103 results about "Quadrilateral meshes" patented technology

The invention discloses a method for meshing point cloud data. In the method, aiming at discrete point cloud data obtained by laser scanning, an automatic global parameterization method with strong robustness is provided, and a parameterization result is used for directly acquiring a meshing result which is consistent with a main direction and can reflect intrinsic geometric characteristics of a model. The meshing result has two forms, i.e., the meshing result can be wholly formed by quadrangles, or formed by triangles. By using the method, only the point cloud data of the model is used, prior triangulation is not needed to perform point cloud data meshing, the processing procedure is completely automatic, point clouds containing noises can be processed without manual intervention, and the density level of quadrangle meshing can be quickly controlled through parameters to obtain quadrilateral meshes or triangular meshes with various resolution ratios.

The invention relates to a China Tang dynasty style historic building modeling method. Firstly, a historic building model based on point clouds is layered, and similar layers of the historic building model are clustered to obtain different constituent parts of a historic building; then symmetry of the historic building is used for conducting missing data filling on the different constituent parts; straight lines and circles are extracted through the Hough conversion and the least square method respectively to achieve primary analytic curve surface reconstruction; same points are selected for each layer according to characteristics of the points on each layer, a quadrilateral mesh model is formed according to coordinate position relations, and free curve surface reconstruction is achieved; finally, photorealistic rendering of the historic building is achieved through a texture mapping method.

The invention discloses a reconstruction method for a three-dimensional quadrilateral mesh model on the basis of an image. The method comprises the following steps that: (1) obtaining point cloud datawhich represents an image object or a scene appearance, and recovering the three-dimensional image of an image; and (2) constructing the quadrilateral mesh of the point cloud data, and reconstructingthe quadrilateral mesh model. The method has the advantages that the method has an effect on fitting the better image object or scene.

The invention discloses a quick generation method of a three-dimensional printing slice contour of a triply periodic minimal surface. The method comprises the steps of inputting an expression of the triply periodic minimal surface to be sliced, slice thickness and a slice quadrilateral mesh resolution, generating slice quadrilateral meshes of an area corresponding to the surface according to a co-ordinate distribution range of the triply periodic minimal surface and the slice thickness, calculating slice line segments of the surface and each slice quadrilateral mesh by linear interpolation according to the expression of the surface, storing a topological relationship between the slice line segments and quadrangles in the corresponding slice quadrilateral meshes, sorting all the slice linesegments, and at last, outputting the slice contour generated after sorting in a CLI (common layer interface) file format for storage. The method achieves quick slicing of the triply periodic minimalsurface and quick sorting of scattered slice line segments by using the slice quadrilateral meshes, quickly generates the three-dimensional printing slice contour, and avoids the disadvantages of consumption of much time and a large memory space due to generation of an STL (standard template library) model in the traditional method.

The invention discloses an automatic generation method for a quadrilateral finite element mesh of a pitting corrosion damage cylindrical shell. The automatic generation method for the quadrilateral finite element mesh of the pitting corrosion damage cylindrical shell includes that carrying out parameterization set on key geometrical sizes of a pitting corrosion damage cylindrical shell model in a finite element software, constructing three standard basic segments of an end perfecting region, a pitting corrosion region and a pitting corrosion spacer region of the cylindrical shell through segregate expression, constructing the whole geometrical model of the pitting corrosion damage cylindrical shell with a multi-layer pitting corrosion region, the pitting corrosion spacer region and the end perfecting region through copying, translation and division methods, grouping the geometrical model according to pit positions and size characteristics of each region, setting the mesh division number of the region boundary of each grouping object, using mapping MAPPED and AMAP to divide the whole cylindrical shell model, and generating the whole finite element model of the quadrilateral mesh unit. The automatic generation method for the quadrilateral finite element mesh of the pitting corrosion damage cylindrical shell solves the microscopic pitting corrosion damage description problem in a macro-scale structure and improves the solving precision and solving efficiency of the simulating calculation.

The invention relates to a numerical simulation method for obtaining aircraft flow fields, wherein an interrupted Galerkin method based on non-structural right angle meshes is used to solve the flow field, and right angle meshes with a quadtree structure are used to disperse a to-be-solved flow field area into a set of meshes; each quadrilateral mesh is processed by dual-linear coordinate conversion, so each mesh under a current physical coordinate system can be mapped onto the next regular mesh in a computational coordinate system, so standard square meshes can be obtained; conservation variables in units under the computational coordinate system are obtained through numerical computation; a front face, a lower face, a left face and a right face of each mesh under the physical coordinate system are determined; according to differences between the left and right vibrations of unit interfaces, an interrupted detector is established; and the conservation variables in each mesh are processed by flow field display on the disperse meshes, so flow field distribution can be obtained. According to the invention, the interrupted Galerkin method based on the non-structural right angle meshes is introduced into flow field computation, so accuracy of the flow field computation is increased, and complicated flow phenomena can be solved.

The invention provides a method of clipping quadrilateral grids of a coal seam by a triangular grid of an open-pit mine stope, and relates to the technical field of coal seam geology. According to themethod, firstly, the quadrilateral grids of coal seam roof and floor interfaces and the triangular grid of the open-pit mine stope are generated; then intersecting-line polygons obtained by intersection of the triangular grid and the quadrilateral grids are generated, and sorted counterclockwise to obtain clipping polygons; and finally, the clipping polygons are used to clip the quadrilateral grids of the coal seam roof and floor interfaces to realize updating for a coal seam geology model. According to the method of clipping the quadrilateral grids of the coal seam by the triangular grid ofthe open-pit mine stope provided by the invention, the problem that intersecting lines of quadrilateral curved surfaces and triangular surfaces are space curves is effectively solved, and practical application is enabled to be realized. The method of directly utilizing the triangular grid to clip the quadrilateral grids highly efficiently realizes, on the premise of not increasing a storage amount, operations of clipping the quadrilateral grids by the triangular grid.

The invention relates to the technical field of complex river network flow field numerical simulation, and discloses a complex river network shunting numerical simulation method. The method comprises the steps that by means of a two-dimensional non-constant shallow water equation set, a quadrilateral mesh and triangular mesh hybrid network system is built, and a finite volume method is used for performing dispersion, so that a planar two-dimensional numerical model of a complex river network is built, and actual water flow motion features in the river network are simulated; by means of measured data rate, a simulated result is determined, and related parameters of the model are determined; then, shunting nonuniform coefficient measuring flow distributed features are introduced, and shunting nonuniform coefficients of a plurality of shunting joints in the river netework are calculated. In this way, the problems that spatial limits of a one-dimensional model are caused and the three-dimensional model calculation time cost is excessively large are avoided, and the defect that the mass and momentum partial non-conservation phenomenon of a multi-dimensional coupling model in linkage appears is overcome.

The invention discloses an iteration generation method of a hexahedral mesh model. The iteration generation method comprises the following steps: step one, inputting a triangular mesh model, constructing an initial hexahedral mesh model according to the triangular mesh model, and extracting a surface quadrilateral mesh from the initial hexahedral mesh model; step 2, carrying out iterative fitting of the surface quadrilateral mesh of the initial hexahedral mesh model on the triangular mesh model and carrying out mobile diffusion on mesh peaks of the surface quadrilateral mesh so as to obtain an intermediate hexahedral mesh model that is divided into multiple layers of quadrilateral meshes; and step three, inserting a layer of quadrilateral mesh between the surface quadrilateral mesh of the intermediate hexahedral mesh model and the internal first-layer quadrilateral mesh and optimizing all layers of the quadrilateral meshes except the surface quadrilateral mesh so as to obtain a final hexahedral mesh model. According to the invention, with the method, a hexahedral mesh with the guaranteed quality can be obtained; and the automation degree is improved.

The invention discloses a repeat mode discovery-based printed pattern generation method. The method comprises the following steps of: carrying out repeat mode discovery on an input printed image set so as to discover an object-class image mode which repeatedly emerges in the image set; constructing a layout template for a repeat object, carrying out multi-granularity quadrilateral mesh generation and optimum layout solution on the profile of an input printed pattern through iterative loop, and calculating an object optimum layout which satisfies a printed pattern constraint condition; and calculating affine transformation of living example of the object and a hierarchical relationship between the living examples during the splicing according to the position and dimension of the template in the layout, so as to carry out living example drawing to realize the synthesis of the printed pattern.

The invention provides a method for parameterizing a quadrilateral grid in a conformal mode. The method is used for directly parameterizing a curved surface of the quadrilateral grid, and comprises the following steps that S11 a quadrilateral grid is input, S12 borders of the quadrilateral grid are parameterized with the length maintained to obtain a border condition, S13 an angle system of the quadrilateral grid is solved to obtain angle input of a conformal energy function, and S14 the conformal energy function is constructed, and the quadrilateral grid is grid-parameterized according to the conformal energy function. According to the method for parameterizing the quadrilateral grid in the conformal mode, the quadrilateral grid can be directly parameterized, not every quadrilateral needs to be divided to two triangles, and the curved surface is parameterized according to a triangular grid parameterizing method.

Techniques for coarsening a quadrilateral mesh are described. These techniques include identifying a coarsening region within the quadrilateral mesh to be coarsened. Quadrilateral elements along a path through the coarsening region are removed. Node pairs along opposite sides of the path are identified. The node pairs along the path are then merged to collapse the path.

The invention discloses a structure of a composite reinforcement pile capable of resisting a budge of a foundation and a construction method. By adopting the structure of the composite reinforcement pile capable of resisting the budge of the foundation and the construction method, deformation of the bulge of the foundation is effectively weakened or eliminated, the running risk of high-speed trains is reduced, and the reduction on the construction cost of the high-speed railways is facilitated. The structure of the composite reinforcement pile comprises a fine aggregate concrete perfusion bodyand a composite reinforcement cage embedded in the fine aggregate concrete perfusion body, wherein the composite reinforcement cage is prepared from vertical geogrids which are circumferentially arranged at intervals and annular geogrids which are vertically arranged at intervals; the vertical geogrids and the annular geogrids are connected integrally in a convergent manner; quadrilateral mesh holes are formed between the two adjacent vertical geogrids and the two adjacent annular geogrids; and the diameters of inscribed circles of the mesh holes are not less than the maximum particle diameters of fine stone concrete aggregates. The fine aggregate concrete perfusion body is formed by perfusing fine stone concrete into foundation drill holes from the composite reinforcement cage, and a protective layer is formed between an outer wall of the composite reinforcement cage and hole walls of the foundation drill holes.

A process for simulating the motion of a first fluid, a second fluid and an interface between the first fluid and the second fluid. The fluid velocities and pressures of the first and second fluids are calculated at a first set of nodes on a first mesh at a first time step, representative of movement of the first and second fluids at the first time step. The level set, which is representative of a position of the interface, is calculated at the first time step, at a second set of nodes on a second mesh. The second mesh is odd times finer than the first mesh. The new fluid velocities and pressures of the first and second fluids are calculated at the first set of nodes at a second time step, representative of new movement of the first and second fluids at a second time step. The new level set is calculated at the second set of nodes, representative of a new position of the interface at the second time step.

The invention discloses a hexagon image reconstruction method based on compressed sensing and is mainly used for solving edge blur and false colour phenomena in the existing image reconstruction method. The hexagon image reconstruction method based on compressed sensing comprises the following steps of: firstly converting a quadrilateral mesh image into a hexagon mesh image x by adopting a pixel grid piecing method; then observing and sampling the converted hexagon mesh image x by adopting a measurement matrix PHI to obtain a sampling value; and finally according to the sampling value, calculating pixel values for reconstructing an image by an orthogonal matching method, and obtaining a reconstructed image. According to the hexagon image reconstruction method based on compressed sensing, correlation between a space dimension and a spectral dimension of an image is utilized for overcoming the marginal sawtooth phenomenon in the existing image reconstruction method, and the hexagon image reconstruction method based on compressed sensing has the advantages of high information utilization ratio and low algorithm complexity and can be applied to acquisition of images in a digital camera.

The invention discloses a similarity transformation-based relocated image quality evaluation method. The method comprises the following steps of: establishing a matching relationship between an original image and a relocated image so as to obtain a reconstructed relocated image; establishing a matching relationship between the relocated image and the original image so as to obtain a reconstructedoriginal image; obtaining a similarity transformation matrix of each quadrilateral mesh in the original image and the relocated image; obtaining a visual saliency map of each of the original image andthe relocated image; obtaining forward geometric distortion, backward geometric distortion, forward information loss and backward information loss according to above information; and finally fusing the forward geometric distortion, the backward geometric distortion, the forward information loss and the backward information loss so as to obtain an objective quality evaluation predicted value of the relocated image. The method has the advantage of effectively improving relevance between objective evaluation results and subjective perceptions.

The invention discloses a quadrilateral meshing method for a plane vector field. The quadrilateral meshing method comprises the main steps of: inputting a plane vector field F, determining a plane area [omega] and a group of process control parameters for performing meshing treatment on F; rasterizing an extended rectangular bounding box covering the area [omega]; respectively generating a streamline set of the vector field F and an orthogonal dual vector field G thereof according to flow field and control parameters; determining an intersection point of the streamlines of F and G in each grid unit, and respectively interposing the obtained intersection points into the corresponding positions of the related streamlines; extracting surface patches of plane meshes interwoven by the intersection points and the streamlines; partitioning the non-quadrilateral mesh surface patches in the meshes, and thereby generating meshes in which quadrilateral units are predominant; generating plane quadrilateral meshes by subdividing the meshes. According to the quadrilateral meshing method, quadrilateral meshing of any plane vector fields can be achieved; the quadrilateral meshing method is simple in principle, easy to implement, and capable of automatically generating quadrilateral meshed with uniform surface patches.

Embodiments of the present invention provide a finite difference method, a finite element projection, and a non-finite-element implementation of the finite element projection for solving the incompressible continuity equation on quadrilateral grids to obtain pressure and fluid velocity. An exemplary apparatus for simulating and analyzing the flow of an incompressible fluid is also provided. More particularly, embodiments of the present invention provide a non-finite-element-method (non-FEM) to implement the finite element projection to obtain a linear system whose coefficient matrix has an average bandwidth of five, in comparison to the finite difference scheme using conventional finite element projection and implementation with a bandwidth of nine. A two-dimensional-five-point-stencil-based non-FEM discretization is formulated to enforce the incompressible continuity equation. A shape function that is different from a weighting function used in the incompressible continuity equation is utilized to guarantee the five-point-stencil discretization is possible. The smaller bandwidth of the non-FEM scheme requires less computing resources and can compute the results in a reduced time duration, due to the simpler matrix to solve.

The invention provides an assembled type prestressed aluminum alloy single-layer latticed shell structure. The structure comprises H-shaped aluminum rod parts and plate type pitch points; the H-shaped aluminum rod parts are interconnected through the plate pitch points to form a quadrilateral surface mesh; a pulling cable is arranged on each diagonal line of the quadrilateral mesh; the pulling cables are connected with the quadrilateral surface mesh through the plate type pitch points, so as to form the assembled type prestressed aluminum alloy single-layer latticed shell structure. With the adoption of the assembled type prestressed aluminum alloy single-layer latticed shell structure, the quantity of steel used and the difficulty at the structure construction are obviously reduced; the weakening effect of a bolt is reduced by 33%, so that the bearing capacity of the pitch points is improved.

The invention discloses a jetting height error compensation method for large-area micro-nano structure electrohydrodynamics printing. The jetting height error compensation method comprises the following steps that (1) the number of constrained points of a base plate is determined; (2) the coordinate value z of the Z axis of the constrained points of the base plate is obtained; (3) a quadrilateral mesh of an XY plane is built; (4) the coordinate value z<j> of the Z axis of the vertex of the quadrilateral mesh of the XY plane is determined; (5) a three-dimensional curved surface of the printing area of the base plate is built; (6) the coordinate value z<c> of the Z axis of the current position of the printing base plate is obtained; and (7) the jetting height of electrohydrodynamics printing is compensated. According to the jetting height error compensation method for large-area micro-nano structure electrohydrodynamics printing, limitation of the existing electrohydrodynamics printing technology to precise forming of a device of a large-area micro-nano structure is broken through, and ink-jet printing of a micro-nano device of a large-area structure and preparation of a device of a micro-nano structure are achieved.