.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.427-434
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• 2000

This paper presents a computer program for a 2-D fluid-structure-soil interaction analysis. With this computer program the fluid can be modeled by a spurious free 4-node displacement-based fluid element which uses rotational penalty and mass projection technique in conjunction with the one point reduced integration scheme to remove the spurious zero energy modes. The structure and near field soil are discretized by the standard finite elements while the unbounded far field soil are discretized by the standard finite elements while the unbounded far field soil is represented by the frequency dependent dynamic infinite elements. Sine this method models directly the fluid-structure-soil system it can be applied to the dynamci analysis of 2-D liquid storage structure with complex geometry. For the purpose of verification dynamic analyses for tanks on a rigid foundation and on compliant embankment are carried out. Comparison of the present results with those by ANSYS program shows good agreement.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10b
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• pp.973-980
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• 1988

This two-part paper presents a control method that allows for stable interaction of a robot manipulator with the environment. In part 1, we focus on the input ouput relationships (unstructured modeling) of the robot and environment dynamics. This analysis leads to a general condition for stability of the robot and environment taken as a whole. This stability condition, for stable maneuver, prescribes a finite sensitivity for robot and environment where sensitivity of the robot(or the environment) is defined as a mapping forces into displacement. According to this stability condition, smaller sensitivity either in robot or in environment leads to narrower stability range. In the limit, when both systems have zero sensitivity, stability cannot be guaranteed. These models do not have any particular structure, yet they can model a wide variety of industrial and research robot manipulators and environment dynamic behavior. Although this approach of modeling may not lead to any design procedure, it will allow us to understand the fundamental issues in stability when a robot interacts with an environment.

• Journal of Korean Association for Spatial Structures
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• v.3 no.2 s.8
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• pp.101-107
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• 2003

There exists a structural problem for link structures in the unstable state. The primary characteristics of this problem are in the existence of rigid body displacements without strain, and in the possibility of the introduction of prestressing to change an unstable state into a stable state. When we make local linearized incremental equations in order to obtain knowledge about these unstable structures, the determinant of the coefficient matrices is zero, so that we face a numerically unstable situation. This is similar to the situation in the stability problem. To avoid such a difficult situation, in this paper a simple and straightforward method was presented by means of the generalized inverse for the numerical analysis of stability problem.

• Geomechanics and Engineering
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• v.21 no.1
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• pp.85-93
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• 2020

In this article, the generalized thermoelastic theory with fractional derivative is presented to estimate the variation of temperature, the components of stress, the components of displacement and the changes in volume fraction field in two-dimensional porous media. Easily, the exact solutions in the Laplace domain are obtained. By using Laplace and Fourier transformations with the eigenvalues method, the physical quantities are obtained analytically. The numerical results for all the physical quantities considered are implemented and presented graphically. The results display that the present model with the fractional derivative is reduced to the Lord and Shulman (LS) and the classical dynamical coupled (CT) theories when the fractional parameter is equivalent to one and the delay time is equal to zero and respectively.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.11
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• pp.941-949
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• 1989

This two-part paper presents a control method that allows for stable interaction of a robot manipulator with environment. In part 1, we focus on the input output relationships (unstructured modeling) of the robot and environment dynamics. This analysis leads to a general condition for stability of the robot and environment taken as a whole. This stability condition, for stable maneuver, prescribes a finite sensitivity for robot and environment where sensitivity of the robot (or the environment) is defined as a mapping forces into displacement. According to this stability condition, smaller sensitivity either in robot or in environment leads to narrower stability range. In the limit, when both systems have zero sensitivity, stability cannot be guaranteed. These models do not have any particular structure, yet they can model a wide variety of industrial and research robot manipulators and environment dynamic behavior. Although this approach of modeling may not lead to and design procedure, it will allow us to understand the fundamental issues in stability when a robot interacts with an environment.

• Proceedings of the Korea Water Resources Association Conference
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• 2002.05b
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• pp.1027-1033
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• 2002

The solute transport in a two-dimensional heterogeneous porous medium is numerically studied by using a random walk particle tracking (RWPT) method. Lognormally isotropic hydraulic conductivity fields are generated by using the turning band methods with mean zero and four different values of standard deviation. The numerical transport experiments are carried out to investigate the large time and spatial effects of the variable pore velocity field on solute plumes. The behavior of the solute plume through numerical simulations is presented in terms of longitudinal and transverse spatial moments: displacement of center-of-mass, plume spread variance and skewness coefficient. It was observed that the dispersive behavior of the solute plume is strongly affected by the degree of heterogeneity in the flow domain.

• Korean Journal of Remote Sensing
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• v.19 no.5
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• pp.363-370
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• 2003

This paper describes a rectification procedure that relies on a polynomial model derived from the imaging geometry without loss of accuracy. By using polynomial model, one can effectively eliminate the iterative process to find an image pixel corresponding to each output grid point. With the imaging geometry and ephemeris data, a geo-location polynomial can be constructed from grid points that are produced by solving three equations simultaneously. And, in order to correct the local distortions induced by the geometry and terrain height, a distortion model has been incorporated in the procedure, which is a function of incidence angle and height at each pixel position. With this function, it is straightforward to calculate the pixel displacement due to distortions and then pixels are assigned to the output grid by re-sampling the displaced pixels. Most of the necessary information for the construction of polynomial model is available in the leader file and some can be derived from others. For validation, sample images of ERS-l PRI and Radarsat-l SGF have been processed by the proposed method and evaluated against ground truth acquired from 1:25,000 topography maps.

• Coupled systems mechanics
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• v.8 no.1
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• pp.19-38
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• 2019

The influence of torsional rigidity of hinged flexible appendage on the linear dynamics of flexible spacecrafts with liquid on board was analyzed by considering the spacecraft's main body as a rigid tank, its flexible appendages as two elastically supported elastic beams, and the onboard liquid as an ideal liquid. The meniscus of the liquid free surface due to surface tension was considered. Using the Lagrangian of the spacecraft's main body (rigid tank), onboard liquid, and two beams (flexible appendages) in addition to assuming the system moved symmetrically, the coupled system frequency equations were obtained by applying the Rayleigh-Ritz method. The influence of the torsional rigidity of the flexible appendages on the spacecraft's coupled vibration characteristics was primary focus of investigation. It was found that coupled vibration modes especially that of appendage considerably changed with torsion spring parameter ${\kappa}_t$ of the flexible appendage. In addition, variation of the main body displacement with system parameters was investigated.