Contour Nodes Research Articles

Designing the working surfaces of rotary planetary mechanisms

Purpose. To design a method for smoothing the working surfaces of stator and rotor with the use of computer simulation to eliminate the impact of the rotor on the stator when they interact. Methodology. Special and general methods of research have been used: interpolation of the point series – to determine the contour nodes of the rotor and the stator of the rotary-planetary machine; formation of B-splines – to construct a point series whose coordinates are structurally determined; technology of automated formation of curves in CAD-system SolidWorks – for modelling of functional surfaces of a planetary-rotary compressor. Findings. Algorithms for formation of the contours representing curves defined analytically or constructively with a given accuracy have been developed. The obtained contours are used in the CAD system as linear elements of the surface model. The developed method has been tested in the simulation of functional surfaces of a planetary-rotary compressor. Optimization of the body shape and rotor profiles in order to increase the productivity of the rotary-planetary machine has been carried out. Originality. The developed algorithms make it possible to determine the original point series belonging to any curve and provide a given interpolation accuracy when forming a B-spline contour or second-order curve arcs. Computer models of the body surfaces of the rotor are formed on the basis of the gear ratio of the planetary-rotary mechanism and the rotor dimensions. In order to increase the performance of the compressor, the working surfaces of the rotor have been optimized. The maximum volume of the working chamber was increased by increasing the radius of the moving gear of the planetary-rotary mechanism. In order to prevent the rotor from jamming during compressor operation, the rotor contour was changed. Practical value. The method for modelling the surfaces of complex shape in CAD-system has been developed on the basis of creating contours which with given accuracy represent lines from the surface determinant. This method makes it possible to form computer models of complex surfaces on the basis of a framework consisting of curves absent in CAD libraries.

A Contour Interpolation Method Based on the Nearest Distance Method to Construct Auxiliary Lines

The regional interpolation method calculates the characteristic distance of the contour nodes to complete the node matching, divides the contour into multiple regions with consistent change trends, and constructs auxiliary lines equally within the region to complete the interpolation. Aiming at the uncertainty of the area divided by the regional interpolation method and the redundancy of the auxiliary line constructed, a contour interpolation method using the nearest distance method to construct the auxiliary line is proposed. Firstly, the Doiglas-Peucker algorithm is used to extract the feature points of the contour line, and the nearest distance method is used to construct the auxiliary line for the feature points, and then the new contour line is interpolated. The nearest distance method constructs the auxiliary line based on the distance between the feature point and the feature point. The auxiliary line can reflect the change trend of the contour line, so that the new contour line can retain the curve features of the original contour line. Compared with the regional interpolation method, the method in this paper has a single uncertainty factor and the auxiliary lines constructed are simple and efficient, which improves the interpolation efficiency. Through experimental comparison, the effectiveness of the method is verified.

3D ultrasonic reconstruction of contour node represented voids and cracks

Although the 2D imaging technology was widely used, it cannot provide enough information for protecting cultural relics. Base on the homogeneous material assumption, 3D contour node is therefore proposed to represent defects of different shapes inside the cultural relics. This paper describes a novel algorithm to reconstruct 3D image of defects inside cultural relics combined with dynamic chain technology and two algorithms: Simultaneous Iterative Reconstruct Technique (SIRT) and Adaptive Moment Estimation(Adam). And the latter is used to improve the former. Meanwhile, a detection scheme is designed like this : Firstly, rough position of defects will be searched, and then precise reconstruction is made for defective areas. The algorithm proposed is verified by simulation experiments. With application of the algorithm, 3D images of defects of different shapes and quantities can be obtained and the errors of reconstruction, in most cases, are lower than 10%, even the maximum error is lower than 22%. Finally, the laboratory experiment also tests the ability of the proposed algorithm. The reconstruction is done by using conventional ultrasonic probes instead of array probes which can reduce the detection cost.

Efficient order-adaptive methods for polymer self-consistent field theory

A highly accurate and memory-efficient approach for the solution of polymer self-consistent field theory (SCFT) is proposed. The central idea is to combine spectral integration in the polymer chain contour variable with a spectral deferred correction technique to solve the SCFT modified diffusion equations with arbitrarily high order of accuracy. The result is a robust method that achieves high accuracy with a minimal number of discrete contour nodes, which translates into vastly reduced memory requirements and increased computational efficiency. In particular, this spectral deferred correction method enables the computation of strongly segregated systems with unprecedented accuracy. Moreover, the framework of deferred corrections allows us to adaptively increase the order of accuracy during the outer saddle point iteration to drastically reduce the cost of a SCFT computation.

COATINGS DISCRETE SURFACES CONSTRUCTION BY SUPERPOSITIONS OF ADJUSTED MESH FRAMES

The method of curve surface discrete geometric modeling on the basis of two discrete frames superimpositions, formed by a static-geometric method, and on the basis of a single surface curve nodal points superimposition, also formed by static-geometric method, is considered. It has been determined that the suggested method allows to model balanced discrete structures formed on the specified contour nodes, as well as those passing through the specified nodal points without composing and solving equations systems.

Ultrasonic detection of contour node represented voids and cracks

In current evaluation of ancient stone monuments, 2-D ultrasonic tomography is widely used. The detection result, however, has deviation in the location and the shape since the ultrasonic velocity of voids and cracks area change much more drastic than the healthy parts. Base on the homogeneous material assumption, a contour node representation is therefore proposed fitting the best defect shape and location. With the contour node representation, a quick ray tracing method is proposed. This inverse problem is solved under the Bayesian framework in which we use Markov chain Monte Carlo to search the global optimal result. Through applying more prior knowledge to the model and the quick ray tracing model, the computational cost of the inverse process is highly reduced. Compared to the ultrasonic tomography result, the proposed method has more accurate location and shape in 2-D inspection. Finally, the laboratory experiment also tests the ability of the proposed method.

A numerical solution for plain problems of theory of elasticity

In this paper ,a generation of a numerical algorithm for solving theory of elasticity plain problem concerning displacements is desired ; using difference equations that the method of successive approximations proceed through transforming a complex ( to be solved ) differential equation into an algebraic one that’s much more easier to solve. The algebraic equations resulted adopt both positioned nodes; interior nodes of a computational grid, and contour ( boundary ) nodes; including corner ones. The evaluation of the new generated algorithm is being validated through applying it on solving a problem of a laterally fixed deep-beam. Obtained numerical results out of the new algorithm to be compared with those early known and stated in the references listed at the last part of the article.

AN IMPROVED SNAKE MODEL FOR REFINEMENT OF LIDAR-DERIVED BUILDING ROOF CONTOURS USING AERIAL IMAGES

Building roof contours are considered as very important geometric data, which have been widely applied in many fields, including but not limited to urban planning, land investigation, change detection and military reconnaissance. Currently, the demand on building contours at a finer scale (especially in urban areas) has been raised in a growing number of studies such as urban environment quality assessment, urban sprawl monitoring and urban air pollution modelling. LiDAR is known as an effective means of acquiring 3D roof points with high elevation accuracy. However, the precision of the building contour obtained from LiDAR data is restricted by its relatively low scanning resolution. With the use of the texture information from high-resolution imagery, the precision can be improved. In this study, an improved snake model is proposed to refine the initial building contours extracted from LiDAR. First, an improved snake model is constructed with the constraints of the deviation angle, image gradient, and area. Then, the nodes of the contour are moved in a certain range to find the best optimized result using greedy algorithm. Considering both precision and efficiency, the candidate shift positions of the contour nodes are constrained, and the searching strategy for the candidate nodes is explicitly designed. The experiments on three datasets indicate that the proposed method for building contour refinement is effective and feasible. The average quality index is improved from 91.66% to 93.34%. The statistics of the evaluation results for every single building demonstrated that 77.0% of the total number of contours is updated with higher quality index.

AN IMPROVED SNAKE MODEL FOR REFINEMENT OF LIDAR-DERIVED BUILDING ROOF CONTOURS USING AERIAL IMAGES

Abstract. Building roof contours are considered as very important geometric data, which have been widely applied in many fields, including but not limited to urban planning, land investigation, change detection and military reconnaissance. Currently, the demand on building contours at a finer scale (especially in urban areas) has been raised in a growing number of studies such as urban environment quality assessment, urban sprawl monitoring and urban air pollution modelling. LiDAR is known as an effective means of acquiring 3D roof points with high elevation accuracy. However, the precision of the building contour obtained from LiDAR data is restricted by its relatively low scanning resolution. With the use of the texture information from high-resolution imagery, the precision can be improved. In this study, an improved snake model is proposed to refine the initial building contours extracted from LiDAR. First, an improved snake model is constructed with the constraints of the deviation angle, image gradient, and area. Then, the nodes of the contour are moved in a certain range to find the best optimized result using greedy algorithm. Considering both precision and efficiency, the candidate shift positions of the contour nodes are constrained, and the searching strategy for the candidate nodes is explicitly designed. The experiments on three datasets indicate that the proposed method for building contour refinement is effective and feasible. The average quality index is improved from 91.66% to 93.34%. The statistics of the evaluation results for every single building demonstrated that 77.0% of the total number of contours is updated with higher quality index.

An edge-based active contour model using an inflation/deflation force with a damping coefficient

This publication presents an edge-based active contour model using the inflation/deflation force, allowing active contour nodes to be moved to find object boundaries in a digital image. The methods proposed in this study make it possible to keep a high value of the inflation/deflation force for each node until the node approaches the boundary of the analysed shape. After the boundary searched for is reached, the value of the inflation/deflation force for these nodes is automatically damped. The solutions used in this paper are of major practical significance if the analysed images contain weak boundaries and/or strong noise at the same time, and on top of that there are strictures of the shape which should be approximated. Experiments were carried out for artificial images as well as USG and MRI medical images, and have confirmed the suitability of the solutions used.

STL Representation of Axisymmetric Solid Element Mesh

This paper develops an algorithm for extracting stereolithography (STL) model from axisymmetric solid finite element (FE) mesh, so as to use 3D physical prototype instead of computer graphics-based visualization to express the deformation result of FE simulation. The key of the algorithm is to recognize contour node pairs from an axisymmetric solid element mesh, which exactly demonstrates that the proposed methodology is independent of axisymmetric element configuration, that is to say, it is applicable for either triangular, quadrilateral, or mixed triangular and quadrilateral axisymmetric solid element mesh.

A natural neighbour method based on Fraeijs de Veubeke variational principle for materially non-linear problems

The natural neighbour method can be considered as one of many variants of the meshless methods. In the present paper, a new approach based on the Fraeijs de Veubeke (FdV) functional, which is initially developed for linear elasticity, is extended to the case of geometrically linear but materially non-linear solids. The new approach provides an original treatment to two classical problems: the numerical evaluation of the integrals over the domain A and the enforcement of boundary conditions of the type ui = ũi on Su. In the absence of body forces (Fi = 0), it will be shown that the calculation of integrals of the type \({\int\nolimits_A \cdot {\rm d}A}\) can be avoided and that boundary conditions of the type ui = ũi on Su can be imposed in the average sense in general and exactly if ũi is linear between two contour nodes, which is obviously the case for ũi = 0.