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Sample records for based geometrical model

  1. Knowledge-based geometric modeling in construction

    DEFF Research Database (Denmark)

    Bonev, Martin; Hvam, Lars

    2012-01-01

    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 for...

  2. Analysis of Geometrical Specification Model Based on the New GeometricalProduct Specification Language

    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.

  3. Image-Based Geometric Modeling and Mesh Generation

    CERN Document Server

    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,...

  4. Water flow based geometric active deformable model for road network

    Science.gov (United States)

    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.

  5. 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.

  6. Pragmatic geometric model evaluation

    Science.gov (United States)

    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

  7. 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.

  8. A Hybrid Model for Biometric Authentication using Finger Back Knuckle Surface based on Angular Geometric Analysis

    OpenAIRE

    Usha, K.; M. Ezhilarasan

    2013-01-01

    Biometric based personal recognition is an efficient method for identifying a person. Recently, hand based biometric has become popular due to its various advantages such as high verification accuracy and high user acceptability. This paper proposes a hybrid model using an emerging hand based biometric trait known as Finger Back Knuckle Surface. This model is based on angular geometric analysis which is implemented on two different samples of Finger Back Knuckle Surface such as Finger Bend Kn...

  9. Matching Aerial Images to 3d Building Models Based on Context-Based Geometric Hashing

    Science.gov (United States)

    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.

  10. 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.

  11. Geometrical Model of Solar Radiation Pressure Based on High-Performing Galileo Clocks - First Geometrical Mapping of the Yarkowsky effect

    Science.gov (United States)

    Svehla, Drazen; Rothacher, Markus; Hugentobler, Urs; Steigenberger, Peter; Ziebart, Marek

    2014-05-01

    depends on the orbit quality and should rather be called GNSS orbit bias instead of SLR bias. When LEO satellite orbits are estimated using GPS, this GPS orbit bias is mapped into the antenna phase center. All LEO satellites, such as CHAMP, GRACE and JASON-1/2, need an adjustment of the radial antenna phase center offset. GNSS orbit translations towards the Sun in the orbital plane do not only propagate into the estimated LEO orbits, but also into derived gravity field and altimetry products. Geometrical mapping of orbit perturbations using an on board GNSS clock is a new technique to monitor orbit perturbations along the orbit and was successfully applied in the modeling of Solar radiation pressure. We show that CODE Solar radiation pressure parameterization lacks dependency with the Sun's elevation, i.e. elongation angle (rotation of Solar arrays), especially at low Sun elevations (eclipses). Parameterisation with the Sun elongation angle is used in the so-called T30 model (ROCK-model) that includes thermal re-radiation. A preliminary version of Solar radiation pressure for the first five Galileo and the GPS-36 satellite is based on 2×180 days of the MGEX Campaign. We show that Galileo clocks map the Yarkowsky effect along the orbit, i.e. the lag between the Sun's illumination and thermal re-radiation. We present the first geometrical mapping of anisotropic thermal emission of absorbed sunlight of an illuminated satellite. In this way, the effects of Solar radiation pressure can be modelled with only two paramaters for all Sun elevations.

  12. Surface-based geometric modelling using teaching trees for advanced robots

    International Nuclear Information System (INIS)

    Geometric modelling of the environment is important in robot motion planning. Generally, shapes can be stored in a data base, so the elements that need to be decided are positions and orientations. In this paper, surface-based geometric modelling using a teaching tree is proposed. In this modelling, combinations of surfaces are considered in order to decide positions and orientations of objects. The combinations are represented by a depth-first tree, which makes it easy for the operator to select one combination out of several. This method is effective not only in the case when perfect data can be obtained, but also when conditions for measurement of three-dimensional data are unfavorable, which often occur in the environment of a working robot. (author)

  13. Model-based recognition of 3-D objects by geometric hashing technique

    International Nuclear Information System (INIS)

    A model-based object recognition system is developed for recognition of polyhedral objects. The system consists of feature extraction, modelling and matching stages. Linear features are used for object descriptions. Lines are obtained from edges using rotation transform. For modelling and recognition process, geometric hashing method is utilized. Each object is modelled using 2-D views taken from the viewpoints on the viewing sphere. A hidden line elimination algorithm is used to find these views from the wire frame model of the objects. The recognition experiments yielded satisfactory results. (author). 8 refs, 5 figs

  14. A Hybrid Model for Biometric Authentication using Finger Back Knuckle Surface based on Angular Geometric Analysis

    Directory of Open Access Journals (Sweden)

    K.Usha

    2013-08-01

    Full Text Available Biometric based personal recognition is an efficient method for identifying a person. Recently, hand based biometric has become popular due to its various advantages such as high verification accuracy and high user acceptability. This paper proposes a hybrid model using an emerging hand based biometric trait known as Finger Back Knuckle Surface. This model is based on angular geometric analysis which is implemented on two different samples of Finger Back Knuckle Surface such as Finger Bend Knuckle Surface and Finger Intact Knuckle Surface for the extraction of knuckle feature information. The obtained feature information from both the surfaces is fused using feature information level fusion technique to authenticate the individuals. Experiments were conducted using newly created database for both Bend Knuckle and Intact Knuckle Surface. The results were promising in terms of accuracy, speed and computational complexity.

  15. 基于新一代产品几何规范(GPS)语言的几何规范模型分析%Analysis of Geometrical Specification Model Based on the New Geometrical Product Specification Language

    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 covering 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.

  16. New geometric design consistency model based on operating speed profiles for road safety evaluation.

    Science.gov (United States)

    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. PMID:23176754

  17. Mathematical Model and Geometrical Model of Double Pitch ZN-type Worm Gear Set Based on Generation Mechanism

    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.

  18. Geometric Computing Based on Computerized Descriptive Geometric

    Institute of Scientific and Technical Information of China (English)

    YU Hai-yan; HE Yuan-Jun

    2011-01-01

    Computer-aided Design (CAD), video games and other computer graphic related technology evolves substantial processing to geometric elements. A novel geometric computing method is proposed with the integration of descriptive geometry, math and computer algorithm. Firstly, geometric elements in general position are transformed to a special position in new coordinate system. Then a 3D problem is projected to new coordinate planes. Finally, according to 2D/3D correspondence principle in descriptive geometry, the solution is constructed computerized drawing process with ruler and compasses. In order to make this method a regular operation, a two-level pattern is established. Basic Layer is a set algebraic packaged function including about ten Primary Geometric Functions (PGF) and one projection transformation. In Application Layer, a proper coordinate is established and a sequence of PGFs is sought for to get the final results. Examples illustrate the advantages of our method on dimension reduction, regulatory and visual computing and robustness.

  19. A Geometrical-Based Model for Cochannel Interference Analysis and Capacity Estimation of CDMA Cellular Systems

    Directory of Open Access Journals (Sweden)

    Konstantinos B. Baltzis

    2008-10-01

    Full Text Available A common assumption in cellular communications is the circular-cell approximation. In this paper, an alternative analysis based on the hexagonal shape of the cells is presented. A geometrical-based stochastic model is proposed to describe the angle of arrival of the interfering signals in the reverse link of a cellular system. Explicit closed form expressions are derived, and simulations performed exhibit the characteristics and validate the accuracy of the proposed model. Applications in the capacity estimation of WCDMA cellular networks are presented. Dependence of system capacity of the sectorization of the cells and the base station antenna radiation pattern is explored. Comparisons with data in literature validate the accuracy of the proposed model. The degree of error of the hexagonal and the circular-cell approaches has been investigated indicating the validity of the proposed model. Results have also shown that, in many cases, the two approaches give similar results when the radius of the circle equals to the hexagon inradius. A brief discussion on how the proposed technique may be applied to broadband access networks is finally made.

  20. Improved quality prediction model for multistage machining process based on geometric constraint equation

    Science.gov (United States)

    Zhu, Limin; He, Gaiyun; Song, Zhanjie

    2016-03-01

    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.

  1. Geometric Generalisation of Surrogate Model-Based Optimisation to Combinatorial and Program Spaces

    Directory of Open Access Journals (Sweden)

    Yong-Hyuk Kim

    2014-01-01

    Full Text Available Surrogate models (SMs can profitably be employed, often in conjunction with evolutionary algorithms, in optimisation in which it is expensive to test candidate solutions. The spatial intuition behind SMs makes them naturally suited to continuous problems, and the only combinatorial problems that have been previously addressed are those with solutions that can be encoded as integer vectors. We show how radial basis functions can provide a generalised SM for combinatorial problems which have a geometric solution representation, through the conversion of that representation to a different metric space. This approach allows an SM to be cast in a natural way for the problem at hand, without ad hoc adaptation to a specific representation. We test this adaptation process on problems involving binary strings, permutations, and tree-based genetic programs.

  2. Particle-Based Geometric and Mechanical Modelling of Woven Technical Textiles and Reinforcements for Composites

    Science.gov (United States)

    Samadi, Reza

    Technical textiles are increasingly being engineered and used in challenging applications, in areas such as safety, biomedical devices, architecture and others, where they must meet stringent demands including excellent and predictable load bearing capabilities. They also form the bases for one of the most widespread group of composite materials, fibre reinforced polymer-matrix composites (PMCs), which comprise materials made of stiff and strong fibres generally available in textile form and selected for their structural potential, combined with a polymer matrix that gives parts their shape. Manufacturing processes for PMCs and technical textiles, as well as parts and advanced textile structures must be engineered, ideally through simulation, and therefore diverse properties of the textiles, textile reinforcements and PMC materials must be available for predictive simulation. Knowing the detailed geometry of technical textiles is essential to predicting accurately the processing and performance properties of textiles and PMC parts. In turn, the geometry taken by a textile or a reinforcement textile is linked in an intricate manner to its constitutive behaviour. This thesis proposes, investigates and validates a general numerical tool for the integrated and comprehensive analysis of textile geometry and constitutive behaviour as required toward engineering applications featuring technical textiles and textile reinforcements. The tool shall be general with regards to the textiles modelled and the loading cases applied. Specifically, the work aims at fulfilling the following objectives: 1) developing and implementing dedicated simulation software for modelling textiles subjected to various load cases; 2) providing, through simulation, geometric descriptions for different textiles subjected to different load cases namely compaction, relaxation and shear; 3) predicting the constitutive behaviour of the textiles undergoing said load cases; 4) identifying parameters

  3. 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.

  4. Computer Graphics & Geometric Modeling

    OpenAIRE

    Zsombor-Murray, Paul; O'Leary, Paul

    2006-01-01

    Least squares fitting of point sets to lines, planes, curves and surfaces is carried out using eigenvalues and eigenvectors to find the major principal moment of inertia axis of a point set taken as representing the mass distribution of a rigid body. This engineering geometric approach produces identical results when compared to methods of conventional minimization using partial derivatives with respect to linear equation coefficients. Extending the approach to the fitting of conics and quadr...

  5. PlantGL: A Python-based geometric library for 3D plant modelling at different scales

    OpenAIRE

    Pradal, Christophe; Boudon, Frédéric; Nouguier, Christophe; Chopard, Jérôme; Godin, Christophe

    2009-01-01

    International audience In this paper, we present PlantGL, an open-source graphic toolkit for the creation, simulation and analysis of 3D virtual plants. This C++ geometric library is embedded in the Python language which makes it a powerful user-interactive platform for plant modeling in various biological application domains. PlantGL makes it possible to build and manipulate geometric models of plants or plant parts, ranging from tissues and organs to plant populations. Based on a scene g...

  6. Phenomenological modeling of Geometric Metasurfaces

    CERN Document Server

    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.

  7. 5th Dagstuhl Seminar on Geometric Modelling

    CERN Document Server

    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

  8. Development of Large Concrete Object Geometrical Model Based on Terrestrial Laser Scanning

    Directory of Open Access Journals (Sweden)

    Zaczek-Peplinska Janina

    2015-02-01

    Full Text Available The paper presents control periodic measurements of movements and survey of concrete dam on Dunajec River in Rożnów, Poland. Topographical survey was conducted using laser scanning technique. The goal of survey was data collection and creation of a geometrical model. Acquired cross- and horizontal sections were utilised to create a numerical model of object behaviour at various load depending of changing level of water in reservoir. Modelling was accomplished using finite elements technique. During the project an assessment was conducted to terrestrial laser scanning techniques for such type of research of large hydrotechnical objects such as gravitational water dams. Developed model can be used to define deformations and displacement prognosis.

  9. A new geometric-based model to accurately estimate arm and leg inertial estimates.

    Science.gov (United States)

    Wicke, Jason; Dumas, Geneviève A

    2014-06-01

    Segment estimates of mass, center of mass and moment of inertia are required input parameters to analyze the forces and moments acting across the joints. The objectives of this study were to propose a new geometric model for limb segments, to evaluate it against criterion values obtained from DXA, and to compare its performance to five other popular models. Twenty five female and 24 male college students participated in the study. For the criterion measures, the participants underwent a whole body DXA scan, and estimates for segment mass, center of mass location, and moment of inertia (frontal plane) were directly computed from the DXA mass units. For the new model, the volume was determined from two standing frontal and sagittal photographs. Each segment was modeled as a stack of slices, the sections of which were ellipses if they are not adjoining another segment and sectioned ellipses if they were adjoining another segment (e.g. upper arm and trunk). Length of axes of the ellipses was obtained from the photographs. In addition, a sex-specific, non-uniform density function was developed for each segment. A series of anthropometric measurements were also taken by directly following the definitions provided of the different body segment models tested, and the same parameters determined for each model. Comparison of models showed that estimates from the new model were consistently closer to the DXA criterion than those from the other models, with an error of less than 5% for mass and moment of inertia and less than about 6% for center of mass location. PMID:24735506

  10. Kinetic modeling of thermal decomposition of zinc ferrite from neutral leach residues based on stochastic geometric model

    International Nuclear Information System (INIS)

    The stochastic geometric model was applied to kinetic modeling the complex process of thermal decomposition of zinc ferrite from neutral leach residues, at different operating temperatures (600 °C, 750 °C, 950 °C and 1150 °C). Based on functional dependence of Avrami's constant (n) in a function of the effective activation energy (Ea), it was found that at T>950 °C, the crystallization process takes place in autocatalytic stage, under the conditions where the rate of nucleation rapidly increases. It was established that the high nucleation rate can be attributed to formation of both Zn and Fe rich regions which provide a high number of heterogeneous nucleation sites. Based on the obtained final shape of the particles, it was found a strong presence of zinc, iron (present only in the form of Fe3O4 (magnetite)), magnesium (in the form of Mg2Si2O6), and also lead oxides. Thermodynamic analysis showed that the decomposition depends on the introduction of heat, and exerts a positive value of the Gibbs free energy of activation. Such a feature was expected since the ferrite system has been submitted to a forced decomposition and volatilization reactions. - Highlights: • Thermo-chemical investigations. • Autocatalytic stage of process, where the rate of nucleation rapidly increases. • Iron is present in the form of Fe3O4 (magnetite). • The possibility of preparing of the nanosized magnetic particles. • Final product which underwent decomposition has the magnetic properties

  11. Geometric filters for protein–ligand complexes based on phenomenological molecular models

    Directory of Open Access Journals (Sweden)

    Sudakov O. O.

    2013-09-01

    Full Text Available Molecular docking is a widely used method of computer-aided drug design capable of accurate prediction of protein-ligand complex conformations. However, scoring functions used to estimate free energy of binding still lack accuracy. Aim. Development of computationally simple and rapid algorithms for ranking ligands based on docking results. Methods. Computational filters utilizing geometry of protein-ligand complex were designed. Efficiency of the filters was verified in a cross-docking study with QXP/Flo software using crystal structures of human serine proteases thrombin (F2 and factor Xa (F10 and two corresponding sets of known selective inhibitors. Results. Evaluation of filtering results in terms of ROC curves with varying filter threshold value has shown their efficiency. However, none of the filters outperformed QXP/Flo built-in scoring function Pi . Nevertheless, usage of the filters with optimized set of thresholds in combination with Pi achieved significant improvement in performance of ligand selection when compared to usage of Pi alone. Conclusions. The proposed geometric filters can be used as a complementary to traditional scoring functions in order to optimize ligand search performance and decrease usage of computational and human resources.

  12. Nonlinear aeroelastic modelling for wind turbine blades based on blade element momentum theory and geometrically exact beam theory

    International Nuclear Information System (INIS)

    Due to the increasing size and flexibility of large wind turbine blades, accurate and reliable aeroelastic modelling is playing an important role for the design of large wind turbines. Most existing aeroelastic models are linear models based on assumption of small blade deflections. This assumption is not valid anymore for very flexible blade design because such blades often experience large deflections. In this paper, a novel nonlinear aeroelastic model for large wind turbine blades has been developed by combining BEM (blade element momentum) theory and mixed-form formulation of GEBT (geometrically exact beam theory). The nonlinear aeroelastic model takes account of large blade deflections and thus greatly improves the accuracy of aeroelastic analysis of wind turbine blades. The nonlinear aeroelastic model is implemented in COMSOL Multiphysics and validated with a series of benchmark calculation tests. The results show that good agreement is achieved when compared with experimental data, and its capability of handling large deflections is demonstrated. Finally the nonlinear aeroelastic model is applied to aeroelastic modelling of the parked WindPACT 1.5 MW baseline wind turbine, and reduced flapwise deflection from the nonlinear aeroelastic model is observed compared to the linear aeroelastic code FAST (Fatigue, Aerodynamics, Structures, and Turbulence). - Highlights: • A novel nonlinear aeroelastic model for wind turbine blades is developed. • The model takes account of large blade deflections and geometric nonlinearities. • The model is reliable and efficient for aeroelastic modelling of wind turbine blades. • The accuracy of the model is verified by a series of benchmark calculation tests. • The model provides more realistic aeroelastic modelling than FAST (Fatigue, Aerodynamics, Structures, and Turbulence)

  13. Kinetic modeling of thermal decomposition of zinc ferrite from neutral leach residues based on stochastic geometric model

    Energy Technology Data Exchange (ETDEWEB)

    Janković, Bojan, E-mail: bojanjan@ffh.bg.ac.rs [Faculty of Physical Chemistry, Department for Dynamics and Matter Structure, University of Belgrade, Studentski trg 12-16, P.O. Box 137, 11001 Belgrade (Serbia); Stopić, Srećko; Güven, Aybars; Friedrich, Bernd [IME Process Metallurgy and Metal Recycling, RWTH Aachen University, Aachen (Germany)

    2014-05-01

    The stochastic geometric model was applied to kinetic modeling the complex process of thermal decomposition of zinc ferrite from neutral leach residues, at different operating temperatures (600 °C, 750 °C, 950 °C and 1150 °C). Based on functional dependence of Avrami's constant (n) in a function of the effective activation energy (E{sub a}), it was found that at T>950 °C, the crystallization process takes place in autocatalytic stage, under the conditions where the rate of nucleation rapidly increases. It was established that the high nucleation rate can be attributed to formation of both Zn and Fe rich regions which provide a high number of heterogeneous nucleation sites. Based on the obtained final shape of the particles, it was found a strong presence of zinc, iron (present only in the form of Fe{sub 3}O{sub 4} (magnetite)), magnesium (in the form of Mg{sub 2}Si{sub 2}O{sub 6}), and also lead oxides. Thermodynamic analysis showed that the decomposition depends on the introduction of heat, and exerts a positive value of the Gibbs free energy of activation. Such a feature was expected since the ferrite system has been submitted to a forced decomposition and volatilization reactions. - Highlights: • Thermo-chemical investigations. • Autocatalytic stage of process, where the rate of nucleation rapidly increases. • Iron is present in the form of Fe{sub 3}O{sub 4} (magnetite). • The possibility of preparing of the nanosized magnetic particles. • Final product which underwent decomposition has the magnetic properties.

  14. Modeling and optimizing periodically inspected software rejuvenation policy based on geometric sequences

    International Nuclear Information System (INIS)

    Software aging is characterized by an increasing failure rate, progressive performance degradation and even a sudden crash in a long-running software system. Software rejuvenation is an effective method to counteract software aging. A periodically inspected rejuvenation policy for software systems is studied. The consecutive inspection intervals are assumed to be a decreasing geometric sequence, and upon the inspection times of software system and its failure features, software rejuvenation or system recovery is performed. The system availability function and cost rate function are obtained, and the optimal inspection time and rejuvenation interval are both derived to maximize system availability and minimize cost rate. Then, boundary conditions of the optimal rejuvenation policy are deduced. Finally, the numeric experiment result shows the effectiveness of the proposed policy. Further compared with the existing software rejuvenation policy, the new policy has higher system availability. - Highlights: • A periodically inspected rejuvenation policy for software systems is studied. • A decreasing geometric sequence is used to denote the consecutive inspection intervals. • The optimal inspection times and rejuvenation interval are found. • The new policy is capable of reducing average cost and improving system availability

  15. Geometric Least Square Models for Deriving [0,1]-Valued Interval Weights from Interval Fuzzy Preference Relations Based on Multiplicative Transitivity

    Directory of Open Access Journals (Sweden)

    Xuan Yang

    2015-01-01

    Full Text Available This paper presents a geometric least square framework for deriving [0,1]-valued interval weights from interval fuzzy preference relations. By analyzing the relationship among [0,1]-valued interval weights, multiplicatively consistent interval judgments, and planes, a geometric least square model is developed to derive a normalized [0,1]-valued interval weight vector from an interval fuzzy preference relation. Based on the difference ratio between two interval fuzzy preference relations, a geometric average difference ratio between one interval fuzzy preference relation and the others is defined and employed to determine the relative importance weights for individual interval fuzzy preference relations. A geometric least square based approach is further put forward for solving group decision making problems. An individual decision numerical example and a group decision making problem with the selection of enterprise resource planning software products are furnished to illustrate the effectiveness and applicability of the proposed models.

  16. A NURBS-based finite element model applied to geometrically nonlinear elastodynamics using a corotational approach

    KAUST Repository

    Espath, L. F R

    2015-02-03

    A numerical model to deal with nonlinear elastodynamics involving large rotations within the framework of the finite element based on NURBS (Non-Uniform Rational B-Spline) basis is presented. A comprehensive kinematical description using a corotational approach and an orthogonal tensor given by the exact polar decomposition is adopted. The state equation is written in terms of corotational variables according to the hypoelastic theory, relating the Jaumann derivative of the Cauchy stress to the Eulerian strain rate.The generalized-α method (Gα) method and Generalized Energy-Momentum Method with an additional parameter (GEMM+ξ) are employed in order to obtain a stable and controllable dissipative time-stepping scheme with algorithmic conservative properties for nonlinear dynamic analyses.The main contribution is to show that the energy-momentum conservation properties and numerical stability may be improved once a NURBS-based FEM in the spatial discretization is used. Also it is shown that high continuity can postpone the numerical instability when GEMM+ξ with consistent mass is employed; likewise, increasing the continuity class yields a decrease in the numerical dissipation. A parametric study is carried out in order to show the stability and energy budget in terms of several properties such as continuity class, spectral radius and lumped as well as consistent mass matrices.

  17. Effect of geometrical uncertainties on the performance of heat exchangers using an efficient POD-based model reduction technique

    Science.gov (United States)

    Abraham, S.; Ghorbaniasl, G.; Raisee, M.; Lacor, C.

    2016-06-01

    The present paper aims at assessing the effect of manufacturing tolerances on the performance of heat exchangers. To this end, a two-dimensional square rib-roughened cooling channel is considered and uncertainties are introduced along the rib profile, using a Karhunen-Loéve expansion including 20 uncertainties. In order to break the curse of dimensionality and keep the overall computational cost within acceptable limits, an efficient uncertainty quantification strategy is followed. A sensitivity analysis is first performed on a coarse grid, enabling the most important dimension to be identified and to remove the ones which have not any significant effect on the output of interest. Afterwards, an efficient Proper Orthogonal Decomposition based dimension reduction technique is implemented in order to propagate uncertainties through the CFD model. It is shown that heat transfer predictions are strongly affected by geometrical uncertainties while no significant effect was found for the pressure drop.

  18. Scaling-based forest structural change detection using an inverted geometric-optical model in the Three Gorges region of China

    NARCIS (Netherlands)

    Zeng, Y.; Schaepman, M.E.; Wu, B.; Clevers, J.G.P.W.; Bregt, A.K.

    2008-01-01

    We use the Li-Strahler geometric-optical model combined with a scaling-based approach to detect forest structural changes in the Three Gorges region of China. The physical-based Li-Strahler model can be inverted to retrieve forest structural properties. One of the main input variables for the invert

  19. Geometric model of robotic arc welding for automatic programming

    Institute of Scientific and Technical Information of China (English)

    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.

  20. Automated contouring error detection based on supervised geometric attribute distribution models for radiation therapy: A general strategy

    International Nuclear Information System (INIS)

    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

  1. Automated contouring error detection based on supervised geometric attribute distribution models for radiation therapy: A general strategy

    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

  2. Geometric filters for protein–ligand complexes based on phenomenological molecular models

    OpenAIRE

    Sudakov O. O.; Balinskyi O. M.; Platonov M. O.; Kovalskyy D. B.

    2013-01-01

    Molecular docking is a widely used method of computer-aided drug design capable of accurate prediction of protein-ligand complex conformations. However, scoring functions used to estimate free energy of binding still lack accuracy. Aim. Development of computationally simple and rapid algorithms for ranking ligands based on docking results. Methods. Computational filters utilizing geometry of protein-ligand complex were designed. Efficiency of the filters was verified in a cross-docking study ...

  3. Semi-physical Simulation of the Airborne InSAR based on Rigorous Geometric Model and Real Navigation Data

    International Nuclear Information System (INIS)

    Raw signal simulation is a useful tool for the system design, mission planning, processing algorithm testing, and inversion algorithm design of Synthetic Aperture Radar (SAR). Due to the wide and high frequent variation of aircraft's trajectory and attitude, and the low accuracy of the Position and Orientation System (POS)'s recording data, it's difficult to quantitatively study the sensitivity of the key parameters, i.e., the baseline length and inclination, absolute phase and the orientation of the antennas etc., of the airborne Interferometric SAR (InSAR) system, resulting in challenges for its applications. Furthermore, the imprecise estimation of the installation offset between the Global Positioning System (GPS), Inertial Measurement Unit (IMU) and the InSAR antennas compounds the issue. An airborne interferometric SAR (InSAR) simulation based on the rigorous geometric model and real navigation data is proposed in this paper, providing a way for quantitatively studying the key parameters and for evaluating the effect from the parameters on the applications of airborne InSAR, as photogrammetric mapping, high-resolution Digital Elevation Model (DEM) generation, and surface deformation by Differential InSAR technology, etc. The simulation can also provide reference for the optimal design of the InSAR system and the improvement of InSAR data processing technologies such as motion compensation, imaging, image co-registration, and application parameter retrieval, etc

  4. Automated segmentation method for the 3D ultrasound carotid image based on geometrically deformable model with automatic merge function

    Science.gov (United States)

    Li, Xiang; Wang, Zigang; Lu, Hongbing; Liang, Zhengrong

    2002-05-01

    Stenosis of the carotid is the most common cause of the stroke. The accurate measurement of the volume of the carotid and visualization of its shape are helpful in improving diagnosis and minimizing the variability of assessment of the carotid disease. Due to the complex anatomic structure of the carotid, it is mandatory to define the initial contours in every slice, which is very difficult and usually requires tedious manual operations. The purpose of this paper is to propose an automatic segmentation method, which automatically provides the contour of the carotid from the 3-D ultrasound image and requires minimum user interaction. In this paper, we developed the Geometrically Deformable Model (GDM) with automatic merge function. In our algorithm, only two initial contours in the topmost slice and four parameters are needed in advance. Simulated 3-D ultrasound image was used to test our algorithm. 3-D display of the carotid obtained by our algorithm showed almost identical shape with true 3-D carotid image. In addition, experimental results also demonstrated that error of the volume measurement of the carotid based on the three different initial contours is less that 1% and its speed was a very fast.

  5. Template-Based Geometric Simulation of Flexible Frameworks

    Directory of Open Access Journals (Sweden)

    Stephen A. Wells

    2012-03-01

    Full Text Available Specialised modelling and simulation methods implementing simplified physical models are valuable generators of insight. Template-based geometric simulation is a specialised method for modelling flexible framework structures made up of rigid units. We review the background, development and implementation of the method, and its applications to the study of framework materials such as zeolites and perovskites. The “flexibility window” property of zeolite frameworks is a particularly significant discovery made using geometric simulation. Software implementing geometric simulation of framework materials, “GASP”, is freely available to researchers.

  6. Invariant geometric structures on statistical models

    Czech Academy of Sciences Publication Activity Database

    Schwachhöfer, L.; Ay, N.; Jost, J.; Le, Hong-Van

    Cham: Springer, 2015 - (Nielsen, F.; Barbaresco, F.), s. 150-158. (Lecture Notes in Computer Science. 9389). ISBN 978-3-319-25039-7. [International Conference on Geometric Science of Information (GSI) 2015 /2./. Palaiseau (FR), 28.10.2015-30.10.2015] Institutional support: RVO:67985840 Keywords : geometric structures * statistical models Subject RIV: BA - General Mathematics http://link.springer.com/chapter/10.1007/978-3-319-25040-3_17

  7. Invariant geometric structures on statistical models

    Czech Academy of Sciences Publication Activity Database

    Schwachhöfer, L.; Ay, N.; Jost, J.; Le, Hong-Van

    Cham : Springer, 2015 - (Nielsen, F.; Barbaresco, F.), s. 150-158 ISBN 978-3-319-25039-7. - (Lecture Notes in Computer Science. 9389). [International Conference on Geometric Science of Information (GSI) 2015 /2./. Palaiseau (FR), 28.10.2015-30.10.2015] Institutional support: RVO:67985840 Keywords : geometric structures * statistical models Subject RIV: BA - General Mathematics http://link.springer.com/chapter/10.1007/978-3-319-25040-3_17

  8. Geometrical efficiency in computerized tomography: generalized model

    International Nuclear Information System (INIS)

    A simplified model for producing sensitivity and exposure profiles in computerized tomographic system was recently developed allowing the forecast of profiles behaviour in the rotation center of the system. The generalization of this model for some point of the image plane was described, and the geometrical efficiency could be evaluated. (C.G.C.)

  9. Geometric simplification of analysis models

    Energy Technology Data Exchange (ETDEWEB)

    Watterberg, P.A.

    1999-12-01

    Analysis programs have been having to deal with more and more complex objects as the capability to model fine detail increases. This can make them unacceptably slow. This project attempts to find heuristics for removing features from models in an automatic fashion in order to reduce polygon count. The approach is not one of theoretical completeness but rather one of trying to achieve useful results with scattered practical ideas. By removing a few simple things such as screw holes, slots, chambers, and fillets, large gains can be realized. Results varied but a reduction in the number of polygons by a factor of 10 is not unusual.

  10. The Geometrical Modelling of Fluids

    OpenAIRE

    Ivanov, Mikhail G.

    2009-01-01

    The paper considers the nonlinear electrodynamics type model and its relation with relativistic hydrodynamics with no dissipation (including string and membrane hydrodynamics). We are able to convert arbitrary flux of fluid to the family of geodesics by the conformal transformation of metric. The conditions of transformation of nonlinear electrodynamics solution to linear electrodynamics solution by changing of metric are presented.

  11. A graph spectrum based geometric biclustering algorithm.

    Science.gov (United States)

    Wang, Doris Z; Yan, Hong

    2013-01-21

    Biclustering is capable of performing simultaneous clustering on two dimensions of a data matrix and has many applications in pattern classification. For example, in microarray experiments, a subset of genes is co-expressed in a subset of conditions, and biclustering algorithms can be used to detect the coherent patterns in the data for further analysis of function. In this paper, we present a graph spectrum based geometric biclustering (GSGBC) algorithm. In the geometrical view, biclusters can be seen as different linear geometrical patterns in high dimensional spaces. Based on this, the modified Hough transform is used to find the Hough vector (HV) corresponding to sub-bicluster patterns in 2D spaces. A graph can be built regarding each HV as a node. The graph spectrum is utilized to identify the eigengroups in which the sub-biclusters are grouped naturally to produce larger biclusters. Through a comparative study, we find that the GSGBC achieves as good a result as GBC and outperforms other kinds of biclustering algorithms. Also, compared with the original geometrical biclustering algorithm, it reduces the computing time complexity significantly. We also show that biologically meaningful biclusters can be identified by our method from real microarray gene expression data. PMID:23079285

  12. 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.

  13. 3D geometric modelling of hand-woven textile

    Science.gov (United States)

    Shidanshidi, H.; Naghdy, F.; Naghdy, G.; Conroy, D. Wood

    2008-02-01

    Geometric modeling and haptic rendering of textile has attracted significant interest over the last decade. A haptic representation is created by adding the physical properties of an object to its geometric configuration. While research has been conducted into geometric modeling of fabric, current systems require time-consuming manual recognition of textile specifications and data entry. The development of a generic approach for construction of the 3D geometric model of a woven textile is pursued in this work. The geometric model would be superimposed by a haptic model in the future work. The focus at this stage is on hand-woven textile artifacts for display in museums. A fuzzy rule based algorithm is applied to the still images of the artifacts to generate the 3D model. The derived model is exported as a 3D VRML model of the textile for visual representation and haptic rendering. An overview of the approach is provided and the developed algorithm is described. The approach is validated by applying the algorithm to different textile samples and comparing the produced models with the actual structure and pattern of the samples.

  14. Geometric Models for Collaborative Search and Filtering

    OpenAIRE

    Bitton, Ephrat

    2011-01-01

    This dissertation explores the use of geometric and graphical models for a variety of information search and filtering applications. These models serve to provide an intuitive understanding of the problem domains and as well as computational efficiencies to our solution approaches. We begin by considering a search and rescue scenario where both human and automated agents share control over a fleet of unmanned aerial vehicles (UAVs) with the goal of locating a missing subject as quickly as pos...

  15. Geometric Feature Based Face-Sketch Recognition

    OpenAIRE

    Pramanik, Sourav; Bhattacharjee, Debotosh

    2013-01-01

    This paper presents a novel facial sketch image or face-sketch recognition approach based on facial feature extraction. To recognize a face-sketch, we have concentrated on a set of geometric face features like eyes, nose, eyebrows, lips, etc and their length and width ratio because it is difficult to match photos and sketches because they belong to two different modalities. In this system, first the facial features/components from training images are extracted, then ratios of length, width, a...

  16. A geometric crescent model for black hole images

    CERN Document Server

    Kamruddin, Ayman Bin

    2013-01-01

    The Event Horizon Telescope (EHT), a global very long baseline interferometry array operating at millimetre wavelengths, is spatially resolving the immediate environments of black holes for the first time. The current observations of the Galactic center black hole, Sagittarius A* (Sgr A*), and M87 have been interpreted in terms of either geometric models (e.g., a symmetric Gaussian) or detailed calculations of the appearance of black hole accretion flows. The former are not physically motivated, while the latter are subject to large systematic uncertainties. Motivated by the dominant relativistic effects of Doppler beaming and gravitational lensing in many calculations, we propose a geometric crescent model for black hole images. We show that this simple model provides an excellent statistical description of the existing EHT data of Sgr A* and M87, superior to other geometric models for Sgr A*. It also qualitatively matches physically predicted models, bridging accretion theory and observation. Based on our r...

  17. Geometrical approach to mutually unbiased bases

    International Nuclear Information System (INIS)

    We propose a unifying phase-space approach to the construction of mutually unbiased bases for a two-qubit system. It is based on an explicit classification of the geometrical structures compatible with the notion of unbiasedness. These consist of bundles of discrete curves intersecting only at the origin and satisfying certain additional properties. We also consider the feasible transformations between different kinds of curves and show that they correspond to local rotations around the Bloch-sphere principal axes. We suggest how to generalize the method to systems in dimensions that are powers of a prime

  18. Matrix models, geometric engineering and elliptic genera

    International Nuclear Information System (INIS)

    We compute the prepotential of N = 2 supersymmetric gauge theories in four dimensions obtained by toroidal compactifications of gauge theories from 6 dimensions, as a function of Kaehler and complex moduli of T2. We use three different methods to obtain this: matrix models, geometric engineering and instanton calculus. Matrix model approach involves summing up planar diagrams of an associated gauge theory on T2. Geometric engineering involves considering F-theory on elliptic threefolds, and using topological vertex to sum up worldsheet instantons. Instanton calculus involves computation of elliptic genera of instanton moduli spaces on R4. We study the compactifications of N = 2* theory in detail and establish equivalence of all these three approaches in this case. As a byproduct we geometrically engineer theories with massive adjoint fields. As one application, we show that the moduli space of mass deformed M5-branes wrapped on T2 combines the Kaehler and complex moduli of T2 and the mass parameter into the period matrix of a genus 2 curve

  19. Geometrical and physical models of abrasion

    CERN Document Server

    Domokos, G

    2013-01-01

    We extend the geometrical theory presented in [5] for collisional and frictional particle abrasion to include an independent physical equation for the evolution of mass and volume. We introduce volume weight functions as multipliers of the geometric equations and use these mutipliers to enforce physical volume evolution in the unified equations. The latter predict, in accordance with Sternberg's Law, exponential decay for volume evolution. We describe both the PDE versions, which are generalisations of Bloore's equations and their heuristic ODE approximations, called the box equations. The latter are suitable for tracking the collective abrasion of large particle populations. The mutual abrasion of identical particles, called the self-dual ows, play a key role in explaining geological scenarios. We give stability criteria for the self-dual ows in terms of the parameters of the physical volume evolution models and show that under reasonable assumptions these criteria can be met by physical systems. We also stu...

  20. The Parametric Geometric Modeling Method for Lettuce Based-template%基于模板的生菜参数化几何建模方法

    Institute of Scientific and Technical Information of China (English)

    温维亮; 郭新宇; 肖伯祥; 陆声链; 杜建军

    2011-01-01

    为了对生菜进行快速三维重构,将逆向工程的思想引入到生菜几何建模中来,提出了一种基于参数模板的生菜几何建模方法.借助三维扫描设备构造具有多分辨率的生菜器官模板,分析生菜植株形态结构特征,提取特征参数,进而通过形态参数对模板进行控制,并最终组装成为参数化的生菜几何模型.试验结果表明,该方法可以快速、便捷地重构出具有较高真实感的生菜几何模型,对曲面难以构造的植物器官及植株几何建模具有一定的参考意义.%In order to reconstruct the three-dimensional model of lettuce rapidly, the idea of reverse engineering was introduced to the lettuce geometric modeling and a template based on parameters method is proposed.Firstly, with the help of three-dimensional scanning device, multi-resolution lettuce organ template was constructed.Then, the morphological characteristics of lettuce plants were analyzed to extract characteristic parameters.Finally, parametric geometric model of lettuce plant was assembled through controlling the morphological parametric and the templates.The results showed that this method could reconstruct high realistic geometric model of lettuce quickly and easily, and have reference value for complicated structure plants.

  1. Multiscale geometric modeling of macromolecules I: Cartesian representation

    Science.gov (United States)

    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

  2. Multiscale geometric modeling of macromolecules I: Cartesian representation

    International Nuclear Information System (INIS)

    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

  3. A Dugdale model based geometrical amplifier enables the measurement of separation-to-failure for a cohesive interface

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Regardless of all kinds of different formulae used for the traction-separation relationship in cohesive zone modeling,the peak tractionσ_m and the separation-to-failureδ_0(or equivalently the work-to-separationΓ) are the primary parameters which control the interfacial fracture behaviors. Experimentally,it is hard to determine those quantities,especially forδ_0,which occurs in a very localized region with possibly complicated geometries by material failure.Based on the Dugdale model,we show that the sepa...

  4. [Retrieval of crown closure of moso bamboo forest using unmanned aerial vehicle (UAV) remotely sensed imagery based on geometric-optical model].

    Science.gov (United States)

    Wang, Cong; Du, Hua-qiang; Zhou, Guo-mo; Xu, Xiao-jun; Sun, Shao-bo; Gao, Guo-long

    2015-05-01

    This research focused on the application of remotely sensed imagery from unmanned aerial vehicle (UAV) with high spatial resolution for the estimation of crown closure of moso bamboo forest based on the geometric-optical model, and analyzed the influence of unconstrained and fully constrained linear spectral mixture analysis (SMA) on the accuracy of the estimated results. The results demonstrated that the combination of UAV remotely sensed imagery and geometric-optical model could, to some degrees, achieve the estimation of crown closure. However, the different SMA methods led to significant differentiation in the estimation accuracy. Compared with unconstrained SMA, the fully constrained linear SMA method resulted in higher accuracy of the estimated values, with the coefficient of determination (R2) of 0.63 at 0.01 level, against the measured values acquired during the field survey. Root mean square error (RMSE) of approximate 0.04 was low, indicating that the usage of fully constrained linear SMA could bring about better results in crown closure estimation, which was closer to the actual condition in moso bamboo forest. PMID:26571671

  5. A cubic B-spline-based hybrid registration of lung CT images for a dynamic airway geometric model with large deformation

    International Nuclear Information System (INIS)

    The goal of this study is to develop a matching algorithm that can handle large geometric changes in x-ray computed tomography (CT)-derived lung geometry occurring during deep breath maneuvers. These geometric relationships are further utilized to build a dynamic lung airway model for computational fluid dynamics (CFD) studies of pulmonary air flow. The proposed algorithm is based on a cubic B-spline-based hybrid registration framework that incorporates anatomic landmark information with intensity patterns. A sequence of invertible B-splines is composed in a multiresolution framework to ensure local invertibility of the large deformation transformation and a physiologically meaningful similarity measure is adopted to compensate for changes in voxel intensity due to inflation. Registrations are performed using the proposed approach to match six pairs of 3D CT human lung datasets. Results show that the proposed approach has the ability to match the intensity pattern and the anatomical landmarks, and ensure local invertibility for large deformation transformations. Statistical results also show that the proposed hybrid approach yields significantly improved results as compared with approaches using either landmarks or intensity alone.

  6. A cubic B-spline-based hybrid registration of lung CT images for a dynamic airway geometric model with large deformation

    Energy Technology Data Exchange (ETDEWEB)

    Yin Youbing; Lin, Ching-Long [Department of Mechanical and Industrial Engineering, University of Iowa, Iowa City, IA 52242 (United States); Hoffman, Eric A [Department of Radiology, University of Iowa, Iowa City, IA 52242 (United States); Ding Kai; Reinhardt, Joseph M, E-mail: ching-long-lin@uiowa.edu [Department of Biomedical Engineering, University of Iowa, Iowa City, IA 52242 (United States)

    2011-01-07

    The goal of this study is to develop a matching algorithm that can handle large geometric changes in x-ray computed tomography (CT)-derived lung geometry occurring during deep breath maneuvers. These geometric relationships are further utilized to build a dynamic lung airway model for computational fluid dynamics (CFD) studies of pulmonary air flow. The proposed algorithm is based on a cubic B-spline-based hybrid registration framework that incorporates anatomic landmark information with intensity patterns. A sequence of invertible B-splines is composed in a multiresolution framework to ensure local invertibility of the large deformation transformation and a physiologically meaningful similarity measure is adopted to compensate for changes in voxel intensity due to inflation. Registrations are performed using the proposed approach to match six pairs of 3D CT human lung datasets. Results show that the proposed approach has the ability to match the intensity pattern and the anatomical landmarks, and ensure local invertibility for large deformation transformations. Statistical results also show that the proposed hybrid approach yields significantly improved results as compared with approaches using either landmarks or intensity alone.

  7. Facial symmetry assessment based on geometric features

    Science.gov (United States)

    Xu, Guoping; Cao, Hanqiang

    2015-12-01

    Face image symmetry is an important factor affecting the accuracy of automatic face recognition. Selecting high symmetrical face image could improve the performance of the recognition. In this paper, we proposed a novel facial symmetry evaluation scheme based on geometric features, including centroid, singular value, in-plane rotation angle of face and the structural similarity index (SSIM). First, we calculate the value of the four features according to the corresponding formula. Then, we use fuzzy logic algorithm to integrate the value of the four features into a single number which represents the facial symmetry. The proposed method is efficient and can adapt to different recognition methods. Experimental results demonstrate its effectiveness in improving the robustness of face detection and recognition.

  8. Geometrical model of the Baltic artesian basin

    Science.gov (United States)

    Sennikovs, J.; Virbulis, J.; Bethers, U.

    2012-04-01

    Baltic artesian basin (BAB) is a multi-layer sedimentary basin spanning around 480'000 km2. BAB is located in the territory of Latvia, Lithuania and Estonia, parts of Poland, Russia, Belarus and large area of the Baltic Sea, including island of Gotland. The thickness of sedimentary cover is about 5000 m in the south-western part. Crystalline bedding reaches the surface in the northern and north-western parts. The aim of the present work is development of the model of geometric structure and three dimensional finite element mesh for the hydrogeological model of the whole BAB. The information that is used to build the geometrical structure includes: (1) Stratigraphic information from boreholes in Latvia and Estonia (2) Maps of height isolines of geological layers for Latvia and Lithuania (3) Maps of sub-quaternary deposits in Latvia and Lithuania (4) Maps of fault lines on the crystalline basement surface in Latvia, Lithuania and Estonia (5) Buried valley data from Latvia and Estonia (6) Earth topography data (7) Baltic sea depth data (8) Data from published geological cross-sections, information from books and other sources. Unification of the heterogeneous information from different sources, which are employed for building of the geometrical structure of the model are performed. Special algorithms are developed for this purpose considering the priority, importance and plausibility of each of the data sources. Pre-processing of the borehole information to screen out the outlying borehole data has been performed. Model of geological structure contains 42 layers. It includes aquifers and aquitards from Cambrian up to the Quaternary deposits. Fault displacements are incorporated into the model taking into account data from the published structural maps. Four reconstructed regional erosion surfaces (upper Ordovician, Devonian, Permian and Quaternary) are included into the model Three dimensional mesh of the geological structure is constructed layer-wise. The triangular

  9. The geometric Schwinger model on the lattice

    International Nuclear Information System (INIS)

    The geometric Schwinger model has an interesting non-perturbative structure related to topological index theorems. This is analyzed on the euclidean lattice with staggered fermions. Using the hybrid Monte Carlo simulation we calculate the exponential decay of the field strength correlation and the screening of the heavy quark potential including finite volume effects. For both cases the transition from strong to weak coupling behaviour is studied. These calculations are complemented by an unquenched strong coupling expansion. Furthermore, we characterize fermion bilinears by their lattice symmetry properties. The Monte Carlo results on their correlation functions can then be discussed under the aspects of the anomalous U(1)A symmetry breaking. The toron part of the effective action is measured too. (orig.)

  10. A geometric crescent model for black hole images

    Science.gov (United States)

    Kamruddin, Ayman Bin; Dexter, Jason

    2013-09-01

    The Event Horizon Telescope (EHT), a global very long baseline interferometry array operating at millimetre wavelengths, is spatially resolving the immediate environments of black holes for the first time. The current observations of the Galactic centre black hole, Sagittarius A* (Sgr A*), and M87 have been interpreted in terms of either geometric models (e.g. a symmetric Gaussian) or detailed calculations of the appearance of black hole accretion flows. The former are not physically motivated, while the latter are subject to large systematic uncertainties. Motivated by the dominant relativistic effects of Doppler beaming and gravitational lensing in many calculations, we propose a geometric crescent model for black hole images. We show that this simple model provides an excellent statistical description of the existing EHT data of Sgr A* and M87, superior to other geometric models for Sgr A*. It also qualitatively matches physically predicted models, bridging accretion theory and observation. Based on our results, we make predictions for the detectability of the black hole shadow, a signature of strong gravity, in future observations.

  11. Forward error correction based on algebraic-geometric theory

    CERN Document Server

    A Alzubi, Jafar; M Chen, Thomas

    2014-01-01

    This book covers the design, construction, and implementation of algebraic-geometric codes from Hermitian curves. Matlab simulations of algebraic-geometric codes and Reed-Solomon codes compare their bit error rate using different modulation schemes over additive white Gaussian noise channel model. Simulation results of Algebraic-geometric codes bit error rate performance using quadrature amplitude modulation (16QAM and 64QAM) are presented for the first time and shown to outperform Reed-Solomon codes at various code rates and channel models. The book proposes algebraic-geometric block turbo codes. It also presents simulation results that show an improved bit error rate performance at the cost of high system complexity due to using algebraic-geometric codes and Chase-Pyndiah’s algorithm simultaneously. The book proposes algebraic-geometric irregular block turbo codes (AG-IBTC) to reduce system complexity. Simulation results for AG-IBTCs are presented for the first time.

  12. Geometric modeling for computer aided design

    Science.gov (United States)

    Schwing, James L.; Olariu, Stephen

    1995-01-01

    The primary goal of this grant has been the design and implementation of software to be used in the conceptual design of aerospace vehicles particularly focused on the elements of geometric design, graphical user interfaces, and the interaction of the multitude of software typically used in this engineering environment. This has resulted in the development of several analysis packages and design studies. These include two major software systems currently used in the conceptual level design of aerospace vehicles. These tools are SMART, the Solid Modeling Aerospace Research Tool, and EASIE, the Environment for Software Integration and Execution. Additional software tools were designed and implemented to address the needs of the engineer working in the conceptual design environment. SMART provides conceptual designers with a rapid prototyping capability and several engineering analysis capabilities. In addition, SMART has a carefully engineered user interface that makes it easy to learn and use. Finally, a number of specialty characteristics have been built into SMART which allow it to be used efficiently as a front end geometry processor for other analysis packages. EASIE provides a set of interactive utilities that simplify the task of building and executing computer aided design systems consisting of diverse, stand-alone, analysis codes. Resulting in a streamlining of the exchange of data between programs reducing errors and improving the efficiency. EASIE provides both a methodology and a collection of software tools to ease the task of coordinating engineering design and analysis codes.

  13. Lunar-based Earth observation geometrical characteristics research

    Science.gov (United States)

    Ren, Yuanzhen; Liu, Guang; Ye, Hanlin; Guo, Huadong; Ding, Yixing; Chen, Zhaoning

    2016-07-01

    As is known to all, there are various platforms for carrying sensors to observe Earth, such as automobiles, aircrafts and satellites. Nowadays, we focus on a new platform, Moon, because of its longevity, stability and vast space. These advantages make it to be the next potential platform for observing Earth, enabling us to get the consistent and global measurements. In order to get a better understanding of lunar-based Earth observation, we discuss its geometrical characteristics. At present, there are no sensors on the Moon for observing Earth and we are not able to obtain a series of real experiment data. As a result, theoretical modeling and numerical calculation are used in this paper. At first, we construct an approximate geometrical model of lunar-based Earth observation, which assumes that Earth and Moon are spheres. Next, we calculate the position of Sun, Earth and Moon based on the JPL ephemeris. With the help of positions data and geometrical model, it is possible for us to decide the location of terminator and substellar points. However, in order to determine their precise position in the conventional terrestrial coordinate system, reference frames transformations are introduced as well. Besides, taking advantages of the relative positions of Sun, Earth and Moon, we get the total coverage of lunar-based Earth optical observation. Furthermore, we calculate a more precise coverage, considering placing sensors on different positions of Moon, which is influenced by its attitude parameters. In addition, different ephemeris data are compared in our research and little difference is found.

  14. Geometric Bessel models for GSp_4 and multiplicity one

    OpenAIRE

    Lysenko, Sergey

    2004-01-01

    I this paper, which is a sequel to math.AG/0310361, we study Bessel models of representations of GSp_4 over a local non archimedian field in the framework of the geometric Langlands program. The Bessel module over the nonramified Hecke algebra of GSp_4 admits a geometric counterpart, the Bessel category of perverse sheaves on some ind-algebraic stack. We use it to prove a geometric version of the multiplicity one for Bessel models. It implies a geometric Casselman-Shalika type formula for the...

  15. 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.

  16. GEOMETRICALLY INVARIANT WATERMARKING BASED ON RADON TRANSFORMATION

    Institute of Scientific and Technical Information of China (English)

    Cai Lian; Du Sidan; Gao Duntang

    2005-01-01

    The weakness of classical watermarking methods is the vulnerability to geometrical distortions that widely occur during normal use of the media. In this letter, a new imagewatermarking method is presented to resist Rotation, Scale and Translation (RST) attacks. The watermark is embedded into a domain obtained by taking Radon transform of a circular area selected from the original image, and then extracting Two-Dimensional (2-D) Fourier magnitude of the Radon transformed image. Furthermore, to prevent the watermarked image from degrading due to inverse Radon transform, watermark signal is inversely Radon transformed individually.Experimental results demonstrate that the proposed scheme is able to withstand a variety of attacks including common geometric attacks.

  17. Approach to Weighted Geometric Evaluation Based on Projection Pursuit

    Institute of Scientific and Technical Information of China (English)

    Yang Shanlin; Wang Shuo; Gong Daning

    2006-01-01

    Weighted geometric evaluation approach based on Projection pursuit (PP) model is presented in this paper to optimize the choice of schemes. By using PP model, the multi-dimension evaluation index values of schemes can be synthesized into projection value with one dimension. The scheme with a bigger projection value is much better, so the schemes sample can be an optimized choice according to the projection value of each scheme. The modeling of PP based on accelerating genetic algorithm can predigest the realized process of projection pursuit technique, can overcome the shortcomings of large computation amount and the difficulty of computer programming in traditional projection pursuit methods, and can give a new method for application of projection pursuit technique to optimize choice of schemes by using weighted geometric evaluation. The analysis of an applied sample shows that applying PP model driven directly by samples data to optimize choice of schemes is both simple and feasible, that its projection values are relatively decentralized and profit decision-making, that its applicability and maneuverability are high. It can avoid the shortcoming of subjective weighing method, and its results are scientific and objective.

  18. Iris-based medical analysis by geometric deformation features.

    Science.gov (United States)

    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. PMID:23144041

  19. Geometría computacional y bases de datos

    OpenAIRE

    Dorzán, María Gisela; Esquivel, Susana Cecilia; Gagliardi, Edilma Olinda; Palmero, Pablo Rafael; Taranilla, María Teresa

    2016-01-01

    La línea de investigación “Geometría Computacional y Bases de Datos” enmarcada en el proyecto “Tecnologías Avanzadas de Bases de Datos” vincula el estudio de las disciplinas Bases de Datos, Geometría Computacional y Metaheurísticas, utilizando los métodos y las herramientas provistas para la resolución de problemas orientados a optimización.

  20. Implementation of geometrically exact beam element for nonlinear dynamics modeling

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jielong, E-mail: jelon.wang@gmail.com [Commercial Aircraft Corporation of China, Ltd., Beijing Aeronautical Science & Technology Research Institute (China)

    2015-12-15

    The paper develops a new type of geometrically exact beam element featuring large displacements and rotations together with small warping. The dimension reduction approach based on variational asymptotic method has been explored, and a linear two-dimensional finite element procedure has been implemented to predict the cross-sectional stiffness and recover the cross-sectional strain fields of the beam. The total and incremental variables mixed formula of governing equations of motion is presented, in which the Wiener–Milenković parameters are selected to vectorize the finite rotation. The dynamic problem of geometrically exact beam has been solved by the implicit Radau IIA algorithms, the time histories of large translations and rotations with small three-dimensional warping have been integrated. Numerical simulations have been performed and the results have been compared to those of commercial software LS-DYNA. It can be concluded that the current modeling approach features high accuracy and that the new geometrically exact beam with warping is robust enough to predict large deformations with small strain.

  1. Implementation of geometrically exact beam element for nonlinear dynamics modeling

    International Nuclear Information System (INIS)

    The paper develops a new type of geometrically exact beam element featuring large displacements and rotations together with small warping. The dimension reduction approach based on variational asymptotic method has been explored, and a linear two-dimensional finite element procedure has been implemented to predict the cross-sectional stiffness and recover the cross-sectional strain fields of the beam. The total and incremental variables mixed formula of governing equations of motion is presented, in which the Wiener–Milenković parameters are selected to vectorize the finite rotation. The dynamic problem of geometrically exact beam has been solved by the implicit Radau IIA algorithms, the time histories of large translations and rotations with small three-dimensional warping have been integrated. Numerical simulations have been performed and the results have been compared to those of commercial software LS-DYNA. It can be concluded that the current modeling approach features high accuracy and that the new geometrically exact beam with warping is robust enough to predict large deformations with small strain

  2. GEOMETRIC MODEL OF THE NAZCA PLATE SUBDUCTION IN SOUTHWEST COLOMBIA

    OpenAIRE

    Monsalve J Hugo; Pedraza Garcia Patricia; Vargas Carlos Alberto

    2007-01-01

    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. Geologi...

  3. Methodology for geometric modelling. Presentation and administration of site descriptive models

    International Nuclear Information System (INIS)

    This report presents a methodology to construct, visualise and present geoscientific descriptive models based on data from the site investigations, which the SKB currently performs, to build an underground nuclear waste disposal facility in Sweden. It is designed for interaction with SICADA (SKB:s site characterisation database) and RVS (SKB:s Rock Visualisation System). However, the concepts of the methodology are general and can be used with other tools capable of handling 3D geometries and parameters. The descriptive model is intended to be an instrument where site investigation data from all disciplines are put together to form a comprehensive visual interpretation of the studied rock mass. The methodology has four main components: 1. Construction of a geometrical model of the interpreted main structures at the site. 2. Description of the geoscientific characteristics of the structures. 3. Description and geometrical implementation of the geometric uncertainties in the interpreted model structures. 4. Quality system for the handling of the geometrical model, its associated database and some aspects of the technical auditing. The geometrical model forms a basis for understanding the main elements and structures of the investigated site. Once the interpreted geometries are in place in the model, the system allows for adding descriptive and quantitative data to each modelled object through a system of intuitive menus. The associated database allows each geometrical object a complete quantitative description of all geoscientific disciplines, variabilities, uncertainties in interpretation and full version history. The complete geometrical model and its associated database of object descriptions are to be recorded in a central quality system. Official, new and old versions of the model are administered centrally in order to have complete quality assurance of each step in the interpretation process. The descriptive model is a cornerstone in the understanding of the

  4. 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.

  5. Point- and curve-based geometric conflation

    KAUST Repository

    López-Vázquez, C.

    2013-01-01

    Geometric conflation is the process undertaken to modify the coordinates of features in dataset A in order to match corresponding ones in dataset B. The overwhelming majority of the literature considers the use of points as features to define the transformation. In this article we present a procedure to consider one-dimensional curves also, which are commonly available as Global Navigation Satellite System (GNSS) tracks, routes, coastlines, and so on, in order to define the estimate of the displacements to be applied to each object in A. The procedure involves three steps, including the partial matching of corresponding curves, the computation of some analytical expression, and the addition of a correction term in order to satisfy basic cartographic rules. A numerical example is presented. © 2013 Copyright Taylor and Francis Group, LLC.

  6. Prediction on the viscosity of multi-component melts with a new geometric model

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A geometric model for calculating the viscosity of multi-component melt from related binary physicochemistry properties was derived based on Chou's thermodynamic geometric model. The model derived was employed to predict the viscosity of Au-Ag-Cu alloys. The results show that the calculated viscosity for Au-Ag-Cu alloys meet the experimental data very well. In addition, the viscosity of Bi-Sn-In systems was also predicted with this model.

  7. Modelling the mass of kiwi fruit by geometrical attributes

    Directory of Open Access Journals (Sweden)

    A. Tabatabaeefar

    2006-06-01

    Full Text Available The determination of mathematical models for predicting the mass of kiwi fruits from their dimensions and projected areas was done. The research was conducted on 200 observations of two Iranian varieties of kiwi fruit (Abbott and Hayward. The physical characteristics measured included mass, volume, dimensions and projected areas perpendicular to major diameters. Maximum, mean, minimum values, standard deviation, coefficient of variation, bulk density (BD, geometric mean diameter (GM, and percent sphericity (SPH of all of the parameters were determined. Models were divided into three classifications: 1 – single and multiple variable regression models of kiwi fruit dimensions (dimension models, 2 – single and multiple variable regression models of projected areas (projected area models, 3 – estimation of kiwi fruit shape, ellipsoid or spheroid based on volume (models based on volume. Among single variable models, 1st classification, second diameter model of kiwi fruit had maximum coefficient of determination, R2 = 0.78 for all observations. Among the second classification, mass models of projected areas had a nonlinear relationship with R2 = 0.97. Third classification models had the highest performance followed by the second classification and, respectively, the first, with R2 approaching unity.

  8. Multipartite geometric entanglement in finite size XY model

    International Nuclear Information System (INIS)

    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.

  9. 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.

  10. A geometric deformable model for echocardiographic image segmentation

    Science.gov (United States)

    Hang, X.; Greenberg, N. L.; Thomas, J. D.

    2002-01-01

    Gradient vector flow (GVF), an elegant external force for parametric deformable models, can capture object boundaries from both sides. A new geometric deformable model is proposed that combines GVF and the geodesic active contour model. The level set method is used as the numerical method of this model. The model is applied for echocardiographic image segmentation.

  11. Geometric Distortion Analysis Using CAD/CAM Based Manufacturing Simulation

    OpenAIRE

    Werke, Mats; Hedlind, Mikael; Nicolescu, Mihai

    2014-01-01

    Machining of components may cause geometric distortions and thereby quality issues and increased costs. This paper presents an engineering approach of CAD/CAM based manufacturing simulation in order to be in control of geometric distortions after machining. The method utilises STEP AP209 for communication of CAD/CAM simulation data. The method improves the ability to optimise process parameters, geometry, and material, in order to fulfil the design requirements. The method supports concurrent...

  12. Multiscale geometric modeling of macromolecules II: Lagrangian representation.

    Science.gov (United States)

    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. PMID:23813599

  13. An empirical model for pp scattering and geometrical scaling

    International Nuclear Information System (INIS)

    We present the result of an empirical model for elastic pp scattering at LHC which indicates that the asymptotic black disk limit R = σelastic/σtotal → 1/2 is not yet reached and discuss the implications on classical geometrical scaling behavior. We propose a geometrical scaling law for the position of the dip in elastic pp scattering which allows to make predictions valid both for intermediate and asymptotic energies.

  14. 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.

  15. Geometrically Invariant Watermarking Scheme Based on Local Feature Points

    Directory of Open Access Journals (Sweden)

    Jing Li

    2012-06-01

    Full Text Available Based on local invariant feature points and cross ratio principle, this paper presents a feature-point-based image watermarking scheme. It is robust to geometric attacks and some signal processes. It extracts local invariant feature points from the image using the improved scale invariant feature transform algorithm. Utilizing these points as vertexes it constructs some quadrilaterals to be as local feature regions. Watermark is inserted these local feature regions repeatedly. In order to get stable local regions it adjusts the number and distribution of extracted feature points. In every chosen local feature region it decides locations to embed watermark bits based on the cross ratio of four collinear points, the cross ratio is invariant to projective transformation. Watermark bits are embedded by quantization modulation, in which the quantization step value is computed with the given PSNR. Experimental results show that the proposed method can strongly fight more geometrical attacks and the compound attacks of geometrical ones.

  16. Ear Biometrics Based on Geometrical Feature Extraction

    OpenAIRE

    Choraś, Micha

    2005-01-01

    Biometrics identification methods proved to be very efficient, more natural and easy for users than traditional methods of human identification. In fact, only biometrics methods truly identify humans, not keys and cards they posses or passwords they should remember. The future of biometrics will surely lead to systems based on image analysis as the data acquisition is very simple and requires only cameras, scanners or sensors. More importantly such methods could be passive, which means that t...

  17. Geometrical aspects of solvable two dimensional models

    International Nuclear Information System (INIS)

    It was noted that there is a connection between the non-linear two-dimensional (2D) models and the scalar curvature r, i.e., when r = -2 the equations of motion of the Liouville and sine-Gordon models were obtained. Further, solutions of various classical nonlinear 2D models can be obtained from the condition that the appropriate curvature two form Ω = 0, which suggests that these models are closely related. This relation is explored further in the classical version by obtaining the equations of motion from the evolution equations, the infinite number of conserved quantities, and the common central charge. The Poisson brackets of the solvable 2D models are specified by the Virasoro algebra. 21 refs

  18. 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.

  19. Investigation of New Microstrip Bandpass Filter Based on Patch Resonator with Geometrical Fractal Slot

    OpenAIRE

    Mezaal, Yaqeen S.; Eyyuboglu, Halil T.

    2016-01-01

    A compact dual-mode microstrip bandpass filter using geometrical slot is presented in this paper. The adopted geometrical slot is based on first iteration of Cantor square fractal curve. This filter has the benefits of possessing narrower and sharper frequency responses as compared to microstrip filters that use single mode resonators and traditional dual-mode square patch resonators. The filter has been modeled and demonstrated by Microwave Office EM simulator designed at a resonant frequenc...

  20. Methods for Geometric Data Validation of 3d City Models

    Science.gov (United States)

    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

  1. A Geometrical Transformations Resistant Digital Watermarking Based on Quantization

    Institute of Scientific and Technical Information of China (English)

    SHI Lei; HONG Fan; LIU Wei-qun; HU Yu-ping; CHEN Zhuo

    2005-01-01

    A geometrical transformations resistant digital image watermarking based on quantization is described. Taking advantage of the rotation, scale and translation invariants of discrete Fourier transform(DFT), each watermark bit is embedded into each homocentric circles around the zero frequency term in DFT domain by quantizing the magnitude vector of Fourier spectrum. The embedded sequence can be extracted by "majority principles" without restoring to the original unmarked image. The experimental results show that the watermark is invisible and robust to any combination of geometrical transformations or common image processing techniques.

  2. Geometric Models for Secondary Structures in Proteins

    OpenAIRE

    Toda, Magdalena; Athukorallage, Bhagya

    2015-01-01

    This research is motivated by a study of special types of surfaces of revolution, using methods from differential geometry, elasticity theory and variational calculus. In particular, we present an elastic membrane model for the beta barrels in protein biology, via a certain {\\em Generalized Willmore type} energy functional. We study the corresponding Euler--Lagrange equation, as well as a specific boundary value problem whose solutions are {\\em Generalized Willmore surfaces of revolution}. We...

  3. Hidden geometrical structures in integrable models

    OpenAIRE

    Dorey, Patrick

    1992-01-01

    The bootstrap equations for the ADE series of purely elastic scattering theories have turned out to be intimately connected with the geometry of root systems and the Coxeter element. An informal review of some of this material is given, mentioning also a couple of other contexts -- the Pasquier models, and the simply-laced affine Toda field theories -- where similar structures are encountered. The relevance of twisted Coxeter elements is indicated, and a construction of these elements inspire...

  4. 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.

  5. The synthetical application based on the geometric distributed lag model%基于几何分布滞后模型消费与收入的综合应用

    Institute of Scientific and Technical Information of China (English)

    沈卉卉

    2011-01-01

    This paper is discussed the adaptive anticipation model and the partial adjustment model based on the geometric distributed lag model. Whereas their different premises that the models are educed the economic hypothesis,and results in the difference of the resid framework. They bring the difference on the estimation of the models, we construct the synthetical model of the partial adjustment and the adaptive anticipation. Using the synthetical model's estimation advantage overcome the impact on the first-order auto-pertinence when we directly estimate the geometric distributed lag model.%在几何分布滞后模型的基础之上,讨论了自适应预期模型和局部调整模型,鉴于它们各自导出模型的经济假设前提不同,导致随机误差项的结构有所不同,从而给模型的估计带来一定的不同.通过建立一个局部调整-自适应预期综合模型,利用它估计模型的优势,克服了几何分布滞后模型直接估计所带来的一阶自相关性的影响.

  6. Do Lumped-Parameter Models Provide the Correct Geometrical Damping?

    DEFF Research Database (Denmark)

    Andersen, Lars

    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....

  7. Diquark Structure in Heavy Quark Baryons in a Geometric Model

    OpenAIRE

    Paria, Lina; Abbas, Afsar

    1996-01-01

    Using a geometric model for the study of the structure of hadrons, we study baryons having one, two and three heavy quarks. The study reveals diquark structure in baryons with one and two heavy quarks but not with three heavy identical quarks.

  8. Geometric Aspects of Force Controllability for a Swimming Model

    International Nuclear Information System (INIS)

    We study controllability properties (swimming capabilities) of a mathematical model of an abstract object which 'swims' in the 2-D Stokes fluid. Our goal is to investigate how the geometric shape of this object affects the forces acting upon it. Such problems are of interest in biology and engineering applications dealing with propulsion systems in fluids

  9. 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.

  10. Comparison and Analysis of Geometric Correction Models of Spaceborne SAR.

    Science.gov (United States)

    Jiang, Weihao; Yu, Anxi; Dong, Zhen; Wang, Qingsong

    2016-01-01

    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. PMID:27347973

  11. Geometric Quality Assessment of LIDAR Data Based on Swath Overlap

    Science.gov (United States)

    Sampath, A.; Heidemann, H. K.; Stensaas, G. L.

    2016-06-01

    This paper provides guidelines on quantifying the relative horizontal and vertical errors observed between conjugate features in the overlapping regions of lidar data. The quantification of these errors is important because their presence quantifies the geometric quality of the data. A data set can be said to have good geometric quality if measurements of identical features, regardless of their position or orientation, yield identical results. Good geometric quality indicates that the data are produced using sensor models that are working as they are mathematically designed, and data acquisition processes are not introducing any unforeseen distortion in the data. High geometric quality also leads to high geolocation accuracy of the data when the data acquisition process includes coupling the sensor with geopositioning systems. Current specifications (e.g. Heidemann 2014) do not provide adequate means to quantitatively measure these errors, even though they are required to be reported. Current accuracy measurement and reporting practices followed in the industry and as recommended by data specification documents also potentially underestimate the inter-swath errors, including the presence of systematic errors in lidar data. Hence they pose a risk to the user in terms of data acceptance (i.e. a higher potential for Type II error indicating risk of accepting potentially unsuitable data). For example, if the overlap area is too small or if the sampled locations are close to the center of overlap, or if the errors are sampled in flat regions when there are residual pitch errors in the data, the resultant Root Mean Square Differences (RMSD) can still be small. To avoid this, the following are suggested to be used as criteria for defining the inter-swath quality of data: a) Median Discrepancy Angle b) Mean and RMSD of Horizontal Errors using DQM measured on sloping surfaces c) RMSD for sampled locations from flat areas (defined as areas with less than 5 degrees of slope

  12. Modeling of eddy current sensor using geometric and electromagnetic data

    International Nuclear Information System (INIS)

    In this paper a new modeling method for an eddy current sensor is presented using geometric and electromagnetic data of a sensor and a measuring target It can predict not only sensor output but also medium behavior related to sensor output. The geometric data of a sensor coil and the eddy current generated on a measuring target are simplified to an array of circular loops. And to perform computations of the network circuit between sensor coil loops and eddy current loops using the geometric and electromagnetic data in order to consider all possible interactions, the equivalent network circuit of eddy current sensor's behavior has been drawn. Because the sensor's initial value, medium behavior, and final value can be shown quantitatively by the proposed modeling method as the geometric and electromagnetic data varies, it can precisely predict the sensor output depending on the measuring goal and application field. Thus the model can be utilized to improve accuracy, eliminate the need for calibration before use, and produce the best design for any given purpose

  13. Evaluating conducting network based transparent electrodes from geometrical considerations

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Ankush [Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, 560064 Bangalore (India); Kulkarni, G. U., E-mail: guk@cens.res.in [Centre for Nano and Soft Matter Sciences, 560013 Bangalore (India)

    2016-01-07

    Conducting nanowire networks have been developed as viable alternative to existing indium tin oxide based transparent electrode (TE). The nature of electrical conduction and process optimization for electrodes have gained much from the theoretical models based on percolation transport using Monte Carlo approach and applying Kirchhoff's law on individual junctions and loops. While most of the literature work pertaining to theoretical analysis is focussed on networks obtained from conducting rods (mostly considering only junction resistance), hardly any attention has been paid to those made using template based methods, wherein the structure of network is neither similar to network obtained from conducting rods nor similar to well periodic geometry. Here, we have attempted an analytical treatment based on geometrical arguments and applied image analysis on practical networks to gain deeper insight into conducting networked structure particularly in relation to sheet resistance and transmittance. Many literature examples reporting networks with straight or curvilinear wires with distributions in wire width and length have been analysed by treating the networks as two dimensional graphs and evaluating the sheet resistance based on wire density and wire width. The sheet resistance values from our analysis compare well with the experimental values. Our analysis on various examples has revealed that low sheet resistance is achieved with high wire density and compactness with straight rather than curvilinear wires and with narrower wire width distribution. Similarly, higher transmittance for given sheet resistance is possible with narrower wire width but of higher thickness, minimal curvilinearity, and maximum connectivity. For the purpose of evaluating active fraction of the network, the algorithm was made to distinguish and quantify current carrying backbone regions as against regions containing only dangling or isolated wires. The treatment can be helpful in

  14. Evaluating conducting network based transparent electrodes from geometrical considerations

    International Nuclear Information System (INIS)

    Conducting nanowire networks have been developed as viable alternative to existing indium tin oxide based transparent electrode (TE). The nature of electrical conduction and process optimization for electrodes have gained much from the theoretical models based on percolation transport using Monte Carlo approach and applying Kirchhoff's law on individual junctions and loops. While most of the literature work pertaining to theoretical analysis is focussed on networks obtained from conducting rods (mostly considering only junction resistance), hardly any attention has been paid to those made using template based methods, wherein the structure of network is neither similar to network obtained from conducting rods nor similar to well periodic geometry. Here, we have attempted an analytical treatment based on geometrical arguments and applied image analysis on practical networks to gain deeper insight into conducting networked structure particularly in relation to sheet resistance and transmittance. Many literature examples reporting networks with straight or curvilinear wires with distributions in wire width and length have been analysed by treating the networks as two dimensional graphs and evaluating the sheet resistance based on wire density and wire width. The sheet resistance values from our analysis compare well with the experimental values. Our analysis on various examples has revealed that low sheet resistance is achieved with high wire density and compactness with straight rather than curvilinear wires and with narrower wire width distribution. Similarly, higher transmittance for given sheet resistance is possible with narrower wire width but of higher thickness, minimal curvilinearity, and maximum connectivity. For the purpose of evaluating active fraction of the network, the algorithm was made to distinguish and quantify current carrying backbone regions as against regions containing only dangling or isolated wires. The treatment can be helpful in

  15. Evaluating conducting network based transparent electrodes from geometrical considerations

    Science.gov (United States)

    Kumar, Ankush; Kulkarni, G. U.

    2016-01-01

    Conducting nanowire networks have been developed as viable alternative to existing indium tin oxide based transparent electrode (TE). The nature of electrical conduction and process optimization for electrodes have gained much from the theoretical models based on percolation transport using Monte Carlo approach and applying Kirchhoff's law on individual junctions and loops. While most of the literature work pertaining to theoretical analysis is focussed on networks obtained from conducting rods (mostly considering only junction resistance), hardly any attention has been paid to those made using template based methods, wherein the structure of network is neither similar to network obtained from conducting rods nor similar to well periodic geometry. Here, we have attempted an analytical treatment based on geometrical arguments and applied image analysis on practical networks to gain deeper insight into conducting networked structure particularly in relation to sheet resistance and transmittance. Many literature examples reporting networks with straight or curvilinear wires with distributions in wire width and length have been analysed by treating the networks as two dimensional graphs and evaluating the sheet resistance based on wire density and wire width. The sheet resistance values from our analysis compare well with the experimental values. Our analysis on various examples has revealed that low sheet resistance is achieved with high wire density and compactness with straight rather than curvilinear wires and with narrower wire width distribution. Similarly, higher transmittance for given sheet resistance is possible with narrower wire width but of higher thickness, minimal curvilinearity, and maximum connectivity. For the purpose of evaluating active fraction of the network, the algorithm was made to distinguish and quantify current carrying backbone regions as against regions containing only dangling or isolated wires. The treatment can be helpful in predicting

  16. Frame-Based Facial Expression Recognition Using Geometrical Features

    OpenAIRE

    Anwar Saeed; Ayoub Al-Hamadi; Robert Niese; Moftah Elzobi

    2014-01-01

    To improve the human-computer interaction (HCI) to be as good as human-human interaction, building an efficient approach for human emotion recognition is required. These emotions could be fused from several modalities such as facial expression, hand gesture, acoustic data, and biophysiological data. In this paper, we address the frame-based perception of the universal human facial expressions (happiness, surprise, anger, disgust, fear, and sadness), with the help of several geometrical featur...

  17. Geometric Modeling and Reasoning of Human-Centered Freeform Products

    CERN Document Server

    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...

  18. A Dynamical model for non-geometric quantum black holes

    CERN Document Server

    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.

  19. 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.

  20. Liquid ropes: a geometrical model for thin viscous jets instabilities

    CERN Document Server

    Brun, P -T; Ribe, Neil M; Eaves, Tom S; Lister, John R

    2014-01-01

    Thin viscous fluid threads falling onto a moving belt behave in a way reminiscent of a sewing machine, generating a rich variety of periodic stitch-like patterns including meanders, W-patterns, alternating loops, and translated coiling. These patterns form to accommodate the difference between the belt speed and the terminal velocity at which the falling thread strikes the belt. Using direct numerical simulations, we show that inertia is not required to produce the aforementioned patterns. We introduce a quasi-static geometrical model which captures the patterns, consisting of three coupled ODEs for the radial deflection, the orientation and the curvature of the path of the thread's contact point with the belt. The geometrical model reproduces well the observed patterns and the order in which they appear as a function of the fall height.

  1. Rigorous geometrical modeling of ALSAT-2A Algerian satellite

    Science.gov (United States)

    Boukerch, Issam; Hadied, Mohammed; Mahmoudi, Redouane; Takarli, Bachir; Hasni, Kamel

    2012-09-01

    The use of the national very high resolution space system Alsat-2A is a primordial task having a significant technological and economical interest assuring the strengthening autonomy in terms of availability and coverage in the satellite data. Also it allows us to improve and update the base and thematic mapping throughout the national territory. Firstly, the characteristics of ALSAT-2A are presented, namely the images and the imaging system with a brief history of ALSAT program. Secondly, as a prerequisite, knowing the internal parameters is essentials to modelize the geometry of such imaging system. From metadata given by the images distributor and ground control points, several test are described and the results are presented. The test data are supplied by ASAL (Algerian Space Agency), the first dataset comprise a panchromatic image over the region of El Bayadh in the North West of Algeria equipped with nine GPS surveyed points. The second dataset is an along track stereoscopic panchromatic 1A level images over the town of sevilla in the south of Spain with 24 GCPs. Finally, a discussion on obtained results is dressed showing the geometric capability of ALSAT-2A.

  2. Modelling the mass of kiwi fruit by geometrical attributes

    OpenAIRE

    A. Tabatabaeefar; A.N. Lorestani

    2006-01-01

    The determination of mathematical models for predicting the mass of kiwi fruits from their dimensions and projected areas was done. The research was conducted on 200 observations of two Iranian varieties of kiwi fruit (Abbott and Hayward). The physical characteristics measured included mass, volume, dimensions and projected areas perpendicular to major diameters. Maximum, mean, minimum values, standard deviation, coefficient of variation, bulk density (BD), geometric mean diameter (GM), and ...

  3. A geometric crescent model for black hole images

    OpenAIRE

    Kamruddin, Ayman Bin; Dexter, Jason

    2013-01-01

    The Event Horizon Telescope (EHT), a global very long baseline interferometry array operating at millimetre wavelengths, is spatially resolving the immediate environments of black holes for the first time. The current observations of the Galactic center black hole, Sagittarius A* (Sgr A*), and M87 have been interpreted in terms of either geometric models (e.g., a symmetric Gaussian) or detailed calculations of the appearance of black hole accretion flows. The former are not physically motivat...

  4. Structure alignment based on coding of local geometric measures

    Directory of Open Access Journals (Sweden)

    Rinne Andrew W

    2006-07-01

    Full Text Available Abstract Background A structure alignment method based on a local geometric property is presented and its performance is tested in pairwise and multiple structure alignments. In this approach, the writhing number, a quantity originating from integral formulas of Vassiliev knot invariants, is used as a local geometric measure. This measure is used in a sliding window to calculate the local writhe down the length of the protein chain. By encoding the distribution of writhing numbers across all the structures in the protein databank (PDB, protein geometries are represented in a 20-letter alphabet. This encoding transforms the structure alignment problem into a sequence alignment problem and allows the well-established algorithms of sequence alignment to be employed. Such geometric alignments offer distinct advantages over structural alignments in Cartesian coordinates as it better handles structural subtleties associated with slight twists and bends that distort one structure relative to another. Results The performance of programs for pairwise local alignment (TLOCAL and multiple alignment (TCLUSTALW are readily adapted from existing code for Smith-Waterman pairwise alignment and for multiple sequence alignment using CLUSTALW. The alignment algorithms employed a blocked scoring matrix (TBLOSUM generated using the frequency of changes in the geometric alphabet of a block of protein structures. TLOCAL was tested on a set of 10 difficult proteins and found to give high quality alignments that compare favorably to those generated by existing pairwise alignment programs. A set of protein comparison involving hinged structures was also analyzed and TLOCAL was seen to compare favorably to other alignment methods. TCLUSTALW was tested on a family of protein kinases and reveal conserved regions similar to those previously identified by a hand alignment. Conclusion These results show that the encoding of the writhing number as a geometric measure allow high

  5. 2D geometric measurement method based on industrial CT images

    International Nuclear Information System (INIS)

    To achieve the non-destructive measurement of the internal structure of the objects, a kind of automatic dimension measuring method using industrial computed tomography (ICT) images was presented based on a threshold of edge extraction. First, a pretreatment of CT images was carried out Then, the best threshold segmentation method was used to extract edge, based on this work the automatic geometry measurement of the CT images was achieved. The results show that geometric measurement of images reaches to a certain degree of accuracy and meet the basic needs of accuracy and repeatability. Simultaneously this method may reduce the influence of artifacts. (authors)

  6. Geant4-based comprehensive study of the absorbed fraction for electrons and gamma-photons using various geometrical models and biological tissues

    Directory of Open Access Journals (Sweden)

    Rahman Ziaur

    2013-01-01

    Full Text Available The Geant4-based comprehensive model has been developed to predict absorbed fraction values for both electrons and gamma photons in spherical, ellipsoidal, and cylindrical geometries. Simulations have been carried out for water, ICRP soft-, brain-, lung-, and ICRU bone tissue for electrons in 0.1 MeV-4 MeV and g-photons in the 0.02 MeV-2.75 MeV energy range. Consistent with experimental observations, the Geant4-simulated values of absorbed fractions show a decreasing trend with an increase in radiation energy. Compared with NIST XCOM and ICRU data, the Geant4-based simulated values of the absorbed fraction remain within a 4.2% and 1.6% deviation, respectively. For electrons and g-photons, the relative difference between the Geant4-based comprehensive model predictions and those of Stabin and Konijnenberg's re-evaluation remains within a 6.8% and 7.4% range, respectively. Ellipsoidal and cylindrical models show 4.9% and 10.1% higher respective values of absorbed dose fractions relative to the spherical model. Target volume dependence of the absorbed fraction values has been found to follow a logical behavior for electrons and Belehradek's equation for g-photons. Gamma-ray absorbed fraction values have been found to be sensitive to the material composition of targets, especially at low energies, while for elections, they remain insensitive to them.

  7. Information geometric modeling of scattering induced quantum entanglement

    International Nuclear Information System (INIS)

    We present an information geometric analysis of entanglement generated by an s-wave scattering between two Gaussian wave packets. We conjecture that the pre- and post-collisional quantum dynamical scenarios related to an elastic head-on collision are macroscopic manifestations emerging from microscopic statistical structures. We then describe them by uncorrelated and correlated Gaussian statistical models, respectively. This allows us to express the entanglement strength in terms of scattering potential and incident particle energies. Furthermore, we show how the entanglement duration can be related to the scattering potential and incident particle energies. Finally, we discuss the connection between entanglement and complexity of motion. -- Highlights: → Information geometric characterization of scattering induced entanglement. → Connection between purity, scattering potential and incident particle energies. → Connection between complexity of motion and entanglement.

  8. Software module for geometric product modeling and NC tool path generation

    International Nuclear Information System (INIS)

    The intelligent CAD/CAM system named VIRTUAL MANUFACTURE is created. It is consisted of four intelligent software modules: the module for virtual NC machine creation, the module for geometric product modeling and automatic NC path generation, the module for virtual NC machining and the module for virtual product evaluation. In this paper the second intelligent software module is presented. This module enables feature-based product modeling carried out via automatic saving of the designed product geometric features as knowledge data. The knowledge data are afterwards applied for automatic NC program generation for the designed product NC machining. (Author)

  9. 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.

  10. Material Characterization and Geometric Segmentation of a Composite Structure Using Microfocus X-Ray Computed Tomography Image-Based Finite Element Modeling

    Science.gov (United States)

    Abdul-Aziz, Ali; Roth, D. J.; Cotton, R.; Studor, George F.; Christiansen, Eric; Young, P. C.

    2011-01-01

    This study utilizes microfocus x-ray computed tomography (CT) slice sets to model and characterize the damage locations and sizes in thermal protection system materials that underwent impact testing. ScanIP/FE software is used to visualize and process the slice sets, followed by mesh generation on the segmented volumetric rendering. Then, the local stress fields around several of the damaged regions are calculated for realistic mission profiles that subject the sample to extreme temperature and other severe environmental conditions. The resulting stress fields are used to quantify damage severity and make an assessment as to whether damage that did not penetrate to the base material can still result in catastrophic failure of the structure. It is expected that this study will demonstrate that finite element modeling based on an accurate three-dimensional rendered model from a series of CT slices is an essential tool to quantify the internal macroscopic defects and damage of a complex system made out of thermal protection material. Results obtained showing details of segmented images; three-dimensional volume-rendered models, finite element meshes generated, and the resulting thermomechanical stress state due to impact loading for the material are presented and discussed. Further, this study is conducted to exhibit certain high-caliber capabilities that the nondestructive evaluation (NDE) group at NASA Glenn Research Center can offer to assist in assessing the structural durability of such highly specialized materials so improvements in their performance and capacities to handle harsh operating conditions can be made.

  11. Mesh Geometric Editing Approach Based on Gpu Texture

    Directory of Open Access Journals (Sweden)

    Guiping Qian

    2012-09-01

    Full Text Available This paper presents a novel interactive mesh editing approach based on GPU texture mapping. The main feature is that it copies 2D surface geometry information to GPU frame buffer. The planar mesh information is transformed into GPU texture and placed on apposite position of target mesh. 3D information is retrieved after stitching two mesh components from the primitive vertex coordinates. When running real-time mesh cloning operator, our mesh editing approach can copy arbitrary irregular geometric features from source mesh to target mesh. Experimental results indicate that our method can outperform previous related mesh editing techniques.

  12. Stochastic model for the geometrical rail track degradation process in the Portuguese railway Northern Line

    International Nuclear Information System (INIS)

    The geometrical track degradation is characterized by the evolution over time (or tonnage) of several parameters such as the longitudinal level, the alignment, the gauge, the twist and the cross level. Dynamic track inspections allow monitoring the track geometrical quality which is essential to ensure track availability and reliability, passenger safety and comfort and also energy efficiency. The track geometrical quality is guaranteed by performing condition-based maintenance and renewal actions during the life of the track and for that it is crucial to understand the geometrical track degradation process. In this paper, a stochastic model for characterizing the geometrical track degradation process over time is presented. The Portuguese railway Northern Line is adopted as a case-study and a statistic analysis is performed for different vehicle speed groups, in accordance with CEN [1]. The new contribution of this research is that the Dagum distribution, usually adopted for representing the income distribution, may represent the geometrical track degradation process in terms of the longitudinal level

  13. Subjective surfaces: a geometric model for boundary completion

    Energy Technology Data Exchange (ETDEWEB)

    Sarti, Alessandro; Malladi, Ravi; Sethian, J.A.

    2000-06-01

    We present a geometric model and a computational method for segmentation of images with missing boundaries. In many situations, the human visual system fills in missing gaps in edges and boundaries, building and completing information that is not present. Boundary completion presents a considerable challenge in computer vision, since most algorithms attempt to exploit existing data. A large body of work concerns completion models, which postulate how to construct missing data; these models are often trained and specific to particular images. In this paper, we take the following, alternative perspective: we consider a reference point within an image as given, and then develop an algorithm which tries to build missing information on the basis of the given point of view and the available information as boundary data to the algorithm. Starting from this point of view, a surface is constructed. It is then evolved with the mean curvature flow in the metric induced by the image until a piecewise constant solution is reached. We test the computational model on modal completion, amodal completion, texture, photo and medical images. We extend the geometric model and the algorithm to 3D in order to extract shapes from low signal/noise ratio medical volumes. Results in 3D echocardiography and 3D fetal echography are presented.

  14. The geometric Schwinger Model on the Torus II

    Energy Technology Data Exchange (ETDEWEB)

    Joos, H. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Azakov, S.I. [AN Azerbajdzhanskoj SSR, Baku (Azerbaijan). Inst. Fiziki]|[Institute for Advanced Studies in Basic Sciences, Zanjan (Iran, Islamic Republic of)

    1994-08-01

    The geometric Schwinger Model (gSM) is the theory of a U(1)-gauge field in two dimensions coupled to a massless Dirac Kaehler field. It is equivalent to a Schwinger model with Dirac fields {Phi}{sub a}{sup b}(x) carrying iso-spin 1/2. We consider this model on the Euclidean space time of a torus. In Part I we discussed in detail the zero mode structure of this model. The main aim of this Part is the calculation of the correlation functions of currents and densities. Since it turned out that the gSM illustrates the generally interesting structure of anomalous chiral symmetry breaking in a very transparent manner, we present our results in the more familiar language of Dirac fields. In the introduction to the first part of our investigations we mentioned as motivation for the study of the gSM on the torus the possibility of a systematic lattice approximation of this model. In the meanwhile this project was realized to a large extend. Here we give the details of the discussion of the different quantities in the continuum to which we applied the lattice approximation. For these we formulate the `geometric` description by differential forms of quantities which we consider interesting in this context. (orig.)

  15. The geometric Schwinger Model on the Torus II

    International Nuclear Information System (INIS)

    The geometric Schwinger Model (gSM) is the theory of a U(1)-gauge field in two dimensions coupled to a massless Dirac Kaehler field. It is equivalent to a Schwinger model with Dirac fields Φab(x) carrying iso-spin 1/2. We consider this model on the Euclidean space time of a torus. In Part I we discussed in detail the zero mode structure of this model. The main aim of this Part is the calculation of the correlation functions of currents and densities. Since it turned out that the gSM illustrates the generally interesting structure of anomalous chiral symmetry breaking in a very transparent manner, we present our results in the more familiar language of Dirac fields. In the introduction to the first part of our investigations we mentioned as motivation for the study of the gSM on the torus the possibility of a systematic lattice approximation of this model. In the meanwhile this project was realized to a large extend. Here we give the details of the discussion of the different quantities in the continuum to which we applied the lattice approximation. For these we formulate the 'geometric' description by differential forms of quantities which we consider interesting in this context. (orig.)

  16. Calibration and Validation of Airborne InSAR Geometric Model

    International Nuclear Information System (INIS)

    The image registration or geo-coding is a very important step for many applications of airborne interferometric Synthetic Aperture Radar (InSAR), especially for those involving Digital Surface Model (DSM) generation, which requires an accurate knowledge of the geometry of the InSAR system. While the trajectory and attitude instabilities of the aircraft introduce severe distortions in three dimensional (3-D) geometric model. The 3-D geometrical model of an airborne SAR image depends on the SAR processor itself. Working at squinted model, i.e., with an offset angle (squint angle) of the radar beam from broadside direction, the aircraft motion instabilities may produce distortions in airborne InSAR geometric relationship, which, if not properly being compensated for during SAR imaging, may damage the image registration. The determination of locations of the SAR image depends on the irradiated topography and the exact knowledge of all signal delays: range delay and chirp delay (being adjusted by the radar operator) and internal delays which are unknown a priori. Hence, in order to obtain reliable results, these parameters must be properly calibrated. An Airborne InSAR mapping system has been developed by the Institute of Remote Sensing and Digital Earth (RADI), Chinese Academy of Sciences (CAS) to acquire three-dimensional geo-spatial data with high resolution and accuracy. To test the performance of the InSAR system, the Validation/Calibration (Val/Cal) campaign has carried out in Sichun province, south-west China, whose results will be reported in this paper

  17. Geant4-based comprehensive study of the absorbed fraction for electrons and gamma-photons using various geometrical models and biological tissues

    OpenAIRE

    Rahman Ziaur; Rehman Shakeel Ur.; Mirza Sikander M.; Arshed Waheed; Mirza Nasir M.

    2013-01-01

    The Geant4-based comprehensive model has been developed to predict absorbed fraction values for both electrons and gamma photons in spherical, ellipsoidal, and cylindrical geometries. Simulations have been carried out for water, ICRP soft-, brain-, lung-, and ICRU bone tissue for electrons in 0.1 MeV-4 MeV and g-photons in the 0.02 MeV-2.75 MeV energy range. Consistent with experimental observations, the Geant4-simulated values of absorbed fractions show a ...

  18. Numerical treatment of a geometrically nonlinear planar Cosserat shell model

    Science.gov (United States)

    Sander, Oliver; Neff, Patrizio; Bîrsan, Mircea

    2016-05-01

    We present a new way to discretize a geometrically nonlinear elastic planar Cosserat shell. The kinematical model is similar to the general six-parameter resultant shell model with drilling rotations. The discretization uses geodesic finite elements (GFEs), which leads to an objective discrete model which naturally allows arbitrarily large rotations. GFEs of any approximation order can be constructed. The resulting algebraic problem is a minimization problem posed on a nonlinear finite-dimensional Riemannian manifold. We solve this problem using a Riemannian trust-region method, which is a generalization of Newton's method that converges globally without intermediate loading steps. We present the continuous model and the discretization, discuss the properties of the discrete model, and show several numerical examples, including wrinkling of thin elastic sheets in shear.

  19. Modeling the geometric formation and powder deposition mass in laser induction hybrid cladding

    International Nuclear Information System (INIS)

    A new laser induction hybrid cladding technique on cylinder work piece is presented. Based on a series of laser induction hybrid experiments by off axial powder feeding, the predicting models of individual clad geometric formation and powder catchment were developed in terms of powder feeding rate, laser special energy and induction energy density using multiple regression analysis. In addition, confirmation tests were performed to make a comparison between the predicting results and measured ones. Via the experiments and analysis, the conclusions can be lead to that the process parameters have crucial influence on the clad geometric formation and powder catchment, and that the predicting model reflects well the relationship between the clad geometric formation and process parameters in laser induction hybrid cladding

  20. The geometrical optics approach to atmospheric propagation models

    Science.gov (United States)

    Doss-Hammel, Stephen M.

    2003-04-01

    An accurate model for the propagation of infrared and optical frequencies through the atmosphere is a requirement for a number of important communications and surveillance systems. These systems operate over long nearly-horizontal paths that are close to the land or sea surface. There can be strong heat and mass flux gradients near the surface which make accurate transmission predictions difficult. The development and utility of geometrical optics, or ray-trace, methods for the EOSTAR and IRWarp models will be addressed. Both models are driven by bulk meteorological models to provide the environmental fields that can subsequently be used to define the refractivity field. The ray-trace algorithm uses the refractivity field to generate a transfer map. The transfer map provides precise information concerning the number, location, and orientation of the images of a source point. One application of this information is the geometric gain, or the refractive propagation factor, which is an output consisting of a vertical signal intensity profile at a given range. A second application is a passive ranging capability for sub-refractive conditions. The ranging calculation uses the existence of an inferior mirage image to deduce the target range and height.

  1. High-Fidelity Geometric Modelling for Biomedical Applications

    Energy Technology Data Exchange (ETDEWEB)

    Zeyun Yu, Michael Holst, and J.A. McCammon

    2008-04-01

    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). The availability of this software toolchain will give researchers in computational biomedicine and other modeling areas access to higher-fidelity geometric models.

  2. An integrated introduction to computer graphics and geometric modeling

    CERN Document Server

    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

  3. SU-E-J-257: A PCA Model to Predict Adaptive Changes for Head&neck Patients Based On Extraction of Geometric Features From Daily CBCT Datasets

    International Nuclear Information System (INIS)

    Purpose: Using daily cone beam CTs (CBCTs) to develop principal component analysis (PCA) models of anatomical changes in head and neck (H&N) patients and to assess the possibility of using these prospectively in adaptive radiation therapy (ART). Methods: Planning CT (pCT) images of 4 H&N patients were deformed to model several different systematic changes in patient anatomy during the course of the radiation therapy (RT). A Pinnacle plugin was used to linearly interpolate the systematic change in patient for the 35 fraction RT course and to generate a set of 35 synthetic CBCTs. Each synthetic CBCT represents the systematic change in patient anatomy for each fraction. Deformation vector fields (DVFs) were acquired between the pCT and synthetic CBCTs with random fraction-to-fraction changes were superimposed on the DVFs. A patient-specific PCA model was built using these DVFs containing systematic plus random changes. It was hypothesized that resulting eigenDVFs (EDVFs) with largest eigenvalues represent the major anatomical deformations during the course of treatment. Results: For all 4 patients, the PCA model provided different results depending on the type and size of systematic change in patient’s body. PCA was more successful in capturing the systematic changes early in the treatment course when these were of a larger scale with respect to the random fraction-to-fraction changes in patient’s anatomy. For smaller scale systematic changes, random changes in patient could completely “hide” the systematic change. Conclusion: The leading EDVF from the patientspecific PCA models could tentatively be identified as a major systematic change during treatment if the systematic change is large enough with respect to random fraction-to-fraction changes. Otherwise, leading EDVF could not represent systematic changes reliably. This work is expected to facilitate development of population-based PCA models that can be used to prospectively identify significant

  4. The Minimized Power Geometric model: An analytical mixing model for calculating polyphase rock viscosities consistent with experimental data

    OpenAIRE

    Huet, Benjamin; Yamato, Philippe; Grasemann, Bernhard

    2014-01-01

    Here we introduce the Minimized Power Geometric (MPG) model which predicts the viscosity of any polyphase rocks deformed during ductile flow. The volumetric fractions and power law parameters of the constituting phases are the only model inputs required. The model is based on a minimization of the mechanical power dissipated in the rock during deformation. In contrast to existing mixing models based on minimization, we use the Lagrange multipliers method and constraints of strain rate and str...

  5. Geometric modelling of a make mandible utilising CT imaging

    International Nuclear Information System (INIS)

    Full text: The mandible is one of the most important and frequently used bones in the human body. It is responsible for basic actions such as mastication, communication and swallowing. It houses and provides protection for the tongue, teeth and salivary glands. The mandible is unique in that it has two anatomically identical articulations, each providing the same function. Both articulations, however, rarely have synchronous force and motion characteristics. The mandible is the only moveable bone in the skull and is capable of the following motions: depression - lowering the mandible, as in yawning, elevation - raising the mandible, protraction - thrusting the jaw forward, retraction - withdrawing the jaw posteriorly, and lateral deviation - sideways displacement in the transverse plane. The mandible is an irregular bone comprising a broad U shaped body with two ascending rami. The rami are quadrilateral plate like structures with lateral sides which are nearly flat. The mandible is subjected to repetitive loading and is susceptible to wear at its articulations, cyclic fatigue and dislocation. Despite the importance of the mandible little is understood about its mechanical properties and loading parameters. The purpose of this study was to create a three dimensional geometric model of a human mandible based on anatomical data. A 21 year old male with no history of mandible fracture or temporomandibular joint dysfunction was selected. The mandible was non-invasively imaged by Computed Tomography (CT). The subject was imaged lying on his back with the head supported and immobilised by a U shaped head rest. Seventeen parallel cross-sectional images oblique to the transverse plane were constructed. Cortical and cancellous bone boundaries were manually digitised for every image using a Science Accessories Corporation GP-9 digitiser linked to an IBM 286 SX personal computer. The data was transferred to a global coordinate system and entered into MSC/PATRAN finite element

  6. Geant4.10 simulation of geometric model for metaphase chromosome

    Science.gov (United States)

    Rafat-Motavalli, L.; 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.

  7. NEW APPROACH FOR IMAGE REPRESENTATION BASED ON GEOMETRIC STRUCTURAL CONTENTS

    Institute of Scientific and Technical Information of China (English)

    Jia Xiaomeng; Wang Guoyu

    2003-01-01

    This paper presents a novel approach for representation of image contents based on edge structural features. Edge detection is carried out for an image in the pre-processing stage.For feature representation, edge pixels are grouped into a set of segments through geometrical partitioning of the whole edge image. Then the invariant feature vector is computed for each edge-pixel segment. Thereby the image is represented with a set of spatially distributed feature vectors, each of which describes the local pattern of edge structures. Matching of two images can be achieved by the correspondence of two sets of feature vectors. Without the difficulty of image segmentation and object extraction due to the complexity of the real world images, the proposed approach provides a simple and flexible description for the image with complex scene, in terms of structural features of the image content. Experiments with real images illustrate the effectiveness of this new method.

  8. A geometric reasoning based algorithm for point pattern matching

    Institute of Scientific and Technical Information of China (English)

    徐文立; 张立华

    2001-01-01

    Point pattern matching (PPM) is an important topic in computer vision and pattern recognition. It can be widely used in many areas such as image registration, object recognition, motion detection, target tracking, autonomous navigation, and pose estimation. This paper discusses the incomplete matching problem of two point sets under Euclidean transformation. According to geometric reasoning, some definitions for matching clique, support point pair, support index set, and support index matrix, etc. are given. Based on the properties and theorems of them, a novel reasoning algorithm is presented, which searches for the optimal sOlLtion from top to bottom and could find out as many consistent corresponding point pairs as possible. Theoretical analysis and experimental results show that the new algorithm is very effective, and could be, under some conditions, applied to the PPM problem under other kind of transformations.

  9. 基于几何结构的2.5D卡通建模%2 . 5 D Cartoon Modeling Based on Geometric Structure

    Institute of Scientific and Technical Information of China (English)

    刘艳; 胡艳宏; 孙战利

    2015-01-01

    二维卡通制作技术大致分为计算机辅助2D卡通动画制作和利用3D建模技术渲染生成动画。将两者结合,提出一种2.5D卡通制作模型,通过几何结构的旋转进行纹理贴图,并构造卡通的旋转过程。在2D动画中,一个卡通形象本身隐含几何结构,将卡通形象定义为由只含一个典型几何结构卡通元素构成的卡通对象,利用典型几何结构二维投影变化规律,构建相应结构卡通元素的变形算法,分析长方体和球体卡通元素在转动时投影的变化规律,给出基于这些规律实现相应结构卡通元素伪3D转动效果的算法。通过长方体、球体、圆柱体进行旋转的实验结果证明了算法的有效性。%Technologies of 2 D cartoon animation can be roughly categorized into two types:one is computer-aided 2 D cartoon animation,and the other is rendering 3D models. These two both have their own pros and cons. So this paper proposes a way which combines both of them,that is 2. 5D cartoon modelling method which constructs the rotation of the cartoon by texture mapping. In 2D animation,a character has an implicit geometry structure. So in this paper,it defines a character as a cartoon object composed of only one typical geometry structure. This paper builds the deformation algorithm of corresponding structure through the two dimensional projection transformation of typical geometries. Detailed analysis of projection transformation patterns of rectangular and sphere are provided. Based on patterns founded,this paper provides algorithm for implementing pseudo-3D rotation effects for the corresponding carton elements, and gives the results of cuboid,sphere and cylinder to support the validity of the algorithm.

  10. Mediastinal Hodgkin lymphomas in computertomography: exact CT-based volume assessment and approximations with simple geometric models; Mediastinale Hodgkin-Lymphone in der Computertomographie. Vergleich von exakter CT-gestuetzter Volumetrie und Volumenabschaetzung mit Hilfe einfacher geometrischer Modelle

    Energy Technology Data Exchange (ETDEWEB)

    Battmann, A. [Marburg Univ. (Germany). Abt. fuer Strahlendiagnostik; Dieckmann, K.; Resch, A.; Poetter, R. [Allgemeines Krankenhaus, Wien (Austria). Universitaetsklinik Strahlentherapie und Strahlenbiologie; Battmann, A. [Giessen Univ. (Germany). Zentrum fuer Pathologie

    2001-03-01

    Background: The importance of the size of the primary tumor in lymphomas and its size after treatment is still uncertain. Assuming a prognostic relevance, an assessment of tumor volume before and after induction of chemotherapy has been performed in the pediatric Hodgkin's disease study (HD-90). Since an exact CT-scan-based volumetric tumor assessment is time-consuming and in some centers not possible, the tumor volume is often estimated based on simple geometric approximations. Aim of this study was the development of an easy to apply and nearly exact model of volume estimation compared to CT-scan-based tumor volume measurements. Material and Methods: thirty computed tomographies (CT) of mediastinal Hodgkin lymphomas of children aged 5 to 16 years have been examined. The CT scans were digitalized using a CCD camera combined with a frame grabber. Applying the Global Lab image software, the true tumor volume was determined excluding local organs, which did not belong to the lymphoma. Subsequently, volumes were assessed using simple geometric models (block, ellipsoid, octaeder) by using the maximum diameters of the tumor. The differences between the volume of the geometric models and the true volume, based on the CT scan evaluation, were compared. Results: the maximum diameters of a tumor can be used to calculate its volume based on simple geometric models. The model 'block' overestimates the volume by 89 to 268%. The model 'ellipsoid' overestimates the volume on average by 29%. The model 'octaeder' underestimates the volume on average by 18%. A division of the block volume by 2.3 approximated the geometric closest to the true volume: the average volume was overestimated by 2% in tumors with a volume larger than 20 ml. No model was sufficient to approximate tumors with a volume of less than 20 ml. Conclusions: for the estimation of tumor volumes in mediastinal Hodgkin lumphomas exceeding 20 ml, the formula 'block /2.3&apos

  11. 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.

  12. 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

  13. Conformal chiral boson models on twisted doubled tori and non-geometric string vacua

    CERN Document Server

    Avramis, Spyros D; Prezas, Nikolaos

    2009-01-01

    We derive and analyze the conditions for quantum conformal and Lorentz invariance of the duality symmetric interacting chiral boson sigma-models, which are conjectured to describe non-geometric string theory backgrounds. The one-loop Weyl and Lorentz anomalies are computed for the general case using the background field method. Subsequently, our results are applied to a class of (on-shell) Lorentz invariant chiral boson models which are based on twisted doubled tori. Our findings are in agreement with those expected from the effective supergravity approach, thereby firmly establishing that the chiral boson models under consideration provide the string worldsheet description of N=4 gauged supergravities with electric gaugings. Furthermore, they demonstrate that twisted doubled tori are indeed the doubled internal geometries underlying a large class of non-geometric string compactifications. For compact gaugings the associated chiral boson models are automatically conformal, a fact that is explained by showing ...

  14. Automatic Target Recognition in Synthetic Aperture Sonar Images Based on Geometrical Feature Extraction

    OpenAIRE

    J. Del Rio Vera; Coiras, E.; Groen, J; Evans, B.

    2009-01-01

    This paper presents a new supervised classification approach for automated target recognition (ATR) in SAS images. The recognition procedure starts with a novel segmentation stage based on the Hilbert transform. A number of geometrical features are then extracted and used to classify observed objects against a previously compiled database of target and non-target features. The proposed approach has been tested on a set of 1528 simulated images created by the NURC SIGMAS sonar model, achieving...

  15. Automatic Target Recognition in Synthetic Aperture Sonar Images Based on Geometrical Feature Extraction

    Science.gov (United States)

    Del Rio Vera, J.; Coiras, E.; Groen, J.; Evans, B.

    2009-12-01

    This paper presents a new supervised classification approach for automated target recognition (ATR) in SAS images. The recognition procedure starts with a novel segmentation stage based on the Hilbert transform. A number of geometrical features are then extracted and used to classify observed objects against a previously compiled database of target and non-target features. The proposed approach has been tested on a set of 1528 simulated images created by the NURC SIGMAS sonar model, achieving up to 95% classification accuracy.

  16. Methodology for geometric modelling. Presentation and administration of site descriptive models; Metodik foer geometrisk modellering. Presentation och administration av platsbeskrivande modeller

    Energy Technology Data Exchange (ETDEWEB)

    Munier, Raymond [Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden); Hermanson, Jan [Golder Associates (Sweden)

    2001-03-01

    This report presents a methodology to construct, visualise and present geoscientific descriptive models based on data from the site investigations, which the SKB currently performs, to build an underground nuclear waste disposal facility in Sweden. It is designed for interaction with SICADA (SKB:s site characterisation database) and RVS (SKB:s Rock Visualisation System). However, the concepts of the methodology are general and can be used with other tools capable of handling 3D geometries and parameters. The descriptive model is intended to be an instrument where site investigation data from all disciplines are put together to form a comprehensive visual interpretation of the studied rock mass. The methodology has four main components: 1. Construction of a geometrical model of the interpreted main structures at the site. 2. Description of the geoscientific characteristics of the structures. 3. Description and geometrical implementation of the geometric uncertainties in the interpreted model structures. 4. Quality system for the handling of the geometrical model, its associated database and some aspects of the technical auditing. The geometrical model forms a basis for understanding the main elements and structures of the investigated site. Once the interpreted geometries are in place in the model, the system allows for adding descriptive and quantitative data to each modelled object through a system of intuitive menus. The associated database allows each geometrical object a complete quantitative description of all geoscientific disciplines, variabilities, uncertainties in interpretation and full version history. The complete geometrical model and its associated database of object descriptions are to be recorded in a central quality system. Official, new and old versions of the model are administered centrally in order to have complete quality assurance of each step in the interpretation process. The descriptive model is a cornerstone in the understanding of the

  17. 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.

  18. Rapid world modeling: Fitting range data to geometric primitives

    International Nuclear Information System (INIS)

    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

  19. Generalised geometrical CP violation in a T′ lepton flavour model

    International Nuclear Information System (INIS)

    We analyse the interplay of generalised CP transformations and the non-Abelian discrete group T′ and use the semi-direct product Gf=T′⋊HCP, 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

  20. Geometrical Derivation of Differential Kinematics to Calibrate Model Parameters of Flexible Manipulator

    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.

  1. Geometric data perturbation-based personal health record transactions in cloud computing.

    Science.gov (United States)

    Balasubramaniam, S; Kavitha, V

    2015-01-01

    Cloud computing is a new delivery model for information technology services and it typically involves the provision of dynamically scalable and often virtualized resources over the Internet. However, cloud computing raises concerns on how cloud service providers, user organizations, and governments should handle such information and interactions. Personal health records represent an emerging patient-centric model for health information exchange, and they are outsourced for storage by third parties, such as cloud providers. With these records, it is necessary for each patient to encrypt their own personal health data before uploading them to cloud servers. Current techniques for encryption primarily rely on conventional cryptographic approaches. However, key management issues remain largely unsolved with these cryptographic-based encryption techniques. We propose that personal health record transactions be managed using geometric data perturbation in cloud computing. In our proposed scheme, the personal health record database is perturbed using geometric data perturbation and outsourced to the Amazon EC2 cloud. PMID:25767826

  2. Geometric Data Perturbation-Based Personal Health Record Transactions in Cloud Computing

    Directory of Open Access Journals (Sweden)

    S. Balasubramaniam

    2015-01-01

    Full Text Available Cloud computing is a new delivery model for information technology services and it typically involves the provision of dynamically scalable and often virtualized resources over the Internet. However, cloud computing raises concerns on how cloud service providers, user organizations, and governments should handle such information and interactions. Personal health records represent an emerging patient-centric model for health information exchange, and they are outsourced for storage by third parties, such as cloud providers. With these records, it is necessary for each patient to encrypt their own personal health data before uploading them to cloud servers. Current techniques for encryption primarily rely on conventional cryptographic approaches. However, key management issues remain largely unsolved with these cryptographic-based encryption techniques. We propose that personal health record transactions be managed using geometric data perturbation in cloud computing. In our proposed scheme, the personal health record database is perturbed using geometric data perturbation and outsourced to the Amazon EC2 cloud.

  3. Dynamics and geometric properties of the k-trigonometric model

    International Nuclear Information System (INIS)

    We analyse the dynamics and the geometric properties of the potential energy surfaces (PES) of the k-trigonometric model (kTM), defined by a fully connected k-body interaction. This model has no thermodynamic transition for k = 1, a second-order one for k = 2, and a first-order one for k > 2. In this paper we (i) show that the single-particle dynamics can be traced back to an effective dynamical system (with only one degree of freedom), (ii) compute the diffusion constant analytically, (iii) determine analytically several properties of the self-correlation functions apart from the relaxation times which we calculate numerically, (iv) relate the collective correlation functions to those of the effective degree of freedom using an exact Dyson-like equation, (v) using two analytical methods, calculate the saddles of the PES that are visited by the system evolving at fixed temperature. On the one hand we minimize vertical bar ∇V vertical bar2, as usually done in the numerical study of supercooled liquids and, on the other hand, we compute the saddles with minimum distance (in configuration space) from initial equilibrium configurations. We find the same result from the two calculations and we speculate that the coincidence might go beyond the specific model investigated here

  4. Dynamics and geometric properties of the k-trigonometric model

    International Nuclear Information System (INIS)

    We analyze the dynamics and the geometric properties of the Potential Energy Surfaces (PES) of the k-Trigonometric Model (kTM), defined by a fully-connected fc-body interaction. This model has no thermodynamic transition for k = 1, a second order one for k=2 and a first order one for k>2. In this paper we i) show that the single particle dynamics can be traced back to an effective dynamical system (with only one degree of freedom); ii) compute the diffusion constant analytically; iii) determine analytically several properties of the self correlation functions apart from the relaxation times which we calculate numerically; iv) relate the collective correlation functions to the ones of the effective degree of freedom using an exact Dyson-like equation; v) using two analytical methods, calculate the saddles of the PES that are visited by the system evolving at fixed temperature. On the one hand we minimize vertical bar∇Vvertical bar2, as usually done in the numerical study of supercooled liquids and, on the other hand, we compute the saddles with minimum distance (in configuration space) from initial equilibrium configurations. We find the same result from the two calculations and we speculate that the coincidence might go beyond the specific model investigated here. (author)

  5. The Van Hiele Model of Geometric Thought and possible contributions to the dynamic geometry

    Directory of Open Access Journals (Sweden)

    ALVES, G. S.

    2010-06-01

    Full Text Available This work presents the main ideas discussed in an essay written in a Computers and Education class in a Master Course at PPGI-UFRJ. We discuss the need to emphasize the topics related to euclidian geometry in primary and secondary schools. The Van Hiele model of the development of geometric thought is presented as a guideline for learning and as an instrument for the evaluation of students´ geometric abilities. Based on Van Hiele ideas and on tests created by the Fundão/UFRJ Project staff, a quantitative study on the level of geomteric thought was performed with students of a public technical high school in Rio de Janeiro. As conclusions, an exposition on possible contributions of dynamic geometry to the Van Hiele model is made.

  6. Modeling bidirectional reflectance of forests and woodlands using Boolean models and geometric optics

    Science.gov (United States)

    Strahler, Alan H.; Jupp, David L. B.

    1990-01-01

    Geometric-optical discrete-element mathematical models for forest canopies have been developed using the Boolean logic and models of Serra. The geometric-optical approach is considered to be particularly well suited to describing the bidirectional reflectance of forest woodland canopies, where the concentration of leaf material within crowns and the resulting between-tree gaps make plane-parallel, radiative-transfer models inappropriate. The approach leads to invertible formulations, in which the spatial and directional variance provides the means for remote estimation of tree crown size, shape, and total cover from remotedly sensed imagery.

  7. Nonlinear Geometric Optics method based multi-scale numerical schemes for highly-oscillatory transport equations

    CERN Document Server

    Crouseilles, Nicolas; Lemou, Mohammed

    2016-01-01

    We introduce a new numerical strategy to solve a class of oscillatory transport PDE models which is able to captureaccurately the solutions without numerically resolving the high frequency oscillations {\\em in both space and time}.Such PDE models arise in semiclassical modeling of quantum dynamics with band-crossings, and otherhighly oscillatory waves. Our first main idea is to use the nonlinear geometric optics ansatz, which builds theoscillatory phase into an independent variable. We then choose suitable initial data, based on the Chapman-Enskog expansion, for the new model. For a scalar model, we prove that so constructed model will have certain smoothness, and consequently, for a first order approximation scheme we prove uniform error estimates independent of the (possibly small) wave length. The method is extended to systems arising from a semiclassical model for surface hopping, a non-adiabatic quantum dynamic phenomenon. Numerous numerical examples demonstrate that the method has the desired properties...

  8. Recognition of facial expressions based on salient geometric features and support vector machines

    OpenAIRE

    Ghimire, Deepak; Lee, Joonwhoan; Li, Ze-Nian; Jeong, Sunghwan

    2016-01-01

    Facial expressions convey nonverbal cues which play an important role in interpersonal relations, and are widely used in behavior interpretation of emotions, cognitive science, and social interactions. In this paper we analyze different ways of representing geometric feature and present a fully automatic facial expression recognition (FER) system using salient geometric features. In geometric feature-based FER approach, the first important step is to initialize and track dense set of facial p...

  9. Modeling habitat suitability for complex species distributions by environmental-distance geometric mean.

    Science.gov (United States)

    Hirzel, Alexandre H; Arlettaz, Raphaël

    2003-11-01

    This paper presents a new habitat suitability modeling method whose main properties are as follows: (1) It is based on the density of observation points in the environmental space, which enables it to fit complex distributions (e.g. nongaussian, bimodal, asymmetrical, etc.). (2) This density is modeled by computing the geometric mean to all observation points, which we show to be a good trade-off between goodness of fit and prediction power. (3) It does not need any absence information, which is generally difficult to collect and of dubious reliability. (4) The environmental space is represented either by an expert-selection of standardized variables or the axes of a factor analysis [in this paper we used the Ecological Niche Factor Analysis (ENFA)]. We first explain the details of the geometric mean algorithm and then we apply it to the bearded vulture (Gypaetus barbatus) habitat in the Swiss Alps. The results are compared to those obtained by the "median algorithm" and tested by jack-knife cross-validation. We also discuss other related algorithms (BIOCLIM, HABITAT, and DOMAIN). All these analyses were implemented into and performed with the ecology-oriented GIS software BIOMAPPER 2.0.The results show the geometric mean to perform better than the median algorithm, as it produces a tighter fit to the bimodal distribution of the bearded vulture in the environmental space. However, the "median algorithm" being quicker, it could be preferred when modeling more usual distribution. PMID:15015699

  10. The geometrical precision of the silicone matrices to the manufacturing of the models of the gear

    Directory of Open Access Journals (Sweden)

    M. Cygnar

    2009-04-01

    Full Text Available The article presents the researches of geometrical precision of silicone casting form manufactured with using of the process of rapidprototyping of the tools (RT – Rapid Tooling. The testing casting form is applied to the production of prototypes of sprockets with thepolymer resins and also the casting waxes. The determining of real geometrical precision of silicone form in the relation to the theoretical assumptions determined on the basis of the parameters of the material card of applied silicone was the purpose of researches. Silicone form was created on the basis of the stereolitographic model of sprocket. The coordinates measurable machine WENZEL LH 87 was applied to researches. The measurements of form and also base model were executed in the scanning mode on the basis of model 3D-CAD ofsprocket. In purpose of the acceleration of measurable process of base model, silicone form and also prototypes manufactured in form, the special program CNC was written. Program enables the executing of measurements in automatic mode. Measurements enabled determining of precision of manufacturing of form in the relation to nominal model 3D-CAD and also in the relation to stereolitographic base model. The next stage of the research works will concern of the execution of geometrical measurements of prototypes casted in silicone form with chosen materials: casting waxes, the polyester, the epoxy and polyurethane resins. Executed measurements will enableon determining of real precision of prototypes manufactured in silicone casting forms. The problems concerned of determining ofgeometrical precision of silicone forms and manufactured in them prototypes are considered seldom in the analysed literature from therange of rapid prototyping. From this reason presented researches in article create the original work in the theoretical and practicalaspect.

  11. Development of a geometric models visualizer generated starting from the GeeWiz module

    International Nuclear Information System (INIS)

    The present work shows an advance of the development of an application that allows visualizing geometric modules in 3 D, of constituent elements of the reactor core. The idea of generating a visualizer for the geometries, goes back to the use of the GeeWiz module, of the Scale 6.0 code. The module allows developing, in a graphic way the geometries of the components to analyze, such as fuel rods, fuel assemblies, containers among others. The GeeWiz module, allows the criticality analysis of this elements, based on the fingering Keno-V.a and/or Keno-Vi. This way, GeeWiz generates a file that details the built geometry of the elements, this file acts as entrance to execute Keno-V.a or Keno-Vi. This entrance file is used in the developed visualizer, to show the geometric constitution of the modeling components. (Author)

  12. A geometric framework for mixed quantum states based on a Kähler structure

    International Nuclear Information System (INIS)

    In this paper we introduce a geometric framework for mixed quantum states based on a Kähler structure. The geometric framework includes a symplectic form, an almost complex structure, and a Riemannian metric that characterize the space of mixed quantum states. We argue that the almost complex structure is integrable. We also in detail discuss a visualizing application of this geometric framework by deriving a geometric uncertainty relation for mixed quantum states. The framework is computationally effective and it provides us with a better understanding of general quantum mechanical systems. (paper)

  13. A simple geometrical model describing shapes of soap films suspended on two rings

    Science.gov (United States)

    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.

  14. Research on geometric error measurement system of machining center BV75 based on laser interferometer

    OpenAIRE

    Shi Lijuan; Chen Jinying; Li Zhaokun; Bian Huamei

    2016-01-01

    This paper measures the twenty one geometric errors of numerical control machining center with parameter identification through laser interferometer, the main contents illustrate the measurement system, measurement model and some testing results combined with specific experimental conditions, at the same time provide particular reference value on numerical control machine tool(NC machine tool) geometric precision detection.

  15. Research on geometric error measurement system of machining center BV75 based on laser interferometer

    Directory of Open Access Journals (Sweden)

    Shi Lijuan

    2016-01-01

    Full Text Available This paper measures the twenty one geometric errors of numerical control machining center with parameter identification through laser interferometer, the main contents illustrate the measurement system, measurement model and some testing results combined with specific experimental conditions, at the same time provide particular reference value on numerical control machine tool(NC machine tool geometric precision detection.

  16. Solution of Inverse Kinematics for 6R Robot Manipulators With Offset Wrist Based on Geometric Algebra.

    Science.gov (United States)

    Fu, Zhongtao; Yang, Wenyu; Yang, Zhen

    2013-08-01

    In this paper, we present an efficient method based on geometric algebra for computing the solutions to the inverse kinematics problem (IKP) of the 6R robot manipulators with offset wrist. Due to the fact that there exist some difficulties to solve the inverse kinematics problem when the kinematics equations are complex, highly nonlinear, coupled and multiple solutions in terms of these robot manipulators stated mathematically, we apply the theory of Geometric Algebra to the kinematic modeling of 6R robot manipulators simply and generate closed-form kinematics equations, reformulate the problem as a generalized eigenvalue problem with symbolic elimination technique, and then yield 16 solutions. Finally, a spray painting robot, which conforms to the type of robot manipulators, is used as an example of implementation for the effectiveness and real-time of this method. The experimental results show that this method has a large advantage over the classical methods on geometric intuition, computation and real-time, and can be directly extended to all serial robot manipulators and completely automatized, which provides a new tool on the analysis and application of general robot manipulators. PMID:23918347

  17. Automatic Target Recognition in Synthetic Aperture Sonar Images Based on Geometrical Feature Extraction

    Directory of Open Access Journals (Sweden)

    J. Del Rio Vera

    2009-01-01

    Full Text Available This paper presents a new supervised classification approach for automated target recognition (ATR in SAS images. The recognition procedure starts with a novel segmentation stage based on the Hilbert transform. A number of geometrical features are then extracted and used to classify observed objects against a previously compiled database of target and non-target features. The proposed approach has been tested on a set of 1528 simulated images created by the NURC SIGMAS sonar model, achieving up to 95% classification accuracy.

  18. 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.

  19. Geometric-Process-Based Battery Management Optimizing Policy for the Electric Bus

    Directory of Open Access Journals (Sweden)

    Yan Li

    2015-01-01

    Full Text Available With the rapid development of the electric vehicle industry and promotive policies worldwide, the electric bus (E-bus has been adopted in many major cities around the world. One of the most important factors that restrain the widespread application of the E-bus is the high operating cost due to the deficient battery management. This paper proposes a geometric-process-based (GP-based battery management optimizing policy which aims to minimize the average cost of the operation on the premise of meeting the required sufficient battery availability. Considering the deterioration of the battery after repeated charging and discharging, this paper constructs the model of the operation of the E-bus battery as a geometric process, and the premaintenance time has been considered with the failure repairment time to enhance the GP-based battery operation model considering the battery cannot be as good as new after the two processes. The computer simulation is carried out by adopting the proposed optimizing policy, and the result verifies the effectiveness of the policy, denoting its significant performance on the application of the E-bus battery management.

  20. An Integrated Geometric Modeling Methodology for 2.5D Cylindrical Prismatic Part for Computer Aided Process Planning

    OpenAIRE

    Viswa Mohan Pedagopu; Manish Kumar

    2014-01-01

    The field of solid modeling has created numerous techniques for unambiguous computer representations of three-dimensional objects. Its data structures and algorithms have been used in a broad range of applications: Computer-Aided Design and Computer-Aided Manufacturing (CAD/ CAM), robotics, computer vision, computer graphics and visualization, virtual reality, etc. This research paper is used to generate process plan from feature-based modeling, based on an integrated geometric modeling syste...

  1. Managing geometric information with a data base management system

    Science.gov (United States)

    Dube, R. P.

    1984-01-01

    The strategies for managing computer based geometry are described. The computer model of geometry is the basis for communication, manipulation, and analysis of shape information. The research on integrated programs for aerospace-vehicle design (IPAD) focuses on the use of data base management system (DBMS) technology to manage engineering/manufacturing data. The objectives of IPAD is to develop a computer based engineering complex which automates the storage, management, protection, and retrieval of engineering data. In particular, this facility must manage geometry information as well as associated data. The approach taken on the IPAD project to achieve this objective is discussed. Geometry management in current systems and the approach taken in the early IPAD prototypes are examined.

  2. Modeling concepts for communication of geometric shape data

    Science.gov (United States)

    Collins, M. F.; Emnett, R. F.; Magedson, R. L.; Shu, H. H.

    1984-01-01

    ANSI5, an abbreviation for Section 5 of the American National Standard under Engineering Drawing and Related Documentation Practices (Committee Y14) on Digital Representation for Communication of Product Definition Data (ANSI Y14.26M-1981), allows encoding of a broad range of geometric shapes to be communicated through digital channels. A brief review of its underlying concepts is presented. The intent of ANSI5 is to devise a unified set of concise language formats for transmission of data pertaining to five types of geometric entities in Euclidean 3 space (E(3)). These are regarded as point like, curve like, surface like, solid like, and a combination of these types. For the first four types, ANSI5 makes a distinction between the geometry and topology. Geometry is a description of the spatial occupancy of the entity, and topology discusses the interconnectedness of the entity's boundary components.

  3. A solution to the surface intersection problem. [Boolean functions in geometric modeling

    Science.gov (United States)

    Timer, H. G.

    1977-01-01

    An application-independent geometric model within a data base framework should support the use of Boolean operators which allow the user to construct a complex model by appropriately combining a series of simple models. The use of these operators leads to the concept of implicitly and explicitly defined surfaces. With an explicitly defined model, the surface area may be computed by simply summing the surface areas of the bounding surfaces. For an implicitly defined model, the surface area computation must deal with active and inactive regions. Because the surface intersection problem involves four unknowns and its solution is a space curve, the parametric coordinates of each surface must be determined as a function of the arc length. Various subproblems involved in the general intersection problem are discussed, and the mathematical basis for their solution is presented along with a program written in FORTRAN IV for implementation on the IBM 370 TSO system.

  4. Geometric-model-free tracking of extended targets using 3D lidar measurements

    Science.gov (United States)

    Steinemann, Philipp; Klappstein, Jens; Dickmann, Juergen; von Hundelshausen, Felix; Wünsche, Hans-Joachim

    2012-06-01

    Tracking of extended targets in high definition, 360-degree 3D-LIDAR (Light Detection and Ranging) measurements is a challenging task and a current research topic. It is a key component in robotic applications, and is relevant to path planning and collision avoidance. This paper proposes a new method without a geometric model to simultaneously track and accumulate 3D-LIDAR measurements of an object. The method itself is based on a particle filter and uses an object-related local 3D grid for each object. No geometric object hypothesis is needed. Accumulation allows coping with occlusions. The prediction step of the particle filter is governed by a motion model consisting of a deterministic and a probabilistic part. Since this paper is focused on tracking ground vehicles, a bicycle model is used for the deterministic part. The probabilistic part depends on the current state of each particle. A function for calculating the current probability density function for state transition is developed. It is derived in detail and based on a database consisting of vehicle dynamics measurements over several hundreds of kilometers. The adaptive probability density function narrows down the gating area for measurement data association. The second part of the proposed method addresses weighting the particles with a cost function. Different 3D-griddependent cost functions are presented and evaluated. Evaluations with real 3D-LIDAR measurements show the performance of the proposed method. The results are also compared to ground truth data.

  5. Transformation of a Foucault shadowgram into the geometrical model of a shear interferogram by means of isophotometry

    Science.gov (United States)

    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.

  6. Geometric data transfer between CAD systems: solid models

    DEFF Research Database (Denmark)

    Kroszynski, Uri; Palstroem, Bjarne; Trostmann, Erik; Schlechtendahl, E. G.

    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...

  7. Evolution of Geometric Sensitivity Derivatives from Computer Aided Design Models

    Science.gov (United States)

    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.

  8. Intermittency in an interacting generalization of the geometric Brownian motion model

    International Nuclear Information System (INIS)

    We propose a minimal interacting generalization of the geometric Brownian motion model, which turns out to be formally equivalent to a model describing the dynamics of networks of analogue neurons. For sufficiently strong interactions, such systems may have many meta-stable states. Transitions between meta-stable states are associated with macroscopic reorganizations of the system, which can be triggered by random external forcing. Such a system will exhibit intermittent dynamics within a large part of its parameter space. We propose market dynamics as a possible application of this model, in which case random external forcing would correspond to the arrival of important information. The emergence of a model of interacting prices of the type considered here can be argued to follow naturally from a general argument based on integrating out all non-price degrees of freedom from the dynamics of a hypothetical complete description of economic dependences

  9. Modeling thermodynamic distance, curvature and fluctuations a geometric approach

    CERN Document Server

    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.

  10. Geometric Context and Orientation Map Combination for Indoor Corridor Modeling Using a Single Image

    Science.gov (United States)

    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

  11. Modeling Philippine Stock Exchange Composite Index Using Weighted Geometric Brownian Motion Forecasts

    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.

  12. Implementation of A Geometric Constraint Regularization For Multibody System Models

    Directory of Open Access Journals (Sweden)

    Müller Andreas

    2014-08-01

    Full Text Available Redundant constraints in MBS models severely deteriorate the computational performance and accuracy of any numerical MBS dynamics simulation method. Classically this problem has been addressed by means of numerical decompositions of the constraint Jacobian within numerical integration steps. Such decompositions are computationally expensive. In this paper an elimination method is discussed that only requires a single numerical decomposition within the model preprocessing step rather than during the time integration. It is based on the determination of motion spaces making use of Lie group concepts. The method is able to reduce the set of loop constraints for a large class of technical systems. In any case it always retains a sufficient number of constraints. It is derived for single kinematic loops.

  13. Geometrical properties of avalanches in self-organized critical models of solar flares

    International Nuclear Information System (INIS)

    We investigate the geometrical properties of avalanches in self-organized critical models of solar flares. Traditionally, such models differ from the classical sandpile model in their formulation of stability criteria in terms of the curvature of the nodal field, and belong to a distinct universality class. With a view toward comparing these properties to those inferred from spatially and temporally resolved flare observations, we consider the properties of avalanche peak snapshots, time-integrated avalanches in two and three dimensions, and the two-dimensional projections of the latter. The nature of the relationship between the avalanching volume and its projected area is an issue of particular interest in the solar flare context. Using our simulation results we investigate this relationship, and demonstrate that proper accounting of the fractal nature of avalanches can bring into agreement hitherto discrepant results of observational analyses based on simple, nonfractal geometries for the flaring volume

  14. Computing the laser beam path in optical cavities: a geometric Newton's method based approach

    CERN Document Server

    Cuccato, Davide; Ortolan, Antonello; Beghi, Alessandro

    2015-01-01

    In the last decade, increasing attention has been drawn to high precision optical experiments, which push resolution and accuracy of the measured quantities beyond their current limits. This challenge requires to place optical elements (e.g. mirrors, lenses, etc.) and to steer light beams with sub-nanometer precision. Existing methods for beam direction computing in resonators, e.g. iterative ray tracing or generalized ray transfer matrices, are either computationally expensive or rely on overparametrized models of optical elements. By exploiting Fermat's principle, we develop a novel method to compute the steady-state beam configurations in resonant optical cavities formed by spherical mirrors, as a function of mirror positions and curvature radii. The proposed procedure is based on the geometric Newton method on matrix manifold, a tool with second order convergence rate that relies on a second order model of the cavity optical length. As we avoid coordinates to parametrize the beam position on mirror surfac...

  15. An Improved Method for the Geometrical Calibration of Parallelogram-based Parallel Robots

    OpenAIRE

    Savoure, Ludovic; Maurine, Patrick; Corbel, David; Krut, Sébastien

    2006-01-01

    International audience This paper presents an improved method for the geometrical calibration of parallel robots for which the structure is based upon some parallelogram mechanisms. Its originality is to identify the complete geometry of the mechanism's parallelograms, and to compensate the positioning error of the TCP (Tool Centre Point), due to the infinitesimal rotation of the traveling plate, induced by the parallelogram geometrical errors. The main difficulties are: (i) to derive the ...

  16. Investigation of New Microstrip Bandpass Filter Based on Patch Resonator with Geometrical Fractal Slot.

    Science.gov (United States)

    Mezaal, Yaqeen S; Eyyuboglu, Halil T

    2016-01-01

    A compact dual-mode microstrip bandpass filter using geometrical slot is presented in this paper. The adopted geometrical slot is based on first iteration of Cantor square fractal curve. This filter has the benefits of possessing narrower and sharper frequency responses as compared to microstrip filters that use single mode resonators and traditional dual-mode square patch resonators. The filter has been modeled and demonstrated by Microwave Office EM simulator designed at a resonant frequency of 2 GHz using a substrate of εr = 10.8 and thickness of h = 1.27 mm. The output simulated results of the proposed filter exhibit 22 dB return loss, 0.1678 dB insertion loss and 12 MHz bandwidth in the passband region. In addition to the narrow band gained, miniaturization properties as well as weakened spurious frequency responses and blocked second harmonic frequency in out of band regions have been acquired. Filter parameters including insertion loss, return loss, bandwidth, coupling coefficient and external quality factor have been compared with different values of perturbation dimension (d). Also, a full comparative study of this filter as compared with traditional square patch filter has been considered. PMID:27054755

  17. Assembly goal inference using geometric modeling facilities of EusLisp

    International Nuclear Information System (INIS)

    In order for an assembly planner to generate assembling sequences, the goal state which describes locations and orientations of each component in the assembly must be given. However, specifying 6 translational and rotational coordinates for each of them is a delicate and error-prone task for mechanical assembly designers. What we propose in this paper is a way to automatically infer those parameters in a plausible goal state. The planner generates candidates of combination of two parts based on fastenermatching and cylindrical matching and evaluates their utilities by interference, area of contact, and degrees of freedom constrained. A realistic demonstration of this method is shown using an assembly of a model aircraft engine. Geometric modeling facilities of the robot-oriented programming language, EusLisp, which enabled above application, is also discussed. (author)

  18. Modeling a geometric locus problem with GeoGebra

    Directory of Open Access Journals (Sweden)

    Gabriela-Simona Antohe

    2009-01-01

    Full Text Available În rezolvarea unor probleme de loc geometric analiza, modelarea, studiul cazurilor particulare ce ajută la intuirea soluţiei poate atrage din partea rezolvitorului un efort de lungă durata. În acest sens, folosirea unor programe specializate pentru modelarea unor fenomene matematice, în genere transformări geometrice în plan, este un instrument acceptat şi folosit din ce în ce mai mult. În cadrul lecţiilor de predare-învăţare a matematicii, implementarea investigaţiei desfăşurată pe platforme de geometrie dinamică precum Geogebra poate atrage definirea unor noi metode de predare-învăţare “nonstandard”, metode ce sunt acceptate ca metode de graniţă ce folosesc instrumentul informatic în strânsă legătură cu demersul matematic al metodelor clasice. Vom numi acest demers “infogeometria dinamică”.

  19. The Data Transfer Kit: A geometric rendezvous-based tool for multiphysics data transfer

    International Nuclear Information System (INIS)

    The Data Transfer Kit (DTK) is a software library designed to provide parallel data transfer services for arbitrary physics components based on the concept of geometric rendezvous. The rendezvous algorithm provides a means to geometrically correlate two geometric domains that may be arbitrarily decomposed in a parallel simulation. By repartitioning both domains such that they have the same geometric domain on each parallel process, efficient and load balanced search operations and data transfer can be performed at a desirable algorithmic time complexity with low communication overhead relative to other types of mapping algorithms. With the increased development efforts in multiphysics simulation and other multiple mesh and geometry problems, generating parallel topology maps for transferring fields and other data between geometric domains is a common operation. The algorithms used to generate parallel topology maps based on the concept of geometric rendezvous as implemented in DTK are described with an example using a conjugate heat transfer calculation and thermal coupling with a neutronics code. In addition, we provide the results of initial scaling studies performed on the Jaguar Cray XK6 system at Oak Ridge National Laboratory for a worse-case-scenario problem in terms of algorithmic complexity that shows good scaling on 0(1 x 104) cores for topology map generation and excellent scaling on 0(1 x 105) cores for the data transfer operation with meshes of O(1 x 109) elements. (authors)

  20. Effective Hydraulic Conductivity Scaling in a 2-Dimensional Geometrical Multifractal Model for Aquifer Heterogeneity

    Science.gov (United States)

    Gentry, R. W.; Perfect, E.; Sukop, M. C.

    2005-12-01

    Recent analyses of field data suggest that the spatial variation of hydraulic conductivity, K, within an aquifer may be multifractal. We investigated the implications of this finding for the scaling of effective hydraulic conductivity, , by performing numerical simulations of flow in 2-dimensional geometrical multifractal K fields. A theoretical framework for generating such fields is presented based on the parameters of the truncated binomial distribution, TBD. This leads to an approximate analytical expression showing that increases with increasing length scale as a power law, whose exponent, α, is determined by the TBD parameters. Five geometrical multifractal K fields were generated with different minimum length scales. Each domain was discretized using a block center grid consisting of 59,049 uniformly-spaced nodes. A unit cube aquifer was used for the numerical simulations. The boundary conditions were implemented with constant head (unit gradient) parallel planes, and corresponding zero flux planes on the normal axes. A finite difference simulation model based on MODFLOW 2000 was used, and "zone budget" was employed to calculate the flow balance. The discharge into and out of the unit cube was then used to calculate based on Darcy's law. The numerical simulations produced similar increases in with increasing length scale to those predicted by the analytical model. Nonlinear regression analyses yielded estimates of α from the numerical simulations that were within 10% of the analytical value for these fields. These simulations provide a theoretical explanation for effective hydraulic conductivity scaling in terms of multifractals. The advantage of such an approach is that the α-parameter, which controls the degree of scaling, is physically-based and can potentially be estimated from independent measurements.

  1. Automatic registration of geometric distortions in satellite images based on control points

    International Nuclear Information System (INIS)

    This paper presents an automatic registration scheme to register geometric distortion in satellite images; A novel feature based matching scheme is proposed which establishes correspondence between the corner points in the reference and target images either by correlating the intensity values around a circular neighborhood of these corner points or by exploiting the relative orientation of lines connecting these corner points. Affine transformation model is used to estimate transformation parameters. Re-sampling is carried out by nearest neighborhood interpolation. The registration process is automatic and can efficiently serve as preprocessing stage for multitemporal analysis, image fusion, image mosaicking and change detection. The effectiveness of the algorithm has been verified by an intensive experiment on a large number of real images. Experimental results reveal high supremacy of the proposed registration method. (author)

  2. Deformation of a Circular Elastic Tube between Two Parallel Bars: Quasi-Analytical Geometrical Ring Models

    Directory of Open Access Journals (Sweden)

    A. Van Hirtum

    2015-01-01

    Full Text Available Several engineering problems are confronted with elastic tubes. In the current work, homothetic quasi-analytical geometrical ring models, ellipse, stadium, and peanut, are formulated allowing a computationally low cost ring shape estimation as a function of a single parameter, that is, the pinching degree. The dynamics of main geometrical parameters due to the model choice is discussed. Next, the ring models are applied to each cross section of a circular elastic tube compressed between two parallel bars for pinching efforts between 40% and 95%. The characteristic error yields less than 4% of the tubes diameter when the stadium model was used.

  3. Geometric evaluation of SPOT5 image using rigorous sensor model and simple polynomial direct location model

    Science.gov (United States)

    Yan, Dongmei; Wang, Fenfei; Kou, Tianyou; Chen, Shirong

    2010-11-01

    With the start tracker and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), SPOT5 satellite point positioning error is lower than 50m. In this paper, two terrains, mountainous areas and plain areas, are defined by terrain gradient. The ground check points are chosen on these terrains with the geometric error and the elevation error both lower than 1m. The coordinate in UTM of each point is calculated both in the Rigorous Sensor Model and the Simple Polynomial Direct Location Model, and the differences between the computed coordinates and the surveyed coordinates are discussed. According to the experiment results, the two models have their own advantage in different circumstances. In mountainous areas, the Rigorous Sensor Model can get higher location accuracy. In plain areas, the two models can locate with same accuracy, but the Simple Polynomial Direct Location Model performs better in the aspect of speed and the simplicity.

  4. METHOD FOR ADAPTIVE MESH GENERATION BASED ON GEOMETRICAL FEATURES OF 3D SOLID

    Institute of Scientific and Technical Information of China (English)

    HUANG Xiaodong; DU Qungui; YE Bangyan

    2006-01-01

    In order to provide a guidance to specify the element size dynamically during adaptive finite element mesh generation, adaptive criteria are firstly defined according to the relationships between the geometrical features and the elements of 3D solid. Various modes based on different datum geometrical elements, such as vertex, curve, surface, and so on, are then designed for generating local refmed mesh. With the guidance of the defined criteria, different modes are automatically selected to apply on the appropriate datum objects to program the element size in the local special areas. As a result, the control information of element size is successfully programmed coveting the entire domain based on the geometrical features of 3D solid. A new algorithm based on Delaunay triangulation is then developed for generating 3D adaptive fmite element mesh, in which the element size is dynamically specified to catch the geometrical features and suitable tetrahedron facets are selected to locate interior nodes continuously. As a result, adaptive mesh with good-quality elements is generated. Examples show that the proposed method can be successfully applied to adaptive finite element mesh automatic generation based on the geometrical features of 3D solid.

  5. Analysis of Geometric Primitives in Quantitative Structure Models of Tree Stems

    Directory of Open Access Journals (Sweden)

    Åkerblom Markku

    2015-04-01

    Full Text Available One way to model a tree is to use a collection of geometric primitives to represent the surface and topology of the stem and branches of a tree. The circular cylinder is often used as the geometric primitive, but it is not the only possible choice. We investigate various geometric primitives and modelling schemes, discuss their properties and give practical estimates for expected modelling errors associated with the primitives. We find that the circular cylinder is the most robust primitive in the sense of a well-bounded volumetric modelling error, even with noise and gaps in the data. Its use does not cause errors significantly larger than those with more complex primitives, while the latter are much more sensitive to data quality. However, in some cases, a hybrid approach with more complex primitives for the stem is useful.

  6. A geometrical representation of the interacting-boson model of nuclei

    International Nuclear Information System (INIS)

    The representation of the interacting-boson-model Hamiltonian as a second-order differential operator in geometrical variables is studied in detail. It is shown that, with appropriate boundary conditions and biorthogonal weight functions, it reproduces exactly both the spectrum and matrix elements of operators of the algebraic boson model. It can be written in self-adjoint form and expanded in a symmetrized moment expansion, allowing the identification of collective mass parameters and energy surfaces, but differs in detail from conventional geometrical collective model. (author)

  7. Photo-Crosslinking Induced Geometric Restriction Controls the Self-Assembly of Diphenylalanine Based Peptides

    Institute of Scientific and Technical Information of China (English)

    TIE Zuo-Xiu; QIN Meng; ZOU Da-Wei; CAO Yi; WANG Wei

    2011-01-01

    @@ The diphenylalanine (FF) motif has been widely used in the design of peptides that are capable of forming various ordered structures, such as nanotubes, nanospheres and hydrogels.In these assemblies, FF based peptides adopt an antiparallel structure and are stabilized by n - TT stacking among the phenyl groups.Here we show that assembly of FF-based peptides can be controlled by their geometric restrictions.Using tripeptide FFY (L-Phe-L-Phe-L-Tyr) as an example, we demonstrate that photo-crosslinking of C-terminal tyrosine can impose a geometric restriction to the formation of an antiparallel structure, leading to a structural change of the assemblies from nanosphere to amorphous.%The diphenylalanine (FF) motif has been widely used in the design of peptides that are capable of forming various ordered structures, such as nanotubes, nanospheres and hydrogels. In these assemblies, FF based peptides adopt an antiparallel structure and are stabilized by π - π stacking among the phenyl groups. Here we show that assembly of FF-based peptides can be controlled by their geometric restrictions. Using tripeptide FFY (L-Phe-L-Phe-L-Tyr) as an example, we demonstrate that photo-crosslinking of C-terminal tyrosine can impose a geometric restriction to the formation of an antiparallel structure, leading to a structural change of the assemblies from nanosphere to amorphous. This finding is confirmed using far-UV circular dichroism, Fourier transform infrared spectroscopy and atomic force microscopy. Based on such a mechanism, we are able to control the gel-sol transition of Fmoc-FFY using the geometric restriction induced by photo-crosslinking of C-terminal tyrosine groups. We believe that geometric restriction should be considered as an important factor in the design of peptide-based materials. It can also be implemented as a useful strategy for the construction of environment-responsive “smart”materials.

  8. Geometrical Standard Model Enhancements to the Standard Model of Particle Physics

    Science.gov (United States)

    Strickland, Ken; Duvernois, Michael

    2011-10-01

    The Standard Model (SM) is the triumph of our age. As experimentation at the LHC tracks particles for the Higgs phenomena, theoreticians and experimentalist struggle to close in on a cohesive theory. Both suffer greatly as expectation waivers those who seek to move beyond the SM and those who cannot do without. When it seems like there are no more good ideas enter Rate Change Graph Technology (RCGT). From the science of the rate change graph, a Geometrical Standard Model (GSM) is available for comprehensive modeling, giving rich new sources of data and pathways to those ultimate answers we punish ourselves to achieve. As a new addition to science, GSM is a tool that provides a structured discovery and analysis environment. By eliminating value and size, RCGT operates with the rules of RCGT mechanics creating solutions derived from geometry. The GSM rate change graph could be the ultimate validation of the Standard Model yet. In its own right, GSM is created from geometrical intersections and comes with RCGT mechanics, yet parallels the SM to offer critical enhancements. The Higgs Objects along with a host of new objects are introduced to the SM and their positions revealed in this proposed modification to the SM.

  9. MAP: Medial axis based geometric routing in sensor networks

    OpenAIRE

    Bruck, Jehoshua; Gao, Jie; Jiang, Anxiao

    2007-01-01

    One of the challenging tasks in the deployment of dense wireless networks (like sensor networks) is in devising a routing scheme for node to node communication. Important consideration includes scalability, routing complexity, quality of communication paths and the load sharing of the routes. In this paper, we show that a compact and expressive abstraction of network connectivity by the medial axis enables efficient and localized routing. We propose MAP, a Medial Axis based naming and routing...

  10. Dynamic modeling of geometrically nonlinear electrostatically actuated microbeams (Corotational Finite Element formulation and analysis)

    International Nuclear Information System (INIS)

    In this paper, a complete nonlinear finite element model for coupled-domain MEMS devices with electrostatic actuation and squeeze film effect is developed. For this purpose, a corotational finite element formulation for the dynamic analysis of planer Euler beams is employed. In this method, the internal nodal forces due to deformation and intrinsic residual stresses, the inertial nodal forces, and the damping effect of squeezed air film are systematically derived by consistent linearization of the fully geometrically nonlinear beam theory using d'Alamber and virtual work principles. An incremental-iterative method based on the Newmark direct integration procedure and the Newton-Raphson algorithm is used to solve the nonlinear dynamic equilibrium equations. Numerical examples are presented and compared with experimental findings which indicate properly good agreement

  11. Parametric geometric model and shape optimization of an underwater glider with blended-wing-body

    Science.gov (United States)

    Sun, Chunya; Song, Baowei; Wang, Peng

    2015-11-01

    Underwater glider, as a new kind of autonomous underwater vehicles, has many merits such as long-range, extended-duration and low costs. The shape of underwater glider is an important factor in determining the hydrodynamic efficiency. In this paper, a high lift to drag ratio configuration, the Blended-Wing-Body (BWB), is used to design a small civilian under water glider. In the parametric geometric model of the BWB underwater glider, the planform is defined with Bezier curve and linear line, and the section is defined with symmetrical airfoil NACA 0012. Computational investigations are carried out to study the hydrodynamic performance of the glider using the commercial Computational Fluid Dynamics (CFD) code Fluent. The Kriging-based genetic algorithm, called Efficient Global Optimization (EGO), is applied to hydrodynamic design optimization. The result demonstrates that the BWB underwater glider has excellent hydrodynamic performance, and the lift to drag ratio of initial design is increased by 7% in the EGO process.

  12. 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 and...

  13. A modified interval subdividing based geometric calibration method for interior tomography

    International Nuclear Information System (INIS)

    The interior tomography is commonly met in practice, whereas the self-calibration method for geometric parameters remains far from explored. To determine the geometry of interior tomography, a modified interval subdividing based method, which was originally developed by Tan et al.,[11] was presented in this paper. For the self-calibration method, it is necessary to obtain the reconstructed image with only geometric artifacts. Therefore, truncation artifacts reduction is a key problem for the self-calibration method of an interior tomography. In the method, an interior reconstruction algorithm instead of the Feldkamp—Davis—Kress (FDK) algorithm was employed for truncation artifact reduction. Moreover, the concept of a minimum interval was defined as the stop criterion of subdividing to ensure the geometric parameters are determined nicely. The results of numerical simulation demonstrated that our method could provide a solution to the self-calibration for interior tomography while the original interval subdividing based method could not. Furthermore, real data experiment results showed that our method could significantly suppress geometric artifacts and obtain high quality images for interior tomography with less imaging cost and faster speed compared with the traditional geometric calibration method with a dedicated calibration phantom. (interdisciplinary physics and related areas of science and technology)

  14. Models for determining the geometrical properties of halo coronal mass ejections

    Science.gov (United States)

    Zhao, X.; Liu, Y.

    2005-12-01

    To this day, the prediction of space weather effects near the Earth suffer from a fundamental problem: the necessary condition for determining whether or not and when a part of the huge interplanetary counterpart (ICME) of frontside halo coronal mass ejections (CMEs) is able to hit the Earth and generate goemagnetic storms, i.e., the real angular width, the propagation direction and speed of the CMEs, cannot be measured directly because of the unfavorable geometry. To inverse these geometrical and kinematical properties we have recently developed a few geometrical models, such as the cone model, the ice cream cone model, and the spherical cone model. The inversing solution of the cone model for the 12 may 1997 halo CME has been used as an input to the ENLIL model (a 3D MHD solar wind code) and successfully predicted the ICME near the Earth (Zhao, Plukett & Liu, 2002; Odstrcil, Riley & Zhao, 2004). After briefly describing the geometrical models this presentation will discuss: 1. What kind of halo CMEs can be inversed? 2. How to select the geometrical models given a specific halo CME? 3. Whether or not the inversing solution is unique?

  15. A geometrical model for the Monte Carlo simulation of the TrueBeam linac

    International Nuclear Information System (INIS)

    Monte Carlo simulation of linear accelerators (linacs) depends on the accurate geometrical description of the linac head. The geometry of the Varian TrueBeam linac is not available to researchers. Instead, the company distributes phase-space files of the flattening-filter-free (FFF) beams tallied at a plane located just upstream of the jaws. Yet, Monte Carlo simulations based on third-party tallied phase spaces are subject to limitations. In this work, an experimentally based geometry developed for the simulation of the FFF beams of the Varian TrueBeam linac is presented. The Monte Carlo geometrical model of the TrueBeam linac uses information provided by Varian that reveals large similarities between the TrueBeam machine and the Clinac 2100 downstream of the jaws. Thus, the upper part of the TrueBeam linac was modeled by introducing modifications to the Varian Clinac 2100 linac geometry. The most important of these modifications is the replacement of the standard flattening filters by ad hoc thin filters. These filters were modeled by comparing dose measurements and simulations. The experimental dose profiles for the 6 MV and 10 MV FFF beams were obtained from the Varian Golden Data Set and from in-house measurements performed with a diode detector for radiation fields ranging from 3  ×  3 to 40  ×  40 cm2 at depths of maximum dose of 5 and 10 cm. Indicators of agreement between the experimental data and the simulation results obtained with the proposed geometrical model were the dose differences, the root-mean-square error and the gamma index. The same comparisons were performed for dose profiles obtained from Monte Carlo simulations using the phase-space files distributed by Varian for the TrueBeam linac as the sources of particles. Results of comparisons show a good agreement of the dose for the ansatz geometry similar to that obtained for the simulations with the TrueBeam phase-space files for all fields and depths considered, except for the

  16. 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.

  17. Difference Energy Based Blind Image Watermarking Resisting to Geometrical Distortions

    Institute of Scientific and Technical Information of China (English)

    YU Yanwei; LU Zhengding; LING Hefei

    2006-01-01

    In this paper a blind image watermarking that can resist to rotation, scaling and translation (RST) attacks is proposed. Based on the spread spectrum, the watermark is modulated before embedding. The log-polar mapped discrete fourier transform (LPM-DFT) magnitude of a disk, a part of the origin image, constitutes the RST-invariant domain, where the origin of the LPM is the center of the disk and the sampling rates of the LPM are constant. After the middle frequency band of LPM-DFT magnitude, namely the watermark-embedding domain, is grouped according to the watermark length, the watermark is embedded by adjusting the difference between the two sub-region energy in each group. To improve the imperceptibility, the watermark-embedding domain is shuffled before embedding and the watermark is not embedded directly into the watermark-embedding domain. In watermark detection procedure, neither the original image nor any knowledge about the distortions is required. Experimental results show that the proposed scheme is very robust against RST distortion and common image processing attacks.

  18. A geometrical and physical nonlinear finite element model for spatial thin-walled beams with arbitrary section

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Based on the theories of Bernoulli-Euler beams and Vlasov’s thin-walled members,a new geometrical and physical nonlinear beam element model is developed by applying an interior node in the element and independent interpolations on bending angles and warp,in which factors such as traverse shear deformation,torsional shear deformation and their coupling,coupling of flexure and torsion,and second shear stress are all considered.Thereafter,geometrical nonlinear strain in total Lagarange(TL) and the corresponding stiffness matrix are formulated.Ideal plastic model is applied to physical nonlinearity to comply with the yield rule of Von Mises and incremental relationship of Prandtle-Reuss.Elastoplastic stiffness matrix is derived by numerical integration on the basis of the finite segment method.Examples show that the developed model is feasible in analysis of thin-walled structures with high accuracy.

  19. Geometric analysis of the capital asset pricing model

    OpenAIRE

    Kure, Thomas

    2010-01-01

    The derivation of the capital asset pricing model is in most literature limited to a graphical analysis. Since this method avoids a complicated mathematical framework the derivation is more intuitive to people who are unfamiliar to this topic. This approach, however, can result in misleading or even wrong results if the analysis is imprecise. Some of the main mistakes seem to be already established in financial textbooks. This thesis gives a deeper analysis of the so often used ...

  20. Circumventing Imprecise Geometric Information and Development of a Unified Modeling Technique for Various Flow Regimes in Capillary Tubes

    Science.gov (United States)

    Abbasi, Bahman

    2012-11-01

    Owing to their manufacturability and reliability, capillary tubes are the most common expansion devices in household refrigerators. Therefore, investigating flow properties in the capillary tubes is of immense appeal in the said business. The models to predict pressure drop in two-phase internal flows invariably rely upon highly precise geometric information. The manner in which capillary tubes are manufactured makes them highly susceptible to geometric imprecisions, which renders geometry-based models unreliable to the point of obsoleteness. Aware of the issue, manufacturers categorize capillary tubes based on Nitrogen flow rate through them. This categorization method presents an opportunity to substitute geometric details with Nitrogen flow data as the basis for customized models. The simulation tools developed by implementation of this technique have the singular advantage of being applicable across flow regimes. Thus the error-prone process of identifying compatible correlations is eliminated. Equally importantly, compressibility and chocking effects can be incorporated in the same model. The outcome is a standalone correlation that provides accurate predictions, regardless of any particular fluid or flow regime. Thereby, exploratory investigations for capillary tube design and optimization are greatly simplified. Bahman Abbasi, Ph.D., is Lead Advanced Systems Engineer at General Electric Appliances in Louisville, KY. He conducts research projects across disciplines in the household refrigeration industry.

  1. GEOMETRICAL MODELING OF 3D PATTERNS FOR TRADITIONAL INDIAN KUNDAN JEWELRY

    Directory of Open Access Journals (Sweden)

    GOEL VINEET KUMAR

    2011-07-01

    Full Text Available India is famous for its art and culture, which can be found in traditional handicrafts, carvings, potteries, as well as in Jewelry. The traditional Jewelry of India is what makes the Indian Jewelry so rich and unique in their manner. India has a rich tradition of gold ornamental designs and there are a number of styles of ornamentmaking in practice, each with its uniqueness, special forms and style. Our work is based on semantics; 3D patterns are created on the bases of parametric representation. This work aims to associate advantages unfolded by Computer Aided Design (CAD technology in developing traditional design patterns for Jewelry design andmanufacturing. The work also presents three dimensional (3D semantics used in Traditional Indian Kundan Jewelry with the help of mathematical modeling; to generate the traditional patterns.The goal will be achieved by devising mathematical models for various 3D semantics, for the modeling of Traditional Indian Kundan jewelry (TIKJ. Jewelry Add-In is developed for inventor using c++. Aim of this Jewelry add-in is to develop pattern of 3D geometrical shapes on 3D surface and for communication between Jewelry Add-In and Inventor.

  2. Country neighborhood network on territory and its geometrical model

    Science.gov (United States)

    Xuan, Qi; Wu, Tie-Jun

    2009-04-01

    The country neighborhood network, where nodes represent countries and two nodes are considered linked if the corresponding countries are neighbors on territory, is created and its giant component, the Asia, Europe, and Africa (AEA) cluster, is carefully studied in this paper. It is found that, as common, the degree distribution and the clustering function of the AEA cluster are both compatible with scale-free property, besides, the AEA cluster presents a little disassortativity, and its near power-law country area-degree relationship with the exponent close to 1.7 may imply a fractal dimension close to 1.2 of country borderlines in the AEA continent. It is also revealed that the average difference of population density between two countries obeys an approximately increasing function of the shortest path length between them, which may suggest a gradual consensus of population density in the AEA cluster. A simple unity rule is then adopted to model the AEA cluster and such model explains the AEA cluster very well in most aspects, e.g., power-law domain area distribution and fractal domain borderlines, etc., except that the network derived by the model has stronger disassortativity, which may be explained by the fact that, in the evolution history of countries, unbalanced neighbors are more likely to be united as one than balanced neighbors. Additionally, the network evolving process can be divided into three periods, defined as formation period, growth period, and combination period, and there are indications that the AEA cluster is in its third period.

  3. The Effect of Origami-Based Instruction on Spatial Visualization, Geometry Achievement, and Geometric Reasoning

    Science.gov (United States)

    Arici, Sevil; Aslan-Tutak, Fatma

    2015-01-01

    This research study examined the effect of origami-based geometry instruction on spatial visualization, geometry achievement, and geometric reasoning of tenth-grade students in Turkey. The sample ("n" = 184) was chosen from a tenth-grade population of a public high school in Turkey. It was a quasi-experimental pretest/posttest design. A…

  4. Photo-Crosslinking Induced Geometric Restriction Controls the Self-Assembly of Diphenylalanine Based Peptides

    International Nuclear Information System (INIS)

    The diphenylalanine (FF) motif has been widely used in the design of peptides that are capable of forming various ordered structures, such as nanotubes, nanospheres and hydrogels. In these assemblies, FF based peptides adopt an antiparallel structure and are stabilized by π — π stacking among the phenyl groups. Here we show that assembly of FF-based peptides can be controlled by their geometric restrictions. Using tripeptide FFY (L-Phe-L-Phe-L-Tyr) as an example, we demonstrate that photo-crosslinking of C-terminal tyrosine can impose a geometric restriction to the formation of an antiparallel structure, leading to a structural change of the assemblies from nanosphere to amorphous. This finding is confirmed using far-UV circular dichroism, Fourier transform infrared spectroscopy and atomic force microscopy. Based on such a mechanism, we are able to control the gel-sol transition of Fmoc-FFY using the geometric restriction induced by photo-crosslinking of C-terminal tyrosine groups. We believe that geometric restriction should be considered as an important factor in the design of peptide-based materials. It can also be implemented as a useful strategy for the construction of environment-responsive 'smart' materials. (cross-disciplinary physics and related areas of science and technology)

  5. Photo-Crosslinking Induced Geometric Restriction Controls the Self-Assembly of Diphenylalanine Based Peptides

    Science.gov (United States)

    Tie, Zuo-Xiu; Qin, Meng; Zou, Da-Wei; Cao, Yi; Wang, Wei

    2011-02-01

    The diphenylalanine (FF) motif has been widely used in the design of peptides that are capable of forming various ordered structures, such as nanotubes, nanospheres and hydrogels. In these assemblies, FF based peptides adopt an antiparallel structure and are stabilized by π — π stacking among the phenyl groups. Here we show that assembly of FF-based peptides can be controlled by their geometric restrictions. Using tripeptide FFY (L-Phe-L-Phe-L-Tyr) as an example, we demonstrate that photo-crosslinking of C-terminal tyrosine can impose a geometric restriction to the formation of an antiparallel structure, leading to a structural change of the assemblies from nanosphere to amorphous. This finding is confirmed using far-UV circular dichroism, Fourier transform infrared spectroscopy and atomic force microscopy. Based on such a mechanism, we are able to control the gel-sol transition of Fmoc-FFY using the geometric restriction induced by photo-crosslinking of C-terminal tyrosine groups. We believe that geometric restriction should be considered as an important factor in the design of peptide-based materials. It can also be implemented as a useful strategy for the construction of environment-responsive “smart" materials.

  6. Photo-crosslinking induced geometric restriction controls the self-assembly of diphenylalanine based peptides

    International Nuclear Information System (INIS)

    The diphenylalanine (FF) motif has been widely used in the design of peptides that are capable of forming various ordered structures, such as nanotubes, nanospheres and hydrogels. In these assemblies, FF based peptides adopt an antiparallel structure and are stabilized by π-π stacking among the phenyl groups. Here we show that assembly of FF-based peptides can be controlled by their geometric restrictions. Using tripeptide FFY (L-Phe-L-Phe-L-Tyr) as an example, we demonstrate that photo-crosslinking of C-terminal tyrosine can impose a geometric restriction to the formation of an antiparallel structure, leading to a structural change of the assemblies from nanosphere to amorphous. This finding is confirmed using far-UV circular dichroism, Fourier transform infrared spectroscopy and atomic force microscopy. Based on such a mechanism, we are able to control the gel-sol transition of Fmoc-FFY using the geometric restriction induced by photo-crosslinking of C-terminal tyrosine groups. We believe that geometric restriction should be considered as an important factor in the design of peptide-based materials. It can also be implemented as a useful strategy for the construction of environment-responsive 'smart' materials. (authors)

  7. Geometric and Dynamical Models of Reverberation Mapping Data

    CERN Document Server

    Pancoast, Anna; Treu, Tommaso

    2011-01-01

    We present a general method to analyze reverberation mapping data that provides both estimates for the black hole mass and for the geometry and dynamics of the broad line region (BLR) in active galactic nuclei (AGN). Our method directly infers the spatial and velocity distribution of the BLR from the data, allowing us to easily derive a velocity-resolved transfer function and allowing for a self-consistent estimate of the black hole mass without a virial coefficient. We obtain estimates and reasonable uncertainties of the BLR model parameters by implementing a Markov Chain Monte Carlo algorithm using the formalism of Bayesian probability theory. We use Gaussian Processes to interpolate the the continuum light curve data and create mock light curves that can be fitted to the data. We test our method by creating simulated reverberation mapping data-sets with known true parameter values and by trying to recover these parameter values using our models. We are able to recover the parameters with realistic uncertai...

  8. PET-based geometrical calibration of a pinhole SPECT add-on for an animal PET scanner

    International Nuclear Information System (INIS)

    We developed SPECT imaging capability on an animal PET scanner to provide a cost effective option for animal SPECT imaging. The SPECT add-on sub-system was enabled by mechanically integrating a multiple-pinhole collimator in the PET detector ring. This study introduces a method to calibrate the geometrical parameters of the SPECT add-on using the PET imaging capability of the scanner. The proposed PET imaging-based calibration method consists of two steps: (1) paint the pinhole apertures of the collimator with a positron emitting radioactive solution; and (2) image the collimator inside the scanner in PET mode. The geometrical parameters of the multi-pinhole SPECT add-on can then be derived directly from a set of PET images by simple linear calculation and used in defining the SPECT system. The method was compared to our implementation of a SPECT calibration approach with model-based fitting of SPECT projection data. The procedure for carrying out the PET imaging-based calibration method is simpler and faster than that of our implementation of the SPECT model-based calibration method. Since it does not require model fitting, the uniqueness of the calibration result is warranted. Better quality SPECT images were reconstructed using the PET-derived calibration parameters rather than our implementation of the SPECT model-based calibration parameters. We conclude that the proposed PET imaging-based calibration method provides a highly effective means for enabling SPECT imaging on a PET scanner. (paper)

  9. Numerical Methods for a Multicomponent Two-Phase Interface Model with Geometric Mean Influence Parameters

    KAUST Repository

    Kou, Jisheng

    2015-07-16

    In this paper, we consider an interface model for multicomponent two-phase fluids with geometric mean influence parameters, which is popularly used to model and predict surface tension in practical applications. For this model, there are two major challenges in theoretical analysis and numerical simulation: the first one is that the influence parameter matrix is not positive definite; the second one is the complicated structure of the energy function, which requires us to find out a physically consistent treatment. To overcome these two challenging problems, we reduce the formulation of the energy function by employing a linear transformation and a weighted molar density, and furthermore, we propose a local minimum grand potential energy condition to establish the relation between the weighted molar density and mixture compositions. From this, we prove the existence of the solution under proper conditions and prove the maximum principle of the weighted molar density. For numerical simulation, we propose a modified Newton\\'s method for solving this nonlinear model and analyze its properties; we also analyze a finite element method with a physical-based adaptive mesh-refinement technique. Numerical examples are tested to verify the theoretical results and the efficiency of the proposed methods.

  10. Collaborative spectrum sensing based on the ratio between largest eigenvalue and Geometric mean of eigenvalues

    KAUST Repository

    Shakir, Muhammad

    2011-12-01

    In this paper, we introduce a new detector referred to as Geometric mean detector (GEMD) which is based on the ratio of the largest eigenvalue to the Geometric mean of the eigenvalues for collaborative spectrum sensing. The decision threshold has been derived by employing Gaussian approximation approach. In this approach, the two random variables, i.e. The largest eigenvalue and the Geometric mean of the eigenvalues are considered as independent Gaussian random variables such that their cumulative distribution functions (CDFs) are approximated by a univariate Gaussian distribution function for any number of cooperating secondary users and received samples. The approximation approach is based on the calculation of exact analytical moments of the largest eigenvalue and the Geometric mean of the eigenvalues of the received covariance matrix. The decision threshold has been calculated by exploiting the CDF of the ratio of two Gaussian distributed random variables. In this context, we exchange the analytical moments of the two random variables with the moments of the Gaussian distribution function. The performance of the detector is compared with the performance of the energy detector and eigenvalue ratio detector. Analytical and simulation results show that our newly proposed detector yields considerable performance advantage in realistic spectrum sensing scenarios. Moreover, our results based on proposed approximation approach are in perfect agreement with the empirical results. © 2011 IEEE.

  11. Geometric mechanics for modelling bioinspired robots locomotion: from rigid to continuous (soft) systems

    Science.gov (United States)

    Boyer, Frederic; Porez, Mathieu; Renda, Federico

    This talk presents recent geometric tools developed to model the locomotion dynamics of bio-inspired robots. Starting from the model of discrete rigid multibody systems we will rapidly shift to the case of continuous systems inspired from snakes and fish. To that end, we will build on the model of Cosserat media. This extended picture of geometric locomotion dynamics (inspired from fields' theory) will allow us to introduce models of swimming recently used in biorobotics. We will show how modeling a fish as a one-dimensional Cosserat medium allows to recover and extend the Large Amplitude Elongated Body theory of J. Lighthill and to apply it to an eel-like robot. In the same vein, modeling the mantle of cephalopods as a two dimensional Cosserat medium will build a basis for studying the jet propelling of a soft octopus like robot.

  12. Physical modeling of geometrically confined disordered protein assemblies

    Science.gov (United States)

    Ando, David

    The mental health of soldiers is a growing concern as rates of depression and suicide have increased in soldiers with recently more deaths attributed to suicide than deaths due to combat in Afghanistan in 2012. Previous research has demonstrated the potential for eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), vitamin D, physical activity, and physical fitness to improve and arachidonic acid (AA) to threaten depression/quality of life scores. This study examined whether blood fatty acid levels, vitamin D status and/or physical activity are associated with physical fitness scores, measures of mood, and measures of resiliency in active duty soldiers. 100 active duty males at Fort Hood, TX underwent a battery of psychometric tests, anthropometric, fitness tests, and donated fasting blood samples. Pearson bivariate correlation analysis revealed significant correlations among psychometric tests, anthropometric, physical performance, reported physical inactivity (sitting time), and fatty acid and vitamin D blood levels. Categorical analysis revealed significant difference in levels of fatty acids and vitamin D, anthropometric, physical performance, and psychometric measures. Based on these findings, a regression equation was developed to predict a depressed mood status as determined by the Patient Health Questionnaire-9. The equation accurately predicted 80% of our participants with a sensitivity of 76.9% and a specificity of 80.5%. Results indicate that lack of physical activity and fitness, high levels of AA and low levels of EPA, DHA, and vitamin D could increase the risk of depressed mood and that use of a regression equation may be helpful in identifying soldiers at higher risk for possible intervention. Future studies should evaluate the impact of exercise and diet interventions as a means of improving resiliency and reducing depressed mood in soldiers.

  13. On the geometrical interpretation of scale-invariant models of inflation

    CERN Document Server

    Karananas, Georgios K

    2016-01-01

    We study the geometrical properties of scale-invariant two-field models of inflation. In particular, we show that when the field-derivative space in the Einstein frame is maximally symmetric during inflation, the inflationary predictions can be universal and independent of the details of the theory.

  14. Influence of the FLUKA geometrical model on the ADS demonstration facility criticality calculations

    International Nuclear Information System (INIS)

    Criticality calculations for a typical ADS have been performed by means of the codes chain FLUKA-CMCS (formerly FLUKA - MC2). the FLUKA code calculates the neutron source for the subsequent neutron transport calculations performed by CMCS. In this paper it is investigated how the geometrical model used in FLUKA can impact the CMCS criticality calculations. (orig.)

  15. 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 irregul...

  16. Optimal control for mathematical models of cancer therapies an application of geometric methods

    CERN Document Server

    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.

  17. Modeling photosynthesis of discontinuous plant canopies by linking Geometric Optical Radiative Transfer model with biochemical processes

    Science.gov (United States)

    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.

  18. A Geometrical Model for Tortuosity of Tortuous Streamlines in Porous Media with Cylindrical Particles

    International Nuclear Information System (INIS)

    We present a three-dimensional geometry model for tortuosity of streamlines in porous media with randomly placed cylindrical particles. The proposed model is expressed as functions of porosity and geometrical parameters with no empirical constant. This might be helpful for understanding the physical mechanism for tortuosity of streamlines in three-dimensional porous media. The model predictions are found to be in good agreement with the experimental data available

  19. Identification of geometrical models of interface evolution for dendritic crystal growth

    OpenAIRE

    Y. Zhao; Coca, D.; Billings, S.A.; Ristic, R.I; DE MATOS, L.L.

    2010-01-01

    This paper introduces a method for identifying geometrical models of interface evolution, directly from experimental imaging data. These local growth models relate normal growth velocity to curvature and its derivatives estimated along the growing interface. Such models can reproduce many qualitative features of dendritic crystal growth as well as predict quantitatively its early stages of evolution. Numerical simulations and experimental crystal growth data are used to demonstrate the ...

  20. A geometric model for cold water and liquid-liquid transitions

    OpenAIRE

    Guisoni, Nara; Henriques, Vera Bohomoletz

    2001-01-01

    Water is an associated liquid in which the main intermolecular interaction is the hydrogen bond (HB) which is limited to four per atom, independently of the number of neighbours. We have considered a hydrogen bond net superposed on Bernal's geometric model for liquids, which allows for different local environments for the liquid particles. In this study, a mean-field treatment of the two-dimensinal version of the model is discussed. Under pressure the model exhibits three phases of different ...

  1. A geometrical model for the Monte Carlo simulation of the TrueBeam linac

    CERN Document Server

    Rodriguez, Miguel; Fogliata, Antonella; Cozzi, Luca; Sauerwein, Wolfgang; Brualla, Lorenzo

    2015-01-01

    Monte Carlo (MC) simulation of linacs depends on the accurate geometrical description of the head. The geometry of the Varian TrueBeam linac is not available to researchers. Instead, the company distributes phase-space files (PSFs) of the flattening-filter-free (FFF) beams tallied upstream the jaws. Yet, MC simulations based on third party tallied PSFs are subject to limitations. We present an experimentally-based geometry developed for the simulation of the FFF beams of the TrueBeam linac. The upper part of the TrueBeam linac was modeled modifying the Clinac 2100 geometry. The most important modification is the replacement of the standard flattening filters by {\\it ad hoc} thin filters which were modeled by comparing dose measurements and simulations. The experimental dose profiles for the 6~MV and 10~MV FFF beams were obtained from the Varian Golden Data Set and from in-house measurements for radiation fields ranging from $3\\times3$ to $40\\times40$ cm$^2$. The same comparisons were done for dose profiles ob...

  2. On bivariate geometric distribution

    OpenAIRE

    Jayakumar, K.; Davis Antony Mundassery

    2013-01-01

    Characterizations of bivariate geometric distribution using univariate and bivariate geometric compounding are obtained. Autoregressive models with marginals as bivariate geometric distribution are developed. Various bivariate geometric distributions analogous to important bivariate exponential distributions like, Marshall-Olkin’s bivariate exponential, Downton’s bivariate exponential and Hawkes’ bivariate exponential are presented.

  3. Geometric Process-Based Maintenance and Optimization Strategy for the Energy Storage Batteries

    Directory of Open Access Journals (Sweden)

    Yan Li

    2016-01-01

    Full Text Available Renewable energy is critical for improving energy structure and reducing environment pollution. But its strong fluctuation and randomness have a serious effect on the stability of the microgrid without the coordination of the energy storage batteries. The main factors that influence the development of the energy storage system are the lack of valid operation and maintenance management as well as the cost control. By analyzing the typical characteristics of the energy storage batteries in their life cycle, the geometric process-based model including the deteriorating system and the improving system is firstly built for describing the operation process, the preventive maintenance process, and the corrective maintenance process. In addition, this paper proposes an optimized management strategy, which aims to minimize the long-run average cost of the energy storage batteries by defining the time interval of the detection and preventive maintenance process as well as the optimal corrective maintenance times, subjected to the state of health and the reliability conditions. The simulation is taken under the built model by applying the proposed energy storage batteries’ optimized management strategy, which verifies the effectiveness and applicability of the management strategy, denoting its obvious practicality on the current application.

  4. Geometric optimization of a neutron detector based on a lithium glass–polymer composite

    International Nuclear Information System (INIS)

    We report on the simulation and optimization of a neutron detector based on a glass–polymer composite that achieves high gamma rejection. Lithium glass is embedded in polyvinyltoluene in three geometric forms: disks, rods, and spheres. Optimal shape, geometric configuration, and size of the lithium glass fragments are determined using Geant4 simulations. All geometrical configurations maintain an approximate 7% glass to polymer mass ratio. Results indicate a 125-mm diameter as the optimal detector size for initial prototype design achieving a 10% efficiency for the thermalization of incident fission neutrons from 252Cf. The geometrical features of a composite detector are shown to have little effect on the intrinsic neutron efficiency, but a significant effect on the gamma rejection is observed. The sphere geometry showed the best overall performance with an intrinsic neutron efficiency of approximately 6% with a gamma rejection better than 10−7 for 280-μm diameter spheres. These promising results provide a motivation for prototype composite detector development based on the simulated designs. - Highlights: • Composite polymer–lithium glass scintillation detector is simulated. • Polymer is considered to be non-scintillating in the simulation. • Three forms of lithium glass are considered: disks, rods, and spheres. • Glass shape has a small effect on neutron efficiency. • Glass shape has a significant effect on gamma rejection

  5. Geometric optimization of a neutron detector based on a lithium glass–polymer composite

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, M., E-mail: mike.f.mayer@gmail.com [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802 (United States); Nattress, J. [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802 (United States); Trivelpiece, C. [Materials Research Institute, The Pennsylvania State University, University Park, PA 16802 (United States); Jovanovic, I. [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802 (United States)

    2015-06-01

    We report on the simulation and optimization of a neutron detector based on a glass–polymer composite that achieves high gamma rejection. Lithium glass is embedded in polyvinyltoluene in three geometric forms: disks, rods, and spheres. Optimal shape, geometric configuration, and size of the lithium glass fragments are determined using Geant4 simulations. All geometrical configurations maintain an approximate 7% glass to polymer mass ratio. Results indicate a 125-mm diameter as the optimal detector size for initial prototype design achieving a 10% efficiency for the thermalization of incident fission neutrons from {sup 252}Cf. The geometrical features of a composite detector are shown to have little effect on the intrinsic neutron efficiency, but a significant effect on the gamma rejection is observed. The sphere geometry showed the best overall performance with an intrinsic neutron efficiency of approximately 6% with a gamma rejection better than 10{sup −7} for 280-μm diameter spheres. These promising results provide a motivation for prototype composite detector development based on the simulated designs. - Highlights: • Composite polymer–lithium glass scintillation detector is simulated. • Polymer is considered to be non-scintillating in the simulation. • Three forms of lithium glass are considered: disks, rods, and spheres. • Glass shape has a small effect on neutron efficiency. • Glass shape has a significant effect on gamma rejection.

  6. A Geometric Computational Model for Calculation of Longwall Face Effect on Gate Roadways

    Science.gov (United States)

    Mohammadi, Hamid; Ebrahimi Farsangi, Mohammad Ali; Jalalifar, Hossein; Ahmadi, Ali Reza

    2016-01-01

    In this paper a geometric computational model (GCM) has been developed for calculating the effect of longwall face on the extension of excavation-damaged zone (EDZ) above the gate roadways (main and tail gates), considering the advance longwall mining method. In this model, the stability of gate roadways are investigated based on loading effects due to EDZ and caving zone (CZ) above the longwall face, which can extend the EDZ size. The structure of GCM depends on four important factors: (1) geomechanical properties of hanging wall, (2) dip and thickness of coal seam, (3) CZ characteristics, and (4) pillar width. The investigations demonstrated that the extension of EDZ is a function of pillar width. Considering the effect of pillar width, new mathematical relationships were presented to calculate the face influence coefficient and characteristics of extended EDZ. Furthermore, taking GCM into account, a computational algorithm for stability analysis of gate roadways was suggested. Validation was carried out through instrumentation and monitoring results of a longwall face at Parvade-2 coal mine in Tabas, Iran, demonstrating good agreement between the new model and measured results. Finally, a sensitivity analysis was carried out on the effect of pillar width, bearing capacity of support system and coal seam dip.

  7. Geometrical Modeling of Concrete Microstructure for the Assessment of ITZ Percolation

    Directory of Open Access Journals (Sweden)

    Daniel Rypl

    2012-01-01

    Full Text Available Percolation is considered to be a critical factor affecting the transport properties of multiphase materials. In the case of concrete, the transport properties are strongly dependent on the interfacial transition zone (ITZ, which is a thin layer of cement paste next to aggregate particles. It is not computationally simple to assess ITZ percolation in concrete, as the geometry and topology of this phase is complex. While there are many advanced models that analyze the behavior of concrete, they are mostly based on the use of spherical or ellipsoidal shapes for the geometry of the aggregate inclusions. These simplified shapes may become unsatisfactory in many simulations, including the assessment of ITZ percolation. This paper deals with geometrical modeling of the concrete microstructure using realistic shapes of aggregate particles, the geometry of which is represented in terms of spherical harmonic expansion. The percolation is assessed using the hard core – soft shell model, in which each randomly-placed aggregate particle is surrounded by a shell of constant thickness representing ITZ.

  8. Development of a geometric uncertainty model describing the accuracy of position-sensitive, coincidence neutron detection

    International Nuclear Information System (INIS)

    A diameter of uncertainty (Du) was derived from a geometric uncertainty model describing the error that would be introduced into position-sensitive, coincidence neutron detection measurements by charged-particle transport phenomena and experimental setup. The transport of α and Li ions, produced by the 10B(n,α) 7Li reaction, through free-standing boro-phosphosilicate glass (BPSG) films was modeled using the Monte Carlo code SRIM, and the results of these simulations were used as input to determine Du for position-sensitive, coincidence techniques. The results of these calculations showed that Du is dependent on encoder separation, the angle of charged particle emission, and film thickness. For certain emission scenarios, the magnitude of Du is larger than the physical size of the neutron converting media that were being modeled. Spheres of uncertainty were developed that describe the difference in flight path times among the bounding-case emission scenarios that were considered in this work. It was shown the overlapping spheres represent emission angles and particle flight path lengths that would be difficult to resolve in terms of particle time-of-flight measurements. However, based on the timing resolution of current nuclear instrumentation, emission events that yield large Du can be discriminated by logical arguments during spectral deconvolution.

  9. Analysis of Oil Film Boundary Conditions of Tilting Pad Bearing Based on a Geometrical Model%基于几何条件的可倾瓦轴承油膜边界条件判定方法

    Institute of Scientific and Technical Information of China (English)

    季超; 荆建平; 陈昌敏

    2015-01-01

    The geometric model describing the boundary conditions of tilting-pad bearings was studied. The coupling effect of the shaft axis, pad center and bearing center locations was analyzed to solve the Reynolds equation and analyze the film pressure distribution by means of finite difference method. Theoretical derivation indicates that the position of each pad is determined by preset parameters and the location of shaft center only. Numerical results show that the bearing capacity increases with the increase of the eccentricity ratio. A case study demonstrates that once the shaft center location is determined, the angle of displacement and the eccentricity ratio can be determined correspondingly, thus the dynamic equation of each pad can be solved. The feasibility law of the boundary conditions has been established, which provides a theoretical basis for the modeling of tilting pad bearings.%针对可倾瓦轴承的雷诺方程,基于瓦块几何模型获得各个瓦块的边界条件,利用轴心、各瓦块中心与轴承之间的耦合关系,采用有限差分法计算分析油膜压力的分布。理论推导表明,瓦块的位置仅由瓦块预置参数、轴心的位置决定;数值结果表明,轴承的承载力随偏心率增大呈增大趋势。结合具体算例看出,当轴颈位置确定时,可确定各瓦块实际偏位角和偏心率,进而可对各瓦块方程分别进行求解。建立一种可行的边界条件确定法则,为可倾瓦轴承的建模提供了理论依据。

  10. Geometric modeling for citation networks with linearly growing scientific paper increment

    CERN Document Server

    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. ...

  11. A geometric graph model for citation networks of exponentially growing scientific papers

    Science.gov (United States)

    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.

  12. 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.

  13. Radmap: ''as-built'' cad models incorporating geometrical, radiological and material information

    International Nuclear Information System (INIS)

    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)

  14. A geometric graph model of the coevolution between citations and coauthorships in scientific papers

    CERN Document Server

    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 ...

  15. Bat Species Comparisons Based on External Morphology: A Test of Traditional versus Geometric Morphometric Approaches.

    Directory of Open Access Journals (Sweden)

    Daniela A Schmieder

    Full Text Available External morphology is commonly used to identify bats as well as to investigate flight and foraging behavior, typically relying on simple length and area measures or ratios. However, geometric morphometrics is increasingly used in the biological sciences to analyse variation in shape and discriminate among species and populations. Here we compare the ability of traditional versus geometric morphometric methods in discriminating between closely related bat species--in this case European horseshoe bats (Rhinolophidae, Chiroptera--based on morphology of the wing, body and tail. In addition to comparing morphometric methods, we used geometric morphometrics to detect interspecies differences as shape changes. Geometric morphometrics yielded improved species discrimination relative to traditional methods. The predicted shape for the variation along the between group principal components revealed that the largest differences between species lay in the extent to which the wing reaches in the direction of the head. This strong trend in interspecific shape variation is associated with size, which we interpret as an evolutionary allometry pattern.

  16. Geometric mechanics

    CERN Document Server

    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.

  17. Registration-based geometric calibration of industrial X-ray tomography system

    International Nuclear Information System (INIS)

    This paper presents a general and efficient method for geometrical calibration of industrial X-ray tomography systems without the use of any phantom. In the field of nondestructive testing (NDT), an accurate numerical model of the object is usually available. By extending the classical volume-to-image registration framework, the method estimates both the parameters related to the position of the object, and those related to the positions and the orientations of the X-ray source, the detector and the rotation axis. Only using the projections data and the numerical model of the object, the values of the geometrical parameters are estimated with a good accuracy. Numerical experiments show that the method provides good results, even if the initialization of the process is far from the real values. (authors)

  18. A geometrical model for the Monte Carlo simulation of the TrueBeam linac

    OpenAIRE

    Rodríguez Niedenführ, Miquel; Sempau Roma, Josep; Fogliata, Antonella; Cozzi, L.; Sauerwein, W.; Brualla, L

    2015-01-01

    Monte Carlo simulation of linear accelerators (linacs) depends on the accurate geometrical description of the linac head. The geometry of the Varian TrueBeam linac is not available to researchers. Instead, the company distributes phase-space files of the flattening-filter-free (FFF) beams tallied at a plane located just upstream of the jaws. Yet, Monte Carlo simulations based on third-party tallied phase spaces are subject to limitations. In this work, an experimentally based geometry develop...

  19. An independent-atom-model description of ion-molecule collisions including geometric screening corrections

    Science.gov (United States)

    Lüdde, Hans Jürgen; Achenbach, Alexander; Kalkbrenner, Thilo; Jankowiak, Hans-Christian; Kirchner, Tom

    2016-04-01

    A new model to account for geometric screening corrections in an independent-atom-model description of ion-molecule collisions is introduced. The ion-molecule cross sections for net capture and net ionization are represented as weighted sums of atomic cross sections with weight factors that are determined from a geometric model of overlapping cross section areas. Results are presented for proton collisions with targets ranging from diatomic to complex polyatomic molecules. Significant improvement compared to simple additivity rule results and in general good agreement with experimental data are found. The flexibility of the approach opens up the possibility to study more detailed observables such as orientation-dependent and charge-state-correlated cross sections for a large class of complex targets ranging from biomolecules to atomic clusters.

  20. A note on geometric method-based procedures to calculate the Hurst exponent

    Science.gov (United States)

    Trinidad Segovia, J. E.; Fernández-Martínez, M.; Sánchez-Granero, M. A.

    2012-03-01

    Geometric method-based procedures, which we will call GM algorithms hereafter, were introduced in M.A. Sánchez-Granero, J.E. Trinidad Segovia, J. García Pérez, Some comments on Hurst exponent and the long memory processes on capital markets, Phys. A 387 (2008) 5543-5551, to calculate the Hurst exponent of a time series. The authors proved that GM algorithms, based on a geometrical approach, are more accurate than classical algorithms, especially with short length time series. The main contribution of this paper is to provide a mathematical background for the validity of these two algorithms to calculate the Hurst exponent H of random processes with stationary and self-affine increments. In particular, we show that these procedures are valid not only for exploring long memory in classical processes such as (fractional) Brownian motions, but also for estimating the Hurst exponent of (fractional) Lévy stable motions.

  1. Polarization conversion system with liquid-crystal geometric-phase-based cylindrical lens

    Science.gov (United States)

    Honma, Michinori; Nose, Toshiaki

    2016-01-01

    We demonstrate a polarization conversion system by utilizing the polarization-splitting function of a liquid-crystal (LC) geometric-phase-based cylindrical lens. The system was constructed by combining the LC lens with a partially rubbed cell. The operation principle includes the following two steps. (i) The incident light is first decomposed into right- and left-handed circularly polarized light (RCP and LCP, respectively) as an attribute of geometric-phase-based optical elements. (ii) Then, only the RCP light is transformed into LCP light by passing it through the partially rubbed cell; as a result, the incident unpolarized light is converted into LCP light. We experimentally reveal the feasibility of the system by evaluating the effects, on the polarization conversion capability, of the diffraction efficiency, focal length, and partially rubbed cell’s retardation. The polarization conversion efficiency was obtained to be 65% on average for 400-700 nm and a maximum of 79% at 610 nm.

  2. 3D Segmentation Method for Natural Environments based on a Geometric-Featured Voxel Map

    OpenAIRE

    Plaza, Victoria; Ababsa, Fakhr-Eddine; Garcia-Cerezo, Alfonso J.; Gomez-Ruiz, Jose Antonio

    2015-01-01

    This work proposes a new segmentation algorithm for three-dimensional dense point clouds and has been specially designed for natural environments where the ground is unstructured and may include big slopes, non-flat areas and isolated areas. This technique is based on a Geometric-Featured Voxel map (GFV) where the scene is discretized in constant size cubes or voxels which are classified in flat surface, linear or tubular structures and scattered or undefined shapes, usually corre...

  3. Image Retrieval based on Integration between Color and Geometric Moment Features

    International Nuclear Information System (INIS)

    Content based image retrieval is the retrieval of images based on visual features such as colour, texture and shape. .the Current approaches to CBIR differ in terms of which image features are extracted; recent work deals with combination of distances or scores from different and usually independent representations in an attempt to induce high level semantics from the low level descriptors of the images. content-based image retrieval has many application areas such as, education, commerce, military, searching, commerce, and biomedicine and Web image classification. This paper proposes a new image retrieval system, which uses color and geometric moment feature to form the feature vectors. Bhattacharyya distance and histogram intersection are used to perform feature matching. This framework integrates the color histogram which represents the global feature and geometric moment as local descriptor to enhance the retrieval results. The proposed technique is proper for precisely retrieving images even in deformation cases such as geometric deformations and noise. It is tested on a standard the results shows that a combination of our approach as a local image descriptor with other global descriptors outperforms other approaches.

  4. Partial SUSY Breaking for Asymmetric Gepner Models and Non-geometric Flux Vacua

    CERN Document Server

    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.

  5. 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.  

  6. Parametric geometric model and shape optimization of an underwater glider with blended-wing-body

    Directory of Open Access Journals (Sweden)

    Sun Chunya

    2015-11-01

    Full Text Available Underwater glider, as a new kind of autonomous underwater vehicles, has many merits such as long-range, extended-duration and low costs. The shape of underwater glider is an important factor in determining the hydrodynamic efficiency. In this paper, a high lift to drag ratio configuration, the Blended-Wing-Body (BWB, is used to design a small civilian under water glider. In the parametric geometric model of the BWB underwater glider, the planform is defined with Bezier curve and linear line, and the section is defined with symmetrical airfoil NACA 0012. Computational investigations are carried out to study the hydrodynamic performance of the glider using the commercial Computational Fluid Dynamics (CFD code Fluent. The Kriging-based genetic algorithm, called Efficient Global Optimization (EGO, is applied to hydrodynamic design optimization. The result demonstrates that the BWB underwater glider has excellent hydrodynamic performance, and the lift to drag ratio of initial design is increased by 7% in the EGO process.

  7. GEOMETRIC COMPLEXITY ANALYSIS IN AN INTEGRATIVE TECHNOLOGY EVALUATION MODEL (ITEM FOR SELECTIVE LASER MELTING (SLM#

    Directory of Open Access Journals (Sweden)

    S. Merkt

    2012-01-01

    Full Text Available

    ENGLISH ABSTRACT: Selective laser melting (SLM is becoming an economically viable choice for manufacturing complex serial parts. This paper focuses on a geometric complexity analysis as part of the integrative technology evaluation model (ITEM presented here. In contrast to conventional evaluation methodologies, the ITEM considers interactions between product and process innovations generated by SLM. The evaluation of manufacturing processes that compete with SLM is the main goal of ITEM. The paper includes a complexity analysis of a test part from Festo AG. The paper closes with a discussion of how the expanded design freedom of SLM can be used to improve company operations, and how the complexity analysis presented here can be seen as a starting point for feature-based complexity analysis..

    AFRIKAANSE OPSOMMING: Selektiewe lasersmelting word geleidelik ’n gangbare ekonomiese keuse vir die vervaar-diging van opeenvolgende komplekse onderdele. Die navorsing is toegespits op die ontleding van meetkundige kompleksiteit as ’n gedeelte van ’n integrerende tegnologiese evalueringsmodel. Gemeet teen konvensionele evalueringsmodelle behandel die genoemde metode interaksies tussen produkte- en prosesinnovasies wat gegenereer word. Die navorsing behandel ’n kompleksiteitsontleding van ’n toetsonderdeel van die firma FESTO AG. Die resultaat toon hoe kompleksiteits-analise gebruik kan word as die vertrekpunt vir eienskapsgebaseerde analise.

  8. Establishment and Optimization of Rigorous Geometric Model of Push-broom Camera Using TDI CCD Arranged in an Alternating Pattern

    Directory of Open Access Journals (Sweden)

    MENG Weican

    2015-12-01

    Full Text Available Push-broom cameras using TDI CCD arranged in an alternating pattern are widely carried by typical high-resolution optical satellites in order to obtain high space resolution and enough strip width. For this kind of cameras, several TDI CCD are arranged in an alternating pattern in two lines on the focal plane and push-broom imaging mode is always adopted. Imaging principle and characteristic of this kind of camera is introduced. Exterior parameters of TDI CCD are modeled together based on their same values in any instant of time and an integrated geometric model is finally established. Error compensation methods are designed to remove exterior error and interior error based on this integrated geometric model. A series of tests are designed to verify models and methods proposed in this paper using original image of TH-1 Satellite HR Camera whose detectors are divided into 8 modules arranged in an alternating pattern. As the results, the imaging geometry of this kind of camera can be rigorously described by this integral geometrical model. The positioning accuracy can be obviously improved by our exterior error compensation method, however, different residual error would be remained for different TDI CCD. The positioning accuracy will not be obviously improved while systematic errors of different TDI CCD can be effectively removed by the interior error compensation method. 2 m positioning accuracy in X, Y and Z directions can be achieved and different systematic errors can be removed when both exterior and interior error were compensated. The same accuracy can be achieved in the other scenes when the calculated inner distortion parameters are adopted.

  9. Non-crimp 3D woven composites unit cell: from geometric modelling to damage simulation

    OpenAIRE

    Bedogni, Enrico

    2013-01-01

    In the last twenty years, the research on composite materials has increased and many progresses have been made. However, there are still unresolved issues concerning the geometric modelling of a material at the meso-level (i.e. on a unit cell) and its damage simulation. In particular, the complexity of the internal geometry of some composite materials, such as 3D textiles, yields to new challenges for the research community. A correct definition of the internal structure in all the important ...

  10. 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.

  11. GEOMETRIC COMPLEXITY ANALYSIS IN AN INTEGRATIVE TECHNOLOGY EVALUATION MODEL (ITEM) FOR SELECTIVE LASER MELTING (SLM)#

    OpenAIRE

    S. Merkt; Hinke, C.; H. Schleifenbaum; H. Voswinckel

    2012-01-01

    ENGLISH ABSTRACT: Selective laser melting (SLM) is becoming an economically viable choice for manufacturing complex serial parts. This paper focuses on a geometric complexity analysis as part of the integrative technology evaluation model (ITEM) presented here. In contrast to conventional evaluation methodologies, the ITEM considers interactions between product and process innovations generated by SLM. The evaluation of manufacturing processes that compete with SLM is the main goal o...

  12. Morphological Discrimination of Greek Honey Bee Populations Based on Geometric Morphometrics Analysis of Wing Shape

    Directory of Open Access Journals (Sweden)

    Charistos Leonidas

    2014-06-01

    Full Text Available Honey bees collected from 32 different localities in Greece were studied based on the geometric morphometrics approach using the coordinates of 19 landmarks located at wing vein intersections. Procrustes analysis, principal component analysis, and Canonical variate analysis (CVA detected population variability among the studied samples. According to the Principal component analysis (PCA of pooled data from each locality, the most differentiated populations were the populations from the Aegean island localities Astypalaia, Chios, and Kythira. However, the populations with the most distant according to the canonical variate analysis performed on all measurements were the populations from Heraklion and Chania (both from Crete island. These results can be used as a starting point for the use of geometric morphometrics in the discrimination of honey bee populations in Greece and the establishment of conservation areas for local honey bee populations.

  13. Geometric Phase Based Quantum Computation Applied to an NP-Complete Problem

    CERN Document Server

    Mitchell, D R

    2005-01-01

    We present a new approach to quantum computation involving the geometric phase. In this approach, an entire computation is performed by adiabatically evolving a suitably chosen quantum system in a closed circuit in parameter space. The problem solved is the determination of the solubility of a 3-SAT Boolean Satisfiability problem. The problem of non-adiabatic transitions to higher levels is addressed in several ways. The avoided level crossings are well defined and the interpolation can be slowed in this region, the Hamiltonian can be scaled with problem dimension resulting in a constant gap size and location, and the prescription here is sufficiently general as to allow for other suitably chosen Hamiltonians. Finally, we show that with $n$ applications of this approach, the geometric phase based quantum computation method may be used to find the solution to the 3-SAT problem in $n$ variables, a member of the NP-complete complexity class.

  14. Turbulence Dynamics based on Lagrange Mechanics and Geometrical Field Theory of Deformation

    CERN Document Server

    Jianhua, Xiao

    2009-01-01

    The turbulence field is stacked on the laminar flow. In this research, the laminar flow is described as a macro deformation which forms an instant curvature space. On such a curvature space, the turbulence is viewed as a micro deformation. So, the fluid flow is described by the geometrical field theory of finite deformation. Based on the Lagrange mechanics and the deformation energy concept, using the Least Action Principle, the Euler-Lagrange motion equations are obtained. According to A E Green formulation, the stress concept is introduced by deformation tensor. The fluid motion is described by the multiplication of a macro deformation tensor and a micro deformation tensor. By this way, the geometrical field of fluid motion is well constructed. Then, the spatial derivative of deformation energy is expressed by the gradient of deformation tensors. By this way, the deformation energy related items in the Euler-Lagrange motion equations are expressed by the stress tensor and deformation tensor. The obtained Eu...

  15. Amorphous forming ranges of Al-Fe-Nd-Zr system predicted by Miedema and geometrical models

    Institute of Scientific and Technical Information of China (English)

    张雷; 陈红梅; 欧阳义芳; 杜勇

    2014-01-01

    A method based on the semi-empirical Miedema model and a geometrical model was used to study the glass forming abili-ties (GFA) and the amorphous forming ranges of Al-Fe-Nd-Zr system and its constituent ternary systems. The amorphous forming composition ranges were analyzed based on different criteria such asΔGam-ss and PHSS (PHSS=ΔHchem (ΔSC/R)(ΔSσ/R)) for Al-Fe-Nd system. The predicted amorphous forming range was in good agreement with the experimental results. The results showed that the criterion ofΔGam-ss was more accurate, and agreed well with the experiment results. The Gibbs free energy differenceΔGam-ss and pa-rameter PHSS were then used to predict the amorphous forming composition range for the rest of the constitutive ternary systems of Al-Fe-Nd-Zr. In addition, the amorphous forming composition ranges of the (Al-Fe-Zr)100-xNdx (x=50, 60, 70) systems were predicted byΔGam-ss and the modified parameter PHSS. The Gibbs free energy of Al10(Fe1-xZrx)30Nd60 were also calculated. The GFA parameter PHSS indicated that the composition with the highest GFA was Al33.5Fe13.5Zr3Nd50 for the (Al-Fe-Zr)50Nd50 system, Al28.8Fe10Zr1.2Nd60 for the (Al-Fe-Zr)40Nd60 system and Al22.8Fe6.9Zr0.3Nd70 for the (Al-Fe-Zr)30Nd70 system, and the results suggested that those alloys with high content of Al had higher GFA. The appropriate content of neodymium and zirconium resulted in the lower value of PHSS and increased the GFA obviously.

  16. Innovative three-dimensional neutronics analyses directly coupled with cad models of geometrically complex fusion systems

    International Nuclear Information System (INIS)

    Fusion systems are, in general, geometrically complex requiring detailed three-dimensional (3-D) nuclear analysis. This analysis is required to address tritium self-sufficiency, nuclear heating, radiation damage, shielding, and radiation streaming issues. To facilitate such calculations, we developed an innovative computational tool that is based on the continuous energy Monte Carlo code MCNP and permits the direct use of CAD-based solid models in the ray-tracing. This allows performing the neutronics calculations in a model that preserves the geometrical details without any simplification, eliminates possible human error in modeling the geometry for MCNP, and allows faster design iterations. In addition to improving the work flow for simulating complex 3- D geometries, it allows a richer representation of the geometry compared to the standard 2nd order polynomial representation. This newly developed tool has been successfully tested for a detailed 40 degree sector benchmark of the International Thermonuclear Experimental Reactor (ITER). The calculations included determining the poloidal variation of the neutron wall loading, flux and nuclear heating in the divertor components, nuclear heating in toroidal field coils, and radiation streaming in the mid-plane port. The tool has been applied to perform 3-D nuclear analysis for several fusion designs including the ARIES Compact Stellarator (ARIES-CS), the High Average Power Laser (HAPL) inertial fusion power plant, and ITER first wall/shield (FWS) modules. The ARIES-CS stellarator has a first wall shape and a plasma profile that varies toroidally within each field period compared to the uniform toroidal shape in tokamaks. Such variation cannot be modeled analytically in the standard MCNP code. The impact of the complex helical geometry and the non-uniform blanket and divertor on the overall tritium breeding ratio and total nuclear heating was determined. In addition, we calculated the neutron wall loading variation in

  17. Parallel Algorithm of Geometrical Hashing Based on NumPy Package and Processes Pool

    Directory of Open Access Journals (Sweden)

    Klyachin Vladimir Aleksandrovich

    2015-10-01

    Full Text Available The article considers the problem of multi-dimensional geometric hashing. The paper describes a mathematical model of geometric hashing and considers an example of its use in localization problems for the point. A method of constructing the corresponding hash matrix by parallel algorithm is considered. In this paper an algorithm of parallel geometric hashing using a development pattern «pool processes» is proposed. The implementation of the algorithm is executed using the Python programming language and NumPy package for manipulating multidimensional data. To implement the process pool it is proposed to use a class Process Pool Executor imported from module concurrent.futures, which is included in the distribution of the interpreter Python since version 3.2. All the solutions are presented in the paper by corresponding UML class diagrams. Designed GeomNash package includes classes Data, Result, GeomHash, Job. The results of the developed program presents the corresponding graphs. Also, the article presents the theoretical justification for the application process pool for the implementation of parallel algorithms. It is obtained condition t2 > (p/(p-1*t1 of the appropriateness of process pool. Here t1 - the time of transmission unit of data between processes, and t2 - the time of processing unit data by one processor.

  18. Geometric-Process-Based Battery Management Optimizing Policy for the Electric Bus

    OpenAIRE

    Yan Li; Jin-kuan Wang; Peng Han; Ying-hua Han

    2015-01-01

    With the rapid development of the electric vehicle industry and promotive policies worldwide, the electric bus (E-bus) has been adopted in many major cities around the world. One of the most important factors that restrain the widespread application of the E-bus is the high operating cost due to the deficient battery management. This paper proposes a geometric-process-based (GP-based) battery management optimizing policy which aims to minimize the average cost of the operation on the premise ...

  19. New software library of geometrical primitives for modelling of solids used in Monte Carlo detector simulations

    CERN Document Server

    CERN. Geneva

    2012-01-01

    We present our effort for the creation of a new software library of geometrical primitives, which are used for solid modelling in Monte Carlo detector simulations. We plan to replace and unify current geometrical primitive classes in the CERN software projects Geant4 and ROOT with this library. Each solid is represented by a C++ class with methods suited for measuring distances of particles from the surface of a solid and for determination as to whether the particles are located inside, outside or on the surface of the solid. We use numerical tolerance for determining whether the particles are located on the surface. The class methods also contain basic support for visualization. We use dedicated test suites for validation of the shape codes. These include also special performance and numerical value comparison tests for help with analysis of possible candidates of class methods as well as to verify that our new implementation proposals were designed and implemented properly. Currently, bridge classes are u...

  20. A United Image Force for Deformable Models and Direct Transforming Geometric Active Contorus to Snakes by Level Sets

    CERN Document Server

    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.

  1. Comparative study of the geometric quantum discord in the transverse Ising model

    International Nuclear Information System (INIS)

    We investigate geometric quantum discords (GQDs) in the two- and three-spin transverse Ising model at both zero and finite temperature. We showed that GQDs measured by the trace distance and the Hellinger distance can be enhanced greatly by the applied transverse magnetic field. For the three-spin isotropic Ising model, the ferromagnetic interaction is more advantageous than that of the antiferromagnetic interaction on creating GQDs. Moreover, the two GQDs can be further increased by the nonuniform Ising interaction between neighbors. In particular, the adjustable antiferromagnetic Ising interaction between two spins is advantageous for enhancing GQDs between them, while the opposite case happens for the other pairs of spins

  2. Comparative study of the geometric quantum discord in the transverse Ising model

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Jia-Min, E-mail: jmgong@yeah.net [School of Electronic Engineering, Xi' an University of Posts and Telecommunications, Xi' an 710121 (China); Wang, Quan [School of Science, Xi' an University of Posts and Telecommunications, Xi' an 710121 (China); Zhang, Ya-Ting [School of Electronic Engineering, Xi' an University of Posts and Telecommunications, Xi' an 710121 (China)

    2015-10-15

    We investigate geometric quantum discords (GQDs) in the two- and three-spin transverse Ising model at both zero and finite temperature. We showed that GQDs measured by the trace distance and the Hellinger distance can be enhanced greatly by the applied transverse magnetic field. For the three-spin isotropic Ising model, the ferromagnetic interaction is more advantageous than that of the antiferromagnetic interaction on creating GQDs. Moreover, the two GQDs can be further increased by the nonuniform Ising interaction between neighbors. In particular, the adjustable antiferromagnetic Ising interaction between two spins is advantageous for enhancing GQDs between them, while the opposite case happens for the other pairs of spins.

  3. Geometrical model of the grain structure refinement resulting from recrystallization of hot-rolled steel

    International Nuclear Information System (INIS)

    The regularities of austenite grain structure transformation due to primary recrystallization of hot worked steels of various chemical composition (carbon, low alloy and high alloy steels) are studied. A geometrical model of refinement of recrystallized austenite grain is developed to predict grain structure parameters in rolled products at any reduction ratio. The model is for use in quality control automatic systems to realize needed structure, texture, mechanical and processing properties in a hot rolled steel with regard to its chemical composition and structure formation features

  4. Study on geometric models of non-numerically controlled machining revolving cutter with constant pitch

    Institute of Scientific and Technical Information of China (English)

    韩成顺; 尚元江; 王景贺; 唐余勇; 董申

    2004-01-01

    This paper presents a new approach of designing the revolving cutter with constant pitch, and pro-vides geometric models. The corresponding models in the non-numerically controlled manufacturing, such asdesigning the helical groove, grinding wheel, relative feeding motion, and calculating the helical angle of thecutting edge, are introduced. The examples are given to testify that the design approach is simple and readilyrealized in machining the revolving cutter with constant pitch. The effective design and manufacture method pro-vides general references for non-NC machining revolving cutter with constant pitch and reducing the equipmentsinput.

  5. The importance of tumor volume in the prognosis of patients with glioblastoma. Comparison of computerized volumetry and geometric models

    International Nuclear Information System (INIS)

    Background and purpose: the importance of tumor volume as a prognostic factor in high-grade gliomas is highly controversial and there are numerous methods estimating this parameter. In this study, a computer-based application was used in order to assess tumor volume from hard copies and a survival analysis was conducted in order to evaluate the prognostic significance of preoperative volumetric data in patients harboring glioblastomas. Patients and methods: 50 patients suffering from glioblastoma were analyzed retrospectively. Tumor volume was determined by the various geometric models as well as by an own specialized software (Volumio). Age, performance status, type of excision, and tumor location were also included in the multivariate analysis. Results: the spheroid and rectangular models overestimated tumor volume, while the ellipsoid model offered the best approximation. Volume failed to attain any statistical significance in prognosis, while age and performance status confirmed their importance in progression-free and overall survival of patients. Conclusion: geometric models provide a rough approximation of tumor volume and should not be used, as accurate determination of size is of paramount importance in order to draw safe conclusions in oncology. Although the significance of volumetry was not disclosed, further studies are definitely required. (orig.)

  6. Retrieval of Airborne Lidar Misalignments Based on the Stepwise Geometric Method

    DEFF Research Database (Denmark)

    Zhang, Xiaohong; Forsberg, René

    2010-01-01

    the relationship between the point clouds on a regular object, e.g. a flat top building, and the ground truth of the objects used for calibration. In order to extract the footprints on the objects, filtering is implemented before the calibration. The tests verify that the proposed method is feasible......In this paper, a new simple method for airborne LIDAR system misalignment calibration is described in detail. The method is especially designed for environmental surveys, such as beach mapping or glacier surveys. The proposed method, termed stepwise geometric misalignment determination is based on...

  7. Tunable orbital angular momentum mode filter based on optical geometric transformation.

    Science.gov (United States)

    Huang, Hao; Ren, Yongxiong; Xie, Guodong; Yan, Yan; Yue, Yang; Ahmed, Nisar; Lavery, Martin P J; Padgett, Miles J; Dolinar, Sam; Tur, Moshe; Willner, Alan E

    2014-03-15

    We present a tunable mode filter for spatially multiplexed laser beams carrying orbital angular momentum (OAM). The filter comprises an optical geometric transformation-based OAM mode sorter and a spatial light modulator (SLM). The programmable SLM can selectively control the passing/blocking of each input OAM beam. We experimentally demonstrate tunable filtering of one or multiple OAM modes from four multiplexed input OAM modes with vortex charge of ℓ=-9, -4, +4, and +9. The measured output power suppression ratio of the propagated modes to the blocked modes exceeds 14.5 dB. PMID:24690870

  8. Designing an Iterative Learning Control Algorithm Based on Process History using limited post process geometrical information

    DEFF Research Database (Denmark)

    Endelt, Benny Ørtoft; Volk, Wolfram

    2013-01-01

    , the reaction speed may be insufficient compared to the production rate in an industrial application. We propose to design an iterative learning control (ILC) algorithm which can control and update the blank-holder force as well as the distribution of the blank-holder force based on limited geometric data from......, there is a number of obstacles which need to be addressed before an industrial implementation is possible, e.g. the proposed control algorithms are often limited by the ability to sample process data with both sufficient accuracy and robustness - this lack of robust sampling technologies is one of the main barriers...

  9. Hybrid geometrical-optical radiative-transfer model for the directional reflectance of discontinuous vegetation canopies

    Science.gov (United States)

    Li, Xiaowen; Strahler, Alan H.; Woodcock, Curtis E.

    1995-01-01

    A new model for the bidirectional reflectance of a vegetation cover combines principles of geometric optics and radiative transfer. It relies on gap probabilities and path length distributions to model the penetration of irradiance from a parallel source and the single and multiple scattering of that irradiance in the direction of an observer. The model applies to vegetation covers of discrete plant crowns that are randomly centered both on the plane and within a layer of variable thickness above it. Crowns assume a spheroidal shape with arbitrary height to width ratio. Geometric optics easily models the irradiance that penetrates the vegetation cover directly, is scattered by the soil, and exits without further scattering by the vegetation. Within a plant crown, the probability of scattering is a negative exponential function of path length. Within-crown scattering provides the source for singly-scattered radiation, which exits with probabilities proportional to further path-length distributions in the direction of exitance (including the hotspot effect). Single scattering provides the source for double scattering, and then higher order pairs of scattering are solved successively by a convolution function. As an early exercise in validation, the model is applied to an open jack pine canopy and ground-level irradiance is predicted with good accuracy.

  10. Midpoint attractors and species richness: Modelling the interaction between environmental drivers and geometric constraints.

    Science.gov (United States)

    Colwell, Robert K; Gotelli, Nicholas J; Ashton, Louise A; Beck, Jan; Brehm, Gunnar; Fayle, Tom M; Fiedler, Konrad; Forister, Matthew L; Kessler, Michael; Kitching, Roger L; Klimes, Petr; Kluge, Jürgen; Longino, John T; Maunsell, Sarah C; McCain, Christy M; Moses, Jimmy; Noben, Sarah; Sam, Katerina; Sam, Legi; Shapiro, Arthur M; Wang, Xiangping; Novotny, Vojtech

    2016-09-01

    We introduce a novel framework for conceptualising, quantifying and unifying discordant patterns of species richness along geographical gradients. While not itself explicitly mechanistic, this approach offers a path towards understanding mechanisms. In this study, we focused on the diverse patterns of species richness on mountainsides. We conjectured that elevational range midpoints of species may be drawn towards a single midpoint attractor - a unimodal gradient of environmental favourability. The midpoint attractor interacts with geometric constraints imposed by sea level and the mountaintop to produce taxon-specific patterns of species richness. We developed a Bayesian simulation model to estimate the location and strength of the midpoint attractor from species occurrence data sampled along mountainsides. We also constructed midpoint predictor models to test whether environmental variables could directly account for the observed patterns of species range midpoints. We challenged these models with 16 elevational data sets, comprising 4500 species of insects, vertebrates and plants. The midpoint predictor models generally failed to predict the pattern of species midpoints. In contrast, the midpoint attractor model closely reproduced empirical spatial patterns of species richness and range midpoints. Gradients of environmental favourability, subject to geometric constraints, may parsimoniously account for elevational and other patterns of species richness. PMID:27358193

  11. Modeling the Influence of Antifreeze Proteins on Three-Dimensional Ice Crystal Melt Shapes using a Geometric Approach

    CERN Document Server

    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.

  12. Research on geometric model of grinding large and medium scales optical aspheric surfaces

    Science.gov (United States)

    Kang, Nianhui; Li, Shengyi; Zheng, Ziwen

    2006-01-01

    Aspheric optics have been used in optical systems widely because of their excellent optical properties. At present, the manufacture of small scale aspheric surfaces has been industrialized. However the manufacture of large and medium aspheric surfaces still follows the procedure of grinding, lapping and polishing. Generally speaking, increasing the working efficiency is the key of machining large and medium scale aspheric surfaces. As we know, lapping and polishing have relatively low efficiencies. Therefore prior to lapping and polishing, NC grinding is often used to shape large and medium scale optical aspheric surfaces, so as to reduce the subsequent process time. Current approaches to grinding aspheric surfaces differ from each other because the wheels and methods used are different, which is inconvenient for programming. To facilitate programming, a unified mathematical formulation is proposed for calculation of the wheel center trajectory when grinding axisymmetric aspheric surfaces based on the principle of shaping aspheric surfaces. Certain geometric models are derived from the unified formulation for the cases of parallel grinding wheel, spherical grinding wheel and cup grinding wheel, according to their features of process. The condition of avoiding overcutting is also derived. The step length of cutting is adaptively selected with accuracy control so as to reduce the program codes. After analyze all the factors affecting the shape accuracy of the curved surface, the major factors are found to be the tool setting error and the radius error of the grinding wheel, then the corresponding influence coefficients of the errors are calculated and the simulation results are given. Finally an example is shown in order to prove the analysis.

  13. Optimising and extending the geometrical modeller of a physics simulation framework

    CERN Document Server

    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...

  14. The Beta-Geometric Model Applied to Fecundability in a Sample of Married Women

    Science.gov (United States)

    Adekanmbi, D. B.; Bamiduro, T. A.

    2006-10-01

    The time required to achieve pregnancy among married couples termed fecundability has been proposed to follow a beta-geometric distribution. The accuracy of the method used in estimating the parameters of the model has an implication on the goodness of fit of the model. In this study, the parameters of the model are estimated using the Method of Moments and Newton-Raphson estimation procedure. The goodness of fit of the model was considered, using estimates from the two methods of estimation, as well as the asymptotic relative efficiency of the estimates. A noticeable improvement in the fit of the model to the data on time to conception was observed, when the parameters are estimated by Newton-Raphson procedure, and thereby estimating reasonable expectations of fecundability for married female population in the country.

  15. How well do lattice simulations reproduce the different aspects of the Geometrical Schwinger Model?

    International Nuclear Information System (INIS)

    Gauge theories with massless fermions possess an intricate non-perturbative structure mainly determined by the topology of gauge field configurations and index theorems for Dirac operators in such background fields. This part of the Standard Model of elementary particle physics is not yet well investigated. A study of the 'Geometric Schwinger Model' (GSM) on the torus showed that this simple solvable 2-dim. model exhibits quite a few characteristic features of the non-perturbative structure. We mention the realization of chiral symmetry breaking by an axial anomaly, and the screening of a confining potential by fermions. It is the aim of our studies to investigate how well the methods of lattice approximation can reproduce these non-perturbative features of the Schwinger Model. The 'geometric' version of the SM with Dirac Kaehler fermions is particularly suited for such an investigation: While there exists a systematic lattice approximation by staggered fermions, there are also explicit expressions for the Green's functions in the continuum for comparison with the lattice results. This includes the finite volume effects of the torus. (orig.)

  16. Measuring the impact of 3D data geometric modeling on spatial analysis: Illustration with Skyview factor

    Science.gov (United States)

    Brasebin, M.; Perret, J.; Mustière, S.; Weber, C.

    2012-10-01

    The increased availability of 3D urban data reflects a growing interest in 3D spatial analysis. As 3D spatial analysis often uses complex 3D data, studies of the potential gains of using more detailed 3D urban databases for specific uses is an important issue. First, more complex data implies an increase in time and memory usage for the analysis (and calls for more research on the efficiency of the algorithms used). Second, detailed 3D urban data are complex to produce, expensive and it is important to be well informed in order to decide whether of not to invest in such data. Currently, many studies have been led about the fitness for use of 2D data but they are very scarce concerning 3D data. This article presents a method to determine the influence of 3D modeling on the results of 3D analysis by isolating the potential sources of errors (such as roof modeling and geometric accuracy). This method is applied on two 3D datasets (LOD1 and LOD2) and a 3D indicator (the sky view factor or SVF). The results show that the significant influence of roof modeling is globally compensated by the difference in geometric modeling but that important local variations are noticed. Nevertheless, for 75% of the SVF processed the difference between the results using these two databases is lower than 2%.

  17. Parametric geometric model and shape optimization of an underwater glider with blended-wing-body

    OpenAIRE

    Sun Chunya; Song Baowei; Wang Peng

    2015-01-01

    Underwater glider, as a new kind of autonomous underwater vehicles, has many merits such as long-range, extended-duration and low costs. The shape of underwater glider is an important factor in determining the hydrodynamic efficiency. In this paper, a high lift to drag ratio configuration, the Blended-Wing-Body (BWB), is used to design a small civilian under water glider. In the parametric geometric model of the BWB underwater glider, the planform is defined with Bezier curve and linear line,...

  18. Geometric-attributes-based segmentation of cortical bone slides using optimized neural networks.

    Science.gov (United States)

    Hage, Ilige S; Hamade, Ramsey F

    2016-05-01

    In cortical bone, solid (lamellar and interstitial) matrix occupies space left over by porous microfeatures such as Haversian canals, lacunae, and canaliculi-containing clusters. In this work, pulse-coupled neural networks (PCNN) were used to automatically distinguish the microfeatures present in histology slides of cortical bone. The networks' parameters were optimized using particle swarm optimization (PSO). When forming the fitness functions for the PSO, we considered the microfeatures' geometric attributes-namely, their size (based on measures of elliptical perimeter or area), shape (based on measures of compactness or the ratio of minor axis length to major axis length), and a two-way combination of these two geometric attributes. This hybrid PCNN-PSO method was further enhanced for pulse evaluation by combination with yet another method, adaptive threshold (AT), where the PCNN algorithm is repeated until the best threshold is found corresponding to the maximum variance between two segmented regions. Together, this framework of using PCNN-PSO-AT constitutes, we believe, a novel framework in biomedical imaging. Using this framework and extracting microfeatures from only one training image, we successfully extracted microfeatures from other test images. The high fidelity of all resultant segments was established using quantitative metrics such as precision, specificity, and Dice indices. PMID:26104115

  19. An atomistic geometrical model of the B-DNA configuration for DNA-radiation interaction simulations

    Science.gov (United States)

    Bernal, M. A.; Sikansi, D.; Cavalcante, F.; Incerti, S.; Champion, C.; Ivanchenko, V.; Francis, Z.

    2013-12-01

    In this paper, an atomistic geometrical model for the B-DNA configuration is explained. This model accounts for five organization levels of the DNA, up to the 30 nm chromatin fiber. However, fragments of this fiber can be used to construct the whole genome. The algorithm developed in this work is capable to determine which is the closest atom with respect to an arbitrary point in space. It can be used in any application in which a DNA geometrical model is needed, for instance, in investigations related to the effects of ionizing radiations on the human genetic material. Successful consistency checks were carried out to test the proposed model. Catalogue identifier: AEPZ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEPZ_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 1245 No. of bytes in distributed program, including test data, etc.: 6574 Distribution format: tar.gz Programming language: FORTRAN. Computer: Any. Operating system: Multi-platform. RAM: 2 Gb Classification: 3. Nature of problem: The Monte Carlo method is used to simulate the interaction of ionizing radiation with the human genetic material in order to determine DNA damage yields per unit absorbed dose. To accomplish this task, an algorithm to determine if a given energy deposition lies within a given target is needed. This target can be an atom or any other structure of the genetic material. Solution method: This is a stand-alone subroutine describing an atomic-resolution geometrical model of the B-DNA configuration. It is able to determine the closest atom to an arbitrary point in space. This model accounts for five organization levels of the human genetic material, from the nucleotide pair up to the 30 nm chromatin fiber. This subroutine carries out a series of coordinate transformations

  20. Augmentation of Explicit Spatial Configurations by Knowledge-Based Inference on Geometric Fields

    Directory of Open Access Journals (Sweden)

    Dan Tappan

    2009-04-01

    Full Text Available A spatial configuration of a rudimentary, static, realworld scene with known objects (animals and properties (positions and orientations contains a wealth of syntactic and semantic spatial information that can contribute to a computational understanding far beyond what its quantitative details alone convey. This work presents an approach that (1 quantitatively represents what a configuration explicitly states, (2 integrates this information with implicit, commonsense background knowledge of its objects and properties, (3 infers additional, contextually appropriate, commonsense spatial information from and about their interrelationships, and (4 augments the original representation with this combined information. A semantic network represents explicit, quantitative information in a configuration. An inheritance-based knowledge base of relevant concepts supplies implicit, qualitative background knowledge to support semantic interpretation. Together, these structures provide a simple, nondeductive, constraint-based, geometric logical formalism to infer substantial implicit knowledge for intrinsic and deictic frames of spatial reference.

  1. The unfolded universe of elementary particles. A geometric explanation of the standard model structure

    CERN Document Server

    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.

  2. A discrete model for geometrically nonlinear transverse free constrained vibrations of beams with various end conditions

    Science.gov (United States)

    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

  3. A new representation of orientable 2-manifold polygonal surfaces for geometric modelling

    Institute of Scientific and Technical Information of China (English)

    LIU Yong-jin; TANG Kai; JOENJA Ajay

    2006-01-01

    Many graphics and computer-aided design applications require that the polygonal meshes used in geometric computing have the properties of not only 2-manifold but also are orientable. In this paper, by collecting previous work scattered in the topology and geometry literature, we rigorously present a theoretical basis for orientable polygonal surface representation from a modern point of view. Based on the presented basis, we propose a new combinatorial data structure that can guarantee the property of orientable 2-manifolds and is primal/dual efficient. Comparisons with other widely used data structures are also presented in terms of time and space efficiency.

  4. Sampling-based exploration of folded state of a protein under kinematic and geometric constraints

    KAUST Repository

    Yao, Peggy

    2011-10-04

    Flexibility is critical for a folded protein to bind to other molecules (ligands) and achieve its functions. The conformational selection theory suggests that a folded protein deforms continuously and its ligand selects the most favorable conformations to bind to. Therefore, one of the best options to study protein-ligand binding is to sample conformations broadly distributed over the protein-folded state. This article presents a new sampler, called kino-geometric sampler (KGS). This sampler encodes dominant energy terms implicitly by simple kinematic and geometric constraints. Two key technical contributions of KGS are (1) a robotics-inspired Jacobian-based method to simultaneously deform a large number of interdependent kinematic cycles without any significant break-up of the closure constraints, and (2) a diffusive strategy to generate conformation distributions that diffuse quickly throughout the protein folded state. Experiments on four very different test proteins demonstrate that KGS can efficiently compute distributions containing conformations close to target (e.g., functional) conformations. These targets are not given to KGS, hence are not used to bias the sampling process. In particular, for a lysine-binding protein, KGS was able to sample conformations in both the intermediate and functional states without the ligand, while previous work using molecular dynamics simulation had required the ligand to be taken into account in the potential function. Overall, KGS demonstrates that kino-geometric constraints characterize the folded subset of a protein conformation space and that this subset is small enough to be approximated by a relatively small distribution of conformations. © 2011 Wiley Periodicals, Inc.

  5. VOLUMETRIC ERROR COMPENSATION IN FIVE-AXIS CNC MACHINING CENTER THROUGH KINEMATICS MODELING OF GEOMETRIC ERROR

    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.

  6. Fusion of inertial and visual: a geometrical observer-based approach

    International Nuclear Information System (INIS)

    The problem of combination between inertial sensors and CCD cameras is of paramount importance in various applications in robotics and autonomous navigation. In this paper we develop a totally geometric model for analysis of this problem, independently from a camera model and from the structure of the scene (landmarks etc.). This formulation can be used for data fusion in several inertial navigation problems. The estimation is then decoupled from the structure of the scene. We use it in the particular case of the estimation of the gyroscopes bias and we build a nonlinear observer which is easy to compute, provides an estimation of the biais, filters the image, and is by construction very robust to noise.

  7. Landmark-based geometric morphometric analysis of wing shape among certain species of Aedes mosquitoes in District Dehradun (Uttarakhand), India

    OpenAIRE

    Ritwik Mondal; Pemola Devi, N.; R.K. Jauhari

    2015-01-01

    Background & objectives: Insect wing morphology has been used in many studies to describe variations among species and populations using traditional morphometrics, and more recently geometric morphometrics. A landmark-based geometric morphometric analysis of the wings of three species of Aedes (Diptera: Culicidae), viz. Ae. aegypti, Ae. albopictus and Ae. pseudotaeniatus, at District Dehradun was conducted belling on the fact that it can provide insight into the population structure, ecology ...

  8. Eccentricity error compensation for geometric camera calibration based on circular features

    International Nuclear Information System (INIS)

    Circular features are very common in geometric camera calibration. The projection of a circular feature is generally a deformed ellipse, not a true ellipse, due to the presence of lens distortion. The center of the deformed ellipse, obtained by fitting the boundary points with an ellipse, does not necessarily coincide with the distorted point corresponding to the center of the undistorted projection of the circular feature. An eccentricity error will be introduced if the two points are considered to be coincident. In this study three main factors that affect the amount of the eccentricity error are discussed, including the form and amount of lens distortion, the size of the circular feature and the tilt of the supporting plane. Then, an effective geometric camera calibration method is proposed where the eccentricity error is compensated by establishing the correspondence between the estimated model position and the real position of the fitted center of the deformed ellipse. Both simulation and measurement data verify the existence of the eccentricity error and the effectiveness of the proposed method. (paper)

  9. Quasi-Topological Gauged Sigma Models, The Geometric Langlands Program, And Knots

    CERN Document Server

    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...

  10. Classifying Data Sets Using Support Vector Machines Based on Geometric Distance

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Support vector machines (SVMs) are not as favored for large-scale data mining as for pattern recognition and machine learning because the training complexity of SVMs is highly dependent on the size of data set. This paper presents a geometric distance-based SVM (GDB-SVM). It takes the distance between a point and classified hyperplane as classification rule,and is designed on the basis of theoretical analysis and geometric intuition. Experimental code is derived from LibSVM with Microsoft Visual C ++ 6.0 as system of translating and editing. Four predicted results of five of GDB-SVM are better than those of the method of one against all (OAA). Three predicted results of five of GDB-SVM are better than those of the method of one against one (OAO). Experiments on real data sets show that GDB-SVM is not only superior to the methods of OAA and OAO,but highly scalable for large data sets while generating high classification accuracy.

  11. A comparison of geometric- and regression-based mobile gaze-tracking

    Directory of Open Access Journals (Sweden)

    Björn Browatzki

    2014-04-01

    Full Text Available Video-based gaze-tracking systems are typically restricted in terms of their effective tracking space. This constraint limits the use of eyetrackers in studying mobile human behavior. Here, we compare two possible approaches for estimating the gaze of participants who are free to walk in a large space whilst looking at different regions of a large display. Geometrically, we linearly combined eye-in-head rotations and head-in-world coordinates to derive a gaze vector and its intersection with a planar display, by relying on the use of a head-mounted eyetracker and body-motion tracker. Alternatively, we employed Gaussian process regression to estimate the gaze intersection directly from the input data itself. Our evaluation of both methods indicates that a regression approach can deliver comparable results to a geometric approach. The regression approach is favored, given that it has the potential for further optimization, provides confidence bounds for its gaze estimates and offers greater flexibility in its implementation. Open-source software for the methods reported here is also provided for user implementation.

  12. QRS complex detection based on simple robust 2-D pictorial-geometrical feature.

    Science.gov (United States)

    Hoseini Sabzevari, S A; Moavenian, Majid

    2014-01-01

    In this paper a heuristic method aimed for detecting of QRS complexes without any pre-process was developed. All the methods developed in previous studies were used pre-process, the most novelty of this study was suggesting a simple method which did not need any pre-process. Toward this objective, a new simple 2-D geometrical feature space was extracted from the original electrocardiogram (ECG) signal. In this method, a sliding window was moved sample-by-sample on the pre-processed ECG signal. During each forward slide of the analysis window an artificial image was generated from the excerpted segment allocated in the window. Then, a geometrical feature extraction technique based on curve-length and angle of highest point was applied to each image for establishment of an appropriate feature space. Afterwards the K-Nearest Neighbors (KNN), Artificial Neural Network (ANN) and Adaptive Network Fuzzy Inference Systems (ANFIS) were designed and implemented to the ECG signal. The proposed methods were applied to DAY general hospital high resolution holter data. For detection of QRS complex the average values of sensitivity Se = 99.93% and positive predictivity P+ = 99.92% were obtained. PMID:24144188

  13. Geometric integration methods for general nonlinear dynamic equation based on Magnus and Fer expansions

    Institute of Scientific and Technical Information of China (English)

    ZHANG Suying; DENG Zichen

    2005-01-01

    Based on Magnus or Fer expansion for solving linear differential equation and operator semi-group theory, Lie group integration methods for general nonlinear dynamic equation are studied. Approximate schemes of Magnus type of 4th, 6th and 8th order are constructed which involve only 1, 4 and 10 different commutators, and the time-symmetry properties of the schemes are proved. In the meantime, the integration methods based on Fer expansion are presented. Then by connecting the Fer expansion methods with Magnus expansion methods some techniques are given to simplify the construction of Fer expansion methods. Furthermore time-symmetric integrators of Fer type are constructed. These methods belong to the category of geometric integration methods and can preserve many qualitative properties of the original dynamic system.

  14. Geometric Corroboration of the Earliest Lensed Galaxy at z~10.8 from Robust Free-Form Modelling

    CERN Document Server

    Chan, Brian M Y; Lim, Jeremy; Diego, Jose M; Zitrin, Adi; Coe, Dan; Ford, Holland C

    2016-01-01

    A multiply-lensed galaxy, MACS0647-JD, with a probable photometric redshift of $z\\simeq 10.7^{+0.6}_{-0.4}$ is claimed to constitute one of the very earliest known galaxies, formed well before reionization was completed. However, spectral evidence that MACS0647-JD lies at high redshift has proven infeasible and so here we seek an independent lensing based "geometric redshift" derived from the angles between the three lensed images of MACS0647-JD, using our free-form mass model (WSLAP+) for the lensing cluster MACSJ0647.7+7015 (at $z=0.591$). Our lens model uses the 9 sets of multiple images, including those of MACS0647-JD, identified by the CLASH survey towards this cluster. We convincingly exclude the low redshift regime of $z<3$, for which convoluted critical curves are generated by our method, as the solution bends to accommodate the wide angles of MACS0647-JD for this low redshift. Instead, a best fit to all sets of lensed galaxy positions and redshifts provides a geometric redshift of $z\\simeq 10.8^{+...

  15. Growing Random Geometric Graph Models of Super-linear Scaling Law

    CERN Document Server

    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...

  16. Enhanced Geometric Map:a 2D & 3D Hybrid City Model of Large Scale Urban Environment for Robot Navigation

    Institute of Scientific and Technical Information of China (English)

    LI Haifeng; HU Zunhe; LIU Jingtai

    2016-01-01

    To facilitate scene understanding and robot navigation in large scale urban environment, a two-layer enhanced geometric map (EGMap) is designed using videos from a monocular onboard camera. The 2D layer of EGMap consists of a 2D building boundary map from top-down view and a 2D road map, which can support localization and advanced map-matching when compared with standard polyline-based maps. The 3D layer includes features such as 3D road model, and building facades with coplanar 3D vertical and horizontal line segments, which can provide the 3D metric features to localize the vehicles and flying-robots in 3D space. Starting from the 2D building boundary and road map, EGMap is initially constructed using feature fusion with geometric constraints under a line feature-based simultaneous localization and mapping (SLAM) framework iteratively and progressively. Then, a local bundle adjustment algorithm is proposed to jointly refine the camera localizations and EGMap features. Furthermore, the issues of uncertainty, memory use, time efficiency and obstacle effect in EGMap construction are discussed and analyzed. Physical experiments show that EGMap can be successfully constructed in large scale urban environment and the construction method is demonstrated to be very accurate and robust.

  17. Flood inundation mapping uncertainty introduced by topographic data accuracy, geometric configuration and modeling approach

    Science.gov (United States)

    Papaioannou, G.; Loukas, Athanasios

    2010-05-01

    Floodplain modeling is a recently new and applied method in river engineering discipline and is essential for prediction of flood hazards. The issue of flood inundation of upland environments with topographically complex floodplains is an understudied subject. In most areas of the U.S.A., the use of topographic information derived from Light Detection and Ranging (LIDAR) has improved the quality of river flood inundation predictions. However, such high quality topographical data are not available in most countries and the necessary information is obtained by topographical survey and/or topographical maps. Furthermore, the optimum dimensionality of hydraulic models, cross-section configuration in one-dimensional (1D) models, mesh resolution in two-dimensional models (2D) and modeling approach is not well studied or documented. All these factors introduce significant uncertainty in the evaluation of the floodplain zoning. This study addresses some of these issues by comparing flood inundation maps developed using different topography, geometric description and modeling approach. The methodology involves use of topographic datasets with different horizontal resolutions, vertical accuracies and bathymetry details. Each topographic dataset is used to create a flood inundation map for different cross-section configurations using 1D (HEC-RAS) model, and different mesh resolutions using 2D models for steady state and unsteady state conditions. Comparison of resulting maps indicates the uncertainty introduced in floodplain modeling by the horizontal resolution and vertical accuracy of topographic data and the different modeling approaches.

  18. Noncyclic geometric quantum computation and preservation of entanglement for a two-qubit Ising model

    Science.gov (United States)

    Rangani Jahromi, H.; Amniat-Talab, M.

    2015-10-01

    After presenting an exact analytical solution of time-dependent Schrödinger equation, we study the dynamics of entanglement for a two-qubit Ising model. One of the spin qubits is driven by a static magnetic field applied in the direction of the Ising interaction, while the other is coupled with a rotating magnetic field. We also investigate how the entanglement can be controlled by changing the external parameters. Because of the important role of maximally entangled Bell states in quantum communication, we focus on the generalized Bell states as the initial states of the system. It is found that the entanglement evolution is independent of the initial Bell states. Moreover, we can preserve the initial maximal entanglement by adjusting the angular frequency of the rotating field or controlling the exchange coupling between spin qubits. Besides, our calculation shows that the entanglement dynamics is unaffected by the static magnetic field imposed in the direction of the Ising interaction. This is an interesting result, because, as we shall show below, this driving field can be used to control and manipulate the noncyclic geometric phase without affecting the system entanglement. Besides, the nonadiabatic and noncyclic geometric phase for evolved states of the present system are calculated and described in detail. In order to identify the unusable states for quantum communication, completely deviated from the initial maximally entangled states, we also study the fidelity between the initial Bell state and the evolved state of the system. Interestingly, we find that these unusable states can be detected by geometric quantum computation.

  19. Design of all-optical, hot-electron current-direction-switching device based on geometrical asymmetry

    Science.gov (United States)

    Kumarasinghe, Chathurangi S.; Premaratne, Malin; Gunapala, Sarath D.; Agrawal, Govind P.

    2016-01-01

    We propose a nano-scale current-direction-switching device(CDSD) that operates based on the novel phenomenon of geometrical asymmetry between two hot-electron generating plasmonic nanostructures. The proposed device is easy to fabricate and economical to develop compared to most other existing designs. It also has the ability to function without external wiring in nano or molecular circuitry since it is powered and controlled optically. We consider a such CDSD made of two dissimilar nanorods separated by a thin but finite potential barrier and theoretically derive the frequency-dependent electron/current flow rate. Our analysis takes in to account the quantum dynamics of electrons inside the nanorods under a periodic optical perturbation that are confined by nanorod boundaries, modelled as finite cylindrical potential wells. The influence of design parameters, such as geometric difference between the two nanorods, their volumes and the barrier width on quality parameters such as frequency-sensitivity of the current flow direction, magnitude of the current flow, positive to negative current ratio, and the energy conversion efficiency is discussed by considering a device made of Ag/TiO2/Ag. Theoretical insight and design guidelines presented here are useful for customizing our proposed CDSD for applications such as self-powered logic gates, power supplies, and sensors. PMID:26887286

  20. Design of all-optical, hot-electron current-direction-switching device based on geometrical asymmetry.

    Science.gov (United States)

    Kumarasinghe, Chathurangi S; Premaratne, Malin; Gunapala, Sarath D; Agrawal, Govind P

    2016-01-01

    We propose a nano-scale current-direction-switching device(CDSD) that operates based on the novel phenomenon of geometrical asymmetry between two hot-electron generating plasmonic nanostructures. The proposed device is easy to fabricate and economical to develop compared to most other existing designs. It also has the ability to function without external wiring in nano or molecular circuitry since it is powered and controlled optically. We consider a such CDSD made of two dissimilar nanorods separated by a thin but finite potential barrier and theoretically derive the frequency-dependent electron/current flow rate. Our analysis takes in to account the quantum dynamics of electrons inside the nanorods under a periodic optical perturbation that are confined by nanorod boundaries, modelled as finite cylindrical potential wells. The influence of design parameters, such as geometric difference between the two nanorods, their volumes and the barrier width on quality parameters such as frequency-sensitivity of the current flow direction, magnitude of the current flow, positive to negative current ratio, and the energy conversion efficiency is discussed by considering a device made of Ag/TiO2/Ag. Theoretical insight and design guidelines presented here are useful for customizing our proposed CDSD for applications such as self-powered logic gates, power supplies, and sensors. PMID:26887286

  1. Design of all-optical, hot-electron current-direction-switching device based on geometrical asymmetry

    Science.gov (United States)

    Kumarasinghe, Chathurangi S.; Premaratne, Malin; Gunapala, Sarath D.; Agrawal, Govind P.

    2016-02-01

    We propose a nano-scale current-direction-switching device(CDSD) that operates based on the novel phenomenon of geometrical asymmetry between two hot-electron generating plasmonic nanostructures. The proposed device is easy to fabricate and economical to develop compared to most other existing designs. It also has the ability to function without external wiring in nano or molecular circuitry since it is powered and controlled optically. We consider a such CDSD made of two dissimilar nanorods separated by a thin but finite potential barrier and theoretically derive the frequency-dependent electron/current flow rate. Our analysis takes in to account the quantum dynamics of electrons inside the nanorods under a periodic optical perturbation that are confined by nanorod boundaries, modelled as finite cylindrical potential wells. The influence of design parameters, such as geometric difference between the two nanorods, their volumes and the barrier width on quality parameters such as frequency-sensitivity of the current flow direction, magnitude of the current flow, positive to negative current ratio, and the energy conversion efficiency is discussed by considering a device made of Ag/TiO2/Ag. Theoretical insight and design guidelines presented here are useful for customizing our proposed CDSD for applications such as self-powered logic gates, power supplies, and sensors.

  2. Optimizing the geometrical accuracy of curvilinear meshes

    CERN Document Server

    Toulorge, Thomas; Remacle, Jean-François

    2015-01-01

    This paper presents a method to generate valid high order meshes with optimized geometrical accuracy. The high order meshing procedure starts with a linear mesh, that is subsequently curved without taking care of the validity of the high order elements. An optimization procedure is then used to both untangle invalid elements and optimize the geometrical accuracy of the mesh. Standard measures of the distance between curves are considered to evaluate the geometrical accuracy in planar two-dimensional meshes, but they prove computationally too costly for optimization purposes. A fast estimate of the geometrical accuracy, based on Taylor expansions of the curves, is introduced. An unconstrained optimization procedure based on this estimate is shown to yield significant improvements in the geometrical accuracy of high order meshes, as measured by the standard Haudorff distance between the geometrical model and the mesh. Several examples illustrate the beneficial impact of this method on CFD solutions, with a part...

  3. Different faces of chaos in FRW models with scalar fields -- geometrical point of view

    CERN Document Server

    Hrycyna, O; Hrycyna, Orest; Szydlowski, Marek

    2006-01-01

    FRW cosmologies with conformally coupled scalar fields are investigated in a geometrical way by the means of geodesics of the Jacobi metric. In this model of dynamics, trajectories in the configuration space are represented by geodesics. Because of the singular nature of the Jacobi metric on the boundary set $\\partial\\mathcal{D}$ of the domain of admissible motion, the geodesics change the cone sectors several times (or an infinite number of times) in the neighborhood of the singular set $\\partial\\mathcal{D}$. We show that this singular set contains interesting information about the dynamical complexity of the model. Firstly, this set can be used as a Poincar{\\'e} surface for construction of Poincar{\\'e} sections, and the trajectories then have the recurrence property. We also investigate the distribution of the intersection points. Secondly, the full classification of periodic orbits in the configuration space is performed and existence of UPO is demonstrated. Our general conclusion is that, although the pre...

  4. Mean-field dynamic criticality and geometric transition in the Gaussian core model

    Science.gov (United States)

    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.

  5. Spectra and neutron dose of an 18 MV Linac using two geometric models of the head

    International Nuclear Information System (INIS)

    Full text: Using the Monte Carlo method, by MCNP5 code, simulations were performed with different source terms and 2 geometric models of the head to obtain spectra in energy, flow and doses of photo-neutrons at different positions on the stretcher and in the radiotherapy room. The simplest model was a spherical shell of tungsten; the second was the complete model of a heterogeneous head of an accelerator Varian ix. In both models Tosi function was used as a source term. In addition, for the second model Sheikh-Bagheri distribution was used for photons and photo-neutrons were generated. Also in both models the radiotherapy room of Gurve group of the Teaching Medical Center La Trinidad was included, which is equipped with an accelerator Varian Clinic 2100. In this Center passive detectors PADC (Cr-39) were irradiated with neutron converters, with 18 MeV photons radiation. The measured neutron flow was compared with that obtained with Monte Carlo calculations. The Monte Carlo flows are similar to those measured at the isocenter. The simplest model underestimates the neutron flow compared with the calculated flows with the heterogeneous model of the head. (Author)

  6. New software library of geometrical primitives for modeling of solids used in Monte Carlo detector simulations

    International Nuclear Information System (INIS)

    We present our effort for the creation of a new software library of geometrical primitives, which are used for solid modeling in Monte Carlo detector simulations. We plan to replace and unify the current implementations for geometrical primitive classes in the software projects Geant4 and ROOT with this library. Each solid is implemented as a C++ class providing methods to compute distances of rays to the surface of a solid or to find whether a position is located inside, outside or on the surface of the solid. A numerical tolerance is used for determining whether a position is on the surface. The class methods also contain basic support for visualization. We use dedicated test suites for the validation of the code; these also include performance and consistency tests used for the analysis of candidate implementations of class methods for the new library. We have implemented simple adapter classes to allow the use of the new optimized solids with Geant4 and ROOT geometries.

  7. New software library of geometrical primitives for modeling of solids used in Monte Carlo detector simulations

    CERN Document Server

    Gayer, Marek; Cosmo, Gabriele; Gheata, Andrei; Guyader, Jean-Marie; Nikitina, Tatiana

    2012-01-01

    We present our effort for the creation of a new software library of geometrical primitives, which are used for solid modeling in Monte Carlo detector simulations. We plan to replace and unify the current implementations for geometrical primitive classes in the software projects Geant4 and ROOT with this library. Each solid is implemented as a C++ class providing methods to compute distances of rays to the surface of a solid or to find whether a position is located inside, outside or on the surface of the solid. A numerical tolerance is used for determining whether a position is on the surface. The class methods also contain basic support for visualization. We use dedicated test suites for the validation of the code, these also include performance and consistency tests used for the analysis of candidate implementations of class methods for the new library. We have implemented simple adapter classes to allow the use of the new optimized solids with Geant4 and ROOT geometries.

  8. Geometrical influence of pulmonary acinar models on respiratory flows and particle deposition

    Science.gov (United States)

    Hofemeier, Philipp; Sznitman, Josue

    2012-11-01

    Due to experimental challenges in assessing respiratory flows in the deep regions of the lungs, computational simulations are typically sought to quantify inhaled aerosol transport and deposition in the acinus. Most commonly, simulations are performed using generic geometries of alveoli, including spheres, toroids and polyhedra to mimic the acinar region. However, local respiratory flows and ensuing particle trajectories are anticipated to be highly influenced by the specific geometrical structures chosen. To date, geometrical influences have not yet been thoroughly quantified. Knowing beforehand how geometries affect acinar flows and particle transport is critical in translating simulated data to predictions of aerosol deposition in real lungs. Here, we conduct a systematic investigation on a number of generic acinar models. Simulations are conducted for simple alveolated airways featuring a selection of geometries. Deposition patterns and efficiencies are quantified both for massless particles, highlighting details of the local flow, and micron-scale aerosols. This latter group of particles represents an important class of inhaled aerosols known to reach and deposit in the acinus. Our work emphasizes the subtleties of acinar geometry in determining the fate of inhaled aerosols.

  9. Research on the measuring technology of minute part's geometrical parameter based on image processing

    Science.gov (United States)

    Jia, Xiao-yan; Xiao, Ze-xin

    2008-03-01

    The measuring technology of minute part's geometrical parameter based on image processing is an integration of optics, the mechanics, electronics, calculation and control. Accomplishing the video alteration of measuring microscope, real-time gathering image with CCD, and compiling automatically measuring software in Visual C++6.0 environment. First to do image processing which includes denoise filter, illuminance non-uniformity adjustment and image enhancement, then to carry on the on-line automatic measuring to its geometry parameters. By measuring the minute part's geometry parameters of machineries and integrated circuit in this system, the experimental results indicate that the measuring accuracy could amount to 1 micron, and the system survey stability and usability are all good.

  10. Enhancement of Generic Building Models by Recognition and Enforcement of Geometric Constraints

    Science.gov (United States)

    Meidow, J.; Hammer, H.; Pohl, M.; Bulatov, D.

    2016-06-01

    Many buildings in 3D city models can be represented by generic models, e.g. boundary representations or polyhedrons, without expressing building-specific knowledge explicitly. Without additional constraints, the bounding faces of these building reconstructions do not feature expected structures such as orthogonality or parallelism. The recognition and enforcement of man-made structures within model instances is one way to enhance 3D city models. Since the reconstructions are derived from uncertain and imprecise data, crisp relations such as orthogonality or parallelism are rarely satisfied exactly. Furthermore, the uncertainty of geometric entities is usually not specified in 3D city models. Therefore, we propose a point sampling which simulates the initial point cloud acquisition by airborne laser scanning and provides estimates for the uncertainties. We present a complete workflow for recognition and enforcement of man-made structures in a given boundary representation. The recognition is performed by hypothesis testing and the enforcement of the detected constraints by a global adjustment of all bounding faces. Since the adjustment changes not only the geometry but also the topology of faces, we obtain improved building models which feature regular structures and a potentially reduced complexity. The feasibility and the usability of the approach are demonstrated with a real data set.

  11. Optimizing wind farm layout via LES-calibrated geometric models inclusive of wind direction and atmospheric stability effects

    Science.gov (United States)

    Archer, Cristina; Ghaisas, Niranjan

    2015-04-01

    that can potentially block it. Based on blockage ratio and distance, an optimization procedure is proposed that explores many different layout variables and identifies, given actual wind direction and stability distributions, the optimal wind farm layout, i.e., the one with the highest wind energy production. The optimization procedure is applied to both the calibration wind farm (Lillgrund) and a test wind farm (Horns Rev) and a number of layouts more efficient than the existing ones are identified. The optimization procedure based on geometric models proposed here can be applied very quickly (within a few hours) to any proposed wind farm, once enough information on wind direction frequency and, if available, atmospheric stability frequency has been gathered and once the number of turbines and/or the areal extent of the wind farm have been identified.

  12. Geometrical mutual information at the tricritical point of the two-dimensional Blume-Capel model

    CERN Document Server

    Mandal, Ipsita; Melko, Roger G

    2016-01-01

    The spin-1 classical Blume-Capel model on a square lattice is known to exhibit a finite-temperature phase transition described by the tricritical Ising CFT in 1+1 space-time dimensions. This phase transition can be accessed with classical Monte Carlo simulations, which, via a replica-trick calculation, can be used to study the shape-dependence of the classical R\\'enyi entropies for a torus divided into two cylinders. From the second R\\'enyi entropy, we calculate the Geometrical Mutual Information (GMI) introduced by St\\'ephan et. al. [Phys. Rev. Lett. 112, 127204 (2014)] and use it to extract a numerical estimate for the value of the central charge near the tricritical point. By comparing to the known CFT result, $c=7/10$, we demonstrate how this type of GMI calculation can be used to estimate the position of the tricritical point in the phase diagram.

  13. Comparing Designers’ Problem-Solving Behavior in a Parametric Design Environment and a Geometric Modeling Environment

    Directory of Open Access Journals (Sweden)

    Ning Gu

    2013-09-01

    Full Text Available This paper presents the results of a protocol study which compares designers’ behavior in a parametric design environment (PDE and a geometric modeling environment (GME. An experiment was conducted in which seven designers were required to complete two architectural conceptual design tasks with similar complexity respectively in a PDE and GME. Protocol analysis is employed to compare the cognitive behavior of designers in these two environments. By analyzing the designers’ actions, including shifting between “problem” and “solution” spaces, it was possible to compare their cognitive activities in PDEs and GMEs. Results of this research suggest that designers put similar effort into the design problem space and the solution space in PDE and GME and that interaction between these two spaces also appears similar in the two design environments. However, different Problem-Solution index values and discontinuity ratios are found across design stages of the two design environments.

  14. A model for the origin and properties of flicker-induced geometric phosphenes.

    Directory of Open Access Journals (Sweden)

    Michael Rule

    2011-09-01

    Full Text Available We present a model for flicker phosphenes, the spontaneous appearance of geometric patterns in the visual field when a subject is exposed to diffuse flickering light. We suggest that the phenomenon results from interaction of cortical lateral inhibition with resonant periodic stimuli. We find that the best temporal frequency for eliciting phosphenes is a multiple of intrinsic (damped oscillatory rhythms in the cortex. We show how both the quantitative and qualitative aspects of the patterns change with frequency of stimulation and provide an explanation for these differences. We use Floquet theory combined with the theory of pattern formation to derive the parameter regimes where the phosphenes occur. We use symmetric bifurcation theory to show why low frequency flicker should produce hexagonal patterns while high frequency produces pinwheels, targets, and spirals.

  15. A Wave-Optics Approach to Paraxial Geometrical Laws Based on Continuity at Boundaries

    Science.gov (United States)

    Linares, J.; Nistal, M. C.

    2011-01-01

    We present a derivation of the paraxial geometrical laws starting from a wave-optics approach, in particular by using simple continuity conditions of paraxial spherical waves at boundaries (discontinuities) between optical media. Paraxial geometrical imaging and magnification laws, under refraction and reflection at boundaries, are derived for…

  16. From species abundance to opal input: Simple geometrical models of radiolarian skeletons from the Atlantic sector of the Southern Ocean

    Science.gov (United States)

    Jacot Des Combes, H.; Abelmann, A.

    2009-05-01

    Radiolarian-based paleoceanographic reconstructions generally use the abundance of selected radiolarian species. However, the recent focus on the opal flux and the development of isotope measurements in biogenic opal and the organic matter embedded in it demands a better knowledge of the origin of the opal. We present here an estimation of the opal content of the skeleton of 63 radiolarian species from two sites in the Southern Ocean. The skeletons are modelled as associations of simple geometrical shapes, and the volume thus obtained is combined with opal density to obtain the amount of opal. These data are, thus, used to determine the most important opal carriers in the radiolarian assemblage in both cores.

  17. A full photometric and geometric model for attached webcam/matte screen devices

    OpenAIRE

    Quéau, Yvain; Modrzejewski, Richard; Gurdjos, Pierre; Durou, Jean-Denis

    2016-01-01

    International audience We present a thorough photometric and geometric study of the multimedia devices composed of both a matte screen and an attached camera, where it is shown that the light emitted by an image displayed on the monitor can be expressed in closed-form at any point facing the screen, and that the geometric calibration of the camera attached to the screen can be simplified by introducing simple geometric constraints. These theoretical contributions are experimentally validat...

  18. Uncertainties in modeling, prediction, and actions in response to variations in patient geometric models

    Science.gov (United States)

    Kashani, Rojano

    External beam radiation therapy is an effective method for treating cancer in many body sites. Highly conformal plans can be created to provide good target coverage while sparing the surrounding normal tissue. A fundamental problem in delivering these conformal plans is the inter- and intra-fractional variations in patient geometry, which result in deviation of the delivered dose from the planned dose, thus reducing the probability of tumor control or increasing the risk of normal tissue toxicity. To address this problem, various motion management strategies have been implemented in the clinic, and several others are under investigation. While the technique employed for management of geometric variation can change depending on the type and source of the variation (set up error, respiratory-induced motion and deformation, or tumor shrinkage or tissue loss in response to treatment) as well as other clinical factors, all these techniques have one thing in common and that is the fact that they are not perfect. This work investigates the uncertainties associated with the measurement and management of motion and deformation, and evaluates the impact of these uncertainties on the accuracy of geometry and dose tracking for treatment adaptation. This research quantified the magnitude and distribution of error in deformable image registration for aligning image volumes acquired at different breathing states. It further explored the potential of reducing the registration error in deforming lung geometry, by applying a method from multivariate statistics (principal component analysis) to identify the significant modes of variation in this geometry. It also demonstrated the potential for tracking respiratory induced deformation in various regions in the lung, using a few surrogates such as implanted markers. In addition to the evaluation of registration error for thoracic geometry affected by respiratory motion, this work also investigates the accuracy of deformable image

  19. Competition and fixation of cohorts of adaptive mutations under Fisher geometrical model.

    Science.gov (United States)

    Moura de Sousa, Jorge A; Alpedrinha, João; Campos, Paulo R A; Gordo, Isabel

    2016-01-01

    One of the simplest models of adaptation to a new environment is Fisher's Geometric Model (FGM), in which populations move on a multidimensional landscape defined by the traits under selection. The predictions of this model have been found to be consistent with current observations of patterns of fitness increase in experimentally evolved populations. Recent studies investigated the dynamics of allele frequency change along adaptation of microbes to simple laboratory conditions and unveiled a dramatic pattern of competition between cohorts of mutations, i.e., multiple mutations simultaneously segregating and ultimately reaching fixation. Here, using simulations, we study the dynamics of phenotypic and genetic change as asexual populations under clonal interference climb a Fisherian landscape, and ask about the conditions under which FGM can display the simultaneous increase and fixation of multiple mutations-mutation cohorts-along the adaptive walk. We find that FGM under clonal interference, and with varying levels of pleiotropy, can reproduce the experimentally observed competition between different cohorts of mutations, some of which have a high probability of fixation along the adaptive walk. Overall, our results show that the surprising dynamics of mutation cohorts recently observed during experimental adaptation of microbial populations can be expected under one of the oldest and simplest theoretical models of adaptation-FGM. PMID:27547562

  20. Automatic Geometric Processing for Very High Resolution Optical Satellite Data Based on Vector Roads and Orthophotos

    Directory of Open Access Journals (Sweden)

    Peter Pehani

    2016-04-01

    Full Text Available In response to the increasing need for fast satellite image processing SPACE-SI developed STORM—a fully automatic image processing chain that performs all processing steps from the input optical images to web-delivered map-ready products for various sensors. This paper focuses on the automatic geometric corrections module and its adaptation to very high resolution (VHR multispectral images. In the automatic ground control points (GCPs extraction sub-module a two-step algorithm that utilizes vector roads as a reference layer and delivers GCPs for high resolution RapidEye images with near pixel accuracy was initially implemented. Super-fine positioning of individual GCPs onto an aerial orthophoto was introduced for VHR images. The enhanced algorithm is capable of achieving accuracy of approximately 1.5 pixels on WorldView-2 data. In the case of RapidEye images the accuracies of the physical sensor model reach sub-pixel values at independent check points. When compared to the reference national aerial orthophoto the accuracies of WorldView-2 orthoimages automatically produced with the rational function model reach near-pixel values. On a heterogeneous set of 41 RapidEye images the rate of automatic processing reached 97.6%. Image processing times remained under one hour for standard-size images of both sensor types.

  1. Testing coordinate measuring arms with a geometric feature-based gauge: in situ field trials

    Science.gov (United States)

    Cuesta, E.; Alvarez, B. J.; Patiño, H.; Telenti, A.; Barreiro, J.

    2016-05-01

    This work describes in detail the definition of a procedure for calibrating and evaluating coordinate measuring arms (AACMMs or CMAs). CMAs are portable coordinate measuring machines that have been widely accepted in industry despite their sensitivity to the skill and experience of the operator in charge of the inspection task. The procedure proposed here is based on the use of a dimensional gauge that incorporates multiple geometric features, specifically designed for evaluating the measuring technique when CMAs are used, at company facilities (workshops or laboratories) and by the usual operators who handle these devices in their daily work. After establishing the procedure and manufacturing the feature-based gauge, the research project was complemented with diverse in situ field tests performed with the collaboration of companies that use these devices in their inspection tasks. Some of the results are presented here, not only comparing different operators but also comparing different companies. The knowledge extracted from these experiments has allowed the procedure to be validated, the defects of the methodologies currently used for in situ inspections to be detected, and substantial improvements for increasing the reliability of these portable instruments to be proposed.

  2. Computer Vision Based Method and System for Online Measurement of Geometric Parameters of Train Wheel Sets

    Directory of Open Access Journals (Sweden)

    Hong-Jun Yang

    2011-12-01

    Full Text Available Train wheel sets must be periodically inspected for possible or actual premature failures and it is very significant to record the wear history for the full life of utilization of wheel sets. This means that an online measuring system could be of great benefit to overall process control. An online non-contact method for measuring a wheel set’s geometric parameters based on the opto-electronic measuring technique is presented in this paper. A charge coupled device (CCD camera with a selected optical lens and a frame grabber was used to capture the image of the light profile of the wheel set illuminated by a linear laser. The analogue signals of the image were transformed into corresponding digital grey level values. The ‘mapping function method’ is used to transform an image pixel coordinate to a space coordinate. The images of wheel sets were captured when the train passed through the measuring system. The rim inside thickness and flange thickness were measured and analyzed. The spatial resolution of the whole image capturing system is about 0.33 mm. Theoretic and experimental results show that the online measurement system based on computer vision can meet wheel set measurement requirements.

  3. Geometrical tuning art for entirely subwavelength grating waveguide based integrated photonics circuits

    Science.gov (United States)

    Wang, Zheng; Xu, Xiaochuan; Fan, Donglei; Wang, Yaguo; Subbaraman, Harish; Chen, Ray T.

    2016-05-01

    Subwavelength grating (SWG) waveguide is an intriguing alternative to conventional optical waveguides due to the extra degree of freedom it offers in tuning a few important waveguide properties, such as dispersion and refractive index. Devices based on SWG waveguides have demonstrated impressive performances compared to conventional waveguides. However, the high loss of SWG waveguide bends jeopardizes their applications in integrated photonic circuits. In this work, we propose a geometrical tuning art, which realizes a pre-distorted refractive index profile in SWG waveguide bends. The pre-distorted refractive index profile can effectively reduce the mode mismatch and radiation loss simultaneously, thus significantly reduce the bend loss. This geometry tuning art has been numerically optimized and experimentally demonstrated in present study. Through such tuning, the average insertion loss of a 5 μm SWG waveguide bend is reduced drastically from 5.43 dB to 1.10 dB per 90° bend for quasi-TE polarization. In the future, the proposed scheme will be utilized to enhance performance of a wide range of SWG waveguide based photonics devices.

  4. Testing coordinate measuring arms with a geometric feature-based gauge: in situ field trials

    International Nuclear Information System (INIS)

    This work describes in detail the definition of a procedure for calibrating and evaluating coordinate measuring arms (AACMMs or CMAs). CMAs are portable coordinate measuring machines that have been widely accepted in industry despite their sensitivity to the skill and experience of the operator in charge of the inspection task. The procedure proposed here is based on the use of a dimensional gauge that incorporates multiple geometric features, specifically designed for evaluating the measuring technique when CMAs are used, at company facilities (workshops or laboratories) and by the usual operators who handle these devices in their daily work. After establishing the procedure and manufacturing the feature-based gauge, the research project was complemented with diverse in situ field tests performed with the collaboration of companies that use these devices in their inspection tasks. Some of the results are presented here, not only comparing different operators but also comparing different companies. The knowledge extracted from these experiments has allowed the procedure to be validated, the defects of the methodologies currently used for in situ inspections to be detected, and substantial improvements for increasing the reliability of these portable instruments to be proposed. (paper)

  5. Towards modelling of the frictional behaviour of deforming fibrous tows: A geometrical approach

    NARCIS (Netherlands)

    Cornelissen, Bo; Akkerman, Remko

    2010-01-01

    Fibrous tows used in continuous fibre-reinforced polymers (CFRPs) deform geometrically during the production of composite products. The cross-sectional geometry of the tow is influenced by the load-induced deformation mechanisms. A study of the effect of two commonly assumed geometrical tow shapes o

  6. Geometric models of statistical physics: billiard in a symmetric phase space

    International Nuclear Information System (INIS)

    The billiard problem of statistical physics is considered in a new geometric approach with a symmetric phase space. The structure and topological features of typical billiard phase portrait are defined. The connection between geometric, dynamic and statistic properties of smooth billiard is established

  7. Generalised Geometrical CP Violation in a $T^{\\prime}$ Lepton Flavour Model

    CERN Document Server

    Girardi, Ivan; Petcov, S T; Spinrath, Martin

    2014-01-01

    We analyse the interplay of generalised CP transformations and the non-Abelian discrete group $T^{\\prime}$ and use the semi-direct product $G_f= T^{\\prime}\\rtimes H_{\\text{CP}}$, 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 $\\delta$ in the lepton mixing matrix is predicted to be $\\delta \\cong \\pi/2~{\\rm or}~ 3\\pi/2$. Thus, the CP violating effects in ...

  8. Geometric analysis of the Goldbeter minimal model for the embryonic cell cycle.

    Science.gov (United States)

    Kosiuk, Ilona; Szmolyan, Peter

    2016-04-01

    A minimal model describing the embryonic cell division cycle at the molecular level in eukaryotes is analyzed mathematically. It is known from numerical simulations that the corresponding three-dimensional system of ODEs has periodic solutions in certain parameter regimes. We prove the existence of a stable limit cycle and provide a detailed description on how the limit cycle is generated. The limit cycle corresponds to a relaxation oscillation of an auxiliary system, which is singularly perturbed and has the same orbits as the original model. The singular perturbation character of the auxiliary problem is caused by the occurrence of small Michaelis constants in the model. Essential pieces of the limit cycle of the auxiliary problem consist of segments of slow motion close to several branches of a two dimensional critical manifold which are connected by fast jumps. In addition, a new phenomenon of exchange of stability occurs at lines, where the branches of the two-dimensional critical manifold intersect. This novel type of relaxation oscillations is studied by combining standard results from geometric singular perturbation with several suitable blow-up transformations. PMID:26100376

  9. ANALYSIS OF ACCELERATED LIFE TESTING USING LOG-LOGISTIC GEOMETRIC PROCESS MODEL IN CASE OF CENSORED DATA

    Directory of Open Access Journals (Sweden)

    S. SAXENA

    2013-07-01

    Full Text Available Geometric process model has been used in a variety of situations such as the determination of the optimal replacement policy and the optimal inspection-repair replacement policy for standby systems, and the analysis of data with trends. This study deals with the analysis of accelerated life testing for Log-Logistic distribution using geometric process model. The case of type-I censoring is considered in this study. It is assumed that the lifetimes under increasing stress levels form a geometric process. The maximum likelihood estimates of the parameters and their confidence intervals using the asymptotic method are derived. The performance of the estimators is evaluated by a simulation study with different pre-fixed parameters.

  10. Shift of absorption energy during thin dye film growth: interpretation by geometric models of the growth morphology

    International Nuclear Information System (INIS)

    We measure absorption spectra of two different perylene molecules in thin films with thicknesses varied between 1 and 30 nm physical vapor deposited on glass substrates. Atomic force microscopy (reveals the formation of crystallized needles for N, N'-dimethyl perylene tetracarboxylic acid diimide and amorphous round-shaped islands for 1,6,7,12-tetrachloro-N,N'-dimethyl perylene tetracarboxylic. For both molecules, a spectral shift of the lowest energy transition to lower energies was observed with increasing film thickness. Common models taking electric fields, electronic coupling or exciton confinement into account cannot completely describe the observed spectral shift. Here we show that the experimental values can be fitted with an advanced layering model based on the energetic difference between bulk and interface/surface materials. In contrast to the known simple d−1 model, which describes the energetic shift for the special case of a layer-by-layer growth, we extend this idea to other film morphologies. - Highlights: • Description of energetic shift of transition energy of organic thin films. • Relation of differences in shift with film morphologies. • Theoretical explanation based on geometric considerations

  11. Shift of absorption energy during thin dye film growth: interpretation by geometric models of the growth morphology

    Energy Technology Data Exchange (ETDEWEB)

    Trenkmann, Ines; Borczyskowski, Christian von; Graaf, Harald, E-mail: graaf@uni-bremen.de

    2014-12-31

    We measure absorption spectra of two different perylene molecules in thin films with thicknesses varied between 1 and 30 nm physical vapor deposited on glass substrates. Atomic force microscopy (reveals the formation of crystallized needles for N, N'-dimethyl perylene tetracarboxylic acid diimide and amorphous round-shaped islands for 1,6,7,12-tetrachloro-N,N'-dimethyl perylene tetracarboxylic. For both molecules, a spectral shift of the lowest energy transition to lower energies was observed with increasing film thickness. Common models taking electric fields, electronic coupling or exciton confinement into account cannot completely describe the observed spectral shift. Here we show that the experimental values can be fitted with an advanced layering model based on the energetic difference between bulk and interface/surface materials. In contrast to the known simple d{sup −1} model, which describes the energetic shift for the special case of a layer-by-layer growth, we extend this idea to other film morphologies. - Highlights: • Description of energetic shift of transition energy of organic thin films. • Relation of differences in shift with film morphologies. • Theoretical explanation based on geometric considerations.

  12. Extraction of Geometric Features of Wear Particles in Color Ferrograph Images Based on RGB Color Space

    Institute of Scientific and Technical Information of China (English)

    CHEN Gui-ming; WANG Han-gong; ZHANG Bao-jun; PAN Wei

    2003-01-01

    This paper analyzes the potential color formats of ferrograph images, and presents the algorithms of converting the formats to RGB(Red, Green, Blue) color space. Through statistical analysis of wear par-ticles' geometric features of color ferrograph images in the RGB color space, we give the differences of ferro-graph wear panicles' geometric features among RGB color spaces and gray scale space, and calculate their respective distributions.

  13. Bat Species Comparisons Based on External Morphology : A Test of Traditional versus Geometric Morphometric Approaches

    OpenAIRE

    Schmieder, Daniela A.; Hugo A. Benítez; Ivailo M Borissov; Carmelo Fruciano

    2015-01-01

    External morphology is commonly used to identify bats as well as to investigate flight and foraging behavior, typically relying on simple length and area measures or ratios. However, geometric morphometrics is increasingly used in the biological sciences to analyse variation in shape and discriminate among species and populations. Here we compare the ability of traditional versus geometric morphometric methods in discriminating between closely related bat species – in this case European horse...

  14. Structural damage identification based on change in geometric modal strain energy–eigenvalue ratio

    Science.gov (United States)

    Nguyen, Khac-Duy; Chan, Tommy HT; Thambiratnam, David P.

    2016-07-01

    This study presents a new damage identification method to locate and quantify damage using measured mode shapes and natural frequencies. A new vibration parameter, ratio of geometric modal strain energy to eigenvalue (GMSEE), has been developed and its change due to stiffness reduction has been formulated using a sensitivity matrix. This sensitivity matrix is estimated with measured modal parameters and basic information of the structure. For damage identification, firstly, the locations of damage and the correlative damage extents are identified by maximizing the correlation level between an analytical GMSEE change vector and a measured one. Herein, the genetic algorithm, which is a powerful evolutionary optimization algorithm, is utilized to solve this optimization problem. Secondly, the size of damage can be estimated using the proposed GMSEE technique and compared with a conventional technique using frequency change. A numerical 2D Truss bridge is used to demonstrate the performance of the proposed method in identifying single and multiple damage cases. Also, practicality of the method is tested with a laboratory eight degree-of-freedom system and a real bridge. Results illustrate the high capability of the method to identify structural damage with less modeling efforts.

  15. A stochastic-geometric model of soil variation in Pleistocene patterned ground

    Science.gov (United States)

    Lark, Murray; Meerschman, Eef; Van Meirvenne, Marc

    2013-04-01

    In this paper we examine the spatial variability of soil in parent material with complex spatial structure which arises from complex non-linear geomorphic processes. We show that this variability can be better-modelled by a stochastic-geometric model than by a standard Gaussian random field. The benefits of the new model are seen in the reproduction of features of the target variable which influence processes like water movement and pollutant dispersal. Complex non-linear processes in the soil give rise to properties with non-Gaussian distributions. Even under a transformation to approximate marginal normality, such variables may have a more complex spatial structure than the Gaussian random field model of geostatistics can accommodate. In particular the extent to which extreme values of the variable are connected in spatially coherent regions may be misrepresented. As a result, for example, geostatistical simulation generally fails to reproduce the pathways for preferential flow in an environment where coarse infill of former fluvial channels or coarse alluvium of braided streams creates pathways for rapid movement of water. Multiple point geostatistics has been developed to deal with this problem. Multiple point methods proceed by sampling from a set of training images which can be assumed to reproduce the non-Gaussian behaviour of the target variable. The challenge is to identify appropriate sources of such images. In this paper we consider a mode of soil variation in which the soil varies continuously, exhibiting short-range lateral trends induced by local effects of the factors of soil formation which vary across the region of interest in an unpredictable way. The trends in soil variation are therefore only apparent locally, and the soil variation at regional scale appears random. We propose a stochastic-geometric model for this mode of soil variation called the Continuous Local Trend (CLT) model. We consider a case study of soil formed in relict patterned

  16. A Study of the Anechoic Performance of Rice Husk-Based, Geometrically Tapered, Hollow Absorbers

    Directory of Open Access Journals (Sweden)

    Muhammad Nadeem Iqbal

    2014-01-01

    Full Text Available Although solid, geometrically tapered microwave absorbers are preferred due to their better performance, they are bulky and must have a thickness on the order of λ or more. The goal of this study was to design lightweight absorbers that can reduce the electromagnetic reflections to less than −10 dB. We used a very simple approach; two waste materials, that is, rice husks and tire dust in powder form, were used to fabricate two independent samples. We measured and used their dielectric properties to determine and compare the propagation constants and quarter-wave thickness. The quarter-wave thickness for the tire dust was 3 mm less than that of the rice husk material, but we preferred the rice-husk material. This preference was based on the fact that our goal was to achieve minimum backward reflections, and the rice-husk material, with its low dielectric constant, high loss factor, large attenuation per unit length, and ease of fabrication, provided a better opportunity to achieve that goal. The performance of the absorbers was found to be better (lower than −20 dB, and comparison of the results proved that the hollow design with 58% less weight was a good alternative to the use of solid absorbers.

  17. An iris localization algorithm based on geometrical features of cow eyes

    Science.gov (United States)

    Zhang, Menglu; Zhao, Lindu; Kong, Qiang

    2009-10-01

    Abrupt vicious affairs on meat food safety show rapid expansion, which poses a threat to food safety and human health. In order to trace the flow of meat products in the food supply chain, the research on the individual identification of large animals based on iris recognition has very important practical significance. Iris localization is the key step in the iris recognition system, and this paper makes the cow iris as an example to propose two-step localization method on the basis of studying and analyzing lots of cow geometrical features. Firstly, threshold transform and Sobel edge detection operator are used to make the image binarization processing and realize coarse location, and the coordinates of boundary points are determined with the quadratic B-spline interpolation curves. Secondly, the cow eye iris image is located from the coarseness to fine through fitting circles. This paper proposes two methods to determine the parameters of the inner and outer boundary circles, including fitting concentric and non-concentric circle. Experimental results show that fitting non-concentric circle algorithm can locate iris region quickly and efficiently and has better accuracy and good robustness.

  18. Geometric accuracy of a novel gimbals based radiation therapy tumor tracking system

    International Nuclear Information System (INIS)

    Purpose: VERO is a novel platform for image guided stereotactic body radiotherapy. Orthogonal gimbals hold the linac-MLC assembly allowing real-time moving tumor tracking. This study determines the geometric accuracy of the tracking. Materials and methods: To determine the tracking error, an 1D moving phantom produced sinusoidal motion with frequencies up to 30 breaths per minute (bpm). Tumor trajectories of patients were reproduced using a 2D robot and pursued with the gimbals tracking system prototype. Using the moving beam light field and a digital-camera-based detection unit tracking errors, system lag and equivalence of pan/tilt performance were measured. Results: The system lag was 47.7 ms for panning and 47.6 ms for tilting. Applying system lag compensation, sinusoidal motion tracking was accurate, with a tracking error 90% percentile E90% 90% of 0.54 mm, and tracking error standard deviations of 0.20 mm for pan and 0.22 mm for tilt. Conclusions: In terms of dynamic behavior, the gimbaled linac of the VERO system showed to be an excellent approach for providing accurate real-time tumor tracking in radiation therapy.

  19. Object-Based Analysis of LIDAR Geometric Features for Vegetation Detection in Shaded Areas

    Science.gov (United States)

    Lin, Yu-Ching; Lin, ChinSu; Tsai, Ming-Da; Lin, Chun-Lin

    2016-06-01

    The extraction of land cover information from remote sensing data is a complex process. Spectral information has been widely utilized in classifying remote sensing images. However, shadows limit the use of multispectral images because they result in loss of spectral radiometric information. In addition, true reflectance may be underestimated in shaded areas. In land cover classification, shaded areas are often left unclassified or simply assigned as a shadow class. Vegetation indices from remote sensing measurement are radiation-based measurements computed through spectral combination. They indicate vegetation properties and play an important role in remote sensing of forests. Airborne light detection and ranging (LiDAR) technology is an active remote sensing technique that produces a true orthophoto at a single wavelength. This study investigated three types of geometric lidar features where NDVI values fail to represent meaningful forest information. The three features include echo width, normalized eigenvalue, and standard deviation of the unit weight observation of the plane adjustment, and they can be derived from waveform data and discrete point clouds. Various feature combinations were carried out to evaluate the compensation of the three lidar features to vegetation detection in shaded areas. Echo width was found to outperform the other two features. Furthermore, surface characteristics estimated by echo width were similar to that by normalized eigenvalues. Compared to the combination of only NDVI and mean height difference, those including one of the three features had a positive effect on the detection of vegetation class.

  20. A Location-Based Service Using Geometric Location Methods to Unite Mobile Users

    Directory of Open Access Journals (Sweden)

    Wen-Chen Hu

    2016-02-01

    Full Text Available Since the introduction of iPhone in 2007, many location-based services (LBSs have been created and new LBSs are found every day. This research proposes yet another LBS, which is practical and was not found before to the best of authors' knowledge. The problem is described as follows. It happens all the times while several groups of people are traveling towards a destination, they lose contact from each other on the way. This research tries to have the groups travel as closely as possible until they reach the destination. It uses a method of minimum covering ellipses to find whether the groups are separated by more than a threshold/distance. If they are, the system will find a convenient rendezvous for all groups by using a method of geometric median. After meeting at the rendezvous, the groups reset the service and continue their journey. By using this LBS, travelers do not need to worry about losing connections with others. This method can also be applied to the problem of finding a convenient meeting place for mobile users.

  1. Numerical analysis of bypass model geometrical parameters influence on pulsatile blood flow

    Directory of Open Access Journals (Sweden)

    Jonášová A.

    2011-06-01

    Full Text Available The present study is focused on the analysis of pulsatile blood flow in complete idealized 3D bypass models in dependence on three main geometrical parameters (stenosis degree, junction angle and diameter ratio. Assuming the blood to be an incompressible Newtonian fluid, the non-linear system of Navier-Stokes equations is integrated in time by a fully implicit second-order accurate fractional-step method. The space discretization is performed with the help of the cell-centred finite volume method formulated for unstructured tetrahedral grids. In order to model a realistic coronary blood flow, a time-dependent flow rate taken from corresponding literature is considered. For the analysis of obtained numerical results, special emphasis is placed on their comparison in the form of velocity isolines at several selected cross-sections during systolic and diastolic phases. The remainder of this paper is devoted to discussion of walls shear stress distribution and its oscillatory character described by the oscillatory shear index with regard to areas prone to development of intimal hyperplasia or to thrombus formation.

  2. Towards Geometric D6-Brane Model Building on non-Factorisable Toroidal $\\mathbb{Z}_4$-Orbifolds

    CERN Document Server

    Berasaluce-González, Mikel; Seifert, Alexander

    2016-01-01

    We present a geometric approach to D-brane model building on the non-factorisable torus backgrounds of $T^6/\\mathbb{Z}_4$, which are $A_3 \\times A_3$ and $A_3 \\times A_1 \\times B_2$. Based on the counting of `short' supersymmetric three-cycles per complex structure {\\it vev}, the number of physically inequivalent lattice orientations with respect to the anti-holomorphic involution ${\\cal R}$ of the Type IIA/$\\Omega\\cal{R}$ orientifold can be reduced to three for the $A_3 \\times A_3$ lattice and four for the $A_3 \\times A_1 \\times B_2$ lattice. While four independent three-cycles on $A_3 \\times A_3$ cannot accommodate phenomenologically interesting global models with a chiral spectrum, the eight-dimensional space of three-cycles on $A_3 \\times A_1 \\times B_2$ is rich enough to provide for particle physics models, with several globally consistent two- and four-generation Pati-Salam models presented here. We further show that for fractional {\\it sLag} three-cycles, the compact geometry can be rewritten in a $(T^...

  3. Microscopic foundation and geometric interpretation of the interacting-boson model

    International Nuclear Information System (INIS)

    A number of aspects of the relation between the shell model and the interacting-boson model are studied. The IBM is assumed to describe that part of the shell-model space where all states are built from selected, correlated pairs with angular momentum zero or two, which are mapped onto bosons. The goal of a microscopic derivation of IBM is to determine this subspace and to obtain the parameters that govern the dynamics in boson space. A formalism is introduced to calculate the expectation value of the hamiltonian between states containing such correlated fermion pairs. This formalism only applies to spherical nuclei, where zero-coupled pairs dominate. It is applied to the semimagic tin nuclei. Several methods are compared to determine the structure of the collective pairs in order to find a method which gives the 'best pairs'. The formalism is also applied to the mercury isotopes for which both neutrons and protons are active. In this more realistic case the above-mentioned methods to determine the pairs are also studied. The IBM-2 parameters are derived from the microscopic calculation. Group-theoretical aspects of the SU(3) limits of IBM-1 and IBM-2 are investigated. A complete decomposition for the SU(3) limits is given. Specific attention is paid to the 'triaxial-rotor' SU(3)*-limit, which is thought to describe nuclei with a triaxial shape. The SU(3)* symmetry of IBM-2 is applied in a study of the 192Os nucleus. The relation between IBM and geometrical models is discussed. (Auth.)

  4. The Definition and Computation of a Metric on Plane Curves. The Meaning of a Face on a Geometric Model

    Science.gov (United States)

    Emery, J. D.

    1985-01-01

    Two topics in topology, the comparison of plane curves and faces on geometric models, are discussed. With regard to the first problem, a curve is defined to be a locus of points without any underlying parameterization. A metric on a class of plane curves is defined, a finite computation of this metric is given for the case of piecewise linear curves, and it is shown how to approximate curves that have bounded curvature by piecewise linear curves. In this way a bound on the distance between two curves can be computed. With regard to the second problem, the questions to be discussed are under what circumstances do geometrical faces make sense; how can they be explicity defined; and when are these geometrical faces homeomorphic to the realization of the abstract (topological) face.

  5. Geometrical Bioelectrodynamics

    OpenAIRE

    Ivancevic, Vladimir G.; Ivancevic, Tijana T.

    2008-01-01

    This paper proposes rigorous geometrical treatment of bioelectrodynamics, underpinning two fast-growing biomedical research fields: bioelectromagnetism, which deals with the ability of life to produce its own electromagnetism, and bioelectromagnetics, which deals with the effect on life from external electromagnetism. Keywords: Bioelectrodynamics, exterior geometrical machinery, Dirac-Feynman quantum electrodynamics, functional electrical stimulation

  6. A simple geometric validation approach to assess the basic behaviour of space- and time- distributed models of epidemic spread - an example using the Ontario rabies model.

    Science.gov (United States)

    Ludwig, A; Berthiaume, P; Richer, J; Tinline, R; Bigras-Poulin, M

    2014-04-01

    Dynamic mathematical modelling and stochastic simulation of disease-host systems for the purpose of epidemiological analysis offer great opportunities for testing hypotheses, especially when field experiments are impractical or when there is a need to evaluate multiple experimental scenarios. This, combined with the ever increasing computer power available to researchers, has contributed to the development of many mathematical models for epidemic simulations, such as the individual-based model (IBM). Nevertheless, few of these models undergo extensive validation and proper assessment of intrinsic variability. The Ontario rabies model (ORM) will be used here to exemplify some advantages of appropriate model behaviour validation and to illustrate the use of a simple geometric procedure for testing directional bias in distributed stochastic dynamic model of spread of diseases. Results were obtained through the comparison of 10 000 epizootics resulting from 100 epidemic simulations started using 100 distinct base populations. The analysis results demonstrated a significant directional bias in epidemic dispersion, which prompted further verification of the model code and the identification of a coding error, which was then corrected. Subsequent testing of the corrected code showed that the directional bias could no longer be detected. These results illustrate the importance of proper validation and the importance of sufficient knowledge of the model behaviour to ensure the results will not confound the objectives of the end-users. PMID:23750567

  7. Towards modelling of the frictional behaviour of deforming fibrous tows: A geometrical approach

    OpenAIRE

    Cornelissen, Bo; Akkerman, Remko

    2010-01-01

    Fibrous tows used in continuous fibre-reinforced polymers (CFRPs) deform geometrically during the production of composite products. The cross-sectional geometry of the tow is influenced by the load-induced deformation mechanisms. A study of the effect of two commonly assumed geometrical tow shapes on an equivalent pressure distribution in a tow-on-a-pin spreading arrangement was performed. The preliminary results show that both elliptic and parabolic tow geometries have qualitatively the comp...

  8. Geometric leaf placement strategies

    International Nuclear Information System (INIS)

    Geometric leaf placement strategies for multileaf collimators (MLCs) typically involve the expansion of the beam's-eye-view contour of a target by a uniform MLC margin, followed by movement of the leaves until some point on each leaf end touches the expanded contour. Film-based dose-distribution measurements have been made to determine appropriate MLC margins-characterized through an index d90-for multileaves set using one particular strategy to straight lines lying at various angles to the direction of leaf travel. Simple trigonometric relationships exist between different geometric leaf placement strategies and are used to generalize the results of the film work into d90 values for several different strategies. Measured d90 values vary both with angle and leaf placement strategy. A model has been derived that explains and describes quite well the observed variations of d90 with angle. The d90 angular variations of the strategies studied differ substantially, and geometric and dosimetric reasoning suggests that the best strategy is the one with the least angular variation. Using this criterion, the best straightforwardly implementable strategy studied is a 'touch circle' approach for which semicircles are imagined to be inscribed within leaf ends, the leaves being moved until the semicircles just touch the expanded target outline

  9. Fisher's geometric model predicts the effects of random mutations when tested in the wild.

    Science.gov (United States)

    Stearns, Frank W; Fenster, Charles B

    2016-02-01

    Fisher's geometric model of adaptation (FGM) has been the conceptual foundation for studies investigating the genetic basis of adaptation since the onset of the neo Darwinian synthesis. FGM describes adaptation as the movement of a genotype toward a fitness optimum due to beneficial mutations. To date, one prediction of FGM, the probability of improvement is related to the distance from the optimum, has only been tested in microorganisms under laboratory conditions. There is reason to believe that results might differ under natural conditions where more mutations likely affect fitness, and where environmental variance may obscure the expected pattern. We chemically induced mutations into a set of 19 Arabidopsis thaliana accessions from across the native range of A. thaliana and planted them alongside the premutated founder lines in two habitats in the mid-Atlantic region of the United States under field conditions. We show that FGM is able to predict the outcome of a set of random induced mutations on fitness in a set of A. thaliana accessions grown in the wild: mutations are more likely to be beneficial in relatively less fit genotypes. This finding suggests that FGM is an accurate approximation of the process of adaptation under more realistic ecological conditions. PMID:26768168

  10. Crystal bases and quiver varieties (Geometric construction of crystal bases II)

    OpenAIRE

    Saito, Yoshihisa

    2001-01-01

    We give a crystal structure on the set of all irreducible components of Lagrangian subvarieties of quiver varieties. One con show that, as a crystal, it is isomorphic to the crystal base of an irreducible highest weight representation of a quantized universal enveloping algebra.

  11. Point-based approach to enhance the quality of geometric data for CAE applications

    OpenAIRE

    Ball, A.; Cripps, R J; J. Lin; Loftus, M

    2010-01-01

    Abstract Commercial CAD surface modelling software is based almost exclusively on Bezier, B-spline and NURBS representations. These methods offer simple interactive shape modification and computationally efficient interrogations, but have some serious practical limitations. The root cause of all these problems is that the parametric polynomial methods are not geometry-based, and the trouble is compounded by the master geometry philosophy which treats the CAD model as if it were abs...

  12. Geometrical models of quadratic-rectangular sets with particular examples of composite solutions

    Directory of Open Access Journals (Sweden)

    Polezhaev Yuriy Olegovich

    Full Text Available During the current decades the aspect of geometrography compositions formation on the basis of basic images has been actively developed. The basic images possess the qualities of harmonies, expressed by lines, squares, tone, color. The relations of square-rectangular forms belonging to plane geometry of parabolic, hyperbolic and elliptic fields has been already analyzed by scientists. This article introduces equiareals construction of square-rectangular shapes, as well as their rows - in classical composition of elementary figures of "squaring the circle". Variations of such constructions, in their turn, offer the possibility to seek and capture new geometrical graphical compositions, practical application of which can be wide enough in technology design and mechanical engineering, architecture and construction, decoration of household items, arts and crafts and costume fabrics, et cetera. The authors consider the topic of plane geometry "Field-M", which is based on a rectilinear grid of ortholines with circulations in its nodal points. The conclusions made by the authors is that the necessity of solutions for more and more various and complicated problems in the conditions of time limitation determines the development of geometrography methods as an effective operating system along with program methods of cognitive graphics.

  13. A wave-optics approach to paraxial geometrical laws based on continuity at boundaries

    Science.gov (United States)

    Liñares, J.; Nistal, M. C.

    2011-09-01

    We present a derivation of the paraxial geometrical laws starting from a wave-optics approach, in particular by using simple continuity conditions of paraxial spherical waves at boundaries (discontinuities) between optical media. Paraxial geometrical imaging and magnification laws, under refraction and reflection at boundaries, are derived for several instructive cases and without using Fresnel diffraction theory. The primary aim is to provide a complementary insight into the standard axiomatic approach of paraxial geometrical optics and likewise to allow the introduction of some wave imaging concepts, such as the transmittance function, with a notable didactic interest for advanced subjects such as Fourier optics. This approach provides a more homogeneous vision of classical optics in which the use of the optical field continuity conditions at a boundary is a usual requirement as is clearly seen, for example, in the case of the derivation of Fresnel formulas. The work is particularly intended for university physics teachers and pregraduate and first year postgraduate students.

  14. Image Coding Using Generalized Predictors Based on Sparsity and Geometric Transformations.

    Science.gov (United States)

    Lucas, Luis F R; Rodrigues, Nuno M M; da Silva, Eduardo A B; Pagliari, Carla L; de Faria, Sergio M M

    2016-09-01

    Directional intra prediction plays an important role in current state-of-the-art video coding standards. In directional prediction, neighbouring samples are projected along a specific direction to predict a block of samples. Ultimately, each prediction mode can be regarded as a set of very simple linear predictors, a different one for each pixel of a block. Therefore, a natural question that arises is whether one could use the theory of linear prediction in order to generate intra prediction modes that provide increased coding efficiency. However, such an interpretation of each directional mode as a set of linear predictors is too poor to provide useful insights for their design. In this paper, we introduce an interpretation of directional prediction as a particular case of linear prediction, which uses the first-order linear filters and a set of geometric transformations. This interpretation motivated the proposal of a generalized intra prediction framework, whereby the first-order linear filters are replaced by adaptive linear filters with sparsity constraints. In this context, we investigate the use of efficient sparse linear models, adaptively estimated for each block through the use of different algorithms, such as matching pursuit, least angle regression, least absolute shrinkage and selection operator, or elastic net. The proposed intra prediction framework was implemented and evaluated within the state-of-the-art high efficiency video coding standard. Experiments demonstrated the advantage of this predictive solution, mainly in the presence of images with complex features and textured areas, achieving higher average bitrate savings than other related sparse representation methods proposed in the literature. PMID:27333603

  15. Intraspecific morphological variation of the scorpionfly Dicerapanorpa magna (Chou) (Mecoptera: Panorpidae) based on geometric morphometric analysis of wings

    OpenAIRE

    Liu, M.; Ma, N; Hua, B.-Z.

    2016-01-01

    Wing shape variation was investigated between the sexes and among four populations of the scorpionfly Dicerapanorpa magna (Chou, 1981) endemic to the Qin-Ba Mountains area, China through the landmark-based geometric morphometric approach. The results show that sexual dimorphism exists both in wing size and shape in D. magna. Significant differences exist in female wing size and shape among D. magna populations. The possible reasons of the wing variation are discussed based on the divergence t...

  16. FACILITATING STUDENTSâ GEOMETRIC THINKING THROUGH VAN HIELEâS PHASE-BASED LEARNING USING TANGRAM

    OpenAIRE

    Nyet Moi Siew; Chin Lu Chong; Mohamad Razali Abdullah

    2013-01-01

    The aim of this study was to determine the effects of Van Hiele’s phases of learning using tangrams on 3rd grade primary school students’ levels of geometric thinking at the first (visual) and second (analysis) level. The study further investigated if high, moderate and low ability students acquire better mastery in geometric thinking at the end of tangram activities. Pre-test and post-test single group experimental design was employed in the study. A total of 221 students enrolle...

  17. Geometric constraints derived from the law of conservation of volume and applied to evolutionary models for detachment folding

    Energy Technology Data Exchange (ETDEWEB)

    Dahlstrom, C.D.A. (Chevron Corp., San Francisco, CA (USA))

    1990-03-01

    This paper presents geometric arguments for modifying the conventional concept for the evolution of concentric fold trains above nonductile detachment zones. The common geometric model for concentric folding above a detachment invokes a wave train with fixed fold axes regularly spaced along the fold panel. Limb lengths from crest to trough remain constant as the limb dips increase to uplift the anticlinal crests while the synclinal troughs slide parallel to the detachment plane. The basic depth to detachment calculation, which derives from the Law of Conservation of Volume, requires that the area of uplift above regional for a concentric anticline be equal to the arithmetic product of the shortening and the depth to detachment. This imposes a geometric constraint with which a constant limb length anticline, growing by increasing limb dip above a fixed detachment plane, cannot comply unless, in the early stages, mobile material in the detachment zone flows from the synclinal troughs to the anticlinal crests and then, in the later stages, the flow direction reverses. Relatively few detachment zones contain a significant amount of mobile salt or shale. Therefore, in most concentric detachment fold trains, a basic geometric incompatibility exists between the conventional geometric model and the Law of Conservation of Volume. The conflict can be resolved by an evolutionary fold model wherein the anticlinal fold limbs are short at the inception of folding and grow longer as dips increase and the fold grows. In this model, the anticlinal axes generally are fixed and the synclinal axes active, which has structural and economic implications for the distribution of permeability and syntectonic sediments as well as for the migration and entrapment of hydrocarbons. 18 figs.

  18. Modeling photosynthesis of discontinuous plant canopies by linking the Geometric Optical Radiative Transfer model with biochemical processes

    Science.gov (United States)

    Xin, Q.; Gong, P.; Li, W.

    2015-06-01

    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 timescales. We demonstrate that ambient CO2 concentrations influence daytime vegetation photosynthesis, which needs to be considered in 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.

  19. Geometrical models of left ventricular contraction from MRI of the normal and spontaneously hypertensive rat heart

    International Nuclear Information System (INIS)

    This study develops a quantitative analysis and model for the differences in left ventricular dynamics in normal and spontaneously hypertensive rats, as determined using non-invasive magnetic resonance imaging (MRI). We emerge with a characterization of the geometrical changes in the left ventricle resulting from hypertension. In addition, the techniques we have adopted are potentially applicable to the study of other disease models for important human cardiac pathologies. A gradient-echo multislice imaging sequence (echo time 4.3 ms) achieved complete image coverage of the heart at high time resolution (13 ms) through the cardiac cycle. Cardiac anatomy in two age-matched groups of young adult (8 and 12 weeks old) normal Wistar-Kyoto (WKY, n=8) and spontaneously hypertensive rats (SHR, n=8) was imaged in synchrony with the electrocardiographic R wave in defined planes both parallel and perpendicular to the principal cardiac axis. The transverse left ventricular image sections were circularly symmetrical; this permitted application of different analytical models for the three-dimensional geometry of the epi- and endocardial borders. An ellipsoidal figure of revolution offered an effective description of the three-dimensional left ventricular geometry throughout the cardiac cycle in both normal WKY and SHR animals. The model successfully characterized both the changes in the shape of the left ventricle through the cardiac cycle and the pathological alterations resulting from spontaneous hypertension. The elliptical model also formed the basis of a simple stress distribution analysis. Such parametric descriptions thus provided a useful alternative to more complex finite element analyses of cardiac function. The eccentricity of the ventricle was characterized by an ellipticity factor a, where a=1 for a sphere and a<1 for a prolate ellipsoid. At end systole, the endocardial surface of the left ventricle gave a=0.43±0.02 and 0.49±0.02 for the WKY and SHR animals

  20. Geometrical Optics

    Science.gov (United States)

    Lindlein, Norbert; Leuchs, Gerd

    This chapter shall discuss the basics and the applications of geometrical optical methods in modern optics. Geometrical optics has a long tradition and some ideas are many centuries old. Nevertheless, the invention of modern personal computers which can perform several million floating-point operations in a second also revolutionized the methods of geometrical optics and so several analytical methods lost importance whereas numerical methods such as ray tracing became very important. Therefore, the emphasis in this chapter is also on modern numerical methods such as ray tracing and some other systematic methods such as the paraxial matrix theory.

  1. An improved formalism for quantum computation based on geometric algebra—case study: Grover's search algorithm

    Science.gov (United States)

    Chappell, James M.; Iqbal, Azhar; Lohe, M. A.; von Smekal, Lorenz; Abbott, Derek

    2013-04-01

    The Grover search algorithm is one of the two key algorithms in the field of quantum computing, and hence it is desirable to represent it in the simplest and most intuitive formalism possible. We show firstly, that Clifford's geometric algebra, provides a significantly simpler representation than the conventional bra-ket notation, and secondly, that the basis defined by the states of maximum and minimum weight in the Grover search space, allows a simple visualization of the Grover search analogous to the precession of a spin-{1/2} particle. Using this formalism we efficiently solve the exact search problem, as well as easily representing more general search situations. We do not claim the development of an improved algorithm, but show in a tutorial paper that geometric algebra provides extremely compact and elegant expressions with improved clarity for the Grover search algorithm. Being a key algorithm in quantum computing and one of the most studied, it forms an ideal basis for a tutorial on how to elucidate quantum operations in terms of geometric algebra—this is then of interest in extending the applicability of geometric algebra to more complicated problems in fields of quantum computing, quantum decision theory, and quantum information.

  2. In-line geometric fault detection in car parts based on structured light projection and image processing

    Science.gov (United States)

    Couweleers, Fred; Skotheim, Oystein; Schulerud, Helene; Kaspersen, Kristin

    2003-05-01

    An inspection system is developed to replace manual inspection in a production line for car parts. The system, based on projected structured light, combining Gray code and phase shifting and using B/W CCD cameras and multi-media data projectors, provides robust height measurement images with a high resolution. By carefully observing a number of parameters, it is possible to attain this high resolution in a large measurement volume even with low-cost, off-the-shelf components. We have been able to achieve a noise floor in the phase determination of 30 mrad, which is better than the much reported 1 part in 10,000. The use of 4 cameras, 3 projectors and a turning operation allows total coverage of the complex shape part. A model of normal parts is designed using height measurement images of normal parts. This model represents both expected part dimensions in all camera views as well as normal variations. In order to compare measurements of new parts with the model, an alignment of the images is performed. The deviations between the measured part and the model are analyzed. Deviations outside the normal variation are classified as faults. The system is thus able to find geometrical faults as small as 2x2x0.25 mm in a part that measures roughly 400x400 mm and can decide whether or not to remove a part from the production line. Integrating optical metrology, image processing and robotics, we are able to design a complete system for in-line inspection of car parts with total coverage that is able to keep up with the production cycle time.

  3. A landmark-based method for the geometrical 3D calibration of scanning microscopes

    Energy Technology Data Exchange (ETDEWEB)

    Ritter, M.

    2007-04-27

    This thesis presents a new strategy and a spatial method for the geometric calibration of 3D measurement devices at the micro-range, based on spatial reference structures with nanometersized landmarks (nanomarkers). The new method was successfully applied for the 3D calibration of scanning probe microscopes (SPM) and confocal laser scanning microscopes (CLSM). Moreover, the spatial method was also used for the photogrammetric self-calibration of scanning electron microscopes (SEM). In order to implement the calibration strategy to all scanning microscopes used, the landmark-based principle of reference points often applied at land survey or at close-range applications has been transferred to the nano- and micro-range in the form of nanomarker. In order to function as a support to the nanomarkers, slope-shaped step pyramids have been developed and fabricated by focused ion beam (FIB) induced metal deposition. These FIB produced 3D microstructures have been sized to embrace most of the measurement volume of the scanning microscopes. Additionally, their special design allows the homogenous distribution of the nanomarkers. The nanomarkers were applied onto the support and the plateaus of the slope-step pyramids by FIB etching (milling) as landmarks with as little as several hundreds of nanometers in diameter. The nanomarkers are either of point-, or ring-shaped design. They are optimized so that they can be spatially measured by SPM and CLSM, and, imaged and photogrammetrically analyzed on the basis of SEM data. The centre of the each nanomarker serves as reference point in the measurement data or images. By applying image processing routines, the image (2D) or object (3D) coordinates of each nanomarker has been determined with subpixel accuracy. The correlative analysis of the SPM, CLSM and photogrammetric SEM measurement data after 3D calibration resulted in mean residues in the measured coordinates of as little as 13 nm. Without the coupling factors the mean

  4. Geometric modeling, functional parameter calculation, and visualization of the in-vivo distended rectal wall

    Science.gov (United States)

    Haider, Clifton R.; Manduca, Armando; Camp, Jon J.; Fletcher, Joel G.; Robb, Richard A.; Bharucha, Adil E.

    2006-03-01

    The rectum can distend to accommodate stool, and contracts in response to distention during defecation. Rectal motor dysfunctions are implicated in the pathophysiology of functional defecation disorders and fecal incontinence. These rectal motor functions can be studied by intra-luminal measurements of pressure by manometry, or combined with volume during rectal balloon distention. Pressure-volume (p-v) relationships provide a global index of rectal mechanical properties. However, balloon distention alone does not measure luminal radius or wall thickness, which are necessary to compute wall tension and stress respectively. It has been suggested that the elastic modulus, which is the linear slope of the stress-strain relationship, is a more accurate measure of wall stiffness. Also, measurements of compliance may not reflect differences in rectal diameter between subjects prior to inflation, and imaging is necessary to determine if, as has been suggested, rectal pressure-volume relationships are affected by extra-rectal structures. We have developed a technique to measure rectal stress:strain relationships in humans, by simultaneous magnetic resonance imaging (MRI) during rectal balloon distention. After a conditioning distention, a rectal balloon was distended with water from 0 to 400 ml in 50 ml steps, and imaged at each step with MRI. The fluid filled balloon was segmented from each volume, the phase-ordered binary volumes were transformed into a geometric characterization of the inflated rectal surface. Taken together with measurements of balloon pressure and of rectal wall thickness, this model of the rectal surface was used to calculate regional values of curvature, tension, strain, and stress for the rectum. In summary, this technique has the unique ability to non-invasively measure the rectal stress:strain relationship and also determine if rectal expansion is limited by extra-rectal structures. This functional information allows the direct clinical analysis

  5. GEOMETRIC TURBULENCE

    Directory of Open Access Journals (Sweden)

    Trunev A. P.

    2014-05-01

    Full Text Available In this article we have investigated the solutions of Maxwell's equations, Navier-Stokes equations and the Schrödinger associated with the solutions of Einstein's equations for empty space. It is shown that in some cases the geometric instability leading to turbulence on the mechanism of alternating viscosity, which offered by N.N. Yanenko. The mechanism of generation of matter from dark energy due to the geometric turbulence in the Big Bang has been discussed

  6. Modeling photosynthesis of discontinuous plant canopies by linking Geometric Optical Radiative Transfer model with biochemical processes

    OpenAIRE

    Xin, Q; P. Gong; Li, W.

    2015-01-01

    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 a...

  7. Horizontal geometrical reaction time model for two-beam nacelle LiDARs

    Science.gov (United States)

    Beuth, Thorsten; Fox, Maik; Stork, Wilhelm

    2015-06-01

    Wind energy is one of the leading sustainable energies. To attract further private and state investment in this technology, a broad scaled drop of the cost of energy has to be enforced. There is a trend towards using Laser Doppler Velocimetry LiDAR systems for enhancing power output and minimizing downtimes, fatigue and extreme forces. Since most used LiDARs are horizontally setup on a nacelle and work with two beams, it is important to understand the geometrical configuration which is crucial to estimate reaction times for the actuators to compensate wind gusts. In the beginning of this article, the basic operating modes of wind turbines are explained and the literature on wind behavior is analyzed to derive specific wind speed and wind angle conditions in relation to the yaw angle of the hub. A short introduction to the requirements for the reconstruction of the wind vector length and wind angle leads to the problem of wind shear detection of angled but horizontal homogeneous wind fronts due to the spatial separation of the measuring points. A distance is defined in which the wind shear of such homogeneous wind fronts is not present which is used as a base to estimate further distance calculations. The reaction time of the controller and the actuators are having a negative effect on the effective overall reaction time for wind regulation as well. In the end, exemplary calculations estimate benefits and disadvantages of system parameters for wind gust regulating LiDARs for a wind turbine of typical size. An outlook shows possible future improvements concerning the vertical wind behavior.

  8. Unconventional Geometric Phase-Shift Gates Based on Superconducting Quantum Interference Devices Coupled to a Single-Mode Cavity

    Institute of Scientific and Technical Information of China (English)

    SONG Ke-Hui; ZHOU Zheng-Wei; GUO Guang-Can

    2006-01-01

    We present a scheme to realize geometric phase-shift gate for two superconducting quantum interference device (SQUID) qubits coupled to a single-mode microwave field. The geometric phase-shift gate operation is performed transitions during the gate operation. Thus, the docoherence due to energy spontaneous emission based on the levels of SQUIDs are suppressed. The gate is insensitive to the cavity decay throughout the operation since the cavity mode is displaced along a circle in the phase space, acquiring a phase conditional upon the two lower flux states of the SQUID qubits, and the cavity mode is still in the original vacuum state. Based on the SQUID qubits interacting with the cavity mode, our proposed approach may open promising prospects for quantum logic in SQUID-system.

  9. Sensitivity of aerosol retrieval to geometrical configuration of ground-based sun/sky-radiometer observations

    Directory of Open Access Journals (Sweden)

    B. Torres

    2013-03-01

    Full Text Available A sensitivity study of the aerosol optical properties retrieval to the geometrical configuration of the ground-based sky radiometer observations is carried out through the inversion tests. Specifically, the study is focused on the principal plane and almucantar observation, since these geometries are employed in Aeronet (AErosol RObotic NETwork. The following effects has been analyzed with simulated data for both geometries: sensitivity of the retrieval to variability of the observed scattering angle range, uncertainties in the assumptions of the aerosol vertical distribution and surface reflectance, possible instrument pointing errors and the effects of the finite field of view. The synthetic observations of radiometer in the tests were calculated using a previous climatology data of retrieved aerosol over three Aeronet sites: Mongu (Zambia for biomass burning aerosol, Goddard Space Flight Center (Maryland-USA for urban aerosol and Solar Village (Saudi Arabia for desert dust aerosol. The results show that almucantar retrievals, in general, are more reliable than principal plane retrievals in presence of the analyzed error sources. This fact partially can be explained by to practical advantages of almucantar geometry: the symmetry between its left and right branches that helps to eliminate some observational uncertainties and the constant value of optical mass constant during the measurements that makes almucantar observations nearly independent on vertical variability of aerosol. Nevertheless, almucantar retrievals present instabilities at high sun observations due to the reduction of the scattering angle range coverage resulting in decrease of information content. The last part of the study is devoted to identification of possible differences between the aerosol retrieval results obtained from real Aeronet data using both geometries. In particular, we have compared Aeronet retrievals at three different key sites: Mongu (biomass burning

  10. Geometric moment based nonlocal-means filter for ultrasound image denoising

    Science.gov (United States)

    Dou, Yangchao; Zhang, Xuming; Ding, Mingyue; Chen, Yimin

    2011-06-01

    It is inevitable that there is speckle noise in ultrasound image. Despeckling is the important process. The original nonlocal means (NLM) filter can remove speckle noise and protect the texture information effectively when the image corruption degree is relatively low. But when the noise in the image is strong, NLM will produce fictitious texture information, which has the disadvantageous influence on its denoising performance. In this paper, a novel nonlocal means (NLM) filter is proposed. We introduce geometric moments into the NLM filter. Though geometric moments are not orthogonal moments, it is popular by its concision, and its restoration ability is not yet proved. Results on synthetic data and real ultrasound image show that the proposed method can get better despeckling performance than other state-of-the-art method.

  11. A mathematical formulation for interface-based modular product design with geometric and weight constraints

    Science.gov (United States)

    Jung-Woon Yoo, John

    2016-06-01

    Since customer preferences change rapidly, there is a need for design processes with shorter product development cycles. Modularization plays a key role in achieving mass customization, which is crucial in today's competitive global market environments. Standardized interfaces among modularized parts have facilitated computational product design. To incorporate product size and weight constraints during computational design procedures, a mixed integer programming formulation is presented in this article. Product size and weight are two of the most important design parameters, as evidenced by recent smart-phone products. This article focuses on the integration of geometric, weight and interface constraints into the proposed mathematical formulation. The formulation generates the optimal selection of components for a target product, which satisfies geometric, weight and interface constraints. The formulation is verified through a case study and experiments are performed to demonstrate the performance of the formulation.

  12. A New Training Method for Feedforward Neural Networks Based on Geometric Contraction Property of Activation Functions

    OpenAIRE

    Birtea, Petre; Cernazanu-Glavan, Cosmin; Sisu, Alexandru

    2016-01-01

    We propose a new training method for a feedforward neural network having the activation functions with the geometric contraction property. The method consists of constructing a new functional that is less nonlinear in comparison with the classical functional by removing the nonlinearity of the activation functions from the output layer. We validate this new method by a series of experiments that show an improved learning speed and also a better classification error.

  13. Cryptography-Based Chaos via Geometric Undersampling of Ring-Coupled Attractors

    OpenAIRE

    Lozi, René

    2015-01-01

    17 pages, 19 figures International audience We propose a new mechanism for undersampling chaotic numbers obtained by the ringcoupling of one-dimensional maps. In the case of 2 coupled maps this mechanism allows thebuilding of a PRNG which passes all NIST Test.This new geometric undersampling is very effective for generating 2 parallel streams of pseudorandomnumbers, as we show, computing carefully their properties, up to sequences of 10^12consecutives iterates of the ring coupled mappin...

  14. Mass spectrometry based identification of geometric isomers during metabolic stability study of a new cytotoxic sulfonamide derivatives supported by quantitative structure-retention relationships.

    Science.gov (United States)

    Belka, Mariusz; Hewelt-Belka, Weronika; Sławiński, Jarosław; Bączek, Tomasz

    2014-01-01

    A set of 15 new sulphonamide derivatives, presenting antitumor activity have been subjected to a metabolic stability study. The results showed that besides products of biotransformation, some additional peaks occurred in chromatograms. Tandem mass spectrometry revealed the same mass and fragmentation pathway, suggesting that geometric isomerization occurred. Thus, to support this hypothesis, quantitative structure-retention relationships were applied. Human liver microsomes were used as an in vitro model of metabolism. The biotransformation reactions were tracked by liquid chromatography assay and additionally, fragmentation mass spectra were recorded. In silico molecular modeling at a semi-empirical level was conducted as a starting point for molecular descriptor calculations. A quantitative structure-retention relationship model was built applying multiple linear regression based on selected three-dimensional descriptors. The studied compounds revealed high metabolic stability, with a tendency to form hydroxylated biotransformation products. However, significant chemical instability in conditions simulating human body fluids was noticed. According to literature and MS data geometrical isomerization was suggested. The developed in sillico model was able to describe the relationship between the geometry of isomer pairs and their chromatographic retention properties, thus it supported the hypothesis that the observed pairs of peaks are most likely geometric isomers. However, extensive structural investigations are needed to fully identify isomers' geometry. An effort to describe MS fragmentation pathways of novel chemical structures is often not enough to propose structures of potent metabolites and products of other chemical reactions that can be observed in compound solutions at early drug discovery studies. The results indicate that the relatively non-expensive and not time- and labor-consuming in sillico approach could be a good supportive tool assisting the

  15. Multivariate Statistical Analysis: A Geometric Perspective

    OpenAIRE

    Tyurin, Yuri N.

    2009-01-01

    A new, coordinate-free (geometric) approach to multivariate statistical analysis. General multivariate linear models and linear hypotheses are defined in geometric form. A method of constructing statistical criteria is defined for linear hypotheses. As a result, multivariate statistical analysis is developed in full analogy to classical statistical analysis. This approach is based on tensor products and modules over the ring of square matrices, supplied with an inner product.

  16. Hopc: a Novel Similarity Metric Based on Geometric Structural Properties for Multi-Modal Remote Sensing Image Matching

    Science.gov (United States)

    Ye, Yuanxin; Shen, Li

    2016-06-01

    Automatic matching of multi-modal remote sensing images (e.g., optical, LiDAR, SAR and maps) remains a challenging task in remote sensing image analysis due to significant non-linear radiometric differences between these images. This paper addresses this problem and proposes a novel similarity metric for multi-modal matching using geometric structural properties of images. We first extend the phase congruency model with illumination and contrast invariance, and then use the extended model to build a dense descriptor called the Histogram of Orientated Phase Congruency (HOPC) that captures geometric structure or shape features of images. Finally, HOPC is integrated as the similarity metric to detect tie-points between images by designing a fast template matching scheme. This novel metric aims to represent geometric structural similarities between multi-modal remote sensing datasets and is robust against significant non-linear radiometric changes. HOPC has been evaluated with a variety of multi-modal images including optical, LiDAR, SAR and map data. Experimental results show its superiority to the recent state-of-the-art similarity metrics (e.g., NCC, MI, etc.), and demonstrate its improved matching performance.

  17. DETERMINATION ALGORITHM OF OPTIMAL GEOMETRICAL PARAMETERS FOR COMPONENTS OF FREIGHT CARS ON THE BASIS OF GENERALIZED MATHEMATICAL MODELS

    Directory of Open Access Journals (Sweden)

    O. V. Fomin

    2013-10-01

    Full Text Available Purpose. Presentation of features and example of the use of the offered determination algorithm of optimum geometrical parameters for the components of freight cars on the basis of the generalized mathematical models, which is realized using computer. Methodology. The developed approach to search for optimal geometrical parameters can be described as the determination of optimal decision of the selected set of possible variants. Findings. The presented application example of the offered algorithm proved its operation capacity and efficiency of use. Originality. The determination procedure of optimal geometrical parameters for freight car components on the basis of the generalized mathematical models was formalized in the paper. Practical value. Practical introduction of the research results for universal open cars allows one to reduce container of their design and accordingly to increase the carrying capacity almost by100 kg with the improvement of strength characteristics. Taking into account the mass of their park this will provide a considerable economic effect when producing and operating. The offered approach is oriented to the distribution of the software packages (for example Microsoft Excel, which are used by technical services of the most enterprises, and does not require additional capital investments (acquisitions of the specialized programs and proper technical staff training. This proves the correctness of the research direction. The offered algorithm can be used for the solution of other optimization tasks on the basis of the generalized mathematical models.

  18. Improving Semantic Updating Method on 3d City Models Using Hybrid Semantic-Geometric 3d Segmentation Technique

    Science.gov (United States)

    Sharkawi, K.-H.; Abdul-Rahman, A.

    2013-09-01

    to LoD4. The accuracy and structural complexity of the 3D objects increases with the LoD level where LoD0 is the simplest LoD (2.5D; Digital Terrain Model (DTM) + building or roof print) while LoD4 is the most complex LoD (architectural details with interior structures). Semantic information is one of the main components in CityGML and 3D City Models, and provides important information for any analyses. However, more often than not, the semantic information is not available for the 3D city model due to the unstandardized modelling process. One of the examples is where a building is normally generated as one object (without specific feature layers such as Roof, Ground floor, Level 1, Level 2, Block A, Block B, etc). This research attempts to develop a method to improve the semantic data updating process by segmenting the 3D building into simpler parts which will make it easier for the users to select and update the semantic information. The methodology is implemented for 3D buildings in LoD2 where the buildings are generated without architectural details but with distinct roof structures. This paper also introduces hybrid semantic-geometric 3D segmentation method that deals with hierarchical segmentation of a 3D building based on its semantic value and surface characteristics, fitted by one of the predefined primitives. For future work, the segmentation method will be implemented as part of the change detection module that can detect any changes on the 3D buildings, store and retrieve semantic information of the changed structure, automatically updates the 3D models and visualize the results in a userfriendly graphical user interface (GUI).

  19. Rotational Sweepback of Magnetic Field Lines in Geometrical Models of Pulsar Radio Emission

    Science.gov (United States)

    Dyks, J.; Harding, Alice K.

    2004-01-01

    We study the rotational distortions of the vacuum dipole magnetic field in the context of geometrical models of the radio emission from pulsars. We find that at low altitudes the rotation deflects the local direction of the magnetic field by at most an angle of the order of r(sup 2 sub n), where r(sub n) = r/R(sub lc), r is the radial distance and R(sub lc) is the light cylinder radius. To the lowest (i.e. second) order in r(sub n) this distortion is symmetrical with respect to the plane containing the dipole axis and the rotation axis ((Omega, mu) plane). The lowest order distortion which is asymmetrical with respect to the (Omega, mu) plane is third order in r(sub n). These results confirm the common assumption that the rotational sweepback has negligible effect on the position angle (PA) curve. We show, however, that the influence of the sweep back on the outer boundary of the open field line region (open volume) is a much larger effect, of the order of r(sup 1/2 sub n). The open volume is shifted backwards with respect to the rotation direction by an angle delta(sub o nu) approx. 0.2 sin alpha r(sup 1/2 sub n) where alpha is the dipole inclination with respect to the rotation axis. The associated phase shift of the pulse profile Delta phi(sub o nu) approx. 0.2 r(sup 1/2 sub n) can easily exceed the shift due to combined effects of aberration and propagation time delays (approx. 2r(sub n)). This strongly affects the misalignment of the center of the PA curve and the center of the pulse profile, thereby modifying the delay radius relation. Contrary to intuition, the effect of sweepback dominates over other effects when emission occurs at low altitudes. For r(sub n) < or approx. 3 x 10(exp -3) the shift becomes negative, i.e. the center of the position angle curve precedes the profile center. With the sweepback effect included, the modified delay-radius relation predicts larger emission radii and is in much better agreement with the other methods of determining r

  20. Quantum-classical hybrids in a simplified model of QED and geometric phase induced by charged particle trajectory

    CERN Document Server

    Koide, T

    2016-01-01

    We derive a model of quantum-classical hybrids for a simplified model of quantum electrodynamics in the framework of the stochastic variational method. In this model, charged particle trajectories are affected by the interaction with quantized electromagnetic fields, and this quantum-classical interaction induces a displacement current. We further investigate a geometric phase in the wave functional of the gauge field configuration, which is induced by adiabatic motions of the charged particles. This phase contains the quantum-classical backreaction effect and usual Berry's phase is reproduced in the vanishing limit of the fluctuation of the charged particle trajectories.

  1. Helicopter Rotor Load Prediction Using a Geometrically Exact Beam with Multicomponent Model

    DEFF Research Database (Denmark)

    Lee, Hyun-Ku; Viswamurthy, S.R.; Park, Sang Chul; Kim, Taeseong; Shin, Sang Joon; Kim, Deog-Kwan

    2010-01-01

    In this paper, an accurate structural dynamic analysis was developed for a helicopter rotor system including rotor control components, which was coupled to various aerodynamic and wake models in order to predict an aeroelastic response and the loads acting on the rotor. Its blade analysis was based......CAMRADII. The present analysis features both model compactness and robustness in its solution procedure while capturing the sophisticated behavior of individual rotor components. The analysis is expected to be part of a framework useful in the preliminary design phase for helicopters....... on an intrinsic formulation of moving beams implemented in the time domain. The rotor control system was modeled as a combination of rigid and elastic components. A multicomponent analysis was then developed by coupling the beam finite element model with the rotor control system model to obtain a...

  2. Model of counterparty risk with geometric attenuation and valuation of CDS

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    To investigate the impact of microstructure interdependency of a counterparty explicitly, a geometric function is introduced in one firm's default intensity to reflect the attenuation behavior of the impact of its counterparty firm's default. The general joint distribution and marginal distributions of default times are derived by employing the change of measure. The fair premium of a vanilla CDS (credit default swap) is obtained in continuous and discrete contexts, respectively. The swap premium in a discr...

  3. Fresnel Lens Solar Concentrator Design Based on Geometric Optics and Blackbody Radiation Equations

    Science.gov (United States)

    Watson, Michael D.; Jayroe, Robert, Jr.

    1999-01-01

    Fresnel lenses have been used for years as solar concentrators in a variety of applications. Several variables effect the final design of these lenses including: lens diameter, image spot distance from the lens, and bandwidth focused in the image spot. Defining the image spot as the geometrical optics circle of least confusion and applying blackbody radiation equations the spot energy distribution can be determined. These equations are used to design a fresnel lens to produce maximum flux for a given spot size, lens diameter, and image distance. This approach results in significant increases in solar efficiency over traditional single wavelength designs.

  4. A Study of the Anechoic Performance of Rice Husk-Based, Geometrically Tapered, Hollow Absorbers

    OpenAIRE

    Muhammad Nadeem Iqbal; Mohd. Fareq Malek; Yeng Seng Lee; Liyana Zahid; Muhammad Shafiq Mezan

    2014-01-01

    Although solid, geometrically tapered microwave absorbers are preferred due to their better performance, they are bulky and must have a thickness on the order of λ or more. The goal of this study was to design lightweight absorbers that can reduce the electromagnetic reflections to less than −10 dB. We used a very simple approach; two waste materials, that is, rice husks and tire dust in powder form, were used to fabricate two independent samples. We measured and used their dielectric propert...

  5. Quantum computation using geometric algebra

    Science.gov (United States)

    Matzke, Douglas James

    This dissertation reports that arbitrary Boolean logic equations and operators can be represented in geometric algebra as linear equations composed entirely of orthonormal vectors using only addition and multiplication Geometric algebra is a topologically based algebraic system that naturally incorporates the inner and anticommutative outer products into a real valued geometric product, yet does not rely on complex numbers or matrices. A series of custom tools was designed and built to simplify geometric algebra expressions into a standard sum of products form, and automate the anticommutative geometric product and operations. Using this infrastructure, quantum bits (qubits), quantum registers and EPR-bits (ebits) are expressed symmetrically as geometric algebra expressions. Many known quantum computing gates, measurement operators, and especially the Bell/magic operators are also expressed as geometric products. These results demonstrate that geometric algebra can naturally and faithfully represent the central concepts, objects, and operators necessary for quantum computing, and can facilitate the design and construction of quantum computing tools.

  6. Traffic sign detection in MLS acquired point clouds for geometric and image-based semantic inventory

    Science.gov (United States)

    Soilán, Mario; Riveiro, Belén; Martínez-Sánchez, Joaquín; Arias, Pedro

    2016-04-01

    Nowadays, mobile laser scanning has become a valid technology for infrastructure inspection. This technology permits collecting accurate 3D point clouds of urban and road environments and the geometric and semantic analysis of data became an active research topic in the last years. This paper focuses on the detection of vertical traffic signs in 3D point clouds acquired by a LYNX Mobile Mapper system, comprised of laser scanning and RGB cameras. Each traffic sign is automatically detected in the LiDAR point cloud, and its main geometric parameters can be automatically extracted, therefore aiding the inventory process. Furthermore, the 3D position of traffic signs are reprojected on the 2D images, which are spatially and temporally synced with the point cloud. Image analysis allows for recognizing the traffic sign semantics using machine learning approaches. The presented method was tested in road and urban scenarios in Galicia (Spain). The recall results for traffic sign detection are close to 98%, and existing false positives can be easily filtered after point cloud projection. Finally, the lack of a large, publicly available Spanish traffic sign database is pointed out.

  7. Dosimetric impact of geometric errors due to respiratory motion prediction on dynamic multileaf collimator-based four-dimensional radiation delivery

    International Nuclear Information System (INIS)

    The synchronization of dynamic multileaf collimator (DMLC) response with respiratory motion is critical to ensure the accuracy of DMLC-based four dimensional (4D) radiation delivery. In practice, however, a finite time delay (response time) between the acquisition of tumor position and multileaf collimator response necessitates predictive models of respiratory tumor motion to synchronize radiation delivery. Predicting a complex process such as respiratory motion introduces geometric errors, which have been reported in several publications. However, the dosimetric effect of such errors on 4D radiation delivery has not yet been investigated. Thus, our aim in this work was to quantify the dosimetric effects of geometric error due to prediction under several different conditions. Conformal and intensity modulated radiation therapy (IMRT) plans for a lung patient were generated for anterior-posterior/posterior-anterior (AP/PA) beam arrangements at 6 and 18 MV energies to provide planned dose distributions. Respiratory motion data was obtained from 60 diaphragm-motion fluoroscopy recordings from five patients. A linear adaptive filter was employed to predict the tumor position. The geometric error of prediction was defined as the absolute difference between predicted and actual positions at each diaphragm position. Distributions of geometric error of prediction were obtained for all of the respiratory motion data. Planned dose distributions were then convolved with distributions for the geometric error of prediction to obtain convolved dose distributions. The dosimetric effect of such geometric errors was determined as a function of several variables: response time (0-0.6 s), beam energy (6/18 MV), treatment delivery (3D/4D), treatment type (conformal/IMRT), beam direction (AP/PA), and breathing training type (free breathing/audio instruction/visual feedback). Dose difference and distance-to-agreement analysis was employed to quantify results. Based on our data, the

  8. Influence of muscle-tendon complex geometrical parameters on modeling passive stretch behavior with the Discrete Element Method.

    Science.gov (United States)

    Roux, A; Laporte, S; Lecompte, J; Gras, L-L; Iordanoff, I

    2016-01-25

    The muscle-tendon complex (MTC) is a multi-scale, anisotropic, non-homogeneous structure. It is composed of fascicles, gathered together in a conjunctive aponeurosis. Fibers are oriented into the MTC with a pennation angle. Many MTC models use the Finite Element Method (FEM) to simulate the behavior of the MTC as a hyper-viscoelastic material. The Discrete Element Method (DEM) could be adapted to model fibrous materials, such as the MTC. DEM could capture the complex behavior of a material with a simple discretization scheme and help in understanding the influence of the orientation of fibers on the MTC׳s behavior. The aims of this study were to model the MTC in DEM at the macroscopic scale and to obtain the force/displacement curve during a non-destructive passive tensile test. Another aim was to highlight the influence of the geometrical parameters of the MTC on the global mechanical behavior. A geometrical construction of the MTC was done using discrete element linked by springs. Young׳s modulus values of the MTC׳s components were retrieved from the literature to model the microscopic stiffness of each spring. Alignment and re-orientation of all of the muscle׳s fibers with the tensile axis were observed numerically. The hyper-elastic behavior of the MTC was pointed out. The structure׳s effects, added to the geometrical parameters, highlight the MTC׳s mechanical behavior. It is also highlighted by the heterogeneity of the strain of the MTC׳s components. DEM seems to be a promising method to model the hyper-elastic macroscopic behavior of the MTC with simple elastic microscopic elements. PMID:26708963

  9. Time Stretching of the GeV Emission of GRBs: Fermi-LAT Data versus Geometrical Model

    Science.gov (United States)

    Piskunov, Maxim S.; Rubtsov, Grigory I.

    2016-06-01

    It is known that the high-energy (\\gt 100 {MeV}) emission of gamma-ray bursts is delayed with respect to the low-energy emission. However, the dependence of light curves on energy has not been studied for the high-energy bands. In this paper, we consider the bursts observed by Fermi LAT from 2008 August 4 to 2011 August 1, for which at least 10 photons were observed with energy greater than 1 {GeV}. These include four bursts: GRB 080916C, GRB 090510, GRB 090902B, and GRB 090926A. We use the Kolmogorov–Smirnov test to compare the light curves in the two bands 100 {MeV}\\lt E\\lt 1 {GeV} and E\\gt 1 {GeV}. For GRB 080916C and GRB 090510 the light curves in the two bands are statistically compatible. However, for GRB 090926A, the higher-energy light curve is stretched compared to the lower-energy one with a statistical significance of 3.3σ and, for GRB 090902B, on the contrary, the lower-energy curve is stretched with 2.3σ significance. We argue that the observed diversity of stretching factors may be explained using a simple geometrical model. The model assumes that the jet opening angle depends on the emission energy in a way that the most energetic photons are radiated near the axis of the jet. All of the bursts are considered equivalent in their rest frames, and the observed light curves differ only due to different redshifts and view directions. The model conforms to the total burst energy constraint and matches the Fermi-LAT observations of the fraction of GRBs visible in the 100 {MeV}\\lt E\\lt 1 {GeV} band, which may be observed at higher energies. The model predicts the distribution of observable stretching factors, which may be tested in future data. Finally, we propose a method to estimate the observer's off-axis angle based on the stretching factor and the fraction of the high-energy photons. The code for modeling is open source and is publicly available on GitHub (https://github.com/maxitg/GammaRays).

  10. Geometrical and statistical properties of vision models obtained via maximum differentiation

    Science.gov (United States)

    Malo, Jesús; Simoncelli, Eero P.

    2015-03-01

    We examine properties of perceptual image distortion models, computed as the mean squared error in the response of a 2-stage cascaded image transformation. Each stage in the cascade is composed of a linear transformation, followed by a local nonlinear normalization operation. We consider two such models. For the first, the structure of the linear transformations is chosen according to perceptual criteria: a center-surround filter that extracts local contrast, and a filter designed to select visually relevant contrast according to the Standard Spatial Observer. For the second, the linear transformations are chosen based on statistical criterion, so as to eliminate correlations estimated from responses to a set of natural images. For both models, the parameters that govern the scale of the linear filters and the properties of the nonlinear normalization operation, are chosen to achieve minimal/maximal subjective discriminability of pairs of images that have been optimized to minimize/maximize the model, respectively (we refer to this as MAximum Differentiation, or "MAD", Optimization). We find that both representations substantially reduce redundancy (mutual information), with a larger reduction occurring in the second (statistically optimized) model. We also find that both models are highly correlated with subjective scores from the TID2008 database, with slightly better performance seen in the first (perceptually chosen) model. Finally, we use a foveated version of the perceptual model to synthesize visual metamers. Specifically, we generate an example of a distorted image that is optimized so as to minimize the perceptual error over receptive fields that scale with eccentricity, demonstrating that the errors are barely visible despite a substantial MSE relative to the original image.

  11. Addressing geometric non-linearities with cantilever MEMS: beyond the Duffing model

    OpenAIRE

    Collin, Eddy; Bunkov, Yuriy M.; Godfrin, Henri

    2010-01-01

    International audience We report on low temperature measurements performed on micro-electro-mechanical systems (MEMS) driven deeply into the non-linear regime. The materials are kept in their elastic domain, while the observed non-linearity is purely of geometrical origin. Two techniques are used, harmonic drive and free decay. For each case, we present an analytic theory fitting the data. The harmonic drive is fit with a Lorentz-like lineshape obtained from an extended version of Landau and...

  12. Automatic geometric modeling, mesh generation and FE analysis for pipelines with idealized defects and arbitrary location

    Energy Technology Data Exchange (ETDEWEB)

    Motta, R.S.; Afonso, S.M.B.; Willmersdorf, R.B.; Lyra, P.R.M. [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil); Cabral, H.L.D. [TRANSPETRO, Rio de Janeiro, RJ (Brazil); Andrade, E.Q. [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil)

    2009-07-01

    Although the Finite Element Method (FEM) has proved to be a powerful tool to predict the failure pressure of corroded pipes, the generation of good computational models of pipes with corrosion defects can take several days. This makes the use of computational simulation procedure difficult to apply in practice. The main purpose of this work is to develop a set of computational tools to produce automatically models of pipes with defects, ready to be analyzed with commercial FEM programs, starting from a few parameters that locate and provide the main dimensions of the defect or a series of defects. Here these defects can be internal and external and also assume general spatial locations along the pipe. Idealized rectangular and elliptic geometries can be generated. These tools were based on MSC.PATRAN pre and post-processing programs and were written with PCL (Patran Command Language). The program for the automatic generation of models (PIPEFLAW) has a simplified and customized graphical interface, so that an engineer with basic notions of computational simulation with the FEM can generate rapidly models that result in precise and reliable simulations. Some examples of models of pipes with defects generated by the PIPEFLAW system are shown, and the results of numerical analyses, done with the tools presented in this work, are compared with, empiric results. (author)

  13. QM/MM Simulation of the Hydrogen Bond Dynamics of an Adenine:Uracil Base Pair in Solution. Geometric Correlations and Infrared Spectrum

    CERN Document Server

    Yan, Yun-an

    2009-01-01

    Hybrid QM(DFT)/MM molecular dynamics simulations have been carried out for the Watson-Crick base pair of 9-ethyl-8-phenyladenine and 1-cyclohexyluracil in deuterochloroform solution at room temperature. Trajectories are analyzed putting special attention to the geometric correlations of the $\\NHN$ and $\\NHO$ hydrogen bonds in the base pair. Further, based on empirical correlations between the hydrogen bond bond length and the fundamental NH stretching frequency its fluctuations are obtained along the trajectory. Using the time dependent frequencies the infrared lineshape is determined assuming the validity of a second order cumulant expansion. The deviations for the fundamental transition frequencies are calculated to amount to less than 2% as compared with experiment. The width of the spectrum for the $\\NHN$ bond is in reasonable agreement with experiment while that for the $\\NHO$ case is underestimated by the present model. Comparing the performance of different pseudopotentials it is found that the Troulli...

  14. Evaluation of the geometric accuracy of surrogate-based gated VMAT using intrafraction kilovoltage x-ray images

    International Nuclear Information System (INIS)

    Purpose: To evaluate the geometric accuracy of beam targeting in external surrogate-based gated volumetric modulated arc therapy (VMAT) using kilovoltage (kV) x-ray images acquired during dose delivery. Methods: Gated VMAT treatments were delivered using a Varian TrueBeam STx Linac for both physical phantoms and patients. Multiple gold fiducial markers were implanted near the target. The reference position was created for each implanted marker, representing its correct position at the gating threshold. The gating signal was generated from the RPM system. During the treatment, kV images were acquired immediately before MV beam-on at every breathing cycle, using the on-board imaging system. All implanted markers were detected and their 3D positions were estimated using in-house developed software. The positioning error of a marker is defined as the distance of the marker from its reference position for each frame of the images. The overall error of the system is defined as the average over all markers. For the phantom study, both sinusoidal motion (1D and 3D) and real human respiratory motion was simulated for the target and surrogate. In the baseline case, the two motions were synchronized for the first treatment fraction. To assess the effects of surrogate-target correlation on the geometric accuracy, a phase shift of 5% and 10% between the two motions was introduced. For the patient study, intrafraction kV images of five stereotactic body radiotherapy (SBRT) patients were acquired for one or two fractions. Results: For the phantom study, a high geometric accuracy was achieved in the baseline case (average error: 0.8 mm in the superior-inferior or SI direction). However, the treatment delivery is prone to geometric errors if changes in the target-surrogate relation occur during the treatment: the average error was increased to 2.3 and 4.7 mm for the phase shift of 5% and 10%, respectively. Results obtained with real human respiratory curves show a similar trend

  15. a Semi-Rigorous Sensor Model for Precision Geometric Processing of Mini-Rf Bistatic Radar Images of the Moon

    Science.gov (United States)

    Kirk, R. L.; Barrett, J. M.; Wahl, D. E.; Erteza, I.; Jackowatz, C. V.; Yocky, D. A.; Turner, S.; Bussey, D. B. J.; Paterson, G. W.

    2016-06-01

    The spaceborne synthetic aperture radar (SAR) instruments known as Mini-RF were designed to image shadowed areas of the lunar poles and assay the presence of ice deposits by quantitative polarimetry. We have developed radargrammetric processing techniques to enhance the value of these observations by removing spacecraft ephemeris errors and distortions caused by topographic parallax so the polarimetry can be compared with other data sets. Here we report on the extension of this capability from monostatic imaging (signal transmitted and received on the same spacecraft) to bistatic (transmission from Earth and reception on the spacecraft) which provides a unique opportunity to measure radar scattering at nonzero phase angles. In either case our radargrammetric sensor models first reconstruct the observed range and Doppler frequency from recorded image coordinates, then determine the ground location with a corrected trajectory on a more detailed topographic surface. The essential difference for bistatic radar is that range and Doppler shift depend on the transmitter as well as receiver trajectory. Incidental differences include the preparation of the images in a different (map projected) coordinate system and use of "squint" (i.e., imaging at nonzero rather than zero Doppler shift) to achieve the desired phase angle. Our approach to the problem is to reconstruct the time-of-observation, range, and Doppler shift of the image pixel by pixel in terms of rigorous geometric optics, then fit these functions with low-order polynomials accurate to a small fraction of a pixel. Range and Doppler estimated by using these polynomials can then be georeferenced rigorously on a new surface with an updated trajectory. This "semi-rigorous" approach (based on rigorous physics but involving fitting functions) speeds the calculation and avoids the need to manage both the original and adjusted trajectory data. We demonstrate the improvement in registration of the bistatic images for

  16. A Geometrically-Constrained Mathematical Model of Mammary Gland Ductal Elongation Reveals Novel Cellular Dynamics within the Terminal End Bud.

    Directory of Open Access Journals (Sweden)

    Ingrid Paine

    2016-04-01

    Full Text Available Mathematics is often used to model biological systems. In mammary gland development, mathematical modeling has been limited to acinar and branching morphogenesis and breast cancer, without reference to normal duct formation. We present a model of ductal elongation that exploits the geometrically-constrained shape of the terminal end bud (TEB, the growing tip of the duct, and incorporates morphometrics, region-specific proliferation and apoptosis rates. Iterative model refinement and behavior analysis, compared with biological data, indicated that the traditional metric of nipple to the ductal front distance, or percent fat pad filled to evaluate ductal elongation rate can be misleading, as it disregards branching events that can reduce its magnitude. Further, model driven investigations of the fates of specific TEB cell types confirmed migration of cap cells into the body cell layer, but showed their subsequent preferential elimination by apoptosis, thus minimizing their contribution to the luminal lineage and the mature duct.

  17. A Geometrically-Constrained Mathematical Model of Mammary Gland Ductal Elongation Reveals Novel Cellular Dynamics within the Terminal End Bud

    Science.gov (United States)

    Chauviere, Arnaud; Landua, John; Sreekumar, Amulya; Cristini, Vittorio; Rosen, Jeffrey; Lewis, Michael T.

    2016-01-01

    Mathematics is often used to model biological systems. In mammary gland development, mathematical modeling has been limited to acinar and branching morphogenesis and breast cancer, without reference to normal duct formation. We present a model of ductal elongation that exploits the geometrically-constrained shape of the terminal end bud (TEB), the growing tip of the duct, and incorporates morphometrics, region-specific proliferation and apoptosis rates. Iterative model refinement and behavior analysis, compared with biological data, indicated that the traditional metric of nipple to the ductal front distance, or percent fat pad filled to evaluate ductal elongation rate can be misleading, as it disregards branching events that can reduce its magnitude. Further, model driven investigations of the fates of specific TEB cell types confirmed migration of cap cells into the body cell layer, but showed their subsequent preferential elimination by apoptosis, thus minimizing their contribution to the luminal lineage and the mature duct. PMID:27115287

  18. Lower Bounds for Sorted Geometric Queries in the I/O Model

    DEFF Research Database (Denmark)

    Afshani, Peyman; Zeh, Norbert

    2012-01-01

    be optimal and in fact we can show that, for a particular class of “persistence-based” data structures, the space lower bound can be improved to Ω(N2 / MO(1)). Both these lower bounds are a first step towards understanding the complexity of sorted geometric query problems. All our lower bounds assume......We study sorted geometric query problems, a class of problems that, to the best of our knowledge and despite their applications, have not received much attention so far. Two of the most prominent problems in this class are angular sorting queries and sorted K-nearest neighbour queries. The former...... asks us to preprocess an input point set S in the plane so that, given a query point q, the clockwise ordering of the points in S around q can be computed efficiently. In the latter problem, the output is the list of K points in S closest to q, sorted by increasing distance from q. The goal in both...

  19. Linear stochastic systems a geometric approach to modeling, estimation and identification

    CERN Document Server

    Lindquist, Anders

    2015-01-01

    This book presents a treatise on the theory and modeling of second-order stationary processes, including an exposition on selected application areas that are important in the engineering and applied sciences. The foundational issues regarding stationary processes dealt with in the beginning of the book have a long history, starting in the 1940s with the work of Kolmogorov, Wiener, Cramér and his students, in particular Wold, and have since been refined and complemented by many others. Problems concerning the filtering and modeling of stationary random signals and systems have also been addressed and studied, fostered by the advent of modern digital computers, since the fundamental work of R.E. Kalman in the early 1960s. The book offers a unified and logically consistent view of the subject based on simple ideas from Hilbert space geometry and coordinate-free thinking. In this framework, the concepts of stochastic state space and state space modeling, based on the notion of the conditional independence of pas...

  20. Numerical Simulation of 3D Solid-Liquid Turbulent Flow in a Low Specific Speed Centrifugal Pump: Performance Comparison of Four Geometric Models

    OpenAIRE

    Baocheng Shi; Jinjia Wei

    2014-01-01

    For numerically simulating 3D solid-liquid turbulent flow in low specific speed centrifugal pumps, there exist several problems including how to design geometrical shape of the calculation model to represent the real pump and how to predict pump performance accurately to guide the design of pump. To solve these problems, four kinds of geometric models were designed. The performance of a low specific speed solid-liquid centrifugal pump was predicted, and the results showed that the improved pr...

  1. Model theory and algebraic geometry an introduction to E. Hrushovski’s proof of the geometric Mordell-Lang conjecture

    CERN Document Server

    1998-01-01

    This introduction to the recent exciting developments in the applications of model theory to algebraic geometry, illustrated by E. Hrushovski's model-theoretic proof of the geometric Mordell-Lang Conjecture starts from very basic background and works up to the detailed exposition of Hrushovski's proof, explaining the necessary tools and results from stability theory on the way. The first chapter is an informal introduction to model theory itself, making the book accessible (with a little effort) to readers with no previous knowledge of model theory. The authors have collaborated closely to achieve a coherent and self- contained presentation, whereby the completeness of exposition of the chapters varies according to the existence of other good references, but comments and examples are always provided to give the reader some intuitive understanding of the subject.

  2. 基于链码的人脸表情几何特征提取%Facial Expression Geometrical Feature Extraction Based on Chain Code

    Institute of Scientific and Technical Information of China (English)

    张庆; 代锐; 朱雪莹; 韦穗

    2012-01-01

    已有人脸表情特征提取算法的表情识别率较低.为此,提出一种基于链码的人脸表情几何特征提取算法.以主动形状模型特征点定位为基础,对面部目标上定位的特征点位置进行循环链码编码,以提取出人脸表情几何特征.实验结果表明,相比经典的LBP表情特征鉴别方法,该算法的识别率提高约10%.%The existing facial expression recognition rate of facial expression feature extraction algorithm is low. For this, this paper proposes a facial geometric feature extraction algorithm based chain codes. Based on active shape model that locates feature points and outputs the points' coordinates of facial targets the coding method gives a circular codes to extract the facial geometric feature. Experimental results show that, compared with the method of typical LBP expression recognition, the accuracy of the algorithm is increased by nearly 10%.

  3. Space-time evolution of a growth fold (Betic Cordillera, Spain). Evidences from 3D geometrical modelling

    Science.gov (United States)

    Martin-Rojas, Ivan; Alfaro, Pedro; Estévez, Antonio

    2014-05-01

    We present a study that encompasses several software tools (iGIS©, ArcGIS©, Autocad©, etc.) and data (geological mapping, high resolution digital topographic data, high resolution aerial photographs, etc.) to create a detailed 3D geometric model of an active fault propagation growth fold. This 3D model clearly shows structural features of the analysed fold, as well as growth relationships and sedimentary patterns. The results obtained permit us to discuss the kinematics and structural evolution of the fold and the fault in time and space. The study fault propagation fold is the Crevillente syncline. This fold represents the northern limit of the Bajo Segura Basin, an intermontane basin in the Eastern Betic Cordillera (SE Spain) developed from upper Miocene on. 3D features of the Crevillente syncline, including growth pattern, indicate that limb rotation and, consequently, fault activity was higher during Messinian than during Tortonian; consequently, fault activity was also higher. From Pliocene on our data point that limb rotation and fault activity steadies or probably decreases. This in time evolution of the Crevillente syncline is not the same all along the structure; actually the 3D geometric model indicates that observed lateral heterogeneity is related to along strike variation of fault displacement.

  4. Optimal point of insertion of the needle in neuraxial blockade using a midline approach: study in a geometrical model

    Science.gov (United States)

    Vogt, Mark; van Gerwen, Dennis J; van den Dobbelsteen, John J; Hagenaars, Martin

    2016-01-01

    Performance of neuraxial blockade using a midline approach can be technically difficult. It is therefore important to optimize factors that are under the influence of the clinician performing the procedure. One of these factors might be the chosen point of insertion of the needle. Surprisingly few data exist on where between the tips of two adjacent spinous processes the needle should be introduced. A geometrical model was adopted to gain more insight into this issue. Spinous processes were represented by parallelograms. The length, the steepness relative to the skin, and the distance between the parallelograms were varied. The influence of the chosen point of insertion of the needle on the range of angles at which the epidural and subarachnoid space could be reached was studied. The optimal point of insertion was defined as the point where this range is the widest. The geometrical model clearly demonstrated, that the range of angles at which the epidural or subarachnoid space can be reached, is dependent on the point of insertion between the tips of the adjacent spinous processes. The steeper the spinous processes run, the more cranial the point of insertion should be. Assuming that the model is representative for patients, the performance of neuraxial blockade using a midline approach might be improved by choosing the optimal point of insertion.

  5. Geometric model of black hole quantum $N$-portrait, extradimensions and thermodynamics

    CERN Document Server

    Frassino, Antonia M; Nicolini, Piero

    2016-01-01

    Recently a short scale modified black hole metric, known as holographic metric, has been proposed in order to capture the self-complete character of gravity. In this paper we show that such a metric can reproduce some geometric features expected from the quantum $N$-portrait beyond the semi-classical limit. We show that for a generic $N$ this corresponds to having an effective energy momentum tensor in Einstein equations or, equivalently, non-local terms in the gravity action. We also consider the higher dimensional extension of the metric and the case of an AdS cosmological term. We provide a detailed thermodynamic analysis of both cases, with particular reference to the repercussions on the Hawking-Page phase transition.

  6. Geometric Model of Black Hole Quantum N-portrait, Extradimensions and Thermodynamics

    Directory of Open Access Journals (Sweden)

    Antonia M. Frassino

    2016-05-01

    Full Text Available Recently a short scale modified black hole metric, known as holographic metric, has been proposed in order to capture the self-complete character of gravity. In this paper we show that such a metric can reproduce some geometric features expected from the quantum N-portrait beyond the semi-classical limit. We show that for a generic N this corresponds to having an effective energy momentum tensor in Einstein equations or, equivalently, non-local terms in the gravity action. We also consider the higher dimensional extension of the metric and the case of an AdS cosmological term. We provide a detailed thermodynamic analysis of both cases, with particular reference to the repercussions on the Hawking-Page phase transition.

  7. PREFACE: Geometrically frustrated magnetism Geometrically frustrated magnetism

    Science.gov (United States)

    Gardner, Jason S.

    2011-04-01

    Frustrated magnetism is an exciting and diverse field in condensed matter physics that has grown tremendously over the past 20 years. This special issue aims to capture some of that excitement in the field of geometrically frustrated magnets and is inspired by the 2010 Highly Frustrated Magnetism (HFM 2010) meeting in Baltimore, MD, USA. Geometric frustration is a broad phenomenon that results from an intrinsic incompatibility between some fundamental interactions and the underlying lattice geometry based on triangles and tetrahedra. Most studies have centred around the kagomé and pyrochlore based magnets but recent work has looked at other structures including the delafossite, langasites, hyper-kagomé, garnets and Laves phase materials to name a few. Personally, I hope this issue serves as a great reference to scientist both new and old to this field, and that we all continue to have fun in this very frustrated playground. Finally, I want to thank the HFM 2010 organizers and all the sponsors whose contributions were an essential part of the success of the meeting in Baltimore. Geometrically frustrated magnetism contents Spangolite: an s = 1/2 maple leaf lattice antiferromagnet? T Fennell, J O Piatek, R A Stephenson, G J Nilsen and H M Rønnow Two-dimensional magnetism and spin-size effect in the S = 1 triangular antiferromagnet NiGa2S4 Yusuke Nambu and Satoru Nakatsuji Short range ordering in the modified honeycomb lattice compound SrHo2O4 S Ghosh, H D Zhou, L Balicas, S Hill, J S Gardner, Y Qi and C R Wiebe Heavy fermion compounds on the geometrically frustrated Shastry-Sutherland lattice M S Kim and M C Aronson A neutron polarization analysis study of moment correlations in (Dy0.4Y0.6)T2 (T = Mn, Al) J R Stewart, J M Hillier, P Manuel and R Cywinski Elemental analysis and magnetism of hydronium jarosites—model kagome antiferromagnets and topological spin glasses A S Wills and W G Bisson The Herbertsmithite Hamiltonian: μSR measurements on single crystals

  8. Automatic recognition of cardiac arrhythmias based on the geometric patterns of Poincaré plots

    International Nuclear Information System (INIS)

    The Poincaré plot emerges as an effective tool for assessing cardiovascular autonomic regulation. It displays nonlinear characteristics of heart rate variability (HRV) from electrocardiographic (ECG) recordings and gives a global view of the long range of ECG signals. In the telemedicine or computer-aided diagnosis system, it would offer significant auxiliary information for diagnosis if the patterns of the Poincaré plots can be automatically classified. Therefore, we developed an automatic classification system to distinguish five geometric patterns of the Poincaré plots from four types of cardiac arrhythmias. The statistics features are designed on measurements and an ensemble classifier of three types of neural networks is proposed. Aiming at the difficulty to set a proper threshold for classifying the multiple categories, the threshold selection strategy is analyzed. 24 h ECG monitoring recordings from 674 patients, which have four types of cardiac arrhythmias, are adopted for recognition. For comparison, Support Vector Machine (SVM) classifiers with linear and Gaussian kernels are also applied. The experiment results demonstrate the effectiveness of the extracted features and the better performance of the designed classifier. Our study can be applied to diagnose the corresponding sinus rhythm and arrhythmia substrates disease automatically in the telemedicine and computer-aided diagnosis system. (paper)

  9. Improved Treatment of the Breast and Supraclavicular Fossa Based on a Simple Geometrical Principle

    Energy Technology Data Exchange (ETDEWEB)

    Yavetz, Dalia, E-mail: dalia.yavetz@gmail.com [Institute of Radiotherapy, Tel Aviv (Israel); Corn, Benjamin W.; Matceyevsky, Diana; Ben-Josef, Rahamim; Soyfer, Viacheslav [Institute of Radiotherapy, Tel Aviv (Israel); Bershtein, Igal [Diagnostic Imaging, Tel Aviv Medical Center, Tel Aviv (Israel); Inbar, Moshe; Ron, Ilan [Department of Medical Oncology, Tel Aviv (Israel); Jiveliouk, Irena [Institute of Radiotherapy, Tel Aviv (Israel); Department of Medical Oncology, Tel Aviv (Israel); Diagnostic Imaging, Tel Aviv Medical Center, Tel Aviv (Israel); Schifter, Dan [Institute of Radiotherapy, Tel Aviv (Israel)

    2011-01-01

    In breast cancer, nodal irradiation has become routine, but adds time and creates concerns for field overlap if the 'match' is not accurate. We developed a technique to address these issues by using only one isocenter for both areas. Tangents are designed at simulation. The isocenter is then shifted to the upper border of the breast using a straightforward geometrical calculation. After determining the new isocenter, fields are recreated wherein the tangents are treated with a quarter beam and the supraclavicular field fashioned with a half-beam block. The gantry, collimator, and couch angles of the supraclavicular field are adjusted to achieve an accurate match. Ten patients were evaluated. Doses to the spinal cord and brachial plexus were lowered relative to conventional techniques. The hot spots were not augmented. In comparison with standard arrangements, setup time decreased. Accurate matching was consistently achieved and verified by portal imaging. A new approach for treating the supraclavicular fossa is easily executed. Advantages include negligible doses to the critical neural structures (i.e., spinal cord and brachial plexus), optimized matchline, and reduced setup time.

  10. Automatic recognition of cardiac arrhythmias based on the geometric patterns of Poincaré plots.

    Science.gov (United States)

    Zhang, Lijuan; Guo, Tianci; Xi, Bin; Fan, Yang; Wang, Kun; Bi, Jiacheng; Wang, Ying

    2015-02-01

    The Poincaré plot emerges as an effective tool for assessing cardiovascular autonomic regulation. It displays nonlinear characteristics of heart rate variability (HRV) from electrocardiographic (ECG) recordings and gives a global view of the long range of ECG signals. In the telemedicine or computer-aided diagnosis system, it would offer significant auxiliary information for diagnosis if the patterns of the Poincaré plots can be automatically classified. Therefore, we developed an automatic classification system to distinguish five geometric patterns of the Poincaré plots from four types of cardiac arrhythmias. The statistics features are designed on measurements and an ensemble classifier of three types of neural networks is proposed. Aiming at the difficulty to set a proper threshold for classifying the multiple categories, the threshold selection strategy is analyzed. 24 h ECG monitoring recordings from 674 patients, which have four types of cardiac arrhythmias, are adopted for recognition. For comparison, Support Vector Machine (SVM) classifiers with linear and Gaussian kernels are also applied. The experiment results demonstrate the effectiveness of the extracted features and the better performance of the designed classifier. Our study can be applied to diagnose the corresponding sinus rhythm and arrhythmia substrates disease automatically in the telemedicine and computer-aided diagnosis system. PMID:25582837

  11. A geometric network model of intrinsic grey-matter connectivity of the human brain

    Science.gov (United States)

    Lo, Yi-Ping; O'Dea, Reuben; Crofts, Jonathan J.; Han, Cheol E.; Kaiser, Marcus

    2015-10-01

    Network science provides a general framework for analysing the large-scale brain networks that naturally arise from modern neuroimaging studies, and a key goal in theoretical neuroscience is to understand the extent to which these neural architectures influence the dynamical processes they sustain. To date, brain network modelling has largely been conducted at the macroscale level (i.e. white-matter tracts), despite growing evidence of the role that local grey matter architecture plays in a variety of brain disorders. Here, we present a new model of intrinsic grey matter connectivity of the human connectome. Importantly, the new model incorporates detailed information on cortical geometry to construct ‘shortcuts’ through the thickness of the cortex, thus enabling spatially distant brain regions, as measured along the cortical surface, to communicate. Our study indicates that structures based on human brain surface information differ significantly, both in terms of their topological network characteristics and activity propagation properties, when compared against a variety of alternative geometries and generative algorithms. In particular, this might help explain histological patterns of grey matter connectivity, highlighting that observed connection distances may have arisen to maximise information processing ability, and that such gains are consistent with (and enhanced by) the presence of short-cut connections.

  12. Geometric Dequantization

    CERN Document Server

    Gozzi, E

    2004-01-01

    Dequantization is a set of rules which turn quantum mechanics (QM) into classical mechanics (CM). It is not the WKB limit of QM. In this paper we show that, by extending time to a 3-dimensional "supertime", we can dequantize the system in the sense of turning the Feynman path integral version of QM into the functional counterpart of the Koopman-von Neumann operatorial approach to CM. Somehow this procedure is the inverse of geometric quantization and we present it in three different polarizations: the Schroedinger, the momentum and the coherent states ones.

  13. Reexamination of Nuclear Shape Transitions in Gadolinium and Dysprosium Isotopes Chains by Using the Geometric Collective Model

    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.

  14. Interrelationships between densitometric, geometric, and mechanical properties of rat femora: inferences concerning mechanical regulation of bone modeling.

    Science.gov (United States)

    Ferretti, J L; Capozza, R F; Mondelo, N; Zanchetta, J R

    1993-11-01

    A compensation for differences in bone material quality by bone geometric properties in femora from two different strains of rats was previously shown by us. A feedback mechanism controlling the mechanical properties of the integrated bones was then proposed, in accordance with Frost's mechanostat theory. Evidence of such a system is now offered by the finding of a negative correlation between the modeling-dependent cross-sectional architecture (moment of inertia) and the mineral-dependent stiffness (elastic modulus) of bone material in the femoral diaphyses of 45 normal Wistar rats of different sexes, ages, and sizes. The strength and stiffness of the integrated diaphyses were found to depend on both cross-sectional inertia and body weight, not on bone mineral density. These findings are interpreted as supporting the hypothesis that the architectural efficiency of diaphyseal cross-sectional design resulting from the spatial orientation of bone modeling during growth is optimized as a function of the body weight-dependent bone strain history, within the constraints imposed by bone stiffness. Results suggest a modulating role of biomass, related to the system set point determination, and explain the usually observed lack of a direct correlation between mineral density and strength or stiffness of long bones in studies of geometrically inhomogeneous populations. PMID:8266830

  15. Precision fabrication of large area silicon-based geometrically enhanced x-ray photocathodes using plasma etching

    Science.gov (United States)

    Opachich, Y. P.; Chen, N.; Bell, P. M.; Bradley, D. K.; Feng, J.; Gopal, A.; Hilsabeck, T. J.; Huffman, E.; Koch, J. A.; Landen, O. L.; MacPhee, A. G.; Nagel, S. R.; Udin, S.

    2015-08-01

    Geometrically enhanced photocathodes are currently being developed for use in applications that seek to improve detector efficiency in the visible to X-ray ranges. Various photocathode surface geometries are typically chosen based on the detector operational wavelength region, along with requirements such as spatial resolution, temporal resolution and dynamic range. Recently, a structure has been identified for possible use in the X-ray region. This anisotropic high aspect ratio structure has been produced in silicon using inductively coupled plasma (ICP) etching technology. The process is specifically developed with respect to the pattern density and geometry of the photocathode chip to achieve the desired sidewall profile angle. The tapered sidewall profile angle precision has been demonstrated to be within +/- 2.5° for a ~ 12° wall angle, with feature sizes that range between 4-9 μm in diameter and 10-25 μm depth. Here we discuss the device applications, design and present the method used to produce a set of geometrically enhanced high yield X-ray photocathodes in silicon.

  16. Finite element modelling approaches for well-ordered porous metallic materials for orthopaedic applications: cost effectiveness and geometrical considerations.

    Science.gov (United States)

    Quevedo González, Fernando José; Nuño, Natalia

    2016-06-01

    The mechanical properties of well-ordered porous materials are related to their geometrical parameters at the mesoscale. Finite element (FE) analysis is a powerful tool to design well-ordered porous materials by analysing the mechanical behaviour. However, FE models are often computationally expensive. This article aims to develop a cost-effective FE model to simulate well-ordered porous metallic materials for orthopaedic applications. Solid and beam FE modelling approaches are compared, using finite size and infinite media models considering cubic unit cell geometry. The model is then applied to compare two unit cell geometries: cubic and diamond. Models having finite size provide similar results than the infinite media model approach for large sample sizes. In addition, these finite size models also capture the influence of the boundary conditions on the mechanical response for small sample sizes. The beam FE modelling approach showed little computational cost and similar results to the solid FE modelling approach. Diamond unit cell geometry appeared to be more suitable for orthopaedic applications than the cubic unit cell geometry. PMID:26260268

  17. Detailed Primitive-Based 3d Modeling of Architectural Elements

    Science.gov (United States)

    Remondino, F.; Lo Buglio, D.; Nony, N.; De Luca, L.

    2012-07-01

    The article describes a pipeline, based on image-data, for the 3D reconstruction of building façades or architectural elements and the successive modeling using geometric primitives. The approach overcome some existing problems in modeling architectural elements and deliver efficient-in-size reality-based textured 3D models useful for metric applications. For the 3D reconstruction, an opensource pipeline developed within the TAPENADE project is employed. In the successive modeling steps, the user manually selects an area containing an architectural element (capital, column, bas-relief, window tympanum, etc.) and then the procedure fits geometric primitives and computes disparity and displacement maps in order to tie visual and geometric information together in a light but detailed 3D model. Examples are reported and commented.

  18. Sharpness in the k-nearest neighbours random geometric graph model

    CERN Document Server

    Falgas-Ravry, Victor

    2011-01-01

    Let $S_{n,k}$ denote the random geometric graph obtained by placing points in a square box of area $n$ according to a Poisson process of intensity $1$ and joining each point to its $k$ nearest neighbours. Balister, Bollob\\'as, Sarkar and Walters conjectured that for every $0< \\epsilon <1$ and all $n$ sufficiently large there exists $C=C(\\epsilon)$ such that whenever the probability $S_{n,k}$ is connected is at least $\\epsilon $ then the probability $S_{n,k+C}$ is connected is at least $1-\\epsilon $. In this paper we prove this conjecture. As a corollary we prove that there is a constant $C'$ such that whenever $k=k(n)$ is a sequence of integers such that the probability $S_{n,k(n)}$ is connected tends to one as $n$ tends to infinity, then for any $s(n)$ with $s(n)=o(\\log n)$, the probability that $S_{n,k(n)+C's\\log \\log n}$ is $s$-connected tends to one This proves another conjecture of Balister, Bollob\\'as, Sarkar and Walters.

  19. An optimization-based method for geometrical calibration in cone-beam CT without dedicated phantoms

    Science.gov (United States)

    Panetta, D.; Belcari, N.; DelGuerra, A.; Moehrs, S.

    2008-07-01

    In this paper we present a new method for the determination of geometrical misalignments in cone-beam CT scanners, from the analysis of the projection data of a generic object. No a priori knowledge of the object shape and positioning is required. We show that a cost function, which depends on the misalignment parameters, can be defined using the projection data and that such a cost function has a local minimum in correspondence to the actual parameters of the system. Hence, the calibration of the scanner can be carried out by minimizing the cost function using standard optimization techniques. The method is developed for a particular class of 3D object functions, for which the redundancy of the fan beam sinogram in the transaxial midplane can be extended to cone-beam projection data, even at wide cone angles. The method has an approximated validity for objects which do not belong to that class; in that case, a suitable subset of the projection data can be selected in order to compute the cost function. We show by numerical simulations that our method is capable to determine with high accuracy the most critical misalignment parameters of the scanner, i.e., the transversal shift and the skew of the detector. Additionally, the detector slant can be determined. Other parameters such as the detector tilt, the longitudinal shift and the error in the source-detector distance cannot be determined with our method, as the proposed cost function has a very weak dependence on them. However, due to the negligible influence of these latter parameters in the reconstructed image quality, they can be kept fixed at estimated values in both calibration and reconstruction processes without compromising the final result. A trade-off between computational cost and calibration accuracy must be considered when choosing the data subset used for the computation of the cost function. Results on real data of a mouse femur as obtained with a small animal micro-CT are shown as well, proving

  20. Introduction to Clifford's Geometric Algebra

    OpenAIRE

    Hitzer, Eckhard

    2013-01-01

    Geometric algebra was initiated by W.K. Clifford over 130 years ago. It unifies all branches of physics, and has found rich applications in robotics, signal processing, ray tracing, virtual reality, computer vision, vector field processing, tracking, geographic information systems and neural computing. This tutorial explains the basics of geometric algebra, with concrete examples of the plane, of 3D space, of spacetime, and the popular conformal model. Geometric algebras are ideal to represen...

  1. Multidimensional Geometrical Model of the Electrical and SU(2) Colour Charge with Splitting off the Supplementary Coordinates

    CERN Document Server

    Dzhunushaliev, V D

    1996-01-01

    The geometrical model of an electrical charge is proposed. This model has the ''nake'' charge shunted with ``fur - coat'' consisting of virtual wormholes. The 5D wormhole solution in the Kaluza - Klein's theory is the ''nake'' charge. The splitting off the supplementary coordinates happens on the two spheres (null surfaces) bounding this 5D wormhole. This allows to sew two Reissner - Nordström's black holes to it on both sides. Virtual wormholes entrap a part of the electrical force lines outcoming from ''nake'' charge. This effect can essentially decrease the charge visible at infinity up to real relation $m^2 < e^2$. The analogical construction for colour SU(2) gauge charge is made.

  2. Comparison of experiment and models of geodesic acoustic mode frequency and amplitude geometric scaling in ASDEX Upgrade

    Science.gov (United States)

    Simon, P.; Conway, G. D.; Stroth, U.; Biancalani, A.; Palermo, F.; the ASDEX Upgrade Team

    2016-04-01

    In a set of dedicated ASDEX Upgrade shape-scan experiments, the influence of plasma geometry on the frequency and amplitude behaviour of the geodesic acoustic mode (GAM), measured by Doppler reflectometry, is studied. In both limiter and divertor configurations, the plasma elongation was varied between circular and highly elongated states (1.1effects. The experimentally observed effect of decreasing {ω\\text{GAM}} with increasing κ is predicted by most models. Other geometric factors, such as inverse aspect ratio ε and Shafranov shift gradient {Δ\\prime} are also seen to be influential in determining a reliable lower {ω\\text{GAM}} boundary. The GAM amplitude is found to vary with boundary elongation {κ\\text{b}} and safety factor q. The collisional damping is compared to multiple models for the collisionless damping. Collisional damping appears to play a stronger role in the divertor configuration, while collisional and collisionless damping both may contribute to the GAM amplitude in the limiter configuration.

  3. Assessment of the influence of the compliant aortic root on aortic valve mechanics by means of a geometrical model.

    Science.gov (United States)

    Redaelli, A; Di Martino, E; Gamba, A; Procopio, A M; Fumero, R

    1997-12-01

    In recent years several researchers have suggested that the changes in the geometry and angular dimensions of the aortic root which occur during the cardiac cycle are functional to the optimisation of aortic valve function, both in terms of diminishing leaflet stresses and of fluid-dynamic behaviour. The paper presents an analytical parametric model of the aortic valve which includes the aortic root movement. The indexes used to evaluate the valve behaviour are the circumferential membrane stress and the stress at the free edge of the leaflet, the index of bending strain, the bending of the leaflet at the line attachment in the radial and circumferential directions and the shape of the conduit formed by the leaflets during systole. In order to evaluate the role of geometric changes in valve performance, two control cases were considered, with different reference geometric configuration, where the movement of the aortic root was ignored. The results obtained appear consistent with physiological data, especially with regard to the late diastolic phase and the early ejection phase, and put in evidence the role of the aortic root movement in the improvement of valve behaviour. PMID:9450254

  4. Modeling and Characterization of Geometric Effects on the Performance of Rainbow and Thunder Actuators

    Science.gov (United States)

    Schwartz, Robert W.; Ballato, J.; Northwang, W. D.; Laoratanakul, P.

    2000-01-01

    Dome formation in Rainbow and Thunder actuators occurs to relieve thermal expansion mismatch stress between the metallic and piezoelectric layers during cooling from device fabrication temperatures. Accompanying this process is the generation of an internal stress profile within the devices and the development of significant tensile stresses within the surface region of the piezoelectric. These tensile stresses affect the domain configuration (ratio of c-to-a domains), and improve the 90 deg. domain wall movement response of the device in this region of the piezoelectric. This results in improved electromechanical performance compared to standard direct extensional and flextensional devices, presumably because of the contributions of stress to the non-linearity of the piezoelectric d-coefficients. 1 Interestingly, this improvement in response seems counterintuitive; a stress perpendicular to the direction of the applied electric field should impede, not contribute to 90' domain switching. Further consideration of the lower region of the piezoelectric that is under compressive stress thus appears warranted. The specified objectives of the research were to: 1. Conduct finite element and equivalent circuit simulation-based investigations to understand the effects of actuator geometry on internal stress distribution and actuator performance (displacement and load-bearing capabilities). 2. Use the results of the modeling studies to predict the processing conditions (geometry and thickness ratio) required for the fabrication of Rainbow ceramics with optimized performance.

  5. Theory for Gaussian beam diffraction in 2D inhomogeneous medium, based on the eikonal form of complex geometrical optics

    International Nuclear Information System (INIS)

    A simple and effective method to describe Gaussian beams propagation and diffraction in arbitrary smoothly inhomogeneous 2D medium has been developed based on the eikonal form of complex geometrical optics. The method assumes the eikonal equation can be solved in paraxial approximation in curvilinear frame of references, connected with the central ray. The Riccati-type ordinary differential equation is derived for complex parameter characterizing the Gaussian beam width and phase front curvature. The same parameter was proved to define both the modulus and the argument of the complex amplitude. As a result, the problem of the Gaussian beam diffraction in inhomogeneous media has been reduced to the solution of the ordinary differential equation of the first order, which can be readily calculated numerically for arbitrary profile of dielectric permittivity

  6. Diffraction of Gaussian beam in 3D smoothly inhomogeneous media: eikonal-based complex geometrical optics approach

    CERN Document Server

    Berczynski, P; Kravtsov, Y A; Stateczny, A; Kravtsov, Yu.A.

    2005-01-01

    A simple and effective method based on the eikonal form of complex geometrical optics is presented to describe scalar Gaussian beams propagation and diffraction in arbitrary 3D smoothly inhomogeneous medium. Similarly to paraxial WKB approach the method reduces the wave problem to a set of ordinary differential equations of Riccati type. This substantially simplifies the solution as compared to full wave or quasy-optics equations. The method assumes the complex eikonal equation to be solved in paraxial approximation in curvilinear coordinate frame, which is associated with the central ray of the beam and performs Levi-Civita parallel transport. In this way the system of Riccati-type equations is obtained for complex parameters, which characterize both the beam cross-section and the shape of the phase front. For Gaussian beam propagating in homogeneous medium or along the symmetry axis in lens-like medium, these equations possess analytical solutions, otherwise they can be readily solved numerically. In contra...

  7. Theory for Gaussian beam diffraction in 2D inhomogeneous medium, based on the eikonal form of complex geometrical optics

    Science.gov (United States)

    Berczynski, P.; Kravtsov, Yu. A.

    2004-10-01

    A simple and effective method to describe Gaussian beams propagation and diffraction in arbitrary smoothly inhomogeneous 2D medium has been developed based on the eikonal form of complex geometrical optics. The method assumes the eikonal equation can be solved in paraxial approximation in curvilinear frame of references, connected with the central ray. The Riccati-type ordinary differential equation is derived for complex parameter characterizing the Gaussian beam width and phase front curvature. The same parameter was proved to define both the modulus and the argument of the complex amplitude. As a result, the problem of the Gaussian beam diffraction in inhomogeneous media has been reduced to the solution of the ordinary differential equation of the first order, which can be readily calculated numerically for arbitrary profile of dielectric permittivity.

  8. Theory for Gaussian beam diffraction in 2D inhomogeneous medium, based on the eikonal form of complex geometrical optics

    Energy Technology Data Exchange (ETDEWEB)

    Berczynski, P. [Institute of Physics, Technical University of Szczecin, Szczecin 70-310 (Poland); Kravtsov, Yu.A. [Space Research Institute, Russian Academy of Science, Moscow 117 997 (Russian Federation) and Institute of Physics, Maritime University of Szczecin, Szczecin 70-500 (Poland)]. E-mail: kravtsov@wsm.szczecin.pl

    2004-10-18

    A simple and effective method to describe Gaussian beams propagation and diffraction in arbitrary smoothly inhomogeneous 2D medium has been developed based on the eikonal form of complex geometrical optics. The method assumes the eikonal equation can be solved in paraxial approximation in curvilinear frame of references, connected with the central ray. The Riccati-type ordinary differential equation is derived for complex parameter characterizing the Gaussian beam width and phase front curvature. The same parameter was proved to define both the modulus and the argument of the complex amplitude. As a result, the problem of the Gaussian beam diffraction in inhomogeneous media has been reduced to the solution of the ordinary differential equation of the first order, which can be readily calculated numerically for arbitrary profile of dielectric permittivity.

  9. Method to improve the accuracy of the geometrical parameters measurement in stereoscopic AOTF-based spectral imagers

    International Nuclear Information System (INIS)

    The problem of non-contact geometrical measurements by the stereoscopic spectral AOTF-based imagers is considered. Major factors contributing to the measurement error are analyzed for the first time. Expressions are derived for area measurement inaccuracy on arbitrary shape surfaces, caused by measurement errors of individual points' 3D coordinates with and without a priori information about surface shape. Verification of the obtained expressions with the real experimental data showed that area measurement error for a complex figure, given by the set of points, is caused mainly by ignoring the fact that these points belong to the surface. It is shown that the use of a priori information about investigated surface shape, which is often available from the design documentation, in many cases would radically improve the accuracy of surface defects area measurement. The presented results can be effectively used for the development of new 3D spectral imagers and modernization of existing ones

  10. A Multiple-Mechanism Developmental Model for Defining Self-Organizing Geometric Structures

    OpenAIRE

    Fleischer, Kurt W.

    1995-01-01

    This thesis introduces a model of multicellular development. The model combines elements of the chemical, cell lineage, and mechanical models of morphogenesis pioneered by Turing, Lindenmayer, and Odell, respectively. The internal state of each cell in the model is represented by a time-varying state vector that is updated by a differential equation. The differential equation is formulated as a sum of contributions from different sources, describing gene transcription, kinetics, and cell meta...

  11. Geometric Data Perturbation-Based Personal Health Record Transactions in Cloud Computing

    OpenAIRE

    Balasubramaniam, S; Kavitha, V.

    2015-01-01

    Cloud computing is a new delivery model for information technology services and it typically involves the provision of dynamically scalable and often virtualized resources over the Internet. However, cloud computing raises concerns on how cloud service providers, user organizations, and governments should handle such information and interactions. Personal health records represent an emerging patient-centric model for health information exchange, and they are outsourced for storage by third pa...

  12. Geometrical versus semiclassical quantization

    International Nuclear Information System (INIS)

    The dynamical variational approach based on geometrical quantization is demonstrated to be capable in describing the most important quantum mechanical quantities. In particular, the method appears to be much better under control than the traditional semiclassical methods in treating the systems whose classical counterparts are chaotic. The formal considerations are illustrated using an exactly solvable SU(3)-spin system. (orig.)

  13. Patient-specific geometrical modeling of orthopedic structures with high efficiency and accuracy for finite element modeling and 3D printing.

    Science.gov (United States)

    Huang, Huajun; Xiang, Chunling; Zeng, Canjun; Ouyang, Hanbin; Wong, Kelvin Kian Loong; Huang, Wenhua

    2015-12-01

    We improved the geometrical modeling procedure for fast and accurate reconstruction of orthopedic structures. This procedure consists of medical image segmentation, three-dimensional geometrical reconstruction, and assignment of material properties. The patient-specific orthopedic structures reconstructed by this improved procedure can be used in the virtual surgical planning, 3D printing of real orthopedic structures and finite element analysis. A conventional modeling consists of: image segmentation, geometrical reconstruction, mesh generation, and assignment of material properties. The present study modified the conventional method to enhance software operating procedures. Patient's CT images of different bones were acquired and subsequently reconstructed to give models. The reconstruction procedures were three-dimensional image segmentation, modification of the edge length and quantity of meshes, and the assignment of material properties according to the intensity of gravy value. We compared the performance of our procedures to the conventional procedures modeling in terms of software operating time, success rate and mesh quality. Our proposed framework has the following improvements in the geometrical modeling: (1) processing time: (femur: 87.16 ± 5.90 %; pelvis: 80.16 ± 7.67 %; thoracic vertebra: 17.81 ± 4.36 %; P < 0.05); (2) least volume reduction (femur: 0.26 ± 0.06 %; pelvis: 0.70 ± 0.47, thoracic vertebra: 3.70 ± 1.75 %; P < 0.01) and (3) mesh quality in terms of aspect ratio (femur: 8.00 ± 7.38 %; pelvis: 17.70 ± 9.82 %; thoracic vertebra: 13.93 ± 9.79 %; P < 0.05) and maximum angle (femur: 4.90 ± 5.28 %; pelvis: 17.20 ± 19.29 %; thoracic vertebra: 3.86 ± 3.82 %; P < 0.05). Our proposed patient-specific geometrical modeling requires less operating time and workload, but the orthopedic structures were generated at a higher rate of success as compared with the conventional method. It is expected to benefit the surgical planning of orthopedic

  14. Geometric programming for communication systems

    CERN Document Server

    Chiang, Mung

    2014-01-01

    Recently Geometric Programming has been applied to study a variety of problems in the analysis and design of communication systems from information theory and queuing theory to signal processing and network protocols. ""Geometric Programming for Communication Systems"" begins its comprehensive treatment of the subject by providing an in-depth tutorial on the theory, algorithms, and modeling methods of Geometric Programming. It then gives a systematic survey of the applications of Geometric Programming to the study of communication systems. It collects in one place various published results in

  15. Size-dependent geometrically nonlinear free vibration analysis of fractional viscoelastic nanobeams based on the nonlocal elasticity theory

    Science.gov (United States)

    Ansari, R.; Faraji Oskouie, M.; Gholami, R.

    2016-01-01

    In recent decades, mathematical modeling and engineering applications of fractional-order calculus have been extensively utilized to provide efficient simulation tools in the field of solid mechanics. In this paper, a nonlinear fractional nonlocal Euler-Bernoulli beam model is established using the concept of fractional derivative and nonlocal elasticity theory to investigate the size-dependent geometrically nonlinear free vibration of fractional viscoelastic nanobeams. The non-classical fractional integro-differential Euler-Bernoulli beam model contains the nonlocal parameter, viscoelasticity coefficient and order of the fractional derivative to interpret the size effect, viscoelastic material and fractional behavior in the nanoscale fractional viscoelastic structures, respectively. In the solution procedure, the Galerkin method is employed to reduce the fractional integro-partial differential governing equation to a fractional ordinary differential equation in the time domain. Afterwards, the predictor-corrector method is used to solve the nonlinear fractional time-dependent equation. Finally, the influences of nonlocal parameter, order of fractional derivative and viscoelasticity coefficient on the nonlinear time response of fractional viscoelastic nanobeams are discussed in detail. Moreover, comparisons are made between the time responses of linear and nonlinear models.

  16. Crowdsourcing Based 3d Modeling

    Science.gov (United States)

    Somogyi, A.; Barsi, A.; Molnar, B.; Lovas, T.

    2016-06-01

    Web-based photo albums that support organizing and viewing the users' images are widely used. These services provide a convenient solution for storing, editing and sharing images. In many cases, the users attach geotags to the images in order to enable using them e.g. in location based applications on social networks. Our paper discusses a procedure that collects open access images from a site frequently visited by tourists. Geotagged pictures showing the image of a sight or tourist attraction are selected and processed in photogrammetric processing software that produces the 3D model of the captured object. For the particular investigation we selected three attractions in Budapest. To assess the geometrical accuracy, we used laser scanner and DSLR as well as smart phone photography to derive reference values to enable verifying the spatial model obtained from the web-album images. The investigation shows how detailed and accurate models could be derived applying photogrammetric processing software, simply by using images of the community, without visiting the site.

  17. Geometrical Reconstruction and CNC Process of Spurious Tympanic Membrane Based on Reverse Engineering

    Institute of Scientific and Technical Information of China (English)

    LU Hong; PENG Jun; ZHOU Yongqing

    2006-01-01

    Perforation of tympanic membrane is one of the main reasons for both deafness and dyssaudia. We could improve and restore audition by restoring or replacing the tympanic membrane. So, whether you can make the spurious tympanic membrane successfully is one of the keys to a successful operation. Utilizing CMM (Coordinate Measuring Machine) measurement equipment, we measured tympanic membrane model precisely and digitally. We also analysed the measured data by point to surface and we have successfully reconstructed the CAD model of the spurious tympanic membrane. Using the model we have got, we schemed out the mold of spurious tympanic membrane. In addition, we utilized MasterCAM compiling CNC (Computerized Numerical Control) code and simulating the course of working. Ultimately, we obtained the mold of spurious tympanic membrane. Our research in this article has great significance to the success of spurious tympanic membrane grafting operation.

  18. Laboratory geometric calibration of areal digital aerial camera

    International Nuclear Information System (INIS)

    Digital aerial camera is non-metric camera. Geometric calibration, including the determination of interior orientation elements and distortion parameters, is the base of high precision photogrammetry. In this paper, a laboratory geometric calibration system of areal digital aerial cameras is developed. This system uses a collimator and a star tester as the target generator. After measurement of the coordinates of targets on the CCD plane and corresponding angles of parallel lights, the geometric calibration of digital aerial camera can be realized according to the geometric calibration model of this paper. Geometric calibration experiments are taken out based on this system using two kinds of mainstream digital aerial cameras, Cannon EOS 5D Mark II and Hasselblad H3D. Experiment results show that this system can satisfy the calibration requirements of aerial photogrammetric application and prove the correctness and the reliability of this calibration method

  19. A geometric Model for the Spatial Correlation of an Acoustic Vector Field in Surface-generated Noise

    Institute of Scientific and Technical Information of China (English)

    Yiwang Huang; Qunyan Ren; Ting Li

    2012-01-01

    Spatial correlation of sound pressure and particle velocity of the surface noise in horizontally stratified media was demonstrated,with directional noise sources uniformly distributed on the ocean surface.In the evaluation of particle velocity,plane wave approximation was applied to each incident ray.Due to the equivalence of the sound source correlation property and its directivity,solutions for the spatial correlation of the field were transformed into the integration of the coherent function generated by a single directional source.As a typical horizontally stratified media,surface noise in a perfect waveguide was investigated.Correlation coefficients given by normal mode and geometric models show satisfactory agreement.Also,the normalized covariance between sound pressure and the vertical component of particle velocity is proportional to acoustic absorption coefficient,while that of the surface noise in semi-infinitely homogeneous space is zero.

  20. 3D Geometric and Haptic Modeling of Hand-Woven Textile Artifacts

    OpenAIRE

    Shidanshidi, Hooman; Naghdy, Fazel; Naghdy, Golshah; Conroy, Diana Wood

    2010-01-01

    International audience Haptic Modeling of textile has attracted significant interest over the last decade. In spite of extensive research, no generic system has been proposed. The previous work mainly assumes that textile has a 2D planar structure. They also require time-consuming objective measurement of textile properties in mechanical/physical model construction. A novel approach for haptic modeling of textile is proposed to overcome the existing shortcomings. The method is generic, ass...

  1. Geometric Entropy

    CERN Document Server

    Das, Diptarka

    2010-01-01

    The laws of mechanics of stationary black holes bear a close resemblance with the laws of thermodynamics. This is not only a mathematical analogy but also a physical one that helps us answer deep questions related to the thermodynamic properties of the black holes. It turns out that we can define an entropy which is purely geometrical for black holes. In this thesis we explain Wald's formulation which identifies black hole entropy for an arbitrary covariant theory of gravity. We would like to know precisely what inputs go into arriving at Wald's formalism. This expression for the entropy clearly depends on the precise form of the action. The secondary theme of this thesis is to distinguish thermodynamic laws which are kinematic from those which are dynamical. We would like to see explicitly in the derivation of these laws, where exactly the form of action plays a role. In the beginning we motivate the definition of entropy using the Einstein-Hilbert Lagrangian. We encounter the Zeroth law, the Hawking radiati...

  2. Regularities pertinent to heat transfer between torch gas layers and steam boiler firebox waterwalls. Part I. Geometrical and physical torch model as a source of heat radiation

    Science.gov (United States)

    Makarov, A. N.

    2014-09-01

    The progress seen in the 19th-21st centuries in the development of methods for calculating heat transfer in torch furnaces, fireboxes, and combustion chambers is analyzed. Throughout the 20th century, calculations of heat transfer were carried out based on the law for radiation from solid bodies deduced by Y. Stefan and L. Boltzmann. It is shown that the use of this law for calculating heat transfer of a torch (a gaseous source of radiation) in heating furnaces and power-generating installations leads to incorrect results. It is substantiated that there is crisis of methods for calculating heat transfer in torch furnaces and power-generating installations. Geometrical and physical torch models in the form of radiating cylindrical gas volumes as sources of heat radiation are proposed for overcoming this crisis.

  3. Geometric Representation Of Visual Data In The Cortex Of Primates: Computer Reconstruction And Modeling Of Neo-Cortical Map And Column Systems

    Science.gov (United States)

    Schwartz, Eric

    1988-08-01

    Much of vertebrate midbrain and mammalian cortex is dedicated to two-dimensional "maps" in which two or more stimulus parameters are encoded by the position of neural activation in the map. Moreover, there are a large number of such maps which interact in an unknown fashion to yield a unified perception of the world. Our research program is based on studying the structure and function of brain maps. In the present paper, we review a recently constructed system of computer aided neuro-anatomy which allows high resolution texture mapped models of cortical surfaces in two and three dimensions to be displayed and manipulated. At the same time, this work demonstrates some of the basic geometric patterns of architecture of the primate brain, such as columnar and topographic mapping.

  4. The geometrization of matter proposal in the Barrett-Crane model and resolution of cosmological problems

    OpenAIRE

    Alexander, S.; Crane, L.; Sheppeard, M. D.

    2003-01-01

    We give an overview of the current issues in early universe cosmology and consider the potential resolution of these issues in an as yet nascent spin foam cosmology. The model is the Barrett-Crane Model for quantum gravity along with a generalization of manifold complexes to complexes including conical singularities.

  5. A method for geometric modelling of magnetic anomalies: Two dimensional bodies

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, T.C.S.

    for bodies of different shapes. A procedure has been evolved to compute the anomalies for all types of step and dyke models from a single formula by suitably reorienting the 'step model and by redefining its edges and the slope or dip angle. This method also...

  6. Finite elements/Taguchi method based procedure for the identification of the geometrical parameters significantly affecting the biomechanical behavior of a lumbar disc.

    Science.gov (United States)

    Cappetti, N; Naddeo, A; Naddeo, F; Solitro, G F

    2016-09-01

    The aim of this work is to show a quick and simple procedure able to identify the geometrical parameters of the intervertebral disc that strongly affect the behavior of the FEM model. First, we allocated a selection criterion for the minimum number of geometrical parameters that describe, with a good degree of approximation, a healthy human vertebra. Next, we carried out a sensitivity analysis using the 'Taguchi orthogonal array' to arrive at a quick identification of the parameters that strongly affect the behavior of the Fem model. PMID:26693883

  7. Scale effects and scaling-up by geometric-optical model

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This is a follow-up paper to our "Scale effect of Planck's law over nonisothermal blackbody surface".More examples are used to describe the scale effect in detail,and the scaling-up of Planck law over blackbody surface is further extended to three-dimension nonisothermal surface.This scaling-up results in a conceptual model for the directionality and spectral signature of thermal radiation at the scale of remote sensing pixels.This new model is also an improvement of Li-Strahler-Friedl conceptual model in a sense that the new model needs only statistic parameters at the pixel scale,without request of sub-pixel scale parameters as the LSF model does.

  8. Scale effects and scaling-up by geometric-optical model

    Institute of Scientific and Technical Information of China (English)

    李小文; 王锦地; A.H.Strahler

    2000-01-01

    This is a follow-up paper to our "Scale effect of Planck’s law over nonisothermal blackbody surface". More examples are used to describe the scale effect in detail, and the scaling-up of Planck law over blackbody surface is further extended to three-dimension nonisothermal surface. This scaling-up results in a conceptual model for the directionality and spectral signature of thermal radiation at the scale of remote sensing pixels. This new model is also an improvement of Li-Strahler-Friedl conceptual model in a sense that the new model needs only statistic parameters at the pixel scale, without request of sub-pixel scale parameters as the LSF model does.

  9. Bio-Economic Assessment of Different Sunflower Based Intercropping Systems at Different Geometric Configurations

    OpenAIRE

    Rashid Saleem; Umar Farooq, M.; Riaz Ahmed

    2003-01-01

    Studies to see the comparative productive efficiency and feasibility of different sunflower based intercropping systems were conducted at Agronomic Research area, University of Agriculture, Faisalabad. Intercropping systems included sunflower alone, sunflower + mash and sunflower + mung. Sunflower was sown in 90 cm apart single rows as well as 90 cm apart double row strips. The results of studies indicated that when sunflower grown alone gave the maximum yield of 2.89 t ha‾1 followed by 2.75 ...

  10. Joint QoS Multicast Power / Admission Control and Base Station Assignment : A Geometric Programming Approach

    OpenAIRE

    Karipidis, Eleftherios; Sidiropoulos, Nicholas; Tassiulas, Leandros

    2008-01-01

    The joint power control and base station (BS) assignment problem is considered under Quality-of-Service (QoS) constraints. If a feasible solution exists, the problem can be efficiently solved using existing distributed algorithms. Infeasibility is often encountered in practice, however, which brings up the issue of optimal admission control. The joint problem is NP-hard, yet important for QoS provisioning and bandwidth-efficient operation of existing and emerging cellular and overlay/underlay...

  11. Examining the Relationship between Forces During Stereolithography 3D Printing and Geometric Parameters of the Model

    OpenAIRE

    Kovalenko Iaroslav; Garan Maryna; Shynkarenko Andrii; Zelený Petr; Šafka Jiří

    2016-01-01

    In the case of stereolithography 3D printing technology, detaching formed model from the tank with photopolymer is a lengthy process. Forces, which appear during removing of solid photopolymer layerformed in stereolithography 3D DLP printer, can destroy the built model. In this article the detachment force is measured, obtained results arestatistically analyzed and relation between detach force, area of produced layer and thickness of the layer are verified. Linear dependence between detach f...

  12. Stationarity and geometric ergodicity of a class of nonlinear ARCH models

    OpenAIRE

    Saidi, Youssef; Zakoian, Jean-Michel

    2006-01-01

    A class of nonlinear ARCH processes is introduced and studied. The existence of a strictly stationary and $\\beta$-mixing solution is established under a mild assumption on the density of the underlying independent process. We give sufficient conditions for the existence of moments. The analysis relies on Markov chain theory. The model generalizes some important features of standard ARCH models and is amenable to further analysis.

  13. A Geometric Algorithm to construct new solitons in the O(3) Nonlinear Sigma Model

    CERN Document Server

    Barros, M

    2003-01-01

    The O(3) nonlinear sigma model with boundary, in dimension two, is considered. An algorithm to determine all its soliton solutions that preserve a rotational symmetry in the boundary is exhibited. This nonlinear problem is reduced to that of clamped elastica in a hyperbolic plane. These solutions carry topological charges that can be holographically determined from the boundary conditions. As a limiting case, we give a wide family of new soliton solutions in the free O(3) nonlinear sigma model.

  14. Structure design: an artificial intelligence-based method for the design of molecules under geometrical constraints.

    Science.gov (United States)

    Cohen, A A; Shatzmiller, S E

    1993-09-01

    This study presents an algorithm that implements artificial-intelligence techniques for automated, and site-directed drug design. The aim of the method is to link two or more predetermined functional groups into a sensible molecular structure. The proposed designing process mimics the classical manual design method, in which the drug designer sits in front of the computer screen and with the aid of computer graphics attempts to design the new drug. Therefore, the key principle of the algorithm is the parameterization of some criteria that affect the decision-making process carried out by the drug designer. This parameterization is based on the generation of weighting factors that reflect the knowledge and knowledge-based intuition of the drug designer, and thus add further rationalization to the drug design process. The proposed algorithm has been shown to yield a large variety of different structures, of which the drug designer may choose the most sensible. Performance tests indicate that with the proper set of parameters, the method generates a new structure within a short time. PMID:8110662

  15. Monte Carlo-based diffusion tensor tractography with a geometrically corrected voxel-centre connecting method

    International Nuclear Information System (INIS)

    Diffusion tensor tractography (DTT) allows one to explore axonal connectivity patterns in neuronal tissue by linking local predominant diffusion directions determined by diffusion tensor imaging (DTI). The majority of existing tractography approaches use continuous coordinates for calculating single trajectories through the diffusion tensor field. The tractography algorithm we propose is characterized by (1) a trajectory propagation rule that uses voxel centres as vertices and (2) orientation probabilities for the calculated steps in a trajectory that are obtained from the diffusion tensors of either two or three voxels. These voxels include the last voxel of each previous step and one or two candidate successor voxels. The precision and the accuracy of the suggested method are explored with synthetic data. Results clearly favour probabilities based on two consecutive successor voxels. Evidence is also provided that in any voxel-centre-based tractography approach, there is a need for a probability correction that takes into account the geometry of the acquisition grid. Finally, we provide examples in which the proposed fibre-tracking method is applied to the human optical radiation, the cortico-spinal tracts and to connections between Broca's and Wernicke's area to demonstrate the performance of the proposed method on measured data.

  16. Model-based geostatistics

    CERN Document Server

    Diggle, Peter J

    2007-01-01

    Model-based geostatistics refers to the application of general statistical principles of modeling and inference to geostatistical problems. This volume provides a treatment of model-based geostatistics and emphasizes on statistical methods and applications. It also features analyses of datasets from a range of scientific contexts.

  17. Hyperspectral Unmixing Overview: Geometrical, Statistical, and Sparse Regression-Based Approaches

    CERN Document Server

    Bioucas-Dias, José M; Dobigeon, Nicolas; Parente, Mario; Du, Qian; Gader, Paul

    2012-01-01

    Imaging spectrometers measure electromagnetic energy scattered in their instantaneous field view in hundreds or thousands of spectral channels with higher spectral resolution than multispectral cameras. Imaging spectrometers are therefore often referred to as hyperspectral cameras (HSCs). Higher spectral resolution enables material identification via spectroscopic analysis, which facilitates countless applications that require identifying materials in scenarios unsuitable for classical spectroscopic analysis. Due to low spatial resolution of HSCs, microscopic material mixing, and multiple scattering, spectra measured by HSCs are mixtures of spectra of materials in a scene. Thus, accurate estimation requires unmixing. Pixels are assumed to be mixtures of a few materials, called endmembers. Unmixing involves estimating all or some of: the number of endmembers, their spectral signatures, and their abundances at each pixel. Unmixing is a challenging, ill-posed inverse problem because of model inaccuracies, observ...

  18. Haptics-based dynamic implicit solid modeling.

    Science.gov (United States)

    Hua, Jing; Qin, Hong

    2004-01-01

    This paper systematically presents a novel, interactive solid modeling framework, Haptics-based Dynamic Implicit Solid Modeling, which is founded upon volumetric implicit functions and powerful physics-based modeling. In particular, we augment our modeling framework with a haptic mechanism in order to take advantage of additional realism associated with a 3D haptic interface. Our dynamic implicit solids are semi-algebraic sets of volumetric implicit functions and are governed by the principles of dynamics, hence responding to sculpting forces in a natural and predictable manner. In order to directly manipulate existing volumetric data sets as well as point clouds, we develop a hierarchical fitting algorithm to reconstruct and represent discrete data sets using our continuous implicit functions, which permit users to further design and edit those existing 3D models in real-time using a large variety of haptic and geometric toolkits, and visualize their interactive deformation at arbitrary resolution. The additional geometric and physical constraints afford more sophisticated control of the dynamic implicit solids. The versatility of our dynamic implicit modeling enables the user to easily modify both the geometry and the topology of modeled objects, while the inherent physical properties can offer an intuitive haptic interface for direct manipulation with force feedback. PMID:15794139

  19. Man-made Object Detection Based on Texture Clustering and Geometric Structure Feature Extracting

    Directory of Open Access Journals (Sweden)

    Fei Cai

    2011-03-01

    Full Text Available Automatic aerial image interpretation is one of new rising high-tech application fields, and it’s proverbially applied in the military domain. Based on human visual attention mechanism and texture visual perception, this paper proposes a new approach for man-made object detection and marking by extracting texture and geometry structure features. After clustering the texture feature to realize effective image segmentation, geometry structure feature is obtained to achieve final detection and marking. Thus a man-made object detection methodology is designed, by which typical man-made objects in complex natural background, including airplanes, tanks and vehicles can be detected. The experiments sustain that the proposed method is effective and rational.

  20. Quartic oscillator potential in the γ-rigid regime of the collective geometrical model

    International Nuclear Information System (INIS)

    A prolate γ-rigid version of the Bohr-Mottelson Hamiltonian with a quartic anharmonic oscillator potential in β collective shape variable is used to describe the spectra for a variety of vibrational-like nuclei. Speculating the exact separation between the two Euler angles and the β variable, one arrives at a differential Schroedinger equation with a quartic anharmonic oscillator potential and a centrifugal-like barrier. The corresponding eigenvalue is approximated by an analytical formula depending only on a single parameter up to an overall scaling factor. The applicability of the model is discussed in connection to the existence interval of the free parameter, which is limited by the accuracy of the approximation, and by comparison with the predictions of the related X(3) and X(3)-β 2 models. The model is applied to qualitatively describe the spectra for nine nuclei which exhibit near-vibrational features. (orig.)

  1. Clifford algebras geometric modelling and chain geometries with application in kinematics

    CERN Document Server

    Klawitter, Daniel

    2015-01-01

    After revising known representations of the group of Euclidean displacements Daniel Klawitter gives a comprehensive introduction into Clifford algebras. The Clifford algebra calculus is used to construct new models that allow descriptions of the group of projective transformations and inversions with respect to hyperquadrics. Afterwards, chain geometries over Clifford algebras and their subchain geometries are examined. The author applies this theory and the developed methods to the homogeneous Clifford algebra model corresponding to Euclidean geometry. Moreover, kinematic mappings for special Cayley-Klein geometries are developed. These mappings allow a description of existing kinematic mappings in a unifying framework.  Contents Models and representations of classical groups Clifford algebras, chain geometries over Clifford algebras Kinematic mappings for Pin and Spin groups Cayley-Klein geometries Target Groups Researchers and students in the field of mathematics, physics, and mechanical engineering About...

  2. Examining the Relationship between Forces During Stereolithography 3D Printing and Geometric Parameters of the Model

    Directory of Open Access Journals (Sweden)

    Kovalenko Iaroslav

    2016-01-01

    Full Text Available In the case of stereolithography 3D printing technology, detaching formed model from the tank with photopolymer is a lengthy process. Forces, which appear during removing of solid photopolymer layerformed in stereolithography 3D DLP printer, can destroy the built model. In this article the detachment force is measured, obtained results arestatistically analyzed and relation between detach force, area of produced layer and thickness of the layer are verified. Linear dependence between detach force and built area is determined. On the other hand, relation between detach force and thickness of the layer is not confirmed.

  3. Simulations of geometrically pinched argon plasmas using an extended one-dimensional model

    NARCIS (Netherlands)

    K.T.A.L. Burm,; W. J. Goedheer,; D.C. Schram,

    2001-01-01

    The subject of this paper is the modelling of a wall-stabilized cylinder symmetric cascaded are which is to be used as a high-density plasma source. To enhance the ion flux emerging from cascaded are argon plasmas the confining wall can be changed into a nozzle geometry. Such pinched geometries incr

  4. A quasi-Bohmian approach for a homogeneous spherical solid body based on its geometric structure

    Energy Technology Data Exchange (ETDEWEB)

    Koupaei, Jalaledin Yousefi [Department of Physics, Shahid Beheshti University, G. C., Evin, Tehran 19839 (Iran, Islamic Republic of); Institutes for Theoretical Physics and Mathematics (IPM), Tehran (Iran, Islamic Republic of); Golshani, Mehdi [Institutes for Theoretical Physics and Mathematics (IPM), Tehran (Iran, Islamic Republic of); Department of Physics, Sharif University of Technology, Tehran (Iran, Islamic Republic of)

    2013-12-15

    In this paper we express the space of rotation as a Riemannian space and try to generalize the classical equations of motion of a homogeneous spherical solid body in the domain of quantum mechanics. This is done within Bohm's view of quantum mechanics, but we do not use the Schrödinger equation. Instead, we assume that in addition to the classical potential there is an extra potential and try to obtain it. In doing this, we start from a classical picture based on Hamilton-Jacobi formalism and statistical mechanics but we use an interpretation which is different from the classical one. Then, we introduce a proper action and extremize it. This procedure gives us a mathematical identity for the extra potential that limits its form. The classical mechanics is a trivial solution of this method. In the simplest cases where the extra potential is not a constant, a mathematical identity determines it uniquely. In fact the first nontrivial potential, apart from some constant coefficients which are determined by experiment, is the usual Bohmian quantum potential.

  5. PEP-X: An Ultimate Storage Ring Based on Fourth-Order Geometric Achromats

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Yunhai; Bane, Karl; Hettel, Robert; Nosochkov, Yuri; Wang, Min-Huey; /SLAC

    2012-04-06

    We have designed an 'ultimate' storage ring for the PEP-X light source that achieves the diffraction limited emittances (at 1.5 {angstrom}) of 12 pm-rad in both horizontal and vertical planes with a 4.5-GeV beam. These emittances include the contribution of intrabeam scattering at a nominal current of 200 mA in 3300 bunches. This quality beam in conjunction with a conventional 4-m undulator in a straight section can generate synchrotron radiation having a spectral brightness above 10{sup 22} [photons/s/mm{sup 2}/mrad{sup 2}/0.1% BW] at a 10 keV photon energy. The high coherence at the diffraction limit makes PEP-X competitive with 4th generation light sources based on an energy recovery linac. In addition, the beam lifetime is several hours and the dynamic aperture is large enough to allow off-axis injection. The alignment and stability tolerances, though challenging, are achievable. A ring with all these properties is only possible because of several major advances in mitigating the effects of nonlinear resonances.

  6. A geometric approach to modeling microstructurally small fatigue crack formation: III. Development of a semi-empirical model for nucleation

    International Nuclear Information System (INIS)

    It has been observed during fatigue cracking of AA 7075-T651 that a small percentage of Al7Cu2Fe particles crack during manufacturing or very early in their life. Some of the cracked particles eventually nucleate cracks into the surrounding microstructure, and among these the number of cycles required for nucleation varies widely. It is important to comprehend the mechanics underpinning the observed variation so that the subsequent propagation stage can be accurately modeled. To this end, finite element models of replicated grain and particle geometry are used to compute mechanical fields near monitored cracked particles using an elastic–viscoplastic crystal plasticity model that captures the effect of the orientation of the grains near each monitored particle. Nonlocal, slip-based metrics are used to study the localization and cyclic accumulation of slip near the cracked particles providing mechanics-based insight into the actuation of the nucleation event. A high slip localization and cyclic accumulation rate are found to be a necessary, but not sufficient, condition for nucleation from cracked particles. A sufficient local driving stress must also be present, which is strongly dependent on the local microstructure and accumulated slip. Furthermore, the simulation results elucidate a quantitative relationship between the slip accumulated during fatigue loading and a consequential reduction of the critical local driving stress for nucleation, providing a physical basis for the fatigue damage concept. The observed nucleation direction is orthogonal to the computed local maximum tangential stress direction, as expected for this alloy. The main result is a semi-empirical model for the number of cycles required for nucleation, which is dependent on the maximum tangential stress and cyclic slip-accumulation rate near a cracked particle

  7. Geometric phase effects in low-energy dynamics near conical intersections: A study of the multidimensional linear vibronic coupling model

    Energy Technology Data Exchange (ETDEWEB)

    Joubert-Doriol, Loïc; Ryabinkin, Ilya G.; Izmaylov, Artur F. [Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, Ontario M1C 1A4 (Canada); Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6 (Canada)

    2013-12-21

    In molecular systems containing conical intersections (CIs), a nontrivial geometric phase (GP) appears in the nuclear and electronic wave functions in the adiabatic representation. We study GP effects in nuclear dynamics of an N-dimensional linear vibronic coupling (LVC) model. The main impact of GP on low-energy nuclear dynamics is reduction of population transfer between the local minima of the LVC lower energy surface. For the LVC model, we proposed an isometric coordinate transformation that confines non-adiabatic effects within a two-dimensional subsystem interacting with an N − 2 dimensional environment. Since environmental modes do not couple electronic states, all GP effects originate from nuclear dynamics within the subsystem. We explored when the GP affects nuclear dynamics of the isolated subsystem, and how the subsystem-environment interaction can interfere with GP effects. Comparing quantum dynamics with and without GP allowed us to devise simple rules to determine significance of the GP for nuclear dynamics in this model.

  8. A model-independent dark energy reconstruction scheme using the geometrical form of the luminosity-distance relation

    CERN Document Server

    Fay, S; Fay, Stephane; Tavakol, Reza

    2006-01-01

    We put forward a new model-independent reconstruction scheme for dark energy which utilises the expected geometrical features of the luminosity-distance relation. Using the recently released supernovae data by the Supernova Legacy Survey together with a phase space representation, we show that the reconstructed luminosity-distance curves best fitting the data favour a slower rate of expansion than the $\\Lambda CDM$ model, with a varying dark energy density which goes through a transition from an accelerating to a decelerating phase at a redshift of around 0.45. However, the $\\Lambda CDM$ model cannot be ruled out at 95.4% significance level, in agreement with other recent reconstructions. Interpreting the dark energy as a minimally coupled scalar field we find that the reconstructed scalar field evolution best fitting the data corresponds to an increasing kinetic energy and a decreasing potential energy as the redshift increases. The important advantage of this scheme is that it does not assume explicit ansat...

  9. A geometrically exact beam element based on the absolute nodal coordinate formulation

    International Nuclear Information System (INIS)

    In this study, Reissner's classical nonlinear rod formulation, as implemented by Simo and Vu-Quoc by means of the large rotation vector approach, is implemented into the framework of the absolute nodal coordinate formulation. The implementation is accomplished in the planar case accounting for coupled axial, bending, and shear deformation. By employing the virtual work of elastic forces similarly to Simo and Vu-Quoc in the absolute nodal coordinate formulation, the numerical results of the formulation are identical to those of the large rotation vector formulation. It is noteworthy, however, that the material definition in the absolute nodal coordinate formulation can differ from the material definition used in Reissner's beam formulation. Based on an analytical eigenvalue analysis, it turns out that the high frequencies of cross section deformation modes in the absolute nodal coordinate formulation are only slightly higher than frequencies of common shear modes, which are present in the classical large rotation vector formulation of Simo and Vu-Quoc, as well. Thus, previous claims that the absolute nodal coordinate formulation is inefficient or would lead to ill-conditioned finite element matrices, as compared to classical approaches, could be refuted. In the introduced beam element, locking is prevented by means of reduced integration of certain parts of the elastic forces. Several classical large deformation static and dynamic examples as well as an eigenvalue analysis document the equivalence of classical nonlinear rod theories and the absolute nodal coordinate formulation for the case of appropriate material definitions. The results also agree highly with those computed in commercial finite element codes

  10. Magnetization plateaus of frustrated Kondo necklace model. Competition between quantum fluctuation and geometrical frustration

    International Nuclear Information System (INIS)

    The magnetization plateaus of frustrated Kondo necklace model have been studied with use of the bosonization technique and level spectroscopy method. It is shown that the model may show three phases (dimer plateau, Neel plateau and Tomonaga-Luttinger liquid phases) due to competitions among Ising anisotropy Δ, the nearest and next nearest neighbor exchange interactions J1, J2. It is shown from bosonization technique that quantum transition between the dimer and Neel plateaus is Gaussian type, while the transition from one of these plateau phases to Tomonaga-Luttinger phase is Brezinskii-Kosterlitz-Thouless type. The phase diagram is constructed on the Δ-J2/J1 plane with use of level spectroscopy method, under the condition that the system has a half of the saturation magnetization. (author)

  11. A three-part geometric model to predict the radar backscatter from wheat, corn, and sorghum

    Science.gov (United States)

    Ulaby, F. T. (Principal Investigator); Eger, G. W., III; Kanemasu, E. T.

    1982-01-01

    A model to predict the radar backscattering coefficient from crops must include the geometry of the canopy. Radar and ground-truth data taken on wheat in 1979 indicate that the model must include contributions from the leaves, from the wheat head, and from the soil moisture. For sorghum and corn, radar and ground-truth data obtained in 1979 and 1980 support the necessity of a soil moisture term and a leaf water term. The Leaf Area Index (LAI) is an appropriate input for the leaf contribution to the radar response for wheat and sorghum, however the LAI generates less accurate values for the backscattering coefficient for corn. Also, the data for corn and sorghum illustrate the importance of the water contained in the stalks in estimating the radar response.

  12. Linking biogeochemistry to hydro-geometrical variability in tidal estuaries: a generic modeling approach

    Science.gov (United States)

    Volta, Chiara; Gildas Laruelle, Goulven; Arndt, Sandra; Regnier, Pierre

    2016-03-01

    This study applies the Carbon-Generic Estuary Model (C-GEM) modeling platform to simulate the estuarine biogeochemical dynamics - in particular the air-water CO2 exchange - in three idealized tidal estuaries characterized by increasing riverine influence, from a so-called "marine estuary" to a "riverine estuary". An intermediate case called "mixed estuary" is also considered. C-GEM uses a generic biogeochemical reaction network and a unique set of model parameters extracted from a comprehensive literature survey to perform steady-state simulations representing average conditions for temperate estuaries worldwide. Climate and boundary conditions are extracted from published global databases (e.g., World Ocean Atlas, GLORICH) and catchment model outputs (GlobalNEWS2). The whole-system biogeochemical indicators net ecosystem metabolism (NEM), C and N filtering capacities (FCTC and FCTN, respectively) and CO2 gas exchanges (FCO2) are calculated across the three idealized systems and are related to their main hydrodynamic and transport characteristics. A sensitivity analysis, which propagates the parameter uncertainties, is also carried out, followed by projections of changes in the biogeochemical indicators for the year 2050. Results show that the average C filtering capacities for baseline conditions are 40, 30 and 22 % for the marine, mixed and riverine estuary, respectively, while N filtering capacities, calculated in a similar fashion, range from 22 % for the marine estuary to 18 and 15 % for the mixed and the riverine estuaries. Sensitivity analysis performed by varying the rate constants for aerobic degradation, denitrification and nitrification over the range of values reported in the literature significantly widens these ranges for both C and N. Simulations for the year 2050 suggest that all estuaries will remain largely heterotrophic, although a slight improvement of the estuarine trophic status is predicted. In addition, our results suggest that, while the

  13. Magnetic studies on a new S = 1/2 vanadium based (V4+) geometrically frustrated system (BaV3O8)

    International Nuclear Information System (INIS)

    In this article we report the magnetic properties of a (S=1/2) vanadium based (V4+) geometrically frustrated system BaV3O8. In this system the V4+ ions are in edge-shared triangular network. The susceptibility measurement shows a broad maximum around 30K indicative to the short-range interaction between the V4+ ions followed by a sharp maximum at 5.8K indicative of long range ordering possibly due to the inter-planer interaction between the V4+ ions. The frustration factor ((θCW/ TN)>5) suggests that geometric frustration plays a vital role in this system. (author)

  14. Brief Announcement: Decentralized Construction of Multicast Trees Embedded into P2P Overlay Networks based on Virtual Geometric Coordinates

    CERN Document Server

    Andreica, Mugurel Ionut; Sambotin, Ana-Delia; Tapus, Nicolae; 10.1145/1835698.1835766

    2010-01-01

    In this paper we consider the problem of efficiently constructing in a fully distributed manner multicast trees which are embedded into P2P overlays using virtual geometric node coordinates. We consider two objectives: to minimize the number of messages required for constructing a multicast tree by using the geometric properties of the P2P overlay, and to construct stable multicast trees when the lifetime durations of the peers are known.

  15. Fish recognition based on the combination between robust feature selection, image segmentation and geometrical parameter techniques using Artificial Neural Network and Decision Tree

    CERN Document Server

    Alsmadi, Mutasem Khalil Sari; Noah, Shahrul Azman; Almarashdah, Ibrahim

    2009-01-01

    We presents in this paper a novel fish classification methodology based on a combination between robust feature selection, image segmentation and geometrical parameter techniques using Artificial Neural Network and Decision Tree. Unlike existing works for fish classification, which propose descriptors and do not analyze their individual impacts in the whole classification task and do not make the combination between the feature selection, image segmentation and geometrical parameter, we propose a general set of features extraction using robust feature selection, image segmentation and geometrical parameter and their correspondent weights that should be used as a priori information by the classifier. In this sense, instead of studying techniques for improving the classifiers structure itself, we consider it as a black box and focus our research in the determination of which input information must bring a robust fish discrimination.The main contribution of this paper is enhancement recognize and classify fishes...

  16. A geometric approach to tree shape statistics

    OpenAIRE

    Matsen, Frederick A.

    2005-01-01

    This article presents a new way to understand the descriptive ability of tree shape statistics. Where before tree shape statistics were chosen by their ability to distinguish between macroevolutionary models, the ``resolution'' presented in this paper quantifies the ability of a statistic to differentiate between similar and different trees. We term this a ``geometric'' approach to differentiate it from the model-based approach previously explored. A distinct advantage of this perspective is ...

  17. Stochastic geometrical model and Monte Carlo optimization methods for building reconstruction from InSAR data

    Science.gov (United States)

    Zhang, Yue; Sun, Xian; Thiele, Antje; Hinz, Stefan

    2015-10-01

    Synthetic aperture radar (SAR) systems, such as TanDEM-X, TerraSAR-X and Cosmo-SkyMed, acquire imagery with high spatial resolution (HR), making it possible to observe objects in urban areas with high detail. In this paper, we propose a new top-down framework for three-dimensional (3D) building reconstruction from HR interferometric SAR (InSAR) data. Unlike most methods proposed before, we adopt a generative model and utilize the reconstruction process by maximizing a posteriori estimation (MAP) through Monte Carlo methods. The reason for this strategy refers to the fact that the noisiness of SAR images calls for a thorough prior model to better cope with the inherent amplitude and phase fluctuations. In the reconstruction process, according to the radar configuration and the building geometry, a 3D building hypothesis is mapped to the SAR image plane and decomposed to feature regions such as layover, corner line, and shadow. Then, the statistical properties of intensity, interferometric phase and coherence of each region are explored respectively, and are included as region terms. Roofs are not directly considered as they are mixed with wall into layover area in most cases. When estimating the similarity between the building hypothesis and the real data, the prior, the region term, together with the edge term related to the contours of layover and corner line, are taken into consideration. In the optimization step, in order to achieve convergent reconstruction outputs and get rid of local extrema, special transition kernels are designed. The proposed framework is evaluated on the TanDEM-X dataset and performs well for buildings reconstruction.

  18. Transformation of Lamellar Structures in Equal Channel Angular Pressing: Geometric Model and Application to Nickel Aluminum Bronze

    Science.gov (United States)

    Barr, Cameron J.; McDonald, Daniel T.; Xia, Kenong

    2015-09-01

    Nickel aluminum bronze (NAB) with a duplex structure was subjected to equal channel angular pressing (ECAP). Samples were pressed for up to four passes at 673 K (400 °C) using routes A, BA, BC, and C, respectively, and the evolution of the microstructures was characterized. A detailed geometric model was developed to enable systematic and quantitative analysis of the transformation of the lamellar structure during ECAP. Depending on their orientations before each ECAP pass, the lamellae were either stretched, leading to fragmentation, or compressed, resulting in buckling and spheroidisation at locations of high curvature. Thanks to the continuous rotation of lamellae into the stretching orientations in route A and the non-plane strain deformation in the two B routes, they are demonstrated to be the most effective in breaking down the lamellar structure. In contrast, partial restoration due to redundant strain in route C makes it least efficient. The model applies generally to materials with a duplex structure, such as NAB and low and medium carbon steels, consisting of a hard and brittle lamellar phase and a softer and ductile matrix phase.

  19. "Improved Geometric Network Model" (IGNM): a novel approach for deriving Connectivity Graphs for Indoor Navigation

    Science.gov (United States)

    Mortari, F.; Zlatanova, S.; Liu, L.; Clementini, E.

    2014-04-01

    Over the past few years Personal Navigation Systems have become an established tool for route planning, but they are mainly designed for outdoor environments. Indoor navigation is still a challenging research area for several reasons: positioning is not very accurate, users can freely move between the interior boundaries of buildings, path network construction process may not be easy and straightforward due to complexity of indoor space configurations. Therefore the creation of a good network is essential for deriving overall connectivity of a building and for representing position of objects within the environment. This paper reviews current approaches to automatic derivation of route graphs for indoor navigation and discusses some of their limitations. Then, it introduces a novel algorithmic strategy for extracting a 3D connectivity graph for indoor navigation based on 2D floor plans.

  20. Double transmission-mediums based geometric phase analysis for determining the two surface profiles of transparent object

    Science.gov (United States)

    Liu, Shuli; Liu, Zhanwei

    2016-05-01

    The accurate measurement for the surface profiles of transparent object is of significance for quality control in optical devices and precision instruments. Here, a double transmission-mediums based geometric phase analysis method has been developed to evaluate both the upper and lower surface profiles of transparent object. To do this, the tested transparent object is placed above a preprinted lattice pattern. When viewed from above with a CCD camera, any slope variations of the surfaces will lead to distortions of the transmission-lattice patterns. And when changing one side of object's contact medium, the lattice virtual image with modulated phase is distorted once again. Combined with the derived relationship between phase variations of transmission-lattice patterns and out-of-plane heights of two surfaces, the double-sided surface profiles of transparent object can be reconstructed successfully. With this, the technique, which is verified experimentally, is demonstrated to be a feasible and reliable method. The advantage of this method is that it simplifies the setup and allows a fast estimation of the geometry of a transparent specimen. The double-sided profiles can be decoupled easily according to the big difference of refractive indexes between contact mediums. And the calculation accuracy can be guaranteed by the weighted average from four directions.