Water flow based geometric active deformable model for road network
Leninisha, Shanmugam; Vani, Kaliaperumal
2015-04-01
A width and color based geometric active deformable model is proposed for road network extraction from remote sensing images with minimal human interception. Orientation and width of road are computed from a single manual seed point, from which the propagation starts both right and left hand directions of the starting point, which extracts the interconnected road network from the aerial or high spatial resolution satellite image automatically. Here the propagation (like water flow in canal with defined boundary) is restricted with color and width of the road. Road extraction is done for linear, curvilinear (U shape and S shape) roads first, irrespective of width and color. Then, this algorithm is improved to extract road with junctions in a shape of L, T and X along with center line. Roads with small break or disconnected roads are also extracts by a modified version of this same algorithm. This methodology is tested and evaluated with various remote sensing images. The experimental results show that the proposed method is efficient and extracting roads accurately with less computation time. However, in complex urban areas, the identification accuracy declines due to the various sizes of obstacles, over bridges, multilane etc.
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
There are two kinds of methods in researching the crust deformation: geophysical method and geometrical (or observational) method. Considerable differences usually exist between the two kinds of results, because of the datum differences, geophysical model errors, observational model errors, and so on. Thus, it is reasonable to combine the two kinds of information to collect the crust deformation information. To use the reliable geometrical and geophysical information, we have to control the observational and geophysical model error influences on the estimated deformation parameters, and to balance their contributions to the evaluated parameters. A hybrid estimation strategy is proposed here for evaluating the deformation parameters employing an adaptively robust filtering. The effects of measurement outliers on the estimated parameters are controlled by robust equivalent weights. Adaptive factors are introduced to balance the contribution of the geophysical model information and the geometrical measurements to the model parameters. The datum for the local deformation analysis is mainly determined by the highly accurate IGS station velocities. The hybrid estimation strategy is applied in an actual GPS monitoring network. It is shown that the hybrid technique employs locally repeated geometrical displacements to reduce the displacement errors caused by the mis-modeling of geophysical technique, and thus improves the precision of the estimated crust deformation parameters.
Philippon, Mélody; Le Carlier de Veslud, Christian; Gueydan, Frédéric; Brun, Jean-Pierre; Caumon, Guillaume
2015-09-01
Superposed to ductile syn-metamorphic deformations, post-foliation deformations affect metamorphic units during their exhumation. Understanding the role of such deformations in the structuration of metamorphic units is key for understanding the tectonic evolution of convergence zones. We characterize post-foliations deformations using 3D modelling which is a first-order tool to describe complex geological structures, but a challenging task where based only on surface data. We propose a modelling procedure that combines fast draft models (interpolation of orientation data), with more complex ones where the structural context is better understood (implicit modelling), allowing us to build a 3D geometrical model of Syros Island blueschists (Cyclades), based on field data. With our approach, the 3D model is able to capture the complex present-day geometry of the island, mainly controlled by the superposition of three types of post-metamorphic deformations affecting the original metamorphic pile: i) a top-to-South ramp-flat extensional system that dominates the overall island structure, ii) large-scale folding of the metamorphic units associated with ramp-flat extensional system, and iii) steeply-dipping normal faults trending dominantly NNW-SSE and EW. The 3D surfaces produced by this method match outcrop data, are geologically consistent, and provide reasonable estimates of geological structures in poorly constrained areas.
Institute of Scientific and Technical Information of China (English)
Wei LIU; Zhenyuan JIA; Fuji WANG; Yongshun ZHANG; Dongming GUO
2008-01-01
The geometrical nonlinearity of a giant magne-tostrictive thin film (GMF) can be clearly detected under the magnetostriction effect. Thus, using geometrical linear elastic theory to describe the strain, stress, and constitutive relationship of GMF is inaccurate. According to nonlinear elastic theory, a nonlinear deformation model of the bimorph GMF is established based on assumptions that the magnetostriction effect is equivalent to the effect of body force loaded on the GMF. With Taylor series method, the numerical solution is deduced. Experiments on TbDyFe/Polyimide (PI)/SmFe and TbDyFe/Cu/SmFe are then conducted to verify the proposed model, respectively. Results indicate that the nonlinear deflection curve model is in good conformity with the experimental data.
Zhang, Yongjie; Jing, Yiming; Liang, Xinghua; Xu, Guoliang; Dong, Lei
2012-09-01
A greyscale-based fully automatic deformable image registration algorithm, based on an optical flow method together with geometric smoothing, is developed for dynamic lung modeling and tumor tracking. In our computational processing pipeline, the input data is a set of 4D CT images with 10 phases. The triangle mesh of the lung model is directly extracted from the more stable exhale phase (Phase 5). In addition, we represent the lung surface model in 3D volumetric format by applying a signed distance function and then generate tetrahedral meshes. Our registration algorithm works for both triangle and tetrahedral meshes. In CT images, the intensity value reflects the local tissue density. For each grid point, we calculate the displacement from the static image (phase 5) to match with the moving image (other phases) by using merely intensity values of the CT images. The optical flow computation is followed by a regularization of the deformation field using geometric smoothing. Lung volume change and the maximum lung tissue movement are used to evaluate the accuracy of the application. Our testing results suggest that the application of deformable registration algorithm is an effective way for delineating and tracking tumor motion in image-guided radiotherapy.
Metastable vacua and geometric deformations
Amariti, A; Girardello, L; Mariotti, A
2008-01-01
We study the geometric interpretation of metastable vacua for systems of D3 branes at non isolated toric deformable singularities. Using the L^{aba} examples, we investigate the relations between the field theoretic susy breaking and restoration and the complex deformations of the CY singularities.
Geometric deformable model driven by CoCRFs: application to optical coherence tomography.
Tsechpenakis, Gabriel; Lujan, Brandon; Martinez, Oscar; Gregori, Giovanni; Rosenfeld, Philip J
2008-01-01
We present a geometric deformable model driven by dynamically updated probability fields. The shape is defined with the signed distance function, and the internal (smoothness) energy consists of a C1 continuity constraint, a shape prior, and a term that forces the zero-level of the shape distance function towards a connected form. The image probability fields are estimated by our collaborative Conditional Random Field (CoCRF), which is updated during the evolution in an active learning manner: it infers class posteriors in pixels or regions with feature ambiguities by assessing the joint appearance of neighboring sites and using the classification confidence. We apply our method to Optical Coherence Tomography fundus images for the segmentation of geographic atrophies in dry age-related macular degeneration of the human eye.
Application of Geometric Moiré to the Analysis of Large Deformation in Three-dimensional Models
Cicinelli, V.; Pappalettere, C.; Sun, W. M.; Surace, L.
The application of geometric moiré in large deformation of 3-D models is discussed. Different aspects of the method, such as mismatch technique and mechanical differentiation, are taken into consideration for the measurement. An application of the method is given to the cushion disk of an artificial knee joint in whose axis-symmetric cross section a cross specimen grating of 0.5mm pitch was replicated. The analysis shows the applicability of the geometric moiré, together with its various approaches, in the large deformation measurement giving the whole field quantitative definition.
Deformable image registration with geometric changes
Institute of Scientific and Technical Information of China (English)
Yu LIU; Bo ZHU
2015-01-01
Geometric changes present a number of difficulties in deformable image registration. In this paper, we propose a global deformation framework to model geometric changes whilst promoting a smooth transformation between source and target images. To achieve this, we have developed an innovative model which significantly reduces the side effects of geometric changes in image registration, and thus improves the registration accuracy. Our key contribution is the introduction of a sparsity-inducing norm, which is typically L1 norm regularization targeting regions where geometric changes occur. This preserves the smoothness of global transformation by eliminating local transformation under different conditions. Numerical solutions are discussed and analyzed to guarantee the stability and fast convergence of our algorithm. To demonstrate the effectiveness and utility of this method, we evaluate it on both synthetic data and real data from traumatic brain injury (TBI). We show that the transformation estimated from our model is able to reconstruct the target image with lower instances of error than a standard elastic registration model.
Geometric Total Variation for Texture Deformation
DEFF Research Database (Denmark)
Bespalov, Dmitriy; Dahl, Anders Lindbjerg; Shokoufandeh, Ali
2010-01-01
of features in texture images leads to significant improvements in localization of these features, when textures undergo geometrical transformations. Accurate localization of features in the presense of unkown deformations is a crucial property for texture characterization methods, and we intend to expoit...
The Minimal Geometric Deformation Approach Extended
Casadio, Roberto; da Rocha, Roldao
2015-01-01
The minimal geometric deformation approach was introduced in order to study the exterior space-time around spherically symmetric self-gravitating systems, like stars or similar astrophysical objects as well, in the Randall-Sundrum brane-world framework. A consistent extension of this approach is developed here, which contains modifications of both the time component and the radial component of a spherically symmetric metric. A modified Schwarzschild geometry is obtained as an example of its simplest application.
The minimal geometric deformation approach extended
Casadio, R.; Ovalle, J.; da Rocha, Roldão
2015-11-01
The minimal geometric deformation approach was introduced in order to study the exterior spacetime around spherically symmetric self-gravitating systems, such as stars or similar astrophysical objects, in the Randall-Sundrum brane-world framework. A consistent extension of this approach is developed here, which contains modifications of both the time component and the radial component of a spherically symmetric metric. A modified Schwarzschild geometry is obtained as an example of its simplest application, and a new solution that is potentially useful to describe stars in the brane-world is also presented.
Geometric Deformations Based on 3D Volume Morphing
Institute of Scientific and Technical Information of China (English)
JIN Xiaogang; WAN Huagen; PENG Qunsheng
2001-01-01
This paper presents a new geometric deformation method based on 3D volume morphing by using a new concept called directional polar coordinate. The user specifies the source control object and the destination control object which act as the embedded spaces.The source and the destination control objects determine a 3D volume morphing which maps the space enclosed in the source control object to that of the destination control object. By embedding the object to be deformed into the source control object, the 3D volume morphing determines the deformed object automatically without the tiring moving of control points.Experiments show that this deformation model is efficient and intuitive, and it can achieve some deformation effects which are difficult to achieve for traditional methods.
Lu, Hongyu
2012-01-01
The image force in active contours plays a key role for shape recovery in medical image analysis. The image force constructed from the heat diffusion model can not indicate segment the image accurately through it exhibits a uniform distribution of force field around the object. The features of the image force based on electrostatic field model are opposite. Firstly, this study introduces a fusion scheme of these two image forces, which capable of extracting the object boundary with high precision and fast speed. Till now, there is no satisfied analysis of the relationship between Snakes and Geometric Active Contour. The second contribution of this study indicates that the GAC model can be deduced directly from Snakes models. It proves that the each term in GAC and Snakes is correspondent and has the same function. These two models are only expressed using different mathematics.
Pragmatic geometric model evaluation
Pamer, Robert
2015-04-01
Quantification of subsurface model reliability is mathematically and technically demanding as there are many different sources of uncertainty and some of the factors can be assessed merely in a subjective way. For many practical applications in industry or risk assessment (e. g. geothermal drilling) a quantitative estimation of possible geometric variations in depth unit is preferred over relative numbers because of cost calculations for different scenarios. The talk gives an overview of several factors that affect the geometry of structural subsurface models that are based upon typical geological survey organization (GSO) data like geological maps, borehole data and conceptually driven construction of subsurface elements (e. g. fault network). Within the context of the trans-European project "GeoMol" uncertainty analysis has to be very pragmatic also because of different data rights, data policies and modelling software between the project partners. In a case study a two-step evaluation methodology for geometric subsurface model uncertainty is being developed. In a first step several models of the same volume of interest have been calculated by omitting successively more and more input data types (seismic constraints, fault network, outcrop data). The positions of the various horizon surfaces are then compared. The procedure is equivalent to comparing data of various levels of detail and therefore structural complexity. This gives a measure of the structural significance of each data set in space and as a consequence areas of geometric complexity are identified. These areas are usually very data sensitive hence geometric variability in between individual data points in these areas is higher than in areas of low structural complexity. Instead of calculating a multitude of different models by varying some input data or parameters as it is done by Monte-Carlo-simulations, the aim of the second step of the evaluation procedure (which is part of the ongoing work) is to
Lin, Erica; Li, Yaning; Ortiz, Christine; Boyce, Mary C.
2014-12-01
Geometrically structured interfaces in nature possess enhanced, and often surprising, mechanical properties, and provide inspiration for materials design. This paper investigates the mechanics of deformation and failure mechanisms of suture interface designs through analytical models and experiments on 3D printed polymer physical prototypes. Suture waveforms with generalized trapezoidal geometries (trapezoidal, rectangular, anti-trapezoidal, and triangular) are studied and characterized by several important geometric parameters: the presence or absence of a bonded tip region, the tip angle, and the geometry. It is shown that a wide range (in some cases as great as an order of magnitude) in stiffness, strength, and toughness is achievable dependent on tip bonding, tip angle, and geometry. Suture interfaces with a bonded tip region exhibit a higher initial stiffness due to the greater load bearing by the skeletal teeth, a double peak in the stress-strain curve corresponding to the failure of the bonded tip and the failure of the slanted interface region or tooth, respectively, and an additional failure and toughening mechanism due to the failure of the bonded tip. Anti-trapezoidal geometries promote the greatest amplification of properties for suture interfaces with a bonded tip due the large tip interface area. The tip angle and geometry govern the stress distributions in the teeth and the ratio of normal to shear stresses in the interfacial layers, which together determine the failure mechanism of the interface and/or the teeth. Rectangular suture interfaces fail by simple shearing of the interfaces. Trapezoidal and triangular suture interfaces fail by a combination of shear and tensile normal stresses in the interface, leading to plastic deformation, cavitation events, and subsequent stretching of interface ligaments with mostly elastic deformation in the teeth. Anti-trapezoidal suture interfaces with small tip angles have high stress concentrations in the teeth
Iris-based medical analysis by geometric deformation features.
Ma, Lin; Zhang, D; Li, Naimin; Cai, Yan; Zuo, Wangmeng; Wang, Kuanguan
2013-01-01
Iris analysis studies the relationship between human health and changes in the anatomy of the iris. Apart from the fact that iris recognition focuses on modeling the overall structure of the iris, iris diagnosis emphasizes the detecting and analyzing of local variations in the characteristics of irises. This paper focuses on studying the geometrical structure changes in irises that are caused by gastrointestinal diseases, and on measuring the observable deformations in the geometrical structures of irises that are related to roundness, diameter and other geometric forms of the pupil and the collarette. Pupil and collarette based features are defined and extracted. A series of experiments are implemented on our experimental pathological iris database, including manual clustering of both normal and pathological iris images, manual classification by non-specialists, manual classification by individuals with a medical background, classification ability verification for the proposed features, and disease recognition by applying the proposed features. The results prove the effectiveness and clinical diagnostic significance of the proposed features and a reliable recognition performance for automatic disease diagnosis. Our research results offer a novel systematic perspective for iridology studies and promote the progress of both theoretical and practical work in iris diagnosis.
Ye, Chuyang; Yang, Zhen; Ying, Sarah H; Prince, Jerry L
2015-07-01
The cerebellar peduncles, comprising the superior cerebellar peduncles (SCPs), the middle cerebellar peduncle (MCP), and the inferior cerebellar peduncles (ICPs), are white matter tracts that connect the cerebellum to other parts of the central nervous system. Methods for automatic segmentation and quantification of the cerebellar peduncles are needed for objectively and efficiently studying their structure and function. Diffusion tensor imaging (DTI) provides key information to support this goal, but it remains challenging because the tensors change dramatically in the decussation of the SCPs (dSCP), the region where the SCPs cross. This paper presents an automatic method for segmenting the cerebellar peduncles, including the dSCP. The method uses volumetric segmentation concepts based on extracted DTI features. The dSCP and noncrossing portions of the peduncles are modeled as separate objects, and are initially classified using a random forest classifier together with the DTI features. To obtain geometrically correct results, a multi-object geometric deformable model is used to refine the random forest classification. The method was evaluated using a leave-one-out cross-validation on five control subjects and four patients with spinocerebellar ataxia type 6 (SCA6). It was then used to evaluate group differences in the peduncles in a population of 32 controls and 11 SCA6 patients. In the SCA6 group, we have observed significant decreases in the volumes of the dSCP and the ICPs and significant increases in the mean diffusivity in the noncrossing SCPs, the MCP, and the ICPs. These results are consistent with a degeneration of the cerebellar peduncles in SCA6 patients.
Deformed Spacetime Geometrizing Interactions in Four and Five Dimensions
Cardone, Fabio
2007-01-01
This volume provides a detailed discussion of the mathematical aspects and the physical applications of a new geometrical structure of space-time, based on a generalization ("deformation") of the usual Minkowski space, as supposed to be endowed with a metric whose coefficients depend on the energy. Such a formalism (Deformed Special Relativity, DSR) allows one to account for breakdown of local Lorentz invariance in the usual, special-relativistic meaning (however, Lorentz invariance is recovered in a generalized sense) to provide an effective geometrical description of the four fundamental interactions (electromagnetic, weak, strong and gravitational) Moreover, the four-dimensional energy-dependent space-time is just a manifestation of a larger, five-dimensional space in which energy plays the role of a fifth (non-compactified) dimension. This new five-dimensional scheme (Deformed Relativity in Five Dimensions, DR5) represents a true generalization of the usual Kaluza-Klein (KK) formalism. The mathematical pr...
Geometric correction of deformed chromosomes for automatic Karyotyping.
Khan, Shadab; DSouza, Alisha; Sanches, João; Ventura, Rodrigo
2012-01-01
Automatic Karyotyping is the process of classifying chromosomes from an unordered karyogram into their respective classes to create an ordered karyogram. Automatic karyotyping algorithms typically perform geometrical correction of deformed chromosomes for feature extraction; these features are used by classifier algorithms for classifying the chromosomes. Karyograms of bone marrow cells are known to have poor image quality. An example of such karyograms is the Lisbon-K(1) (LK(1)) dataset that is used in our work. Thus, to correct the geometrical deformation of chromosomes from LK(1), a robust method to obtain the medial axis of the chromosome was necessary. To address this problem, we developed an algorithm that uses the seed points to make a primary prediction. Subsequently, the algorithm computes the distance of boundary from the predicted point, and the gradients at algorithm-specified points on the boundary to compute two auxiliary predictions. Primary prediction is then corrected using auxiliary predictions, and a final prediction is obtained to be included in the seed region. A medial axis is obtained this way, which is further used for geometrical correction of the chromosomes. This algorithm was found capable of correcting geometrical deformations in even highly distorted chromosomes with forked ends.
Extending the geometric deformation: New black hole solutions
Ovalle, Jorge
2016-03-01
By using the extension of the Minimal Geometric Deformation approach, recently developed to investigate the exterior spacetime of a self-gravitating system in the Braneworld, we identified a master solution for the deformation undergone by the radial metric component when time deformations are produced by bulk gravitons. A specific form for the temporal deformation is used to generate a new exterior solution with a tidal charge Q. The main feature of this solution is the presence of higher-order terms in the tidal charge, thus generalizing the well known tidally charged solution. The horizon of the black hole lies inside the Schwarzschild radius, h < rs = 2ℳ, indicating that extra-dimensional effects weaken the gravitational field.
Extending the geometric deformation: New black hole solutions
Ovalle, J
2015-01-01
We use the extension of the Minimal Geometric Deformation approach, recently developed to investigate the exterior of a self-gravitating system in the Braneworld, to identified a master solution for the deformation undergone by the radial metric component when time deformations are produced by bulk gravitons. A specific form for the temporal deformation is used to generate a new exterior solution with a tidal charge $Q$. The main feature of this solution is the presence of higher-order terms in the tidal charge, thus generalizing the well known tidally charged solution. The horizon of the black hole lies inside the Schwarzschild radius, $h
Black hole acoustics in the minimal geometric deformation of a de Laval nozzle
Energy Technology Data Exchange (ETDEWEB)
Rocha, Roldao da [Universidade Federal do ABC-UFABC, Centro de Matematica, Computacao e Cognicao, Santo Andre (Brazil)
2017-05-15
The correspondence between sound waves, in a de Laval propelling nozzle, and quasinormal modes emitted by brane-world black holes deformed by a 5D bulk Weyl fluid are here explored and scrutinized. The analysis of sound waves patterns in a de Laval nozzle in the laboratory, reciprocally, is here shown to provide relevant data about the 5D bulk Weyl fluid and its on-brane projection, comprised by the minimal geometrically deformed compact stellar distribution on the brane. Acoustic perturbations of the gas fluid flow in the de Laval nozzle are proved to coincide with the quasinormal modes of black holes solutions deformed by the 5D Weyl fluid, in the geometric deformation procedure. Hence, in a phenomenological Eoetvoes-Friedmann fluid brane-world model, the realistic shape of a de Laval nozzle is derived and its consequences studied. (orig.)
Geometrically nonlinear creeping mathematic models of shells with variable thickness
Directory of Open Access Journals (Sweden)
V.M. Zhgoutov
2012-08-01
Full Text Available Calculations of strength, stability and vibration of shell structures play an important role in the design of modern devices machines and structures. However, the behavior of thin-walled structures of variable thickness during which geometric nonlinearity, lateral shifts, viscoelasticity (creep of the material, the variability of the profile take place and thermal deformation starts up is not studied enough.In this paper the mathematical deformation models of variable thickness shells (smoothly variable and ribbed shells, experiencing either mechanical load or permanent temperature field and taking into account the geometrical nonlinearity, creeping and transverse shear, were developed. The refined geometrical proportions for geometrically nonlinear and steadiness problems are given.
3D facial geometric features for constrained local model
Cheng, Shiyang; Zafeiriou, Stefanos; Asthana, Akshay; Pantic, Maja
2014-01-01
We propose a 3D Constrained Local Model framework for deformable face alignment in depth image. Our framework exploits the intrinsic 3D geometric information in depth data by utilizing robust histogram-based 3D geometric features that are based on normal vectors. In addition, we demonstrate the fusi
Geometric interpretation for the interacting-boson-fermion model
Energy Technology Data Exchange (ETDEWEB)
Leviatan, A.
1988-08-11
A geometric oriented approach for studying the interacting-boson-fermion model for odd-A nuclei is presented. A deformed single-particle hamiltonian is derived by means of an algebraic Born-Oppenheimer treatment. Observables concerning spectrum and transitions are calculated for the case of a single-j fermion coupled to a prolate core charge boson number and arbitrary deformations.
Diffeomorphic Statistical Deformation Models
DEFF Research Database (Denmark)
Hansen, Michael Sass; Hansen, Mads/Fogtman; Larsen, Rasmus
2007-01-01
In this paper we present a new method for constructing diffeomorphic statistical deformation models in arbitrary dimensional images with a nonlinear generative model and a linear parameter space. Our deformation model is a modified version of the diffeomorphic model introduced by Cootes et al. Th...... with ground truth in form of manual expert annotations, and compared to Cootes's model. We anticipate applications in unconstrained diffeomorphic synthesis of images, e.g. for tracking, segmentation, registration or classification purposes....
Geometric models of (d+1)-dimensional relativistic rotating oscillators
Cotaescu, I I
2000-01-01
Geometric models of quantum relativistic rotating oscillators in arbitrary dimensions are defined on backgrounds with deformed anti-de Sitter metrics. It is shown that these models are analytically solvable, deriving the formulas of the energy levels and corresponding normalized energy eigenfunctions. An important property is that all these models have the same nonrelativistic limit, namely the usual harmonic oscillator.
The Spherical Deformation Model
DEFF Research Database (Denmark)
Hobolth, Asgar
2003-01-01
Miller et al. (1994) describe a model for representing spatial objects with no obvious landmarks. Each object is represented by a global translation and a normal deformation of a sphere. The normal deformation is defined via the orthonormal spherical-harmonic basis. In this paper we analyse...... the spherical deformation model in detail and describe how it may be used to summarize the shape of star-shaped three-dimensional objects with few parameters. It is of interest to make statistical inference about the three-dimensional shape parameters from continuous observations of the surface and from...
Hubbard model with geometrical frustration
Energy Technology Data Exchange (ETDEWEB)
Lee, Hunpyo
2009-10-15
At first we present the details of the dual fermion (DF), the cluster extension of dynamical mean field theory (CDMFT) and continuous-time quantum Monte Carlo (CT QMC) methods. Using a panoply of these methods we explore the Hubbard model on the triangular and hyperkagome lattice. We find a first-order transition and continuous transition on the triangular and hyper-kagome lattice, respectively. Moreover, we find the reentrant behavior due to competition between the magnetic correlation and itinerancy of electrons by source of geometrical frustration on both lattices. (orig.)
Pallozzi Lavorante, Luca; Dirk Ebert, Hans
2008-07-01
Tensor3D is a geometric modeling program with the capacity to simulate and visualize in real-time the deformation, specified through a tensor matrix and applied to triangulated models representing geological bodies. 3D visualization allows the study of deformational processes that are traditionally conducted in 2D, such as simple and pure shears. Besides geometric objects that are immediately available in the program window, the program can read other models from disk, thus being able to import objects created with different open-source or proprietary programs. A strain ellipsoid and a bounding box are simultaneously shown and instantly deformed with the main object. The principal axes of strain are visualized as well to provide graphical information about the orientation of the tensor's normal components. The deformed models can also be saved, retrieved later and deformed again, in order to study different steps of progressive strain, or to make this data available to other programs. The shape of stress ellipsoids and the corresponding Mohr circles defined by any stress tensor can also be represented. The application was written using the Visualization ToolKit, a powerful scientific visualization library in the public domain. This development choice, allied to the use of the Tcl/Tk programming language, which is independent on the host computational platform, makes the program a useful tool for the study of geometric deformations directly in three dimensions in teaching as well as research activities.
Phenomenological modeling of Geometric Metasurfaces
Ye, Weimin; Xiang, Yuanjiang; Fan, Dianyuan; Zhang, Shuang
2015-01-01
Metasurfaces, with their superior capability in manipulating the optical wavefront at the subwavelength scale and low manufacturing complexity, have shown great potential for planar photonics and novel optical devices. However, vector field simulation of metasurfaces is so far limited to periodic-structured metasurfaces containing a small number of meta-atoms in the unit cell by using full-wave numerical methods. Here, we propose a general phenomenological method to analytically model metasurfaces made up of arbitrarily distributed meta-atoms based on the assumption that the meta-atoms possess localized resonances with Lorentz-Drude forms, whose exact form can be retrieved from the full wave simulation of a single element. Applied to phase modulated geometric metasurfaces, our analytical results show good agreement with full-wave numerical simulations. The proposed theory provides an efficient method to model and design optical devices based on metasurfaces.
Elastic scattering in geometrical model
Plebaniak, Zbigniew; Wibig, Tadeusz
2016-10-01
The experimental data on proton-proton elastic and inelastic scattering emerging from the measurements at the Large Hadron Collider, calls for an efficient model to fit the data. We have examined the optical, geometrical picture and we have found the simplest, linear dependence of this model parameters on the logarithm of the interaction energy with the significant change of the respective slopes at one point corresponding to the energy of about 300 GeV. The logarithmic dependence observed at high energies allows one to extrapolate the proton-proton elastic, total (and inelastic) cross sections to ultra high energies seen in cosmic rays events which makes a solid justification of the extrapolation to very high energy domain of cosmic rays and could help us to interpret the data from an astrophysical and a high energy physics point of view.
Compensation of geometrical deformations for watermark extraction in digital cinema application
Delannay, Damien; Delaigle, Jean-Francois; Macq, Benoit M. M.; Barlaud, Michel
2001-08-01
In this paper, we investigate the restoration of geometrically altered digital images with the aim of recovering an embedded watermark information. More precisely, we focus on the distorsion taking place by the camera acquisition of an image. Indeed, in the cinema industry, a large part of early movie piracy comes from copies made in the theater itself with a camera. The evolution towards digital cinema broadcast enables watermark based fingerprinting protection systems. The first step for fingerprint extraction of a counterfeit material is the compensation of the geometrical deformation inherent to the acquisition process. In order to compensate the deformations, we use a modified 12-parameters bilinear transformation model which closely matches the deformations taking place by an analog acquisition process. The estimation of the parameters can either be global, either vary across regions within the image. Our approach consist in the estimation of the displacement of a number of of pixels via a modified block-matching technique followed by a minimum mean square error optimization of the parameters on basis of those estimated displacement-vectors. The estimated transformation is applied to the candidate image to get a reconstruction as close as possible to the original image. Classical watermark extraction procedure can follow.
Geometric Deformations of Orthogonal and Symplectic Galois Representations
Booher, Jeremy
2016-01-01
For a representation over a finite field of characteristic p of the absolute Galois group of the rationals, we study the existence of a lift to characteristic zero that is geometric in the sense of the Fontaine-Mazur conjecture. For two-dimensional representations, Ramakrishna proved that under technical assumptions odd representations admit geometric lifts. We generalize this to higher dimensional orthogonal and symplectic representations. The key innovation is the definition and study of a ...
Geometrical approach to fluid models
Kuvshinov, B. N.; Schep, T. J.
1997-01-01
Differential geometry based upon the Cartan calculus of differential forms is applied to investigate invariant properties of equations that describe the motion of continuous media. The main feature of this approach is that physical quantities are treated as geometrical objects. The geometrical
Geometrical approach to fluid models
Kuvshinov, B. N.; Schep, T. J.
1997-01-01
Differential geometry based upon the Cartan calculus of differential forms is applied to investigate invariant properties of equations that describe the motion of continuous media. The main feature of this approach is that physical quantities are treated as geometrical objects. The geometrical notio
Black strings from minimal geometric deformation in a variable tension brane-world
Casadio, R.; Ovalle, J.; da Rocha, Roldão
2014-02-01
We study brane-world models with variable brane tension and compute corrections to the horizon of a black string along the extra dimension. The four-dimensional geometry of the black string on the brane is obtained by means of the minimal geometric deformation approach, and the bulk corrections are then encoded in additional terms involving the covariant derivatives of the variable brane tension. Our investigation shows that the variable brane tension strongly affects the shape and evolution of the black string horizon along the extra dimension, at least in a near-brane expansion. In particular, we apply our general analysis to a model motivated by the Eötvös branes, where the variable brane tension is related to the Friedmann-Robertson-Walker brane-world cosmology. We show that for some stages in the evolution of the universe, the black string warped horizon collapses to a point and the black string has correspondingly finite extent along the extra dimension. Furthermore, we show that in the minimal geometric deformation of a black hole on the variable tension brane, the black string has a throat along the extra dimension, whose area tends to zero as time goes to infinity.
Higher-Dimensional Geometric $\\sigma$-Models
Vasilic, M
1999-01-01
Geometric $\\sigma$-models have been defined as purely geometric theories of scalar fields coupled to gravity. By construction, these theories possess arbitrarily chosen vacuum solutions. Using this fact, one can build a Kaluza--Klein geometric $\\sigma$-model by specifying the vacuum metric of the form $M^4\\times B^d$. The obtained higher dimensional theory has vanishing cosmological constant but fails to give massless gauge fields after the dimensional reduction. In this paper, a modified geometric $\\sigma$-model is suggested, which solves the above problem.
Energy Technology Data Exchange (ETDEWEB)
Naei, Mohammad Hassan; Rastgoo, Abbas [University of Tehran, Tehran (Iran, Islamic Republic of); Ebrahimi, Farzad [Faculty of Engineering and Technology, lmam Khomeini International University, Qazvin (Iran, Islamic Republic of)
2009-08-15
A theoretical model for geometrically nonlinear vibration analysis of piezoelectrically actuated circular plates made of functionally grade material (FGM) is presented based on Kirchhoff's-Love hypothesis with von-Karman type geometrical large nonlinear deformations. To determine the initial stress state and pre-vibration deformations of the smart plate a nonlinear static problem is solved followed by adding an incremental dynamic state to the pre-vibration state. The derived governing equations of the structure are solved by exact series expansion method combined with perturbation approach. The material properties of the FGM core plate are assumed to be graded in the thickness direction according to the power-law distribution in terms of the volume fractions of the constituents. Control of the FGM plate's nonlinear deflections and natural frequencies using high control voltages is studied and their nonlinear effects are evaluated. Numerical results for FG plates with various mixture of ceramic and metal are presented in dimensionless forms. In a parametric study the emphasis is placed on investigating the effect of varying the applied actuator voltage as well as gradient index of FGM plate on vibration characteristics of the smart structure
Some technical issues in geometric modeling
Energy Technology Data Exchange (ETDEWEB)
Peterson, D.P.
1983-01-01
The full impact of CAD/CAM will not be felt until geometric modeling systems support dimensioning and tolerancing, have sophisticated user interfaces, and are capable of routinely handling many representation conversions. The attainment of these capabilities requires a joint effort among users, implementors, and theoreticians of geometric modeling.
Abelian and derived deformations in the presence of Z-generating geometric helices
De Deken, Olivier
2010-01-01
For a Grothendieck category C which, via a Z-generating sequence (O(n))_{n in Z}, is equivalent to the category of "quasi-coherent modules" over an associated Z-algebra A, we show that under suitable cohomological conditions "taking quasi-coherent modules" defines an equivalence between linear deformations of A and abelian deformations of C. If (O(n))_{n in Z} is at the same time a geometric helix in the derived category, we show that restricting a (deformed) Z-algebra to a "thread" of objects defines a further equivalence with linear deformations of the associated matrix algebra.
Brane-world stars from minimal geometric deformation, and black holes
Casadio, Roberto
2012-01-01
We build analytical models of spherically symmetric stars in the brane-world, in which the external space-time contains both an ADM mass and a tidal charge. In order to determine the interior geometry, we apply the principle of minimal geometric deformation, which allows one to map General Relativistic solutions to solutions of the effective four-dimensional brane-world equations. We further restrict our analysis to stars with a radius linearly related to the total General Relativistic mass, and obtain a general relation between the latter, the brane-world ADM mass and the tidal charge. In these models, the value of the star's radius can then be taken to zero smoothly, thus obtaining brane-world black hole metrics with a tidal charge solely determined by the mass of the source and the brane tension. General conclusions regarding the minimum mass for semiclassical black holes will also be drawn.
5th Dagstuhl Seminar on Geometric Modelling
Brunnett, Guido; Farin, Gerald; Goldman, Ron
2004-01-01
In 19 articles presented by leading experts in the field of geometric modelling the state-of-the-art on representing, modeling, and analyzing curves, surfaces as well as other 3-dimensional geometry is given. The range of applications include CAD/CAM-systems, computer graphics, scientific visualization, virtual reality, simulation and medical imaging. The content of this book is based on selected lectures given at a workshop held at IBFI Schloss Dagstuhl, Germany. Topics treated are: – curve and surface modelling – non-manifold modelling in CAD – multiresolution analysis of complex geometric models – surface reconstruction – variational design – computational geometry of curves and surfaces – 3D meshing – geometric modelling for scientific visualization – geometric models for biomedical applications
Rule-based transformations for geometric modelling
Directory of Open Access Journals (Sweden)
Thomas Bellet
2011-02-01
Full Text Available The context of this paper is the use of formal methods for topology-based geometric modelling. Topology-based geometric modelling deals with objects of various dimensions and shapes. Usually, objects are defined by a graph-based topological data structure and by an embedding that associates each topological element (vertex, edge, face, etc. with relevant data as their geometric shape (position, curve, surface, etc. or application dedicated data (e.g. molecule concentration level in a biological context. We propose to define topology-based geometric objects as labelled graphs. The arc labelling defines the topological structure of the object whose topological consistency is then ensured by labelling constraints. Nodes have as many labels as there are different data kinds in the embedding. Labelling constraints ensure then that the embedding is consistent with the topological structure. Thus, topology-based geometric objects constitute a particular subclass of a category of labelled graphs in which nodes have multiple labels.
Rule-based transformations for geometric modelling
Bellet, Thomas; Gall, Pascale Le; 10.4204/EPTCS.48.5
2011-01-01
The context of this paper is the use of formal methods for topology-based geometric modelling. Topology-based geometric modelling deals with objects of various dimensions and shapes. Usually, objects are defined by a graph-based topological data structure and by an embedding that associates each topological element (vertex, edge, face, etc.) with relevant data as their geometric shape (position, curve, surface, etc.) or application dedicated data (e.g. molecule concentration level in a biological context). We propose to define topology-based geometric objects as labelled graphs. The arc labelling defines the topological structure of the object whose topological consistency is then ensured by labelling constraints. Nodes have as many labels as there are different data kinds in the embedding. Labelling constraints ensure then that the embedding is consistent with the topological structure. Thus, topology-based geometric objects constitute a particular subclass of a category of labelled graphs in which nodes hav...
GEOMETRICAL NONLINEAR WAVES IN FINITE DEFORMATION ELASTIC RODS
Institute of Scientific and Technical Information of China (English)
GUO Jian-gang; ZHOU Li-jun; ZHANG Shan-yuan
2005-01-01
By using Hamilton-type variation principle in non-conservation system, the nonlinear equation of wave motion of a elastic thin rod was derived according to Lagrange description of finite deformation theory. The dissipation caused due to viscous effect and the dispersion introduced by transverse inertia were taken into consideration so that steady traveling wave solution can be obtained. Using multi-scale method the nonlinear equation is reduced to a KdV-Burgers equation which corresponds with saddle-spiral heteroclinic orbit on phase plane. Its solution is called the oscillating-solitary wave or saddle-spiral shock wave.If viscous effect or transverse inertia is neglected, the equation is degraded to classical KdV or Burgers equation. The former implies a propagating solitary wave with homoclinic on phase plane, the latter means shock wave and heteroclinic orbit.
Geometric sigma model of the Universe
Vasilić, Milovan
2017-05-01
The purpose of this work is to demonstrate how an arbitrarily chosen background of the Universe can be made a solution of a simple geometric sigma model. Geometric sigma models are purely geometric theories in which spacetime coordinates are seen as scalar fields coupled to gravity. Although they look like ordinary sigma models, they have the peculiarity that their complete matter content can be gauged away. The remaining geometric theory possesses a background solution that is predefined in the process of constructing the theory. The fact that background configuration is specified in advance is another peculiarity of geometric sigma models. In this paper, I construct geometric sigma models based on different background geometries of the Universe. Whatever background geometry is chosen, the dynamics of its small perturbations is shown to have a generic classical stability. This way, any freely chosen background metric is made a stable solution of a simple model. Three particular models of the Universe are considered as examples of how this is done in practice. Supported by Serbian Ministry of Education, Science and Technological Development (171031)
GEOMETRIC ANALYSIS OF PLANAR SHAPES WITH APPLICATIONS TO CELL DEFORMATIONS
Directory of Open Access Journals (Sweden)
Ximo Gual-Arnau
2015-09-01
Full Text Available Shape analysis is of great importance in many fields such as computer vision, medical imaging, and computational biology. In this paper we focus on a shape space in which shapes are represented by means of planar closed curves. In this shape space a new metric was recently introduced with the result that this shape space has the property of being isometric to an infinite-dimensional Grassmann manifold of 2-dimensional subspaces. Using this isometry it is possible, from Younes et al. (2008, to explicitly describe geodesics, a task that previously was not at all easy. Our aim is twofold, namely: to use this general theory in order to show some applications to the study of erythrocytes, using digital images of peripheral blood smears, in the treatment of sickle cell disease; and, since normal erythrocytes are almost circular and many Sickle cells have elliptical shape, to particularize the computation of geodesics and distances between shapes using this metric to planar objects considered as deformations of a template (circle or ellipse. The applications considered include: shape interpolation, shape classification, and shape clustering.
Making Deformable Template Models Operational
DEFF Research Database (Denmark)
Fisker, Rune
2000-01-01
Deformable template models are a very popular and powerful tool within the field of image processing and computer vision. This thesis treats this type of models extensively with special focus on handling their common difficulties, i.e. model parameter selection, initialization and optimization...... published during the Ph.D. project. To put these articles into the general context of deformable template models and to pass on an overview of the deformable template model literature, the thesis starts with a compact survey of the deformable template model literature with special focus on representation....... A proper handling of the common difficulties is essential for making the models operational by a non-expert user, which is a requirement for intensifying and commercializing the use of deformable template models. The thesis is organized as a collection of the most important articles, which has been...
Hierarchical Geometric Constraint Model for Parametric Feature Based Modeling
Institute of Scientific and Technical Information of China (English)
高曙明; 彭群生
1997-01-01
A new geometric constraint model is described,which is hierarchical and suitable for parametric feature based modeling.In this model,different levels of geometric information are repesented to support various stages of a design process.An efficient approach to parametric feature based modeling is also presented,adopting the high level geometric constraint model.The low level geometric model such as B-reps can be derived automatically from the hig level geometric constraint model,enabling designers to perform their task of detailed design.
Geometric Modelling by Recursively Cutting Vertices
Institute of Scientific and Technical Information of China (English)
吕伟; 梁友栋; 等
1989-01-01
In this paper,a new method for curve and surface modelling is introduced which generates curves and surfaces by recursively cutting and grinding polygons and polyhedra.It is a generalization of the existing corner-cutting methods.A lot of properties,such as geometric continuity,representation,shape-preserving,and the algorithm are studied which show that such curves and surfaces are suitable for geometric designs in CAD,computer graphics and their application fields.
Deng, Zhipeng; Lei, Lin; Zhou, Shilin
2015-10-01
Automatic image registration is a vital yet challenging task, particularly for non-rigid deformation images which are more complicated and common in remote sensing images, such as distorted UAV (unmanned aerial vehicle) images or scanning imaging images caused by flutter. Traditional non-rigid image registration methods are based on the correctly matched corresponding landmarks, which usually needs artificial markers. It is a rather challenging task to locate the accurate position of the points and get accurate homonymy point sets. In this paper, we proposed an automatic non-rigid image registration algorithm which mainly consists of three steps: To begin with, we introduce an automatic feature point extraction method based on non-linear scale space and uniform distribution strategy to extract the points which are uniform distributed along the edge of the image. Next, we propose a hybrid point matching algorithm using DaLI (Deformation and Light Invariant) descriptor and local affine invariant geometric constraint based on triangulation which is constructed by K-nearest neighbor algorithm. Based on the accurate homonymy point sets, the two images are registrated by the model of TPS (Thin Plate Spline). Our method is demonstrated by three deliberately designed experiments. The first two experiments are designed to evaluate the distribution of point set and the correctly matching rate on synthetic data and real data respectively. The last experiment is designed on the non-rigid deformation remote sensing images and the three experimental results demonstrate the accuracy, robustness, and efficiency of the proposed algorithm compared with other traditional methods.
Connexions for the nuclear geometrical collective model
Rosensteel, G.; Sparks, N.
2015-11-01
The Bohr-Mottelson-Frankfurt model of nuclear rotations and quadrupole vibrations is a foundational model in nuclear structure physics. The model, also called the geometrical collective model or simply GCM(3), has two hidden mathematical structures, one group theoretic and the other differential geometric. Although the group structure has been understood for some time, the geometric structure is a new feature that this paper investigates in some detail. Using the de Rham Laplacian \\triangle =\\star d \\star d for the kinetic energy extends significantly the physical scope of the GCM(3) model. This Laplacian contains a ‘magnetic’ term due to the connexion between base manifold rotational and fibre vortex degrees of freedom. When the connexion specializes to irrotational flow, the Laplacian reduces to the Bohr-Mottelson kinetic energy operator.
Geometric interpretation of Planck-scale-deformed co-products
Lobo, Iarley P
2016-01-01
For theories formulated with a maximally symmetric momentum space we propose a general characterization for the description of interactions in terms of the isometry group of the momentum space. The well known cases of $\\kappa$-Poincar\\'e-inspired and (2+1)-dimensional gravity-inspired composition laws both satisfy our condition. Future applications might include the proposal of a class of models based on momenta spaces with anti-de Sitter geometry.
Geometric Modeling Application Interface Program
1990-11-01
Manual IDEF-Extended ( IDEFIX ) Integrated Information Support System (IISS), ICAM Project 6201, Contract F33615-80-C-5155, December 1985. Interim...Differential Geometry of Curves and Surfaces, M. P. de Carmo, Prentice-Hall, Inc., 1976. IDEFIX Readers Reference, D. Appleton Company, December 1985...Modeling. IDEFI -- IDEF Information Modeling. IDEFIX -- IDEF Extended Information Modeling. IDEF2 -- IDEF Dynamics Modeling. IDSS -- Integrated Decision
Ko, William L.; Fleischer, Van Tran; Lung, Shun-Fat
2017-01-01
For shape predictions of structures under large geometrically nonlinear deformations, Curved Displacement Transfer Functions were formulated based on a curved displacement, traced by a material point from the undeformed position to deformed position. The embedded beam (depth-wise cross section of a structure along a surface strain-sensing line) was discretized into multiple small domains, with domain junctures matching the strain-sensing stations. Thus, the surface strain distribution could be described with a piecewise linear or a piecewise nonlinear function. The discretization approach enabled piecewise integrations of the embedded-beam curvature equations to yield the Curved Displacement Transfer Functions, expressed in terms of embedded beam geometrical parameters and surface strains. By entering the surface strain data into the Displacement Transfer Functions, deflections along each embedded beam can be calculated at multiple points for mapping the overall structural deformed shapes. Finite-element linear and nonlinear analyses of a tapered cantilever tubular beam were performed to generate linear and nonlinear surface strains and the associated deflections to be used for validation. The shape prediction accuracies were then determined by comparing the theoretical deflections with the finiteelement- generated deflections. The results show that the newly developed Curved Displacement Transfer Functions are very accurate for shape predictions of structures under large geometrically nonlinear deformations.
Institute of Scientific and Technical Information of China (English)
马利民; 王金星; 蒋向前; 李柱; 徐振高
2004-01-01
Geometrical Product Specification and verification (GPS) is an ISO standard system coveting standards of size, dimension,geometrical tolerance and surface texture of geometrical product. ISO/TC213 on the GPS has been working towards coordination of the previous standards in tolerance and related metrology in order to publish the next generation of the GPS language. This paper introduces the geometrical product specification model for design, manufacturing and verification based on the improved GPS and its new concepts,i.e., surface models, geometrical features and operations. An application example for the geometrical product specification model is then given.
Geometrical Models and Hadronic Radii
Zahra, Sarwat; Fazal-e-Aleem,; Hussain, Talib; Zafar, Abrar Ahmad; Tahir, Sohail Afzal
2015-01-01
By using electromagnetic form factors predicted by Generalized Chou Yang model (GCYM), we compute rms radii of several hadrons with varying strangeness content such as (Pion, Proton, Phi, Lambda0, Sigma+, Sigma- and Omega-). The computed radii are found quite consistent with the results of other models and experiments, indicating excellent predicting power of GCYM. The results indicate that rms radii decrease with increase in strangeness content, separately for mesons and baryons.
Geometrically nonlinear deformation and the emergent behavior of polarons in soft matter.
Li, Xiaobao; Liu, Liping; Sharma, Pradeep
2015-11-07
Mechanical strain can alter the electronic structure of both bulk semiconductors as well as nanostructures such as quantum dots. This fact has been extensively researched and exploited for tailoring electronic properties. The strain mediated interaction between the charge carriers and the lattice is interpreted through the so-called deformation potential. In the case of soft materials or nanostructures, such as DNA, the deformation potential leads to the formation of polarons which largely determine the electronic characteristics of DNA and similar polymer entities. In addition, polarons are also speculated to be responsible for the mechanism of quantum actuation in carbon nanotubes. The deformation potential is usually taken to be a linear function of the lattice deformation (U ∼ αε) where α is the deformation potential "constant" that determines the coupling strength and ε is the mechanical strain. In this letter, by carefully accounting for nonlinear geometric deformation that has been hitherto ignored so far in this context, we show that the deformation potential constant is renormalized in a non-trivial manner and is hardly a constant. It varies spatially within the material and with the size of the material. This effect, while negligible for hard materials, is found to be important for soft materials and critically impacts the interpretation of quantities such as polaron size, binding energy, and accordingly, electronic behavior.
Cavalcanti, R. T.; Goncalves da Silva, A.; da Rocha, Roldão
2016-11-01
In this paper we apply the strong deflection limit approach to investigate the gravitational lensing phenomena beyond general relativity. This is accomplished by considering the lensing effects related to black hole solutions that emerge out of the domain of Einstein gravity, namely, the ones acquired from the method of geometric deformation and the Casadio-Fabbri-Mazzacurati (CFM) brane-world black holes. The lensing observables, for those brane-world black hole metrics, are compared with the standard ones for the Schwarzschild case. We prove that brane-world black holes could have significantly different observational signatures, compared to the Schwarzschild black hole, with terms containing the post-Newtonian parameter, for the case of the CFM, and terms with variable brane-world tension, for the method of geometric deformation.
Symmetries and deformations in the spherical shell model
Van Isacker, P.; Pittel, S.
2016-02-01
We discuss symmetries of the spherical shell model that make contact with the geometric collective model of Bohr and Mottelson. The most celebrated symmetry of this kind is SU(3), which is the basis of Elliott’s model of rotation. It corresponds to a deformed mean field induced by a quadrupole interaction in a single major oscillator shell N and can be generalized to include several major shells. As such, Elliott’s SU(3) model establishes the link between the spherical shell model and the (quadrupole component of the) geometric collective model. We introduce the analogue symmetry induced by an octupole interaction in two major oscillator shells N-1 and N, leading to an octupole-deformed solution of the spherical shell model. We show that in the limit of large oscillator shells, N\\to ∞ , the algebraic octupole interaction tends to that of the geometric collective model.
Brane-world stars from minimal geometric deformation, and black holes
Casadio, Roberto; Ovalle, Jorge
2014-02-01
Using the effective four-dimensional Einstein field equations, we build analytical models of spherically symmetric stars in the brane-world, in which the external space-time contains both an ADM mass and a tidal charge. In order to determine the interior geometry, we apply the principle of minimal geometric deformation, which allows one to map general relativistic solutions to solutions of the effective four-dimensional brane-world equations. We further restrict our analysis to stars with a radius linearly related to the total general relativistic mass, and obtain a general relation between the latter, the brane-world ADM mass and the tidal charge. In these models, the value of the star's radius can then be taken to zero smoothly, thus obtaining brane-world black hole metrics with a tidal charge solely determined by the mass of the source and the brane tension. We find configurations which entail a partial screening of the gravitational mass, and general conclusions regarding the minimum mass for semiclassical black holes are also drawn.
Black Strings from Minimal Geometric Deformation in a Variable Tension Brane-World
Casadio, Roberto; da Rocha, Roldao
2013-01-01
We study brane-world models with variable brane tension and compute corrections to the horizon of a black string along the extra dimension. The four-dimensional geometry of the black string on the brane is obtained by means of the minimal geometric deformation approach, and the bulk corrections are then encoded in additional terms involving the covariant derivatives of the variable brane tension. Our investigation shows that the variable brane tension strongly affects the shape and evolution of the black string horizon along the extra dimension, at least in a near-brane expansion. In particular, we apply our general analysis to a model motivated by the E\\"otv\\"os branes, where the variable brane tension is related to the Friedmann-Robertson-Walker brane-world cosmology. We show that for some stages in the evolution of the universe, the black string warped horizon collapses to a point and the black string has correspondingly finite extent along the extra dimension. Furthermore, we show that in the minimal geom...
Classical Tests of General Relativity: Brane-World Sun from Minimal Geometric Deformation
Casadio, Roberto; da Rocha, Roldao
2015-01-01
We consider a solution of the effective four-dimensional brane-world equations, obtained from the General Relativistic Schwarzschild metric via the principle of Minimal Geometric Deformation, and investigate the corresponding signatures stemming from the possible existence of a warped extra dimension. In particular, we derive bounds on an extra-dimensional parameter, closely related with the fundamental gravitational length, from the experimental results of the classical tests of General Relativity in the Solar system.
Classical tests of general relativity: Brane-world Sun from minimal geometric deformation
Casadio, R.; Ovalle, J.; da Rocha, Roldão
2015-05-01
We consider a solution of the effective four-dimensional brane-world equations, obtained from the general relativistic Schwarzschild metric via the principle of minimal geometric deformation, and investigate the corresponding signatures stemming from the possible existence of a warped extra-dimension. In particular, we derive bounds on an extra-dimensional parameter, closely related with the fundamental gravitational length, from the experimental results of the classical tests of general relativity in the Solar system.
Model-based vision using geometric hashing
Akerman, Alexander, III; Patton, Ronald
1991-04-01
The Geometric Hashing technique developed by the NYU Courant Institute has been applied to various automatic target recognition applications. In particular, I-MATH has extended the hashing algorithm to perform automatic target recognition ofsynthetic aperture radar (SAR) imagery. For this application, the hashing is performed upon the geometric locations of dominant scatterers. In addition to being a robust model-based matching algorithm -- invariant under translation, scale, and 3D rotations of the target -- hashing is of particular utility because it can still perform effective matching when the target is partially obscured. Moreover, hashing is very amenable to a SIMD parallel processing architecture, and thus potentially realtime implementable.
A geometrical approach to structural change modeling
Stijepic, Denis
2013-01-01
We propose a model for studying the dynamics of economic structures. The model is based on qualitative information regarding structural dynamics, in particular, (a) the information on the geometrical properties of trajectories (and their domains) which are studied in structural change theory and (b) the empirical information from stylized facts of structural change. We show that structural change is path-dependent in this model and use this fact to restrict the number of future structural cha...
Advanced Geometric Modeler with Hybrid Representation
Institute of Scientific and Technical Information of China (English)
杨长贵; 陈玉健; 等
1996-01-01
An advanced geometric modeler GEMS4.0 has been developed,in which feature representation is used at the highest level abstraction of a product model.Boundary representation is used at the bottom level,while CSG model is adopted at the median level.A BRep data structure capable of modeling non-manifold is adopted.UNRBS representation is used for all curved surfaces,Quadric surfaces have dual representations consisting of their geometric data such as radius,center point,and center axis.Boundary representation of free form surfaces is easily built by sweeping and skinning method with NURBS geometry.Set operations on curved solids with boundary representation are performed by an evaluation process consisting of four steps.A file exchange facility is provided for the conversion between product data described by STEP and product information generated by GEMS4.0.
On deformations of triangulated models
De Deken, Olivier
2012-01-01
This paper is the first part of a project aimed at understanding deformations of triangulated categories, and more precisely their dg and A infinity models, and applying the resulting theory to the models occurring in the Homological Mirror Symmetry setup. In this first paper, we focus on models of derived and related categories, based upon the classical construction of twisted objects over a dg or $A_{\\infty}$-algebra. For a Hochschild 2 cocycle on such a model, we describe a corresponding "curvature compensating" deformation which can be entirely understood within the framework of twisted objects. We unravel the construction in the specific cases of derived A infinity and abelian categories, homotopy categories, and categories of graded free qdg-modules. We identify a purity condition on our models which ensures that the structure of the model is preserved under deformation. This condition is typically fulfilled for homotopy categories, but not for unbounded derived categories.
Geometric Models of the Relativistic Harmonic Oscillator
Cotaescu, I I
1997-01-01
A family of relativistic geometric models is defined as a generalization of the actual anti-de Sitter (1+1) model of the relativistic harmonic oscillator. It is shown that all these models lead to the usual harmonic oscillator in the non-relativistic limit, even though their relativistic behavior is quite different. Among quantum models we find a set of models with countable energy spectra, and another one having only a finite number of energy levels and in addition a continuous spectrum.
Deformed two center shell model
Gherghescu, R A
2003-01-01
A highly specialized two-center shell model has been developed accounting for the splitting of a deformed parent nucleus into two ellipsoidaly deformed fragments. The potential is based on deformed oscillator wells in direct correspondance with the shape change of the nuclear system. For the first time a potential responsible for the necking part between the fragments is introduced on potential theory basis. As a direct consequence, spin-orbit {\\bf ls} and {\\bf l$^2$} operators are calculated as shape dependent. Level scheme evolution along the fission path for pairs of ellipsoidaly deformed fragments is calculated. The Strutinsky method yields the shell corrections for different mass asymmetries from the superheavy nucleus $^{306}$122 and $^{252}$Cf all along the splitting process.
Geometric Algebra Model of Distributed Representations
Patyk, Agnieszka
2010-01-01
Formalism based on GA is an alternative to distributed representation models developed so far --- Smolensky's tensor product, Holographic Reduced Representations (HRR) and Binary Spatter Code (BSC). Convolutions are replaced by geometric products, interpretable in terms of geometry which seems to be the most natural language for visualization of higher concepts. This paper recalls the main ideas behind the GA model and investigates recognition test results using both inner product and a clipped version of matrix representation. The influence of accidental blade equality on recognition is also studied. Finally, the efficiency of the GA model is compared to that of previously developed models.
Geometrical geodesy techniques in Goddard earth models
Lerch, F. J.
1974-01-01
The method for combining geometrical data with satellite dynamical and gravimetry data for the solution of geopotential and station location parameters is discussed. Geometrical tracking data (simultaneous events) from the global network of BC-4 stations are currently being processed in a solution that will greatly enhance of geodetic world system of stations. Previously the stations in Goddard earth models have been derived only from dynamical tracking data. A linear regression model is formulated from combining the data, based upon the statistical technique of weighted least squares. Reduced normal equations, independent of satellite and instrumental parameters, are derived for the solution of the geodetic parameters. Exterior standards for the evaluation of the solution and for the scale of the earth's figure are discussed.
Geometrical model of multidimensional orbital motion
Energy Technology Data Exchange (ETDEWEB)
Jacak, D [Institute of Mathematics and Computer Science, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland)], E-mail: dorota.jacak@pwr.wroc.pl
2008-05-15
We consider a geometrical n-dimensional model of orbital-type rotation, for n{>=}4. The vectors generating this process are defined and the Fibonacci sequence is found in representation of their lengths. Within the dimension analysis of Planck units, we consider an example of the multidimensional whirl and define a sequence of formal fields. Special attention is paid to the three subsequent elements of this sequence, called here magnetic, electric and energy fields, which allow for some physical interpretations.
Dosimetric- and Geometric Evaluation of Adaptive H&N IMRT Using Deformable Image Registration
DEFF Research Database (Denmark)
Eiland, R.B.; Behrens, C. F.; Sjöström, D.
2012-01-01
Purpose/Objective: Anatomical changes can occur during RT treatment of H&N cancer patients. This can lead to a difference between planned- and delivered dose. Adaptive RT has the potential to overcome this, utilizing deformable image registration (DIR). The purpose of this study was to evaluate...... to the ReCT in four of seven patients with regard to the target. Larger geometrical variations were observed for organs at risk (OAR). OAR contours obtained with the DIR were for nearly all patients estimated smaller than in the ReCT whereas target contours were estimated larger. The dosimetric results...
Geometric Models of the Quantum Relativistic Rotating Oscillator
Cotaescu, I I
1997-01-01
A family of geometric models of quantum relativistic rotating oscillator is defined by using a set of one-parameter deformations of the static (3+1) de Sitter or anti-de Sitter metrics. It is shown that all these models lead to the usual isotropic harmonic oscillator in the non-relativistic limit, even though their relativistic behavior is different. As in the case of the (1+1) models, these will have even countable energy spectra or mixed ones, with a finite discrete sequence and a continuous part. In addition, all these spectra, except that of the pure anti-de Sitter model, will have a fine-structure, given by a rotator-like term.
Some Asymptotic Inference in Multinomial Nonlinear Models (a Geometric Approach)
Institute of Scientific and Technical Information of China (English)
WEIBOCHENG
1996-01-01
A geometric framework is proposed for multinomlat nonlinear modelsbased on a modified vemlon of the geometric structure presented by Bates & Watts[4]. We use this geometric framework to study some asymptotic inference in terms ofcurvtures for multlnomial nonlinear models. Our previous results [15] for ordlnary nonlinear regression models are extended to multlnomlal nonlinear models.
Smoothing Algorithm for Planar and Surface Mesh Based on Element Geometric Deformation
Directory of Open Access Journals (Sweden)
Shuli Sun
2015-01-01
Full Text Available Smoothing is one of the basic procedures for improvement of mesh quality. In this paper, a novel and efficient smoothing approach for planar and surface mesh based on element geometric deformation is developed. The presented approach involves two main stages. The first stage is geometric deformation of all the individual elements through a specially designed two-step stretching-shrinking operation (SSO, which is performed by moving the vertices of each element according to a certain rule in order to get better shape of the element. The second stage is to determine the position of each node of the mesh by a weighted average strategy according to quality changes of its adjacent elements. The suggested SSO-based smoothing algorithm works efficiently for triangular mesh and can be naturally expanded to quadrilateral mesh, arbitrary polygonal mesh, and mixed mesh. Combined with quadratic error metric (QEM, this approach may be also applied to improve the quality of surface mesh. The proposed method is simple to program and inherently very suitable for parallelization, especially on graphic processing unit (GPU. Results of numerical experiments demonstrate the effectiveness and potential of this method.
Liao, Fei; Ye, Zhengyin
2015-12-01
Despite significant progress in recent computational techniques, the accurate numerical simulations, such as direct-numerical simulation and large-eddy simulation, are still challenging. For accurate calculations, the high-order finite difference method (FDM) is usually adopted with coordinate transformation from body-fitted grid to Cartesian grid. But this transformation might lead to failure in freestream preservation with the geometric conservation law (GCL) violated, particularly in high-order computations. GCL identities, including surface conservation law (SCL) and volume conservation law (VCL), are very important in discretization of high-order FDM. To satisfy GCL, various efforts have been made. An early and successful approach was developed by Thomas and Lombard [6] who used the conservative form of metrics to cancel out metric terms to further satisfy SCL. Visbal and Gaitonde [7] adopted this conservative form of metrics for SCL identities and satisfied VCL identity through invoking VCL equation to acquire the derivative of Jacobian in computation on moving and deforming grids with central compact schemes derived by Lele [5]. Later, using the metric technique from Visbal and Gaitonde [7], Nonomura et al. [8] investigated the freestream and vortex preservation properties of high-order WENO and WCNS on stationary curvilinear grids. A conservative metric method (CMM) was further developed by Deng et al. [9] with stationary grids, and detailed discussion about the innermost difference operator of CMM was shown with proof and corresponding numerical test cases. Noticing that metrics of CMM is asymmetrical without coordinate-invariant property, Deng et al. proposed a symmetrical CMM (SCMM) [12] by using the symmetric forms of metrics derived by Vinokur and Yee [10] to further eliminate asymmetric metric errors with stationary grids considered only. The research from Abe et al. [11] presented new asymmetric and symmetric conservative forms of time metrics and
Symmetry in Image Registration and Deformation Modeling
DEFF Research Database (Denmark)
Sommer, Stefan; Jacobs, Henry O.
We survey the role of symmetry in diffeomorphic registration of landmarks, curves, surfaces, images and higher-order data. The infinite dimensional problem of finding correspondences between objects can for a range of concrete data types be reduced resulting in compact representations of shape...... and spatial structure. This reduction is possible because the available data is incomplete in encoding the full deformation model. Using reduction by symmetry, we describe the reduced models in a common theoretical framework that draws on links between the registration problem and geometric mechanics....... Symmetry also arises in reduction to the Lie algebra using particle relabeling symmetry allowing the equations of motion to be written purely in terms of Eulerian velocity field. Reduction by symmetry has recently been applied for jet-matching and higher-order discrete approximations of the image matching...
Knowledge-based geometric modeling in construction
DEFF Research Database (Denmark)
Bonev, Martin; Hvam, Lars
2012-01-01
a considerably high amount of their recourses is required for designing and specifying the majority of their product assortment. As design decisions are hereby based on knowledge and experience about behaviour and applicability of construction techniques and materials for a predefined design situation, smart...... tools need to be developed, to support these activities. In order to achieve a higher degree of design automation, this study proposes a framework for using configuration systems within the CAD environment together with suitable geometric modeling techniques on the example of a Danish manufacturer...
Young Children's Understanding of Geometric Shapes: The Role of Geometric Models
Elia, Iliada; Gagatsis, Athanasios; Kyriakides, Leonidas
2003-01-01
In this paper, we explore the role of polygonal shapes as geometrical models in teaching mathematics, so as to elicit and interpret children's geometric conceptions and understanding about shapes. Primary pupils were asked to draw a stairway of figures (triangles, squares and rectangles) each one bigger than the preceding one. Pupils use two…
Geometric Model of a Coronal Cavity
Kucera, Therese A.; Gibson, S. E.; Ratawicki, D.; Dove, J.; deToma, G.; Hao, J.; Hudson, H. S.; Marque, C.; McIntosh, P. S.; Reeves, K. K.;
2010-01-01
We observed a coronal cavity from August 8-18 2007 during a multi-instrument observing campaign organized under the auspices of the International Heliophysical Year (IHY). Here we present initial efforts to model the cavity with a geometrical streamer-cavity model. The model is based the white-light streamer mode] of Gibson et a]. (2003 ), which has been enhanced by the addition of a cavity and the capability to model EUV and X-ray emission. The cavity is modeled with an elliptical cross-section and Gaussian fall-off in length and width inside the streamer. Density and temperature can be varied in the streamer and cavity and constrained via comparison with data. Although this model is purely morphological, it allows for three-dimensional, multi-temperature analysis and characterization of the data, which can then provide constraints for future physical modeling. Initial comparisons to STEREO/EUVI images of the cavity and streamer show that the model can provide a good fit to the data. This work is part of the effort of the International Space Science Institute International Team on Prominence Cavities
Geometric Model of a Coronal Cavity
Kucera, Therese A.; Gibson, S. E.; Ratawicki, D.; Dove, J.; deToma, G.; Hao, J.; Hudson, H. S.; Marque, C.; McIntosh, P. S.; Reeves, K. K.; Schmidt, D. J.; Sterling, A. C.; Tripathi, D. K.; Williams, D. R.; Zhang, M.
2010-01-01
We observed a coronal cavity from August 8-18 2007 during a multi-instrument observing campaign organized under the auspices of the International Heliophysical Year (IHY). Here we present initial efforts to model the cavity with a geometrical streamer-cavity model. The model is based the white-light streamer mode] of Gibson et a]. (2003 ), which has been enhanced by the addition of a cavity and the capability to model EUV and X-ray emission. The cavity is modeled with an elliptical cross-section and Gaussian fall-off in length and width inside the streamer. Density and temperature can be varied in the streamer and cavity and constrained via comparison with data. Although this model is purely morphological, it allows for three-dimensional, multi-temperature analysis and characterization of the data, which can then provide constraints for future physical modeling. Initial comparisons to STEREO/EUVI images of the cavity and streamer show that the model can provide a good fit to the data. This work is part of the effort of the International Space Science Institute International Team on Prominence Cavities
Zhevlakov, A. P.; Zatsepina, M. E.; Kirillovskii, V. K.
2014-06-01
The principles of transformation of a Foucault shadowgram into a quantitative map of wave-front deformation based on creation of a system of isophotes are unveiled. The presented studies and their results prove that there is a high degree of correspondence between a Foucault shadowgram and the geometrical model of a shear interferogram with respect to displaying wave-front deformations.
Wang, Chuntao; Ni, Jiangqun; Zhang, Dong
2013-12-01
Counteracting geometrical attacks remains one of the most challenging problems in robust watermarking. In this paper, we resist rotation, scaling, and translation (RST) by constructing a kind of deformable pyramid transform (DPT) that is shift-invariant, steerable, and scalable. The DPT is extended from a closed-form polar-separable steerable pyramid transform (SPT). The radial component of the SPT's basis filters is taken as the kernel of the scalable basis filters, and the angular component is used for the steerable basis filters. The shift-invariance is inherited from the SPT by retaining undecimated high-pass and band-pass subbands. Based on the designed DPT, we theoretically derive interpolation functions for steerability and scalability and synchronization mechanisms for translation, rotation, and scaling. By exploiting the preferable characteristics of DPT, we develop a new template-based robust image watermarking scheme that is resilient to RST. Translation invariance is achieved by taking the Fourier magnitude of the cover image as the DPT's input. The resilience to rotation and scaling is obtained using the synchronization mechanisms for rotation and scaling, for which an efficient template-matching algorithm has been devised. Extensive simulations show that the proposed scheme is highly robust to geometrical attacks, such as RST, cropping, and row/column line removal, as well as common signal processing attacks such as JPEG compression, additive white Gaussian noise, and median filtering.
Geometric Modeling of Inclusions as Ellipsoids
Bonacuse, Peter J.
2008-01-01
Nonmetallic inclusions in gas turbine disk alloys can have a significant detrimental impact on fatigue life. Because large inclusions that lead to anomalously low lives occur infrequently, probabilistic approaches can be utilized to avoid the excessively conservative assumption of lifing to a large inclusion in a high stress location. A prerequisite to modeling the impact of inclusions on the fatigue life distribution is a characterization of the inclusion occurrence rate and size distribution. To help facilitate this process, a geometric simulation of the inclusions was devised. To make the simulation problem tractable, the irregularly sized and shaped inclusions were modeled as arbitrarily oriented, three independent dimensioned, ellipsoids. Random orientation of the ellipsoid is accomplished through a series of three orthogonal rotations of axes. In this report, a set of mathematical models for the following parameters are described: the intercepted area of a randomly sectioned ellipsoid, the dimensions and orientation of the intercepted ellipse, the area of a randomly oriented sectioned ellipse, the depth and width of a randomly oriented sectioned ellipse, and the projected area of a randomly oriented ellipsoid. These parameters are necessary to determine an inclusion s potential to develop a propagating fatigue crack. Without these mathematical models, computationally expensive search algorithms would be required to compute these parameters.
Integrable Deformations of T -Dual σ Models
Borsato, Riccardo; Wulff, Linus
2016-12-01
We present a method to deform (generically non-Abelian) T duals of two-dimensional σ models, which preserves classical integrability. The deformed models are identified by a linear operator ω on the dualized subalgebra, which satisfies the 2-cocycle condition. We prove that the so-called homogeneous Yang-Baxter deformations are equivalent, via a field redefinition, to our deformed models when ω is invertible. We explain the details for deformations of T duals of principal chiral models, and present the corresponding generalization to the case of supercoset models.
Deformations of the Almheiri-Polchinski model
Kyono, Hideki; Okumura, Suguru; Yoshida, Kentaroh
2017-03-01
We study deformations of the Almheiri-Polchinski (AP) model by employing the Yang-Baxter deformation technique. The general deformed AdS2 metric becomes a solution of a deformed AP model. In particular, the dilaton potential is deformed from a simple quadratic form to a hyperbolic function-type potential similarly to integrable deformations. A specific solution is a deformed black hole solution. Because the deformation makes the spacetime structure around the boundary change drastically and a new naked singularity appears, the holographic interpretation is far from trivial. The Hawking temperature is the same as the undeformed case but the Bekenstein-Hawking entropy is modified due to the deformation. This entropy can also be reproduced by evaluating the renormalized stress tensor with an appropriate counter-term on the regularized screen close to the singularity.
Geometric model of robotic arc welding for automatic programming
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
Geometric information is important for automatic programming of arc welding robot. Complete geometric models of robotic arc welding are established in this paper. In the geometric model of weld seam, an equation with seam length as its parameter is introduced to represent any weld seam. The method to determine discrete programming points on a weld seam is presented. In the geometric model of weld workpiece, three class primitives and CSG tree are used to describe weld workpiece. Detailed data structure is presented. In pose transformation of torch, world frame, torch frame and active frame are defined, and transformation between frames is presented. Based on these geometric models, an automatic programming software package for robotic arc welding, RAWCAD, is developed. Experiments show that the geometric models are practical and reliable.
A population based statistical model for daily geometric variations in the thorax.
Szeto, Yenny Z; Witte, Marnix G; van Herk, Marcel; Sonke, Jan-Jakob
2017-04-01
To develop a population based statistical model of the systematic interfraction geometric variations between the planning CT and first treatment week of lung cancer patients for inclusion as uncertainty term in future probabilistic planning. Deformable image registrations between the planning CT and first week CBCTs of 235 lung cancer patients were used to generate deformation vector fields (DVFs) representing the geometric variations of lung cancer patients. Using a second deformable registration step, the average DVF per patient was mapped to an average patient CT. Subsequently, the dominant modes of systematic geometric variations were extracted using Principal Component Analysis (PCA). For evaluation a leave-one-out cross-validation was performed. The first three PCA components mainly described cranial-caudal, anterior-posterior, and left-right variations, respectively. Fifty and 112 components were needed to describe correspondingly 75% and 90% of the variance. An overall systematic variation of 3.6mm SD was observed and could be described with an accuracy of about 1.0mm with the PCA model. A PCA based model for systematic geometric variations in the thorax was developed, and its accuracy determined. Such a model can serve as a basis for probability based treatment planning in lung cancer patients. Copyright © 2017 Elsevier B.V. All rights reserved.
Kovaleva, Elizaveta; Klötzli, Urs; Habler, Gerlinde
2016-10-01
We present novel microstructural analyses of zircon from a variety of strained rocks. For the first time, multiple plastically deformed zircon crystals were analyzed in a kinematic context of the respective host shear zones. Our aim was to derive how the orientation of zircon grains in a shear zone affects their deformation, based on careful in situ observations. For sampling, we selected zircon-bearing rocks that were deformed by simple shear. Samples covered a range of P-T conditions and lithologies, including various meta-igneous and meta-sedimentary gneisses. Microstructural analyses of zircon crystals in situ with scanning electron backscatter diffraction mapping show strong geometrical relationships between orientations of: (i) the long axes of plastically deformed zircon crystals, (ii) the crystallographic orientation of misorientation axes in plastically deformed zircon crystals and (iii) the foliation and lineation directions of the respective samples. We assume that zircon crystals did not experience post-deformation rigid body rotation, and thus the true geometric link can be observed. The relationships are the following: (a) plastically deformed zircon crystals usually have long axes parallel to the mylonitic foliation plane; (b) crystals with axes oriented at an angle > 15° to the foliation plane are undeformed or fractured. Zircon crystals that have axes aligned parallel or normal to the stretching lineation within the foliation plane develop misorientation and rotation axes parallel to the [001] crystallographic direction. Zircon grains with the axis aligned at 30-60° to the lineation within the foliation plane often develop either two low Miller indices misorientation axes or one high Miller indices misorientation axis. Host phases have a significant influence on deformation mechanisms. In a relatively soft matrix, zircon is more likely to develop low Miller indices misorientation axes than in a relatively strong matrix. These relationships are
Yang-Mills equation for the nuclear geometrical collective model connexion
Sparks, N.; Rosensteel, G.
2017-01-01
The Bohr-Mottelson collective model of rotations and quadrupole vibrations is a foundational model in nuclear structure physics. A modern formulation using differential geometry of bundles builds on this legacy collective model to allow a deformation-dependent interaction between rotational and vortical degrees of freedom. The interaction is described by the bundle connexion. This article reports the Yang-Mills equation for the connexion. For a class of solutions to the Yang-Mills equation, the differential geometric collective model attains agreement between experiment and theory for the moments of inertia of deformed isotopes. More generally, the differential geometric framework applies to models of emergent phenomena in which two interacting sets of degrees of freedom must be unified.
Geometric Properties of AR（q） Nonlinear Regression Models
Institute of Scientific and Technical Information of China (English)
LIUYing-ar; WEIBo-cheng
2004-01-01
This paper is devoted to a study of geometric properties of AR(q) nonlinear regression models. We present geometric frameworks for regression parameter space and autoregression parameter space respectively based on the weighted inner product by fisher information matrix. Several geometric properties related to statistical curvatures are given for the models. The results of this paper extended the work of Bates & Watts(1980,1988)[1.2] and Seber & Wild (1989)[3].
Geometrical modeling of fibrous materials under compression
Maze, Benoit; Tafreshi, Hooman Vahedi; Pourdeyhimi, Behnam
2007-10-01
Many fibrous materials such as nonwovens are consolidated via compaction rolls in a so-called calendering process. Hot rolls compress the fiber assembly and cause fiber-to-fiber bonding resulting in a strong yet porous structure. In this paper, we describe an algorithm for generating three dimensional virtual fiberwebs and simulating the geometrical changes that happen to the structure during the calendering process. Fibers are assumed to be continuous filaments with square cross sections lying randomly in the x or y direction. The fibers are assumed to be flexible to allow bending over one another during the compression process. Lateral displacement is not allowed during the compaction process. The algorithm also does not allow the fibers to interpenetrate or elongate and so the mass of the fibers is conserved. Bending of the fibers is modeled either by considering a constant "slope of bending" or constant "span of bending." The influence of the bending parameters on the propagation of compression through the material's thickness is discussed. In agreement with our experimental observations, it was found that the average solid volume fraction profile across the thickness becomes U shaped after the calendering. The application of these virtual structures in studying transport phenomena in fibrous materials is also demonstrated.
Geometric deviation modeling by kinematic matrix based on Lagrangian coordinate
Liu, Weidong; Hu, Yueming; Liu, Yu; Dai, Wanyi
2015-09-01
Typical representation of dimension and geometric accuracy is limited to the self-representation of dimension and geometric deviation based on geometry variation thinking, yet the interactivity affection of geometric variation and gesture variation of multi-rigid body is not included. In this paper, a kinematic matrix model based on Lagrangian coordinate is introduced, with the purpose of unified model for geometric variation and gesture variation and their interactive and integrated analysis. Kinematic model with joint, local base and movable base is built. The ideal feature of functional geometry is treated as the base body; the fitting feature of functional geometry is treated as the adjacent movable body; the local base of the kinematic model is fixed onto the ideal geometry, and the movable base of the kinematic model is fixed onto the fitting geometry. Furthermore, the geometric deviation is treated as relative location or rotation variation between the movable base and the local base, and it's expressed by the Lagrangian coordinate. Moreover, kinematic matrix based on Lagrangian coordinate for different types of geometry tolerance zones is constructed, and total freedom for each kinematic model is discussed. Finally, the Lagrangian coordinate library, kinematic matrix library for geometric deviation modeling is illustrated, and an example of block and piston fits is introduced. Dimension and geometric tolerances of the shaft and hole fitting feature are constructed by kinematic matrix and Lagrangian coordinate, and the results indicate that the proposed kinematic matrix is capable and robust in dimension and geometric tolerances modeling.
A Geometrical Model for Non-Zero $\\theta_{13}$
Chen, Jun-Mou; Li, Xue-Qian
2011-01-01
Based on Friedberg and Lee's geometric picture by which the tribimaximal PMNS leptonic mixing matrix is constructed, namely corresponding mixing angles correspond to the geometric angles among the sides of a cube. We suggest that the three realistic mixing angles which slightly deviate from the values determined for the cube, are due to a viable deformation from the perfectly cubic shape. Taking the best fitted results of $\\theta_{12}$ and $\\theta_{23}$ as inputs, we determine the central value of $\\sin^22\\theta_{13}$ should be 0.0238 with a relatively large error tolerance, this value lies in the range of measurement precision of the Daya Bay experiment.
Initialization and Optimation of Deformable Models
DEFF Research Database (Denmark)
Jensen, Rune Fisker; Carstensen, Jens Michael; Madsen, Kaj
1999-01-01
The deformable model literature has in general been very focused on the formulation and development of new models or the solution of a specific application. Teh final and crucial steps of initialization and optimazation of the deformable model, needed for making inference, have received very little...
Modelling the deformation process of flexible stamps for nanoimprint lithography
DEFF Research Database (Denmark)
Sonne, Mads Rostgaard
The present thesis is devoted to numerical modelling of the deformation process of flexible stamps for nanoimprint lithography (NIL). The purpose of those models is to be able to predict the deformation and stretch of the flexixble stamps in order to take that into account when designing the plan...... 2D silicon master used in the NIL process. Two different manufacturing processes are investigated; (i) Embossing of an electroplated nickel foil into a hydrogen silsesquioxane (HSQ) polymer resist on a double-curved surface, (ii) NIL of a flexible polytetrafluoroethylene (PTFE) stamps...... into a polymethyl methacrylate (PMMA) resist. Challenges comprise several non-linear phenomena. First of all geometrical non-linearities arising from the inherent large strains and deformations during the process are modelled. Then, the constitutive behaviors of the nickel foil and the PTFE polymer during...... deformation are addressed. This is achieved by a general elasto-plastic description for the nickel foil and a viscoelastic-viscoplastic model for the PTFE material, in which the material parameters are found. Last, the contact conditions between the deforming stamp and the injection moulding tool insert...
Geometric aspects of shear jamming induced by deformation of frictionless sphere packings
Vinutha, H. A.; Sastry, Srikanth
2016-09-01
It has recently been demonstrated that shear deformation of frictionless sphere packings leads to structures that will undergo jamming in the presence of friction, at densities well below the isotropic jamming point {φj}≈ 0.64 , and at high enough strains. Here, we show that the geometric features induced by strain are robust with respect to finite size effects, and include the feature of hyperuniformity, previously studied in the context of jamming, and more recently in driven systems. We study the approach to jamming as strain is increased, by evolving frictionless sheared configurations through frictional dynamics, and thereby identify a critical, or jamming, strain for each density, for a chosen value of the coefficient of friction. In the presence of friction above a certain strain value the sheared frictionless packings begin to develop finite stresses, which marks the onset of shear jamming. At a higher strain value, the shear stress reaches a saturation value after rising rapidly above the onset of shear jamming, which permits identification of the shear jamming transition. The onset of shear jamming and shear jamming are found to occur when the coordination number Z reaches values of Z = 3 and Z = 4 respectively. By considering percolation probabilities for the contact network, clusters of four coordinated and six coordinated spheres, we show that the percolation of four coordinated spheres corresponds to the onset of shear jamming behaviour, whereas the percolation of six coordinated spheres corresponds to shear jamming, for the chosen friction coefficients. At the onset of shear jamming, the force distribution begins to develop a peak at finite value and the force network is anisotropic and heterogeneous. And at the shear jamming transition, the force distribution has a well defined peak close to and the force network is less anisotropic and homogeneous. We briefly discuss mechanical aspects of the jamming behaviour by performing
Corotational formulation for 3d solids. An analysis of geometrically nonlinear foam deformation
Kaczmarczyk, Łukasz; Pearce, Chris J
2011-01-01
This paper presents theory for the Lagrange co-rotational (CR) formulation of finite elements in the geometrically nonlinear analysis of 3D structures. In this paper strains are assumed to be small while the magnitude of rotations from the reference configuration is not restricted. A new best fit rotator and consistent spin filter are derived. Lagrange CR formulation is applied with Hybrid Trefftz Stress elements, although presented methodology can be applied to arbitrary problem formulation and discretization technique, f.e. finite volume methods and lattice models, discreet element methods. Efficiency of CR formulation can be utilized in post-buckling stability analysis, damage and fracture mechanics, modelling of dynamic fragmentation of bodies made from quasi-brittle materials, solid fluid interactions and analysis of post-stressed structures, discreet body dynamics.
On parameter estimation in deformable models
DEFF Research Database (Denmark)
Fisker, Rune; Carstensen, Jens Michael
1998-01-01
Deformable templates have been intensively studied in image analysis through the last decade, but despite its significance the estimation of model parameters has received little attention. We present a method for supervised and unsupervised model parameter estimation using a general Bayesian...... method is based on a modified version of the EM algorithm. Experimental results for a deformable template used for textile inspection are presented...
Some geometric models of ancient astronomy with Geogebra
Directory of Open Access Journals (Sweden)
Leandro Tortosa
2010-05-01
Full Text Available The main objective of this work is to review and simulate, with the help of GeoGebra, the most important geometric models used by the ancient astronomers to explain the mechanisms governing the trajectories of celestial bodies in the sky. It is well known that ancient astronomers like Ptolemy, Copernicus, Galileo, invented the same complex geometric systems of circles to explain the motion of the celestial bodies. It was not until Kepler, with the introduction of conics in the geometric models, that it was possible to accurately explain the observations with theoretical models.
Deformation Models Tracking, Animation and Applications
Torres, Arnau; Gómez, Javier
2013-01-01
The computational modelling of deformations has been actively studied for the last thirty years. This is mainly due to its large range of applications that include computer animation, medical imaging, shape estimation, face deformation as well as other parts of the human body, and object tracking. In addition, these advances have been supported by the evolution of computer processing capabilities, enabling realism in a more sophisticated way. This book encompasses relevant works of expert researchers in the field of deformation models and their applications. The book is divided into two main parts. The first part presents recent object deformation techniques from the point of view of computer graphics and computer animation. The second part of this book presents six works that study deformations from a computer vision point of view with a common characteristic: deformations are applied in real world applications. The primary audience for this work are researchers from different multidisciplinary fields, s...
The Nuclear Shape Phase Transitions Studied within the Geometric Collective Model
Directory of Open Access Journals (Sweden)
Khalaf A. M.
2013-04-01
Full Text Available In the framework of the Geometric Collective Model (GCM, quantum phase transition between spherical and deformed shapes of doubly even nuclei are investigated. The validity of the model is examined for the case of lanthanide chains Nd / Sm and actinide chains Th / U. The parameters of the model were obtained by performing a computer simulated search program in order to obtain minimum root mean square deviations be- tween the calculated and the experimental excitation energies. Calculated potential en- ergy surfaces (PES’s describing all deformation effects of each nucleus are extracted. Our systematic studies on lanthanide and actinide chains have revealed a shape transi- tion from spherical vibrator to axially deformed rotor when moving from the lighter to the heavier isotopes.
Multipartite geometric entanglement in finite size XY model
Energy Technology Data Exchange (ETDEWEB)
Blasone, Massimo; Dell' Anno, Fabio; De Siena, Silvio; Giampaolo, Salvatore Marco; Illuminati, Fabrizio, E-mail: blasone@sa.infn.i [Dipartimento di Matematica e Informatica, Universita degli Studi di Salerno, Via Ponte don Melillo, I-84084 Fisciano (Italy)
2009-06-01
We investigate the behavior of the multipartite entanglement in the finite size XY model by means of the hierarchical geometric measure of entanglement. By selecting specific components of the hierarchy, we study both global entanglement and genuinely multipartite entanglement.
A geometric construction of traveling waves in a bioremediation model
Beck, M.A.; Doelman, A.; Kaper, T.J.
2006-01-01
Bioremediation is a promising technique for cleaning contaminated soil. We study an idealized bioremediation model involving a substrate (contaminant to be removed), electron acceptor (added nutrient), and microorganisms in a one-dimensional soil column. Using geometric singular perturbation theory,
Integration of geometric modeling and advanced finite element preprocessing
Shephard, Mark S.; Finnigan, Peter M.
1987-01-01
The structure to a geometry based finite element preprocessing system is presented. The key features of the system are the use of geometric operators to support all geometric calculations required for analysis model generation, and the use of a hierarchic boundary based data structure for the major data sets within the system. The approach presented can support the finite element modeling procedures used today as well as the fully automated procedures under development.
Sigma models for genuinely non-geometric backgrounds
Chatzistavrakidis, Athanasios; Lechtenfeld, Olaf
2015-01-01
The existence of genuinely non-geometric backgrounds, i.e. ones without geometric dual, is an important question in string theory. In this paper we examine this question from a sigma model perspective. First we construct a particular class of Courant algebroids as protobialgebroids with all types of geometric and non-geometric fluxes. For such structures we apply the mathematical result that any Courant algebroid gives rise to a 3D topological sigma model of the AKSZ type and we discuss the corresponding 2D field theories. It is found that these models are always geometric, even when both 2-form and 2-vector fields are neither vanishing nor inverse of one another. Taking a further step, we suggest an extended class of 3D sigma models, whose world volume is embedded in phase space, which allow for genuinely non-geometric backgrounds. Adopting the doubled formalism such models can be related to double field theory, albeit from a world sheet perspective.
Deformable Models for Eye Tracking
DEFF Research Database (Denmark)
Vester-Christensen, Martin; Leimberg, Denis; Ersbøll, Bjarne Kjær;
2005-01-01
A deformable template method for eye tracking on full face images is presented. The strengths of the method are that it is fast and retains accuracy independently of the resolution. We compare the me\\$\\backslash\\$-thod with a state of the art active contour approach, showing that the heuristic...
Geometrical model for non-zero θ13
Chen, Jun-Mou; Wang, Bin; Li, Xue-Qian
2011-10-01
Based on Friedberg and Lee’s geometric picture by which the tribimaximal Pontecorvo-Maki-Nakawaga-Sakata leptonic mixing matrix is constructed, namely, corresponding mixing angles correspond to the geometric angles among the sides of a cube. We suggest that the three realistic mixing angles, which slightly deviate from the values determined for the cube, are due to a viable deformation from the perfectly cubic shape. Taking the best-fitted results of θ12 and θ23 as inputs, we determine the central value of sin22θ13 should be 0.0238, with a relatively large error tolerance; this value lies in the range of measurement precision of the Daya Bay experiment and is consistent with recent results from the T2K Collaboration.
Multiscale geometric modeling of macromolecules II: Lagrangian representation.
Feng, Xin; Xia, Kelin; Chen, Zhan; Tong, Yiying; Wei, Guo-Wei
2013-09-15
Geometric modeling of biomolecules plays an essential role in the conceptualization of biolmolecular structure, function, dynamics, and transport. Qualitatively, geometric modeling offers a basis for molecular visualization, which is crucial for the understanding of molecular structure and interactions. Quantitatively, geometric modeling bridges the gap between molecular information, such as that from X-ray, NMR, and cryo-electron microscopy, and theoretical/mathematical models, such as molecular dynamics, the Poisson-Boltzmann equation, and the Nernst-Planck equation. In this work, we present a family of variational multiscale geometric models for macromolecular systems. Our models are able to combine multiresolution geometric modeling with multiscale electrostatic modeling in a unified variational framework. We discuss a suite of techniques for molecular surface generation, molecular surface meshing, molecular volumetric meshing, and the estimation of Hadwiger's functionals. Emphasis is given to the multiresolution representations of biomolecules and the associated multiscale electrostatic analyses as well as multiresolution curvature characterizations. The resulting fine resolution representations of a biomolecular system enable the detailed analysis of solvent-solute interaction, and ion channel dynamics, whereas our coarse resolution representations highlight the compatibility of protein-ligand bindings and possibility of protein-protein interactions.
DEFF Research Database (Denmark)
Sonne, Mads Rostgaard; Cech, Jiri; Hattel, Jesper Henri;
2013-01-01
. Experimentally, it is possible to address this stretch by counting the periods of the cross-gratings via SEM characterization. A model for the deformation of the nickel foil during nanoimprint is developed, utilizing non-linear material and geometrical behaviour. Good agreement between measured and numerically...... calculated stretch ratios on the surface of the deformed nickel foil is found, and it is shown, that from the model it is also possible to predict the geometrical extend of the nano-structured area on the curved surfaces....
Leukocyte deformability: finite element modeling of large viscoelastic deformation.
Dong, C; Skalak, R
1992-09-21
An axisymmetric deformation of a viscoelastic sphere bounded by a prestressed elastic thin shell in response to external pressure is studied by a finite element method. The research is motivated by the need for understanding the passive behavior of human leukocytes (white blood cells) and interpreting extensive experimental data in terms of the mechanical properties. The cell at rest is modeled as a sphere consisting of a cortical prestressed shell with incompressible Maxwell fluid interior. A large-strain deformation theory is developed based on the proposed model. General non-linear, large strain constitutive relations for the cortical shell are derived by neglecting the bending stiffness. A representation of the constitutive equations in the form of an integral of strain history for the incompressible Maxwell interior is used in the formulation of numerical scheme. A finite element program is developed, in which a sliding boundary condition is imposed on all contact surfaces. The mathematical model developed is applied to evaluate experimental data of pipette tests and observations of blood flow.
Geometric modeling of subcellular structures, organelles, and multiprotein complexes
Feng, Xin; Xia, Kelin; Tong, Yiying; Wei, Guo-Wei
2013-01-01
SUMMARY Recently, the structure, function, stability, and dynamics of subcellular structures, organelles, and multi-protein complexes have emerged as a leading interest in structural biology. Geometric modeling not only provides visualizations of shapes for large biomolecular complexes but also fills the gap between structural information and theoretical modeling, and enables the understanding of function, stability, and dynamics. This paper introduces a suite of computational tools for volumetric data processing, information extraction, surface mesh rendering, geometric measurement, and curvature estimation of biomolecular complexes. Particular emphasis is given to the modeling of cryo-electron microscopy data. Lagrangian-triangle meshes are employed for the surface presentation. On the basis of this representation, algorithms are developed for surface area and surface-enclosed volume calculation, and curvature estimation. Methods for volumetric meshing have also been presented. Because the technological development in computer science and mathematics has led to multiple choices at each stage of the geometric modeling, we discuss the rationales in the design and selection of various algorithms. Analytical models are designed to test the computational accuracy and convergence of proposed algorithms. Finally, we select a set of six cryo-electron microscopy data representing typical subcellular complexes to demonstrate the efficacy of the proposed algorithms in handling biomolecular surfaces and explore their capability of geometric characterization of binding targets. This paper offers a comprehensive protocol for the geometric modeling of subcellular structures, organelles, and multiprotein complexes. PMID:23212797
Method to geometrically personalize a detailed finite-element model of the spine.
Lalonde, Nadine Michèle; Petit, Yvan; Aubin, Carl-Eric; Wagnac, Eric; Arnoux, Pierre-Jean
2013-07-01
To date, developing geometrically personalized and detailed solid finite-element models (FEMs) of the spine remains a challenge, notably due to multiple articulations and complex geometries. To answer this problem, a methodology based on a free-form deformation technique (kriging) was developed to deform a detailed reference finite-element mesh of the spine (including discs and ligaments) to the patient-specific geometry of 10- and 82-year-old asymptomatic spines. Different kriging configurations were tested: with or without smoothing, and control points on or surrounding the entire mesh. Based on the results, it is recommended to use surrounding control points and smoothing. The mean node to surface distance between the deformed and target geometries was 0.3±1.1 mm. Most elements met the mesh quality criteria (95%) after deformation, without interference at the articular facets. The method's novelty lies in the deformation of the entire spine at once, as opposed to deforming each vertebra separately, with surrounding control points and smoothing. This enables the transformation of reference vertebrae and soft tissues to obtain complete and personalized FEMs of the spine with minimal postprocessing to optimize the mesh.
Geometrical and physical properties of the 1982-84 deformation source at Campi Flegrei - Italy
Bonafede, Maurizio; Trasatti, Elisa; Giunchi, Carlo; Berrino, Giovanna
2010-05-01
Deformation of the ground surface in volcanic areas is generally recognized as a reliable indicator of unrest, possibly resulting from the intrusion of fresh magma within the shallow rock layers. The intrusion process is usually represented by a deformation source such as an ellipsoidal pressurized cavity, embedded within a homogeneous and elastic half-space. Similar source models allow inferring the depth, the location and the (incremental) volume of the intrusion, which are very important parameters for volcanic risk implications. However, assuming a homogeneous and elastic rheology and, assigning a priori the shape and the mechanism of the source (within a very restricted 'library' of available solutions) may bias considerably the inference of source parameters. In complete generality, any point source deformation, including overpressure sources, may be described in terms of a suitable moment tensor, while the assumption of an overpressure source strongly restricts the variety of allowable moment tensors. In particular, by assuming a pressurized cavity, we rule out the possibility that either shear failure may precede magma emplacement (seismically induced intrusion) or may accompany it (mixed tensile and shear mode fracture). Another possibility is that a pre-existent weakness plane may be chosen by the ascending magma (fracture toughness heterogeneity). We perform joint inversion of levelling and EDM data (part of latter are unpublished), collected during the 1982-84 unrest at Campi Flegrei caldera: a 43% misfit reduction is obtained for a general moment source if the elastic heterogeneities computed from seismic tomography are accouted for. The inferred source is at 5.2 km depth but cannot be interpreted as a simple pressurized cavity. Moreover, if mass conservation is accounted for, magma emplaced within a shallow source must come from a (generally deeper) reservoir, which is usually assumed to be deep enough to be simply neglected. At Campi Flegrei, seismic
PT-symmetric deformations of integrable models.
Fring, Andreas
2013-04-28
We review recent results on new physical models constructed as PT-symmetrical deformations or extensions of different types of integrable models. We present non-Hermitian versions of quantum spin chains, multi-particle systems of Calogero-Moser-Sutherland type and nonlinear integrable field equations of Korteweg-de Vries type. The quantum spin chain discussed is related to the first example in the series of the non-unitary models of minimal conformal field theories. For the Calogero-Moser-Sutherland models, we provide three alternative deformations: a complex extension for models related to all types of Coxeter/Weyl groups; models describing the evolution of poles in constrained real-valued field equations of nonlinear integrable systems; and genuine deformations based on antilinearly invariant deformed root systems. Deformations of complex nonlinear integrable field equations of Korteweg-de Vries type are studied with regard to different kinds of PT-symmetrical scenarios. A reduction to simple complex quantum mechanical models currently under discussion is presented.
A Geometric Model for the Dynamics of Microchannel Emulsification
Zwan, van der E.A.; Schroën, C.G.P.H.; Boom, R.M.
2009-01-01
Microchannel emulsification is an interfacial tension driven method to produce monodisperse microdroplets, or microspheres. In this paper we introduce a model for describing the dynamics of microchannel emulsification based on simple time dependent geometric shape analysis. The model is based on mec
A geometric representation for the Proca model
Camacaro, J; Leal, L C; Camacaro, Jaime; Gaitan, Rolando; Leal, Lorenzo
1996-01-01
The Proca model is quantized in an open-path dependent representation that generalizes the Loop Representation of gauge theories. The starting point is a gauge invariant Lagrangian that reduces to the Proca Lagrangian when certain gauge is selected.
Deformable surface modeling based on dual subdivision
Institute of Scientific and Technical Information of China (English)
WANG Huawei; SUN Hanqiu; QIN Kaihuai
2005-01-01
Based on dual Doo-Sabin subdivision and the corresponding parameterization, a modeling technique of deformable surfaces is presented in this paper. In the proposed model, all the dynamic parameters are computed in a unified way for both non-defective and defective subdivision matrices, and central differences are used to discretize the Lagrangian dynamics equation instead of backward differences. Moreover, a local scheme is developed to solve the dynamics equation approximately, thus the order of the linear equation is reduced greatly. Therefore, the proposed model is more efficient and faster than the existing dynamic models. It can be used for deformable surface design, interactive surface editing, medical imaging and simulation.
Geometric Reid's recipe for dimer models
Bocklandt, R.; Craw, A.; Quintero Vélez, A.
2015-01-01
Crepant resolutions of three-dimensional toric Gorenstein singularities are derived equivalent to noncommutative algebras arising from consistent dimer models. By choosing a special stability parameter and hence a distinguished crepant resolution Y, this derived equivalence generalises the Fourier-M
Fuzzy Clustering Using the Convex Hull as Geometrical Model
Directory of Open Access Journals (Sweden)
Luca Liparulo
2015-01-01
Full Text Available A new approach to fuzzy clustering is proposed in this paper. It aims to relax some constraints imposed by known algorithms using a generalized geometrical model for clusters that is based on the convex hull computation. A method is also proposed in order to determine suitable membership functions and hence to represent fuzzy clusters based on the adopted geometrical model. The convex hull is not only used at the end of clustering analysis for the geometric data interpretation but also used during the fuzzy data partitioning within an online sequential procedure in order to calculate the membership function. Consequently, a pure fuzzy clustering algorithm is obtained where clusters are fitted to the data distribution by means of the fuzzy membership of patterns to each cluster. The numerical results reported in the paper show the validity and the efficacy of the proposed approach with respect to other well-known clustering algorithms.
GEOMETRIC METHOD OF SEQUENTIAL ESTIMATION RELATED TO MULTINOMIAL DISTRIBUTION MODELS
Institute of Scientific and Technical Information of China (English)
WEIBOCHENG; LISHOUYE
1995-01-01
In 1980's differential geometric methods are successfully used to study curved expomential families and normal nonlinear regression models.This paper presents a new geometric structure to study multinomial distribution models which contain a set of nonlinear parameters.Based on this geometric structure,the suthors study several asymptotic properties for sequential estimation.The bias,the variance and the information loss of the sequential estimates are given from geomentric viewpoint,and a limit theorem connected with the observed and expected Fisher information is obtained in terms of curvatvre measures.The results show that the sequential estimation procednce has some better properties which are generally impossible for nonsequential estimation procedures.
Geometric Reid's recipe for dimer models
Bocklandt, Raf; Velez, Alexander Quintero
2013-01-01
Crepant resolutions of three-dimensional toric Gorenstein singularities are derived equivalent to noncommutative algebras arising from consistent dimer models. By choosing a special stability parameter and hence a distinguished crepant resolution $Y$, this derived equivalence generalises the Fourier-Mukai transform relating the $G$-Hilbert scheme and the skew group algebra $\\CC[x,y,z]\\ast G$ for a finite abelian subgroup of $\\SL(3,\\CC)$. We show that this equivalence sends the vertex simples to pure sheaves, except for the zero vertex which is mapped to the dualising complex of the compact exceptional locus. This generalises results of Cautis-Logvinenko and Cautis-Craw-Logvinenko to the dimer setting, though our approach is different in each case. We also describe some of these pure sheaves explicitly and compute the support of the remainder, providing a dimer model analogue of results from Logvinenko.
Variations of Shape in Industrial Geometric Models
Veelo, Bastiaan Niels
2004-01-01
This thesis presents an approach to free-form surface manipulations, which conceptually improves an existing CAD system that constructs surfaces by smoothly interpolating a network of intersecting curves. There are no regularity requirements on the network, which already yields superior modelling capabilities compared to systems that are based on industry-standard NURBS surfaces. Originally, the shape of such a surface can be modified only locally by manipulating a curve in the network. In t...
DEFF Research Database (Denmark)
Ottosson, Wiviann; Lykkegaard Andersen, J. A.; Borrisova, S.
2014-01-01
Respiration and anatomical variation during radiotherapy (RT) of lung cancer yield dosimetric uncertainties of the delivered dose, possibly affecting the clinical outcome if not corrected for. Adaptive radiotherapy (ART), based on deformable image registration (DIR) and Deep-Inspiration-Breath-Ho......Respiration and anatomical variation during radiotherapy (RT) of lung cancer yield dosimetric uncertainties of the delivered dose, possibly affecting the clinical outcome if not corrected for. Adaptive radiotherapy (ART), based on deformable image registration (DIR) and Deep....... Delineations of anatomical structures were performed on each image set. The CT images were retrospective rigidly and deformable registered to all obtained images using the Varian Smart Adapt v. 11.0. The registered images were analysed for volume change and Dice Similarity Coefficient (DSC). Result...
A Robust Geometric Model for Argument Classification
Giannone, Cristina; Croce, Danilo; Basili, Roberto; de Cao, Diego
Argument classification is the task of assigning semantic roles to syntactic structures in natural language sentences. Supervised learning techniques for frame semantics have been recently shown to benefit from rich sets of syntactic features. However argument classification is also highly dependent on the semantics of the involved lexicals. Empirical studies have shown that domain dependence of lexical information causes large performance drops in outside domain tests. In this paper a distributional approach is proposed to improve the robustness of the learning model against out-of-domain lexical phenomena.
Geometric accuracy of wax bade models manufactured in silicon moulds
Directory of Open Access Journals (Sweden)
G. Budzik
2010-01-01
Full Text Available The article presents the test results of the geometric accuracy of wax blade models manufactured in silicon moulds in the Rapid Tooling process, with the application of the Vacuum Casting technology. In batch production casting waxes are designed for the manufacture of models and components of model sets through injection into a metal die. The objective of the tests was to determine the possibility of using traditional wax for the production of casting models in the rapid prototyping process. Blade models made of five types of casting wax were measured. The definition of the geometric accuracy of wax blade models makes it possible to introduce individual modifications aimed at improving their shape in order to increase the dimensional accuracy of blade models manufactured in the rapid prototyping process.
Multiscale geometric modeling of macromolecules I: Cartesian representation.
Xia, Kelin; Feng, Xin; Chen, Zhan; Tong, Yiying; Wei, Guo Wei
2014-01-01
This paper focuses on the geometric modeling and computational algorithm development of biomolecular structures from two data sources: Protein Data Bank (PDB) and Electron Microscopy Data Bank (EMDB) in the Eulerian (or Cartesian) representation. Molecular surface (MS) contains non-smooth geometric singularities, such as cusps, tips and self-intersecting facets, which often lead to computational instabilities in molecular simulations, and violate the physical principle of surface free energy minimization. Variational multiscale surface definitions are proposed based on geometric flows and solvation analysis of biomolecular systems. Our approach leads to geometric and potential driven Laplace-Beltrami flows for biomolecular surface evolution and formation. The resulting surfaces are free of geometric singularities and minimize the total free energy of the biomolecular system. High order partial differential equation (PDE)-based nonlinear filters are employed for EMDB data processing. We show the efficacy of this approach in feature-preserving noise reduction. After the construction of protein multiresolution surfaces, we explore the analysis and characterization of surface morphology by using a variety of curvature definitions. Apart from the classical Gaussian curvature and mean curvature, maximum curvature, minimum curvature, shape index, and curvedness are also applied to macromolecular surface analysis for the first time. Our curvature analysis is uniquely coupled to the analysis of electrostatic surface potential, which is a by-product of our variational multiscale solvation models. As an expository investigation, we particularly emphasize the numerical algorithms and computational protocols for practical applications of the above multiscale geometric models. Such information may otherwise be scattered over the vast literature on this topic. Based on the curvature and electrostatic analysis from our multiresolution surfaces, we introduce a new concept, the
Modelling deformation and fracture in confectionery wafers
Energy Technology Data Exchange (ETDEWEB)
Mohammed, Idris K.; Charalambides, Maria N.; Williams, J. Gordon; Rasburn, John [Mechanical Engineering Department, Imperial College London, South Kensington, London, SW7 2AZ, United Kingdom and Nestec York Ltd., Nestlé Product Technology Centre, Haxby Road, PO Box 204, York YO91 1XY (United Kingdom)
2015-01-22
The aim of this research is to model the deformation and fracture behaviour of brittle wafers often used in chocolate confectionary products. Three point bending and compression experiments were performed on beam and circular disc samples respectively to determine the 'apparent' stress-strain curves in bending and compression. The deformation of the wafer for both these testing types was observed in-situ within an SEM. The wafer is modeled analytically and numerically as a composite material with a core which is more porous than the skins. X-ray tomography was used to generate a three dimensional volume of the wafer microstructure which was then meshed and used for quantitative analysis. A linear elastic material model, with a damage function and element deletion, was used and the XMT generated architecture was loaded in compression. The output from the FE simulations correlates closely to the load-deflection deformation observed experimentally.
Realistic face modeling based on multiple deformations
Institute of Scientific and Technical Information of China (English)
GONG Xun; WANG Guo-yin
2007-01-01
On the basis of the assumption that the human face belongs to a linear class, a multiple-deformation model is proposed to recover face shape from a few points on a single 2D image. Compared to the conventional methods, this study has the following advantages. First, the proposed modified 3D sparse deforming model is a noniterative approach that can compute global translation efficiently and accurately. Subsequently, the overfitting problem can be alleviated based on the proposed multiple deformation model. Finally, by keeping the main features, the texture generated is realistic. The comparison results show that this novel method outperforms the existing methods by using ground truth data and that realistic 3D faces can be recovered efficiently from a single photograph.
Modelling deformation and fracture in confectionery wafers
Mohammed, Idris K.; Charalambides, Maria N.; Williams, J. Gordon; Rasburn, John
2015-01-01
The aim of this research is to model the deformation and fracture behaviour of brittle wafers often used in chocolate confectionary products. Three point bending and compression experiments were performed on beam and circular disc samples respectively to determine the 'apparent' stress-strain curves in bending and compression. The deformation of the wafer for both these testing types was observed in-situ within an SEM. The wafer is modeled analytically and numerically as a composite material with a core which is more porous than the skins. X-ray tomography was used to generate a three dimensional volume of the wafer microstructure which was then meshed and used for quantitative analysis. A linear elastic material model, with a damage function and element deletion, was used and the XMT generated architecture was loaded in compression. The output from the FE simulations correlates closely to the load-deflection deformation observed experimentally.
A model for geometric and mechanical adaptation of arteries to sustained hypertension.
Rachev, A; Stergiopulos, N; Meister, J J
1998-02-01
This study aimed to model phenomenologically the dynamics of arterial wall remodeling under hypertensive conditions. Sustained hypertension was simulated by a step increase in blood pressure. The arterial wall was considered to be a thick-walled tube made of nonlinear elastic incompressible material. Remodeling rate equations were postulated for the evolution of the geometric dimensions of the hypertensive artery at the zero-stress state, as well as for one of the material constants in the constitutive equations. The driving stimuli for the geometric adaptation are the normalized deviations of wall stresses from their values under normotensive conditions. The geometric dimensions are modulated by the evolution of the deformed inner radius, which serves to restore the level of the flow-induced shear stresses at the arterial endothelium. Mechanical adaptation is driven by the difference between the area compliance under hypertensive and normotensive conditions. The predicted time course of the geometry and mechanical properties of arterial wall are in good qualitative agreement with published experimental findings. The model predicts that the geometric adaptation maintains the stress distribution in arterial wall to its control level, while the mechanical adaptation restores the normal arterial function under induced hypertension.
Duals for classical inventory models via generalized geometric programming
Carlton H. Scott; Thomas R. Jefferson; Soheila Jorjani
2004-01-01
Inventory problems generally have a structure that can be exploited for computational purposes. Here, we look at the duals of two seemingly unrelated inventory models that suggest an interesting duality between discrete time optimal control and optimization over an ordered sequence of variables. Concepts from conjugate duality and generalized geometric programming are used to establish the duality.
Three dimensional geometric modeling of processing-tomatoes
Characterizing tomato geometries with different shapes and sizes would facilitate the design of tomato processing equipments and promote computer-based engineering simulations. This research sought to develop a three-dimensional geometric model that can describe the morphological attributes of proce...
AUTOMATIC MESH GENERATION OF 3-D GEOMETRIC MODELS
Institute of Scientific and Technical Information of China (English)
刘剑飞
2003-01-01
In this paper the presentation of the ball-packing method is reviewed,and a scheme to generate mesh for complex 3-D geometric models is given,which consists of 4 steps:(1)create nodes in 3-D models by ball-packing method,(2)connect nodes to generate mesh by 3-D Delaunay triangulation,(3)retrieve the boundary of the model after Delaunay triangulation,(4)improve the mesh.
DIGITAL GEOMETRIC MODELLING OF TEETH PROFILE BY USING CAD METHODOLOGY
Directory of Open Access Journals (Sweden)
Krzysztof TWARDOCH
2014-03-01
Full Text Available This article is devoted to the problem of properly defining the spatial model of tooth profile with CAD methodologies. Moved by the problem of the accuracy of the mapping defined curves describing the geometry of the teeth. Particular attention was paid to precise geometric modeling involute tooth profile, which has a significant influence on the process of identifying the mesh stiffness for tests performed on the dynamic phenomena occurring in the gear transmission systems conducted using dynamic models
Comparison and Analysis of Geometric Correction Models of Spaceborne SAR.
Jiang, Weihao; Yu, Anxi; Dong, Zhen; Wang, Qingsong
2016-06-25
Following the development of synthetic aperture radar (SAR), SAR images have become increasingly common. Many researchers have conducted large studies on geolocation models, but little work has been conducted on the available models for the geometric correction of SAR images of different terrain. To address the terrain issue, four different models were compared and are described in this paper: a rigorous range-doppler (RD) model, a rational polynomial coefficients (RPC) model, a revised polynomial (PM) model and an elevation derivation (EDM) model. The results of comparisons of the geolocation capabilities of the models show that a proper model for a SAR image of a specific terrain can be determined. A solution table was obtained to recommend a suitable model for users. Three TerraSAR-X images, two ALOS-PALSAR images and one Envisat-ASAR image were used for the experiment, including flat terrain and mountain terrain SAR images as well as two large area images. Geolocation accuracies of the models for different terrain SAR images were computed and analyzed. The comparisons of the models show that the RD model was accurate but was the least efficient; therefore, it is not the ideal model for real-time implementations. The RPC model is sufficiently accurate and efficient for the geometric correction of SAR images of flat terrain, whose precision is below 0.001 pixels. The EDM model is suitable for the geolocation of SAR images of mountainous terrain, and its precision can reach 0.007 pixels. Although the PM model does not produce results as precise as the other models, its efficiency is excellent and its potential should not be underestimated. With respect to the geometric correction of SAR images over large areas, the EDM model has higher accuracy under one pixel, whereas the RPC model consumes one third of the time of the EDM model.
Comparison and Analysis of Geometric Correction Models of Spaceborne SAR
Directory of Open Access Journals (Sweden)
Weihao Jiang
2016-06-01
Full Text Available Following the development of synthetic aperture radar (SAR, SAR images have become increasingly common. Many researchers have conducted large studies on geolocation models, but little work has been conducted on the available models for the geometric correction of SAR images of different terrain. To address the terrain issue, four different models were compared and are described in this paper: a rigorous range-doppler (RD model, a rational polynomial coefficients (RPC model, a revised polynomial (PM model and an elevation derivation (EDM model. The results of comparisons of the geolocation capabilities of the models show that a proper model for a SAR image of a specific terrain can be determined. A solution table was obtained to recommend a suitable model for users. Three TerraSAR-X images, two ALOS-PALSAR images and one Envisat-ASAR image were used for the experiment, including flat terrain and mountain terrain SAR images as well as two large area images. Geolocation accuracies of the models for different terrain SAR images were computed and analyzed. The comparisons of the models show that the RD model was accurate but was the least efficient; therefore, it is not the ideal model for real-time implementations. The RPC model is sufficiently accurate and efficient for the geometric correction of SAR images of flat terrain, whose precision is below 0.001 pixels. The EDM model is suitable for the geolocation of SAR images of mountainous terrain, and its precision can reach 0.007 pixels. Although the PM model does not produce results as precise as the other models, its efficiency is excellent and its potential should not be underestimated. With respect to the geometric correction of SAR images over large areas, the EDM model has higher accuracy under one pixel, whereas the RPC model consumes one third of the time of the EDM model.
An Efficient Virtual Trachea Deformation Model
Directory of Open Access Journals (Sweden)
Cui Tong
2016-01-01
Full Text Available In this paper, we present a virtual tactile model with the physically based skeleton to simulate force and deformation between a rigid tool and the soft organ. When the virtual trachea is handled, a skeleton model suitable for interactive environments is established, which consists of ligament layers, cartilage rings and muscular bars. In this skeleton, the contact force goes through the ligament layer, and produces the load effects of the joints , which are connecting the ligament layer and cartilage rings. Due to the nonlinear shape deformation inside the local neighbourhood of a contact region, the RBF method is applied to modify the result of linear global shape deformation by adding the nonlinear effect inside. Users are able to handle the virtual trachea, and the results from the examples with the mechanical properties of the human trachea are given to demonstrate the effectiveness of the approach.
Cracking and Deformation Modelling of Tensile RC Members Using Stress Transfer Approach
Directory of Open Access Journals (Sweden)
Ronaldas Jakubovskis
2016-12-01
Full Text Available The paper presents a modeling technique for bond, cracking and deformation analysis of RC members. The proposed mod-eling technique is not restricted by the geometrical dimensions of the analyzed member and may be applied for various load-ing conditions. Tensile as well as bending RC members may be analyzed using the proposed technique. Adequacy of the modeling strategy was evaluated by the developed numerical discrete crack algorithm, which allows modeling deformation and cracking behavior of tensile RC members. Comparison of experimental and numerical results proved the applicability of the proposed modeling strategy.
Numerical Modeling of Subglacial Sediment Deformation
DEFF Research Database (Denmark)
Damsgaard, Anders
2015-01-01
incompatible with commonly accepted till rheology models. Variation in pore-water pressure proves to cause reorganization in the internal stress network and leads to slow creeping deformation. The rate of creep is non-linearly dependent on the applied stresses. Granular creep can explain slow glacial...
Geometric Modeling and Reasoning of Human-Centered Freeform Products
Wang, Charlie C L
2013-01-01
The recent trend in user-customized product design requires the shape of products to be automatically adjusted according to the human body’s shape, so that people will feel more comfortable when wearing these products. Geometric approaches can be used to design the freeform shape of products worn by people, which can greatly improve the efficiency of design processes in various industries involving customized products (e.g., garment design, toy design, jewel design, shoe design, and design of medical devices, etc.). These products are usually composed of very complex geometric shapes (represented by free-form surfaces), and are not driven by a parameter table but a digital human model with free-form shapes or part of human bodies (e.g., wrist, foot, and head models). Geometric Modeling and Reasoning of Human-Centered Freeform Products introduces the algorithms of human body reconstruction, freeform product modeling, constraining and reconstructing freeform products, and shape optimization for improving...
A Physical – Geometrical Model of an Early Universe
Directory of Open Access Journals (Sweden)
Corneliu BERBENTE
2014-12-01
Full Text Available A physical-geometrical model for a possible early universe is proposed. One considers an initial singularity containing the energy of the whole universe. The singularity expands as a spherical wave at the speed of light generating space and time. The relations of the special theory of relativity, quantum mechanics and gas kinetics are considered applicable. A structuring of the primary wave is adopted on reasons of geometrical simplicity as well as on satisfying the conservation laws. The evolution is able to lead to particles very close to neutrons as mass and radius. The actually admitted values for the radius and mass of the universe as well as the temperature of the ground radiation (3-5 K can be obtained by using the proposed model.
Image-Based Geometric Modeling and Mesh Generation
2013-01-01
As a new interdisciplinary research area, “image-based geometric modeling and mesh generation” integrates image processing, geometric modeling and mesh generation with finite element method (FEM) to solve problems in computational biomedicine, materials sciences and engineering. It is well known that FEM is currently well-developed and efficient, but mesh generation for complex geometries (e.g., the human body) still takes about 80% of the total analysis time and is the major obstacle to reduce the total computation time. It is mainly because none of the traditional approaches is sufficient to effectively construct finite element meshes for arbitrarily complicated domains, and generally a great deal of manual interaction is involved in mesh generation. This contributed volume, the first for such an interdisciplinary topic, collects the latest research by experts in this area. These papers cover a broad range of topics, including medical imaging, image alignment and segmentation, image-to-mesh conversion,...
Geometrical model fitting for interferometric data: GEM-FIND
Klotz, D; Paladini, C; Hron, J; Wachter, G
2012-01-01
We developed the tool GEM-FIND that allows to constrain the morphology and brightness distribution of objects. The software fits geometrical models to spectrally dispersed interferometric visibility measurements in the N-band using the Levenberg-Marquardt minimization method. Each geometrical model describes the brightness distribution of the object in the Fourier space using a set of wavelength-independent and/or wavelength-dependent parameters. In this contribution we numerically analyze the stability of our nonlinear fitting approach by applying it to sets of synthetic visibilities with statistically applied errors, answering the following questions: How stable is the parameter determination with respect to (i) the number of uv-points, (ii) the distribution of points in the uv-plane, (iii) the noise level of the observations?
A Dynamical model for non-geometric quantum black holes
Spallucci, Euro
2016-01-01
It has been recently proposed that quantum black holes can be described as N-graviton Bose-Einstein condensates. In this picture the quantum properties of BHs "... can be understood in terms of the single number N". However, so far, the dynamical origin of the occupational number N has not been specified. This description is alternative to the usual one, where black holes are believed to be well described geometrically even at the quantum level. In this paper we pursue the former point of view and develop a non-geometrical dynamical model of quantum black holes (BHs). In our model the occupational number N is proportional to the principal quantum number n of a Planckian harmonic oscillator. The so-called "classicalization" corresponds to the large-n limit, where the Schwarzschild horizon is recovered.
Time evolution in a geometric model of a particle
Atiyah, Michael; Schroers, Bernd
2014-01-01
We analyse the properties of a (4+1)-dimensional Ricci-flat spacetime which may be viewed as an evolving Taub-NUT geometry, and give exact solutions of the Maxwell and gauged Dirac equation on this background. We interpret these solutions in terms of a geometric model of the electron and its spin, and discuss links between the resulting picture and Dirac's Large Number Hypothesis.
A simulation model for analysing brain structure deformations
Energy Technology Data Exchange (ETDEWEB)
Bona, Sergio Di [Institute for Information Science and Technologies, Italian National Research Council (ISTI-8211-CNR), Via G Moruzzi, 1-56124 Pisa (Italy); Lutzemberger, Ludovico [Department of Neuroscience, Institute of Neurosurgery, University of Pisa, Via Roma, 67-56100 Pisa (Italy); Salvetti, Ovidio [Institute for Information Science and Technologies, Italian National Research Council (ISTI-8211-CNR), Via G Moruzzi, 1-56124 Pisa (Italy)
2003-12-21
Recent developments of medical software applications from the simulation to the planning of surgical operations have revealed the need for modelling human tissues and organs, not only from a geometric point of view but also from a physical one, i.e. soft tissues, rigid body, viscoelasticity, etc. This has given rise to the term 'deformable objects', which refers to objects with a morphology, a physical and a mechanical behaviour of their own and that reflects their natural properties. In this paper, we propose a model, based upon physical laws, suitable for the realistic manipulation of geometric reconstructions of volumetric data taken from MR and CT scans. In particular, a physically based model of the brain is presented that is able to simulate the evolution of different nature pathological intra-cranial phenomena such as haemorrhages, neoplasm, haematoma, etc and to describe the consequences that are caused by their volume expansions and the influences they have on the anatomical and neuro-functional structures of the brain.
Constitutive model with time-dependent deformations
DEFF Research Database (Denmark)
Krogsbøll, Anette
1998-01-01
are common in time as well as size. This problem is adressed by means of a new constitutive model for soils. It is able to describe the behavior of soils at different deformation rates. The model defines time-dependent and stress-related deformations separately. They are related to each other and they occur......In many geological and Engineering problems it is necessary to transform information from one scale to another. Data collected at laboratory scale are often used to evaluate field problems on a much larger scale. This is certainly true for geological problems where extreme scale differences...... simultanelously. The model is based on concepts from elasticity and viscoplasticity theories. In addition to Hooke's law for the elastic behavior, the framework for the viscoplastic behavior consists, in the general case (two-dimensional or three-dimensional), of a yield surface, an associated flow rule...
Geometric Assortative Growth Model for Small-World Networks
Directory of Open Access Journals (Sweden)
Yilun Shang
2014-01-01
Full Text Available It has been shown that both humanly constructed and natural networks are often characterized by small-world phenomenon and assortative mixing. In this paper, we propose a geometrically growing model for small-world networks. The model displays both tunable small-world phenomenon and tunable assortativity. We obtain analytical solutions of relevant topological properties such as order, size, degree distribution, degree correlation, clustering, transitivity, and diameter. It is also worth noting that the model can be viewed as a generalization for an iterative construction of Farey graphs.
Geometric assortative growth model for small-world networks.
Shang, Yilun
2014-01-01
It has been shown that both humanly constructed and natural networks are often characterized by small-world phenomenon and assortative mixing. In this paper, we propose a geometrically growing model for small-world networks. The model displays both tunable small-world phenomenon and tunable assortativity. We obtain analytical solutions of relevant topological properties such as order, size, degree distribution, degree correlation, clustering, transitivity, and diameter. It is also worth noting that the model can be viewed as a generalization for an iterative construction of Farey graphs.
A stochastic large deformation model for computational anatomy
DEFF Research Database (Denmark)
Arnaudon, Alexis; Holm, Darryl D.; Pai, Akshay Sadananda Uppinakudru
2017-01-01
In the study of shapes of human organs using computational anatomy, variations are found to arise from inter-subject anatomical differences, disease-specific effects, and measurement noise. This paper introduces a stochastic model for incorporating random variations into the Large Deformation...... Diffeomorphic Metric Mapping (LDDMM) framework. By accounting for randomness in a particular setup which is crafted to fit the geometrical properties of LDDMM, we formulate the template estimation problem for landmarks with noise and give two methods for efficiently estimating the parameters of the noise fields...... from a prescribed data set. One method directly approximates the time evolution of the variance of each landmark by a finite set of differential equations, and the other is based on an Expectation-Maximisation algorithm. In the second method, the evaluation of the data likelihood is achieved without...
Solving Topological and Geometrical Constraints in Bridge Feature Model
Institute of Scientific and Technical Information of China (English)
PENG Weibing; SONG Liangliang; PAN Guoshuai
2008-01-01
The capacity that computer can solve more complex design problem was gradually increased.Bridge designs need a breakthrough in the current development limitations, and then become more intelli-gent and integrated. This paper proposes a new parametric and feature-based computer aided design (CAD) models which can represent families of bridge objects, includes knowledge representation, three-dimensional geometric topology relationships. The realization of a family member is found by solving first the geometdc constraints, and then the topological constraints. From the geometric solution, constraint equations are constructed. Topology solution is developed by feature dependencies graph between bridge objects. Finally, feature parameters are proposed to drive bridge design with feature parameters. Results from our implementation show that the method can help to facilitate bridge design.
MODELING OF NONLINEAR DEFORMATION AND BUCKLING OF ELASTIC INHOMOGENEOUS SHELLS
Directory of Open Access Journals (Sweden)
Bazhenov V.A.
2014-06-01
Full Text Available The paper outlines the fundamentals of the method of solving static problems of geometrically nonlinear deformation, buckling, and postbuckling behavior of thin thermoelastic inhomogeneous shells with complex-shaped mid-surface, geometrical features throughout the thickness, and multilayer structure under complex thermomechanical loading. The method is based on the geometrically nonlinear equations of three-dimensional thermoelasticity and the moment finiteelement scheme. The method is justified numerically. Comparing solutions with those obtained by other authors and by software LIRA and SCAD is conducted.
DEFF Research Database (Denmark)
Eiland, R B; Maare, Christian; Sjöström, D
2014-01-01
The aim of this study was to carry out geometric and dosimetric evaluation of the usefulness of a deformable image registration algorithm utilized for adaptive head-and-neck intensity-modulated radiotherapy. Data consisted of seven patients, each with a planning CT (pCT), a rescanning CT (Re...
Scale Problems in Geometric-Kinematic Modelling of Geological Objects
Siehl, Agemar; Thomsen, Andreas
To reveal, to render and to handle complex geological objects and their history of structural development, appropriate geometric models have to be designed. Geological maps, sections, sketches of strain and stress patterns are such well-known analogous two-dimensional models. Normally, the set of observations and measurements supporting them is small in relation to the complexity of the real objects they derive from. Therefore, modelling needs guidance by additional expert knowledge to bridge empty spaces which are not supported by data. Generating digital models of geological objects has some substantial advantages compared to conventional methods, especially if they are supported by an efficient database management system. Consistent 3D models of some complexity can be created, and experiments with time-dependent geological geometries may help to restore coherent sequences of paleogeological states. In order to cope with the problems arising from the combined usage of 3D-geometry models of different scale and resolution within an information system on subsurface geology, geometrical objects need to be annotated with information on the context, within which the geometry model has been established and within which it is valid, and methods supporting storage and retrieval as well as manipulation of geometry at different scales must also take into account and handle such context information to achieve meaningful results. An example is given of a detailed structural study of an open pit lignite mine in the Lower Rhine Basin.
Protaziuk, Elżbieta
2016-06-01
Satellite measurements become competitive in many tasks of engineering surveys, however, in many requiring applications possibilities to apply such solutions are still limited. The possibility to widely apply satellite technologies for displacements measurements is related with new challenges; the most important of them relate to increasing requirements concerning the accuracy, reliability and continuity of results of position determination. One of the solutions is a ground augmentation of satellite network, which intention is to improve precision of positioning, ensure comparable accuracy of coordinates and reduce precision fluctuations over time. The need for augmentation of GNSS is particularly significant in situations: where the visibility of satellites is poor because of terrain obstacles, when the determined position is not precise enough or a satellites constellation does not allow for reliable positioning. Ground based source/sources of satellite signal placed at a ground, called pseudosatellites, or pseudolites were intensively investigated during the last two decades and finally were developed into groundbased, time-synchronized transceivers, that can transmit and receive a proprietary positioning signal. The paper presents geometric aspects of the ground based augmentation of the satellite networks using various quality measures of positioning geometry, which depends on access to the constellation of satellites and the conditions of the observation environment. The issue of minimizing these measures is the key problem that allows to obtain the position with high accuracy. For this purpose, the use of an error ellipsoid is proposed and compared with an error ellipse. The paper also describes the results of preliminary accuracy analysis obtained at test area and a comparison of various measures of the quality of positioning geometry.
Do Lumped-Parameter Models Provide the Correct Geometrical Damping?
DEFF Research Database (Denmark)
Andersen, Lars
This paper concerns the formulation of lumped-parameter models for rigid footings on homogenous or stratified soil. Such models only contain a few degrees of freedom, which makes them ideal for inclusion in aero-elastic codes for wind turbines and other models applied to fast evaluation of struct......This paper concerns the formulation of lumped-parameter models for rigid footings on homogenous or stratified soil. Such models only contain a few degrees of freedom, which makes them ideal for inclusion in aero-elastic codes for wind turbines and other models applied to fast evaluation...... response during excitation and the geometrical damping related to free vibrations of a hexagonal footing. The optimal order of a lumped-parameter model is determined for each degree of freedom, i.e. horizontal and vertical translation as well as torsion and rocking. In particular, the necessity of coupling...... between horizontal sliding and rocking is discussed....
Model on surface borehole squeezing deformation fracture*
Institute of Scientific and Technical Information of China (English)
SUN Hai-tao; HU Qian-ting; HUANG Sheng-shu
2009-01-01
As a good method to solve the problem of high methane on the workface and in the goaf, drawing coal strata methane through a surface borehole is used. However, the excavation affected the overlying rock strata greatly. When the excavation face passed through the surface borehole position, the surface borehole fractures fast. This problem was seriously related to the unformed squeeze effect. Therefore, a squeezing deformation fracture model based on the rock strata squeezing effect was set up. At the same time, a 3DEC simulation model is presented to confirm the theory. The result shows that the mod-el is reliable and has a good engineering application value.
Discrete element modeling of subglacial sediment deformation
DEFF Research Database (Denmark)
Damsgaard, Anders; Egholm, David L.; Piotrowski, Jan A.
2013-01-01
-shear experiments on simple granular materials are compared to results from similar numerical experiments. The simulated DEM material and all tested laboratory materials deform by an elasto-plastic rheology under the applied effective normal stress. These results demonstrate that the DEM is a viable alternative...... on the level of normal (overburden) stress, and we show how high normal stress can mobilize material to great depths. The particle rotational axes tend to align with progressive shear strain, with rotations both along and reverse to the shear direction. The results from successive laboratory ring...... to continuum models for small-scale analysis of sediment deformation. It can be used to simulate the macromechanical behavior of simple granular sediments, and it provides an opportunity to study how microstructures in subglacial sediments are formed during progressive shear strain....
Energy Technology Data Exchange (ETDEWEB)
Cornu, T.
2001-01-01
The present work deals with three-dimensional deformation of sedimentary basins. The main goal of the work was to propose new ways to study tectonic deformation and to insert it into basin-modeling environment for hydrocarbon migration applications. To handle the complexity of the deformation, the model uses kinematic laws, a discrete approach, and the construction of a code that allows the greatest diversity in the deformation mechanisms we can take into account. The 3-D-volume deformation is obtained through the calculation of the behavior of the neutral surface of each basin layer. The main idea is to deform the neutral surface of each layer with the help of geometrical laws and to use the result to rebuild the volume deformation of the basin. The constitutive algorithm includes three characteristic features. The first one deals with the mathematical operator we use to describe the flexural-slip mechanism which is a combination of the translation of the neutral surface nodes and the rotation of the vertical edges attached to these nodes. This performs the reversibility that was required for the basin modeling. The second one is about. the use of a discrete approach, which gives a better description of the global deformation and offers to locally control volume evolutions. The knowledge of volume variations can become a powerful tool in structural geology analysis and the perfect complement for a field study. The last one concerns the modularity of the developed code. Indeed, the proposed model uses three main mechanisms of deformation. But the architecture of the code allows the insertion of new mechanisms or a better interaction between them. The model has been validated first with 2-D cases, then with 3-D natural cases. They give good results from a qualitative point of view. They also show the capacity of the model to provide a deformation path that is geologically acceptable, and its ability to control the volume variations of the basin through the
Poisson sigma models and deformation quantization
Cattaneo, A S; Cattaneo, Alberto S.; Felder, Giovanni
2001-01-01
This is a review aimed at a physics audience on the relation between Poisson sigma models on surfaces with boundary and deformation quantization. These models are topological open string theories. In the classical Hamiltonian approach, we describe the reduced phase space and its structures (symplectic groupoid), explaining in particular the classical origin of the non-commutativity of the string end-point coordinates. We also review the perturbative Lagrangian approach and its connection with Kontsevich's star product. Finally we comment on the relation between the two approaches.
High-fidelity geometric modeling for biomedical applications
Energy Technology Data Exchange (ETDEWEB)
Yu, Zeyun [Univ. of California, San Diego, CA (United States). Dept. of Mathematics; Holst, Michael J. [Univ. of California, San Diego, CA (United States). Dept. of Mathematics; Andrew McCammon, J. [Univ. of California, San Diego, CA (United States). Dept. of Chemistry and Biochemistry; Univ. of California, San Diego, CA (United States). Dept. of Pharmacology
2008-05-19
In this paper, we describe a combination of algorithms for high-fidelity geometric modeling and mesh generation. Although our methods and implementations are application-neutral, our primary target application is multiscale biomedical models that range in scales across the molecular, cellular, and organ levels. Our software toolchain implementing these algorithms is general in the sense that it can take as input a molecule in PDB/PQR forms, a 3D scalar volume, or a user-defined triangular surface mesh that may have very low quality. The main goal of our work presented is to generate high quality and smooth surface triangulations from the aforementioned inputs, and to reduce the mesh sizes by mesh coarsening. Tetrahedral meshes are also generated for finite element analysis in biomedical applications. Experiments on a number of bio-structures are demonstrated, showing that our approach possesses several desirable properties: feature-preservation, local adaptivity, high quality, and smoothness (for surface meshes). Finally, the availability of this software toolchain will give researchers in computational biomedicine and other modeling areas access to higher-fidelity geometric models.
An integrated introduction to computer graphics and geometric modeling
Goldman, Ronald
2009-01-01
… this book may be the first book on geometric modelling that also covers computer graphics. In addition, it may be the first book on computer graphics that integrates a thorough introduction to 'freedom' curves and surfaces and to the mathematical foundations for computer graphics. … the book is well suited for an undergraduate course. … The entire book is very well presented and obviously written by a distinguished and creative researcher and educator. It certainly is a textbook I would recommend. …-Computer-Aided Design, 42, 2010… Many books concentrate on computer programming and soon beco
A geometric model for Hochschild homology of Soergel bimodules
DEFF Research Database (Denmark)
Webster, Ben; Williamson, Geordie
2008-01-01
An important step in the calculation of the triply graded link homology of Khovanov and Rozansky is the determination of the Hochschild homology of Soergel bimodules for SL(n). We present a geometric model for this Hochschild homology for any simple group G, as B–equivariant intersection cohomology...... of B×B–orbit closures in G. We show that, in type A, these orbit closures are equivariantly formal for the conjugation B–action. We use this fact to show that, in the case where the corresponding orbit closure is smooth, this Hochschild homology is an exterior algebra over a polynomial ring...
Integrable deformations of T-dual $\\sigma$ models
Borsato, Riccardo
2016-01-01
We present a method to deform (generically non-abelian) T duals of two-dimensional $\\sigma$ models, which preserves classical integrability. The deformed models are identified by a linear operator $\\omega$ on the dualised subalgebra, which satisfies the 2-cocycle condition. We prove that the so-called homogeneous Yang-Baxter deformations are equivalent, via a field redefinition, to our deformed models when $\\omega$ is invertible. We explain the details for deformations of T duals of Principal Chiral Models, and present the corresponding generalisation to the case of supercoset models.
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Shen, Z; Greskovich, J; Xia, P [The Cleveland Clinic, Cleveland, OH (United States); Bzdusek, K [Philips, Fitchburg, WI (United States)
2015-06-15
Purpose: To generate virtual phantoms with clinically relevant deformation and use them to objectively evaluate geometric and dosimetric uncertainties of deformable image registration (DIR) algorithms. Methods: Ten lung cancer patients undergoing adaptive 3DCRT planning were selected. For each patient, a pair of planning CT (pCT) and replanning CT (rCT) were used as the basis for virtual phantom generation. Manually adjusted meshes were created for selected ROIs (e.g. PTV, lungs, spinal cord, esophagus, and heart) on pCT and rCT. The mesh vertices were input into a thin-plate spline algorithm to generate a reference displacement vector field (DVF). The reference DVF was used to deform pCT to generate a simulated replanning CT (srCT) that was closely matched to rCT. Three DIR algorithms (Demons, B-Spline, and intensity-based) were applied to these ten virtual phantoms. The images, ROIs, and doses were mapped from pCT to srCT using the DVFs computed by these three DIRs and compared to those mapped using the reference DVF. Results: The average Dice coefficients for selected ROIs were from 0.85 to 0.96 for Demons, from 0.86 to 0.97 for intensity-based, and from 0.76 to 0.95 for B-Spline. The average Hausdorff distances for selected ROIs were from 2.2 to 5.4 mm for Demons, from 2.3 to 6.8 mm for intensity-based, and from 2.4 to 11.4 mm for B-Spline. The average absolute dose errors for selected ROIs were from 0.2 to 0.6 Gy for Demons, from 0.1 to 0.5 Gy for intensity-based, and from 0.5 to 1.5 Gy for B-Spline. Conclusion: Virtual phantoms were modeled after patients with lung cancer and were clinically relevant for adaptive radiotherapy treatment replanning. Virtual phantoms with known DVFs serve as references and can provide a fair comparison when evaluating different DIRs. Demons and intensity-based DIRs were shown to have smaller geometric and dosimetric uncertainties than B-Spline. Z Shen: None; K Bzdusek: an employee of Philips Healthcare; J Greskovich: None; P Xia
Formal Relationships Between Geometrical and Classical Models for Concurrency
Goubault, Eric
2010-01-01
A wide variety of models for concurrent programs has been proposed during the past decades, each one focusing on various aspects of computations: trace equivalence, causality between events, conflicts and schedules due to resource accesses, etc. More recently, models with a geometrical flavor have been introduced, based on the notion of cubical set. These models are very rich and expressive since they can represent commutation between any bunch of events, thus generalizing the principle of true concurrency. While they seem to be very promising - because they make possible the use of techniques from algebraic topology in order to study concurrent computations - they have not yet been precisely related to the previous models, and the purpose of this paper is to fill this gap. In particular, we describe an adjunction between Petri nets and cubical sets which extends the previously known adjunction between Petri nets and asynchronous transition systems by Nielsen and Winskel.
Geometric and Textural Blending for 3D Model Stylization.
Huang, YiJheng; Lin, Wen-Chieh; Yeh, I-Cheng; Lee, Tong-Yee
2017-01-25
Stylizing a 3D model with characteristic shapes or appearances is common in product design, particularly in the design of 3D model merchandise, such as souvenirs, toys, furniture, and stylized items. A model stylization approach is proposed in this study. The approach combines base and style models while preserving user-specified shape features of the base model and the attractive features of the style model with limited assistance from a user. The two models are first combined at the topological level. A tree-growing technique is utilized to search for all possible combinations of the two models. Second, the models are combined at textural and geometric levels by employing a morphing technique. Results show that the proposed approach generates various appealing models and allows users to control the diversity of the output models and adjust the blending degree between the base and style models. The results of this work are also experimentally compared with those of a recent work through a user study. The comparison indicates that our results are more appealing, feature-preserving, and reasonable than those of the compared previous study. The proposed system allows product designers to easily explore design possibilities and assists novice users in creating their own stylized models.
Body circumferences: clinical implications emerging from a new geometric model
Directory of Open Access Journals (Sweden)
Gallagher Dympna
2008-10-01
Full Text Available Abstract Background Body volume expands with the positive energy balance associated with the development of adult human obesity and this "growth" is captured by two widely used clinical metrics, waist circumference and body mass index (BMI. Empirical correlations between circumferences, BMI, and related body compartments are frequently reported but fail to provide an important common conceptual foundation that can be related to key clinical observations. A two-phase program was designed to fill this important gap: a geometric model linking body volume with circumferences and BMI was developed and validated in cross-sectional cohorts; and the model was applied to the evaluation of longitudinally monitored subjects during periods of voluntary weight loss. Concepts emerging from the developed model were then used to examine the relations between the evaluated clinical measures and body composition. Methods Two groups of healthy adults (n = 494 and 1499 were included in the cross-sectional model development/testing phase and subjects in two previous weight loss studies were included in the longitudinal model evaluation phase. Five circumferences (arm, waist, hip, thigh, and calf; average of sum, C, height (H, BMI, body volume (V; underwater weighing, and the volumes of major body compartments (whole-body magnetic resonance imaging were measured. Results The evaluation of a humanoid geometric model based a cylinder confirmed that V derived from C and H was highly correlated with measured V [R2 both males and females, 0.97; p 0.5. The scaling of individual circumferences to V/H varied, with waist the highest (V/H~0.6 and calf the lowest (V/H~0.3, indicating that the largest and smallest between-subject "growth" with greater body volume occurs in the abdominal area and lower extremities, respectively. A stepwise linear regression model including all five circumferences2 showed that each contributed independently to V/H. These cross
Hopping electron model with geometrical frustration: kinetic Monte Carlo simulations
Terao, Takamichi
2016-09-01
The hopping electron model on the Kagome lattice was investigated by kinetic Monte Carlo simulations, and the non-equilibrium nature of the system was studied. We have numerically confirmed that aging phenomena are present in the autocorrelation function C ({t,tW )} of the electron system on the Kagome lattice, which is a geometrically frustrated lattice without any disorder. The waiting-time distributions p(τ ) of hopping electrons of the system on Kagome lattice has been also studied. It is confirmed that the profile of p (τ ) obtained at lower temperatures obeys the power-law behavior, which is a characteristic feature of continuous time random walk of electrons. These features were also compared with the characteristics of the Coulomb glass model, used as a model of disordered thin films and doped semiconductors. This work represents an advance in the understanding of the dynamics of geometrically frustrated systems and will serve as a basis for further studies of these physical systems.
Mask roughness induced LER: geometric model at long correlation lengths
Energy Technology Data Exchange (ETDEWEB)
McClinton, Brittany M.; Naulleau, Patrick P.
2011-02-11
Collective understanding of how both the resist and line-edge roughness (LER) on the mask affect the final printed LER has made significant advances. What is poorly understood, however, is the extent to which mask surface roughness couples to image plane LER as a function of illumination conditions, NA, and defocus. Recently, progress has been made in formulating a simplified solution for mask roughness induced LER. Here, we investigate the LER behavior at long correlation lengths of surface roughness on the mask. We find that for correlation lengths greater than 3/NA in wafer dimensions and CDs greater than approximately 0.75/NA, the previously described simplified model, which remains based on physical optics, converges to a 'geometric regime' which is based on ray optics and is independent of partial coherence. In this 'geometric regime', the LER is proportional to the mask slope error as it propagates through focus, and provides a faster alternative to calculating LER in contrast to either full 2D aerial image simulation modeling or the newly proposed physical optics model. Data is presented for both an NA = 0.32 and an NA = 0.5 imaging system for CDs of 22-nm and 50-nm horizontal-line-dense structures.
Budiarto, E.; Keijzer, M.; Storchi, P. R.; Hoogeman, M. S.; Bondar, L.; Mutanga, T. F.; de Boer, H. C. J.; Heemink, A. W.
2011-02-01
Local motions and deformations of organs between treatment fractions introduce geometrical uncertainties into radiotherapy. These uncertainties are generally taken into account in the treatment planning by enlarging the radiation target by a margin around the clinical target volume. However, a practical method to fully include these uncertainties is still lacking. This paper proposes a model based on the principal component analysis to describe the patient-specific local probability distributions of voxel motions so that the average values and variances of the dose distribution can be calculated and fully used later in inverse treatment planning. As usually only a very limited number of data for new patients is available; in this paper the analysis is extended to use population data. A basic assumption (which is justified retrospectively in this paper) is that general movements and deformations of a specific organ are similar despite variations in the shapes of the organ over the population. A proof of principle of the method for deformations of the prostate and the seminal vesicles is presented.
Energy Technology Data Exchange (ETDEWEB)
Budiarto, E; Keijzer, M; Heemink, A W [Delft Institute of Applied Mathematics (DIAM), Technische Universiteit Delft, Mekelweg 4, 2628 CD Delft (Netherlands); Storchi, P R; Hoogeman, M S; Bondar, L; Mutanga, T F [Department of Radiation Oncology, Erasmus MC-Daniel den Hoed Cancer Centre. Groene Hilledijk 301, 3075 EA Rotterdam (Netherlands); De Boer, H C J, E-mail: e.budiarto@tudelft.nl [Department of Radiotherapy, Universitair Medisch Centrum Utrecht, Heidelberglaan 100, 3584 CX Utrecht (Netherlands)
2011-02-21
Local motions and deformations of organs between treatment fractions introduce geometrical uncertainties into radiotherapy. These uncertainties are generally taken into account in the treatment planning by enlarging the radiation target by a margin around the clinical target volume. However, a practical method to fully include these uncertainties is still lacking. This paper proposes a model based on the principal component analysis to describe the patient-specific local probability distributions of voxel motions so that the average values and variances of the dose distribution can be calculated and fully used later in inverse treatment planning. As usually only a very limited number of data for new patients is available; in this paper the analysis is extended to use population data. A basic assumption (which is justified retrospectively in this paper) is that general movements and deformations of a specific organ are similar despite variations in the shapes of the organ over the population. A proof of principle of the method for deformations of the prostate and the seminal vesicles is presented.
A Geometrically Exact Model for Externally Loaded Concentric-Tube Continuum Robots
Rucker, D. Caleb; Jones, Bryan A.; Webster, Robert J.
2011-01-01
Continuum robots, which are composed of multiple concentric, precurved elastic tubes, can provide dexterity at diameters equivalent to standard surgical needles. Recent mechanics-based models of these “active cannulas” are able to accurately describe the curve of the robot in free space, given the preformed tube curves and the linear and angular positions of the tube bases. However, in practical applications, where the active cannula must interact with its environment or apply controlled forces, a model that accounts for deformation under external loading is required. In this paper, we apply geometrically exact rod theory to produce a forward kinematic model that accurately describes large deflections due to a general collection of externally applied point and/or distributed wrench loads. This model accommodates arbitrarily many tubes, with each having a general preshaped curve. It also describes the independent torsional deformation of the individual tubes. Experimental results are provided for both point and distributed loads. Average tip error under load was 2.91 mm (1.5%–3% of total robot length), which is similar to the accuracy of existing free-space models. PMID:21566688
On the geometric modulation of skin lesion growth: a mathematical model for melanoma
Directory of Open Access Journals (Sweden)
Ana Isabel Mendes
Full Text Available Abstract Introduction Early detection of suspicious skin lesions is critical to prevent skin malignancies, particularly the melanoma, which is the most dangerous form of human skin cancer. In the last decade, image processing techniques have been an increasingly important tool for early detection and mathematical models play a relevant role in mapping the progression of lesions. Methods This work presents an algorithm to describe the evolution of the border of the skin lesion based on two main measurable markers: the symmetry and the geometric growth path of the lesion. The proposed methodology involves two dermoscopic images of the same melanocytic lesion obtained at different moments in time. By applying a mathematical model based on planar linear transformations, measurable parameters related to symmetry and growth are extracted. Results With this information one may compare the actual evolution in the lesion with the outcomes from the geometric model. First, this method was tested on predefined images whose growth was controlled and the symmetry known which were used for validation. Then the methodology was tested in real dermoscopic melanoma images in which the parameters of the mathematical model revealed symmetry and growth rates consistent with a typical melanoma behavior. Conclusions The method developed proved to show very accurate information about the target growth markers (variation on the growth along the border, the deformation and the symmetry of the lesion trough the time. All the results, validated by the expected phantom outputs, were similar to the ones on the real images.
Miranda, Alexandre F; Sampaio, Francisco J B
2014-06-01
A surgical approach with plaque incision and graft (PIG) to correct Peyronie's disease is the best method for complex, large deviations. However, the geometric and mechanical consequences of this intervention are poorly understood. The aim of this study was to analyze the geometric and mechanical consequences of PIG on penile straighten surgery. A tridimensional penile simile model with a curvature of 85° was created to test all of the most common PIG techniques. PIG with double-Y, H-shape, and Egydio techniques were used to rectify the curved penile model. The results that differed from a rectified cylinder shape were highlighted. All of the analyzed techniques created a geometric distortion that could be linked to poor surgical results. We suggest a new technique to resolve these abnormalities. Current techniques designed to correct penile deviation using PIG present geometric and mechanical imperfections with potential consequences to the postoperative success rate. The new technique proposed in this report could be a possible solution to solve the geometric distortion caused by PIG. © 2014 International Society for Sexual Medicine.
Implicit modeling of folds and overprinting deformation
Laurent, Gautier; Ailleres, Laurent; Grose, Lachlan; Caumon, Guillaume; Jessell, Mark; Armit, Robin
2016-12-01
Three-dimensional structural modeling is gaining importance for a broad range of quantitative geoscientific applications. However, existing approaches are still limited by the type of structural data they are able to use and by their lack of structural meaning. Most techniques heavily rely on spatial data for modeling folded layers, but are unable to completely use cleavage and lineation information for constraining the shape of modeled folds. This lack of structural control is generally compensated by expert knowledge introduced in the form of additional interpretive data such as cross-sections and maps. With this approach, folds are explicitly designed by the user instead of being derived from data. This makes the resulting structures subjective and deterministic. This paper introduces a numerical framework for modeling folds and associated foliations from typical field data. In this framework, a parametric description of fold geometry is incorporated into the interpolation algorithm. This way the folded geometry is implicitly derived from observed data, while being controlled through structural parameters such as fold wavelength, amplitude and tightness. A fold coordinate system is used to support the numerical description of fold geometry and to modify the behavior of classical structural interpolators. This fold frame is constructed from fold-related structural elements such as axial foliations, intersection lineations, and vergence. Poly-deformed terranes are progressively modeled by successively modeling each folding event going backward through time. The proposed framework introduces a new modeling paradigm, which enables the building of three-dimensional geological models of complex poly-deformed terranes. It follows a process based on the structural geologist approach and is able to produce geomodels that honor both structural data and geological knowledge.
Cox, P G; Fagan, M J; Rayfield, E J; Jeffery, N
2011-12-01
Rodents are defined by a uniquely specialized dentition and a highly complex arrangement of jaw-closing muscles. Finite element analysis (FEA) is an ideal technique to investigate the biomechanical implications of these specializations, but it is essential to understand fully the degree of influence of the different input parameters of the FE model to have confidence in the model's predictions. This study evaluates the sensitivity of FE models of rodent crania to elastic properties of the materials, loading direction, and the location and orientation of the models' constraints. Three FE models were constructed of squirrel, guinea pig and rat skulls. Each was loaded to simulate biting on the incisors, and the first and the third molars, with the angle of the incisal bite varied over a range of 45°. The Young's moduli of the bone and teeth components were varied between limits defined by findings from our own and previously published tests of material properties. Geometric morphometrics (GMM) was used to analyse the resulting skull deformations. Bone stiffness was found to have the strongest influence on the results in all three rodents, followed by bite position, and then bite angle and muscle orientation. Tooth material properties were shown to have little effect on the deformation of the skull. The effect of bite position varied between species, with the mesiodistal position of the biting tooth being most important in squirrels and guinea pigs, whereas bilateral vs. unilateral biting had the greatest influence in rats. A GMM analysis of isolated incisor deformations showed that, for all rodents, bite angle is the most important parameter, followed by elastic properties of the tooth. The results here elucidate which input parameters are most important when defining the FE models, but also provide interesting glimpses of the biomechanical differences between the three skulls, which will be fully explored in future publications. © 2011 The Authors. Journal of
Badawi, Ahmed M.; Weiss, Elisabeth; Sleeman, William C., IV; Hugo, Geoffrey D.
2012-01-01
The purpose of this study is to develop and evaluate a lung tumour interfraction geometric variability classification scheme as a means to guide adaptive radiotherapy and improve measurement of treatment response. Principal component analysis (PCA) was used to generate statistical shape models of the gross tumour volume (GTV) for 12 patients with weekly breath hold CT scans. Each eigenmode of the PCA model was classified as ‘trending’ or ‘non-trending’ depending on whether its contribution to the overall GTV variability included a time trend over the treatment course. Trending eigenmodes were used to reconstruct the original semi-automatically delineated GTVs into a reduced model containing only time trends. Reduced models were compared to the original GTVs by analyzing the reconstruction error in the GTV and position. Both retrospective (all weekly images) and prospective (only the first four weekly images) were evaluated. The average volume difference from the original GTV was 4.3% ± 2.4% for the trending model. The positional variability of the GTV over the treatment course, as measured by the standard deviation of the GTV centroid, was 1.9 ± 1.4 mm for the original GTVs, which was reduced to 1.2 ± 0.6 mm for the trending-only model. In 3/13 cases, the dominant eigenmode changed class between the prospective and retrospective models. The trending-only model preserved GTV and shape relative to the original GTVs, while reducing spurious positional variability. The classification scheme appears feasible for separating types of geometric variability by time trend.
A New Simple Model for the Mushrooming Deformation of Projectile Impacting on A Deformable Target
Institute of Scientific and Technical Information of China (English)
Zhang Xiaoqing; Yang Guitong
2004-01-01
Based on Taylor's model and Hawkyard's model, a new simple model for the mushrooming deformation of projectile impacting on a deformable target is installed considering the penetration of the projectile to the deformable target. In the model, the following time-dependent variables are involved in: the extent and the particle velocity in the rigid zone; the extent, the cross-section area and the particle velocity in plastic zone; the velocity and depth of the penetrating of projectile to the target. Solving the set of equations, analytic solution is given. The profiles of deformed projectile and shape parameters for different initial impact velocities are shown. The duration time of deformation increases with increasing the impact velocity. The analytical results by using this model are coincident with experimental result.
Geometric Model of Topological Insulators from the Maxwell Algebra
Palumbo, Giandomenico
2016-01-01
We propose a novel geometric model of three-dimensional topological insulators in presence of an external electromagnetic field. The gapped boundary of these systems supports relativistic quantum Hall states and is described by a Chern-Simons theory with a gauge connection that takes values in the Maxwell algebra. This represents a non-central extension of the Poincar\\'e algebra and takes into account both the Lorentz and magnetic-translation symmetries of the surface states. In this way, we derive a relativistic version of the Wen-Zee term, and we show that the non-minimal coupling between the background geometry and the electromagnetic field in the model is in agreement with the main properties of the relativistic quantum Hall states in the flat space.
Simulation of a mass-spring model for global deformation
Institute of Scientific and Technical Information of China (English)
Tong CUI; Aiguo SONG; Juan WU
2009-01-01
This article addresses a largely open problem in haptic simulation and rendering:contact force and deformation modeling for haptic simulation of a discrete globe mass-spring model,especially for global deforma-tion.The mass-spring system is composed of nodes connected with radially distributed springs.We tackle the problem using the theory of virtual work,and relations between the virtual force and nodal displacements are analyzed to obtain elastic deformations.The global deformation is controlled by the total nodal deformations based on a force equation at each node.The simulation results verify the efficiency of the contact force and deformation model with reasonable realism.
Modelling Polymer Deformation during 3D Printing
McIlroy, Claire; Olmsted, Peter
Three-dimensional printing has the potential to transform manufacturing processes, yet improving the strength of printed parts, to equal that of traditionally-manufactured parts, remains an underlying issue. The fused deposition modelling technique involves melting a thermoplastic, followed by layer-by-layer extrusion to fabricate an object. The key to ensuring strength at the weld between layers is successful inter-diffusion. However, prior to welding, both the extrusion process and the cooling temperature profile can significantly deform the polymer micro-structure and, consequently, how well the polymers are able to ``re-entangle'' across the weld. In particular, polymer alignment in the flow can cause de-bonding of the layers and create defects. We have developed a simple model of the non-isothermal extrusion process to explore the effects that typical printing conditions and material rheology have on the conformation of a polymer melt. In particular, we incorporate both stretch and orientation using the Rolie-Poly constitutive equation to examine the melt structure as it flows through the nozzle, the subsequent alignment with the build plate and the resulting deformation due to the fixed nozzle height, which is typically less than the nozzle radius.
Rule-based spatial modeling with diffusing, geometrically constrained molecules
Directory of Open Access Journals (Sweden)
Lohel Maiko
2010-06-01
Full Text Available Abstract Background We suggest a new type of modeling approach for the coarse grained, particle-based spatial simulation of combinatorially complex chemical reaction systems. In our approach molecules possess a location in the reactor as well as an orientation and geometry, while the reactions are carried out according to a list of implicitly specified reaction rules. Because the reaction rules can contain patterns for molecules, a combinatorially complex or even infinitely sized reaction network can be defined. For our implementation (based on LAMMPS, we have chosen an already existing formalism (BioNetGen for the implicit specification of the reaction network. This compatibility allows to import existing models easily, i.e., only additional geometry data files have to be provided. Results Our simulations show that the obtained dynamics can be fundamentally different from those simulations that use classical reaction-diffusion approaches like Partial Differential Equations or Gillespie-type spatial stochastic simulation. We show, for example, that the combination of combinatorial complexity and geometric effects leads to the emergence of complex self-assemblies and transportation phenomena happening faster than diffusion (using a model of molecular walkers on microtubules. When the mentioned classical simulation approaches are applied, these aspects of modeled systems cannot be observed without very special treatment. Further more, we show that the geometric information can even change the organizational structure of the reaction system. That is, a set of chemical species that can in principle form a stationary state in a Differential Equation formalism, is potentially unstable when geometry is considered, and vice versa. Conclusions We conclude that our approach provides a new general framework filling a gap in between approaches with no or rigid spatial representation like Partial Differential Equations and specialized coarse-grained spatial
Methods for Geometric Data Validation of 3d City Models
Wagner, D.; Alam, N.; Wewetzer, M.; Pries, M.; Coors, V.
2015-12-01
Geometric quality of 3D city models is crucial for data analysis and simulation tasks, which are part of modern applications of the data (e.g. potential heating energy consumption of city quarters, solar potential, etc.). Geometric quality in these contexts is however a different concept as it is for 2D maps. In the latter case, aspects such as positional or temporal accuracy and correctness represent typical quality metrics of the data. They are defined in ISO 19157 and should be mentioned as part of the metadata. 3D data has a far wider range of aspects which influence their quality, plus the idea of quality itself is application dependent. Thus, concepts for definition of quality are needed, including methods to validate these definitions. Quality on this sense means internal validation and detection of inconsistent or wrong geometry according to a predefined set of rules. A useful starting point would be to have correct geometry in accordance with ISO 19107. A valid solid should consist of planar faces which touch their neighbours exclusively in defined corner points and edges. No gaps between them are allowed, and the whole feature must be 2-manifold. In this paper, we present methods to validate common geometric requirements for building geometry. Different checks based on several algorithms have been implemented to validate a set of rules derived from the solid definition mentioned above (e.g. water tightness of the solid or planarity of its polygons), as they were developed for the software tool CityDoctor. The method of each check is specified, with a special focus on the discussion of tolerance values where they are necessary. The checks include polygon level checks to validate the correctness of each polygon, i.e. closeness of the bounding linear ring and planarity. On the solid level, which is only validated if the polygons have passed validation, correct polygon orientation is checked, after self-intersections outside of defined corner points and edges
Geometric Models for Isotropic Random Porous Media: A Review
Directory of Open Access Journals (Sweden)
Helmut Hermann
2014-01-01
Full Text Available Models for random porous media are considered. The models are isotropic both from the local and the macroscopic point of view; that is, the pores have spherical shape or their surface shows piecewise spherical curvature, and there is no macroscopic gradient of any geometrical feature. Both closed-pore and open-pore systems are discussed. The Poisson grain model, the model of hard spheres packing, and the penetrable sphere model are used; variable size distribution of the pores is included. A parameter is introduced which controls the degree of open-porosity. Besides systems built up by a single solid phase, models for porous media with the internal surface coated by a second phase are treated. Volume fraction, surface area, and correlation functions are given explicitly where applicable; otherwise numerical methods for determination are described. Effective medium theory is applied to calculate physical properties for the models such as isotropic elastic moduli, thermal and electrical conductivity, and static dielectric constant. The methods presented are exemplified by applications: small-angle scattering of systems showing fractal-like behavior in limited ranges of linear dimension, optimization of nanoporous insulating materials, and improvement of properties of open-pore systems by atomic layer deposition of a second phase on the internal surface.
Dosimetric treatment course simulation based on a statistical model of deformable organ motion.
Söhn, M; Sobotta, B; Alber, M
2012-06-21
We present a method of modeling dosimetric consequences of organ deformation and correlated motion of adjacent organ structures in radiotherapy. Based on a few organ geometry samples and the respective deformation fields as determined by deformable registration, principal component analysis (PCA) is used to create a low-dimensional parametric statistical organ deformation model (Söhn et al 2005 Phys. Med. Biol. 50 5893-908). PCA determines the most important geometric variability in terms of eigenmodes, which represent 3D vector fields of correlated organ deformations around the mean geometry. Weighted sums of a few dominating eigenmodes can be used to simulate synthetic geometries, which are statistically meaningful inter- and extrapolations of the input geometries, and predict their probability of occurrence. We present the use of PCA as a versatile treatment simulation tool, which allows comprehensive dosimetric assessment of the detrimental effects that deformable geometric uncertainties can have on a planned dose distribution. For this, a set of random synthetic geometries is generated by a PCA model for each simulated treatment course, and the dose of a given treatment plan is accumulated in the moving tissue elements via dose warping. This enables the calculation of average voxel doses, local dose variability, dose-volume histogram uncertainties, marginal as well as joint probability distributions of organ equivalent uniform doses and thus of TCP and NTCP, and other dosimetric and biologic endpoints. The method is applied to the example of deformable motion of prostate/bladder/rectum in prostate IMRT. Applications include dosimetric assessment of the adequacy of margin recipes, adaptation schemes, etc, as well as prospective 'virtual' evaluation of the possible benefits of new radiotherapy schemes.
The Effects of Computer-assisted and Distance Learning of Geometric Modeling
Directory of Open Access Journals (Sweden)
Omer Faruk Sozcu
2013-01-01
Full Text Available The effects of computer-assisted and distance learning of geometric modeling and computer aided geometric design are studied. It was shown that computer algebra systems and dynamic geometric environments can be considered as excellent tools for teaching mathematical concepts of mentioned areas, and distance education technologies would be indispensable for consolidation of successfully passed topics
Geometric and colour data fusion for outdoor 3D models.
Merchán, Pilar; Adán, Antonio; Salamanca, Santiago; Domínguez, Vicente; Chacón, Ricardo
2012-01-01
This paper deals with the generation of accurate, dense and coloured 3D models of outdoor scenarios from scanners. This is a challenging research field in which several problems still remain unsolved. In particular, the process of 3D model creation in outdoor scenes may be inefficient if the scene is digitalized under unsuitable technical (specific scanner on-board camera) and environmental (rain, dampness, changing illumination) conditions. We address our research towards the integration of images and range data to produce photorealistic models. Our proposal is based on decoupling the colour integration and geometry reconstruction stages, making them independent and controlled processes. This issue is approached from two different viewpoints. On the one hand, given a complete model (geometry plus texture), we propose a method to modify the original texture provided by the scanner on-board camera with the colour information extracted from external images taken at given moments and under specific environmental conditions. On the other hand, we propose an algorithm to directly assign external images onto the complete geometric model, thus avoiding tedious on-line calibration processes. We present the work conducted on two large Roman archaeological sites dating from the first century A.D., namely, the Theatre of Segobriga and the Fori Porticus of Emerita Augusta, both in Spain. The results obtained demonstrate that our approach could be useful in the digitalization and 3D modelling fields.
Geometric and Colour Data Fusion for Outdoor 3D Models
Directory of Open Access Journals (Sweden)
Ricardo Chacón
2012-05-01
Full Text Available This paper deals with the generation of accurate, dense and coloured 3D models of outdoor scenarios from scanners. This is a challenging research field in which several problems still remain unsolved. In particular, the process of 3D model creation in outdoor scenes may be inefficient if the scene is digitalized under unsuitable technical (specific scanner on-board camera and environmental (rain, dampness, changing illumination conditions. We address our research towards the integration of images and range data to produce photorealistic models. Our proposal is based on decoupling the colour integration and geometry reconstruction stages, making them independent and controlled processes. This issue is approached from two different viewpoints. On the one hand, given a complete model (geometry plus texture, we propose a method to modify the original texture provided by the scanner on-board camera with the colour information extracted from external images taken at given moments and under specific environmental conditions. On the other hand, we propose an algorithm to directly assign external images onto the complete geometric model, thus avoiding tedious on-line calibration processes. We present the work conducted on two large Roman archaeological sites dating from the first century A.D., namely, the Theatre of Segobriga and the Fori Porticus of Emerita Augusta, both in Spain. The results obtained demonstrate that our approach could be useful in the digitalization and 3D modelling fields.
Discrete element modeling of subglacial sediment deformation
Damsgaard, Anders; Egholm, David L.; Piotrowski, Jan A.; Tulaczyk, Slawek; Larsen, Nicolaj K.; Tylmann, Karol
2013-12-01
The Discrete Element Method (DEM) is used in this study to explore the highly nonlinear dynamics of a granular bed when exposed to stress conditions comparable to those at the bed of warm-based glaciers. Complementary to analog experiments, the numerical approach allows a detailed analysis of the material dynamics and the shear zone development during progressive shear strain. The geometry of the heterogeneous stress network is visible in the form of force-carrying grain bridges and adjacent, volumetrically dominant, inactive zones. We demonstrate how the shear zone thickness and dilation depend on the level of normal (overburden) stress, and we show how high normal stress can mobilize material to great depths. The particle rotational axes tend to align with progressive shear strain, with rotations both along and reverse to the shear direction. The results from successive laboratory ring-shear experiments on simple granular materials are compared to results from similar numerical experiments. The simulated DEM material and all tested laboratory materials deform by an elastoplastic rheology under the applied effective normal stress. These results demonstrate that the DEM is a viable alternative to continuum models for small-scale analysis of sediment deformation. It can be used to simulate the macromechanical behavior of simple granular sediments, and it provides an opportunity to study how microstructures in subglacial sediments are formed during progressive shear strain.
Geometrical Models of the Locally Anisotropic Space-Time
Balan, V; Kokarev, S S; Pavlov, D G; Siparov, S V; Voicu, N
2011-01-01
Along with the construction of non-Lorentz-invariant effective field theories, recent studies which are based on geometric models of Finsler space-time become more and more popular. In this respect, the Finslerian approach to the problem of Lorentz symmetry violation is characterized by the fact that the violation of Lorentz symmetry is not accompanied by a violation of relativistic symmetry. That means, in particular, that preservation of relativistic symmetry can be considered as a rigorous criterion of the viability for any non-Lorentz-invariant effective field theory. Although this paper has a review character, it contains (with few exceptions) only those results on Finsler extensions of relativity theory, that were obtained by the authors.
Standalone visualization tool for three-dimensional DRAGON geometrical models
Energy Technology Data Exchange (ETDEWEB)
Lukomski, A.; McIntee, B.; Moule, D.; Nichita, E. [Faculty of Energy Systems and Nuclear Science, Univ. of Ontario Inst. of Tech., Oshawa, Ontario (Canada)
2008-07-01
DRAGON is a neutron transport and depletion code able to solve one-, two- and three-dimensional problems. To date DRAGON provides two visualization modules, able to represent respectively two- and three-dimensional geometries. The two-dimensional visualization module generates a postscript file, while the three dimensional visualization module generates a MATLAB M-file with instructions for drawing the tracks in the DRAGON TRACKING data structure, which implicitly provide a representation of the geometry. The current work introduces a new, standalone, tool based on the open-source Visualization Toolkit (VTK) software package which allows the visualization of three-dimensional geometrical models by reading the DRAGON GEOMETRY data structure and generating an axonometric image which can be manipulated interactively by the user. (author)
Geometrical properties of the Potts model during the coarsening regime.
Loureiro, Marcos P O; Arenzon, Jeferson J; Cugliandolo, Leticia F
2012-02-01
We study the dynamic evolution of geometric structures in a polydegenerate system represented by a q-state Potts model with nonconserved order parameter that is quenched from its disordered into its ordered phase. The numerical results obtained with Monte Carlo simulations show a strong relation between the statistical properties of hull perimeters in the initial state and during coarsening: The statistics and morphology of the structures that are larger than the averaged ones are those of the initial state, while the ones of small structures are determined by the curvature-driven dynamic process. We link the hull properties to the ones of the areas they enclose. We analyze the linear von Neumann-Mullins law, both for individual domains and on the average, concluding that its validity, for the later case, is limited to domains with number of sides around 6, while presenting stronger violations in the former case. © 2012 American Physical Society
Directory of Open Access Journals (Sweden)
Francisco Cavas-Martínez
Full Text Available AIM: To establish a new procedure for 3D geometric reconstruction of the human cornea to obtain a solid model that represents a personalized and in vivo morphology of both the anterior and posterior corneal surfaces. This model is later analyzed to obtain geometric variables enabling the characterization of the corneal geometry and establishing a new clinical diagnostic criterion in order to distinguish between healthy corneas and corneas with keratoconus. METHOD: The method for the geometric reconstruction of the cornea consists of the following steps: capture and preprocessing of the spatial point clouds provided by the Sirius topographer that represent both anterior and posterior corneal surfaces, reconstruction of the corneal geometric surfaces and generation of the solid model. Later, geometric variables are extracted from the model obtained and statistically analyzed to detect deformations of the cornea. RESULTS: The variables that achieved the best results in the diagnosis of keratoconus were anterior corneal surface area (ROC area: 0.847, p<0.000, std. error: 0.038, 95% CI: 0.777 to 0.925, posterior corneal surface area (ROC area: 0.807, p<0.000, std. error: 0.042, 95% CI: 0,726 to 0,889, anterior apex deviation (ROC area: 0.735, p<0.000, std. error: 0.053, 95% CI: 0.630 to 0.840 and posterior apex deviation (ROC area: 0.891, p<0.000, std. error: 0.039, 95% CI: 0.8146 to 0.9672. CONCLUSION: Geometric modeling enables accurate characterization of the human cornea. Also, from a clinical point of view, the procedure described has established a new approach for the study of eye-related diseases.
Saverin, Joseph; Peukert, Juliane; Marten, David; Pechlivanoglou, George; Paschereit, Christian Oliver; Greenblatt, David
2016-09-01
The current paper investigates the aeroelastic modelling of large, flexible multi- MW wind turbine blades. Most current performance prediction tools make use of the Blade Element Momentum (BEM) model, based upon a number of simplifying assumptions that hold only under steady conditions. This is why a lifting line free vortex wake (LLFVW) algorithm is used here to accurately resolve unsteady wind turbine aerodynamics. A coupling to the structural analysis tool BeamDyn, based on geometrically exact beam theory, allows for time-resolved aeroelastic simulations with highly deflected blades including bend-twist, coupling. Predictions of blade loading and deformation for rigid and flexible blades are analysed with reference to different aerodynamic and structural approaches. The emergency shutdown procedure is chosen as an examplary design load case causing large deflections to place emphasis on the influence of structural coupling and demonstrate the necessity of high fidelity structural models.
Discrete element modeling of subglacial sediment deformation
DEFF Research Database (Denmark)
Damsgaard, Anders; Egholm, David L.; Piotrowski, Jan A.
. The numerical approach allows for a detailed analysis of the material dynamics and shear zone development during progressive shear strain. We demonstrate how the shear zone thickness and dilation increase with the magnitude of the normal stress. The stresses are distributed heterogeneously through the granular...... of the inter-particle contacts parameterizes the model. For validating the numerical approach, the macromechanical behavior of the numerical material is compared to the results from successive laboratory ring-shear experiments. Overall, there is a good agreement between the geotechnical behavior of the real...... granular materials and the numerical results. The materials deform by an elasto-plastic rheology under the applied effective normal stress and horizontal shearing. The peak and ultimate shear strengths depend linearly on the magnitude of the normal stress by the Mohr-Coulomb constitutive relationship...
Rapid world modeling: Fitting range data to geometric primitives
Energy Technology Data Exchange (ETDEWEB)
Feddema, J.; Little, C.
1996-12-31
For the past seven years, Sandia National Laboratories has been active in the development of robotic systems to help remediate DOE`s waste sites and decommissioned facilities. Some of these facilities have high levels of radioactivity which prevent manual clean-up. Tele-operated and autonomous robotic systems have been envisioned as the only suitable means of removing the radioactive elements. World modeling is defined as the process of creating a numerical geometric model of a real world environment or workspace. This model is often used in robotics to plan robot motions which perform a task while avoiding obstacles. In many applications where the world model does not exist ahead of time, structured lighting, laser range finders, and even acoustical sensors have been used to create three dimensional maps of the environment. These maps consist of thousands of range points which are difficult to handle and interpret. This paper presents a least squares technique for fitting range data to planar and quadric surfaces, including cylinders and ellipsoids. Once fit to these primitive surfaces, the amount of data associated with a surface is greatly reduced up to three orders of magnitude, thus allowing for more rapid handling and analysis of world data.
Generalised geometrical CP violation in a T′ lepton flavour model
Energy Technology Data Exchange (ETDEWEB)
Girardi, Ivan [SISSA/INFN,Via Bonomea 265, I-34136 Trieste (Italy); Meroni, Aurora [SISSA/INFN,Via Bonomea 265, I-34136 Trieste (Italy); Dipartimento di Matematica e Fisica, Università di Roma Tre,Via della Vasca Navale 84, I-00146, Rome (Italy); INFN, Laboratori Nazionali di Frascati,Via E. Fermi 40, I-00044 Frascati (Italy); Petcov, S.T. [SISSA/INFN,Via Bonomea 265, I-34136 Trieste (Italy); IPMU, University of Tokyo,5-1-5 Kashiwanoha, 277-8583 Kashiwa (Japan); Spinrath, Martin [SISSA/INFN,Via Bonomea 265, I-34136 Trieste (Italy); Institut für Theoretische Teilchenphysik, Karlsruhe Institute of Technology,Engesserstraße 7, D-76131 Karlsruhe (Germany)
2014-02-12
We analyse the interplay of generalised CP transformations and the non-Abelian discrete group T′ and use the semi-direct product G{sub f}=T′⋊H{sub CP}, as family symmetry acting in the lepton sector. The family symmetry is shown to be spontaneously broken in a geometrical manner. In the resulting flavour model, naturally small Majorana neutrino masses for the light active neutrinos are obtained through the type I see-saw mechanism. The known masses of the charged leptons, lepton mixing angles and the two neutrino mass squared differences are reproduced by the model with a good accuracy. The model allows for two neutrino mass spectra with normal ordering (NO) and one with inverted ordering (IO). For each of the three spectra the absolute scale of neutrino masses is predicted with relatively small uncertainty. The value of the Dirac CP violation (CPV) phase δ in the lepton mixing matrix is predicted to be δ≅π/2 or 3π/2. Thus, the CP violating effects in neutrino oscillations are predicted to be maximal (given the values of the neutrino mixing angles) and experimentally observable. We present also predictions for the sum of the neutrino masses, for the Majorana CPV phases and for the effective Majorana mass in neutrinoless double beta decay. The predictions of the model can be tested in a variety of ongoing and future planned neutrino experiments.
Chang, Shengqian; Liu, Siqi; Yuan, Fei; Zheng, Zhenrong
2017-01-01
Since optical distortion has been a big trouble for various kinds of imaging systems, finding a simple correction method with wide applications is of significant importance. In this paper, we propose a unified and simple correction method, performing well for both photographic and projective imaging systems. The basic idea is regarding the optical distortion as geometrical deformation between the object and image, without considering the specific features of an optical system. First of all, a calibration template is employed to establish the geometrical transformation model (GTM) for the distortion of a built optical system. Two alternative algorithms are given to estimate the GTM in algebraic form. The computation is very simple because no intrinsic parameters of the optical system are needed to establish the GTM. Besides, the errors introduced by the fabricating and assembling process can be eliminated. Then, the corrected image of the photographic system or the pre-distorted image of the projective systems can be obtained accordingly utilizing the GTM. Experiments are conducted to demonstrate the effectiveness of our method with wide applications.
Meier, Christoph; Wall, Wolfgang A; Popp, Alexander
2016-01-01
Recently, the authors have proposed a novel all-angle beam contact (ABC) formulation that combines the advantages of existing point and line contact models in a variationally consistent manner. However, the ABC formulation has so far only been applied in combination with a special torsion-free beam model, which yields a very simple and efficient finite element formulation, but which is restricted to initially straight beams with isotropic cross-sections. In order to abstain from these restrictions, the current work combines the ABC formulation with a geometrically exact Kirchhoff-Love beam element formulation that is capable of treating even the most general cases of slender beam problems in terms of initial geometry and external loads. While the neglect of shear deformation that is inherent to this formulation has been shown to provide considerable numerical advantages in the range of high beam slenderness ratios, alternative shear-deformable beam models are required for examples with thick beams. The curren...
Energy Technology Data Exchange (ETDEWEB)
Moenkkoenen, H.; Rantanen, T.; Kuula, H. [WSP Finland Oy, Helsinki (Finland)
2012-05-15
In this report, the rock mechanics parameters of fractures and brittle deformation zones have been estimated in the vicinity of the ONKALO area at the Olkiluoto site, western Finland. This report is an extension of the previously published report: Geometrical and Mechanical properties if the fractures and brittle deformation zones based on ONKALO tunnel mapping, 0-2400 m tunnel chainage (Kuula 2010). In this updated report, mapping data are from 2400-4390 m tunnel chainage. Defined rock mechanics parameters of the fractures are associated with the rock engineering classification quality index, Q', which incorporates the RQD, Jn, Jr and Ja values. The friction angle of the fracture surfaces is estimated from the Jr and Ja numbers. There are no new data from laboratory joint shear and normal tests. The fracture wall compressive strength (JCS) data are available from the chainage range 1280-2400 m. Estimation of the mechanics properties of the 24 brittle deformation zones (BDZ) is based on the mapped Q' value, which is transformed to the GSI value in order to estimate strength and deformability properties. A component of the mapped Q' values is from the ONKALO and another component is from the drill cores. In this study, 24 BDZs have been parameterized. The location and size of the brittle deformation are based on the latest interpretation. New data for intact rock strength of the brittle deformation zones are not available. (orig.)
Deformation and Development Tendency of Shiliushubao Landslide by Numerical Modeling
Institute of Scientific and Technical Information of China (English)
LI Xiuzhen; KONG Jiming; XU Qiang
2006-01-01
On the basis of analysing basic features of Shiliushubao landslide, the landslide's deformation and development tendency are quantitatively studied by using FLAC3D program. The results accord with monitoring results. The results are indicated that reservoir impounding accelerates the landslide's deformation, and the variation of reservoir water level is key factor of affecting the deformation; The landslide has the characters of pull-behind movement according to the displacement of the landslide body gradually reducing from leading edge to trailing edge; Excavating and deloading slow down the landslide's deformation in the certain degree. On the basis, the deformation developmental tendency of Shiliushubao landslide is predicted by the established simulating model.
A geometric growth model interpolating between regular and small-world networks
Energy Technology Data Exchange (ETDEWEB)
Zhang, Zhongzhi [Department of Computer Science and Engineering, Fudan University, Shanghai 200433 (China); Zhou, Shuigeng [Department of Computer Science and Engineering, Fudan University, Shanghai 200433 (China); Wang, Zhiyong [Department of Computer Science and Engineering, Fudan University, Shanghai 200433 (China); Shen, Zhen [Department of Computer Science and Engineering, Fudan University, Shanghai 200433 (China)
2007-09-28
We propose a geometric growth model which interpolates between one-dimensional linear graphs and small-world networks. The model undergoes a transition from large to small worlds. We study the topological characteristics by both theoretical predictions and numerical simulations, which are in good accordance with each other. Our geometrically growing model is a complementarity for the static WS model.
q-Deformation of Lorentzian spin foam models
Fairbairn, Winston J
2011-01-01
We construct and analyse a quantum deformation of the Lorentzian EPRL model. The model is based on the representation theory of the quantum Lorentz group with real deformation parameter. We give a definition of the quantum EPRL intertwiner, study its convergence and braiding properties and construct an amplitude for the four-simplexes. We find that the resulting model is finite.
Indian Academy of Sciences (India)
T N Janko; C Njiki Chatu´e; M Kw´ekam; B E Bella Nk´e; A F Yakeu Sandjo; E M Fozing
2017-03-01
The Numba ductile deformation zone (NDDZ) is characterised by folds recorded during the three deformation phases that affected the banded amphibole gneiss. Fold-shape analyses using the program Fold Profiler with the aim to show the importance of folding events in the structural analysis of the NDDZ and its contribution to the Pan-African orogeny in central Africa have been made. Classical field method, conic sections method and Ramsay’s fold classification method were applied to (i) have the general orientation of folds, (ii) analyze the fold shapes and (iii) classify the geometry of the folded bands. Fold axes in banded amphibole gneiss plunge moderately (<15◦) towards the NNE or SSW. The morphology of F₁, F₂ and F₃ folds in the study area clearly points to (i) Z-shape folds with SE vergence and (ii) a dextral sense of shear motion. Conic section method reveals two dominant families: F₁ and F₃ folds belong to parabolic shape folds, while F₂ folds belong to parabolic shape and hyperbolic shape folds. Ramsay’s scheme emphasizes class 1C (for F₁, F₂ and F₃ folds) and class 3 (for F₂ folds) as main fold classes. The co-existence of the various fold shapes can be explained by (i) the structuration of the banded gneiss, (ii) the folding mechanisms that associate shear with a non-least compressive or flattening component in a ductile shear zone and (iii) the change in rheological properties of the band during the period of fold formation. These data allow us to conclude that the Numba region underwent ductile dextral shear and can be integrated (i) in a correlation model with the Central Cameroon Shear Zone(CCSZ) and associated syn-kinematic intrusions and (ii) into the tectonic model of Pan-African belt of central Africa in Cameroon.
Integrability of a New Type of Deformed XXZ Model
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
A new type of deformed XXZ model was constructed and diagonalized by the coordinate Bethe ansatz method. We obtained the energy and the Bethe ansatz equations of the model and also discussed some thermodynamics of the model.
Free-form geometric modeling by integrating parametric and implicit PDEs.
Du, Haixia; Qin, Hong
2007-01-01
Parametric PDE techniques, which use partial differential equations (PDEs) defined over a 2D or 3D parametric domain to model graphical objects and processes, can unify geometric attributes and functional constraints of the models. PDEs can also model implicit shapes defined by level sets of scalar intensity fields. In this paper, we present an approach that integrates parametric and implicit trivariate PDEs to define geometric solid models containing both geometric information and intensity distribution subject to flexible boundary conditions. The integrated formulation of second-order or fourth-order elliptic PDEs permits designers to manipulate PDE objects of complex geometry and/or arbitrary topology through direct sculpting and free-form modeling. We developed a PDE-based geometric modeling system for shape design and manipulation of PDE objects. The integration of implicit PDEs with parametric geometry offers more general and arbitrary shape blending and free-form modeling for objects with intensity attributes than pure geometric models.
Content-Based Search on a Database of Geometric Models: Identifying Objects of Similar Shape
Energy Technology Data Exchange (ETDEWEB)
XAVIER, PATRICK G.; HENRY, TYSON R.; LAFARGE, ROBERT A.; MEIRANS, LILITA; RAY, LAWRENCE P.
2001-11-01
The Geometric Search Engine is a software system for storing and searching a database of geometric models. The database maybe searched for modeled objects similar in shape to a target model supplied by the user. The database models are generally from CAD models while the target model may be either a CAD model or a model generated from range data collected from a physical object. This document describes key generation, database layout, and search of the database.
An extension of dynamic droplet deformation models to secondary atomization
Bartz, F.O.; Schmehl, R.; Koch, R.; Bauer, H.J.
2010-01-01
A detailed model for secondary atomization of liquid droplets by aerodynamic forces is presented. As an empirical extension of dynamic droplet deformation models, it accounts for temporal variations of the relative velocity between droplet and gas phase during the deformation and breakup process and
Integrability of the eta-deformed Neumann-Rosochatius model
Arutyunov, Gleb; Medina-Rincon, Daniel
2016-01-01
An integrable deformation of the well-known Neumann-Rosochatius system is studied by considering generalised bosonic spinning solutions on the eta-deformed AdS_5 x S^5 background. For this integrable model we construct a 4x4 Lax representation and a set of integrals of motion that ensures its Liouville integrability. These integrals of motion correspond to the deformed analogues of the Neumann-Rosochatius integrals and generalise the previously found integrals for the eta-deformed Neumann and (AdS_5 x S^5)_eta geodesic systems. Finally, we briefly comment on consistent truncations of this model.
Modeling Study of Planar Flexible Manipulator Undergoing Large Deformation
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The planar flexible manipulator undergoing large deformation is investigated by using finite element method (FEM). Three kinds of reference frames are employed to describe the deformation of arbitrary point in the flexible manipulator, which are global frame, body-fixed frame and co-rotational frame. The rigid-flexible coupling dynamic equation of the planar flexible manipulator is derived using the Hamilton's principle. Numerical simulations are carried out in the end of this paper to demonstrate the effectiveness of the proposed model. The simulation results indicate that the proposed model is efficient not only for small deformation but also for large deformation.
Game model of safety monitoring for arch dam deformation
Institute of Scientific and Technical Information of China (English)
2008-01-01
Arch dam deformation is comprehensively affected by water pressure,temperature,dam’s structural behavior and material properties as well as other factors.Among them the water pressure and temperature are external factors(source factors) that cause dam deformation,and dam’s structural behavior and material properties are the internal factors of deformation(resistance factors).The dam deformation is the result of the mutual game playing between source factors and resistance factors.Therefore,resistance factors of structure and materials that reflect resistance character of arch dam structure are introduced into the traditional model,where structure factor is embodied by the flexibility coefficient of dam body and the maximum dam height,and material property is embodied by the elastic modulus of dam.On the basis of analyzing the correlation between dam deformation and resistance factors,the game model of safety monitoring for arch dam deformation is put forward.
Modeling the Microstructural Evolution during Hot Deformation of Microalloyed Steels
Bäcke, Linda
2009-01-01
This thesis contains the development of a physically-based model describing the microstructural evolution during hot deformation of microalloyed steels. The work is mainly focused on the recrystallization kinetics. During hot rolling, the repeated deformation and recrystallization provides progressively refined recrystallized grains. Also, recrystallization enables the material to be deformed more easily and knowledge of the recrystallization kinetics is important in order to predict the re...
GEOMETRIC MODEL OF THE NAZCA PLATE SUBDUCTION IN SOUTHWEST COLOMBIA
Directory of Open Access Journals (Sweden)
Monsalve J Hugo
2007-12-01
Full Text Available A geometric model for the subduction of the Nazca plate beneath the South American plate in southwestern of Colombia is proposed based on the relocation of hypocenters of local and distant
earthquakes. By means of the simultaneous inversion of teleseismic P and SH body waves, the depths of the 15 events with Mw ≥ 5.8 were constrained, and the hypocenters of the 250 earthquakes recorded
between 1990 and 2005 by the International Seismological Centre (ISC and U.S. Geological Survey, National Earthquake Information Center (NEIC were constrained and relocated. A model is proposed
for the hypocentral sections taking into account the trench along of the Earth and Colombia-Ecuador.
Three different possible shapes of subduction of the Nazca plate in the Colombia-Ecuador trench were obtained: The first configuration, in the Cali A segment, the dip angle changes from17º to 45º down to a maximum depth of 100km; the second configuration, in the Popayán B and Nariño C segments, the dip angle holds approximately constant at 30º down to a maximum depth of 200 km; and the third configuration, in the Quito D segment, the dip angle changes of 9º to 50º to a maximum depth 220 km. The maximum depth of seismicity along the Colombia-Ecuador trench shows two increases, the first between latitudes 4.5ºN-5ºN and the second between the latitudes 1ºS-2ºS, which suggest that the presence of the Malpelo and Carnegie Ridges may generate a differential blockage at the Pacific Colombia-Ecuador basin.
Deformation modeling and constitutive modeling for anisotropic superalloys
Milligan, Walter W.; Antolovich, Stephen D.
1989-01-01
A study of deformation mechanisms in the single crystal superalloy PWA 1480 was conducted. Monotonic and cyclic tests were conducted from 20 to 1093 C. Both (001) and near-(123) crystals were tested, at strain rates of 0.5 and 50 percent/minute. The deformation behavior could be grouped into two temperature regimes: low temperatures, below 760 C; and high temperatures, above 820 to 950 C depending on the strain rate. At low temperatures, the mechanical behavior was very anisotropic. An orientation dependent CRSS, a tension-compression asymmetry, and anisotropic strain hardening were all observed. The material was deformed by planar octahedral slip. The anisotropic properties were correlated with the ease of cube cross-slip, as well as the number of active slip systems. At high temperatures, the material was isotropic, and deformed by homogeneous gamma by-pass. It was found that the temperature dependence of the formation of superlattice-intrinsic stacking faults was responsible for the local minimum in the CRSS of this alloy at 400 C. It was proposed that the cube cross-slip process must be reversible. This was used to explain the reversible tension-compression asymmetry, and was used to study models of cross-slip. As a result, the cross-slip model proposed by Paidar, Pope and Vitek was found to be consistent with the proposed slip reversibility. The results were related to anisotropic viscoplastic constitutive models. The model proposed by Walter and Jordan was found to be capable of modeling all aspects of the material anisotropy. Temperature and strain rate boundaries for the model were proposed, and guidelines for numerical experiments were proposed.
A General Polygon-based Deformable Model for Object Recognition
DEFF Research Database (Denmark)
Jensen, Rune Fisker; Carstensen, Jens Michael
1999-01-01
We propose a general scheme for object localization and recognition based on a deformable model. The model combines shape and image properties by warping a arbitrary prototype intensity template according to the deformation in shape. The shape deformations are constrained by a probabilistic...... distribution, which combined with a match of the warped intensity template and the image form the final criteria used for localization and recognition of a given object. The chosen representation gives the model an ability to model an almost arbitrary object. Beside the actual model a full general scheme...
Preliminary deformation model for National Seismic Hazard map of Indonesia
Energy Technology Data Exchange (ETDEWEB)
Meilano, Irwan; Gunawan, Endra; Sarsito, Dina; Prijatna, Kosasih; Abidin, Hasanuddin Z. [Geodesy Research Division, Faculty of Earth Science and Technology, Institute of Technology Bandung (Indonesia); Susilo,; Efendi, Joni [Agency for Geospatial Information (BIG) (Indonesia)
2015-04-24
Preliminary deformation model for the Indonesia’s National Seismic Hazard (NSH) map is constructed as the block rotation and strain accumulation function at the elastic half-space. Deformation due to rigid body motion is estimated by rotating six tectonic blocks in Indonesia. The interseismic deformation due to subduction is estimated by assuming coupling on subduction interface while deformation at active fault is calculated by assuming each of the fault‘s segment slips beneath a locking depth or in combination with creeping in a shallower part. This research shows that rigid body motion dominates the deformation pattern with magnitude more than 15 mm/year, except in the narrow area near subduction zones and active faults where significant deformation reach to 25 mm/year.
Emergent lattices with geometrical frustration in doped extended Hubbard models
Kaneko, Ryui; Tocchio, Luca F.; Valentí, Roser; Gros, Claudius
2016-11-01
Spontaneous charge ordering occurring in correlated systems may be considered as a possible route to generate effective lattice structures with unconventional couplings. For this purpose we investigate the phase diagram of doped extended Hubbard models on two lattices: (i) the honeycomb lattice with on-site U and nearest-neighbor V Coulomb interactions at 3 /4 filling (n =3 /2 ) and (ii) the triangular lattice with on-site U , nearest-neighbor V , and next-nearest-neighbor V' Coulomb interactions at 3 /8 filling (n =3 /4 ). We consider various approaches including mean-field approximations, perturbation theory, and variational Monte Carlo. For the honeycomb case (i), charge order induces an effective triangular lattice at large values of U /t and V /t , where t is the nearest-neighbor hopping integral. The nearest-neighbor spin exchange interactions on this effective triangular lattice are antiferromagnetic in most of the phase diagram, while they become ferromagnetic when U is much larger than V . At U /t ˜(V/t ) 3 , ferromagnetic and antiferromagnetic exchange interactions nearly cancel out, leading to a system with four-spin ring-exchange interactions. On the other hand, for the triangular case (ii) at large U and finite V', we find no charge order for small V , an effective kagome lattice for intermediate V , and one-dimensional charge order for large V . These results indicate that Coulomb interactions induce [case (i)] or enhance [case(ii)] emergent geometrical frustration of the spin degrees of freedom in the system, by forming charge order.
Geometric modeling and analysis of large latticed surfaces
Nayfeh, A. H.; Hefzy, M. S.
1980-01-01
The application of geometrical schemes, similar to geodesic domes, to large spherical antenna reflectors was investigated. The shape and size of flat segmented latticed surfaces which approximate general shells of revolution, and in particular spherical and paraboloidal reflective surfaces, were determined. The extensive mathematical and computational geometric analyses of the reflector resulted in the development of a general purpose computer program capable of generating the complete design parameters of the dish. The program also includes a graphical self contained subroutine for graphic display of the required design.
Information Geometric Complexity of a Trivariate Gaussian Statistical Model
Directory of Open Access Journals (Sweden)
Domenico Felice
2014-05-01
Full Text Available We evaluate the information geometric complexity of entropic motion on low-dimensional Gaussian statistical manifolds in order to quantify how difficult it is to make macroscopic predictions about systems in the presence of limited information. Specifically, we observe that the complexity of such entropic inferences not only depends on the amount of available pieces of information but also on the manner in which such pieces are correlated. Finally, we uncover that, for certain correlational structures, the impossibility of reaching the most favorable configuration from an entropic inference viewpoint seems to lead to an information geometric analog of the well-known frustration effect that occurs in statistical physics.
Indian Academy of Sciences (India)
Prantik Mukhopadhyay
2009-08-01
The recovered cold rolled microstructure obtained from orientation image microstructure of Al–4%Mg–0.5%Mn alloy (AA5182 alloy) was superimposed on the grid of cellular automata based microstructure model. The Taylor factors of deformed/cold rolled orientations were considered as the driving force for recrystallization. The local development of recrystallized microstructure and texture were simulated with orientation dependent grain boundary mobility and compared with the experimental results.
Geometric Modeling Applications Interface Program (GMAP). Volume 1. Executive Overview
1989-09-01
Z . Code) 10. SOURCE OF FUNDING NOS. PROGRAM PROJECT TASK WORK UNIT ELEMENT NO. NO. NO. NO. 11. TITLE (Include Security Classification) GEOMETRIC...342f CI FTR560240OOlU September 1989 SECTION 2 SCOPE OF GMAP GMAP focused on the generacion , control, and exchange of computer information to replace
Meshless methods for physics-based modeling and simulation of deformable models
Institute of Scientific and Technical Information of China (English)
GUO XiaoHu; QIN Hong
2009-01-01
As 3D digital photographic and scanning devices produce higher resolution Images,acquired geometric data sets grow more complex in terms of the modeled objects' size,geometry,and topology.As a consequence,point-sampled geometry Is becoming ubiquitous in graphics and geometric information processing,and poses new challenges which have not been fully resolved by the state-of-art graphical techniques.In this paper,we address the challenges by proposing a meshless computational framework for dynamic modeling and simulation of solids and thin-shells represented as point sampies.Our meshless framework can directly compute the elastic deformation and fracture propagation for any scanned point geometry,without the need of converting them to polygonal meshes or higher order spline representations.We address the necessary computational techniques,such as Moving Least Squares,Hierarchical Discretization,and Modal Warping,to effectively and efficiently compute the physical simulation in real-time.This meshlesa computational framework alms to bridge the gap between the point-sampled geometry with physics-baaed modeling and simulation governed by partial differential equations.
Complex structure-induced deformations of sigma-models
Bykov, Dmitri
2016-01-01
We describe a deformation of the principal chiral model (with an even-dimensional target space G) by a B-field proportional to the K\\"ahler form on the target space. The equations of motion of the deformed model admit a zero-curvature representation. As a simplest example, we consider the case of G=S^1 x S^3. We also apply a variant of the construction to a deformation of the AdS_3 x S^3 x S^1 (super-)sigma-model.
Getting inflationary models using the deformation method
Rodrigues, Jamilton
2014-01-01
We show as the dynamics for the inflaton, under slow-roll regime, can be treated in a other dynamics, following the deformation procedure. In a direct way we present a relationship between two slow-roll inflationary potentials, and we apply this framework to show how to construct an eternal inflation from chaotic inflation, or even, a natural inflation from hilltop inflation, easily.
Ebrahimi, Farzad; Barati, Mohammad Reza
2016-11-01
Free vibration analysis is presented for a simply supported, functionally graded piezoelectric (FGP) nanobeam embedded on elastic foundation in the framework of third-order parabolic shear deformation beam theory. Effective electro-mechanical properties of FGP nanobeam are supposed to be variable throughout the thickness based on power-law model. To incorporate the small size effects into the local model, Eringen's nonlocal elasticity theory is adopted. Analytical solution is implemented to solve the size-dependent buckling analysis of FGP nanobeams based upon a higher-order shear deformation beam theory where coupled equations obtained using Hamilton's principle exist for such beams. Some numerical results for natural frequencies of the FGP nanobeams are prepared, which include the influences of elastic coefficients of foundation, electric voltage, material and geometrical parameters and mode number. This study is motivated by the absence of articles in the technical literature and provides beneficial results for accurate FGP structures design.
Modeling of Surface Geometric Structure State After Integratedformed Milling and Finish Burnishing
Berczyński, Stefan; Grochała, Daniel; Grządziel, Zenon
2017-06-01
The article deals with computer-based modeling of burnishing a surface previously milled with a spherical cutter. This method of milling leaves traces, mainly asperities caused by the cutting crossfeed and cutter diameter. The burnishing process - surface plastic treatment - is accompanied by phenomena that take place right in the burnishing ball-milled surface contact zone. The authors present the method for preparing a finite element model and the methodology of tests for the assessment of height parameters of a surface geometrical structure (SGS). In the physical model the workpieces had a cuboidal shape and these dimensions: (width × height × length) 2×1×4.5 mm. As in the process of burnishing a cuboidal workpiece is affected by plastic deformations, the nonlinearities of the milled item were taken into account. The physical model of the process assumed that the burnishing ball would be rolled perpendicularly to milling cutter linear traces. The model tests included the application of three different burnishing forces: 250 N, 500 N and 1000 N. The process modeling featured the contact and pressing of a ball into the workpiece surface till the desired force was attained, then the burnishing ball was rolled along the surface section of 2 mm, and the burnishing force was gradually reduced till the ball left the contact zone. While rolling, the burnishing ball turned by a 23° angle. The cumulative diagrams depict plastic deformations of the modeled surfaces after milling and burnishing with defined force values. The roughness of idealized milled surface was calculated for the physical model under consideration, i.e. in an elementary section between profile peaks spaced at intervals of crossfeed passes, where the milling feed fwm = 0.5 mm. Also, asperities after burnishing were calculated for the same section. The differences of the obtained values fall below 20% of mean values recorded during empirical experiments. The adopted simplification in after
Real-time model for simulating a tracked vehicle on deformable soils
Directory of Open Access Journals (Sweden)
Martin Meywerk
2016-05-01
Full Text Available Simulation is one possibility to gain insight into the behaviour of tracked vehicles on deformable soils. A lot of publications are known on this topic, but most of the simulations described there cannot be run in real-time. The ability to run a simulation in real-time is necessary for driving simulators. This article describes an approach for real-time simulation of a tracked vehicle on deformable soils. The components of the real-time model are as follows: a conventional wheeled vehicle simulated in the Multi Body System software TRUCKSim, a geometric description of landscape, a track model and an interaction model between track and deformable soils based on Bekker theory and Janosi–Hanamoto, on one hand, and between track and vehicle wheels, on the other hand. Landscape, track model, soil model and the interaction are implemented in MATLAB/Simulink. The details of the real-time model are described in this article, and a detailed description of the Multi Body System part is omitted. Simulations with the real-time model are compared to measurements and to a detailed Multi Body System–finite element method model of a tracked vehicle. An application of the real-time model in a driving simulator is presented, in which 13 drivers assess the comfort of a passive and an active suspension of a tracked vehicle.
A differential-geometric approach to generalized linear models with grouped predictors
Augugliaro, Luigi; Mineo, Angelo M.; Wit, Ernst C.
2016-01-01
We propose an extension of the differential-geometric least angle regression method to perform sparse group inference in a generalized linear model. An efficient algorithm is proposed to compute the solution curve. The proposed group differential-geometric least angle regression method has important
dMODELS: A software package for modeling volcanic deformation
Battaglia, Maurizio
2017-04-01
dMODELS is a software package that includes the most common source models used to interpret deformation measurements near active volcanic centers. The emphasis is on estimating the parameters of analytical models of deformation by inverting data from the Global Positioning System (GPS), Interferometric Synthetic Aperture Radar (InSAR), tiltmeters and strainmeters. Source models include: (a) pressurized spherical, ellipsoidal and sill-like magma chambers in an elastic, homogeneous, flat half-space; (b) pressurized spherical magma chambers with topography corrections; and (c) the solutions for a dislocation (fracture) in an elastic, homogeneous, flat half-space. All of the equations have been extended to include deformation and strain within the Earth's crust (as opposed to only at the Earth's surface) and verified against finite element models. Although actual volcanic sources are not embedded cavities of simple shape, we assume that these models may reproduce the stress field created by the actual magma intrusion or hydrothermal fluid injection. The dMODELS software employs a nonlinear inversion algorithm to determine the best-fit parameters for the deformation source by searching for the minimum of the cost function χv2 (chi square per degrees of freedom). The non-linear inversion algorithm is a combination of local optimization (interior-point method) and random search. This approach is more efficient for hyper-parameter optimization than trials on a grid. The software has been developed using MATLAB, but compiled versions that can be run using the free MATLAB Compiler Runtime (MCR) module are available for Windows 64-bit operating systems. The MATLAB scripts and compiled files are open source and intended for teaching and research. The software package includes both functions for forward modeling and scripts for data inversion. A software demonstration will be available during the meeting. You are welcome to contact the author at mbattaglia@usgs.gov for
Modeling Steady Acoustic Fields Bounded in Cavities with Geometrical Imperfections
Albo, P. A. Giuliano; Gavioso, R. M.; Benedetto, G.
2010-07-01
A mathematical method is derived within the framework of classical Lagrangian field theory, which is suitable for the determination of the eigenstates of acoustic resonators of nearly spherical shape. The method is based on the expansion of the Helmholtz differential operator and the boundary condition in a power series of a small geometrical perturbation parameter {ɛ} . The method extends to orders higher than {ɛ^2} the calculation of the perturbed acoustic eigenvalues, which was previously limited by the use of variational formalism and the methods of Morse and Ingard. A specific example is worked out for radial modes of a prolate spheroid, with the frequency perturbation calculated to order {ɛ^3} . A possible strategy to tackle the problem of calculating the acoustic eigenvalues for cavities presenting non-smooth geometrical imperfections is also described.
Relativistic Hartree-Fock-Bogoliubov model for deformed nuclei
Ebran, J -P; Arteaga, D Pena; Vretenar, D
2010-01-01
The Relativistic Hartree-Fock-Bogoliubov model for axially deformed nuclei (RHFBz) is introduced. The model is based on an effective Lagrangian with density-dependent meson-nucleon couplings in the particle-hole channel, and the pairing part of the Gogny force is used in the pairing channel. The RHFBz quasiparticle equations are solved by expansion in the basis of a deformed harmonic oscillator. Illustrative RHFBz calculations are performed for Carbon, Neon and Magnesium isotopes. The effect of the explicitly including the pion field is investigated for binding energies, deformation parameters, and charge radii.
An Efficient Data-driven Tissue Deformation Model
DEFF Research Database (Denmark)
Mosbech, Thomas Hammershaimb; Ersbøll, Bjarne Kjær; Christensen, Lars Bager
2009-01-01
empirical data; 10 pig carcasses are subjected to deformation from a controlled source imitating the cutting tool. The tissue deformation is quantified by means of steel markers inserted into the carcass as a three-dimensional lattice. For each subject marker displacements are monitored through two...... consecutive computed tomography images - before and after deformation; tracing corresponding markers provides accurate information on the tissue deformation. To enable modelling of the observed deformations, the displacements are parameterised applying methods from point-based registration...... find an association between the first principal mode and the lateral movement. Furthermore, there is a link between this and the ratio of meat-fat quantity - a potentially very useful finding since existing tools for carcass grading and sorting measure equivalent quantities....
Finite element modelling of manufacturing processes for plastic deformation
Directory of Open Access Journals (Sweden)
Fernando Mejía Umaña
2010-04-01
Full Text Available The object of the Mechanical and Electrical Engineering Departament's computational mechanics of solids section is to offer industry solutions to problems requiring deeper knowledge regarding the mechanincs of solids and how they can be numerically modelled. This article summarises the foundations of plastic deformation, together with the results obtained during the experimental phase and from modelling two applications of plastic deformation processes being studied as part of mechanical engineering students' undergraduate projects.
Winter, Samantha Lee; Forrest, Sarah Michelle; Wallace, Joanne; Challis, John H
2017-08-08
The purpose of this study was to validate a new geometric solids model, developed to address the lack of female specific models for body segment inertial parameter estimation. A second aim was to determine the effect of reducing the number of geometric solids used to model the limb segments on model accuracy. The 'full' model comprised 56 geometric solids, the 'reduced' 31, and the 'basic' 16. Predicted whole-body inertial parameters were compared with direct measurements (reaction board, scales), and predicted segmental parameters with those estimated from whole-body DXA scans for 28 females. The percentage root mean square error (%RMSE) for whole-body volume was geometric solids are required to more accurately model the trunk.
Relativistic models of magnetars: structure and deformations
Colaiuda, A; Gualtieri, L; Pons, J A
2007-01-01
We find numerical solutions of the coupled system of Einstein-Maxwell's equations with a linear approach, in which the magnetic field acts as a perturbation of a spherical neutron star. In our study, magnetic fields having both poloidal and toroidal components are considered, and higher order multipoles are also included. We evaluate the deformations induced by different field configurations, paying special attention to those for which the star has a prolate shape. We also explore the dependence of the stellar deformation on the particular choice of the equation of state and on the mass of the star. Our results show that, for neutron stars with mass M = 1.4 Msun and surface magnetic fields of the order of 10^15 G, a quadrupole ellipticity of the order of 10^(-6) - 10^(-5) should be expected. Low mass neutron stars are in principle subject to larger deformations (quadrupole ellipticities up to 10^(-3) in the most extreme case). The effect of quadrupolar magnetic fields is comparable to that of dipolar componen...
A Geometric Model of Multiaxial Warp-knitted Preform for Composite Reinforcement
Institute of Scientific and Technical Information of China (English)
周荣星; 李炜; 陈南梁; 冯勋伟
2003-01-01
A new geometric model of Multiaxial Warp-Knitted (MWK) performs, which is based on the experimental observations and analysis of basic stitch, is developed to relate the geometric parameters and process variables. The fiber volume fraction and fibre orientation of MWK reinforced composites are described in terms of structural and processing parameters in the model. And this model provides a basis for the prediction of mechanical behavior of the MWK reinforced composites.
Evaluation of Rational Function Model for Geometric Modeling of CHANG'E-1 CCD Images
Liu, Y.; Di, K.
2011-08-01
Rational Function Model (RFM) is a generic geometric model that has been widely used in geometric processing of high-resolution earth-observation satellite images, due to its generality and excellent capability of fitting complex rigorous sensor models. In this paper, the feasibility and precision of RFM for geometric modeling of China's Chang'E-1 (CE-1) lunar orbiter images is presented. The RFM parameters of forward-, nadir- and backward-looking CE-1 images are generated though least squares solution using virtual control points derived from the rigorous sensor model. The precision of the RFM is evaluated by comparing with the rigorous sensor model in both image space and object space. Experimental results using nine images from three orbits show that RFM can precisely fit the rigorous sensor model of CE-1 CCD images with a RMS residual error of 1/100 pixel level in image space and less than 5 meters in object space. This indicates that it is feasible to use RFM to describe the imaging geometry of CE-1 CCD images and spacecraft position and orientation. RFM will enable planetary data centers to have an option to supply RFM parameters of orbital images while keeping the original orbit trajectory data confidential.
An Optimized Method for PDEs-Based Geometric Modeling and Reconstruction
Directory of Open Access Journals (Sweden)
Chuanjun Wang
2012-09-01
Full Text Available This study presents an optimized method for efficient geometric modeling and reconstruction using Partial Differential Equations (PDEs. Based on the identification between the analytic solution of Bloor Wilson PDE and the Fourier series, we transform the problem of model selection for PDEs-based geometric modeling into the problem of significant frequencies selection from Fourier series. With the significance analysis of the Fourier series, a model selection and an iterative surface fitting algorithm are applied to address the problem of overfitting and underfitting in the PDEs-based geometric modeling and reconstruction. Simulations are conducted on both the computer generated geometric surface and the laser scanned 3D face data. Experiment results show the merits of the proposed method.
Modeling thermodynamic distance, curvature and fluctuations a geometric approach
Badescu, Viorel
2016-01-01
This textbook aims to briefly outline the main directions in which the geometrization of thermodynamics has been developed in the last decades. The textbook is accessible to people trained in thermal sciences but not necessarily with solid formation in mathematics. For this, in the first chapters a summary of the main mathematical concepts is made. In some sense, this makes the textbook self-consistent. The rest of the textbook consists of a collection of results previously obtained in this young branch of thermodynamics. The manner of presentation used throughout the textbook is adapted for ease of access of readers with education in natural and technical sciences.
A geometric level set model for ultrasounds analysis
Energy Technology Data Exchange (ETDEWEB)
Sarti, A.; Malladi, R.
1999-10-01
We propose a partial differential equation (PDE) for filtering and segmentation of echocardiographic images based on a geometric-driven scheme. The method allows edge-preserving image smoothing and a semi-automatic segmentation of the heart chambers, that regularizes the shapes and improves edge fidelity especially in presence of distinct gaps in the edge map as is common in ultrasound imagery. A numerical scheme for solving the proposed PDE is borrowed from level set methods. Results on human in vivo acquired 2D, 2D+time,3D, 3D+time echocardiographic images are shown.
Institute of Scientific and Technical Information of China (English)
颜昭雯; 陈敏茹; 吴可; 赵伟忠
2012-01-01
Based on the covariant prolongation structure technique,we construct the integrable higher-order deformations of the (2+1)-dimensional Heisenberg ferromagnet model and obtain their su(2)×R(λ) prolongation structures.By associating these deformed multidimensional Heisenberg ferromagnet models with the moving space curve in Euclidean space and using the Hasimoto function,we derive their geometrical equivalent counterparts,i.e.,higher-order (2+1)-dimensional nonlinear Schr?dinger equations.
Directory of Open Access Journals (Sweden)
Khalaf A. M.
2014-01-01
Full Text Available The critical points of potential energy surface (PES’s of the limits of nuclear struc- ture harmonic oscillator, axially symmetric rotor and deformed -soft and discussed in framework of the general geometric collective model (GCM. Also the shape phase transitions linking the three dynamical symmetries are studied taking into account only three parameters in the PES’s. The model is tested for the case of 238 92 U , which shows a more prolate behavior. The optimized model parameters have been adjusted by fit- ting procedure using a simulated search program in order to reproduce the experimental excitation energies in the ground state band up to 6 + and the two neutron separation energies.
Battaglia, Maurizio; ,; Peter, F.; Murray, Jessica R.
2013-01-01
This manual provides the physical and mathematical concepts for selected models used to interpret deformation measurements near active faults and volcanic centers. The emphasis is on analytical models of deformation that can be compared with data from the Global Positioning System (GPS) receivers, Interferometric synthetic aperture radar (InSAR), leveling surveys, tiltmeters and strainmeters. Source models include pressurized spherical, ellipsoidal, and horizontal penny-shaped geometries in an elastic, homogeneous, flat half-space. Vertical dikes and faults are described following the mathematical notation for rectangular dislocations in an elastic, homogeneous, flat half-space. All the analytical expressions were verified against numerical models developed by use of COMSOL Multyphics, a Finite Element Analysis software (http://www.comsol.com). In this way, typographical errors present were identified and corrected. Matlab scripts are also provided to facilitate the application of these models.
Directory of Open Access Journals (Sweden)
DR.S.C.JAYSWAL
2011-07-01
Full Text Available This experimental work presents a technique to determine the better surface quality by controlling the surface roughness and geometrical error. In machining operations, achieving desired surface quality features of the machined product is really a challenging job. Because, these quality features are highly correlated and areexpected to be influenced directly or indirectly by the direct effect of process parameters or their interactive effects. Thus The four input process parameters such as spindle speed, depth of cut, feed rate, and stepover have been selected to minimize the surface roughness and geometrical error simultaneously by using the robustdesign concept of Taguchi L9(34 method coupled with Response surface concept. Mathematical models for surface roughness and geometrical error were obtained from response surface analysis to predict values of surface roughness and geometrical error. S/N ratio and ANOVA analyses were also performed to obtain for significant parameters influencing surface roughness and geometrical error.
A dynamic stall model for airfoils with deformable trailing edges
DEFF Research Database (Denmark)
Andersen, Peter Bjørn; Gaunaa, Mac; Bak, Dan Christian
2007-01-01
on an airfoil section undergoing arbitrary motion in heave, lead-lag, pitch, Trailing Edge (TE) flapping. In the linear region, the model reduces to the inviscid model of Gaunaa [4], which includes the aerodynamic effect of a thin airfoil with a deformable camberline in inviscid flow. Therefore, the proposed......The present work contains an extension of the Beddoes-Leishman (B-L) type dynamic stall model, as described by Hansen et al. [7]. In this work a Deformable Trailing Edge Geometry (DTEG) has been added to the dynamic stall model. The model predicts the unsteady aerodynamic forces and moments...
An improved measurement model of binocular vision using geometrical approximation
Wang, Qiyue; Wang, Zhongyu; Yao, Zhenjian; Forrest, Jeffrey; Zhou, Weihu
2016-12-01
In order to improve the precision of a binocular vision measurement system, an effective binocular vision measurement method, named geometrical approximation, is proposed. This method can optimize the measurement results by geometrical approximation operation based on the principles of optimization theory and spatial geometry. To evaluate the properties of the proposed method, both simulative and practical experiments are carried out. The influence of image noise and focal length error on measurement results is discussed. The results show that measurement performance of the proposed method is manifested well. Besides, the proposed method is also compared with Bundle adjustment and least squares method in a practical experiment. The experiment results indicate that the average error, calculated by using the proposed method, is 0.076 mm less than Bundle adjustment’s 0.085 mm, and only half of the least squares method’s 0.146 mm. At the meantime, the proposed method enjoys a high level of computational efficiency when compared to Bundle adjustment. Since no nonlinear iteration optimization is involved, this method can be applied readily to real time on-line measurements.
Fluctuating Nonlinear Spring Model of Mechanical Deformation of Biological Particles
Kononova, Olga; Marx, Kenneth A; Wuite, Gijs J L; Roos, Wouter H; Barsegov, Valeri
2015-01-01
We present a new theory for modeling forced indentation spectral lineshapes of biological particles, which considers non-linear Hertzian deformation due to an indenter-particle physical contact and bending deformations of curved beams modeling the particle structure. The bending of beams beyond the critical point triggers the particle dynamic transition to the collapsed state, an extreme event leading to the catastrophic force drop as observed in the force (F)-deformation (X) spectra. The theory interprets fine features of the spectra: the slope of the FX curves and the position of force-peak signal, in terms of mechanical characteristics --- the Young's moduli for Hertzian and bending deformations E_H and E_b, and the probability distribution of the maximum strength with the strength of the strongest beam F_b^* and the beams' failure rate m. The theory is applied to successfully characterize the $FX$ curves for spherical virus particles --- CCMV, TrV, and AdV.
Integrability of the η-deformed Neumann-Rosochatius model
Arutyunov, Gleb; Heinze, Martin; Medina-Rincon, Daniel
2017-01-01
An integrable deformation of the well-known Neumann-Rosochatius system is studied by considering generalised bosonic spinning solutions on the η-deformed \\text{Ad}{{\\text{S}}5}× {{\\text{S}}5} background. For this integrable model we construct a 4× 4 Lax representation and a set of integrals of motion that ensures its Liouville integrability. These integrals of motion correspond to the deformed analogues of the Neumann-Rosochatius integrals and generalise the previously found integrals for the η-deformed Neumann and {{≤ft(\\text{Ad}{{\\text{S}}5}× {{\\text{S}}5}\\right)}η} geodesic systems. Finally, we briefly comment on consistent truncations of this model.
Fluctuating Nonlinear Spring Model of Mechanical Deformation of Biological Particles.
Directory of Open Access Journals (Sweden)
Olga Kononova
2016-01-01
Full Text Available The mechanical properties of virus capsids correlate with local conformational dynamics in the capsid structure. They also reflect the required stability needed to withstand high internal pressures generated upon genome loading and contribute to the success of important events in viral infectivity, such as capsid maturation, genome uncoating and receptor binding. The mechanical properties of biological nanoparticles are often determined from monitoring their dynamic deformations in Atomic Force Microscopy nanoindentation experiments; but a comprehensive theory describing the full range of observed deformation behaviors has not previously been described. We present a new theory for modeling dynamic deformations of biological nanoparticles, which considers the non-linear Hertzian deformation, resulting from an indenter-particle physical contact, and the bending of curved elements (beams modeling the particle structure. The beams' deformation beyond the critical point triggers a dynamic transition of the particle to the collapsed state. This extreme event is accompanied by a catastrophic force drop as observed in the experimental or simulated force (F-deformation (X spectra. The theory interprets fine features of the spectra, including the nonlinear components of the FX-curves, in terms of the Young's moduli for Hertzian and bending deformations, and the structural damage dependent beams' survival probability, in terms of the maximum strength and the cooperativity parameter. The theory is exemplified by successfully describing the deformation dynamics of natural nanoparticles through comparing theoretical curves with experimental force-deformation spectra for several virus particles. This approach provides a comprehensive description of the dynamic structural transitions in biological and artificial nanoparticles, which is essential for their optimal use in nanotechnology and nanomedicine applications.
Energy Technology Data Exchange (ETDEWEB)
Cheung, Y; Sawant, A [UT Southwestern Medical Center, Dallas, TX (United States)
2014-06-15
Purpose: Most clinically-deployed strategies for respiratory motion management in lung radiotherapy (e.g., gating, tracking) use external markers that serve as surrogates for tumor motion. However, typical lung phantoms used to validate these strategies are rigid-exterior+rigid-interior or rigid-exterior+deformable-interior. Neither class adequately represents the human anatomy, which is deformable internally as well as externally. We describe the construction and experimental validation of a more realistic, externally- and internally-deformable, programmable lung phantom. Methods: The outer shell of a commercially-available lung phantom (RS- 1500, RSD Inc.) was used. The shell consists of a chest cavity with a flexible anterior surface, and embedded vertebrae, rib-cage and sternum. A 3-axis platform was programmed with sinusoidal and six patient-recorded lung tumor trajectories. The platform was used to drive a rigid foam ‘diaphragm’ that compressed/decompressed the phantom interior. Experimental characterization comprised of mapping the superior-inferior (SI) and anterior-posterior (AP) trajectories of external and internal radioopaque markers with kV x-ray fluoroscopy and correlating these with optical surface monitoring using the in-room VisionRT system. Results: The phantom correctly reproduced the programmed motion as well as realistic effects such as hysteresis. The reproducibility of marker trajectories over multiple runs for sinusoidal as well as patient traces, as characterized by fluoroscopy, was within 0.4 mm RMS error for internal as well as external markers. The motion trajectories of internal and external markers as measured by fluoroscopy were found to be highly correlated (R=0.97). Furthermore, motion trajectories of arbitrary points on the deforming phantom surface, as recorded by the VisionRT system also showed a high correlation with respect to the fluoroscopically-measured trajectories of internal markers (R=0.92). Conclusion: We have
A dynamic stall model for airfoils with deformable trailing edges
DEFF Research Database (Denmark)
Andersen, Peter Bjørn; Gaunaa, Mac; Bak, Christian;
2009-01-01
, lead-lag, pitch, trailing-edge flapping. In the linear region, the model reduces to the inviscid model, which includes the aerodynamic effect of a thin airfoil with a deformable camberline in inviscid flow. Therefore, the proposed model can be considered a crossover between the work of Gaunaa...... for the attached flow region and Hansen et al. The model is compared qualitatively to wind tunnel measurements of a Riso/ B1-18 blade section equipped with deformable trailing-edge flap devices in the form of piezoelectric devices. Copyright © 2009 John Wiley & Sons, Ltd....
Deformed Calogero-Sutherland model and fractional quantum Hall effect
Atai, Farrokh; Langmann, Edwin
2017-01-01
The deformed Calogero-Sutherland (CS) model is a quantum integrable system with arbitrary numbers of two types of particles and reducing to the standard CS model in special cases. We show that a known collective field description of the CS model, which is based on conformal field theory (CFT), is actually a collective field description of the deformed CS model. This provides a natural application of the deformed CS model in Wen's effective field theory of the fractional quantum Hall effect (FQHE), with the two kinds of particles corresponding to electrons and quasi-hole excitations. In particular, we use known mathematical results about super-Jack polynomials to obtain simple explicit formulas for the orthonormal CFT basis proposed by van Elburg and Schoutens in the context of the FQHE.
Deformed single-particle levels in the boson-fermion model
Energy Technology Data Exchange (ETDEWEB)
Leviatan, A.; Shao, B. (Center for Theoretical Physics, Sloane Laboratory, Yale University, New Haven, Connecticut 06511 (US) Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (US))
1989-11-13
Deformed single-particle levels are derived from a boson-fermion Hamiltonian in which the odd fermion occupies several {ital j} orbits. The geometric-oriented approach applied to {sup 169}Tm clarified the role of algebraic interactions and provides an intuitive interpretation and guidance to numerical calculations in deformed nuclei.
Transient Analysis of Hysteresis Queueing Model Using Matrix Geometric Method
Directory of Open Access Journals (Sweden)
Wajiha Shah
2011-10-01
Full Text Available Various analytical methods have been proposed for the transient analysis of a queueing system in the scalar domain. In this paper, a vector domain based transient analysis is proposed for the hysteresis queueing system with internal thresholds for the efficient and numerically stable analysis. In this system arrival rate of customer is controlled through the internal thresholds and the system is analyzed as a quasi-birth and death process through matrix geometric method with the combination of vector form Runge-Kutta numerical procedure which utilizes the special matrices. An arrival and service process of the system follows a Markovian distribution. We analyze the mean number of customers in the system when the system is in transient state against varying time for a Markovian distribution. The results show that the effect of oscillation/hysteresis depends on the difference between the two internal threshold values.
Modeling for Deformable Body and Motion Analysis: A Review
Directory of Open Access Journals (Sweden)
Hailang Pan
2013-01-01
Full Text Available This paper surveys the modeling methods for deformable human body and motion analysis in the recent 30 years. First, elementary knowledge of human expression and modeling is introduced. Then, typical human modeling technologies, including 2D model, 3D surface model, and geometry-based, physics-based, and anatomy-based approaches, and model-based motion analysis are summarized. Characteristics of these technologies are analyzed. The technology accumulation in the field is outlined for an overview.
Static deformation modeling and analysis of flexure hinges made of a shape memory alloy
Du, Zhijiang; Yang, Miao; Dong, Wei; Zhang, Dan
2016-11-01
The flexure hinge is a key element in compliant mechanisms to achieve continuous motion; however the motion range of a flexure hinge is severely restricted by the material’s allowable strain. Due to the superelasticity effect, shape memory alloys (SMAs) can undergo much larger strain than other metals; this means that they are excellent candidates for the fabrication of flexure hinges with a large motion range. In this paper, a simple static deformation modeling approach is proposed for a flexure hinge made of a SMA. The superelastic behavior of the SMA is described by Brinson’s constitutive model. The flexure hinge is considered as a non-prismatic cantilever beam associated with geometrical and material nonlinearities. Govern equations of the flexure hinge are derived and solved numerically by applying the nonlinear bending theory of the Euler-Bernoulli beam. Experimental tests show that the proposed modeling approach can predict the deformation of the flexure hinge precisely; the maximum relative error is less than 6.5%. Based on the static deformation model, the motion capacity, the stiffness characteristic and the rotational error of the flexure hinge are also investigated. The results reveal that the flexure hinge made of a SMA has great potential to construct compliant mechanisms with a large motion range.
Institute of Scientific and Technical Information of China (English)
ZHOU; Jianxun; ZHOU; Jiansheng
2006-01-01
The Bohai Basin is a Cenozoic petroliferous extensional basin in China and has apparent geometrical and kinematic similarities with the other Meso-Cenozoic extensional basins located along the eastern margin of Eurasian Plate. However, the deformation mechanisms of the basin are still in dispute. Physcial modelling referring to the Huanghua Depression, located in the central part of the Bohai Basin was conducted employing four sets of planar sandbox experimental models with different extension directions. Only experimental results of the model with N-S extension show good structural similarity with the depression. The results also indicate that complex variations of fault strike in a rift basin are not necessarily the results of complex kinematic mechanisms or polyphase deformation. Based on comparison of experimental results with the actual structures and the good structural similarity between Huanghua Depression and the whole Bohai Basin, it is concluded that the Bohai Basin was formed by the N-S extension. The strike slip deformation along the NNE-trending border faults of the basin resulted from the N-S extension and played the role of lateral transformation for the N-S extension. In addition, according to the apparent geometrical and kinematic similarities among the Bohai Basin and other Meso-Cenozoic extensional basins located along the eastern margin of the Eurasian Plate, it is proposed that: (1) this "N-S extension" model provides a better kinematic interpretation for the formation of Bohai Basin and the other adjacent basins located along the eastern margin of the Eurasian Plate; and (2) the N-S extension was probably the effect of the "slab window" formed by the subduction of the nearly E-W trending oceanic ridge between the Kula and Pacific Plates. The "slab window" effect can also provide reasonable explanations for the phenomena that initial rifting ages of basins become progressively younger westwards along the eastern margin of the Eurasian Plate
RHEOLOGICAL DEFORMATION BEHAVIOR MODEL OF SUGAR DOUGH IN THE CONDITIONS OF MONOAXIAL COMPRESSION
Directory of Open Access Journals (Sweden)
G. O. Magomedov
2014-01-01
Full Text Available Summary. The knowledge of regularities of deformation behavior of the processed confectionery masses with certain rheological properties allows to calculate parameters of shaping process and to select processing equipment for its carrying out. The article studies the obtaining of the rheological equation of deformation behavior of sugar dough in the conditions of monoaxial compression which is realized in sugar cookies dough pieces formation processes. The results of the pilot studies confirming adequacy of the offered rheological equation are presented. The behavior of an elastic-, viscous- and plastic body in the conditions of quasistatic test for creeping during which the set size is tension, and the measured one is relative deformation is considered. The main rheological properties of sugar dough received experimentally are given. Values of rheological constants are received and it is revealed that at 95% confidential probability, the rheological equation for the general deformation of an elastic-, viscous- and plastic body adequately describes experimental data. The maximum fault thus makes 2,3%. It is established that dough pieces shaping processes from the sugar dough possessing visco- and plastic properties should be realized at an external tension (power impact from the forming body which exceeds a limit of fluidity of the dough formed. The level of external tension, as well as the duration of its influence (that is formation duration should be chosen taking into account the residual deformations in the processed mass which guarantee giving of a certain geometrical form and drawing on a surface of dough pieces. The rheological model of sugar dough allows to predict its deformation behavior in the formation conditions, and to calculate the parameters of sugar dough formation process.
Modeling steel deformation in the semi-solid state
Hojny, Marcin
2017-01-01
This book addresses selected aspects of steel-deformation modelling, both at very high temperatures and under the conditions in which the liquid and the solid phases coexist. Steel-deformation modelling with its simultaneous solidification is particularly difficult due to its specificity and complexity. With regard to industrial applications and the development of new, integrated continuous casting and rolling processes, the issues related to modelling are becoming increasingly important. Since the numerous industrial tests that are necessary when traditional methods are used to design the process of continuous casting immediately followed by rolling are expensive, new modelling concepts have been sought. Comprehensive tests were applied to solve problems related to the deformation of steel with a semi-solid core. Physical tests using specialist laboratory instruments (Gleeble 3800thermo-mechanical simulator, NANOTOM 180 N computer tomography, Zwick Z250 testing equipment, 3D blue-light scanning systems), and...
Wess-Zumino Terms for the Deformed Skyrme Model
Neves, C; Neves, Clifford; Wotzasek, Clovis
2000-01-01
A formulation of Skyrme model as an embedded gauge theory with the constraint deformed away from the spherical geometry is proposed. The gauge invariant formulation is obtained firstly generalizing the intrinsic geometry of the model and then converting the constraint to first-class through an iterative Wess-Zumino procedure. The gauge invariant model is quantized via Dirac method for first-class system. A perturbative calculation provides new free parameters related to deformation that improve the energy spectrum obtained in earlier approaches.
On hydrological model complexity, its geometrical interpretations and prediction uncertainty
Arkesteijn, E.C.M.M.; Pande, S.
2013-01-01
Knowledge of hydrological model complexity can aid selection of an optimal prediction model out of a set of available models. Optimal model selection is formalized as selection of the least complex model out of a subset of models that have lower empirical risk. This may be considered equivalent to
Geometrical Modeling of Woven Fabrics Weavability-Limit New Relationships
Directory of Open Access Journals (Sweden)
Dalal Mohamed
2017-03-01
Full Text Available The weavability limit and tightness for 2D and 3D woven fabrics is an important factor and depends on many geometric parameters. Based on a comprehensive review of the literature on textile fabric construction and property, and related research on fabric geometry, a study of the weavability limit and tightness relationships of 2D and 3D woven fabrics was undertaken. Experiments were conducted on a representative number of polyester and cotton woven fabrics which have been woven in our workshop, using three machines endowed with different insertion systems (rapier, projectiles and air jet. Afterwards, these woven fabrics have been analyzed in the laboratory to determine their physical and mechanical characteristics using air permeability-meter and KES-F KAWABATA Evaluation System for Fabrics. In this study, the current Booten’s weavability limit and tightness relationships based on Ashenhurst’s, Peirce’s, Love’s, Russell’s, Galuszynskl’s theory and maximum-weavability is reviewed and modified as new relationships to expand their use to general cases (2D and 3D woven fabrics, all fiber materiel, all yarns etc…. The theoretical relationships were examined and found to agree with experimental results. It was concluded that the weavability limit and tightness relationships are useful tools for weavers in predicting whether a proposed fabric construction was weavable and also in predicting and explaining their physical and mechanical properties.
A Deformable Template Model, with Special Reference to Elliptical Templates
DEFF Research Database (Denmark)
Hobolth, Asger; Pedersen, Jan; Jensen, Eva Bjørn Vedel
2002-01-01
This paper suggests a high-level continuous image model for planar star-shaped objects. Under this model, a planar object is a stochastic deformation of a star-shaped template. The residual process, describing the difference between the radius-vector function of the template and the object...
Personalized heterogeneous deformable model for fast volumetric registration.
Si, Weixin; Liao, Xiangyun; Wang, Qiong; Heng, Pheng Ann
2017-02-20
Biomechanical deformable volumetric registration can help improve safety of surgical interventions by ensuring the operations are extremely precise. However, this technique has been limited by the accuracy and the computational efficiency of patient-specific modeling. This study presents a tissue-tissue coupling strategy based on penalty method to model the heterogeneous behavior of deformable body, and estimate the personalized tissue-tissue coupling parameters in a data-driven way. Moreover, considering that the computational efficiency of biomechanical model is highly dependent on the mechanical resolution, a practical coarse-to-fine scheme is proposed to increase runtime efficiency. Particularly, a detail enrichment database is established in an offline fashion to represent the mapping relationship between the deformation results of high-resolution hexahedral mesh extracted from the raw medical data and a newly constructed low-resolution hexahedral mesh. At runtime, the mechanical behavior of human organ under interactions is simulated with this low-resolution hexahedral mesh, then the microstructures are synthesized in virtue of the detail enrichment database. The proposed method is validated by volumetric registration in an abdominal phantom compression experiments. Our personalized heterogeneous deformable model can well describe the coupling effects between different tissues of the phantom. Compared with high-resolution heterogeneous deformable model, the low-resolution deformable model with our detail enrichment database can achieve 9.4× faster, and the average target registration error is 3.42 mm, which demonstrates that the proposed method shows better volumetric registration performance than state-of-the-art. Our framework can well balance the precision and efficiency, and has great potential to be adopted in the practical augmented reality image-guided robotic systems.
Forward and inverse modelling of post-seismic deformation
Crawford, Ophelia; Al-Attar, David; Tromp, Jeroen; Mitrovica, Jerry X.
2016-11-01
We consider a new approach to both the forward and inverse problems in post-seismic deformation. We present a method for forward modelling post-seismic deformation in a self-gravitating, heterogeneous and compressible earth with a variety of linear and non-linear rheologies. We further demonstrate how the adjoint method can be applied to the inverse problem both to invert for rheological structure and to calculate the sensitivity of a given surface measurement to changes in rheology or time-dependence of the source. Both the forward and inverse aspects are illustrated with several numerical examples implemented in a spherically symmetric earth model.
Forward and inverse modelling of post-seismic deformation
Crawford, Ophelia; Al-Attar, David; Tromp, Jeroen; Mitrovica, Jerry X.
2017-02-01
We consider a new approach to both the forward and inverse problems in post-seismic deformation. We present a method for forward modelling post-seismic deformation in a self-gravitating, heterogeneous and compressible earth with a variety of linear and nonlinear rheologies. We further demonstrate how the adjoint method can be applied to the inverse problem both to invert for rheological structure and to calculate the sensitivity of a given surface measurement to changes in rheology or time-dependence of the source. Both the forward and inverse aspects are illustrated with several numerical examples implemented in a spherically symmetric earth model.
Mask synthesis and verification based on geometric model for surface micro-machined MEMS
Institute of Scientific and Technical Information of China (English)
LI Jian-hua; LIU Yu-sheng; GAO Shu-ming
2005-01-01
Traditional MEMS (microelectromechanical system) design methodology is not a structured method and has become an obstacle for MEMS creative design. In this paper, a novel method of mask synthesis and verification for surface micro-machined MEMS is proposed, which is based on the geometric model of a MEMS device. The emphasis is focused on synthesizing the masks at the basis of the layer model generated from the geometric model of the MEMS device. The method is comprised of several steps: the correction of the layer model, the generation of initial masks and final masks including multi-layer etch masks, and mask simulation. Finally some test results are given.
The effects of geometric uncertainties on computational modelling of knee biomechanics.
Meng, Qingen; Fisher, John; Wilcox, Ruth
2017-08-01
The geometry of the articular components of the knee is an important factor in predicting joint mechanics in computational models. There are a number of uncertainties in the definition of the geometry of cartilage and meniscus, and evaluating the effects of these uncertainties is fundamental to understanding the level of reliability of the models. In this study, the sensitivity of knee mechanics to geometric uncertainties was investigated by comparing polynomial-based and image-based knee models and varying the size of meniscus. The results suggested that the geometric uncertainties in cartilage and meniscus resulting from the resolution of MRI and the accuracy of segmentation caused considerable effects on the predicted knee mechanics. Moreover, even if the mathematical geometric descriptors can be very close to the imaged-based articular surfaces, the detailed contact pressure distribution produced by the mathematical geometric descriptors was not the same as that of the image-based model. However, the trends predicted by the models based on mathematical geometric descriptors were similar to those of the imaged-based models.
Hooper, Andrew John
While conventional interferometric synthetic aperture radar (InSAR) is a very effective technique for measuring crustal deformation, almost any interferogram includes large areas where the signals decorrelate and no measurement is possible. Consequently, most InSAR studies to date have focused on areas that are dry and sparsely vegetated. A relatively new analysis technique, permanent scatterer InSAR, overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms. This technique has been useful for analysis of urban areas, where angular structures produce efficient reflectors that dominate background scattering. However, man-made structures are absent from most of the Earth's surface. Furthermore, this technique requires, a priori, an approximate temporal model for the deformation, whereas characterizing the temporal pattern of deformation is commonly one of the aims of any study. We have developed a new method of analysis, StaMPS, using spatial correlation of interferogram phase to find a network of stable pixels in all terrains, with or without buildings. Prior knowledge of temporal variations in the deformation rate is not required. We refer to these pixels as persistent scatterers (PS). A key component of our method is the development of two algorithms to unwrap a three-dimensional series of interferograms. We observe temporally-variable deformation, using an initial version of StaMPS, in data acquired over Long Valley caldera in California, for a period when deformation rates varied significantly. The inferred displacements of the PS compare well with ground truth. Using an enhanced version of StaMPS, we detect a period of steady deflation within the Volcan Alcedo caldera in the Galapagos Islands between 1997 and 2001, which we model with a contracting ellipsoidal magma body. Conventional InSAR has been limited here until now by high rates of temporal decorrelation over much of
Multi-Mode GF-3 Satellite Image Geometric Accuracy Verification Using the RPC Model.
Wang, Taoyang; Zhang, Guo; Yu, Lei; Zhao, Ruishan; Deng, Mingjun; Xu, Kai
2017-09-01
The GaoFen-3 (GF-3) satellite is the first C-band multi-polarization synthetic aperture radar (SAR) imaging satellite with a resolution up to 1 m in China. It is also the only SAR satellite of the High-Resolution Earth Observation System designed for civilian use. There are 12 different imaging models to meet the needs of different industry users. However, to use SAR satellite images for related applications, they must possess high geometric accuracy. In order to verify the geometric accuracy achieved by the different modes of GF-3 images, we analyze the SAR geometric error source and perform geometric correction tests based on the RPC model with and without ground control points (GCPs) for five imaging modes. These include the spotlight (SL), ultra-fine strip (UFS), Fine Strip I (FSI), Full polarized Strip I (QPSI), and standard strip (SS) modes. Experimental results show that the check point residuals are large and consistent without GCPs, but the root mean square error of the independent checkpoints for the case of four corner control points is better than 1.5 pixels, achieving a similar level of geometric positioning accuracy to that of international satellites. We conclude that the GF-3 satellite can be used for high-accuracy geometric processing and related industry applications.
Energy Technology Data Exchange (ETDEWEB)
Huang Mingxin, E-mail: mingxin.huang@arcelormittal.com [Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS, Delft (Netherlands); Rivera-Diaz-del-Castillo, Pedro E.J. [Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS, Delft (Netherlands); Bouaziz, Olivier [ArcelorMittal Research, Voie Romaine-BP30320, 57283 Maizieres-les-Metz Cedex (France); Zwaag, Sybrand van der [Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS, Delft (Netherlands)
2009-07-15
A new unified description for the steady state deformation stress in single and polycrystalline metals and for various deformation conditions is presented. The new formulation for dislocation controlled deformation stems from the field of irreversible thermodynamics. The model applies to conditions of dynamic recovery as well as dynamic recrystallization and has been validated for constant strain rate and creep loading conditions. Unlike existing approaches, the new model captures transitions between deformation mechanisms within a single formulation. For conditions of dynamic recrystallization, the average dislocation density is found to be a function of the shear strain rate and a term combining the dislocation climb velocity and the grain boundary velocity.
Mathematical models of carbon-carbon composite deformation
Golovin, N. N.; Kuvyrkin, G. N.
2016-09-01
Mathematical models of carbon-carbon composites (CCC) intended for describing the processes of deformation of structures produced by using CCC under high-temperature loading are considered. A phenomenological theory of CCC inelastic deformation is proposed, where such materials are considered as homogeneous ones with effective characteristics and where their high anisotropy of mechanical characteristics and different ways of resistance to extension and compression are taken into account. Micromechanical models are proposed for spatially reinforced CCC, where the difference between mechanical characteristics of components and the reinforcement scheme are taken into account. Themodel parameters are determined from the results of experiments of composite macrospecimens in the directions typical of the material. A version of endochronictype theory with several internal times "launched" for each composite component and related to some damage accumulation mechanisms is proposed for describing the inelastic deformation. Some practical examples are considered.
An immersed-boundary method for modeling flow of deformable blood cells in complex geometry
Balogh, Peter; Bagchi, Prosenjit
2016-11-01
We present a computational methodology for simulating blood flow at the cellular scale in highly complex geometries, such as microvascular networks. Immersed boundary methods provide the foundation for our approach, as they allow modeling flows in arbitrary geometries, in addition to resolving the large deformation and dynamics of individual blood cell with high fidelity. Different simulation components are seamlessly integrated into the present methodology that can simultaneously model stationary rigid boundaries of arbitrary and complex shape, moving rigid bodies, and highly deformable interfaces of blood cells that are governed by non-linear elasticity. This permits physiologically realistic simulations of blood cells flowing in complex microvascular networks characterized by multiple bifurcating and merging vessels. The methodology is validated against analytical theory, experimental data, and previous numerical results. We then demonstrate the capabilities of the methodology by simulating deformable blood cells and heterogeneous cell suspensions flowing in both physiologically realistic microvascular networks and geometrically intricate microfluidic devices. The methodology offers the potential of scaling up to large microvascular networks at organ levels. Funded by NSF CBET 1604308.
Numerical Modeling of Exploitation Relics and Faults Influence on Rock Mass Deformations
Wesołowski, Marek
2016-12-01
This article presents numerical modeling results of fault planes and exploitation relics influenced by the size and distribution of rock mass and surface area deformations. Numerical calculations were performed using the finite difference program FLAC. To assess the changes taking place in a rock mass, an anisotropic elasto-plastic ubiquitous joint model was used, into which the Coulomb-Mohr strength (plasticity) condition was implemented. The article takes as an example the actual exploitation of the longwall 225 area in the seam 502wg of the "Pokój" coal mine. Computer simulations have shown that it is possible to determine the influence of fault planes and exploitation relics on the size and distribution of rock mass and its surface deformation. The main factor causing additional deformations of the area surface are the abandoned workings in the seam 502wd. These abandoned workings are the activation factor that caused additional subsidences and also, due to the significant dip, they are a layer on which the rock mass slides down in the direction of the extracted space. These factors are not taken into account by the geometrical and integral theories.
Modeling of Photoinduced Deformation in Silicon Microcantilever
Directory of Open Access Journals (Sweden)
MinHang Bao
2007-09-01
Full Text Available A model for prediction the photostriction effect in silicon microcantilevers is built up based on the fundamentals of mechanics and semiconductor physics. By considering the spatial distribution and surface recombination of photoinduced carriers in silicon, the model interprets the cause of the photoinduced bending. The results from our model much more closely approximate the experimental values than the former model built up by Datskos, Rajic and Datskou [1](APL, Vol.73 (1998 No.16, pp 3219-2321, represented by the reduction of the error between calculation and measurement from 25 times to 0.85 times.
Design developing conceptual models blade with geometric combined surface
Juraev, T. H.; Bukhara Technological Institute of Engineering, Bukhara
2013-01-01
A conceptual model of the blade using the methods of geometricmodeling principles of industrial design and CAD technologies. Variants are functional use of the proposed model for various working bodies.
Procedures for Geometric Data Reduction in Solid Log Modelling
Luis G. Occeña; Wenzhen Chen; Daniel L. Schmoldt
1995-01-01
One of the difficulties in solid log modelling is working with huge data sets, such as those that come from computed axial tomographic imaging. Algorithmic procedures are described in this paper that have successfully reduced data without sacrificing modelling integrity.
Bartlewska-Urban, Monika; Zombroń, Marek; Strzelecki, Tomasz
2016-03-01
The following study presents numerical calculations for establishing the impact of temperature changes on the process of distortion of bi-phase medium represented using Biot consolidation equations with Kelvin-Voigt rheological skeleton presented, on the example of thermo-consolidation of a pavement of expressway S17. We analyzed the behavior of the expressway under the action of its own weight, dynamic load caused by traffic and temperature gradient. This paper presents the application of the Biot consolidation model with the Kelvin-Voigt skeleton rheological characteristics and the influence of temperature on the deformation process is taken into account. A three-dimensional model of the medium was created describing the thermal consolidation of a porous medium. The 3D geometrical model of the area under investigation was based on data obtained from the land surveying and soil investigation of a 200 m long section of the expressway and its shoulders.
The Geometric Modelling of Furniture Parts and Its Application
Institute of Scientific and Technical Information of China (English)
张福炎; 蔡士杰; 王玉兰; 居正文
1989-01-01
In this paper, a 3-D solid modelling method appropriate for the design of furniture parts, which has been used in FCAD (Computer Aided Design for Furniture Structure )system, is introduced. Some interactive functions for modifying part models and deriving a variety of practical parts are described. Finally. the application of the modelling method to computer aided manufacturing of furniture parts is prospected.
A simple numerical model of a geometrically nonlinear Timoshenko beam
Keijdener, C.; Metrikine, A.
2015-01-01
In the original problem for which this model was developed, onedimensional flexible objects interact through a non-linear contact model. Due to the non-linear nature of the contact model, a numerical time-domain approach was adopted. One of the goals was to see if the coupling between axial and tran
Matrix model description of baryonic deformations
Energy Technology Data Exchange (ETDEWEB)
Bena, Iosif; Murayama, Hitoshi; Roiban, Radu; Tatar, Radu
2003-03-13
We investigate supersymmetric QCD with N{sub c} + 1 flavors using an extension of the recently proposed relation between gauge theories and matrix models.The impressive agreement between the two sides provides a beautiful confirmation of the extension of the gauge theory-matrix model relation to this case.
Institute of Scientific and Technical Information of China (English)
LI Zhanli; SUN Xiuying
2006-01-01
VRML(Virtual Reality Modeling Language) format as an international standard for virtual reality, has already been widely adopted for graphical representation of 3D objects over the Web. Adopting VRML model in RP(Rapid Prototyping) can reduce the precision loss which is caused by triangulation in generating STL file. Hence exploring a slicing method and developing a slicing software for VRML model is important and significant to improve the accuracy of RP products. Finding intersections of a plane and VRML model is the key operation in slicing algorithm. This paper presents a method for calculating the intersections between a set of parallel planes and VRML geometric primitives. Based on the analysis of the relative position between a plane and a geometric primitive, intersection conditions in all cases were obtained, and the geometric parameters and corresponding equations of intersections were derived. The algorithm had been tested, and applications show that it is robust and effective.
Observation of Schramm-Loewner evolution on the geometrical clusters of the Ising model
Najafi, M. N.
2015-05-01
Schramm-Loewner Evolution (SLE) is a stochastic process that, by focusing on the geometrical features of the two-dimensional (2D) conformal invariant models, classifies them using one real parameter κ. In this work we apply the SLE formalism to the exterior frontiers of the geometrical clusters (interfaces) of the two-dimensional critical Ising model on the triangular lattice. We first analyze the critical curves going from the real axis to the real axis in the upper half plane geometry and show numerically that SLE(κ, κ - 6) works well to extract the diffusivity parameter κ. We then analyze the conformal loops of the critical Ising model. After determining some geometrical exponents of the critical loops as the interfaces of the model in hand, we address the problem of application of SLE to conformal loops. We numerically show that SLE(κ, κ - 6) is more reliable than previous methods.
Fixing Geometric Errors on Polygonal Models: A Survey
Institute of Scientific and Technical Information of China (English)
Tao Ju
2009-01-01
Polygonal models are popular representations of 3D objects. The use of polygonal models in computational applications often requires a model to properly bound a 3D solid. That is, the polygonal model needs to be closed, manifold, and free of self-intersections. This paper surveys a sizeable literature for repairing models that do not satisfy this criteria, focusing on categorizing them by their methodology and capability. We hope to offer pointers to further readings for researchers and practitioners, and suggestions of promising directions for future research endeavors.
η and λ deformations as E-models
Directory of Open Access Journals (Sweden)
Ctirad Klimčík
2015-11-01
Full Text Available We show that the so-called λ deformed σ-model as well as the η deformed one belong to a class of the E-models introduced in the context of the Poisson–Lie-T-duality. The λ and η theories differ solely by the choice of the Drinfeld double; for the λ model the double is the direct product G×G while for the η model it is the complexified group GC. As a consequence of this picture, we prove for any G that the target space geometries of the λ-model and of the Poisson–Lie T-dual of the η-model are related by a simple analytic continuation.
Littelmann path model for geometric crystals, Whittaker functions on Lie groups and Brownian motion
Chhaibi, Reda
2013-02-01
Generally speaking, this thesis focuses on the interplay between the representations of Lie groups and probability theory. It subdivides into essentially three parts. In a first rather algebraic part, we construct a path model for geometric crystals in the sense of Berenstein and Kazhdan, for complex semi-simple Lie groups. We will mainly describe the algebraic structure, its natural morphisms and parameterizations. The theory of total positivity will play a particularly important role. Then, we anticipate on the probabilistic part by exhibiting a canonical measure on geometric crystals. It uses as ingredients the superpotential for the flag manifold and a measure invariant under the crystal actions. The image measure under the weight map plays the role of Duistermaat-Heckman measure. Its Laplace transform defines Whittaker functions, providing an interesting formula for all Lie groups. Then it appears clearly that Whittaker functions are to geometric crystals, what characters are to combinatorial crystals. The Littlewood-Richardson rule is also exposed. Finally we present the probabilistic approach that allows to find the canonical measure. It is based on the fundamental idea that the Wiener measure will induce the adequate measure on the algebraic structures through the path model. In the last chapter, we show how our geometric model degenerates to the continuous classical Littelmann path model and thus recover known results. For example, the canonical measure on a geometric crystal of highest weight degenerates into a uniform measure on a polytope, and recovers the parameterizations of continuous crystals.
Geometric Feature Extraction and Model Reconstruction Based on Scattered Data
Institute of Scientific and Technical Information of China (English)
胡鑫; 习俊通; 金烨
2004-01-01
A method of 3D model reconstruction based on scattered point data in reverse engineering is presented here. The topological relationship of scattered points was established firstly, then the data set was triangulated to reconstruct the mesh surface model. The curvatures of cloud data were calculated based on the mesh surface, and the point data were segmented by edge-based method; Every patch of data was fitted by quadric surface of freeform surface, and the type of quadric surface was decided by parameters automatically, at last the whole CAD model was created. An example of mouse model was employed to confirm the effect of the algorithm.
The Skin Deformation of a 3D Virtual Human
Institute of Scientific and Technical Information of China (English)
Xiao-Jing Zhou; Zheng-Xu Zhao
2009-01-01
This paper presents a skin deformation algorithm for creating 3D characters or virtual human models. The algorithm can be applied to rigid deformation, joint dependent localized deformation, skeleton driven deformation, cross contour deformation, and free-form deformation (FFD). These deformations are computed and demonstrated with examples and the algorithm is applied to overcome the difficulties in mechanically simulating the motion of the human body by club-shape models. The techniques described in this article enables the reconstruction of dynamic human models that can be used in defining and representing the geometrical and kinematical characteristics of human motion.
Abrosimov, N. A.
1999-11-01
Nonlinear three-dimensional problems of dynamic deformation, buckling, and posteritical behavior of composite shell structures under pulsed loads are analyzed. The structure is assumed to be made of rigidly joined plates and shells of revolution along the lines coinciding with the coordinate directions of the joined elements. Individual structural elements can be made of both composite and conventional isotropic materials. The kinematic model of deformation of the structural elements is based on Timoshenko-type hypotheses. This approach is oriented to the calculation of nonstationary deformation processes in composite structures under small deformations but large displacements and rotation angles, and is implemented in the context of a simplified version of the geometrically nonlinear theory of shells. The physical relations in the composite structural elements are based on the theory of effective moduli for individual layers or for the package as a whole, whereas in the metallic elements this is done in the framework of the theory of plastic flow. The equations of motion of a composite shell structure are derived based on the principle of virtual displacements with some additional conditions allowing for the joint operation of structural elements. To solve the initial boundary-value problem formulated, an efficient numerical method is developed based on the finite-difference discretization of variational equations of motion in space variables and an explicit second-order time-integration scheme. The permissible time-integration step is determined using Neumann's spectral criterion. The above method is especially efficient in calculating thin-walled shells, as well as in the case of local loads acting on the structural element, when the discretization grid has to be condensed in the zones of rapidly changing solutions in space variables. The results of analyzing the nonstationary deformation processes and critical loads are presented for composite and isotropic
Do Lumped-Parameter Models Provide the Correct Geometrical Damping?
DEFF Research Database (Denmark)
Andersen, Lars
2007-01-01
This paper concerns the formulation of lumped-parameter models for rigid footings on homogenous or stratified soil with focus on the horizontal sliding and rocking. Such models only contain a few degrees of freedom, which makes them ideal for inclusion in aero-elastic codes for wind turbines...
Do Lumped-Parameter Models Provide the Correct Geometrical Damping?
DEFF Research Database (Denmark)
Andersen, Lars
2007-01-01
This paper concerns the formulation of lumped-parameter models for rigid footings on homogenous or stratified soil with focus on the horizontal sliding and rocking. Such models only contain a few degrees of freedom, which makes them ideal for inclusion in aero-elastic codes for wind turbines...
A NEW DEFORMABLE MODEL USING LEVEL SETS FOR SHAPE SEGMENTALTION
Institute of Scientific and Technical Information of China (English)
He Ning; Zhang Peng; Lu Ke
2009-01-01
In this paper,we present a new deformable model for shape segmentation,which makes two modifications to the original level set implementation of deformable models.The modifications are motivated by difficulties that we have encountered in applying deformable models to segmentation of medical images.The level set algorithm has some advantages over the classical snake deformable models.However,it could develop large gaps in the boundary and holes within the objects.Such boundary gaps and holes of objects can cause inaccurate segmentation that requires manual correction.The proposed method in this paper possesses an inherent property to detect gaps and holes within the object with a single initial contour and also does not require specific initialization.The first modification is to replace the edge detector by some area constraint,and the second modification utilizes weighted length constraint to regularize the curve under evolution.The proposed method has been applied to both synthetic and real images with promising results.
Modeling dynamic recrystallization of olivine aggregates deformed in simple shear
Energy Technology Data Exchange (ETDEWEB)
Wenk, H.-R. [Department of Geology and Geophysics, University of California, Berkeley (United States); Tome, C. N. [Materials, Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico (United States)
1999-11-10
Experiments by Zhang and Karato [1995] have shown that in simple shear dislocation creep of olivine at low strains, an asymmetric texture develops with a [100] maximum rotated away from the shear direction against the sense of shear. At large strain where recrystallization is pervasive, the texture pattern is symmetrical, and [100] is parallel to the shear direction. The deformation texture can be adequately modeled with a viscoplastic self-consistent polycrystal plasticity theory. This model can be expanded to include recrystallization, treating the process as a balance of boundary migration (growth of relatively underformed grains at the expense of highly deformed grains) and nucleation (strain-free nuclei replacing highly deformed grains). If nucleation dominates over growth, the model predicts a change from the asymmetric to the symmetric texture as recrystallization proceeds and stabilization in the ''easy slip'' orientation for the dominant (010)[100] slip system. This result is in accordance with the experiments and suggests that the most highly deformed orientation components dominate the recrystallization texture. The empirical model will be useful to simulate more adequately the development of anisotropy in the mantle where olivine is largely recrystallized. (c) 1999 American Geophysical Union.
Holographic superconductor in a deformed four-dimensional STU model
Pourhassan, B
2016-01-01
In this paper, we consider deformed STU model in four dimension including both electric and magnetic charges. Using AdS/CFT we study holographic superconductor and obtain transport properties. We find that presence of magnetic charge is necessary to have maximum electrical conductivity. Also we show that thermal conductivity increases with magnetic charge.
Human supervisory approach to modeling industrial scenes using geometric primitives
Energy Technology Data Exchange (ETDEWEB)
Luck, J.P.; Little, C.Q.; Roberts, R.S.
1997-11-19
A three-dimensional world model is crucial for many robotic tasks. Modeling techniques tend to be either fully manual or autonomous. Manual methods are extremely time consuming but also highly accurate and flexible. Autonomous techniques are fast but inflexible and, with real-world data, often inaccurate. The method presented in this paper combines the two, yielding a highly efficient, flexible, and accurate mapping tool. The segmentation and modeling algorithms that compose the method are specifically designed for industrial environments, and are described in detail. A mapping system based on these algorithms has been designed. It enables a human supervisor to quickly construct a fully defined world model from unfiltered and unsegmented real-world range imagery. Examples of how industrial scenes are modeled with the mapping system are provided.
Metastable Vacua in Deformed N=2 Supersymmetric Models
Halyo, Edi
2009-01-01
We show that supersymmetric Abelian models that are obtained from deformations of those with ${\\cal N}=2$ supersymmetry also contain metastable vacua for a wide range of parameters. The deformations we consider are combinations of masses for charged and singlet fields, a singlet F--term and an anomalous D--term. We find that, in all cases, the nonsupersymmetric vacua are parametrically far from the supersymmetric ones and therefore metastable. Using retrofitting, we show that these metastable vacua may lead to semi--realistic phenomenology.
Duality in deformed coset fermionic models
Cabra, D C
1996-01-01
We study the SU(2)_k/U(1)-parafermion model perturbed by its first thermal operator. By formulating the theory in terms of a (perturbed) fermionic coset model we show that the model is equivalent to interacting WZW fields modulo free fields. In this scheme, the order and disorder operators of the Z_k parafermion theory are constructed as gauge invariant composites. We find that the theory presents a duality symmetry that interchanges the roles of the spin and dual spin operators. For two particular values of the coupling constant we find that the theory recovers conformal invariance and the gauge symmetry is enlarged. We also find a novel self-dual point.
Gauged spinning models with deformed supersymmetry
Fedoruk, Sergey
2016-01-01
New models of the SU(2|1) supersymmetric mechanics based on gauging the systems with dynamical (1,4,3) and semi-dynamical (4,4,0) supermultiplets are presented. We propose a new version of SU(2|1) harmonic superspace approach which makes it possible to construct the Wess-Zumino term for interacting (4,4,0) multiplets. A new N=4 extension of d=1 Calogero-Moser multiparticle system is obtained by gauging the U(n) isometry of matrix SU(2|1) harmonic superfield model.
Quasi-Integrable Deformations of the Bullough-Dodd model
Aurichio, Vinicius H
2015-01-01
It has been shown recently that deformations of some integrable field theories in (1+1)-dimensions possess an infinite number of charges that are asymptotically conserved in the scattering of soliton like solutions. Such charges are not conserved in time and they do vary considerably during the scattering process, however they all return in the remote future (after the scattering) to the values they had in the remote past (before the scattering). Such non-linear phenomenon was named quasi-integrability, and it seems to be related to special properties of the solutions under a space-time parity transformation. In this paper we investigate, analytically and numerically, such phenomenon in the context of deformations of the integrable Bullough-Dodd model. We find that a special class of two-soliton like solutions of such deformed theories do present an infinite number of asymptotically conserved charges.
Videogrammetric Model Deformation Measurement Technique for Wind Tunnel Applications
Barrows, Danny A.
2006-01-01
Videogrammetric measurement technique developments at NASA Langley were driven largely by the need to quantify model deformation at the National Transonic Facility (NTF). This paper summarizes recent wind tunnel applications and issues at the NTF and other NASA Langley facilities including the Transonic Dynamics Tunnel, 31-Inch Mach 10 Tunnel, 8-Ft high Temperature Tunnel, and the 20-Ft Vertical Spin Tunnel. In addition, several adaptations of wind tunnel techniques to non-wind tunnel applications are summarized. These applications include wing deformation measurements on vehicles in flight, determining aerodynamic loads based on optical elastic deformation measurements, measurements on ultra-lightweight and inflatable space structures, and the use of an object-to-image plane scaling technique to support NASA s Space Exploration program.
Raziperchikolaee, S.; Alvarado, V.; Yin, S.
2014-09-01
Studying rock joint deformation including both slippage and opening mechanisms provides an opportunity to investigate the connection between the permeability and seismic source mechanisms. A microscale fluid flow-geomechanics-seismicity model was built to evaluate the transport response and failure mechanism of microcracks developed along a joint in Berea sandstone samples during deformation. The modeling method considers comprehensive grain-cement interactions. Fluid flow behavior is obtained through a realistic network model of the pore space in the compacted assembly. The geometric description of the complex pore structure is characterized to predict permeability of the rock sample as a function of rock deformation by using a dynamic pore network model. As a result of microcracks development, forces and displacements in grains involved in bond breakage are measured to determine seismic moment tensor. Shear and nonshear displacements are applied to the joint samples to investigate their effects on permeability evolution and failure mechanism of microcracks during joint deformation. In addition, the effect of joint roughness is analyzed by performing numerical compression tests. We also investigate how confining pressure affects volumetric deformation leading to opening or closure of developed microcracks and permeability changes of samples with joints.
Viscoelastic models with consistent hypoelasticity for fluids undergoing finite deformations
Altmeyer, Guillaume; Rouhaud, Emmanuelle; Panicaud, Benoit; Roos, Arjen; Kerner, Richard; Wang, Mingchuan
2015-08-01
Constitutive models of viscoelastic fluids are written with rate-form equations when considering finite deformations. Trying to extend the approach used to model these effects from an infinitesimal deformation to a finite transformation framework, one has to ensure that the tensors and their rates are indifferent with respect to the change of observer and to the superposition with rigid body motions. Frame-indifference problems can be solved with the use of an objective stress transport, but the choice of such an operator is not obvious and the use of certain transports usually leads to physically inconsistent formulation of hypoelasticity. The aim of this paper is to present a consistent formulation of hypoelasticity and to combine it with a viscosity model to construct a consistent viscoelastic model. In particular, the hypoelastic model is reversible.
On the Use of Geometric Modeling to Predict Aortic Aneurysm Rupture.
Muluk, Sruthi L; Muluk, Pallavi D; Shum, Judy; Finol, Ender A
2017-05-22
Currently, the risk of abdominal aortic aneurysm (AAA) rupture is determined using the maximum diameter (Dmax) of the aorta. We sought in this study to identify a set of computed tomography (CT)-based geometric parameters that would better predict the risk of rupture than Dmax. We obtained CT scans from 180 patients (90 ruptured AAA and 90 elective AAA repair) and then used automated software to calculate 1- , 2- , and 3-dimensional geometric parameters for each AAA. Linear regression was used to identify univariate correlates of membership in the rupture group. We then used stepwise backward elimination to generate a logistic regression model for prediction of rupture. Linear regression identified 40 correlates of rupture. Following stepwise backward elimination, we developed a multivariate logistic regression model containing 15 geometric parameters, including Dmax. This model was compared with a model containing Dmax alone. The multivariate model correctly classified 98% of all cases, whereas the Dmax-only model correctly classified 72% of cases. Receiver operating characteristic analysis showed that the multivariate model had an area under the curve of 0.995, as compared with 0.770 for the Dmax-only model. This difference was highly significant (P geometric factors entirely measurable from CT scanning can be a better predictor of AAA rupture than maximum diameter alone. Copyright © 2017 Elsevier Inc. All rights reserved.
Zeng, Y.; Schaepman, M.E.; Wu, B.; Clevers, J.G.P.W.; Bregt, A.K.
2009-01-01
The physical-based geometric-optical Li-Strahler model can be inverted to retrieve forest canopy structural variables. One of the main input variables of the inverted model is the fractional component of sunlit background (K g). K g is calculated by using pure reflectance spectra (endmembers) of the
The Dixit-Stiglitz-Krugman Trade Model: A Geometric Note
Kikuchi, Toru
2010-01-01
In this note, we briefly review the now standard Dixit-Stiglitz-Krugman trade model of monopolistic competition. Furthermore, we propose a convincing graphical exposition that emphasizes the firms' entry-exit process.
Single High Fidelity Geometric Data Sets for LCM - Model Requirements
2006-11-01
material name (example, an HY80 steel ) plus additional material requirements (heat treatment, etc.) Creation of a more detailed description of the data...57 Figure 2.22. Typical Stress-Strain Curve for Steel (adapted from Ref 59) .............................. 60 Figure...structures are steel , aluminum and composites. The structural components that make up a global FEA model drive the fidelity of the model. For example
Improving Completeness of Geometric Models from Terrestrial Laser Scanning Data
Directory of Open Access Journals (Sweden)
Clemens Nothegger
2011-12-01
Full Text Available The application of terrestrial laser scanning for the documentation of cultural heritage assets is becoming increasingly common. While the point cloud by itself is sufficient for satisfying many documentation needs, it is often desirable to use this data for applications other than documentation. For these purposes a triangulated model is usually required. The generation of topologically correct triangulated models from terrestrial laser scans, however, still requires much interactive editing. This is especially true when reconstructing models from medium range panoramic scanners and many scan positions. Because of residual errors in the instrument calibration and the limited spatial resolution due to the laser footprint, the point clouds from different scan positions never match perfectly. Under these circumstances many of the software packages commonly used for generating triangulated models produce models which have topological errors such as surface intersecting triangles, holes or triangles which violate the manifold property. We present an algorithm which significantly reduces the number of topological errors in the models from such data. The algorithm is a modification of the Poisson surface reconstruction algorithm. Poisson surfaces are resilient to noise in the data and the algorithm always produces a closed manifold surface. Our modified algorithm partitions the data into tiles and can thus be easily parallelized. Furthermore, it avoids introducing topological errors in occluded areas, albeit at the cost of producing models which are no longer guaranteed to be closed. The algorithm is applied to scan data of sculptures of the UNESCO World Heritage Site Schönbrunn Palace and data of a petrified oyster reef in Stetten, Austria. The results of the method’s application are discussed and compared with those of alternative methods.
Sensitivity analysis of geometric errors in additive manufacturing medical models.
Pinto, Jose Miguel; Arrieta, Cristobal; Andia, Marcelo E; Uribe, Sergio; Ramos-Grez, Jorge; Vargas, Alex; Irarrazaval, Pablo; Tejos, Cristian
2015-03-01
Additive manufacturing (AM) models are used in medical applications for surgical planning, prosthesis design and teaching. For these applications, the accuracy of the AM models is essential. Unfortunately, this accuracy is compromised due to errors introduced by each of the building steps: image acquisition, segmentation, triangulation, printing and infiltration. However, the contribution of each step to the final error remains unclear. We performed a sensitivity analysis comparing errors obtained from a reference with those obtained modifying parameters of each building step. Our analysis considered global indexes to evaluate the overall error, and local indexes to show how this error is distributed along the surface of the AM models. Our results show that the standard building process tends to overestimate the AM models, i.e. models are larger than the original structures. They also show that the triangulation resolution and the segmentation threshold are critical factors, and that the errors are concentrated at regions with high curvatures. Errors could be reduced choosing better triangulation and printing resolutions, but there is an important need for modifying some of the standard building processes, particularly the segmentation algorithms. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.
MODELING AND COMPENSATION TECHNIQUE FOR THE GEOMETRIC ERRORS OF FIVE-AXIS CNC MACHINE TOOLS
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
One of the important trends in precision machining is the development of real-time error compensation technique.The error compensation for multi-axis CNC machine tools is very difficult and attractive.The modeling for the geometric error of five-axis CNC machine tools based on multi-body systems is proposed.And the key technique of the compensation-identifying geometric error parameters-is developed.The simulation of cutting workpiece to verify the modeling based on the multi-body systems is also considered.
Requirements for tolerances in a CAM-I generalized, solid geometric modeling system
Energy Technology Data Exchange (ETDEWEB)
Easterday, R.J.
1980-01-01
For a geometric modeling system to support computer-assisted manufacturing, it is necessary that dimensioning and tolerancing information be available in computer-readable form. The requirements of a tolerancing scheme within a geometric modeling system are discussed; they include structure sufficient to characterize the tolerance specifications currently in use by industry, means to associate tolerance structures to the boundary representation, means to create and edit information in the tolerance structures, means to extract information from the data base, and functions to check for completeness and validity of the tolerances. 1 figure, 8 tables. (RWR)
Optimization of absorption placement using geometrical acoustic models and least squares.
Saksela, Kai; Botts, Jonathan; Savioja, Lauri
2015-04-01
Given a geometrical model of a space, the problem of optimally placing absorption in a space to match a desired impulse response is in general nonlinear. This has led some to use costly optimization procedures. This letter reformulates absorption assignment as a constrained linear least-squares problem. Regularized solutions result in direct distribution of absorption in the room and can accommodate multiple frequency bands, multiple sources and receivers, and constraints on geometrical placement of absorption. The method is demonstrated using a beam tracing model, resulting in the optimal absorption placement on the walls and ceiling of a classroom.
Evolution of Geometric Sensitivity Derivatives from Computer Aided Design Models
Jones, William T.; Lazzara, David; Haimes, Robert
2010-01-01
The generation of design parameter sensitivity derivatives is required for gradient-based optimization. Such sensitivity derivatives are elusive at best when working with geometry defined within the solid modeling context of Computer-Aided Design (CAD) systems. Solid modeling CAD systems are often proprietary and always complex, thereby necessitating ad hoc procedures to infer parameter sensitivity. A new perspective is presented that makes direct use of the hierarchical associativity of CAD features to trace their evolution and thereby track design parameter sensitivity. In contrast to ad hoc methods, this method provides a more concise procedure following the model design intent and determining the sensitivity of CAD geometry directly to its respective defining parameters.
Geometric data transfer between CAD systems: solid models
DEFF Research Database (Denmark)
Kroszynski, Uri; Palstroem, Bjarne; Trostmann, Erik
1989-01-01
The first phase of the ESPRIT project CAD*I resulted in a specification for the exchange of solid models as well as in some pilot implementations of processors based on this specification. The authors summarize the CAD*I approach, addressing the structure of neutral files for solids, entities......, and attributes supporting three kinds of representations: facilities for the transfer of parametric designs; referencing library components; and other general mechanisms. They also describe the current state of the specification and processor implementations and include an example of a CAD*I neutral file....... Results from cycle and intersystem solid model transfer tests are presented, showing the practicality of the CAD*I proposal. B-rep model transfer results are discussed in some detail. The relationship of this work to standardization efforts is outlined...
Reappraisal of a model for deformed special relativity
Gubitosi, Giulia
2015-01-01
We revisit one of the earliest proposals for deformed dispersion relations in the light of recent results on dynamical dimensional reduction and production of cosmological fluctuations. Depending on the specification of the measure of integration and addition rule in momentum space the model may be completed so as to merely deform Lorentz invariance, or so as to introduce a preferred frame. Models which violate Lorentz invariance have a negative UV asymptotic dimension and a very red spectrum of quantum vacuum fluctuations. Instead, models which preserve frame independence can exhibit running to a UV dimension of 2, and a scale-invariant spectrum of fluctuations. The bispectrum of the fluctuations is another point of divergence between the two casings proposed here for the original model.
Ukass, J.; Saks, T.; Popovs, K.
2012-04-01
In present study we attempt to verify the 3D geological model, which has been built on a variety of heterogeneous data sources for the Baltic Basin (BB). Data describing the displacement along the faults and associated thickness changes of the syntectonic strata is sparse and reflects only regional relevance (Brangulis & Konsins 2002). Borehole logs provide most reliable and comprehensive data source for reconstructing the structural geology of the Latvia sedimentary cover as sufficient quality seismic data is available only for the local scale structures. Based on the thickness analysis of the boreholes rough resolution 3D geological tectonic block model was developed to deconstruct the geological structure of the Latvia Caledonian sedimentary sequence. MOSYS modeling system was used for the geological structure modeling, developed within the PUMA project (Sennikovs et al, 2011). Algorithmic genetic approach was applied to interpolate data of well logs as strata volume and sequentially to reconstruct the post-deformation situation. This approach allows modifying model construction in any step and all processes are fully documented and are repeatable. Geometrical model consists of 33 tectonic blocks bordered by the faults which were distributed by interpreting displacement amount of the blocks along the faults providing an opportunity to characterize common tectonic evolution. The study results indicate insignificant thickness change of the Ordovician and Silurian strata along the faults suggesting that major slip event along the faults occurred during the late Silurian and early Devonian, and some secondary fault reactivation during the middle Devonian Narva time. Uplift of the territory during this time is confirmed by the presence of the regional unconformity. Constructed rough resolution 3D geometrical model suggests shortening along the horizontal axis approximately 10 - 20% but most of the shortening has occurred in the central-west part of Latvia where it
Rule-based spatial modeling with diffusing, geometrically constrained molecules
Lohel Maiko; Lenser Thorsten; Ibrahim Bashar; Gruenert Gerd; Hinze Thomas; Dittrich Peter
2010-01-01
Abstract Background We suggest a new type of modeling approach for the coarse grained, particle-based spatial simulation of combinatorially complex chemical reaction systems. In our approach molecules possess a location in the reactor as well as an orientation and geometry, while the reactions are carried out according to a list of implicitly specified reaction rules. Because the reaction rules can contain patterns for molecules, a combinatorially complex or even infinitely sized reaction net...
Martínez, Fabio; Romero, Eduardo; Dréan, Gaël; Simon, Antoine; Haigron, Pascal; De Crevoisier, Renaud; Acosta, Oscar
2014-01-01
Accurate segmentation of the prostate and organs at risk in computed tomography (CT) images is a crucial step for radiotherapy (RT) planning. Manual segmentation, as performed nowadays, is a time consuming process and prone to errors due to the a high intra- and inter-expert variability. This paper introduces a new automatic method for prostate, rectum and bladder segmentation in planning CT using a geometrical shape model under a Bayesian framework. A set of prior organ shapes are first built by applying Principal Component Analysis (PCA) to a population of manually delineated CT images. Then, for a given individual, the most similar shape is obtained by mapping a set of multi-scale edge observations to the space of organs with a customized likelihood function. Finally, the selected shape is locally deformed to adjust the edges of each organ. Experiments were performed with real data from a population of 116 patients treated for prostate cancer. The data set was split in training and test groups, with 30 and 86 patients, respectively. Results show that the method produces competitive segmentations w.r.t standard methods (Averaged Dice = 0.91 for prostate, 0.94 for bladder, 0.89 for Rectum) and outperforms the majority-vote multi-atlas approaches (using rigid registration, free-form deformation (FFD) and the demons algorithm) PMID:24594798
FEMSA: A Finite Element Simulation Tool for Quasi-static Seismic Deformation Modeling
Volpe, M.; Melini, D.; Piersanti, A.
2006-12-01
Modeling postseismic deformation is an increasingly valuable tool in earthquake seismology. In particular, the Finite Element (FE) numerical method allows accurate modeling of complex faulting geometry, inhomogeneous materials and realistic viscous flow, appearing an excellent tool to investigate a lot of specific phenomena related with earthquakes. We developed a FE simulation tool, FEMSA (Finite Element Modeling for Seismic Applications), to model quasi-static deformation generated by faulting sources. The approach allows to automatically implement arbitrary faulting sources and calculate displacement and stress fields induced by slip on the fault. The package makes use of the capabilities of CalculiX, a non commercial FE software designed to solve field problems, and is freely distributed. The main advantages of the method are: reliability, wide diffusion and flexibility, allowing geometrical and/or rheological heterogeneities to be included in a mechanical analysis. We carried out an optimization study on boundary conditions as well as a series of benchmark simulations on test cases and we also verified the capability of our approach to face the presence of 3D heterogeneities within the domain. Here, we present our package and show some simple examples of application.
Physical modeling of geometrically confined disordered protein assemblies
Ando, David
2015-08-01
The transport of cargo across the nuclear membrane is highly selective and accomplished by a poorly understood mechanism involving hundreds of nucleoporins lining the inside of the nuclear pore complex (NPC). Currently, there is no clear picture of the overall structure formed by this collection of proteins within the pore, primarily due to their disordered nature and uncertainty regarding the properties of individual nucleoporins. We first study the defining characteristics of the amino acid sequences of nucleoporins through bioinformatics techniques, although bioinformatics of disordered proteins is especially challenging given high mutation rates for homologous proteins and that functionality may not be strongly related to sequence. Here we have performed a novel bioinformatic analysis, based on the spatial clustering of physically relevant features such as binding motifs and charges within disordered proteins, on thousands of FG motif containing nucleoporins (FG nups). The biophysical mechanism by which the critical FG nups regulate nucleocytoplasmic transport has remained elusive, yet our analysis revealed a set of highly conserved spatial features in the sequence structure of individual FG nups, such as the separation, localization, and ordering of FG motifs and charged residues along the protein chain. These sequence features are likely conserved due to a common functionality between species regarding how FG nups functionally regulate traffic, therefore these results constrain current models and eliminate proposed biophysical mechanisms responsible for regulation of nucleocytoplasmic traffic in the NPC which would not result in such a conserved amino acid sequence structure. Additionally, this method allows us to identify potentially functionally analogous disordered proteins across distantly related species. To understand the physical implications of the sequence features on structure and dynamics of the nucleoporins, we performed coarse-grained simulations
Quantum inverse scattering and the lambda deformed principal chiral model
Appadu, Calan; Hollowood, Timothy J.; Price, Dafydd
2017-07-01
The lambda model is a one parameter deformation of the principal chiral model that arises when regularizing the non-compactness of a non-abelian T dual in string theory. It is a current-current deformation of a WZW model that is known to be integrable at the classical and quantum level. The standard techniques of the quantum inverse scattering method cannot be applied because the Poisson bracket is non ultra-local. Inspired by an approach of Faddeev and Reshetikhin, we show that in this class of models, there is a way to deform the symplectic structure of the theory leading to a much simpler theory that is ultra-local and can be quantized on the lattice whilst preserving integrability. This lattice theory takes the form of a generalized spin chain that can be solved by standard algebraic Bethe Ansatz techniques. We then argue that the IR limit of the lattice theory lies in the universality class of the lambda model implying that the spin chain provides a way to apply the quantum inverse scattering method to this non ultra-local theory. This points to a way of applying the same ideas to other lambda models and potentially the string world-sheet theory in the gauge-gravity correspondence.
MODELING INTRAPERSONAL DEFORMATION SUBSPACE USING GMM FOR PALMPRINT IDENTIFICATION
Institute of Scientific and Technical Information of China (English)
Li Qiang; Qiu Zhengding; Sun Dongmei
2006-01-01
In this paper, an efficient model of palmprint identification is presented based on subspace density estimation using Gaussian Mixture Model (GMM). While a few training samples are available for each person,we use intrapersonal palmprint deformations to train the global GMM instead of modeling GMMs for every class. To reduce the dimension of such variations while preserving density function of sample space, Principle Component Analysis (PCA) is used to find the principle differences and form the Intrapersonal Deformation Subspace (IDS). After training GMM using Expectation Maximization (EM) algorithm in IDS, a maximum likelihood strategy is carried out to identify a person. Experimental results demonstrate the advantage of our method compared with traditional PCA method and single Gaussian strategy.
Mathematical calculation model for geometrical parameters of timber mesh design with orthogonal grid
Directory of Open Access Journals (Sweden)
Loktev Dmitriy Aleksandrovich
Full Text Available Mesh cover design, a multi-element design, which ensures the correct geometrical arrangement of the elements, is a very important task. The purpose of the given article is the development of a mathematical model for selecting the geometric parameters of wooden arches with mesh orthogonal grid with different input data. In this article three variants of design were observed. The main differences between them are in the relative position of longitudinal and transverse components. When performing static calculations of such designs in order to achieve their subsequent correct assembly, the following location conditions were observed: all the items must strictly match with each other without a gap and without overlap. However, these conditions must be met for any ratio of height to the arch span, the number of longitudinal members and the thickness of longitudinal members. Inverse problems also take place. In this case, the geometric calculation is not possible to vary the cross-section elements, and the stress-strain state of the cover is provided by varying the pitch of the transverse arches of the elements, on which the geometric calculation has no influence. All this determines the need for universal mathematical models describing any geometrical parameter of the designs needed for their geometrical calculation. The basic approach for the development of such models is the use of the known trigonometric formulas, giving a complete description of the desired geometry of the arch. Finally three transcendental equations were obtained, the solution algorithm of which using Newton’s method is presented in the MathCAD. The complexity of solving such equations using the proposed algorithm in the MathCAD is reduced to a minimum.
Analytic model of deformation of construction interfaces of rolled control concrete dam
Institute of Scientific and Technical Information of China (English)
GU Chong-shi; HUANG Guang-ming; LAI Dao-ping
2007-01-01
The construction interfaces of RCCD have a distinct influence on the deformation of dams. The characters and rules on deformation of construction interfaces are studied. The methods simulating the deformation of the interfaces at different stages are proposed. A thickness analytic model and a no-thickness analytic model of construction interfaces are built. These models can reflect the elastic deformation, the attenuation creep deformation, the irreversible creep deformation and the accelerating creep deformation of interfaces. The example shows that these proposed models can simulate the deformation of the dam structure objectively. Especially, the results of the thickness analytic model which simulates the gradual changing regularities of interfaces can tally with those of monitoring in situ preferably. The methods proposed and the analytic models can be generalized and applied to general concrete dams, especially to the analysis on deformation rules of fault and interlayer in dam base.
Compound dislocation models (CDMs) for volcano deformation analyses
Nikkhoo, Mehdi; Walter, Thomas R.; Lundgren, Paul R.; Prats-Iraola, Pau
2017-02-01
Volcanic crises are often preceded and accompanied by volcano deformation caused by magmatic and hydrothermal processes. Fast and efficient model identification and parameter estimation techniques for various sources of deformation are crucial for process understanding, volcano hazard assessment and early warning purposes. As a simple model that can be a basis for rapid inversion techniques, we present a compound dislocation model (CDM) that is composed of three mutually orthogonal rectangular dislocations (RDs). We present new RD solutions, which are free of artefact singularities and that also possess full rotational degrees of freedom. The CDM can represent both planar intrusions in the near field and volumetric sources of inflation and deflation in the far field. Therefore, this source model can be applied to shallow dikes and sills, as well as to deep planar and equidimensional sources of any geometry, including oblate, prolate and other triaxial ellipsoidal shapes. In either case the sources may possess any arbitrary orientation in space. After systematically evaluating the CDM, we apply it to the co-eruptive displacements of the 2015 Calbuco eruption observed by the Sentinel-1A satellite in both ascending and descending orbits. The results show that the deformation source is a deflating vertical lens-shaped source at an approximate depth of 8 km centred beneath Calbuco volcano. The parameters of the optimal source model clearly show that it is significantly different from an isotropic point source or a single dislocation model. The Calbuco example reflects the convenience of using the CDM for a rapid interpretation of deformation data.
Geometrical and computer modeling of mechanical engineering surfaces products intersection line
Panchuk, K. L.; Kaygorodtseva, N. V.; Kaygorodtseva, T. N.; Yurkov, V. Yu
2017-06-01
In the design and manufacture of engineering products geometrical problem is known by shaping the surface of the product. An important element of general solution of this problem is to define the lines of surfaces intersection, forming the shape of designed product. Existing possibilities of modern CAD systems do not allow achieving fullness of the result in this direction. For example, control points and change point of visibility is difficult to identify in the product drawings. In addition, there are no possibilities of detecting imaginary points which are necessary for a complete analysis of intersection surfaces, and mapping these points in the drawing. The aim of the study is to develop a geometric algorithm of constructive determining the intersection line and is devoid of these shortcomings. The objectives of the study are testing the obtained algorithm by experimental verification with geometric modeling solutions to specific problems by tools CAD. This study adopted the method, which is based on quotient of geometric sets, which are regarded as intersecting surfaces in space E3 . One area of practical use of surface engineering products geometric algorithm - shaping is based on their intersection line.
Multi-Modality Vertebra Recognition in Arbitrary Views Using 3D Deformable Hierarchical Model.
Cai, Yunliang; Osman, Said; Sharma, Manas; Landis, Mark; Li, Shuo
2015-08-01
Computer-aided diagnosis of spine problems relies on the automatic identification of spine structures in images. The task of automatic vertebra recognition is to identify the global spine and local vertebra structural information such as spine shape, vertebra location and pose. Vertebra recognition is challenging due to the large appearance variations in different image modalities/views and the high geometric distortions in spine shape. Existing vertebra recognitions are usually simplified as vertebrae detections, which mainly focuses on the identification of vertebra locations and labels but cannot support further spine quantitative assessment. In this paper, we propose a vertebra recognition method using 3D deformable hierarchical model (DHM) to achieve cross-modality local vertebra location+pose identification with accurate vertebra labeling, and global 3D spine shape recovery. We recast vertebra recognition as deformable model matching, fitting the input spine images with the 3D DHM via deformations. The 3D model-matching mechanism provides a more comprehensive vertebra location+pose+label simultaneous identification than traditional vertebra location+label detection, and also provides an articulated 3D mesh model for the input spine section. Moreover, DHM can conduct versatile recognition on volume and multi-slice data, even on single slice. Experiments show our method can successfully extract vertebra locations, labels, and poses from multi-slice T1/T2 MR and volume CT, and can reconstruct 3D spine model on different image views such as lumbar, cervical, even whole spine. The resulting vertebra information and the recovered shape can be used for quantitative diagnosis of spine problems and can be easily digitalized and integrated in modern medical PACS systems.
Simulation of mechanisms modeled by geometrically-exact beams using Rodrigues rotation parameters
Gay Neto, Alfredo
2017-03-01
We present mathematical models for joints, springs, dashpots and follower loads, to be used together with geometrically-exact beam finite elements to simulate mechanisms. The rotations are described using Rodrigues parameters. An updated-Lagrangian approach is employed, leading to the possibility of finite rotations involving many turns, overcoming possible singularities in the rotation tensor. We present formulations for spherical, hinge and universal (Cardan) joints, which are enforced by Lagrange multipliers. For the hinge joint, a torsional spring with a nonlinear damper model is presented. A geometric-nonlinear translational spring/dashpot model is proposed, such as follower loads. All formulations are presented detailing their contribution to the model weak form and tangent operator. These are employed together with implicit time-integration schemes. Numerical examples are performed, showing that the proposed formulations are able to model complex spatial mechanisms. Usage of the models together with contact interaction between beams is explored by a cam/follower mechanism example.
Modeling cotton (Gossypium spp) leaves and canopy using computer aided geometric design (CAGD)
The goal of this research is to develop a geometrically accurate model of cotton crop canopies for exploring changes in canopy microenvironment and physiological function with leaf structure. We develop an accurate representation of the leaves, including changes in three-dimensional folding and orie...
Model Study of Wave Overtopping of Marine Structure for a Wide Range of Geometric Parameters
DEFF Research Database (Denmark)
Kofoed, Jens Peter
2000-01-01
The objective of the study described in this paper is to enable estimation of wave overtopping rates for slopes/ramps given by a wide range of geometric parameters when subjected to varying wave conditions. To achieve this a great number of model tests are carried out in a wave tank using irregular...
Optimal control for mathematical models of cancer therapies an application of geometric methods
Schättler, Heinz
2015-01-01
This book presents applications of geometric optimal control to real life biomedical problems with an emphasis on cancer treatments. A number of mathematical models for both classical and novel cancer treatments are presented as optimal control problems with the goal of constructing optimal protocols. The power of geometric methods is illustrated with fully worked out complete global solutions to these mathematically challenging problems. Elaborate constructions of optimal controls and corresponding system responses provide great examples of applications of the tools of geometric optimal control and the outcomes aid the design of simpler, practically realizable suboptimal protocols. The book blends mathematical rigor with practically important topics in an easily readable tutorial style. Graduate students and researchers in science and engineering, particularly biomathematics and more mathematical aspects of biomedical engineering, would find this book particularly useful.
Modeling of friction-induced deformation and microstructures.
Energy Technology Data Exchange (ETDEWEB)
Michael, Joseph Richard; Prasad, Somuri V.; Jungk, John Michael; Cordill, Megan J. (University of Minnesota); Bammann, Douglas J.; Battaile, Corbett Chandler; Moody, Neville Reid; Majumdar, Bhaskar Sinha (New Mexico Institure of Mining and Technology)
2006-12-01
Frictional contact results in surface and subsurface damage that could influence the performance, aging, and reliability of moving mechanical assemblies. Changes in surface roughness, hardness, grain size and texture often occur during the initial run-in period, resulting in the evolution of subsurface layers with characteristic microstructural features that are different from those of the bulk. The objective of this LDRD funded research was to model friction-induced microstructures. In order to accomplish this objective, novel experimental techniques were developed to make friction measurements on single crystal surfaces along specific crystallographic surfaces. Focused ion beam techniques were used to prepare cross-sections of wear scars, and electron backscattered diffraction (EBSD) and TEM to understand the deformation, orientation changes, and recrystallization that are associated with sliding wear. The extent of subsurface deformation and the coefficient of friction were strongly dependent on the crystal orientation. These experimental observations and insights were used to develop and validate phenomenological models. A phenomenological model was developed to elucidate the relationships between deformation, microstructure formation, and friction during wear. The contact mechanics problem was described by well-known mathematical solutions for the stresses during sliding friction. Crystal plasticity theory was used to describe the evolution of dislocation content in the worn material, which in turn provided an estimate of the characteristic microstructural feature size as a function of the imposed strain. An analysis of grain boundary sliding in ultra-fine-grained material provided a mechanism for lubrication, and model predictions of the contribution of grain boundary sliding (relative to plastic deformation) to lubrication were in good qualitative agreement with experimental evidence. A nanomechanics-based approach has been developed for characterizing the
Vile, Douglas J.
In radiation therapy, interfraction organ motion introduces a level of geometric uncertainty into the planning process. Plans, which are typically based upon a single instance of anatomy, must be robust against daily anatomical variations. For this problem, a model of the magnitude, direction, and likelihood of deformation is useful. In this thesis, principal component analysis (PCA) is used to statistically model the 3D organ motion for 19 prostate cancer patients, each with 8-13 fractional computed tomography (CT) images. Deformable image registration and the resultant displacement vector fields (DVFs) are used to quantify the interfraction systematic and random motion. By applying the PCA technique to the random DVFs, principal modes of random tissue deformation were determined for each patient, and a method for sampling synthetic random DVFs was developed. The PCA model was then extended to describe the principal modes of systematic and random organ motion for the population of patients. A leave-one-out study tested both the systematic and random motion model's ability to represent PCA training set DVFs. The random and systematic DVF PCA models allowed the reconstruction of these data with absolute mean errors between 0.5-0.9 mm and 1-2 mm, respectively. To the best of the author's knowledge, this study is the first successful effort to build a fully 3D statistical PCA model of systematic tissue deformation in a population of patients. By sampling synthetic systematic and random errors, organ occupancy maps were created for bony and prostate-centroid patient setup processes. By thresholding these maps, PCA-based planning target volume (PTV) was created and tested against conventional margin recipes (van Herk for bony alignment and 5 mm fixed [3 mm posterior] margin for centroid alignment) in a virtual clinical trial for low-risk prostate cancer. Deformably accumulated delivered dose served as a surrogate for clinical outcome. For the bony landmark setup
Resurgence in η-deformed Principal Chiral Models
Energy Technology Data Exchange (ETDEWEB)
Demulder, Saskia [Theoretische Natuurkunde, Vrije Universiteit Brussel and The International Solvay Institutes,Pleinlaan 2, 1050, Brussels (Belgium); Dorigoni, Daniele [Centre for Particle Theory & Department of Mathematical Sciences, Durham University,Durham DH1 3LE (United Kingdom); Thompson, Daniel C. [Theoretische Natuurkunde, Vrije Universiteit Brussel and The International Solvay Institutes,Pleinlaan 2, 1050, Brussels (Belgium)
2016-07-18
We study the SU(2) Principal Chiral Model (PCM) in the presence of an integrable η-deformation. We put the theory on ℝ×S{sup 1} with twisted boundary conditions and then reduce the circle to obtain an effective quantum mechanics associated with the Whittaker-Hill equation. Using resurgent analysis we study the large order behaviour of perturbation theory and recover the fracton events responsible for IR renormalons. The fractons are modified from the standard PCM due to the presence of this η-deformation but they are still the constituents of uniton-like solutions in the deformed quantum field theory. We also find novel SL(2,ℂ) saddles, thus strengthening the conjecture that the semi-classical expansion of the path integral gives rise to a resurgent transseries once written as a sum over Lefschetz thimbles living in a complexification of the field space. We conclude by connecting our quantum mechanics to a massive deformation of the N=2 4-d gauge theory with gauge group SU(2) and N{sub f}=2.
Resurgence in $\\eta$-deformed Principal Chiral Models
Demulder, Saskia; Thompson, Daniel C
2016-01-01
We study the $SU(2)$ Principal Chiral Model (PCM) in the presence of an integrable $\\eta$-deformation. We put the theory on $\\mathbb{R}\\times S^1$ with twisted boundary conditions and then reduce the circle to obtain an effective quantum mechanics associated with the Whittaker-Hill equation. Using resurgent analysis we study the large order behaviour of perturbation theory and recover the fracton events responsible for IR renormalons. The fractons are modified from the standard PCM due to the presence of this $\\eta$-deformation but they are still the constituents of uniton-like solutions in the deformed quantum field theory. We also find novel $SL(2,\\mathbb{C})$ saddles, thus strengthening the conjecture that the semi-classical expansion of the path integral gives rise to a resurgent transseries once written as a sum over Lefschetz thimbles living in a complexification of the field space. We conclude by connecting our quantum mechanics to a massive deformation of the $\\mathcal{N}=2~$ $4$-d gauge theory with g...
Resurgence in η-deformed Principal Chiral Models
Demulder, Saskia; Dorigoni, Daniele; Thompson, Daniel C.
2016-07-01
We study the SU(2) Principal Chiral Model (PCM) in the presence of an integrable η-deformation. We put the theory on {R}× {S}^1 with twisted boundary conditions and then reduce the circle to obtain an effective quantum mechanics associated with the Whittaker-Hill equation. Using resurgent analysis we study the large order behaviour of perturbation theory and recover the fracton events responsible for IR renormalons. The fractons are modified from the standard PCM due to the presence of this η-deformation but they are still the constituents of uniton-like solutions in the deformed quantum field theory. We also find novel SL(2,{C}) saddles, thus strengthening the conjecture that the semi-classical expansion of the path integral gives rise to a resurgent transseries once written as a sum over Lefschetz thimbles living in a complexification of the field space. We conclude by connecting our quantum mechanics to a massive deformation of the {N} = 2 4-d gauge theory with gauge group SU(2) and N f = 2.
Directory of Open Access Journals (Sweden)
Tim Odenthal
Full Text Available Adhesion governs to a large extent the mechanical interaction between a cell and its microenvironment. As initial cell spreading is purely adhesion driven, understanding this phenomenon leads to profound insight in both cell adhesion and cell-substrate interaction. It has been found that across a wide variety of cell types, initial spreading behavior universally follows the same power laws. The simplest cell type providing this scaling of the radius of the spreading area with time are modified red blood cells (RBCs, whose elastic responses are well characterized. Using a mechanistic description of the contact interaction between a cell and its substrate in combination with a deformable RBC model, we are now able to investigate in detail the mechanisms behind this universal power law. The presented model suggests that the initial slope of the spreading curve with time results from a purely geometrical effect facilitated mainly by dissipation upon contact. Later on, the spreading rate decreases due to increasing tension and dissipation in the cell's cortex as the cell spreads more and more. To reproduce this observed initial spreading, no irreversible deformations are required. Since the model created in this effort is extensible to more complex cell types and can cope with arbitrarily shaped, smooth mechanical microenvironments of the cells, it can be useful for a wide range of investigations where forces at the cell boundary play a decisive role.
Reduction by Lie Group Symmetries in Diffeomorphic Image Registration and Deformation Modelling
Directory of Open Access Journals (Sweden)
Stefan Sommer
2015-05-01
Full Text Available We survey the role of reduction by symmetry in the large deformation diffeomorphic metric mapping framework for registration of a variety of data types (landmarks, curves, surfaces, images and higher-order derivative data. Particle relabelling symmetry allows the equations of motion to be reduced to the Lie algebra allowing the equations to be written purely in terms of the Eulerian velocity field. As a second use of symmetry, the infinite dimensional problem of finding correspondences between objects can be reduced for a range of concrete data types, resulting in compact representations of shape and spatial structure. Using reduction by symmetry, we describe these models in a common theoretical framework that draws on links between the registration problem and geometric mechanics. We outline these constructions and further cases where reduction by symmetry promises new approaches to the registration of complex data types.
Extension of non-linear beam models with deformable cross sections
Sokolov, I.; Krylov, S.; Harari, I.
2015-12-01
Geometrically exact beam theory is extended to allow distortion of the cross section. We present an appropriate set of cross-section basis functions and provide physical insight to the cross-sectional distortion from linear elastostatics. The beam formulation in terms of material (back-rotated) beam internal force resultants and work-conjugate kinematic quantities emerges naturally from the material description of virtual work of constrained finite elasticity. The inclusion of cross-sectional deformation allows straightforward application of three-dimensional constitutive laws in the beam formulation. Beam counterparts of applied loads are expressed in terms of the original three-dimensional data. Special attention is paid to the treatment of the applied stress, keeping in mind applications such as hydrogel actuators under environmental stimuli or devices made of electroactive polymers. Numerical comparisons show the ability of the beam model to reproduce finite elasticity results with good efficiency.
DEFF Research Database (Denmark)
Sonne, Mads Rostgaard; Cech, Jiri; Pranov, H.
2016-01-01
In the present work, a manufacturing process for transferring nanostructures from a glass wafer, to a double-curvedinsert for injection moulding is demonstrated. A nanostructure consisting of sinusoidal cross-gratings with a period of 426 nm issuccessfully transferred to hemispheres on an aluminium...... substrate with three different radii; 500 μm, 1000 μm and 2000 μm,respectively. The nanoimprint is performed using a 50 μm thick nickel foil, manufactured using electroforming. During theimprinting process, the nickel foil is stretched due to the curved surface of the aluminium substrate. Experimentally......, it is possibleto address this stretch by counting the periods of the cross-gratings via SEM characterization. A model for the deformation of thenickel foil during nanoimprint is developed, utilizing non-linear material and geometrical behaviour. Good agreement betweenmeasured and numerically calculated stretch...
Experimental modelling of ground deformation associated with shallow magma intrusions
Galland, O.
2012-04-01
Active volcanoes experience ground deformation as a response to the dynamics of underground magmatic systems. The analysis of ground deformation patterns may provide important constraints on the dynamics and shape of the underlying volcanic plumbing systems. Nevertheless, these analyses usually take into account simplistic shapes (sphere, dykes, sills) and the results cannot be verified as the modelled systems are buried. In this contribution, I will present new results from experimental models of magma intrusion, in which both the evolution of ground deformation during intrusion and the shape of the underlying intrusion are monitored in 3D. The models consisted of a molten vegetable oil, simulating low viscosity magma, injected into cohesive fine-grained silica flour, simulating the brittle upper crust; oil injection resulted is sheet intrusions (dykes, sills and cone sheets). The initial topography in the models was flat. While the oil was intruding, the surface of the models slightly lifted up to form a smooth relief, which was mapped through time. After an initial symmetrical development, the uplifted area developed asymmetrically; at the end of the experiments, the oil always erupted at the steepest edge of the uplifted area. After the experiment, the oil solidified, the intrusion was excavated and the shape of its top surface mapped. The comparison between the uplifted zone and the underlying intrusions showed that (1) the complex shapes of the uplifted areas reflected the complex shapes of the underlying intrusions, (2) the time evolution of the uplifted zone was correlated with the evolution of the underlying intrusion, and (3) the early asymmetrical evolution of the uplifted areas can be used to predict the location of the eruption of the oil. The experimental results also suggest that complex intrusion shapes (inclined sheet, cone sheet, complex sill) may have to be considered more systematically in analyses of ground deformation patterns on volcanoes.
A large deformation viscoelastic model for double-network hydrogels
Mao, Yunwei; Lin, Shaoting; Zhao, Xuanhe; Anand, Lallit
2017-03-01
We present a large deformation viscoelasticity model for recently synthesized double network hydrogels which consist of a covalently-crosslinked polyacrylamide network with long chains, and an ionically-crosslinked alginate network with short chains. Such double-network gels are highly stretchable and at the same time tough, because when stretched the crosslinks in the ionically-crosslinked alginate network rupture which results in distributed internal microdamage which dissipates a substantial amount of energy, while the configurational entropy of the covalently-crosslinked polyacrylamide network allows the gel to return to its original configuration after deformation. In addition to the large hysteresis during loading and unloading, these double network hydrogels also exhibit a substantial rate-sensitive response during loading, but exhibit almost no rate-sensitivity during unloading. These features of large hysteresis and asymmetric rate-sensitivity are quite different from the response of conventional hydrogels. We limit our attention to modeling the complex viscoelastic response of such hydrogels under isothermal conditions. Our model is restricted in the sense that we have limited our attention to conditions under which one might neglect any diffusion of the water in the hydrogel - as might occur when the gel has a uniform initial value of the concentration of water, and the mobility of the water molecules in the gel is low relative to the time scale of the mechanical deformation. We also do not attempt to model the final fracture of such double-network hydrogels.
Xin, Q.; Gong, P.; Li, W.
2015-02-01
Modeling vegetation photosynthesis is essential for understanding carbon exchanges between terrestrial ecosystems and the atmosphere. The radiative transfer process within plant canopies is one of the key drivers that regulate canopy photosynthesis. Most vegetation cover consists of discrete plant crowns, of which the physical observation departs from the underlying assumption of a homogenous and uniform medium in classic radiative transfer theory. Here we advance the Geometric Optical Radiative Transfer (GORT) model to simulate photosynthesis activities for discontinuous plant canopies. We separate radiation absorption into two components that are absorbed by sunlit and shaded leaves, and derive analytical solutions by integrating over the canopy layer. To model leaf-level and canopy-level photosynthesis, leaf light absorption is then linked to the biochemical process of gas diffusion through leaf stomata. The canopy gap probability derived from GORT differs from classic radiative transfer theory, especially when the leaf area index is high, due to leaf clumping effects. Tree characteristics such as tree density, crown shape, and canopy length affect leaf clumping and regulate radiation interception. Modeled gross primary production (GPP) for two deciduous forest stands could explain more than 80% of the variance of flux tower measurements at both near hourly and daily time scales. We also demonstrate that the ambient CO2 concentration influences daytime vegetation photosynthesis, which needs to be considered in state-of-the-art biogeochemical models. The proposed model is complementary to classic radiative transfer theory and shows promise in modeling the radiative transfer process and photosynthetic activities over discontinuous forest canopies.
Geometric modeling for citation networks with linearly growing scientific paper increment
Liu, Qi; Dong, Engming; Li, Jianping
2016-01-01
For the case that the numbers of annual published papers in some citation networks grow linearly, a geometric model is proposed to predict some statistical features of those networks, in which the academic influence scopes of papers are denoted through specific geometric areas related to time and space. In the model, nodes (papers) are uniformly and randomly sprinkled onto a cluster of circles of the Minkowski space whose centers are on the time axis. Edges (citations) are linked according to an influence mechanism which indicates an existing paper will be cited by a new paper locating in its influence zone. Considering the citations between papers in different disciplines, an interdisciplinary citation mechanism is added into the model in which some papers chosen with a small probability will cite some existing papers randomly and uniformly. Different from most existing models which only study the scale-free tail of the in-degree distribution, this model characterize the overall in-degree distribution well. ...
Modelling of the Deformation Diffusion Areas on a Para-Aramid Fabric with B-Spline Curves
Directory of Open Access Journals (Sweden)
Hatice Kuşak Samancı
2017-01-01
Full Text Available The geometrical modelling of the planar energy diffusion behaviors of the deformations on a para-aramid fabric has been performed. In the application process of the study, in the experimental period, drop test with bullets of different weights has been applied. The B-spline curve-generating technique has been used in the study. This is an efficient method for geometrical modelling of the deformation diffusion areas formed after the drop test. Proper control points have been chosen to be able to draw the borders of the diffusion areas on the fabric which is deformed, and then the De Casteljau and De Boor algorithms have been used. The Holditch area calculation according to the beams taken at certain fixed lengths has been performed for the B-spline border curve obtained as a closed form. After the calculations, it has been determined that the diffusion area where the bullet with pointed end was dropped on a para-aramid fabric is bigger and the diffusion area where the bullet with rounded end was dropped is smaller when compared with the areas where other bullets with different ends were dropped.
Ishimoto, Yukitaka
2014-01-01
In order to describe two-dimensionally packed cells in epithelial tissues both mathematically and physically, there have been developed several sorts of geometrical models, such as the vertex model, the finite element model, the cell-centered model, the cellular Potts model. So far, in any case, pressures have not neatly been dealt with and curvatures of the cell boundaries have been even omitted through their approximations. We focus on these quantities and formulate them on the vertex model. Thus, a model with the curvatures is constructed and its algorithm is given for simulation. Its possible extensions and applications will also be discussed.
Embankment deformation analyzed by elastoplastic damage model coupling consolidation theory
Institute of Scientific and Technical Information of China (English)
Hong SUN; Xihong ZHAO
2006-01-01
The deformation of embankment has serious influences on neighboring structure and infrastructure. A trial embankment is reanalyzed by elastoplastic damage model coupling Biot's consolidation theory. With the increase in time of loading, the damage accumulation becomes larger. Under the centre and toe of embankment, damage becomes serious. Under the centre of embankment, vertical damage values are bigger than horizontal ones. Under the toe of embankment, horizontal damage values are bigger than vertical ones.
Description of deformed nuclei in the sdg boson model
Li, S C
1996-01-01
We present a study of deformed nuclei in the framework of the sdg interacting boson model utilizing both numerical diagonalization and analytical 1/N expansion techniques. The focus is on description of high-spin states which have recently become computationally accessible through the use of computer algebra in the 1/N expansion formalism. A systematic study is made of high-spin states in rare-earth and actinide nuclei.
Modified Sachs's Model of Deformation of Polycrystalline Magnesium
Kesarev, A. G.; Vlasova, A. M.
2017-09-01
There are a large number of approaches to a description of work hardening of metal polycrystals with various crystal lattices. In the present work, Sachs's model is generalized to uniaxial tension/compression of polycrystalline magnesium with hexagonal densely packed crystal lattice. The tensile yield stress is estimated taking into account two deformation modes: (0001) easy basal slip and (10\\overline{1}2) twinning.
A geometric graph model for citation networks of exponentially growing scientific papers
Xie, Zheng; Ouyang, Zhenzheng; Liu, Qi; Li, Jianping
2016-08-01
In citation networks, the content relativity of papers is a precondition of engendering citations, which is hard to model by a topological graph. A geometric graph is proposed to predict some features of the citation networks with exponentially growing papers, which addresses the precondition by using coordinates of nodes to model the research contents of papers, and geometric distances between nodes to diversities of research contents between papers. Citations between modeled papers are drawn according to a geometric rule, which addresses the precondition as well as some other factors engendering citations, namely academic influences of papers, aging of those influences, and incomplete copying of references. Instead of cumulative advantage of degree, the model illustrates that the scale-free property of modeled networks arises from the inhomogeneous academic influences of modeled papers. The model can also reproduce some other statistical features of citation networks, e.g. in- and out-assortativities, which show the model provides a suitable tool to understand some aspects of citation networks by geometry.
Modeling Permanent Deformations of Superelastic and Shape Memory Materials.
Urbano, Marco Fabrizio; Auricchio, Ferdinando
2015-06-11
In this paper we propose a modification of the polycrystalline shape memory alloy constitutive model originally proposed by Souza. By introducing a transformation strain energy with two different hardening coefficients, we are able to take into account the effect of the martensitic transformation of unfavorably oriented grains occurring after the main plateau. By choosing a proper second hardening coefficient, it is possible to reproduce the correct stress strain behavior of the material after the plateau without the need of introducing a much smaller Young modulus for martensite. The proposed modification is introduced in the model comprising permanent deformation effects. Model results for uniaxial stress tests are compared to experimental results showing good agreement.
Heavy quark potential from deformed AdS5 models
Zhang, Zi-qiang; Hou, De-fu; Chen, Gang
2017-04-01
In this paper, we investigate the heavy quark potential in some holographic QCD models. The calculation relies on a modified renormalization scheme mentioned in a previous work of Albacete et al. After studying the heavy quark potential in Pirner-Galow model and Andreev-Zakharov model, we extend the discussion to a general deformed AdS5 case. It is shown that the obtained potential is negative definite for all quark-antiquark separations, differs from that using the usual renormalization scheme.
Muniz Oliva, Waldyr
2002-01-01
Geometric Mechanics here means mechanics on a pseudo-riemannian manifold and the main goal is the study of some mechanical models and concepts, with emphasis on the intrinsic and geometric aspects arising in classical problems. The first seven chapters are written in the spirit of Newtonian Mechanics while the last two ones as well as two of the four appendices describe the foundations and some aspects of Special and General Relativity. All the material has a coordinate free presentation but, for the sake of motivation, many examples and exercises are included in order to exhibit the desirable flavor of physical applications.
Analysis of Data from a Series of Events by a Geometric Process Model
Institute of Scientific and Technical Information of China (English)
Yeh Lam; Li-xing Zhu; Jennifer S. K. Chan; Qun Liu
2004-01-01
Geometric process was first introduced by Lam[10,11]. A stochastic process {Xi, i = 1, 2,…} is called a geometric process (GP) if, for some a > 0, {ai-1Xi, i = 1, 2,…} forms a renewal process. In thispaper, the GP is used to analyze the data from a series of events. A nonparametric method is introduced forthe estimation of the three parameters in the GP. The limiting distributions of the three estimators are studied.Through the analysis of some real data sets, the GP model is compared with other three homogeneous andnonhomogeneous Poisson models. It seems that on average the GP model is the best model among these fourmodels in analyzing the data from a series of events.
Radmap: ''as-built'' cad models incorporating geometrical, radiological and material information
Energy Technology Data Exchange (ETDEWEB)
Piotrowski, L. [Electricite de France (EDF/DRD), 78 - Chatou (France); Lubawy, J.L. [Electricite de France (EDF/CNEPE), 37 - Tours (France)
2001-07-01
EDF intends to achieve successful and cost-effective dismantling of its obsolete nuclear plants. To reach this goal, EDF is currently extending its ''as-built'' 3-D modelling system to also include the location and characteristics of gamma sources in the geometrical models of its nuclear installations. The resulting system (called RADMAP) is a complete CAD chain covering 3-D and gamma data acquisitions, CAD modelling and exploitation of the final model. Its aim is to describe completely the geometrical and radiological state of a particular nuclear environment. This paper presents an overall view of RADMAP. The technical and functional characteristics of each element of the chain are indicated and illustrated using real (EDF) environments/applications. (author)
A geometrical construction of rational boundary states in linear sigma models
Energy Technology Data Exchange (ETDEWEB)
Kennaway, Kristian D. E-mail: kennaway@usc.edu
2002-12-30
Starting from the geometrical construction of special Lagrangian submanifolds of a toric variety, we identify a certain subclass of A-type D-branes in the linear sigma model for a Calabi-Yau manifold and its mirror with the A- and B-type Recknagel-Schomerus boundary states of the Gepner model, by reproducing topological properties such as their labeling, intersection, and the relationships that exist in the homology lattice of the D-branes. In the non-linear sigma model phase these special Lagrangians reproduce an old construction of 3-cycles relevant for computing periods of the Calabi-Yau, and provide insight into other results in the literature on special Lagrangian submanifolds on compact Calabi-Yau manifolds. The geometrical construction of rational boundary states suggests several ways in which new Gepner model boundary states may be constructed.
A geometric graph model of the coevolution between citations and coauthorships in scientific papers
Xie, Zheng; Li, Jianping; Li, Miao; Yi, Dongyun
2016-01-01
Collaborations and citations within scientific research grow simultaneously and interact dynamically. Modelling the coevolution between them helps to study many phenomena that can be approached only through combining citation and coauthorship data. A geometric graph for the coevolution is proposed, the mechanism of which synthetically expresses the interactive impacts of authors and papers in a geometrical way. The model is validated against a data set of papers published in PNAS during 2000-2015. The validation shows the ability to reproduce a range of features observed with citation and coauthorship data combined and separately. Particulary, in the empirical distribution of citations per author there exist two limits, in which the distribution appears as a generalized Poisson and a power-law respectively. Our model successfully reproduces the shape of the distribution, and provides an explanation for how the shape emerges. The model also captures the empirically positive correlations between the numbers of ...
Numerical modelling of stresses and deformations in casting processes
DEFF Research Database (Denmark)
Hattel, Jesper Henri
1997-01-01
Keywords: Stresses and deformations, casting, governing equations, thermal strain, control volume method......Keywords: Stresses and deformations, casting, governing equations, thermal strain, control volume method...
Numerical modelling of stresses and deformations in casting processes
DEFF Research Database (Denmark)
Hattel, Jesper Henri
1997-01-01
Keywords: Stresses and deformations, casting, governing equations, thermal strain, control volume method......Keywords: Stresses and deformations, casting, governing equations, thermal strain, control volume method...
Surrogate Modeling of Deformable Joint Contact using Artificial Neural Networks
Eskinazi, Ilan; Fregly, Benjamin J.
2016-01-01
Deformable joint contact models can be used to estimate loading conditions for cartilage-cartilage, implant-implant, human-orthotic, and foot-ground interactions. However, contact evaluations are often so expensive computationally that they can be prohibitive for simulations or optimizations requiring thousands or even millions of contact evaluations. To overcome this limitation, we developed a novel surrogate contact modeling method based on artificial neural networks (ANNs). The method uses special sampling techniques to gather input-output data points from an original (slow) contact model in multiple domains of input space, where each domain represents a different physical situation likely to be encountered. For each contact force and torque output by the original contact model, a multi-layer feed-forward ANN is defined, trained, and incorporated into a surrogate contact model. As an evaluation problem, we created an ANN-based surrogate contact model of an artificial tibiofemoral joint using over 75,000 evaluations of a fine-grid elastic foundation (EF) contact model. The surrogate contact model computed contact forces and torques about 1000 times faster than a less accurate coarse grid EF contact model. Furthermore, the surrogate contact model was seven times more accurate than the coarse grid EF contact model within the input domain of a walking motion. For larger input domains, the surrogate contact model showed the expected trend of increasing error with increasing domain size. In addition, the surrogate contact model was able to identify out-of-contact situations with high accuracy. Computational contact models created using our proposed ANN approach may remove an important computational bottleneck from musculoskeletal simulations or optimizations incorporating deformable joint contact models. PMID:26220591
Frame junction vibration transmission with a modified frame deformation model.
Moore, J A
1990-12-01
A previous paper dealt with vibration transmission through junctions of connected frame members where the allowed frame deformations included bending, torsion, and longitudinal motions [J.A. Moore, J. Acoust. Soc. Am. 88, 2766-2776 (1990)]. In helicopter and aircraft structures the skin panels can constitute a high impedance connection along the length of the frames that effectively prohibits in-plane motion at the elevation of the skin panels. This has the effect of coupling in-plane bending and torsional motions within the frame. This paper discusses the transmission behavior through frame junctions that accounts for the in-plane constraint in idealized form by assuming that the attached skin panels completely prohibit inplane motion in the frames. Also, transverse shear deformation is accounted for in describing the relatively deep web frame constructions common in aircraft structures. Longitudinal motion in the frames is not included in the model. Transmission coefficient predictions again show the importance of out-of-plane bending deformation to the transmission of vibratory energy in an aircraft structure. Comparisons are shown with measured vibration transmission data along the framing in the overhead of a helicopter airframe, with good agreement. The frame junction description has been implemented within a general purpose statistical energy analysis (SEA) computer code in modeling the entire airframe structure including skin panels.
An Elliptical Model for Deformation Due to Groundwater Fluctuations
Tiampo, Kristy F.; Ouegnin, Francois-Alexis; Valluri, Sreeram; Samsonov, Sergey; Fernández, José; Kapp, Garrett
2012-08-01
Historically, surface subsidence as a result of subsurface groundwater fluctuations have produced important and, at times, catastrophic effects, whether natural or anthropogenic. Over the past 30 years, numerical and analytical techniques for the modeling of this surface deformation, based upon elastic and poroelastic theory, have been remarkably successful in predicting the magnitude of that deformation (L e M ouélic and A dragna in Geophys Res Lett 29:1853, 2002). In this work we have extended the formula for a circular-shaped aquifer (Geertsma in J Petroleum Tech 25:734-744, 1973) to a more realistic elliptical shape. We have improved the accuracy of the approximation by making use of the cross terms of the expansion for the elliptic coordinates in terms of the eccentricity, e, and the mean anomaly angle, M, widely used in astronomy. Results of a number of simulations, in terms of e and M developed from the transcendental Kepler equation, are encouraging, giving realistic values for the elliptical approximation of the vertical deformation due to groundwater change. Finally, we have applied the algorithm to modeling of groundwater in southern California.
Oscillatory athermal quasistatic deformation of a model glass
Fiocco, Davide; Foffi, Giuseppe; Sastry, Srikanth
2013-08-01
We report computer simulations of oscillatory athermal quasistatic shear deformation of dense amorphous samples of a three-dimensional model glass former. A dynamical transition is observed as the amplitude of the deformation is varied: For large values of the amplitude the system exhibits diffusive behavior and loss of memory of the initial conditions, whereas localization is observed for small amplitudes. Our results suggest that the same kind of transition found in driven colloidal systems is present in the case of amorphous solids (e.g., metallic glasses). The onset of the transition is shown to be related to the onset of energy dissipation. Shear banding is observed for large system sizes, without, however, affecting qualitative aspects of the transition.
Geometric and material modeling environment for the finite-difference time-domain method
Lee, Yong-Gu; Muhammad, Waleed
2012-02-01
The simulation of electromagnetic problems using the Finite-Difference Time-Domain method starts with the geometric design of the devices and their surroundings with appropriate materials and boundary conditions. This design stage is one of the most time consuming part in the Finite-Difference Time-Domain (FDTD) simulation of photonics devices. Many FDTD solvers have their own way of providing the design environment which can be burdensome for a new user to learn. In this work, geometric and material modeling features are developed on the freely available Google SketchUp, allowing users who are fond of its environment to easily model photonics simulations. The design and implementation of the modeling environment are discussed.
Directory of Open Access Journals (Sweden)
Bum-Joo Lee
2013-02-01
Full Text Available In this paper differential kinematics was geometrically derived to be utilized in a calibration algorithm that improves the accuracy of the manipulation of a robot. Even though the mechanical components are manufactured and assembled precisely, small differences between the designed and the actual system always exist, due to both geometric and unmodelled errors. In order to resolve these problems, differential relationships between the model parameters and the end‐effectorʹs posture were formulated. Subsequently, a derivative based estimation algorithm, such as an EKF (Extended Kalman Filter manner, could be adopted to update the model parameters. The proposed algorithm includes joint flexibility, so is an advanced version of previous work, where a rigid joint model was adopted [1]. The effectiveness of the proposed algorithm was verified by a computer simulation with a 6 DOF manipulator robot.
Geant4.10 simulation of geometric model for metaphase chromosome
Energy Technology Data Exchange (ETDEWEB)
Rafat-Motavalli, L., E-mail: rafat@um.ac.ir; Miri-Hakimabad, H.; Bakhtiyari, E.
2016-04-01
In this paper, a geometric model of metaphase chromosome is explained. The model is constructed according to the packing ratio and dimension of the structure from nucleosome up to chromosome. A B-DNA base pair is used to construct 200 base pairs of nucleosomes. Each chromatin fiber loop, which is the unit of repeat, has 49,200 bp. This geometry is entered in Geant4.10 Monte Carlo simulation toolkit and can be extended to the whole metaphase chromosomes and any application in which a DNA geometrical model is needed. The chromosome base pairs, chromosome length, and relative length of chromosomes are calculated. The calculated relative length is compared to the relative length of human chromosomes.
Region-based geometric modelling of human airways and arterial vessels.
Ding, Songlin; Ye, Yong; Tu, Jiyuan; Subic, Aleksandar
2010-03-01
Anatomically precise geometric models of human airways and arterial vessels play a critical role in the analysis of air and blood flows in human bodies. The established geometric modelling methods become invalid when the model consists of bronchioles or small vessels. This paper presents a new method for reconstructing the entire airway tree and carotid vessels from point clouds obtained from CT or MR images. A novel layer-by-layer searching algorithm has been developed to recognize branches of the airway tree and arterial vessels from the point clouds. Instead of applying uniform accuracy to all branches regardless of the number of available points, the surface patches on each branch are constructed adaptively based on the number of available elemental points, which leads to the elimination of distortions occurring at small bronchi and vessels.
Geometrical origin of tricritical points of various U(1) lattice models
Janke, W; Janke, W; Kleinert, H
1995-01-01
We review the dual relationship between various compact U(1) lattice models and Abelian Higgs models, the latter being the disorder field theories of line-like topological excitations in the systems. We point out that the predicted first-order transitions in the Abelian Higgs models (Coleman-Weinberg mechanism) are, in three dimensions, in contradiction with direct numerical investigations in the compact U(1) formulation since these yield continuous transitions in the major part of the phase diagram. In four dimensions, there are indications from Monte Carlo data for a similar situation. Concentrating on the strong-coupling expansion in terms of geometrical objects, surfaces or lines, with certain statistical weights, we present semi-quantitative arguments explaining the observed cross-over from first-order to continuous transitions by the balance between the lowest two weights (``2:1 ratio'') of these geometrical objects.
Directory of Open Access Journals (Sweden)
Bum-Joo Lee
2013-02-01
Full Text Available In this paper differential kinematics was geometrically derived to be utilized in a calibration algorithm that improves the accuracy of the manipulation of a robot. Even though the mechanical components are manufactured and assembled precisely, small differences between the designed and the actual system always exist, due to both geometric and unmodelled errors. In order to resolve these problems, differential relationships between the model parameters and the end-effector's posture were formulated. Subsequently, a derivative based estimation algorithm, such as an EKF (Extended Kalman Filter manner, could be adopted to update the model parameters. The proposed algorithm includes joint flexibility, so is an advanced version of previous work, where a rigid joint model was adopted [1]. The effectiveness of the proposed algorithm was verified by a computer simulation with a 6 DOF manipulator robot.
Deformed Gaussian Orthogonal Ensemble Analysis of the Interacting Boson Model
Pato, M P; Lima, C L; Hussein, M S; Alhassid, Y
1994-01-01
A Deformed Gaussian Orthogonal Ensemble (DGOE) which interpolates between the Gaussian Orthogonal Ensemble and a Poissonian Ensemble is constructed. This new ensemble is then applied to the analysis of the chaotic properties of the low lying collective states of nuclei described by the Interacting Boson Model (IBM). This model undergoes a transition order-chaos-order from the $SU(3)$ limit to the $O(6)$ limit. Our analysis shows that the quantum fluctuations of the IBM Hamiltonian, both of the spectrum and the eigenvectors, follow the expected behaviour predicted by the DGOE when one goes from one limit to the other.
Modelling of the water retention characteristic of deformable soils
Directory of Open Access Journals (Sweden)
Wang Yu
2016-01-01
Full Text Available A recently proposed water retention model has been further developed for the application on unsaturated deformable soils. The physical mechanisms underpinning the water retention characteristic of soils was at first described in terms of traditional theories of capillarity and interfacial physical chemistry at pore level. Then upscaling to macroscopic level of material scale in terms of average volume theorem produces an analytical formula for the water retention characteristic. The methodology produces an explicit form of the water retention curve as a function of three state parameters: the suction, the degree-of-water-saturation and the void-ratio. At last, the model has been tested using experimental measurements.
A Deformable Model for Bringing Particles in Focus
DEFF Research Database (Denmark)
Dahl, Anders Lindbjerg; Jørgensen, Thomas Martini; Larsen, Rasmus
2010-01-01
We provide a deformable model for particle analysis. We in- vestigate particle images from a backlit microscope system where parti- cles suer from out-of-focus blur. The blur is a result of particles being in front or behind the focus plane, and the out-of-focus gives a bias towards overestimatin...... demonstrate the capa- bilities of our model on both real and simulated data, and our approach shows promising results for a reliable particle analysis. The potential is more process information obtained over shorter sampling time....
Winding vacuum energies in a deformed O(4) sigma model
Bazhanov, Vladimir V; Lukyanov, Sergei L
2014-01-01
We consider the problem of calculating the Casimir energies in the winding sectors of Fateev's SS-model, which is an integrable two-parameter deformation of the O(4) non-linear sigma model in two dimensions. This problem lies beyond the scope of all traditional methods of integrable quantum field theory including the thermodynamic Bethe ansatz and non-linear integral equations. Here we propose a solution based on a remarkable correspondence between classical and quantum integrable systems and express the winding energies in terms of certain solutions of the classical sinh-Gordon equation.
Winding vacuum energies in a deformed O(4) sigma model
Energy Technology Data Exchange (ETDEWEB)
Bazhanov, Vladimir V. [Department of Theoretical Physics, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200 (Australia); Mathematical Sciences Institute, Australian National University, Canberra, ACT 0200 (Australia); Kotousov, Gleb A. [Department of Theoretical Physics, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200 (Australia); Lukyanov, Sergei L., E-mail: sergei@physics.rutgers.edu [NHETC, Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08855-0849 (United States); L.D. Landau Institute for Theoretical Physics, Chernogolovka 142432 (Russian Federation)
2014-12-15
We consider the problem of calculating the Casimir energies in the winding sectors of Fateev's SS-model, which is an integrable two-parameter deformation of the O(4) non-linear sigma model in two dimensions. This problem lies beyond the scope of all traditional methods of integrable quantum field theory including the thermodynamic Bethe ansatz and non-linear integral equations. Here we propose a solution based on a remarkable correspondence between classical and quantum integrable systems and express the winding energies in terms of certain solutions of the classical sinh-Gordon equation.
ACCUMULATED DEFORMATION MODELING OF PERMANENT WAY BASED ON ENTROPY SYSTEM
Directory of Open Access Journals (Sweden)
D. M. Kurhan
2015-07-01
Full Text Available Purpose. The work provides a theoretical research about the possibility of using methods that determine the lifetime of a railway track not only in terms of total stresses, and accounting its structure and dynamic characteristics. The aim of these studies is creation the model of deformations accumulation for assessment of service life of a railway track taking into account these features. Methodology. To simulate a gradual change state during the operation (accumulation of deformations the railway track is presented as a system that consists of many particles of different materials collected in a coherent design. It is appropriate to speak not about the appearance of deformations of a certain size in a certain section of the track, and the probability of such event on the site. If to operate the probability of occurrence of deviations, comfortable state of the system is characterized by the number of breaks of the conditional internal connections. The same state of the system may correspond to different combinations of breaks. The more breaks, the more the number of options changes in the structure of the system appropriate to its current state. Such a process can be represented as a gradual transition from an ordered state to a chaotic one. To describe the characteristics of the system used the numerical value of the entropy. Findings. Its entropy is constantly increasing at system aging. The growth of entropy is expressed by changes in the internal energy of the system, which can be determined using mechanical work forces, which leads to deformation. This gives the opportunity to show quantitative indication of breaking the bonds in the system as a consequence of performing mechanical work. According to the results of theoretical research methods for estimation of the timing of life cycles of railway operation considering such factors as the structure of the flow of trains, construction of the permanent way, the movement of trains at high
Richeton, T.; Le, LT; Chauve, T.; Bernacki, M.; Berbenni, S.; Montagnat, M.
2017-02-01
A model based on the elastic theory of continuously distributed dislocations, accounting for the transport of geometrically necessary dislocations (GND) on slip systems is developed. It allows keeping the crystallographic nature of glide by allocating velocities specific to slip systems to GND. At grain boundaries, the dislocation transport equation is resolved between a specific system in a grain and a specific system in the adjacent grain. It is used to simulate a compression creep test followed by unloading of a multiple slip deforming multi-crystal of ice during which kink band formation, grain boundary migration and localized grain nucleation are observed. The model predictions are compared to 2D strain fields obtained by digital image correlation and show a good agreement. Besides, the kink band position corresponds very well with an area of strong lattice misorientation predicted by the model and is also bounded by opposite densities of edge dislocations, in agreement with kink banding theory and characterization. Furthermore, the grain boundary migration is observed to happen from predicted low dislocation density area towards high dislocation ones—also in agreement with the theory. Lastly, the triple junctions where nucleation is observed are also characterized by high GND density and especially strong gradient of elastic energy density. These different features show the relevance of using a continuum theory of polarized dislocations per slip system to study the onset of relaxation mechanisms like kink banding, grain boundary migration and grain nucleation and possibly to propose nucleation and migration criteria.
Directory of Open Access Journals (Sweden)
Q. Xin
2015-02-01
Full Text Available Modeling vegetation photosynthesis is essential for understanding carbon exchanges between terrestrial ecosystems and the atmosphere. The radiative transfer process within plant canopies is one of the key drivers that regulate canopy photosynthesis. Most vegetation cover consists of discrete plant crowns, of which the physical observation departs from the underlying assumption of a homogenous and uniform medium in classic radiative transfer theory. Here we advance the Geometric Optical Radiative Transfer (GORT model to simulate photosynthesis activities for discontinuous plant canopies. We separate radiation absorption into two components that are absorbed by sunlit and shaded leaves, and derive analytical solutions by integrating over the canopy layer. To model leaf-level and canopy-level photosynthesis, leaf light absorption is then linked to the biochemical process of gas diffusion through leaf stomata. The canopy gap probability derived from GORT differs from classic radiative transfer theory, especially when the leaf area index is high, due to leaf clumping effects. Tree characteristics such as tree density, crown shape, and canopy length affect leaf clumping and regulate radiation interception. Modeled gross primary production (GPP for two deciduous forest stands could explain more than 80% of the variance of flux tower measurements at both near hourly and daily time scales. We also demonstrate that the ambient CO2 concentration influences daytime vegetation photosynthesis, which needs to be considered in state-of-the-art biogeochemical models. The proposed model is complementary to classic radiative transfer theory and shows promise in modeling the radiative transfer process and photosynthetic activities over discontinuous forest canopies.
Facial Performance Transfer via Deformable Models and Parametric Correspondence.
Asthana, Akshay; de la Hunty, Miles; Dhall, Abhinav; Goecke, Roland
2012-09-01
The issue of transferring facial performance from one person's face to another's has been an area of interest for the movie industry and the computer graphics community for quite some time. In recent years, deformable face models, such as the Active Appearance Model (AAM), have made it possible to track and synthesize faces in real time. Not surprisingly, deformable face model-based approaches for facial performance transfer have gained tremendous interest in the computer vision and graphics community. In this paper, we focus on the problem of real-time facial performance transfer using the AAM framework. We propose a novel approach of learning the mapping between the parameters of two completely independent AAMs, using them to facilitate the facial performance transfer in a more realistic manner than previous approaches. The main advantage of modeling this parametric correspondence is that it allows a "meaningful" transfer of both the nonrigid shape and texture across faces irrespective of the speakers' gender, shape, and size of the faces, and illumination conditions. We explore linear and nonlinear methods for modeling the parametric correspondence between the AAMs and show that the sparse linear regression method performs the best. Moreover, we show the utility of the proposed framework for a cross-language facial performance transfer that is an area of interest for the movie dubbing industry.
Micromechanical modeling of the deformation of HCP metals
Energy Technology Data Exchange (ETDEWEB)
Graff, S. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Materialforschung
2008-12-04
Nowadays, intense research is conducted to understand the relation between microstructural features and mechanical properties of hexagonal close-packed (hcp) metals. Due to their hexagonal structure, hcp metals exhibit mechanical properties such as strong anisotropy, which is more pronounced than for construction metals with cubic crystal structure, and tension/compression asymmetry. Deformation mechanisms in hcp metals, dislocation motion on specific slip systems and activation of twinning, are not yet completely understood. The purpose of this work is to link the physical mechanisms developing during deformation of magnesium (Mg) on the microscale with the macroscopic yielding properties of texture Mg samples. It will be shown that the mechanical behavior of hcp metals may be understood and reproduced with the help of a visco-plastic model for crystal plasticity and a phenomenological yield criterion with appropriate hardening behavior. The study of single crystal specimens subjected to channel die compression tests reveals the active slip systems and twinning systems of the material considered. The material anisotropy at mesoscale is reproduced by using adequate critical resolved shear stresses (CRSS) for the considered deformation mechanisms. In order to describe the macroscopic behavior, texture is incorporated into polycrystalline Representative Volume Elements (RVEs) and various mechanical properties of extruded bars and rolled plates can be predicted. For RVEs exhibiting the texture of rolled plates the numerical results reveal the plate's anisotropic yielding and hardening behavior on a mesoscale. In order to extend the modeling possibilities to process simulations and to allow for time-saving simulations of structural behavior, a phenomenological yield surface accounting for anisotropy and tension/compression asymmetry has been established and implemented in a finite element code. Its numerous model parameters are calibrated by an optimization
Fuzzy Decision-Making Approach in Geometric Programming for a Single Item EOQ Model
Directory of Open Access Journals (Sweden)
Monalisha Pattnaik
2015-06-01
Full Text Available Background and methods: Fuzzy decision-making approach is allowed in geometric programming for a single item EOQ model with dynamic ordering cost and demand-dependent unit cost. The setup cost varies with the quantity produced/purchased and the modification of objective function with storage area in the presence of imprecisely estimated parameters are investigated. It incorporates all concepts of a fuzzy arithmetic approach, the quantity ordered, and demand per unit compares both fuzzy geometric programming technique and other models for linear membership functions. Results and conclusions: Investigation of the properties of an optimal solution allows developing an algorithm whose validity is illustrated through an example problem and the results discu ssed. Sensitivity analysis of the optimal solution is also studied with respect to changes in different parameter values.
Partial SUSY Breaking for Asymmetric Gepner Models and Non-geometric Flux Vacua
Blumenhagen, Ralph; Plauschinn, Erik
2016-01-01
Using the method of simple current extensions, asymmetric Gepner models of Type IIB with N=1 space-time supersymmetry are constructed. The combinatorics of the massless vector fields suggests that these classical Minkowski string vacua provide fully backreacted solutions corresponding to N=1 minima of N=2 gauged supergravity. The latter contain abelian gaugings along the axionic isometries in the hypermultiplet moduli space, and can be considered as Type IIB flux compactifications on Calabi-Yau manifolds equipped with (non-)geometric fluxes. For a particular class of asymmetric Gepner models, we are able to explicitly specify the underlying CICYs and to check necessary conditions for a GSUGRA interpretation. If this conjecture is correct, there exists a large class of exactly solvable non-geometric flux compactifications on CY threefolds.
Institute of Scientific and Technical Information of China (English)
SHAO Zhi-gang; FU Rong-shan; XUE Ting-xiao; ZHA Xian-jie
2008-01-01
In this paper, we firstly use finite element method (FEM) with Burgers model to simulate the postseismic viscoe- lastic relaxation taking 1960 Chile earthquake as an example. The postseismic deformation modeled with Burgers model includes co-seismic deformation, transient postseismic deformation and long-term postseismic deformation. So if we apply Burgers model to calculate postseismic deformation of 1960 Chile earthquake, there is no discrep- ancy phenomenon due to different durations of postseismic deformations that happens in Maxwell model.
Transferable Deformation-Dipole Model for Ionic Materials
Karaman, Ali; Akdeniz, Zehra; Tosi, Mario P.
2007-06-01
A model for the ionic interactions in polyvalent metal halides was originally built for chloroaluminate clusters using an analysis of data on static and dynamic structure of their molecular monomers [for a review see M. P. Tosi, Phys. Chem. Liquids 43, 409 (2005)]. Recently, by continuing the deformation-dipole model calculations, the transferability of the halogen parameters was tested through the calculation of the structure of alkali halides and alkaline-earth halides. In this work we test the usefulness of the deformation-dipole model in the study of ionic materials by examining the transferability of the overlap parameters for the halogen ions across families of halide compounds. Following a comparative discussion of alkali and alkaline-earth halide monomers near equilibrium, results on alkaline-earth halides are given. By using the transferable ionic potential model we also calculate the equilibrium structure of the molecular clusters, as well as the vibrational frequencies of ACl4 compounds (where A = U, Np, Pu, Am and Th).
A coupled model for intragranular deformation and chemical diffusion
Zhong, Xin; Vrijmoed, Johannes; Moulas, Evangelos; Tajčmanová, Lucie
2017-09-01
A coupled model for chemical diffusion and mechanical deformation is developed in analogy to the studies of poroelasticity and thermoelasticity. Nondimensionalization of the governing equations yields a controlling dimensionless parameter, the Deborah number, given by the ratio of the characteristic time for pressure relaxation and concentration homogenization. Using the Deborah number two types of plausible chemical zonation are distinguished, i.e. diffusion controlled, and mechanically controlled. The transition between these two types of chemical zonation is determined at the conditions where the Deborah number equals one. We apply our model to a chemically zoned plagioclase rim in a spherical coordinate frame assuming homogeneous initial pressure. Using thermodynamic data, an experimentally derived diffusion coefficient and a viscous flow law for plagioclase, our numerical simulations show that up to ∼0.6 GPa grain-scale pressure variation is generated during the diffusion-deformation process. Due to the mechanical-chemical coupling, the pressure variations maintain the chemical zonation longer than predicted by the classical diffusion model. The fully coupled mechanical-chemical model provides an alternative explanation for the preservation of chemically zoned minerals, and may contribute to a better understanding of metamorphic processes in the deep Earth interior.
Studies on a Double Poisson-Geometric Insurance Risk Model with Interference
Directory of Open Access Journals (Sweden)
Yujuan Huang
2013-01-01
Full Text Available This paper mainly studies a generalized double Poisson-Geometric insurance risk model. By martingale and stopping time approach, we obtain adjustment coefficient equation, the Lundberg inequality, and the formula for the ruin probability. Also the Laplace transformation of the time when the surplus reaches a given level for the first time is discussed, and the expectation and its variance are obtained. Finally, we give the numerical examples.
Institute of Scientific and Technical Information of China (English)
李双; 冯笙琴
2012-01-01
The net-baryon number is essentially transported by valence quarks that probe the saturation regime in the target by multiple scattering. The net-baryon distributions, nuclear stopping power and gluon saturation features in the SPS and RHIC energy regions are investigated by taking advantage of the gluon saturation model with geometric scaling. Predications are made for the net-baryon rapidity distributions, mean rapidity loss and gluon saturation features in central Pb ＋ Pb collisions at LHC.
Kolb, Martin; Wubker, Achim
2011-01-01
We analyze the large time behavior of a stochastic model for the lay-down of fibers on a conveyor belt in the production process of nonwovens. It is shown, that under weak conditions this degenerate diffusion process is strong mixing, confirming a conjecture of Grothaus and Klar. Moreover, under some additional assumptions even geometric ergodicity is established using probabilistic tools -- described in the book of Meyn and Tweedie -- in combination with methods from stochastic analysis.
Institute of Scientific and Technical Information of China (English)
Yuan Guanglin; Shu Qianjin; Zhang Yunfei; Liu Tao; Ji Yongsheng; Xu Guoan
2012-01-01
A large number of high-voltage power transmission towers have recently been constructed in mining areas prone to subsidence.In order to ensure the safety of the transmission towers and the safe operation of transmission systems,it is imperative to carry out research on the anti-deformation performance of transmission towers.In our study,we performed experiments on the anti-deformation performance of a transmission tower in a subsidence area on a scale model with a geometric scale ratio of 1∶5 and analyzed the failure mechanism of the tower members.The results show that,when the axial distance between two supports changes,destabilization failure most likely occurs in the members of the bottom transverse layer because some parts of the main diagonal member bars yield under the action of compression.The failure mechanism of the tower members basically coincides with the lever principle.
Modeling Recrystallization of Austenite for C-Mn Steels during Hot Deformation by Cellular Automaton
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
By using a cellular automaton method, microstructure evolution of recrystallization in austenite during hot deformation was simulated for C-Mn steels. A model takes into account the influence of deformation temperature, strain, and strain rate on the dynamic recrystallization fraction, and the effect of the keeping time on the static recrystallization fraction based on a hot deformation test on a Gleeble-1500 simulator. In addition, the size changing of γ grains during continuous hot deformation was simulated by applying the model.
Energy Technology Data Exchange (ETDEWEB)
Battaile, C.C.; Buchheit, T.E.; Holm, E.A.; Neilsen, M.K.; Wellman, G.W.
1999-01-12
The microstructural evolution of heavily deformed polycrystalline Cu is simulated by coupling a constitutive model for polycrystal plasticity with the Monte Carlo Potts model for grain growth. The effects of deformation on boundary topology and grain growth kinetics are presented. Heavy deformation leads to dramatic strain-induced boundary migration and subsequent grain fragmentation. Grain growth is accelerated in heavily deformed microstructures. The implications of these results for the thermomechanical fatigue failure of eutectic solder joints are discussed.
A Large Deformation Model for the Elastic Moduli of Two-dimensional Cellular Materials
Institute of Scientific and Technical Information of China (English)
HU Guoming; WAN Hui; ZHANG Youlin; BAO Wujun
2006-01-01
We developed a large deformation model for predicting the elastic moduli of two-dimensional cellular materials. This large deformation model was based on the large deflection of the inclined members of the cells of cellular materials. The deflection of the inclined member, the strain of the representative structure and the elastic moduli of two-dimensional cellular materials were expressed using incomplete elliptic integrals. The experimental results show that these elastic moduli are no longer constant at large deformation, but vary significantly with the strain. A comparison was made between this large deformation model and the small deformation model proposed by Gibson and Ashby.
Viscoelastoplastic constitutive model for creep deformation behavior of asphalt sand
Institute of Scientific and Technical Information of China (English)
叶永; 杨新华; 陈传尧
2008-01-01
A uniaxial viscoelastoplastic model that can describe whole creep behaviors of asphalt sand at different temperatures was presented.The model was composed of three submodels in series,which describe elastoplastic,viscoelastic and viscoplastic characteristics respectively.The constitutive equation was established for uniaxial loading condition,and the creep representation was also obtained.The constitutive parameters were determined by uniaxial compression tests under controlled-stress of 0.1 MPa with five different test temperatures of 20,40,45,50 and 60 ℃.Expressions of the model parameters in terms of temperatures were also given.The model gave prediction at various temperatures consistent with the experimental results,and can reflect the total deformation characterization of asphalt sands.
Modeling and Simulation of Grasping of Deformable Objects
DEFF Research Database (Denmark)
Fugl, Andreas Rune
Automated robot solutions have for decades been increasing productivity around the world. They are attractive for being fast, accurate and able to work in dangerous and repetitive environments. In traditional applications the grasped object is kinematically attached to the Tool Center Point....... The purpose of this thesis is to address the modeling and simulation of deformable objects, as applied to robotic grasping and manipulation. The main contributions of this work are: An evaluation of 3D linear elasticity used for robot grasping as implemented by a Finite Difference Method supporting regular...
A note on solutions of an equation modelling arterial deformation
Energy Technology Data Exchange (ETDEWEB)
Gordoa, P.R. [Area de Matematica Aplicada, ESCET, Universidad Rey Juan Carlos, C/ Tulipan s/n, 28933 Mostoles, Madrid (Spain)]. E-mail: pilar.gordoa@urjc.es
2007-08-15
The derivation of exact solutions for a partial differential equation modelling arterial deformation in large arteries is considered. Amongst other results, we show that, for any values of the parameters appearing in the equation, solutions in terms of the first Painleve transcendent can be obtained. This is in spite of the non-integrability of the equation. We also establish a connection, via an approximation of the equation under study by the Korteweg-de Vries equation, with the second Painleve equation. Our results thus serve to further demonstrate the wide applicability and importance of the Painleve equations.
Neural Network method for Inverse Modeling of Material Deformation
Energy Technology Data Exchange (ETDEWEB)
Allen, J.D., Jr.; Ivezic, N.D.; Zacharia, T.
1999-07-10
A method is described for inverse modeling of material deformation in applications of importance to the sheet metal forming industry. The method was developed in order to assess the feasibility of utilizing empirical data in the early stages of the design process as an alternative to conventional prototyping methods. Because properly prepared and employed artificial neural networks (ANN) were known to be capable of codifying and generalizing large bodies of empirical data, they were the natural choice for the application. The product of the work described here is a desktop ANN system that can produce in one pass an accurate die design for a user-specified part shape.
Fractal and prefractal geometric models have substantial potential of contributing to the analysis of flow and transport in porous media such as soils and reservoir rocks. In this study, geometric and hydrodynamic parameters of saturated 3D mass and pore-solid prefractal porous media were characteri...
Telfer, Scott; Erdemir, Ahmet; Woodburn, James; Cavanagh, Peter R
2016-01-25
Integration of patient-specific biomechanical measurements into the design of therapeutic footwear has been shown to improve clinical outcomes in patients with diabetic foot disease. The addition of numerical simulations intended to optimise intervention design may help to build on these advances, however at present the time and labour required to generate and run personalised models of foot anatomy restrict their routine clinical utility. In this study we developed second-generation personalised simple finite element (FE) models of the forefoot with varying geometric fidelities. Plantar pressure predictions from barefoot, shod, and shod with insole simulations using simplified models were compared to those obtained from CT-based FE models incorporating more detailed representations of bone and tissue geometry. A simplified model including representations of metatarsals based on simple geometric shapes, embedded within a contoured soft tissue block with outer geometry acquired from a 3D surface scan was found to provide pressure predictions closest to the more complex model, with mean differences of 13.3kPa (SD 13.4), 12.52kPa (SD 11.9) and 9.6kPa (SD 9.3) for barefoot, shod, and insole conditions respectively. The simplified model design could be produced in 3h in the case of the more detailed model, and solved on average 24% faster. FE models of the forefoot based on simplified geometric representations of the metatarsal bones and soft tissue surface geometry from 3D surface scans may potentially provide a simulation approach with improved clinical utility, however further validity testing around a range of therapeutic footwear types is required.
Finite Element Model and Validation of Nasal Tip Deformation.
Manuel, Cyrus T; Harb, Rani; Badran, Alan; Ho, David; Wong, Brian J F
2017-03-01
Nasal tip mechanical stability is important for functional and cosmetic nasal airway surgery. Palpation of the nasal tip provides information on tip strength to the surgeon, though it is a purely subjective assessment. Providing a means to simulate nasal tip deformation with a validated model can offer a more objective approach in understanding the mechanics and nuances of the nasal tip support and eventual nasal mechanics as a whole. Herein we present validation of a finite element (FE) model of the nose using physical measurements recorded using an ABS plastic-silicone nasal phantom. Three-dimensional photogrammetry was used to capture the geometry of the phantom at rest and while under steady state load. The silicone used to make the phantom was mechanically tested and characterized using a linear elastic constitutive model. Surface point clouds of the silicone and FE model were compared for both the loaded and unloaded state. The average Hausdorff distance between actual measurements and FE simulations across the nose were 0.39 ± 1.04 mm and deviated up to 2 mm at the outermost boundaries of the model. FE simulation and measurements were in near complete agreement in the immediate vicinity of the nasal tip with millimeter accuracy. We have demonstrated validation of a two-component nasal FE model, which could be used to model more complex modes of deformation where direct measurement may be challenging. This is the first step in developing a nasal model to simulate nasal mechanics and ultimately the interaction between geometry and airflow.
Bethe ansatz and Isomonodromic deformations
Talalaev, D
2008-01-01
We study symmetries of the Bethe equations for the Gaudin model appeared naturally in the framework of the geometric Langlands correspondence under the name of Hecke operators and under the name of Schlesinger transformations in the theory of isomonodromic deformations, and particularly in the theory of Painlev\\'e transcendents.
Modeling and Prediction of Hot Deformation Flow Curves
Mirzadeh, Hamed; Cabrera, Jose Maria; Najafizadeh, Abbas
2012-01-01
The modeling of hot flow stress and prediction of flow curves for unseen deformation conditions are important in metal-forming processes because any feasible mathematical simulation needs accurate flow description. In the current work, in an attempt to summarize, generalize, and introduce efficient methods, the dynamic recrystallization (DRX) flow curves of a 17-4 PH martensitic precipitation hardening stainless steel, a medium carbon microalloyed steel, and a 304 H austenitic stainless steel were modeled and predicted using (1) a hyperbolic sine equation with strain dependent constants, (2) a developed constitutive equation in a simple normalized stress-normalized strain form and its modified version, and (3) a feed-forward artificial neural network (ANN). These methods were critically discussed, and the ANN technique was found to be the best for the modeling available flow curves; however, the developed constitutive equation showed slightly better performance than that of ANN and significantly better predicted values than those of the hyperbolic sine equation in prediction of flow curves for unseen deformation conditions.
Lin, Y. K.; Ke, M. C.; Ke, S. S.
2016-12-01
An active fault is commonly considered to be active if they have moved one or more times in the last 10,000 years and likely to have another earthquake sometime in the future. The relationship between the fault reactivation and the surface deformation after the Chi-Chi earthquake (M=7.2) in 1999 has been concerned up to now. According to the investigations of well-known disastrous earthquakes in recent years, indicated that surface deformation is controlled by the 3D fault geometric shape. Because the surface deformation may cause dangerous damage to critical infrastructures, buildings, roads, power, water and gas lines etc. Therefore it's very important to make pre-disaster risk assessment via the 3D active fault model to decrease serious economic losses, people injuries and deaths caused by large earthquake. The approaches to build up the 3D active fault model can be categorized as (1) field investigation (2) digitized profile data and (3) build the 3D modeling. In this research, we tracked the location of the fault scarp in the field first, then combined the seismic profiles (had been balanced) and historical earthquake data to build the underground fault plane model by using SKUA-GOCAD program. Finally compared the results come from trishear model (written by Richard W. Allmendinger, 2012) and PFC-3D program (Itasca) and got the calculated range of the deformation area. By analysis of the surface deformation area made from Hsin-Chu Fault, we concluded the result the damage zone is approaching 68 286m, the magnitude is 6.43, the offset is 0.6m. base on that to estimate the population casualties, building damage by the M=6.43 earthquake in Hsin-Chu area, Taiwan. In the future, in order to be applied accurately on earthquake disaster prevention, we need to consider further the groundwater effect and the soil structure interaction inducing by faulting.
Monte Carlo based geometrical model for efficiency calculation of an n-type HPGe detector
Energy Technology Data Exchange (ETDEWEB)
Padilla Cabal, Fatima, E-mail: fpadilla@instec.c [Instituto Superior de Tecnologias y Ciencias Aplicadas, ' Quinta de los Molinos' Ave. Salvador Allende, esq. Luaces, Plaza de la Revolucion, Ciudad de la Habana, CP 10400 (Cuba); Lopez-Pino, Neivy; Luis Bernal-Castillo, Jose; Martinez-Palenzuela, Yisel; Aguilar-Mena, Jimmy; D' Alessandro, Katia; Arbelo, Yuniesky; Corrales, Yasser; Diaz, Oscar [Instituto Superior de Tecnologias y Ciencias Aplicadas, ' Quinta de los Molinos' Ave. Salvador Allende, esq. Luaces, Plaza de la Revolucion, Ciudad de la Habana, CP 10400 (Cuba)
2010-12-15
A procedure to optimize the geometrical model of an n-type detector is described. Sixteen lines from seven point sources ({sup 241}Am, {sup 133}Ba, {sup 22}Na, {sup 60}Co, {sup 57}Co, {sup 137}Cs and {sup 152}Eu) placed at three different source-to-detector distances (10, 20 and 30 cm) were used to calibrate a low-background gamma spectrometer between 26 and 1408 keV. Direct Monte Carlo techniques using the MCNPX 2.6 and GEANT 4 9.2 codes, and a semi-empirical procedure were performed to obtain theoretical efficiency curves. Since discrepancies were found between experimental and calculated data using the manufacturer parameters of the detector, a detail study of the crystal dimensions and the geometrical configuration is carried out. The relative deviation with experimental data decreases from a mean value of 18-4%, after the parameters were optimized.
Directory of Open Access Journals (Sweden)
Jasmine Norman
2011-10-01
Full Text Available Random Geometric Graphs have been a very influential and well-studied model of large networks, such assensor networks, where the network nodes are represented by the vertices of the RGG, and the direct connectivity between nodes is represented by the edges. This assumes homogeneous wireless nodes with uniform transmission ranges. In real life, there exist heterogeneous wireless networks in which devices have dramatically different capabilities. The connectivity of a WSN is related to the positions of nodes, and those positions are heavily affected by the method of sensor deployment. As sensors may be spread in an arbitrary manner, one of the fundamental issues in a wireless sensor network is the coverage problem. In this paper, I study connectivity and coverage in hybrid WSN based on dynamic random geometric graph.
Monte Carlo based geometrical model for efficiency calculation of an n-type HPGe detector.
Cabal, Fatima Padilla; Lopez-Pino, Neivy; Bernal-Castillo, Jose Luis; Martinez-Palenzuela, Yisel; Aguilar-Mena, Jimmy; D'Alessandro, Katia; Arbelo, Yuniesky; Corrales, Yasser; Diaz, Oscar
2010-12-01
A procedure to optimize the geometrical model of an n-type detector is described. Sixteen lines from seven point sources ((241)Am, (133)Ba, (22)Na, (60)Co, (57)Co, (137)Cs and (152)Eu) placed at three different source-to-detector distances (10, 20 and 30 cm) were used to calibrate a low-background gamma spectrometer between 26 and 1408 keV. Direct Monte Carlo techniques using the MCNPX 2.6 and GEANT 4 9.2 codes, and a semi-empirical procedure were performed to obtain theoretical efficiency curves. Since discrepancies were found between experimental and calculated data using the manufacturer parameters of the detector, a detail study of the crystal dimensions and the geometrical configuration is carried out. The relative deviation with experimental data decreases from a mean value of 18-4%, after the parameters were optimized.
Scaling of geometric phase versus band structure in cluster-Ising models
Nie, Wei; Mei, Feng; Amico, Luigi; Kwek, Leong Chuan
2017-08-01
We study the phase diagram of a class of models in which a generalized cluster interaction can be quenched by an Ising exchange interaction and external magnetic field. The various phases are studied through winding numbers. They may be ordinary phases with local order parameters or exotic ones, known as symmetry protected topologically ordered phases. Quantum phase transitions with dynamical critical exponents z =1 or z =2 are found. In particular, the criticality is analyzed through finite-size scaling of the geometric phase accumulated when the spins of the lattice perform an adiabatic precession. With this study, we quantify the scaling behavior of the geometric phase in relation to the topology and low-energy properties of the band structure of the system.
Statistical Modeling of CTV Motion and Deformation for IMRT of Early-Stage Rectal Cancer
Energy Technology Data Exchange (ETDEWEB)
Bondar, Luiza, E-mail: M.L.Bondar@umcutrecht.nl [Department of Radiotherapy, University Medical Center Utrecht, Utrecht (Netherlands); Intven, Martijn; Burbach, J.P. Maarten [Department of Radiotherapy, University Medical Center Utrecht, Utrecht (Netherlands); Budiarto, Eka [Delft Institute of Applied Mathematics, Delft University of Technology, Delft (Netherlands); Kleijnen, Jean-Paul; Philippens, Marielle; Asselen, Bram van; Seravalli, Enrica; Reerink, Onne; Raaymakers, Bas [Department of Radiotherapy, University Medical Center Utrecht, Utrecht (Netherlands)
2014-11-01
Purpose: To derive and validate a statistical model of motion and deformation for the clinical target volume (CTV) of early-stage rectal cancer patients. Methods and Materials: For 16 patients, 4 to 5 magnetic resonance images (MRI) were acquired before each fraction was administered. The CTV was delineated on each MRI. Using a leave-one-out methodology, we constructed a population-based principal component analysis (PCA) model of the CTV motion and deformation of 15 patients, and we tested the model on the left-out patient. The modeling error was calculated as the amount of the CTV motion-deformation of the left-out-patient that could not be explained by the PCA model. Next, the PCA model was used to construct a PCA target volume (PCA-TV) by accumulating motion-deformations simulated by the model. A PCA planning target volume (PTV) was generated by expanding the PCA-TV by uniform margins. The PCA-PTV was compared with uniform and nonuniform CTV-to-PTV margins. To allow comparison, geometric margins were determined to ensure adequate coverage, and the volume difference between the PTV and the daily CTV (CTV-to-PTV volume) was calculated. Results: The modeling error ranged from 0.9 ± 0.5 to 2.9 ± 2.1 mm, corresponding to a reduction of the CTV motion-deformation between 6% and 60% (average, 23% ± 11%). The reduction correlated with the magnitude of the CTV motion-deformation (P<.001, R=0.66). The PCA-TV and the CTV required 2-mm and 7-mm uniform margins, respectively. The nonuniform CTV-to-PTV margins were 4 mm in the left, right, inferior, superior, and posterior directions and 8 mm in the anterior direction. Compared to uniform and nonuniform CTV-to-PTV margins, the PCA-based PTV significantly decreased (P<.001) the average CTV-to-PTV volume by 128 ± 20 mL (49% ± 4%) and by 35 ± 6 mL (20% ± 3.5%), respectively. Conclusions: The CTV motion-deformation of a new patient can be explained by a population-based PCA model. A PCA model
Multi-view and 3D deformable part models.
Pepik, Bojan; Stark, Michael; Gehler, Peter; Schiele, Bernt
2015-11-01
As objects are inherently 3D, they have been modeled in 3D in the early days of computer vision. Due to the ambiguities arising from mapping 2D features to 3D models, 3D object representations have been neglected and 2D feature-based models are the predominant paradigm in object detection nowadays. While such models have achieved outstanding bounding box detection performance, they come with limited expressiveness, as they are clearly limited in their capability of reasoning about 3D shape or viewpoints. In this work, we bring the worlds of 3D and 2D object representations closer, by building an object detector which leverages the expressive power of 3D object representations while at the same time can be robustly matched to image evidence. To that end, we gradually extend the successful deformable part model [1] to include viewpoint information and part-level 3D geometry information, resulting in several different models with different level of expressiveness. We end up with a 3D object model, consisting of multiple object parts represented in 3D and a continuous appearance model. We experimentally verify that our models, while providing richer object hypotheses than the 2D object models, provide consistently better joint object localization and viewpoint estimation than the state-of-the-art multi-view and 3D object detectors on various benchmarks (KITTI [2] , 3D object classes [3] , Pascal3D+ [4] , Pascal VOC 2007 [5] , EPFL multi-view cars[6] ).
Modeling Permanent Deformations of Superelastic and Shape Memory Materials
Directory of Open Access Journals (Sweden)
Marco Fabrizio Urbano
2015-06-01
Full Text Available In this paper we propose a modification of the polycrystalline shape memory alloy constitutive model originally proposed by Souza. By introducing a transformation strain energy with two different hardening coefficients, we are able to take into account the effect of the martensitic transformation of unfavorably oriented grains occurring after the main plateau. By choosing a proper second hardening coefficient, it is possible to reproduce the correct stress strain behavior of the material after the plateau without the need of introducing a much smaller Young modulus for martensite. The proposed modification is introduced in the model comprising permanent deformation effects. Model results for uniaxial stress tests are compared to experimental results showing good agreement.
Modeling of microelectromechanical systems deformable mirror diffraction grating
Sirbu, Dan; Pluzhnik, Eugene; Belikov, Ruslan
2016-07-01
Model-based wavefront control methods such as electric field conjugation require accurate optical propagation models to create high-contrast regions in the focal plane using deformable mirrors (DMs). Recently, it has been shown that it is possible to exceed the controllable outer-working angle imposed by the Nyquist limit based on the number of actuators by utilizing a diffraction grating. The print-through pattern on MEMS-based DMs formed during the fabrication process creates both an amplitude and a phase diffraction grating that can be used to enable Super-Nyquist wavefront control. Using interferometric measurements of a DM-actuator, we develop a DM-diffraction grating model. We compare the total energy enclosed in the first diffraction order due to the phase, amplitude, and combined phase-amplitude gratings with laboratory measurements.
Modeling Permanent Deformations of Superelastic and Shape Memory Materials
Urbano, Marco Fabrizio; Auricchio, Ferdinando
2015-01-01
In this paper we propose a modification of the polycrystalline shape memory alloy constitutive model originally proposed by Souza. By introducing a transformation strain energy with two different hardening coefficients, we are able to take into account the effect of the martensitic transformation of unfavorably oriented grains occurring after the main plateau. By choosing a proper second hardening coefficient, it is possible to reproduce the correct stress strain behavior of the material after the plateau without the need of introducing a much smaller Young modulus for martensite. The proposed modification is introduced in the model comprising permanent deformation effects. Model results for uniaxial stress tests are compared to experimental results showing good agreement. PMID:26110494
FEMUR SHAPE RECOVERY FROM VOLUMETRIC IMAGES USING 3-D DEFORMABLE MODELS
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
A new scheme for femur shape recovery from volumetric images using deformable models was proposed. First, prior 3-D deformable femur models are created as templates using point distribution models technology. Second, active contour models are employed to segment the magnetic resonance imaging (MRI) volumetric images of the tibial and femoral joints and the deformable models are initialized based on the segmentation results. Finally, the objective function is minimized to give the optimal results constraining the surface of shapes.
Phase field modeling of partially saturated deformable porous media
Sciarra, Giulio
2016-09-01
A poromechanical model of partially saturated deformable porous media is proposed based on a phase field approach at modeling the behavior of the mixture of liquid water and wet air, which saturates the pore space, the phase field being the saturation (ratio). While the standard retention curve is expected still^ to provide the intrinsic retention properties of the porous skeleton, depending on the porous texture, an enhanced description of surface tension between the wetting (liquid water) and the non-wetting (wet air) fluid, occupying the pore space, is stated considering a regularization of the phase field model based on an additional contribution to the overall free energy depending on the saturation gradient. The aim is to provide a more refined description of surface tension interactions. An enhanced constitutive relation for the capillary pressure is established together with a suitable generalization of Darcy's law, in which the gradient of the capillary pressure is replaced by the gradient of the so-called generalized chemical potential, which also accounts for the "force", associated to the local free energy of the phase field model. A micro-scale heuristic interpretation of the novel constitutive law of capillary pressure is proposed, in order to compare the envisaged model with that one endowed with the concept of average interfacial area. The considered poromechanical model is formulated within the framework of strain gradient theory in order to account for possible effects, at laboratory scale, of the micro-scale hydro-mechanical couplings between highly localized flows (fingering) and localized deformations of the skeleton (fracturing).
Modelling Polymer Deformation and Welding Behaviour during 3D Printing
McIlroy, Claire; Olmsted, Peter
2016-11-01
3D printing has the potential to transform manufacturing processes, yet improving the strength of printed parts, to equal that of traditionally-manufactured parts, remains an underlying issue. The most common method, fused deposition modelling, involves melting a thermoplastic, followed by layer-by-layer extrusion of the material to fabricate a three-dimensional object. The key to the ensuring strength at the weld between these layers is successful inter-diffusion. However, as the printed layer cools towards the glass transition temperature, the time available for diffusion is limited. In addition, the extrusion process significantly deforms the polymer micro-structure prior to welding and consequently affects how the polymers "re-entangle" across the weld. We have developed a simple model of the non-isothermal printing process to explore the effects that typical printing conditions and amorphous polymer rheology have on the ultimate weld structure. In particular, we incorporate both the stretch and orientation of the polymer using the Rolie-Poly constitutive equation to examine how the melt flows through the nozzle and is deposited onto the build plate. We then address how this deformation relaxes and contributes to the thickness and structure of the weld. National Institute for Standards and Technology (NIST) and Georgetown University.
Discrete element modelling of permanent pavement deformation in granular materials
Cai, Wei
2015-01-01
The permanent deformation of a pavement due to vehicle load is one of the important factors affecting the design life as well as the maintenance cost of a pavement. For the purpose of obtaining a cost-effective design, it is advisable to predict the traffic-loadinduced permanent pavement deformation. The permanent deformation in pavements (i.e. rutting) can be classified into three categories, including the wearing of the asphalt layers, compaction, and shear deformations. In the present stud...
Directory of Open Access Journals (Sweden)
Kevin D. Brewer
2012-11-01
Full Text Available This paper presents some Excel-based simulation exercises that are suitable for use in financial modeling courses. Such exercises are based on a stochastic process of stock price movements, called geometric Brownian motion, that underlies the derivation of the Black-Scholes option pricing model. Guidance is provided in assigning appropriate values of the drift parameter in the stochastic process for such exercises. Some further simulation exercises are also suggested. As the analytical underpinning of the materials involved is provided, this paper is expected to be of interest also to instructors and students of investment courses.
A 5G Hybrid Channel Model Considering Rays and Geometric Stochastic Propagation Graph
DEFF Research Database (Denmark)
Steinböck, Gerhard; Karstensen, Anders; Kyösti, Pekka;
2016-01-01
We consider a ray-tracing tool, in particular the METIS map based model for deterministic simulation of the channel impulse response. The ray-tracing tool is extended by adding a geometric stochastic propagation graph to model additional stochastic paths and the dense multipath components observed...... simplistic, e.g. plain walls and thus neglecting the structures on the building facades, window frames, window sills, etc. Thus in measurements there are often additional components observed that are not captured by these simplistic ray-tracing implementations. In this contribution we introduce a flexible...
Honzík, Petr; Podkovskiy, Alexey; Durand, Stéphane; Joly, Nicolas; Bruneau, Michel
2013-11-01
The main purpose of the paper is to contribute at presenting an analytical and a numerical modeling which would be relevant for interpreting the couplings between a circular membrane, a peripheral cavity having the same external radius as the membrane, and a thin air gap (with a geometrical discontinuity between them), and then to characterize small scale electrostatic receivers and to propose procedures that could be suitable for fitting adjustable parameters to achieve optimal behavior in terms of sensitivity and bandwidth expected. Therefore, comparison between these theoretical methods and characterization of several shapes is dealt with, which show that the models would be appropriate to address the design of such transducers.
Mixture models of geometric distributions in genomic analysis of inter-nucleotide distances
Directory of Open Access Journals (Sweden)
Adelaide Valente Freitas
2013-11-01
Full Text Available The mapping defined by inter-nucleotide distances (InD provides a reversible numerical representation of the primary structure of DNA. If nucleotides were independently placed along the genome, a finite mixture model of four geometric distributions could be fitted to the InD where the four marginal distributions would be the expected distributions of the four nucleotide types. We analyze a finite mixture model of geometric distributions (f_2, with marginals not explicitly addressed to the nucleotide types, as an approximation to the InD. We use BIC in the composite likelihood framework for choosing the number of components of the mixture and the EM algorithm for estimating the model parameters. Based on divergence profiles, an experimental study was carried out on the complete genomes of 45 species to evaluate f_2. Although the proposed model is not suited to the InD, our analysis shows that divergence profiles involving the empirical distribution of the InD are also exhibited by profiles involving f_2. It suggests that statistical regularities of the InD can be described by the model f_2. Some characteristics of the DNA sequences captured by the model f_2 are illustrated. In particular, clusterings of subgroups of eukaryotes (primates, mammalians, animals and plants are detected.
Variable-intercept panel model for deformation zoning of a super-high arch dam.
Shi, Zhongwen; Gu, Chongshi; Qin, Dong
2016-01-01
This study determines dam deformation similarity indexes based on an analysis of deformation zoning features and panel data clustering theory, with comprehensive consideration to the actual deformation law of super-high arch dams and the spatial-temporal features of dam deformation. Measurement methods of these indexes are studied. Based on the established deformation similarity criteria, the principle used to determine the number of dam deformation zones is constructed through entropy weight method. This study proposes the deformation zoning method for super-high arch dams and the implementation steps, analyzes the effect of special influencing factors of different dam zones on the deformation, introduces dummy variables that represent the special effect of dam deformation, and establishes a variable-intercept panel model for deformation zoning of super-high arch dams. Based on different patterns of the special effect in the variable-intercept panel model, two panel analysis models were established to monitor fixed and random effects of dam deformation. Hausman test method of model selection and model effectiveness assessment method are discussed. Finally, the effectiveness of established models is verified through a case study.
Mechanical modelling of the Singoe deformation zone. Site descriptive modelling Forsmark stage 2.1
Energy Technology Data Exchange (ETDEWEB)
Glamheden, Rune; Maersk Hansen, Lars; Fredriksson, Anders; Bergkvist, Lars; Markstroem, Ingemar; Elfstroem, Mats [Golder Associates AB (Sweden)
2007-02-15
This project aims at demonstrating the theoretical approach developed by SKB for determination of mechanical properties of large deformation zones, in particular the Singoe deformation zone. Up to now, only bedrock and minor deformation zones have been characterized by means of this methodology, which has been modified for this project. The Singoe deformation zone is taken as a reference object to get a more comprehensive picture of the structure, which could be incorporated in a future version of the SDM of Forsmark. Furthermore, the Singoe Zone has been chosen because of available data from four tunnels. Scope of work has included compilation and analysis of geological information from site investigations and documentation of existing tunnels. Results have been analyzed and demonstrated by means of RVS-visualization. Numerical modelling has been used to obtain mechanical properties. Numerical modelling has also been carried out in order to verify the results by comparison of calculated and measured deformations. Compilation of various structures in the four tunnels coincides largely with a magnetic anomaly and also with the estimated width. Based on the study it is clear that the Singoe deformation zone has a heterogeneous nature. The number of fracture zones associated with the deformation zone varies on either side of the zone, as does the transition zone between host rock and the Singoe zone. The overall impression from the study is that the results demonstrate that the methodology used for simulating of equivalent mechanical properties is an applicable and adequate method, also in case of large deformation zones. Typical rock mechanical parameters of the Singoe deformations that can be used in the regional stress model considering the zone to be a single fracture are: 200 MPa/m in normal stiffness, 10-15 MPa/m in shear stiffness, 0.4 MPa in cohesion and 31.5 degrees in friction angle.
The geometric signature: Quantifying landslide-terrain types from digital elevation models
Pike, R.J.
1988-01-01
Topography of various types and scales can be fingerprinted by computer analysis of altitude matrices (digital elevation models, or DEMs). The critical analytic tool is the geometric signature, a set of measures that describes topographic form well enough to distinguish among geomorphically disparate landscapes. Different surficial processes create topography with diagnostic forms that are recognizable in the field. The geometric signature abstracts those forms from contour maps or their DEMs and expresses them numerically. This multivariate characterization enables once-in-tractable problems to be addressed. The measures that constitute a geometric signature express different but complementary attributes of topographic form. Most parameters used here are statistical estimates of central tendency and dispersion for five major categories of terrain geometry; altitude, altitude variance spectrum, slope between slope reversals, and slope and its curvature at fixed slope lengths. As an experimental application of geometric signatures, two mapped terrain types associated with different processes of shallow landsliding in Marin County, California, were distinguished consistently by a 17-variable description of topography from 21??21 DEMs (30-m grid spacing). The small matrix is a statistical window that can be used to scan large DEMs by computer, thus potentially automating the mapping of contrasting terrain types. The two types in Marin County host either (1) slow slides: earth flows and slump-earth flows, or (2) rapid flows: debris avalanches and debris flows. The signature approach should adapt to terrain taxonomy and mapping in other areas, where conditions differ from those in Central California. ?? 1988 International Association for Mathematical Geology.
On the Modeling of Plastic Deformation of Magnesium Alloys
Ertürk, S.; Steglich, D.; Bohlen, J.; Letzig, D.; Brocks, W.
2007-05-01
Magnesium alloys are promising materials due to their low density and therefore high specific strength. However, the industrial application is not well established so far, especially for wrought products such as sheets or profiles. Due to its hexagonal crystallographic structure, deformation mechanisms observed in magnesium alloys are rather different from those in face centered cubic metals such as aluminum alloys. This leads not only to a mechanical anisotropy, but also to a tension-compression asymmetry, i.e. unequal compressive and tensile yield strength. The resulting complexity in the yielding behavior of such materials cannot be captured by conventional models of J2 plasticity. Cazacu and Barlat, therefore, proposed a phenomenological yield potential which accounts for the respective phenomena by introducing the third invariant of the stress tensor. Simulations based on this model are performed with ABAQUS/Explicit and a user defined routine VUMAT for validating the respective implementation. The application aims at simulating the extrusion process of magnesium alloys.
Modeling cellular deformations using the level set formalism
Directory of Open Access Journals (Sweden)
Yang Liu
2008-07-01
Full Text Available Abstract Background Many cellular processes involve substantial shape changes. Traditional simulations of these cell shape changes require that grids and boundaries be moved as the cell's shape evolves. Here we demonstrate that accurate cell shape changes can be recreated using level set methods (LSM, in which the cellular shape is defined implicitly, thereby eschewing the need for updating boundaries. Results We obtain a viscoelastic model of Dictyostelium cells using micropipette aspiration and show how this viscoelastic model can be incorporated into LSM simulations to recreate the observed protrusion of cells into the micropipette faithfully. We also demonstrate the use of our techniques by simulating the cell shape changes elicited by the chemotactic response to an external chemoattractant gradient. Conclusion Our results provide a simple but effective means of incorporating cellular deformations into mathematical simulations of cell signaling. Such methods will be useful for simulating important cellular events such as chemotaxis and cytokinesis.
Hypersurface-deformation algebroids and effective space-time models
Bojowald, Martin; Buyukcam, Umut; D'Ambrosio, Fabio
2016-01-01
In canonical gravity, covariance is implemented by brackets of hypersurface-deformation generators forming a Lie algebroid. Lie algebroid morphisms therefore allow one to relate different versions of the brackets that correspond to the same space-time structure. An application to examples of modified brackets found mainly in models of loop quantum gravity can in some cases map the space-time structure back to the classical Riemannian form after a field redefinition. For one type of quantum corrections (holonomies), signature change appears to be a generic feature of effective space-time, and is shown here to be a new quantum space-time phenomenon which cannot be mapped to an equivalent classical structure. In low-curvature regimes, our constructions prove the existence of classical space-time structures assumed elsewhere in models of loop quantum cosmology, but also shows the existence of additional quantum corrections that have not always been included.
Institute of Scientific and Technical Information of China (English)
SHU Linsen; CAO Huajun; LI Xianchong; ZHANG Chenglong; LI Yuxia
2015-01-01
The current researches on the tooth surface mathematical equations and the theory of gearing malnly pay attention to the ordinary type worm gear set (e.g., ZN, ZA, or ZK). The research of forming mechanism and three-dimensional modeling method for the double pitch worm gear set is not enough. So there are some difficulties in mathematical model deducing and geometry modeling of double pitch ZN-type worm gear set based on generation mechanism. In order to establish the mathematical model and the precise geometric model of double pitch ZN-type worm gear set, the structural characteristics and generation mechanism of the double pitch ZN-type worm gear set are investigated. Mathematical model of the ZN-type worm gear set is derived based on its generation mechanism and the theory of gearing. According to the mathematical model of the worm gear set which has been developed, a geometry modeling method of the double pitch ZN-type worm and worm gear is presented. Furthermore, a geometrical precision calculate method is proposed to evaluate the geometrical quality of the double pitch worm gear set. As a result, the maximum error is less than 6´10–4 mm in magnitude, thus the model of the double pitch ZN-type worm gear set is avallable to meet the requirements of finite element analysis and engineering application. The derived mathematical model and the proposed geometrical modeling method are helpful to guiding the design, manufacture and contact analysis of the worm gear set.
The Simulation and Correction to the Brain Deformation Based on the Linear Elastic Model in IGS
Institute of Scientific and Technical Information of China (English)
MUXiao-lan; SONGZhi-jian
2004-01-01
The brain deformation is a vital factor affecting the precision of the IGS and it becomes a hotspot to simulate and correct the brain deformation recently.The research organizations, which firstly resolved the brain deformation with the physical models, have the Image Processing and Analysis department of Yale University, Biomedical Modeling Lab of Vanderbilt University and so on. The former uses the linear elastic model; the latter uses the consolidation model.
The Transmuted Geometric-Weibull distribution: Properties, Characterizations and Regression Models
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Zohdy M Nofal
2017-06-01
Full Text Available We propose a new lifetime model called the transmuted geometric-Weibull distribution. Some of its structural properties including ordinary and incomplete moments, quantile and generating functions, probability weighted moments, Rényi and q-entropies and order statistics are derived. The maximum likelihood method is discussed to estimate the model parameters by means of Monte Carlo simulation study. A new location-scale regression model is introduced based on the proposed distribution. The new distribution is applied to two real data sets to illustrate its flexibility. Empirical results indicate that proposed distribution can be alternative model to other lifetime models available in the literature for modeling real data in many areas.
Directory of Open Access Journals (Sweden)
Martin Boeff
2014-01-01
Full Text Available The plastic deformations of tempered martensite steel representative volume elements with different martensite block structures have been investigated by using a nonlocal crystal plasticity model which considers isotropic and kinematic hardening produced by plastic strain gradients. It was found that pronounced strain gradients occur in the grain boundary region even under homogeneous loading. The isotropic hardening of strain gradients strongly influences the global stress–strain diagram while the kinematic hardening of strain gradients influences the local deformation behaviour. It is found that the additional strain gradient hardening is not only dependent on the block width but also on the misorientations or the deformation incompatibilities in adjacent blocks.
Sheynikhovich, Denis; Arleo, Angelo
2010-12-13
In contrast to predictions derived from the associative learning theory, a number of behavioral studies suggested the absence of competition between geometric cues and landmarks in some experimental paradigms. In parallel to these studies, neurobiological experiments suggested the existence of separate independent memory systems which may not always interact according to classic associative principles. In this paper we attempt to combine these two lines of research by proposing a model of spatial learning that is based on the theory of multiple memory systems. In our model, a place-based locale strategy uses activities of modeled hippocampal place cells to drive navigation to a hidden goal, while a stimulus-response taxon strategy, presumably mediated by the dorso-lateral striatum, learns landmark-approaching behavior. A strategy selection network, proposed to reside in the prefrontal cortex, implements a simple reinforcement learning rule to switch behavioral strategies. The model is used to reproduce the results of a behavioral experiment in which an interaction between a landmark and geometric cues was studied. We show that this model, built on the basis of neurobiological data, can explain the lack of competition between the landmark and geometry, potentiation of geometry learning by the landmark, and blocking. Namely, we propose that the geometry potentiation is a consequence of cooperation between memory systems during learning, while blocking is due to competition between the memory systems during action selection.
Liu, Jun Jie; Dolev, Maya Bar; Celik, Yeliz; Wettlaufer, J S; Braslavsky, Ido
2012-01-01
The melting of pure axisymmetric ice crystals has been described previously by us within the framework of so-called geometric crystal growth. Nonequilibrium ice crystal shapes evolving in the presence of hyperactive antifreeze proteins (hypAFPs) are experimentally observed to assume ellipsoidal geometries ("lemon" or "rice" shapes). To analyze such shapes we harness the underlying symmetry of hexagonal ice Ih and extend two-dimensional geometric models to three-dimensions to reproduce the experimental dissolution process. The geometrical model developed will be useful as a quantitative test of the mechanisms of interaction between hypAFPs and ice.
Kulasinski, Karol; Guyer, Robert; Derome, Dominique; Carmeliet, Jan
2015-08-01
Molecular simulation of adsorption of water molecules in nanoporous amorphous biopolymers, e.g., cellulose, reveals nonlinear swelling and nonlinear mechanical response with the increase in fluid content. These nonlinearities result from hydrogen bond breakage by water molecules. Classical poroelastic models, employing porosity and pore pressure as basic variables for describing the "pore fluid," are not adequate for the description of these systems. There is neither a static geometric structure to which porosity can sensibly be assigned nor arrangements of water molecules that are adequately described by giving them a pressure. We employ molar concentration of water and chemical potential to describe the state of the "pore fluid" and stress-strain as mechanical variables. A thermodynamic description is developed using a model energy function having mechanical, fluid, and fluid-mechanical coupling contributions. The parameters in this model energy are fixed by the output of the initial simulation and validated with the results of further simulation. The poroelastic properties, e.g., swelling and mechanical response, are found to be functions both of the molar concentration of water and the stress. The basic fluid-mechanical coupling coefficient, the swelling coefficient, depends on the molar concentration of water and stress and is interpreted in terms of porosity change and solid matrix deformation. The difference between drained and undrained bulk stiffness is explained as is the dependence of these moduli on concentration and stress.
A point cloud modeling method based on geometric constraints mixing the robust least squares method
Yue, JIanping; Pan, Yi; Yue, Shun; Liu, Dapeng; Liu, Bin; Huang, Nan
2016-10-01
The appearance of 3D laser scanning technology has provided a new method for the acquisition of spatial 3D information. It has been widely used in the field of Surveying and Mapping Engineering with the characteristics of automatic and high precision. 3D laser scanning data processing process mainly includes the external laser data acquisition, the internal industry laser data splicing, the late 3D modeling and data integration system. For the point cloud modeling, domestic and foreign researchers have done a lot of research. Surface reconstruction technology mainly include the point shape, the triangle model, the triangle Bezier surface model, the rectangular surface model and so on, and the neural network and the Alfa shape are also used in the curved surface reconstruction. But in these methods, it is often focused on single surface fitting, automatic or manual block fitting, which ignores the model's integrity. It leads to a serious problems in the model after stitching, that is, the surfaces fitting separately is often not satisfied with the well-known geometric constraints, such as parallel, vertical, a fixed angle, or a fixed distance. However, the research on the special modeling theory such as the dimension constraint and the position constraint is not used widely. One of the traditional modeling methods adding geometric constraints is a method combing the penalty function method and the Levenberg-Marquardt algorithm (L-M algorithm), whose stability is pretty good. But in the research process, it is found that the method is greatly influenced by the initial value. In this paper, we propose an improved method of point cloud model taking into account the geometric constraint. We first apply robust least-squares to enhance the initial value's accuracy, and then use penalty function method to transform constrained optimization problems into unconstrained optimization problems, and finally solve the problems using the L-M algorithm. The experimental results
Segmentation of Pathological Structures by Landmark-Assisted Deformable Models.
Ibragimov, Bulat; Korez, Robert; Likar, Bostjan; Pernus, Franjo; Xing, Lei; Vrtovec, Tomaz
2017-02-13
Computerized segmentation of pathological structures in medical images is challenging, as, in addition to unclear image boundaries, image artifacts and traces of surgical activities, the shape of pathological structures may be very different from the shape of normal structures. Even if a sufficient number of pathological training samples are collected, statistical shape modeling cannot always capture shape features of pathological samples as they may be suppressed by shape features of a considerably larger number of healthy samples. At the same time, landmarking can be efficient in analyzing pathological structures but often lacks robustness. In this paper, we combine the advantages of landmark detection and deformable models into a novel supervised multi-energy segmentation framework that can efficiently segment structures with pathological shape. The framework adopts the theory of Laplacian shape editing that was introduced in the field of computer graphics, so that the limitations of statistical shape modeling are avoided. The performance of the proposed framework was validated by segmenting fractured lumbar vertebrae from three-dimensional (3D) computed tomography (CT) images, atrophic corpora callosa from two-dimensional (2D) magnetic resonance (MR) crosssections and cancerous prostates from 3D MR images, resulting respectively in a Dice coefficient of 84.7 ± 5.0%, 85.3 ± 4.8% and 78.3 ± 5.1%, and boundary distance of 1.14 ± 0.49 mm, 1.42 ± 0.45mm and 2.27 ± 0.52 mm. The obtained results were shown to be superior in comparison to existing deformable modelbased segmentation algorithms.
Morphing of geometric composites via residual swelling.
Pezzulla, Matteo; Shillig, Steven A; Nardinocchi, Paola; Holmes, Douglas P
2015-08-07
Understanding and controlling the shape of thin, soft objects has been the focus of significant research efforts among physicists, biologists, and engineers in the last decade. These studies aim to utilize advanced materials in novel, adaptive ways such as fabricating smart actuators or mimicking living tissues. Here, we present the controlled growth-like morphing of 2D sheets into 3D shapes by preparing geometric composite structures that deform by residual swelling. The morphing of these geometric composites is dictated by both swelling and geometry, with diffusion controlling the swelling-induced actuation, and geometric confinement dictating the structure's deformed shape. Building on a simple mechanical analog, we present an analytical model that quantitatively describes how the Gaussian and mean curvatures of a thin disk are affected by the interplay among geometry, mechanics, and swelling. This model is in excellent agreement with our experiments and numerics. We show that the dynamics of residual swelling is dictated by a competition between two characteristic diffusive length scales governed by geometry. Our results provide the first 2D analog of Timoshenko's classical formula for the thermal bending of bimetallic beams - our generalization explains how the Gaussian curvature of a 2D geometric composite is affected by geometry and elasticity. The understanding conferred by these results suggests that the controlled shaping of geometric composites may provide a simple complement to traditional manufacturing techniques.
Optimising and extending the geometrical modeller of a physics simulation framework
Urban, P
1998-01-01
The design of highly complex particle detectors used in High Energy Physics involves both CAD systems and physics simulation packages like Geant4. Geant4 is able to exchange detector geometries with CAD systems, conforming to the Standard for the Exchange of Product Model Data (STEP); Boundary Representation (B-Rep) models are transferred. Particle tracking is performed in these models, requiring efficient and accurate intersection computations from the geometrical modeller. The results of extending and optimising the modeller of Geant4 form the contents of this thesis. Swept surfaces: surfaces of linear extrusion and surfaces of revolution have been implemented. The problem of classifying points on surfaces bounded by curves as being inside or outside has been solved. These tasks necessitated the extension and optimisation of code related to curves and lead to a re-design of this code. Emphasis was put on efficiency and on dealing with numerical errors. The results will be integrated into the upcoming beta t...
Geometrical Lattice models for N=2 supersymmetric theories in two dimensions
Saleur, H
1992-01-01
We introduce in this paper two dimensional lattice models whose continuum limit belongs to the $N=2$ series. The first kind of model is integrable and obtained through a geometrical reformulation, generalizing results known in the $k=1$ case, of the $\\Gamma_{k}$ vertex models (based on the quantum algebra $U_{q}sl(2)$ and representation of spin $j=k/2$). We demonstrate in particular that at the $N=2$ point, the free energy of the $\\Gamma_{k}$ vertex model can be obtained exactly by counting arguments, without any Bethe ansatz computation, and we exhibit lattice operators that reproduce the chiral ring. The second class of models is more adequately described in the language of twisted $N=2$ supersymmetry, and consists of an infinite series of multicritical polymer points, which should lead to experimental realizations. It turns out that the exponents $\
A geometric approach to modeling of four- and five-link planar snake-like robot
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Tomáš Lipták
2016-10-01
Full Text Available The article deals with the issue of use of geometric mechanics tools in modelling nonholonomic systems. The introductory part of the article contains fiber bundle theory that we use at creating mathematical model of nonholonomic locomotion system with undulatory movement. Further the determination of general mathematical model for n-link snake-like robot is presented, where we used nonholonomic constraints. The relation between changes of shape and position variables was expressed using the local connection that was used to analyze and control system movement by vector fields. The effect of links number of snake-like robot on its mathematical model was investigated. The last part of this article consists of detailed description of modeling reconstruction equation for four- and five-link snake-like robot.
Physics-based deformable organisms for medical image analysis
Hamarneh, Ghassan; McIntosh, Chris
2005-04-01
Previously, "Deformable organisms" were introduced as a novel paradigm for medical image analysis that uses artificial life modelling concepts. Deformable organisms were designed to complement the classical bottom-up deformable models methodologies (geometrical and physical layers), with top-down intelligent deformation control mechanisms (behavioral and cognitive layers). However, a true physical layer was absent and in order to complete medical image segmentation tasks, deformable organisms relied on pure geometry-based shape deformations guided by sensory data, prior structural knowledge, and expert-generated schedules of behaviors. In this paper we introduce the use of physics-based shape deformations within the deformable organisms framework yielding additional robustness by allowing intuitive real-time user guidance and interaction when necessary. We present the results of applying our physics-based deformable organisms, with an underlying dynamic spring-mass mesh model, to segmenting and labelling the corpus callosum in 2D midsagittal magnetic resonance images.
Efficiencies of power plants, quasi-static models and the geometric-mean temperature
Johal, Ramandeep S.
2017-02-01
Observed efficiencies of industrial power plants are often approximated by the square-root formula: 1 - √T-/T+, where T+(T-) is the highest (lowest) temperature achieved in the plant. This expression can be derived within finite-time thermodynamics, or, by entropy generation minimization, based on finite rates for the processes. In these analyses, a closely related quantity is the optimal value of the intermediate temperature for the hot stream, given by the geometric-mean value: √T+/T-. In this paper, instead of finite-time models, we propose to model the operation of plants by quasi-static work extraction models, with one reservoir (source/sink) as finite, while the other as practically infinite. No simplifying assumption is made on the nature of the finite system. This description is consistent with two model hypotheses, each yielding a specific value of the intermediate temperature, say T1 and T2. The lack of additional information on validity of the hypothesis that may be actually realized, motivates to approach the problem as an exercise in inductive inference. Thus we define an expected value of the intermediate temperature as the equally weighted mean: (T1 + T2)/2. It is shown that the expected value is very closely given by the geometric-mean value for almost all of the observed power plants.
Geometric Context and Orientation Map Combination for Indoor Corridor Modeling Using a Single Image
Baligh Jahromi, Ali; Sohn, Gunho
2016-06-01
Since people spend most of their time indoors, their indoor activities and related issues in health, security and energy consumption have to be understood. Hence, gathering and representing spatial information of indoor spaces in form of 3D models become very important. Considering the available data gathering techniques with respect to the sensors cost and data processing time, single images proved to be one of the reliable sources. Many of the current single image based indoor space modeling methods are defining the scene as a single box primitive. This domain-specific knowledge is usually not applicable in various cases where multiple corridors are joined at one scene. Here, we addressed this issue by hypothesizing-verifying multiple box primitives which represents the indoor corridor layout. Middle-level perceptual organization is the foundation of the proposed method, which relies on finding corridor layout boundaries using both detected line segments and virtual rays created by orthogonal vanishing points. Due to the presence of objects, shadows and occlusions, a comprehensive interpretation of the edge relations is often concealed. This necessitates the utilization of virtual rays to create a physically valid layout hypothesis. Many of the former methods used Orientation Map or Geometric Context to evaluate their proposed layout hypotheses. Orientation map is a map that reveals the local belief of region orientations computed from line segments, and in a segmented image geometric context uses color, texture, edge, and vanishing point cues to estimate the likelihood of each possible label for all super-pixels. Here, the created layout hypotheses are evaluated by an objective function which considers the fusion of orientation map and geometric context with respect to the horizontal viewing angle at each image pixel. Finally, the best indoor corridor layout hypothesis which gets the highest score from the scoring function will be selected and converted to a 3D
Geometrical order-of-magnitude estimates for spatial curvature in realistic models of the Universe
Buchert, Thomas; van Elst, Henk; 10.1007/s10714-009-0828-4
2009-01-01
The thoughts expressed in this article are based on remarks made by J\\"urgen Ehlers at the Albert-Einstein-Institut, Golm, Germany in July 2007. The main objective of this article is to demonstrate, in terms of plausible order-of-magnitude estimates for geometrical scalars, the relevance of spatial curvature in realistic models of the Universe that describe the dynamics of structure formation since the epoch of matter-radiation decoupling. We introduce these estimates with a commentary on the use of a quasi-Newtonian metric form in this context.
Montag, J. Lee; Family, Fereydoon; Vicsek, Tamas; Nakanishi, Hisao
1985-10-01
We propose a new phenomenological rule for the weight function in the position-space renormalization-group approach for the calculation of the fractal dimension in models of geometrical disorder in order to avoid strong corrections to scaling due to surface effects. In our scheme the radius of gyration is used as a characteristic measure of the spatial extent of the clusters. In addition, an optimization parameter is introduced. Application to diffusion-limited aggregation in two dimensions shows that our method gives good estimates even when relatively small cells are used.
Matching Aerial Images to 3D Building Models Using Context-Based Geometric Hashing.
Jung, Jaewook; Sohn, Gunho; Bang, Kiin; Wichmann, Andreas; Armenakis, Costas; Kada, Martin
2016-06-22
A city is a dynamic entity, which environment is continuously changing over time. Accordingly, its virtual city models also need to be regularly updated to support accurate model-based decisions for various applications, including urban planning, emergency response and autonomous navigation. A concept of continuous city modeling is to progressively reconstruct city models by accommodating their changes recognized in spatio-temporal domain, while preserving unchanged structures. A first critical step for continuous city modeling is to coherently register remotely sensed data taken at different epochs with existing building models. This paper presents a new model-to-image registration method using a context-based geometric hashing (CGH) method to align a single image with existing 3D building models. This model-to-image registration process consists of three steps: (1) feature extraction; (2) similarity measure; and matching, and (3) estimating exterior orientation parameters (EOPs) of a single image. For feature extraction, we propose two types of matching cues: edged corner features representing the saliency of building corner points with associated edges, and contextual relations among the edged corner features within an individual roof. A set of matched corners are found with given proximity measure through geometric hashing, and optimal matches are then finally determined by maximizing the matching cost encoding contextual similarity between matching candidates. Final matched corners are used for adjusting EOPs of the single airborne image by the least square method based on collinearity equations. The result shows that acceptable accuracy of EOPs of a single image can be achievable using the proposed registration approach as an alternative to a labor-intensive manual registration process.
Matching Aerial Images to 3D Building Models Using Context-Based Geometric Hashing
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Jaewook Jung
2016-06-01
Full Text Available A city is a dynamic entity, which environment is continuously changing over time. Accordingly, its virtual city models also need to be regularly updated to support accurate model-based decisions for various applications, including urban planning, emergency response and autonomous navigation. A concept of continuous city modeling is to progressively reconstruct city models by accommodating their changes recognized in spatio-temporal domain, while preserving unchanged structures. A first critical step for continuous city modeling is to coherently register remotely sensed data taken at different epochs with existing building models. This paper presents a new model-to-image registration method using a context-based geometric hashing (CGH method to align a single image with existing 3D building models. This model-to-image registration process consists of three steps: (1 feature extraction; (2 similarity measure; and matching, and (3 estimating exterior orientation parameters (EOPs of a single image. For feature extraction, we propose two types of matching cues: edged corner features representing the saliency of building corner points with associated edges, and contextual relations among the edged corner features within an individual roof. A set of matched corners are found with given proximity measure through geometric hashing, and optimal matches are then finally determined by maximizing the matching cost encoding contextual similarity between matching candidates. Final matched corners are used for adjusting EOPs of the single airborne image by the least square method based on collinearity equations. The result shows that acceptable accuracy of EOPs of a single image can be achievable using the proposed registration approach as an alternative to a labor-intensive manual registration process.
HERMES: A Model to Describe Deformation, Burning, Explosion, and Detonation
Energy Technology Data Exchange (ETDEWEB)
Reaugh, J E
2011-11-22
performance, whether as a result of accident, hazard, or a fault in the detonation train. These models describe the build-up of detonation from a shock stimulus. They are generally consistent with the mesoscale picture of ignition at many small defects in the plane of the shock front and the growth of the resulting hot-spots, leading to detonation in heterogeneous explosives such as plastic-bonded explosives (PBX). The models included terms for ignition, and also for the growth of reaction as tracked by the local mass fraction of product gas, {lambda}. The growth of reaction in such models incorporates a form factor that describes the change of surface area per unit volume (specific surface area) as the reaction progresses. For unimolecular crystalline-based explosives, the form factor is consistent with the mesoscale picture of a galaxy of hot spots burning outward and eventually interacting with each other. For composite explosives and propellants, where the fuel and oxidizer are segregated, the diffusion flame at the fuel-oxidizer interface can be interpreted with a different form factor that corresponds to grains burning inward from their surfaces. The form factor influences the energy release rate, and the amount of energy released in the reaction zone. Since the 19th century, gun and cannon propellants have used perforated geometric shapes that produce an increasing surface area as the propellant burns. This helps maintain the pressure as burning continues while the projectile travels down the barrel, which thereby increases the volume of the hot gas. Interior ballistics calculations use a geometric form factor to describe the changing surface area precisely. As a result, with a suitably modified form factor, detonation models can represent burning and explosion in damaged and broken reactant. The disadvantage of such models in application to accidents is that the ignition term does not distinguish between a value of pressure that results from a shock, and the same
HERMES: A Model to Describe Deformation, Burning, Explosion, and Detonation
Energy Technology Data Exchange (ETDEWEB)
Reaugh, J E
2011-11-22
performance, whether as a result of accident, hazard, or a fault in the detonation train. These models describe the build-up of detonation from a shock stimulus. They are generally consistent with the mesoscale picture of ignition at many small defects in the plane of the shock front and the growth of the resulting hot-spots, leading to detonation in heterogeneous explosives such as plastic-bonded explosives (PBX). The models included terms for ignition, and also for the growth of reaction as tracked by the local mass fraction of product gas, {lambda}. The growth of reaction in such models incorporates a form factor that describes the change of surface area per unit volume (specific surface area) as the reaction progresses. For unimolecular crystalline-based explosives, the form factor is consistent with the mesoscale picture of a galaxy of hot spots burning outward and eventually interacting with each other. For composite explosives and propellants, where the fuel and oxidizer are segregated, the diffusion flame at the fuel-oxidizer interface can be interpreted with a different form factor that corresponds to grains burning inward from their surfaces. The form factor influences the energy release rate, and the amount of energy released in the reaction zone. Since the 19th century, gun and cannon propellants have used perforated geometric shapes that produce an increasing surface area as the propellant burns. This helps maintain the pressure as burning continues while the projectile travels down the barrel, which thereby increases the volume of the hot gas. Interior ballistics calculations use a geometric form factor to describe the changing surface area precisely. As a result, with a suitably modified form factor, detonation models can represent burning and explosion in damaged and broken reactant. The disadvantage of such models in application to accidents is that the ignition term does not distinguish between a value of pressure that results from a shock, and the same
Hilley, G. E.; Arrowsmith, R.
2011-12-01
cases in which the SAF fault friction is low, and the contrast in frictional properties between the simulated North American and Pacific Plate sediments is high. In these cases, the overall dimensions and rock uplift rates predicted by the simulations are, to first order, consistent with values measured or inferred based on field observations. Our results provide a mechanically plausible scenario to supplement the geometric explanation previously posed for this specific feature, and indicate that this type of numerical modeling may provide a useful basis for forming a mechanistic understanding these near-fault deformation features.
Rahmouni, A.; Beidouri, Z.; Benamar, R.
2013-09-01
The purpose of the present paper was the development of a physically discrete model for geometrically nonlinear free transverse constrained vibrations of beams, which may replace, if sufficient degrees of freedom are used, the previously developed continuous nonlinear beam constrained vibration models. The discrete model proposed is an N-Degrees of Freedom (N-dof) system made of N masses placed at the ends of solid bars connected by torsional springs, presenting the beam flexural rigidity. The large transverse displacements of the bar ends induce a variation in their lengths giving rise to axial forces modelled by longitudinal springs. The calculations made allowed application of the semi-analytical model developed previously for nonlinear structural vibration involving three tensors, namely the mass tensor mij, the linear rigidity tensor kij and the nonlinearity tensor bijkl. By application of Hamilton's principle and spectral analysis, the nonlinear vibration problem is reduced to a nonlinear algebraic system, examined for increasing numbers of dof. The results obtained by the physically discrete model showed a good agreement and a quick convergence to the equivalent continuous beam model, for various fixed boundary conditions, for both the linear frequencies and the nonlinear backbone curves, and also for the corresponding mode shapes. The model, validated here for the simply supported and clamped ends, may be used in further works to present the flexural linear and nonlinear constrained vibrations of beams with various types of discontinuities in the mass or in the elasticity distributions. The development of an adequate discrete model including the effect of the axial strains induced by large displacement amplitudes, which is predominant in geometrically nonlinear transverse constrained vibrations of beams [1]. The investigation of the results such a discrete model may lead to in the case of nonlinear free vibrations. The development of the analogy between the
A Geometric Method for Model Reduction of Biochemical Networks with Polynomial Rate Functions.
Samal, Satya Swarup; Grigoriev, Dima; Fröhlich, Holger; Weber, Andreas; Radulescu, Ovidiu
2015-12-01
Model reduction of biochemical networks relies on the knowledge of slow and fast variables. We provide a geometric method, based on the Newton polytope, to identify slow variables of a biochemical network with polynomial rate functions. The gist of the method is the notion of tropical equilibration that provides approximate descriptions of slow invariant manifolds. Compared to extant numerical algorithms such as the intrinsic low-dimensional manifold method, our approach is symbolic and utilizes orders of magnitude instead of precise values of the model parameters. Application of this method to a large collection of biochemical network models supports the idea that the number of dynamical variables in minimal models of cell physiology can be small, in spite of the large number of molecular regulatory actors.
A Simplified Geometric Channel Model for Mobile-to-Mobile Communications
Directory of Open Access Journals (Sweden)
K. B. Baltzis
2011-12-01
Full Text Available In Mobile-to-Mobile (M2M communications, the communicating nodes are surrounded by scatterers and equipped with low elevation antennas. This paper proposes a simple 2-D geometric scattering model for M2M channels. The model is also applicable in cellular systems when we employ low height base station antennas. In our approach, the scatterers are uniformly distributed in ellipses with arbitrary size and orientation around each communicating node. We provide simple formulas for the calculation of the angular spread and delay variation of the propagating signal. Simulation results verify the accuracy of the model. In order to validate the generalization of the approach, we compare it against notable models in the literature. As an application example, we investigate the impact of scatterer distribution and separation between mobiles on the angle and time of arrival statistics of the multipaths.
A simple geometrical model describing shapes of soap films suspended on two rings
Herrmann, Felix J.; Kilvington, Charles D.; Wildenberg, Rebekah L.; Camacho, Franco E.; Walecki, Wojciech J.; Walecki, Peter S.; Walecki, Eve S.
2016-09-01
We measured and analysed the stability of two types of soap films suspended on two rings using the simple conical frusta-based model, where we use common definition of conical frustum as a portion of a cone that lies between two parallel planes cutting it. Using frusta-based we reproduced very well-known results for catenoid surfaces with and without a central disk. We present for the first time a simple conical frusta based spreadsheet model of the soap surface. This very simple, elementary, geometrical model produces results surprisingly well matching the experimental data and known exact analytical solutions. The experiment and the spreadsheet model can be used as a powerful teaching tool for pre-calculus and geometry students.
Directory of Open Access Journals (Sweden)
Shengxiang Jia
2003-01-01
Full Text Available This article presents a dynamic model of three shafts and two pair of gears in mesh, with 26 degrees of freedom, including the effects of variable tooth stiffness, pitch and profile errors, friction, and a localized tooth crack on one of the gears. The article also details howgeometrical errors in teeth can be included in a model. The model incorporates the effects of variations in torsional mesh stiffness in gear teeth by using a common formula to describe stiffness that occurs as the gears mesh together. The comparison between the presence and absence of geometrical errors in teeth was made by using Matlab and Simulink models, which were developed from the equations of motion. The effects of pitch and profile errors on the resultant input pinion angular velocity coherent-signal of the input pinion's average are discussed by investigating some of the common diagnostic functions and changes to the frequency spectra results.
Bennequin, Daniel
2016-01-01
We propose a geometric explanation of the standard model of Glashow, Weinberg and Salam for the known elementary particles. Our model is a generic Quantum Field Theory in dimension four, obtained by developing along a Lorentz sub-manifold the lagrangian of Einstein and Dirac in dimension twelve. The main mechanism which gives birth to the standard model is a certain gauge fixing of triality, which permits to identify the multiplicity of fermions, as seen from the four dimensional world, with the eight unseen dimensions of the generating universe. In this way we get the known tables of particles, explaining the series of fermions and the gauge bosons. We suggest that the Higgs field dynamics could appear through a bosonization of the right handed neutrino and correspond to a displacement in the unseen dimensions. We also propose hypotheses for dark matter, and perhaps dark energy. Then we suggest predictions to go beyond the standard model.
MATCHING AERIAL IMAGES TO 3D BUILDING MODELS BASED ON CONTEXT-BASED GEOMETRIC HASHING
Directory of Open Access Journals (Sweden)
J. Jung
2016-06-01
Full Text Available In this paper, a new model-to-image framework to automatically align a single airborne image with existing 3D building models using geometric hashing is proposed. As a prerequisite process for various applications such as data fusion, object tracking, change detection and texture mapping, the proposed registration method is used for determining accurate exterior orientation parameters (EOPs of a single image. This model-to-image matching process consists of three steps: 1 feature extraction, 2 similarity measure and matching, and 3 adjustment of EOPs of a single image. For feature extraction, we proposed two types of matching cues, edged corner points representing the saliency of building corner points with associated edges and contextual relations among the edged corner points within an individual roof. These matching features are extracted from both 3D building and a single airborne image. A set of matched corners are found with given proximity measure through geometric hashing and optimal matches are then finally determined by maximizing the matching cost encoding contextual similarity between matching candidates. Final matched corners are used for adjusting EOPs of the single airborne image by the least square method based on co-linearity equations. The result shows that acceptable accuracy of single image's EOP can be achievable by the proposed registration approach as an alternative to labour-intensive manual registration process.
Bucksch, Alexander; Atta-Boateng, Acheampong; Azihou, Akomian F.; Battogtokh, Dorjsuren; Baumgartner, Aly; Binder, Brad M.; Braybrook, Siobhan A.; Chang, Cynthia; Coneva, Viktoirya; DeWitt, Thomas J.; Fletcher, Alexander G.; Gehan, Malia A.; Diaz-Martinez, Diego Hernan; Hong, Lilan; Iyer-Pascuzzi, Anjali S.; Klein, Laura L.; Leiboff, Samuel; Li, Mao; Lynch, Jonathan P.; Maizel, Alexis; Maloof, Julin N.; Markelz, R. J. Cody; Martinez, Ciera C.; Miller, Laura A.; Mio, Washington; Palubicki, Wojtek; Poorter, Hendrik; Pradal, Christophe; Price, Charles A.; Puttonen, Eetu; Reese, John B.; Rellán-Álvarez, Rubén; Spalding, Edgar P.; Sparks, Erin E.; Topp, Christopher N.; Williams, Joseph H.; Chitwood, Daniel H.
2017-01-01
The geometries and topologies of leaves, flowers, roots, shoots, and their arrangements have fascinated plant biologists and mathematicians alike. As such, plant morphology is inherently mathematical in that it describes plant form and architecture with geometrical and topological techniques. Gaining an understanding of how to modify plant morphology, through molecular biology and breeding, aided by a mathematical perspective, is critical to improving agriculture, and the monitoring of ecosystems is vital to modeling a future with fewer natural resources. In this white paper, we begin with an overview in quantifying the form of plants and mathematical models of patterning in plants. We then explore the fundamental challenges that remain unanswered concerning plant morphology, from the barriers preventing the prediction of phenotype from genotype to modeling the movement of leaves in air streams. We end with a discussion concerning the education of plant morphology synthesizing biological and mathematical approaches and ways to facilitate research advances through outreach, cross-disciplinary training, and open science. Unleashing the potential of geometric and topological approaches in the plant sciences promises to transform our understanding of both plants and mathematics. PMID:28659934
Matching Aerial Images to 3d Building Models Based on Context-Based Geometric Hashing
Jung, J.; Bang, K.; Sohn, G.; Armenakis, C.
2016-06-01
In this paper, a new model-to-image framework to automatically align a single airborne image with existing 3D building models using geometric hashing is proposed. As a prerequisite process for various applications such as data fusion, object tracking, change detection and texture mapping, the proposed registration method is used for determining accurate exterior orientation parameters (EOPs) of a single image. This model-to-image matching process consists of three steps: 1) feature extraction, 2) similarity measure and matching, and 3) adjustment of EOPs of a single image. For feature extraction, we proposed two types of matching cues, edged corner points representing the saliency of building corner points with associated edges and contextual relations among the edged corner points within an individual roof. These matching features are extracted from both 3D building and a single airborne image. A set of matched corners are found with given proximity measure through geometric hashing and optimal matches are then finally determined by maximizing the matching cost encoding contextual similarity between matching candidates. Final matched corners are used for adjusting EOPs of the single airborne image by the least square method based on co-linearity equations. The result shows that acceptable accuracy of single image's EOP can be achievable by the proposed registration approach as an alternative to labour-intensive manual registration process.
Directory of Open Access Journals (Sweden)
Pooyan Vahidi Pashsaki
2016-06-01
Full Text Available Accuracy of a five-axis CNC machine tool is affected by a vast number of error sources. This paper investigates volumetric error modeling and its compensation to the basis for creation of new tool path for improvement of work pieces accuracy. The volumetric error model of a five-axis machine tool with the configuration RTTTR (tilting head B-axis and rotary table in work piece side A΄ was set up taking into consideration rigid body kinematics and homogeneous transformation matrix, in which 43 error components are included. Volumetric error comprises 43 error components that can separately reduce geometrical and dimensional accuracy of work pieces. The machining accuracy of work piece is guaranteed due to the position of the cutting tool center point (TCP relative to the work piece. The cutting tool is deviated from its ideal position relative to the work piece and machining error is experienced. For compensation process detection of the present tool path and analysis of the RTTTR five-axis CNC machine tools geometrical error, translating current position of component to compensated positions using the Kinematics error model, converting newly created component to new tool paths using the compensation algorithms and finally editing old G-codes using G-code generator algorithm have been employed.
Qianxiang, Zhou
2012-07-01
It is very important to clarify the geometric characteristic of human body segment and constitute analysis model for ergonomic design and the application of ergonomic virtual human. The typical anthropometric data of 1122 Chinese men aged 20-35 years were collected using three-dimensional laser scanner for human body. According to the correlation between different parameters, curve fitting were made between seven trunk parameters and ten body parameters with the SPSS 16.0 software. It can be concluded that hip circumference and shoulder breadth are the most important parameters in the models and the two parameters have high correlation with the others parameters of human body. By comparison with the conventional regressive curves, the present regression equation with the seven trunk parameters is more accurate to forecast the geometric dimensions of head, neck, height and the four limbs with high precision. Therefore, it is greatly valuable for ergonomic design and analysis of man-machine system.This result will be very useful to astronaut body model analysis and application.
Geometrical characteristics of the enlarged fused hard sphere models of simple molecules.
Boublík, Tomas
2005-10-20
The enlarged fused hard sphere model represents a compromise between fused hard sphere- and hard convex body models of repulsive interactions of nonspherical molecules. Geometric functionals of the enlarged fused hard sphere models, i.e., the hard body volume, surface area, and "mean radius" for 25 molecules of the linear and approximately planar shapes (cycloalkanes and aromatic compounds), neopentane and cyclohexane were determined from the bond lengths and bond angles and expressed in the dimensionless form. The hard sphere diameters, first approximated by the values found from the correlation of the second virial coefficients, were then adjusted to heats of vaporization of the studied compounds. Parameters of nonsphericity and molar volumes, evaluated from these characteristics, are compared with parameters of modern semiempirical equations of state (BACK, BACKONE, SAFT). The calculated geometric quantities for a series of compounds make it possible to improve methods of determining the characteristic parameters of the modern semiempirical equations of state, as well as those from the perturbation approaches.
Directory of Open Access Journals (Sweden)
Alexander Bucksch
2017-06-01
Full Text Available The geometries and topologies of leaves, flowers, roots, shoots, and their arrangements have fascinated plant biologists and mathematicians alike. As such, plant morphology is inherently mathematical in that it describes plant form and architecture with geometrical and topological techniques. Gaining an understanding of how to modify plant morphology, through molecular biology and breeding, aided by a mathematical perspective, is critical to improving agriculture, and the monitoring of ecosystems is vital to modeling a future with fewer natural resources. In this white paper, we begin with an overview in quantifying the form of plants and mathematical models of patterning in plants. We then explore the fundamental challenges that remain unanswered concerning plant morphology, from the barriers preventing the prediction of phenotype from genotype to modeling the movement of leaves in air streams. We end with a discussion concerning the education of plant morphology synthesizing biological and mathematical approaches and ways to facilitate research advances through outreach, cross-disciplinary training, and open science. Unleashing the potential of geometric and topological approaches in the plant sciences promises to transform our understanding of both plants and mathematics.
Bucksch, Alexander; Atta-Boateng, Acheampong; Azihou, Akomian F; Battogtokh, Dorjsuren; Baumgartner, Aly; Binder, Brad M; Braybrook, Siobhan A; Chang, Cynthia; Coneva, Viktoirya; DeWitt, Thomas J; Fletcher, Alexander G; Gehan, Malia A; Diaz-Martinez, Diego Hernan; Hong, Lilan; Iyer-Pascuzzi, Anjali S; Klein, Laura L; Leiboff, Samuel; Li, Mao; Lynch, Jonathan P; Maizel, Alexis; Maloof, Julin N; Markelz, R J Cody; Martinez, Ciera C; Miller, Laura A; Mio, Washington; Palubicki, Wojtek; Poorter, Hendrik; Pradal, Christophe; Price, Charles A; Puttonen, Eetu; Reese, John B; Rellán-Álvarez, Rubén; Spalding, Edgar P; Sparks, Erin E; Topp, Christopher N; Williams, Joseph H; Chitwood, Daniel H
2017-01-01
The geometries and topologies of leaves, flowers, roots, shoots, and their arrangements have fascinated plant biologists and mathematicians alike. As such, plant morphology is inherently mathematical in that it describes plant form and architecture with geometrical and topological techniques. Gaining an understanding of how to modify plant morphology, through molecular biology and breeding, aided by a mathematical perspective, is critical to improving agriculture, and the monitoring of ecosystems is vital to modeling a future with fewer natural resources. In this white paper, we begin with an overview in quantifying the form of plants and mathematical models of patterning in plants. We then explore the fundamental challenges that remain unanswered concerning plant morphology, from the barriers preventing the prediction of phenotype from genotype to modeling the movement of leaves in air streams. We end with a discussion concerning the education of plant morphology synthesizing biological and mathematical approaches and ways to facilitate research advances through outreach, cross-disciplinary training, and open science. Unleashing the potential of geometric and topological approaches in the plant sciences promises to transform our understanding of both plants and mathematics.
Energy Technology Data Exchange (ETDEWEB)
Chen, Hsin-Chen; Tan, Jun; Dolly, Steven; Kavanaugh, James; Harold Li, H.; Altman, Michael; Gay, Hiram; Thorstad, Wade L.; Mutic, Sasa; Li, Hua, E-mail: huli@radonc.wustl.edu [Department of Radiation Oncology, Washington University, St. Louis, Missouri 63110 (United States); Anastasio, Mark A. [Department of Biomedical Engineering, Washington University, St. Louis, Missouri 63110 (United States); Low, Daniel A. [Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California 90095 (United States)
2015-02-15
Purpose: One of the most critical steps in radiation therapy treatment is accurate tumor and critical organ-at-risk (OAR) contouring. Both manual and automated contouring processes are prone to errors and to a large degree of inter- and intraobserver variability. These are often due to the limitations of imaging techniques in visualizing human anatomy as well as to inherent anatomical variability among individuals. Physicians/physicists have to reverify all the radiation therapy contours of every patient before using them for treatment planning, which is tedious, laborious, and still not an error-free process. In this study, the authors developed a general strategy based on novel geometric attribute distribution (GAD) models to automatically detect radiation therapy OAR contouring errors and facilitate the current clinical workflow. Methods: Considering the radiation therapy structures’ geometric attributes (centroid, volume, and shape), the spatial relationship of neighboring structures, as well as anatomical similarity of individual contours among patients, the authors established GAD models to characterize the interstructural centroid and volume variations, and the intrastructural shape variations of each individual structure. The GAD models are scalable and deformable, and constrained by their respective principal attribute variations calculated from training sets with verified OAR contours. A new iterative weighted GAD model-fitting algorithm was developed for contouring error detection. Receiver operating characteristic (ROC) analysis was employed in a unique way to optimize the model parameters to satisfy clinical requirements. A total of forty-four head-and-neck patient cases, each of which includes nine critical OAR contours, were utilized to demonstrate the proposed strategy. Twenty-nine out of these forty-four patient cases were utilized to train the inter- and intrastructural GAD models. These training data and the remaining fifteen testing data sets
On integrable deformations of superstring sigma models related to AdSn×Sn supercosets
Directory of Open Access Journals (Sweden)
B. Hoare
2015-08-01
Full Text Available We consider two integrable deformations of 2d sigma models on supercosets associated with AdSn×Sn. The first, the “η-deformation” (based on the Yang–Baxter sigma model, is a one-parameter generalization of the standard superstring action on AdSn×Sn, while the second, the “λ-deformation” (based on the deformed gauged WZW model, is a generalization of the non-abelian T-dual of the AdSn×Sn superstring. We show that the η-deformed model may be obtained from the λ-deformed one by a special scaling limit and analytic continuation in coordinates combined with a particular identification of the parameters of the two models. The relation between the couplings and deformation parameters is consistent with the interpretation of the first model as a real quantum deformation and the second as a root of unity quantum deformation. For the AdS2×S2 case we then explore the effect of this limit on the supergravity background associated with the λ-deformed model. We also suggest that the two models may form a dual Poisson–Lie pair and provide direct evidence for this in the case of the integrable deformations of the coset associated with S2.
STATISTICAL MECHANICS MODELING OF MESOSCALE DEFORMATION IN METALS
Energy Technology Data Exchange (ETDEWEB)
Anter El-Azab
2013-04-08
The research under this project focused on a theoretical and computational modeling of dislocation dynamics of mesoscale deformation of metal single crystals. Specifically, the work aimed to implement a continuum statistical theory of dislocations to understand strain hardening and cell structure formation under monotonic loading. These aspects of crystal deformation are manifestations of the evolution of the underlying dislocation system under mechanical loading. The project had three research tasks: 1) Investigating the statistical characteristics of dislocation systems in deformed crystals. 2) Formulating kinetic equations of dislocations and coupling these kinetics equations and crystal mechanics. 3) Computational solution of coupled crystal mechanics and dislocation kinetics. Comparison of dislocation dynamics predictions with experimental results in the area of statistical properties of dislocations and their field was also a part of the proposed effort. In the first research task, the dislocation dynamics simulation method was used to investigate the spatial, orientation, velocity, and temporal statistics of dynamical dislocation systems, and on the use of the results from this investigation to complete the kinetic description of dislocations. The second task focused on completing the formulation of a kinetic theory of dislocations that respects the discrete nature of crystallographic slip and the physics of dislocation motion and dislocation interaction in the crystal. Part of this effort also targeted the theoretical basis for establishing the connection between discrete and continuum representation of dislocations and the analysis of discrete dislocation simulation results within the continuum framework. This part of the research enables the enrichment of the kinetic description with information representing the discrete dislocation systems behavior. The third task focused on the development of physics-inspired numerical methods of solution of the coupled
Proximal first metatarsal opening wedge osteotomy: geometric analysis on saw bone models.
Kugan, R; Currall, V A; Johal, P; Clark, C I C
2015-03-01
For hallux valgus correction, distal first metatarsal osteotomy is generally used for minor to moderate deformities, diaphyseal osteotomy for moderate deformities and basal osteotomy or arthrodesis for severe deformities. With the advent of locking plates, there has been renewed interest in opening wedge basal osteotomy. We undertook this study in order to understand the power and limitations of this osteotomy. Proximal opening wedge osteotomies were performed on saw bone models in four orientations, with three different wedge sizes: (1) perpendicular to the ground (PG); (2) perpendicular to the shaft (PS); (3) perpendicular to shaft with 30° declination (DEC); (4) 30° oblique (OB). Pre- and post-osteotomy measurements were made of axial and plantar translation and inter-metatarsal angle. Plantar translation and intermetatarsal angle correction increased with increasing wedge size. The DEC osteotomy produced the greatest increase in length of metatarsal shaft, while the PS osteotomy gave the least. The most plantar translation was achieved with the DEC osteotomy. Overall, the PS osteotomy gave the largest correction of the intermetatarsal angle. Although there are several published clinical case series of the proximal opening wedge osteotomy, this is the first study to fully evaluate its geometry. Copyright © 2014 Elsevier Ltd. All rights reserved.
Spinal curvature determination from an X-ray image using a deformable model
Sardjono, T.A.; Wilkinson, M.H.F.; Ooijen, P.M.A. van; Veldhuizen, A.G.; Purnama, K.E.; Verkerke, G.J.; Ibrahim, F; Osman, NAA; Usman, J; Kadri, NA
2007-01-01
This paper presents a spinal curvature determination from frontal X-ray images of scoliotic patients. A new deformable model, Modified CPM (Charged Particles Model), has been developed and used to determine the spinal curvature. The Modified CPM is a new approach of a deformable model based on CPM,
Institute of Scientific and Technical Information of China (English)
徐国良; 潘青
2005-01-01
We construct discrete three- and four-sided surface patches with specified C0 or C1 boundary conditions, using several geometric intrinsic curvature driven flows. These flow equations are solved numerically based on discretizations of the involved differential-geometry operators, which are derived from parametric approximations. The constructed surface patches satisfy certain geometric partial differential equations, and therefore have desirable shape. These patches are assembled together for constructing complicated geometric models for shape design. Multi-resolution representations of the models are achieved using repeated subdivision and evolution.%使用若干个几何本质的曲率驱动的偏微分方程来构造符合指定C0或C1边界条件的三边曲面片和四边曲面片,这些方程的数值解由所涉及的微分几何算子的离散化来得到,微分几何算子的离散化则源于参数逼近.所构造的曲面片满足某些特定的几何偏微分方程,故具有理想的形状,将这些曲面片组装起来便构造出复杂的几何模型.通过反复的子分和演化,得到几何模型的多尺度表示.
Directory of Open Access Journals (Sweden)
Congrong Li
2015-08-01
Full Text Available Forest canopy leaf area index (LAI inversion based on remote sensing data is an important method to obtain LAI. Currently, the most widely-used model to achieve forest canopy structure parameters is the Li-Strahler geometric-optical bidirectional reflectance model, by considering the effect of crown shape and mutual shadowing, which is referred to as the GOMS model. However, it is difficult to retrieve LAI through the GOMS model directly because LAI is not a fundamental parameter of the model. In this study, a gap probability model was used to obtain the relationship between the canopy structure parameter nR2 and LAI. Thus, LAI was introduced into the GOMS model as an independent variable by replacing nR2 The modified GOMS (MGOMS model was validated by application to Dayekou in the Heihe River Basin of China. The LAI retrieved using the MGOMS model with optical multi-angle remote sensing data, high spatial resolution images and field-measured data was in good agreement with the field-measured LAI, with an R-square (R2 of 0.64, and an RMSE of 0.67. The results demonstrate that the MGOMS model obtained by replacing the canopy structure parameter nR2 of the GOMS model with LAI can be used to invert LAI directly and precisely.
Shibkov, A. A.; Zolotov, A. E.; Zheltov, M. A.; Denisov, A. A.; Gasanov, M. F.; Kochegarov, S. S.
2016-05-01
The effect of an electric current on the band formation and the serrated deformation of planar specimens made of an aluminum-magnesium AlMg5 alloy and weakened by holes is experimentally studied. It is found that the concentration of elastic stress fields and the self-localized unstable plastic deformation field near a hole decreases the critical strain of appearance of the first stress drop and hinders the currentinduced suppression of band formation and the serrated Portevin-Le Chatelier deformation. These results are shown not to be related to the concentration of Joule heat near a hole.
Solving a class of geometric programming problems by an efficient dynamic model
Nazemi, Alireza; Sharifi, Elahe
2013-03-01
In this paper, a neural network model is constructed on the basis of the duality theory, optimization theory, convex analysis theory, Lyapunov stability theory and LaSalle invariance principle to solve geometric programming (GP) problems. The main idea is to convert the GP problem into an equivalent convex optimization problem. A neural network model is then constructed for solving the obtained convex programming problem. By employing Lyapunov function approach, it is also shown that the proposed neural network model is stable in the sense of Lyapunov and it is globally convergent to an exact optimal solution of the original problem. The simulation results also show that the proposed neural network is feasible and efficient.
Nedjar, B.
The present work deals with the extension to the geometrically nonlinear case of recently proposed ideas on elastic- and elastoplastic-damage modelling frameworks within the infinitesimal theory. The particularity of these models is that the damage part of the modelling involves the gradient of damage quantity which, together with the equations of motion, are ensuing from a new formulation of the principle of virtual power. It is shown how the thermodynamics of irreversible processes is crucial in the characterization of the dissipative phenomena and in setting the convenient forms for the constitutive relations. On the numerical side, we discuss the problem of numerically integrating these equations and the implementation within the context of the finite element method is described in detail. And finally, we present a set of representative numerical simulations to illustrate the effectiveness of the proposed framework.
Quasi-Topological Gauged Sigma Models, The Geometric Langlands Program, And Knots
Tan, Meng-Chwan
2011-01-01
We construct and study a closed, two-dimensional, quasi-topological (0,2) gauged sigma model with target space a smooth G-manifold, where G is any compact and connected Lie group. When the target space is a flag manifold of simple G, and the gauge group is a Cartan subgroup thereof, the perturbative model describes, purely physically, the recently formulated mathematical theory of "Twisted Chiral Differential Operators". This paves the way, via a generalized T-duality, for a natural physical interpretation of the geometric Langlands correspondence for simply-connected, simple, complex Lie groups. In particular, the Hecke eigensheaves and Hecke operators can be described in terms of the correlation functions of certain operators that underlie the infinite-dimensional chiral algebra of the flag manifold model. Nevertheless, nonperturbative worldsheet twisted-instantons can, in some situations, trivialize the chiral algebra completely. This leads to a spontaneous breaking of supersymmetry whilst implying certain...
Institute of Scientific and Technical Information of China (English)
罗尧治; 杨超
2013-01-01
有限质点法是基于向量式力学提出的一种新兴的数值计算方法.它采用物理计算模式,将分析域定义成一组质点的集合,并根据牛顿第二定律描述质点的运动,从而取代了传统数值方法中数学连续体的概念.该方法通过虚拟逆向运动分离刚体位移和变形位移,并采用变形坐标的形式来计算内力,再利用显式时间积分逐步求解质点运动方程.分析中可以通过描述各质点的轨迹来追踪整体的运动行为.该文阐述了有限质点法的基本概念和原理,推导了平面固体的内力求解公式,并将其应用于平面固体几何大变形问题的数值计算,通过自编程序对实例计算的结果表明,该方法有良好的精度和收敛性,对于求解平面固体的大位移、大转动问题是有效的、可行的.%The finite particle method (FPM) is a new developed method for numerical calculation, which is based on the vector mechanics and physical thoughts. It models the analyzed domain by a set of particles instead of mathematical function and continuous bodies adopted in traditional method, and thus the motion of each particle is directly formulated by Newton's second law. The formulations include a new description of kinematics called fictitious reverse motion to dissect rigid body and deformation displacement, and a set of deformation coordinates for each time increment to evaluate deformation and internal nodal forces. The explicit time integration is adopted to solve the equation of motion. Motions of all particles can describe the whole behavior. The fundamentals of PFM are presented first in this paper. Then, the formulations of the planar solid internal forces are derived. Finally, FPM is applied to the numerical calculations of geometric large deformations of planar solids. The results of numerical examples solved by self-designed program demonstrate that the presented method can achieve good accuracy and convergence. It also shows
De Lucas, Javier
2015-03-01
A simple geometrical model for calculating the effective emissivity in blackbody cylindrical cavities has been developed. The back ray tracing technique and the Monte Carlo method have been employed, making use of a suitable set of coordinates and auxiliary planes. In these planes, the trajectories of individual photons in the successive reflections between the cavity points are followed in detail. The theoretical model is implemented by using simple numerical tools, programmed in Microsoft Visual Basic for Application and Excel. The algorithm is applied to isothermal and non-isothermal diffuse cylindrical cavities with a lid; however, the basic geometrical structure can be generalized to a cylindro-conical shape and specular reflection. Additionally, the numerical algorithm and the program source code can be used, with minor changes, for determining the distribution of the cavity points, where photon absorption takes place. This distribution could be applied to the study of the influence of thermal gradients on the effective emissivity profiles, for example. Validation is performed by analyzing the convergence of the Monte Carlo method as a function of the number of trials and by comparison with published results of different authors.
Dual geometric worm algorithm for two-dimensional discrete classical lattice models
Hitchcock, Peter; Sørensen, Erik S.; Alet, Fabien
2004-07-01
We present a dual geometrical worm algorithm for two-dimensional Ising models. The existence of such dual algorithms was first pointed out by Prokof’ev and Svistunov [N. Prokof’ev and B. Svistunov, Phys. Rev. Lett. 87, 160601 (2001)]. The algorithm is defined on the dual lattice and is formulated in terms of bond variables and can therefore be generalized to other two-dimensional models that can be formulated in terms of bond variables. We also discuss two related algorithms formulated on the direct lattice, applicable in any dimension. These latter algorithms turn out to be less efficient but of considerable intrinsic interest. We show how such algorithms quite generally can be “directed” by minimizing the probability for the worms to erase themselves. Explicit proofs of detailed balance are given for all the algorithms. In terms of computational efficiency the dual geometrical worm algorithm is comparable to well known cluster algorithms such as the Swendsen-Wang and Wolff algorithms, however, it is quite different in structure and allows for a very simple and efficient implementation. The dual algorithm also allows for a very elegant way of calculating the domain wall free energy.
Institute of Scientific and Technical Information of China (English)
Abdul Wahid Khan; Chen Wuyi
2010-01-01
A systematic geometric model has been presented for calibration of a newly designed 5-axis turbine blade grinding machine.This machine is designed to serve a specific purpose to attain high accuracy and high efficiency grinding of turbine blades by eliminating the hand grinding process.Although its topology is RPPPR (P:prismatic;R:rotary),its design is quite distinct from the competitive machine tools.As error quantification is the only way to investigate,maintain and improve its accuracy,calibration is recommended for its performance assessment and acceptance testing.Systematic geometric error modeling technique is implemented and 52 position dependent and position independent errors are identified while considering the machine as five rigid bodies by eliminating the set-up errors ofworkpiece and cutting tool.39 of them are found to have influential errors and are accommodated for finding the resultant effect between the cutting tool and the workpiece in workspace volume.Rigid body kinematics techniques and homogenous transformation matrices are used for error synthesis.
Understanding geometric instabilities in thin films via a multi-layer model.
Lejeune, Emma; Javili, Ali; Linder, Christian
2016-01-21
When a thin stiff film adhered to a compliant substrate is subject to compressive stresses, the film will experience a geometric instability and buckle out of plane. For high film/substrate stiffness ratios with relatively low levels of strain, the primary mode of instability will either be wrinkling or buckling delamination depending on the material and geometric properties of the system. Previous works approach these systems by treating the film and substrate as homogenous layers, either consistently perfectly attached, or perfectly unattached at interfacial flaws. However, this approach neglects systems where the film and substrate are uniformly weakly attached or where interfacial layers due to surface modifications in either the film or substrate are present. Here we demonstrate a method for accounting for these additional thin surface layers via an analytical solution verified by numerical results. The main outcome of this work is an improved understanding of how these layers influence global behavior. We demonstrate the utility of our model with applications ranging from buckling based metrology in ultrathin films, to an improved understanding of the formation of a novel surface in carbon nanotube bio-interface films. Moving forward, this model can be used to interpret experimental results, particularly for systems which deviate from traditional behavior, and aid in the evaluation and design of future film/substrate systems.
Three-Dimensional Geometrical Modelling of Wild Boar Head by Reverse Engineering Technology
Institute of Scientific and Technical Information of China (English)
Liang Xu; Min-xu Lin; Jian-qiao Li; Zhao-liang Wang; B. Chirende
2008-01-01
In this paper, a wild boar head was taken as the bionic research object for the development of new ridgers, a kind of plough."The reverse engineering technology was adopted to obtain the surface geometrical information of the head. Several three-dimensional (3D) point clouds of the head were captured first using a non-touch laser scanner, and an integrated point cloud was generated by aligning these point clouds using UG/Imageware. Then, the digital surface model of the head was rebuilt by means of CATIA. The characteristic curves of the surface model were analyzed. The results show that the average error between the rebuilt surface and the point cloud is -0.431 mm. The max curvature of the ridge on the neb of the head is 0.187 mm-1, and the max and rain Gauss curvatures on the surface are 0.008 mm-2 and -0.002 mm-2. These geometrical information are the essential parameters for biomimetics study of the ridger.
Growing Random Geometric Graph Models of Super-linear Scaling Law
Zhang, Jiang
2012-01-01
Recent researches on complex systems highlighted the so-called super-linear growth phenomenon. As the system size $P$ measured as population in cities or active users in online communities increases, the total activities $X$ measured as GDP or number of new patents, crimes in cities generated by these people also increases but in a faster rate. This accelerating growth phenomenon can be well described by a super-linear power law $X \\propto P^{\\gamma}$($\\gamma>1$). However, the explanation on this phenomenon is still lack. In this paper, we propose a modeling framework called growing random geometric models to explain the super-linear relationship. A growing network is constructed on an abstract geometric space. The new coming node can only survive if it just locates on an appropriate place in the space where other nodes exist, then new edges are connected with the adjacent nodes whose number is determined by the density of existing nodes. Thus the total number of edges can grow with the number of nodes in a f...
Directory of Open Access Journals (Sweden)
Santosh Sanodiya
2017-03-01
Full Text Available The present paper examines the deformation behaviour of geometrical specimens of an aluminium alloy undergoing axial compression in a Universal Testing Machine under dry condition. It is observed that researchers have made attempts to investigate alternate specimens for friction calibration. It is found that ring compression test is recommended as the standard test for determination of coefficient of friction, because it gives reliable results. The effect of weight percentage of silicon carbide on microstructure, hardness and upsetting load is studied. The friction factor at die metal interface is evaluated by ring compression tests and its effect on non-uniform deformation is investigated. The experimental results are finally compared with those obtained by FEA simulation and modelling. In order to validate the predictability of these specimens, real experiments on them are carried out. Rings of standard dimensional ratio 6:3:1 in the same machine. Friction predictions from both specimen are found to be in close match, proposed alternate specimen offers a powerful tool for friction prediction in the absence of ring specimen. Some aspects of Exergy calculations have been in the past repeatedly used to quantify the quality and quantity of energy used in thermal energy processes. This attempt to drive a exergy utilization and compare for the first time two entirely different manufacturing processes, material processing by a mechanical method of straining of the material and thermal processing during cold forging of the same mass of the material using exergy formulation as metric. The exergy analysis of material processing is determined by performed work and utilized heat transfer using mechanical and thermal processes
Brock, Kristy K.; Ménard, Cynthia; Hensel, Jennifer; Jaffray, David A.
2006-03-01
Magnetic resonance imaging (MRI) with an endorectal receiver coil (ERC) provides superior visualization of the prostate gland and its surrounding anatomy at the expense of large anatomical deformation. The ability to correct for this deformation is critical to integrate the MR images into the CT-based treatment planning for radiotherapy. The ability to quantify and understand the physiological motion due to large changes in rectal filling can also improve the precision of image-guided procedures. The purpose of this study was to understand the biomechanical relationship between the prostate, rectum, and bladder using a finite element-based multi-organ deformable image registration method, 'Morfeus' developed at our institution. Patients diagnosed with prostate cancer were enrolled in the study. Gold seed markers were implanted in the prostate and MR scans performed with the ERC in place and its surrounding balloon inflated to varying volumes (0-100cc). The prostate, bladder, and rectum were then delineated, converted into finite element models, and assigned appropriate material properties. Morfeus was used to assign surface interfaces between the adjacent organs and deform the bladder and rectum from one position to another, obtaining the position of the prostate through finite element analysis. This approach achieves sub-voxel accuracy of image co-registration in the context of a large ERC deformation, while providing a biomechanical understanding of the multi-organ physiological relationship between the prostate, bladder, and rectum. The development of a deformable registration strategy is essential to integrate the superior information offered in MR images into the treatment planning process.
Model Attitude and Deformation Measurements at the NASA Glenn Research Center
Woike, Mark R.
2008-01-01
The NASA Glenn Research Center is currently participating in an American Institute of Aeronautics and Astronautics (AIAA) sponsored Model Attitude and Deformation Working Group. This working group is chartered to develop a best practices document dealing with the measurement of two primary areas of wind tunnel measurements, 1) model attitude including alpha, beta and roll angle, and 2) model deformation. Model attitude is a principle variable in making aerodynamic and force measurements in a wind tunnel. Model deformation affects measured forces, moments and other measured aerodynamic parameters. The working group comprises of membership from industry, academia, and the Department of Defense (DoD). Each member of the working group gave a presentation on the methods and techniques that they are using to make model attitude and deformation measurements. This presentation covers the NASA Glenn Research Center s approach in making model attitude and deformation measurements.
Directory of Open Access Journals (Sweden)
Yaohua Deng
2015-01-01
Full Text Available This paper discusses the calculation problems of bending deformation of FWP processing. Take three axis CNC machining as an example, to establish mechanics model of flexible workpiece processing process. The flexible workpiece balance equation is a two-dimensional partial differential equation, to solve the problem of flexible workpiece bending deformation using Rayleigh-Ritz method and designing the test function of bending deformation of flexible workpiece. By satisfying the minimum potential energy condition of FWP processing to work out the approximate solution of bending deformation of flexible workpiece, find out the relationship between material properties of flexible piece, acting force Fz, and deformation value. Finally, the rectangle flexible workpiece which is made up of polyurethane sponge is selected as an experiment subject. The results show that the average relative deviation between theoretical value and observed value is only 5.51%. It is proved that the bending deformation test function satisfies the actual deformation calculation requirements.
New geometric design consistency model based on operating speed profiles for road safety evaluation.
Camacho-Torregrosa, Francisco J; Pérez-Zuriaga, Ana M; Campoy-Ungría, J Manuel; García-García, Alfredo
2013-12-01
To assist in the on-going effort to reduce road fatalities as much as possible, this paper presents a new methodology to evaluate road safety in both the design and redesign stages of two-lane rural highways. This methodology is based on the analysis of road geometric design consistency, a value which will be a surrogate measure of the safety level of the two-lane rural road segment. The consistency model presented in this paper is based on the consideration of continuous operating speed profiles. The models used for their construction were obtained by using an innovative GPS-data collection method that is based on continuous operating speed profiles recorded from individual drivers. This new methodology allowed the researchers to observe the actual behavior of drivers and to develop more accurate operating speed models than was previously possible with spot-speed data collection, thereby enabling a more accurate approximation to the real phenomenon and thus a better consistency measurement. Operating speed profiles were built for 33 Spanish two-lane rural road segments, and several consistency measurements based on the global and local operating speed were checked. The final consistency model takes into account not only the global dispersion of the operating speed, but also some indexes that consider both local speed decelerations and speeds over posted speeds as well. For the development of the consistency model, the crash frequency for each study site was considered, which allowed estimating the number of crashes on a road segment by means of the calculation of its geometric design consistency. Consequently, the presented consistency evaluation method is a promising innovative tool that can be used as a surrogate measure to estimate the safety of a road segment.
Design of Wideband MIMO Car-to-Car Channel Models Based on the Geometrical Street Scattering Model
Directory of Open Access Journals (Sweden)
Nurilla Avazov
2012-01-01
Full Text Available We propose a wideband multiple-input multiple-output (MIMO car-to-car (C2C channel model based on the geometrical street scattering model. Starting from the geometrical model, a MIMO reference channel model is derived under the assumption of single-bounce scattering in line-of-sight (LOS and non-LOS (NLOS propagation environments. The proposed channel model assumes an infinite number of scatterers, which are uniformly distributed in two rectangular areas located on both sides of the street. Analytical solutions are presented for the space-time-frequency cross-correlation function (STF-CCF, the two-dimensional (2D space CCF, the time-frequency CCF (TF-CCF, the temporal autocorrelation function (ACF, and the frequency correlation function (FCF. An efficient sum-of-cisoids (SOCs channel simulator is derived from the reference model. It is shown that the temporal ACF and the FCF of the SOC channel simulator fit very well to the corresponding correlation functions of the reference model. To validate the proposed channel model, the mean Doppler shift and the Doppler spread of the reference model have been matched to real-world measurement data. The comparison results demonstrate an excellent agreement between theory and measurements, which confirms the validity of the derived reference model. The proposed geometry-based channel simulator allows us to study the effect of nearby street scatterers on the performance of C2C communication systems.
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
It is showed that all equations of the linearized Gurtin-Murdoch model of surface elasticity can be derived, in a straightforward way, from a simple second-order expression for the ratio of deformed surface area to initial surface area. This elementary derivation offers a simple explanation for all unique features of the model and its simplified/modified versions, and helps to clarify some misunderstandings of the model already occurring in the literature. Finally, it is demonstrated that, because the Gurtin-Murdoch model is based on a hybrid formulation combining linearized deformation of bulk material with 2nd-order finite deformation of the surface, caution is needed when the original form of this model is applied to bending deformation of thin-walled elastic structures with surface stress.
Lüdde, H. J.; Achenbach, A.; Kalkbrenner, T.; Jankowiak, H. C.; Kirchner, T.
2016-05-01
A recently introduced model to account for geometric screening corrections in an independent-atom-model description of ion-molecule collisions is applied to proton collisions from amino acids and DNA and RNA nucleobases. The correction coefficients are obtained from using a pixel counting method (PCM) for the exact calculation of the effective cross sectional area that emerges when the molecular cross section is pictured as a structure of (overlapping) atomic cross sections. This structure varies with the relative orientation of the molecule with respect to the projectile beam direction and, accordingly, orientation-independent total cross sections are obtained from averaging the pixel count over many orientations. We present net capture and net ionization cross sections over wide ranges of impact energy and analyze the strength of the screening effect by comparing the PCM results with Bragg additivity rule cross sections and with experimental data where available. Work supported by NSERC, Canada.
Mean-field dynamic criticality and geometric transition in the Gaussian core model
Coslovich, Daniele; Ikeda, Atsushi; Miyazaki, Kunimasa
2016-04-01
We use molecular dynamics simulations to investigate dynamic heterogeneities and the potential energy landscape of the Gaussian core model (GCM). Despite the nearly Gaussian statistics of particles' displacements, the GCM exhibits giant dynamic heterogeneities close to the dynamic transition temperature. The divergence of the four-point susceptibility is quantitatively well described by the inhomogeneous version of the mode-coupling theory. Furthermore, the potential energy landscape of the GCM is characterized by large energy barriers, as expected from the lack of activated, hopping dynamics, and display features compatible with a geometric transition. These observations demonstrate that all major features of mean-field dynamic criticality can be observed in a physically sound, three-dimensional model.
A 5G Hybrid Channel Model Considering Rays and Geometric Stochastic Propagation Graph
DEFF Research Database (Denmark)
Steinböck, Gerhard; Karstensen, Anders; Kyösti, Pekka
2016-01-01
We consider a ray-tracing tool, in particular the METIS map based model for deterministic simulation of the channel impulse response. The ray-tracing tool is extended by adding a geometric stochastic propagation graph to model additional stochastic paths and the dense multipath components observed...... in measurements. The computational complexity of raytracing typically prohibits the inclusion of the dense multipath component or limits it to the early part of the impulse response. Due to computational reasons and for lack of detailed information is the description of the environment for ray-tracing often very...... simplistic, e.g. plain walls and thus neglecting the structures on the building facades, window frames, window sills, etc. Thus in measurements there are often additional components observed that are not captured by these simplistic ray-tracing implementations. In this contribution we introduce a flexible...
Directory of Open Access Journals (Sweden)
Gayo Willy
2016-01-01
Full Text Available Philippine Stock Exchange Composite Index (PSEi is the main stock index of the Philippine Stock Exchange (PSE. PSEi is computed using a weighted mean of the top 30 publicly traded companies in the Philippines, called component stocks. It provides a single value by which the performance of the Philippine stock market is measured. Unfortunately, these weights, which may vary for every trading day, are not disclosed by the PSE. In this paper, we propose a model of forecasting the PSEi by estimating the weights based on historical data and forecasting each component stock using Monte Carlo simulation based on a Geometric Brownian Motion (GBM assumption. The model performance is evaluated and its forecast compared is with the results using a direct GBM forecast of PSEi over different forecast periods. Results showed that the forecasts using WGBM will yield smaller error compared to direct GBM forecast of PSEi.
Modeling Geometric-Temporal Context With Directional Pyramid Co-Occurrence for Action Recognition.
Yuan, Chunfeng; Li, Xi; Hu, Weiming; Ling, Haibin; Maybank, Stephen J
2014-02-01
In this paper, we present a new geometric-temporal representation for visual action recognition based on local spatio-temporal features. First, we propose a modified covariance descriptor under the log-Euclidean Riemannian metric to represent the spatio-temporal cuboids detected in the video sequences. Compared with previously proposed covariance descriptors, our descriptor can be measured and clustered in Euclidian space. Second, to capture the geometric-temporal contextual information, we construct a directional pyramid co-occurrence matrix (DPCM) to describe the spatio-temporal distribution of the vector-quantized local feature descriptors extracted from a video. DPCM characterizes the co-occurrence statistics of local features as well as the spatio-temporal positional relationships among the concurrent features. These statistics provide strong descriptive power for action recognition. To use DPCM for action recognition, we propose a directional pyramid co-occurrence matching kernel to measure the similarity of videos. The proposed method achieves the state-of-the-art performance and improves on the recognition performance of the bag-of-visual-words (BOVWs) models by a large margin on six public data sets. For example, on the KTH data set, it achieves 98.78% accuracy while the BOVW approach only achieves 88.06%. On both Weizmann and UCF CIL data sets, the highest possible accuracy of 100% is achieved.
Comparison of geometrical shock dynamics and kinematic models for shock-wave propagation
Ridoux, J.; Lardjane, N.; Monasse, L.; Coulouvrat, F.
2017-09-01
Geometrical shock dynamics (GSD) is a simplified model for nonlinear shock-wave propagation, based on the decomposition of the shock front into elementary ray tubes. Assuming small changes in the ray tube area, and neglecting the effect of the post-shock flow, a simple relation linking the local curvature and velocity of the front, known as the A{-}M rule, is obtained. More recently, a new simplified model, referred to as the kinematic model, was proposed. This model is obtained by combining the three-dimensional Euler equations and the Rankine-Hugoniot relations at the front, which leads to an equation for the normal variation of the shock Mach number at the wave front. In the same way as GSD, the kinematic model is closed by neglecting the post-shock flow effects. Although each model's approach is different, we prove their structural equivalence: the kinematic model can be rewritten under the form of GSD with a specific A{-}M relation. Both models are then compared through a wide variety of examples including experimental data or Eulerian simulation results when available. Attention is drawn to the simple cases of compression ramps and diffraction over convex corners. The analysis is completed by the more complex cases of the diffraction over a cylinder, a sphere, a mound, and a trough.
Institute of Scientific and Technical Information of China (English)
ZHU Limin; HE Gaiyun; SONG Zhanjie
2016-01-01
Product variation reduction is critical to improve process efficiency and product quality, especially for multistage machining process (MMP). However, due to the variation accumulation and propagation, it becomes quite difficult to predict and reduce product variation for MMP. While the method of statistical process control can be used to control product quality, it is used mainly to monitor the process change rather than to analyze the cause of product variation. In this paper, based on a differential description of the contact kinematics of locators and part surfaces, and the geometric constraints equation defined by the locating scheme, an improved analytical variation propagation model for MMP is presented. In which the influence of both locator position and machining error on part quality is considered while, in traditional model, it usually focuses on datum error and fixture error. Coordinate transformation theory is used to reflect the generation and transmission laws of error in the establishment of the model. The concept of deviation matrix is heavily applied to establish an explicit mapping between the geometric deviation of part and the process error sources. In each machining stage, the part deviation is formulized as three separated components corresponding to three different kinds of error sources, which can be further applied to fault identification and design optimization for complicated machining process. An example part for MMP is given out to validate the effectiveness of the methodology. The experiment results show that the model prediction and the actual measurement match well. This paper provides a method to predict part deviation under the influence of fixture error, datum error and machining error, and it enriches the way of quality prediction for MMP.
Jiao, F.; Mohles, V.; Miroux, A.G.; Bollmann, C.
2014-01-01
Microstructure and microchemistry evolution during hot deformation and subsequent annealing of a commercial Al-Mg-Si alloy were experimentally investigated using electron backscatter diffraction (EBSD) and SEM. Meanwhile, a through-process model framework consisting of the deformation model GIA-3IVM
Jiao, F.; Mohles, V.; Miroux, A.G.; Bollmann, C.
2014-01-01
Microstructure and microchemistry evolution during hot deformation and subsequent annealing of a commercial Al-Mg-Si alloy were experimentally investigated using electron backscatter diffraction (EBSD) and SEM. Meanwhile, a through-process model framework consisting of the deformation model GIA-3IVM