This paper presents an algorithm of the point constraint for B-spline surfaces. Based on static energy model, the shape of the surface can be sculpted in an intuitive manner by changing the force distribution vector a...
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ISBN:
(纸本)9781424415304
This paper presents an algorithm of the point constraint for B-spline surfaces. Based on static energy model, the shape of the surface can be sculpted in an intuitive manner by changing the force distribution vector and control point constraint, thus this method provides the user with a familiar interface for modifying the shape. Furthermore, in order to impose surface point constraints upon the B-spline surface, optimization object function is built based on the least square method, and force distribution vector is used as optimization variable. Several calculation examples are demonstrated to verify and show the capabilities of the developed model.
This paper presents an algorithm of the point constraint for B-spline *** on static energy model, the shape of the surface can be sculpted in an intuitive manner by changing the force distribution vector and control p...
详细信息
ISBN:
(纸本)9781424415304
This paper presents an algorithm of the point constraint for B-spline *** on static energy model, the shape of the surface can be sculpted in an intuitive manner by changing the force distribution vector and control point constraint,thus this method provides the user with a familiar interface for modifying the ***,in order to impose surface point constraints upon the B-spline surface, optimization object function is built based on the least square method,and force distribution vector is used as optimization *** calculation examples are demonstrated to verify and show the capabilities of the developed model.
Remote sensing images contain abundant land cover information. Due to the complex nature of land cover, however, mixed pixels exist widely in remote sensing images. Sub-pixel mapping (SPM) is a technique for predictin...
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Remote sensing images contain abundant land cover information. Due to the complex nature of land cover, however, mixed pixels exist widely in remote sensing images. Sub-pixel mapping (SPM) is a technique for predicting the spatial distribution of land cover classes within mixed pixels. As an ill-posed inverse problem, the uncertainty of prediction cannot be eliminated and hinders the production of accurate sub-pixel maps. In contrast to conventional methods that use continuous geospatial information (e.g., images) to enhance SPM, in this paper, a SPM method with point constraints into SPM is proposed. The method of fusing point constraints is implemented based on the pixel swapping algorithm (PSA) and utilizes the auxiliary point information to reduce the uncertainty in the SPM process and increase map accuracy. The point data are incorporated into both the initialization and optimization processes of PSA. Experiments were performed on three images to validate the proposed method. The influences of the performances were also investigated under different numbers of point data, different spatial characters of land cover and different zoom factors. The results show that by using the point data, the proposed SPM method can separate more small-sized targets from aggregated artifacts and the accuracies are increased obviously. The proposed method is also more accurate than the advanced radial basis function interpolation-based method. The advantage of using point data is more evident when the point data size and scale factor are large and the spatial autocorrelation of the land cover is small. As the amount of point data increases, however, the increase in accuracy becomes less noticeable. Furthermore, the SPM accuracy can still be increased even if the point data and coarse proportions contain errors.
We present a novel approach for dealing with optimal approximate merging of two adjacent Bezier eurves with G^2-continuity. Instead of moving the control points, we minimize the distance between the original curves an...
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We present a novel approach for dealing with optimal approximate merging of two adjacent Bezier eurves with G^2-continuity. Instead of moving the control points, we minimize the distance between the original curves and the merged curve by taking advantage of matrix representation of Bezier curve＇s discrete structure, where the approximation error is measured by L2-norm. We use geometric information about the curves to generate the merged curve, and the approximation error is smaller. We can obtain control points of the merged curve regardless of the degrees of the two original curves. We also discuss the merged curve with point constraints. Numerical examples are provided to demonstrate the effectiveness of our algorithms.
In this paper, a unified method is proposed to predict the free and forced vibration behavior of the combined conical-cylindrical shell (CCS) structure in the steady-state thermal environment. The first-order shear de...
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In this paper, a unified method is proposed to predict the free and forced vibration behavior of the combined conical-cylindrical shell (CCS) structure in the steady-state thermal environment. The first-order shear deformation theory (FSDT) and the thermal strain are utilized to establish the energy equation of the combined structure, and the artificial virtual spring technique is introduced to realize the coupling between the substructures and the arbitrary boundary conditions of the CCS. The displacement function of the structure is constructed by the spectral-geometry method, and the vibration equation is solved by using the Rayleigh-Ritz method. The accuracy of the present model is verified by comparing the numerical results with the finite element method. The factors that may affect the vibration behavior of the CCS under thermal environment are analyzed specifically, and the results demonstrate that point constraints on the shell surface can effectively suppress shell vibration. This paper provides a compelling reference for vibration control of CCS in practical applications.
In the case of arbitrary traction on the side faces of an object, a polynomial function of the radial coordinate can be employed to describe the side-face loads using the scaled boundary finite element method (SBFEM)....
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In the case of arbitrary traction on the side faces of an object, a polynomial function of the radial coordinate can be employed to describe the side-face loads using the scaled boundary finite element method (SBFEM). A SBFEM shape function considering the side-face loads is presented together with the corresponding stiffness matrix and equivalent node load. The Lagrange multiplier method is used to establish the contact model between the crack faces. The elements corresponding to the crack faces are divided into non-crack-tip elements and crack-tip elements. For the former, the crack is designated the boundary of the polygonal SBFEM element;the contact tractions on the boundary are assigned to the nodes where the Lagrange multiplier is applied for the point constraints. For the latter, the Lagrange multiplier is assumed to be linear on the side faces for the segment constraints. Numerical examples demonstrate the validity of the proposed SBFEM in addressing the crack face contact problem. (C) 2017 Elsevier B.V. All rights reserved.
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