Parametric Volume Models for Interactive Three-Dimensional Grid Generation

1994 ◽  
Author(s):  
Jawad D. Mokhtar ◽  
James H. Oliver
Keyword(s):  
Curve Surface ◽  
Three Dimensional ◽  
Grid Generation ◽  
Distribution Functions ◽  
Two Dimensional ◽  
Design Data ◽  
Point Distribution ◽  
Transfinite Interpolation ◽  
Initial Block ◽  
Block Construction

Abstract A method based on non-uniform rational B-spline (NURBS) curve, surface, and solid technology is presented for interactive grid generation of three-dimensional flow fields encountered in turbomachinery applications. The method allows construction of several types of multi-block grids including H-, O-, and C-grids for two-dimensional grids, and strict H-grids for three-dimensional grid generation. Automated two-dimensional block construction is facilitated via a traversal method that searches four-sided regions in the initial block structure. A NURBS surface is then constructed on each block by transfinite interpolation of the boundary curves themselves, and various point distribution options may be applied. Three-dimensional grid generation is an extension of the two-dimensional procedure. Tri-parametric hyperpatches (NURBS solids) are constructed from the two-dimensional block surfaces and grids may be generated via several point distribution functions. This method exploits existing geometric design data via Initial Graphics Exchange Specification (IGES) input of NURBS-based component geometry. It provides an efficient and robust method for complex grid generation to support a variety of analysis functions. Several example applications are presented to demonstrate the capabilities of the technique.

scholarly journals Visuo-spatial construction in patients with frontal and parietal lobe lesions

2011 ◽  
Author(s):  
Himani Kashyap ◽  
Keshav J. Kumar ◽  
Shobini L. Rao ◽  
B. Indira Devi
Keyword(s):  
Frontal Lobe ◽  
Parietal Lobe ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Parietal Lobes ◽  
Gender Education ◽  
Block Construction ◽  
Frontal Lesions ◽  
Spatial Construction ◽  
Larger Sample

Visuospatial construction, traditionally viewed as a putative parietal function, also requires sustained attention, planning, organization strategies and error correction, and hence frontal lobe mediation. The relative contributions of the frontal and parietal lobes are poorly understood. To examine the contributions of parietal, frontal lobes, as well as right and left cerebral hemispheres to visuospatial construction. The Stick Construction Test for two-dimensional construction and the Block Construction Test for three-dimensional construction were administered pre-surgically to patients with lesions in the parietal lobe (n = 9) and the frontal lobe (n = 11), along with normal control subjects (n = 20) matched to the patients on age (+⁄- 3 years), gender, education (+⁄- 3 years) and handedness. The patients were significantly slower than the controls on both two-dimensional and three-dimensional tests. Patients with parietal lesions were slower than those with frontal lesions on the test of three-dimensional construction. Within each lobe patients with right and left sided lesions did not differ significantly. It appears that tests of three-dimensional construction might be most sensitive to visuospatial construction deficits. Visuospatial construction involves the mediation of both frontal and parietal lobes. The function does not appear to be lateralized. The networks arising from the parieto-occipital areas and projecting to the frontal cortices (e.g., occipito-frontal fasciculus) may be the basis of the mediation of both lobes in visuospatial construction. The present findings need replication from studies with larger sample sizes.

Moving Boundary-Moving Mesh Analysis of Freezing Process in Water-Saturated Porous Media Using a Combined Transfinite Interpolation and PDE Mapping Methods

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
P. Rattanadecho ◽  
S. Wongwises
Keyword(s):  
Porous Media ◽  
Analytical Solution ◽  
Moving Boundary ◽  
Grid Generation ◽  
Experimental Results ◽  
Freezing Process ◽  
Saturated Porous Media ◽  
Two Dimensional ◽  
Transfinite Interpolation ◽  
Water Saturated

This paper couples the grid generation algorithm with the heat transport equations and applies them to simulate the thermal behavior of freezing process in water-saturated porous media. Focus is placed on establishing a computationally efficient approach for solving moving boundary heat transfer problem, in two-dimensional structured grids, with specific application to an undirectional solidification problem. Preliminary grids are first generated by an algebraic method, based on a transfinite interpolation method, with subsequent refinement using a partial differential equation (PDE) mapping (parabolic grid generation) method. A preliminary case study indicates successful implementation of the numerical procedure. A two-dimensional solidification model is then validated against available analytical solution and experimental results and subsequently used as a tool for efficient computational prototyping. The results of the problem are in good agreement with available analytical solution and experimental results.

scholarly journals Texture and Lamellae Distribution Functions in Lamellar Eutectics

1986 ◽  
Vol 6 (4) ◽  
pp. 265-287 ◽  
Author(s):  
H. J. Bunge
Keyword(s):  
Three Dimensional ◽  
Orientation Distribution ◽  
Distribution Functions ◽  
X Rays ◽  
Two Dimensional ◽  
Absorption Factor ◽  
X Ray Diffraction ◽  
Diffraction Vector ◽  
X Ray ◽  
Pole Figures

The crystallographic orientation distribution and the geometrical lamellae orientation distribution in lamellar eutectics are, in general, not independent of each other. The combined orientation-lamellae distribution function depends on five angular parameters. X-ray diffraction in such eutectics may exhibit an anisotropic macroscopic absorption factor if the penetration depth of the X-rays is large compared with their planar size. As a consequence, the reflected X-ray intensity may depend on a third angle γ, i.e. a rotation of the sample about the diffraction vector s additionally to the usual pole figure angles α, β which describe the orientation of the diffraction vector s with respect to the sample coordinate system. It is thus necessary to measure three-dimensional generalized pole figures instead of conventional two-dimensional ones.

PADRAM: Parametric Design and Rapid Meshing System for Turbomachinery Optimisation

2003 ◽  
Author(s):  
Shahrokh Shahpar ◽  
Leigh Lapworth
Keyword(s):  
Parametric Design ◽  
Three Dimensional ◽  
Grid Generation ◽  
Optimization Process ◽  
Design System ◽  
Two Dimensional ◽  
Generation System ◽  
Design Optimisation ◽  
Structured Grid ◽  
Turbomachinery Blades

A parametric design system suitable for inclusion in an automatic optimization process is presented. The system makes use of a multi-block structured grid generation system specially designed for the rapid meshing of two-dimensional, quasi-three-dimensional, and three-dimensional single passage as well as multi-passage, multi-row turbomachinery blades. Full annulus viscous meshes of the order of five to ten million mesh points for the complete bypass assembly of the low pressure compression (LPC) system can be generated in a matter of minutes. PADRAM offers a major new design capability where the optimisation of multi-passage three-dimensional blades and its circumferential pattern is done simultaneously in one system. Successful usage of PADRAM in a number of design, optimisation and analysis applications has recently been demonstrated and reported herein.

Two-Dimensional Orthogonal Grid Generation

2012 ◽  
Vol 468-471 ◽  
pp. 2668-2671
Author(s):  
Y.L. Liu ◽  
K. Bai ◽  
Xi Wang ◽  
Ming Qin Liu
Keyword(s):  
Grid Generation ◽  
Test Problems ◽  
Two Dimensional ◽  
Point Distribution ◽  
Good Balance ◽  
Control Functions ◽  
Orthogonal Grid ◽  
Finite Difference Discretization ◽  
Generating System ◽  
Difference Discretization

A method for nearly orthogonal grid generation is presented in this study. The generating system is based on solution of a system of partial differential equations with finite difference discretization. The grid quality control functions and grid properties are investigated. Specification of both boundary point distribution on all sides is used. The proposed method is applied to various test problems，which shows this method provides a good balance between controlling grid orthogonality and cell aspect ratio.

Communicating Spatial Relations Using Online Chat

2018 ◽  
pp. 233-282
Author(s):  
Theodor Wyeld
Keyword(s):  
Qualitative Analysis ◽  
Coordinate System ◽  
Qualitative Methodology ◽  
Three Dimensional ◽  
Spatial Relations ◽  
Two Dimensional ◽  
Online Chat ◽  
Spatial Expressions ◽  
Block Construction ◽  
Spatial Terms

The block construction exercises described in this chapter were used to investigate how spatial communication about the manipulation of objects in virtual, physical, and graphical space is communicated using online text. Where this study differs from previous research in the area is in its use of a qualitative methodology to investigate how these types of interactions are structured, communicated, and interpreted via text-based media. What emerges from the qualitative analysis is new insights over the previous quantitative investigations. More particularly, this mode of investigation has revealed the apparent superior efficacy of the fragmenting of three-dimensional spatial arrangements into two-dimensional planar representations using a simple ABC123 grid-wise coordinate system. The spatial terms used by participants in their textual communications are filtered according to Lefebvre's thirdspace and deictic spatial expressions.

High Resolution Microscopy of Multi-Layered Biological Crystals

1982 ◽  
Vol 40 ◽  
pp. 80-83
Author(s):  
H.A. Cohen ◽  
T.W. Jeng ◽  
W. Chiu
Keyword(s):  
High Resolution ◽  
Low Dose ◽  
Three Dimensional ◽  
Data Interpretation ◽  
Two Dimensional ◽  
Biological Objects ◽  
Density Maps ◽  
Density Map ◽  
Complex Crystal ◽  
High Resolution Microscopy

This tutorial will discuss the methodology of low dose electron diffraction and imaging of crystalline biological objects, the problems of data interpretation for two-dimensional projected density maps of glucose embedded protein crystals, the factors to be considered in combining tilt data from three-dimensional crystals, and finally, the prospects of achieving a high resolution three-dimensional density map of a biological crystal. This methodology will be illustrated using two proteins under investigation in our laboratory, the T4 DNA helix destabilizing protein gp32*I and the crotoxin complex crystal.

Instrumentation For Quantitative Microscopy

1977 ◽  
Vol 35 ◽  
pp. 206-209
Author(s):  
B. Ralph ◽  
A.R. Jones
Keyword(s):  
Volume Fraction ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Automatic Data ◽  
Phase Volume Fraction ◽  
Statistical Confidence ◽  
Resultant Data ◽  
Automatic Data Collection ◽  
Third Dimension ◽  
Evolution Of Microstructure

In all fields of microscopy there is an increasing interest in the quantification of microstructure. This interest may stem from a desire to establish quality control parameters or may have a more fundamental requirement involving the derivation of parameters which partially or completely define the three dimensional nature of the microstructure. This latter categorey of study may arise from an interest in the evolution of microstructure or from a desire to generate detailed property/microstructure relationships. In the more fundamental studies some convolution of two-dimensional data into the third dimension (stereological analysis) will be necessary.In some cases the two-dimensional data may be acquired relatively easily without recourse to automatic data collection and further, it may prove possible to perform the data reduction and analysis relatively easily. In such cases the only recourse to machines may well be in establishing the statistical confidence of the resultant data. Such relatively straightforward studies tend to result from acquiring data on the whole assemblage of features making up the microstructure. In this field data mode, when parameters such as phase volume fraction, mean size etc. are sought, the main case for resorting to automation is in order to perform repetitive analyses since each analysis is relatively easily performed.

A linearity test for thick specimens imaged by HVEM over a 180° angular range

1991 ◽  
Vol 49 ◽  
pp. 552-553
Author(s):  
Yu Liu
Keyword(s):  
Phase Contrast ◽  
Three Dimensional ◽  
Angular Range ◽  
Two Dimensional ◽  
Back Projection ◽  
Line Integral ◽  
Exponential Law ◽  
Transmission Electron ◽  
Absorption Law ◽  
Linearity Test

The image obtained in a transmission electron microscope is the two-dimensional projection of a three-dimensional (3D) object. The 3D reconstruction of the object can be calculated from a series of projections by back-projection, but this algorithm assumes that the image is linearly related to a line integral of the object function. However, there are two kinds of contrast in electron microscopy, scattering and phase contrast, of which only the latter is linear with the optical density (OD) in the micrograph. Therefore the OD can be used as a measure of the projection only for thin specimens where phase contrast dominates the image. For thick specimens, where scattering contrast predominates, an exponential absorption law holds, and a logarithm of OD must be used. However, for large thicknesses, the simple exponential law might break down due to multiple and inelastic scattering.

An Image Reconstruction System Applied to High Voltage Microscopy

1975 ◽  
Vol 33 ◽  
pp. 292-293
Author(s):  
D. E. Johnson
Keyword(s):  
High Voltage ◽  
Prior Information ◽  
Block Diagram ◽  
Three Dimensional ◽  
Real Space ◽  
Two Dimensional ◽  
Efficient Manner ◽  
Fourier Methods ◽  
Tilt Series ◽  
Methods Of Reconstruction

Increased specimen penetration; the principle advantage of high voltage microscopy, is accompanied by an increased need to utilize information on three dimensional specimen structure available in the form of two dimensional projections (i.e. micrographs). We are engaged in a program to develop methods which allow the maximum use of information contained in a through tilt series of micrographs to determine three dimensional speciman structure.In general, we are dealing with structures lacking in symmetry and with projections available from only a limited span of angles (±60°). For these reasons, we must make maximum use of any prior information available about the specimen. To do this in the most efficient manner, we have concentrated on iterative, real space methods rather than Fourier methods of reconstruction. The particular iterative algorithm we have developed is given in detail in ref. 3. A block diagram of the complete reconstruction system is shown in fig. 1.

Sign in / Sign up

Export Citation Format

Share Document