Reference Shape Research Articles

Assessment of missile hazards: Evaluation of the fragment number and drag factors

An approach was proposed for the assessment of the expected number and drag factor of fragments generated in the collapse of a vessel due to internal pressure. The analysis of a database reporting data on more than 140 vessel fragmentation events allowed the identification of a limited number of fragment reference shapes. The correlation of fragment reference shapes to the vessel credible fragmentation patterns allowed the assessment of the expected number and reference shape of fragments generated. Starting from the fragment reference shapes identified, simplified functions for drag factor calculation were developed, based on few geometrical parameters of the vessel undergoing the fragmentation event. The probabilistic models for the expected shape and number of fragments generated and the simplified drag factor functions developed may constitute an important input for the analysis of the possible fragment trajectories in the framework of missile hazard assessment.

Shape recognition using fuzzy string-matching technique

Object recognition is a very important task in industrial applications. Attributed string matching is a well-known technique for pattern matching. The present paper proposes a fuzzy string-matching approach for two-dimensional object recognition. The fuzzy numbers are used to represent the edit costs. Therefore, the edit distances are also presented as fuzzy numbers. The attributed string-matching problem is then equivalent to a fuzzy shortest path problem. The edit distance between two shapes is presented as a fuzzy number. By ranking the fuzzy edit distances, the input shape is classified as the reference shape that has the minimum fuzzy edit distance. The experimental results show that the proposed method can effectively recognize two-dimensional objects.

신경회로망기법을 사용한 엇갈린 딤플 유로의 최적설계

This study presents a numerical procedure to optimize the shape of staggered dimple surface to enhance turbulent heat transfer in a rectangular channel. The RBNN method is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer with shear stress transport (SST) turbulence model. The dimple depth-to-dimple print diameter (d/D), channel height-to-dimple print diameter ratio (H/D), and dimple print diameter-to-pitch ratio (D/S) are chosen as design variables. The objective function is defined as a linear combination of heat transfer related term and friction loss related term with a weighting factor. Latin Hypercube Sampling (LHS) is used to determine the training points as a mean of the design of experiment. The optimum shape shows remarkable performance in comparison with a reference shape.

Fast 3D shape screening of large chemical databases through alignment-recycling.

BackgroundLarge chemical databases require fast, efficient, and simple ways of looking for similar structures. Although such tasks are now fairly well resolved for graph-based similarity queries, they remain an issue for 3D approaches, particularly for those based on 3D shape overlays. Inspired by a recent technique developed to compare molecular shapes, we designed a hybrid methodology, alignment-recycling, that enables efficient retrieval and alignment of structures with similar 3D shapes.ResultsUsing a dataset of more than one million PubChem compounds of limited size (< 28 heavy atoms) and flexibility (< 6 rotatable bonds), we obtained a set of a few thousand diverse structures covering entirely the 3D shape space of the conformers of the dataset. Transformation matrices gathered from the overlays between these diverse structures and the 3D conformer dataset allowed us to drastically (100-fold) reduce the CPU time required for shape overlay. The alignment-recycling heuristic produces results consistent with de novo alignment calculation, with better than 80% hit list overlap on average.ConclusionOverlay-based 3D methods are computationally demanding when searching large databases. Alignment-recycling reduces the CPU time to perform shape similarity searches by breaking the alignment problem into three steps: selection of diverse shapes to describe the database shape-space; overlay of the database conformers to the diverse shapes; and non-optimized overlay of query and database conformers using common reference shapes. The precomputation, required by the first two steps, is a significant cost of the method; however, once performed, querying is two orders of magnitude faster. Extensions and variations of this methodology, for example, to handle more flexible and larger small-molecules are discussed.

Deformation by examples: a density flow approach

AbstractIn this article, a shape transformation technique is introduced for deforming objects based on a given deformation example. The example consists of two reference shapes representing two different states of an object. The reference shapes are assumed to morph from one state to the other. The evolution between the two reference shapes determines the shape transformation function. Any given objects can then be deformed by the same transformation. A continuous 4D Radial Basis Function is used to construct a density flow field (an extension of the optical flow in computer vision) representing the shape transformation of the example in 3‐space. Objects embedded in the density flow field are deformed by moving vertices of the objects along the density flow vectors. Additional parameters are introduced to control the process of the deformation. This provides explicit control on the shape of the object obtained in the deformation process. Copyright © 2007 John Wiley &amp; Sons, Ltd.

A unified particle model for fluid–solid interactions

AbstractWe present a new method for the simulation of melting and solidification in a unified particle model. Our technique uses the Smoothed Particle Hydrodynamics (SPH) method for the simulation of liquids, deformable as well as rigid objects, which eliminates the need to define an interface for coupling different models. Using this approach, it is possible to simulate fluids and solids by only changing the attribute values of the underlying particles. We significantly changed a prior elastic particle model to achieve a flexible model for melting and solidification. By using an SPH approach and considering a new definition of a local reference shape, the simulation of merging and splitting of different objects, as may be caused by phase change processes, is made possible. In order to keep the system stable even in regions represented by a sparse set of particles we use a special kernel function for solidification processes. Additionally, we propose a surface reconstruction technique based on considering the movement of the center of mass to reduce rendering errors in concave regions. The results demonstrate new interaction effects concerning the melting and solidification of material, even while being surrounded by liquids. Copyright © 2007 John Wiley &amp; Sons, Ltd.

A visual landmark framework for mobile robot navigation

This article describes visual functions dedicated to the extraction and recognition of visual landmarks, here planar quadrangles detected by a single camera. Landmarks are extracted among edge segments through a relaxation scheme, used to apply geometrical, topological and appearance constraints on sets of segments. Once extracted, such a landmark is characterized by invariant attributes so that recognition is made possible from a large range of viewpoints. Landmarks are represented by an icon which is built using the homography between the current viewpoint and a reference shape (a square). When detected again, the landmark is recognized by using a distance between icons. We propose a comparison of several of these metrics and an evaluation on actual and synthetic images that shows the validity of our approach. Results issued from experiments of a mobile robot navigating in an indoor environment are finally presented.

Affine-invariant geometric shape priors for region-based active contours

We present a new way of constraining the evolution of a region-based active contour with respect to a reference shape. Minimizing a shape prior, defined as a distance between shape descriptors based on the Legendre moments of the characteristic function, leads to a geometric flow that can be used with benefits in a two-class segmentation application. The shape model includes intrinsic invariance with regard to pose and affine deformations.

난류열전달 증진을 위한 딤플형상의 최적설계

This study presents a numerical procedure to optimize the shape of dimple surface to enhance turbulent heat transfer in a rectangular channel. The response surface based optimization method is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer with shear stress transport (SST) turbulence model. The dimple depth-to-dimple print diameter ratio, channel height-to-dimple print diameter ratio, and dimple print diameter-to-pitch ratio are chosen as design variables. The objective function is defined as a linear combination of heat transfer related term and friction loss related term with a weighting factor. Full factorial method is used to determine the training points as a mean of design of experiment. The optimum shape shows remarkable performance in comparison with a reference shape.

단단 천음속 축류압축기 동익의 Stacking Line 설계 최적화

Shape optimization of a rotor blade in a single-stage transonic axial compressor has been performed using a response surface method and three-dimensional Navier-Stokes analysis. Two shape variables of the rotor blade, which are used to define a blade skew, are introduced to increase an adiabatic efficiency. Throughout the shape optimization of a rotor blade, the adiabatic efficiency is increased to about 2.2 percent compared to that of the reference shape of the stator. The increase in efficiency for the optimal shape of the rotor is due to the pressure enhancement, which is mainly caused by moving the separation position on the suction surface of rotor blade to the downstream direction.

Commerical reference shape standards use in the study of particle shape effect on laser diffraction particle size analysis

The purpose of this paper is to describe the use of LGC Promochem AEA 1001 to AEA 1003 monosized fiber-analog shape standards in the study of the effect of particle shape on laser diffraction (LD) particle size analysis (psa). The psa of the AEA standards was conducted using LD psa systems from Beckman Coulter, Horiba, and Malvern Instruments. Flow speed settings, sample refractive index values, and sample cell types were varied to examine the extent to which the shape effect on LD psa results is modified by these variables. The volume and number probability plots resulting from these measurements were each characterized by a spread in the particle size distribution that roughly extended from the breadth to the longest dimension of the particles. For most of the selected sample refractive index values, the volume probability plots were characterized by apparent bimodal distributions. The results, therefore, provide experimental verification of the conclusions from theoretical studies of LD psa system response to monosized elliptical particles in which this apparent bimodality was the predicted result in the case of flow-oriented particles. The data support the findings from previous studies conducted over the past 10 years that have called into question the verity of the tenets of, and therefore the value of the application of, the equivalent spherical volume diameter theory and the random particle orientation model to the interpretation of LD psa results from measurements made on nonspherical particles.

A reduced basis element method for the steady Stokes problem

The reduced basis element method is a new approach for approximating the solution of problems described by partial differential equations. The method takes its roots in domain decomposi- tion methods and reduced basis discretizations. The basic idea is to first decompose the computational domain into a series of subdomains that are deformations of a few reference domains (or generic com- putational parts). Associated with each reference domain are precomputed solutions corresponding to the same governing partial differential equation, but solved for different choices of deformations of the reference subdomains and mapped onto the reference shape. The approximation corresponding to a new shape is then taken to be a linear combination of the precomputed solutions, mapped from the generic computational part to the actual computational part. We extend earlier work in this direction to solve incompressible fluid flow problems governed by the steady Stokes equations. Particular focus is given to satisfying the inf-sup condition, to a posteriori error estimation, and to gluing the local solutions together in the multidomain case.

Cutting path generation of linear hotwire cutter for VLM-ST

Most rapid prototyping (RP) processes adopt a solid CAD model, which will be sliced into thin layers of constant thickness in the building direction. Each cross-sectional layer is successively deposited and, simultaneously, bonded onto the previous layer; eventually, the stacked layers form a physical part of the model. A new thick-layered RP process, the transfer-type variable lamination manufacturing process using expandable polystyrene foam sheets (VLM-ST), has been developed to reduce building time by employing thick layers and to improve the surface finish of parts with a sloping surface. This paper describes the method to generate the unit shape layer (USL), the cutting path data of the four-axis hotwire cutter for the VLM-ST process. The USL is the basic unit of cutting and building in the VLM-ST process and it is also the basic unit of cutting path data of each layer. The USL includes data such as layer thickness, positional coordinates, side angles of each layer, and reference shape. The method to generate the USL is as follows: (1) the mid-slice of each layer is generated from the CAD model, (2) each mid-slice is converted into a simply-connected domain, (3) the rotation angle of the hotwire of the cutting system is calculated for each layer, and (4) the reference shape of each layer is generated for manual stacking. The procedure to generate the cutting path data of the linear hotwire cutter for VLM-ST was practically applied and verified for various three-dimensional shapes.

Virtual reconstruction: a primer in computer-assisted paleontology and biomedicine

Preface. Acknowledgments. Introduction. 1. Virtual Reconstruction. 1.1 A Virtual Reality Contest. 1.2 Virtual Reconstruction. 1.3 Computer-Assisted Paleontology. 1.3.1 Data Acquisition. 1.3.2 Data Segmentation and Three-Dimensional Reconstruction. 1.3.3 Virtual Fossil Reconstruction. 1.3.4 From Virtual Reality to Real Virtuality. 1.3.5 Databases and Morphometry. 1.3.6 Virtual Reconstruction in Space and Time. 1.4 Computer-Assisted Surgery. 1.5 Further Reading. 2. Data Representation. 2.1 World Food on a Chessboard. 2.2 Facts About Data to Get Data About Facts. 2.2.1 Analog and Digital Data. 2.2.2 Bits, Bytes, and Words. 2.2.3 Characters, Numbers, Pixels, and Voxels. 2.2.4 Representing Gray Tones and Colors. 2.2.5 Data Compression. 2.2.6 Some Common Image File Formats. 2.2.7 Implicit Versus Explicit Representation of Object Data. 2.2.8 Modeling Three-Dimensional Objects. 2.3 A Taxonomy of Biomedical Data. 2.3.1 Perspectives on Data. 2.3.2 Volume Data. 2.3.3 Surface Data. 2.3.4 Landmark Data. 2.3.5 Extent-Based Data. 2.3.6 Relational Data. 2.4 Further Reading. 3. Data Acquisition. 3.1 Data and the Physical World. 3.2 Vision and Photography as Data Acquisition: Performance Considerations. 3.3 Computed Tomography. 3.3.1 Frau RAntgena s Wedding Ring. 3.3.2 Radiographic Projections. 3.3.3 Reconstructing CT Images. 3.3.4 CT Scanning: Technical Considerations. 3.3.5 Limitations of CT Data Acquisition. 3.3.6 Slice-to-Slice, Helical, and Multislice CT. 3.3.7 Industrial and Micro Computed Tomography. 3.3.8 Three-Dimensional Data Acquisition with a Medical Scanner. 3.4 Magnetic Resonance Imaging. 3.5 Surface Scanners. 3.6 3D Digitizers. 3.7 Further Reading. 4. Image Data Processing. 4.1 Recovering Objects from Images. 4.2 Converting a CT Image into a Screen Image. 4.3 Filtering Images. 4.3.1 Coffee and Kernels. 4.3.2 Convolution and Fourier Analysis. 4.3.3 Statistical Filters. 4.3.4 Edge Detection Filters. 4.4 Extracting Isosurfaces. 4.4.1 Determining Boundaries in CT Images. 4.4.2 From Edges to Isocontours and Isosurfaces. 4.5 Interactive Segmentation. 4.6 Further Reading. 5. Visualization and Interaction. 5.1 Visualizing Data in Two and More Dimensions. 5.2 Interaction with Virtual Worlds. 5.3 The Graphics Rendering Pipeline. 5.4 Setting Up a Virtual Environment. 5.4.1 Object Materials, Lighting, and Shading. 5.4.2 Setting Up the Camera. 5.4.3 Object Manipulation and Interaction. 5.5 Volume Rendering. 5.6 Further Reading. 6. Virtual Fossil Reconstruction. 6.1 A Baroque Puzzle. 6.2 Principles of Reconstruction. 6.3 Physical and Virtual Reconstruction. 6.4 Preparing and Restoring Fossils on the Computer Screen. 6.5 Reconstructing Fossil Morphologies. 6.5.1 Recovering Implicit Anatomic Information. 6.5.2 Combining Computer Graphics and Anatomy: The Globe Paradigm. 6.5.3 Inferring Missing Information. 6.5.4 Interpolation and Extrapolation. 6.6 Correcting Fossil Deformation. 6.6.1 Taphonomic Scenarios. 6.6.2 Correcting Plastic Deformation. 6.7 Validating Virtual Reconstructions. 6.8 Paleodiagnostics and Paleoforensics. 6.9 Inferring Soft Tissue Structures. 6.9.1 Motivation. 6.9.2 Fossil Soft Tissue Reconstruction: Classic and Virtual Approaches. 6.9.3 What Shall Be Reconstructed? 6.9.4 Soft Tissue Reconstruction and Measurement. 6.10 Virtual Surgery: A Paleoanthropologista s Eye View. 6.10.1 Motivation. 6.10.2 Virtual Planning and Simulation of Surgical Interventions. 6.10.3 Custom Implant Design. 6.10.4 Soft Tissue Reconstruction. 6.11 Further Reading. 7. From Virtual Reality to Real Virtuality. 7.1 Reifying Virtual Objects. 7.2 Principles of Rapid Prototyping. 7.3 Combining Virtual Reality and Real Virtuality. 7.4 Further Reading. 8. Morphometric Analysis. 8.1 Morphometry as Reconstruction. 8.2 Morphometry and Geometry. 8.2.1 The Role of Geometry. 8.2.2 The Role of Size and Shape. 8.2.3 Multivariate Morphometry. 8.2.4 Principal Components Analysis and Dimension Reduction. 8.2.5 Classic Multivariate Morphometry: Geometry Lost. 8.2.6 Geometric Morphometrics: Geometry Recovered. 8.3 Shape Space Analysis. 8.3.1 From Da Arcy Thompson to Kendall. 8.3.2 The Workflow of Shape Space Analysis. 8.3.3 Determining a Reference Shape. 8.3.4 Analyzing Data in Shape Space. 8.3.5 Visualizing Patterns of Shape Difference and Shape Change. 8.3.5 Visualizing Patterns of Shape Difference and Shape Change. 8.4 Euclidean Distance Matrix Analysis. 8.4.1 In Search of the Golden Mean. 8.4.2 Exploring Form Variability with EDMA. 8.5 Outline Analysis. 8.6 A Comparison of Geometric Morphometric Methods. 8.6.1 Criteria for Comparison. 8.6.2 From Pattern to Process. 8.7 Exploring Morphometric Patterns. 8.8 Further Reading. Appendix A. Image Data Acquisition Systems: Performance Considerations. Appendix B. Parameters Influencing the Quality of CT Image Data. Appendix C. CT Scanning of Fossil Specimens and Recent Skeletal Specimens: How to Proceed? Appendix D. Object Manipulation in Virtual Space. Appendix E. A Parsimonious Approach to Correction of Taphonomic Deformation. Appendix F. Morphometry. References. Index.

Optimization of a stator blade using response surface method in a single-stage transonic axial compressor

This article describes the shape optimization of a stator blade in a single-stage transonic axial compressor. The blade optimization has been performed using response surface method and three-dimensional Navier-Stokes analysis. Thin-layer approximation is introduced to the Navier-Stokes equations, and an explicit Runge-Kutta scheme is used to solve the governing equations. Two geometric design variables of the stator blade, which are used to define a stacking line, are introduced to increase an adiabatic efficiency. D-optimal design is employed to reduce the number of evaluation points for response surface. With the optimization of the stator blade, the adiabatic efficiency is successfully improved when compared with that of the reference shape of the stator with straight stacking line. Positive stacking line, which bends on blade pressure side, effectively suppresses the flow separation on the blade suction surface of the stator.

WE‐C‐T‐617‐10: Geometry Calibration of An On‐Board KV Imaging System

Purpose: We have developed a method of geometrically calibrating the MV and kV radiographic isocenters of a Varian linear accelerator equipped with an on‐board kV imaging system. Method and Materials: The calibration uses a cylindrical phantom containing 16 BB's placed in a spiral pattern and ∼400–600 radiographs of the phantom acquired using both kV and MV imaging systems. Since the phantom has a known geometry, the 7 degrees of freedom (DOF) needed to fit the predicted projections of the BB's to the measured projections can be calculated. During MV imaging a partial transmission plate is placed in the accelerator wedge slot to project a reference shape onto the EPID images of the phantom. The reference shape accounts for motion of the EPID and generates the radiographic isocenter for the MV x‐ray beam alone. Geometry correction parameters can be calculated for the kV imaging system that map the center of radiographic images or CBCT projections to the radiographic isocenter of the MV beam. The method has been tested with linear accelerator and lab bench imaging systems. Results: BB identification accuracy is ∼0.3 pixels and is limited by noise in the images. While the method is insensitive to changes in SID (0.3 pixels ∼= 2.5 cm SID change), the method can measure known in‐plane imager displacements to an accuracy of better than 0.1 mm. Imager displacements versus gantry angle are small − 0.75×0.50 mm. CBCT reconstruction using parameters from this method results in spatial frequencies as high as 18 lp/cm and adjustments in parameters of ±0.1 mm reduce the reconstructed spatial resolution. Conclusion: Our method to match MV and kV radiographic isocenters for on‐board imaging systems shows that accelerator flex is quite modest but that the calibration method can improve the spatial resolution of the CBCT reconstructions.

단단 천음속 축류압축기의 정익형상 최적설계

This paper describes the shape optimization of a stator blade in a single-stage transonic axial compressor. The blade optimization has been performed using a response surface method and three-dimensional Navier-Stokes analysis. Two shape variables of the stator blade, which are used to define a stacking line, are introduced to increase an adiabatic efficiency. Data points for response evaluations have been selected by D-optimal design, and linear programming method has been used for an optimization on a response surface. Throughout the shape optimization of a stator blade, the adiabatic efficiency is increased to 5.8 percent compared to that of the reference shape of the stator. The increase of the efficiency is mainly caused by the pressure enhancement in the stator blade. Flow separation on the blade suction surface of the stator is also improved by optimizing the stator blade. It is noted that the optimization of the stator blade is also useful method to increase the adiabatic efficiency in the axial compressor as well as the optimization of a rotor blade, which is widely used now.

The Rich Stereochemistry of Eight‐Vertex Polyhedra: A Continuous Shape Measures Study

A stereochemical study of polyhedral eight-vertex structures is presented, based on continuous shape measures (CShM). Reference polyhedra, shape maps, and minimal-distortion interconversion paths are presented for eight-vertex polyhedral and polygonal structures within the CShM framework. The application of these stereochemical tools is analyzed for several families of experimental structures: 1) coordination polyhedra of molecular transition-metal coordination compounds, classified by electron configuration and ligands; 2) edge-bonded polyhedra, including cubane structures, realgar, and metal clusters; 3) octanuclear transition-metal supramolecular architectures; and 4) coordination polyhedra in extended structures in inorganic solids. Structural classification is shown to be greatly facilitated by these tools, and the detection of less common structures, such as the gyrobifastigium, is straightforward.

Development and Evaluation of a New Body-Seat Interface Shape Measurement System

A new system has been developed to capture the body-seat interface shape. It can repeatedly and accurately measure interface deformation. The shape sensing array system uses optical fiber technology and is noninvasive. The system can cover an interface as large as 400 x 480 mm and the shape is measured over a 10 x 12 array of sensors laminated on ribbon substrates. The accuracy and repeatability of this system were assessed. Measurement errors were evaluated by comparing the shape with a reference shape obtained by a mechanical digitizer. The root-mean-square error in the Z direction for the system was 3.79 mm. The repeatability of the system was within 0.38 mm under controlled conditions. Different interface materials noticeably affected measurements. With the development of this interface shape measurement device, the basic information gathered through its use may prove to be fundamental in the successful design of generic-shape contoured support surfaces. Furthermore, we expect that the new shape measurement device will provide a quick and effective tool for cushion evaluation and clinical guidelines for cushion prescription.

Helmholtz energy, extended corresponding states and local composition model for fluid mixtures

We present a model for the calculation of mixture properties. This model is based on the mixture residual Helmholtz energy given by the sum of two terms: one is the residual Helmholtz energy calculated by an extended corresponding states (ECS) model while the other is a correction term. The ECS model is based on methane as the reference fluid and shape factors that carry out the scaling of properties between the fluid of interest and the reference fluid. These shape factors are given by correlations in terms of reduced temperature and density. The application to mixtures is carried out with the one-fluid van der Waals mixture model. The correction term is temperature- and density-dependent as is given by a local composition mixing rule. Local compositions were calculated from a coordination number model based on lattice gas theory. With respect to binary-mixture properties, densities were calculated with an average absolute deviation (AAD) of 0.12%; speeds of sound were calculated with an AAD of 0.16% and bubble pressures were calculated with an AAD of 1.77%. Also, natural gas densities were calculated with AAD of 0.03% and natural gas speeds of sound were calculated with AAD of 0.049%. All these results are very satisfactory when compared with those obtained by modern mixture models.