Analytical design of conformally invisible cloaks for arbitrarily shaped objects
NASA Astrophysics Data System (ADS)
Jiang, Wei Xiang; Chin, Jessie Yao; Li, Zhuo; Cheng, Qiang; Liu, Ruopeng; Cui, Tie Jun
2008-06-01
To design conformally invisible cloaks for arbitrarily shaped objects, we use the nonuniform rational B -spline (NURBS) to represent the geometrical modeling of the arbitrary object. Based on the method of optical transformation, analytical formulas of the permittivity and permeability tensors are proposed for arbitrarily shaped invisible cloaks. Such formulas can be easily implemented in the design of arbitrary cloaks. Full-wave simulations are given for heart-shaped invisible cloaks and perfectly electrical conducting (PEC) objects, in which we observe that the power-flow lines of incoming electromagnetic waves will be bent smoothly in the cloaks and will return to their original propagation directions after propagating around the object. We also show that the scattered field from the PEC object coated with the invisible cloak is much smaller than that from the PEC core. The application of NURBS in the design of arbitrary cloaks shows transformation optics to be a very general tool to interface with commercial softwares like 3D STUDIOMAX and MAYA.
Scattering of arbitrarily shaped beam by a chiral object
NASA Astrophysics Data System (ADS)
Wang, Wenjie; Sun, Yufa; Zhang, Huayong
2017-02-01
An exact semi-analytical solution to the arbitrarily shaped beam scattering by a chiral object is proposed through expanding the scattered and internal fields in terms of appropriate spherical vector wave functions. By using the boundary conditions and the method of moments technique, the unknown expansion coefficients are determined. For incidence of a Gaussian beam, zero-order Bessel beam and Hertzian electric dipole radiation, numerical results of the normalized differential scattering cross section are given to a chiral spheroid and a chiral circular cylinder of finite length, and the scattering characteristics are discussed concisely.
A low memory zerotree coding for arbitrarily shaped objects.
Su, Chorng-Yann; Wu, Bing-Fei
2003-01-01
The set partitioning in hierarchical trees (SPIHT) algorithm is a computationally simple and efficient zerotree coding technique for image compression. However, the high working memory requirement is its main drawback for hardware realization. We present a low memory zerotree coder (LMZC), which requires much less working memory than SPIHT. The LMZC coding algorithm abandons the use of lists, defines a different tree structure, and merges the sorting pass and the refinement pass together. The main techniques of LMZC are the recursive programming and a top-bit scheme (TBS). In TBS, the top bits of transformed coefficients are used to store the coding status of coefficients instead of the lists used in SPIHT. In order to achieve high coding efficiency, shape-adaptive discrete wavelet transforms are used to transformation arbitrarily shaped objects. A compact emplacement of the transformed coefficients is also proposed to further reduce working memory. The LMZC carefully treats "don't care" nodes in the wavelet tree and does not use bits to code such nodes. Comparison of LMZC with SPIHT shows that for coding a 768 /spl times/ 512 color image, LMZC saves at least 5.3 MBytes of memory but only increases a little execution time and reduces minor peak signal-to noise ratio (PSNR) values, thereby making it highly promising for some memory limited applications.
NASA Astrophysics Data System (ADS)
Kim, Kyoohyun; Park, Yongkeun
2017-05-01
Optical trapping can manipulate the three-dimensional (3D) motion of spherical particles based on the simple prediction of optical forces and the responding motion of samples. However, controlling the 3D behaviour of non-spherical particles with arbitrary orientations is extremely challenging, due to experimental difficulties and extensive computations. Here, we achieve the real-time optical control of arbitrarily shaped particles by combining the wavefront shaping of a trapping beam and measurements of the 3D refractive index distribution of samples. Engineering the 3D light field distribution of a trapping beam based on the measured 3D refractive index map of samples generates a light mould, which can manipulate colloidal and biological samples with arbitrary orientations and/or shapes. The present method provides stable control of the orientation and assembly of arbitrarily shaped particles without knowing a priori information about the sample geometry. The proposed method can be directly applied in biophotonics and soft matter physics.
NASA Astrophysics Data System (ADS)
Webb, David Bedford
The solution of electromagnetic scattering by objects located in planar, multilayered media has long been the subject of active research. For layered-media integral equation solutions via the Method of Moments (MoM), the O(N^2) matrix fill is often prohibitively expensive, even for problems of moderate size. For spatial-domain formulations, this is due to the presence of the Sommerfeld integrals required for obtaining the Green's functions in spatial form. These integrals are completely avoided through use of the complex-image method, which represents the spatial -domain Green's functions in closed form. However, this method is not without limitations, most notably a finite region of validity and an undesirable sensitivity to the choice of requisite parameters. This thesis focuses on methods for overcoming these limitations, to allow robust implementation of the method within the framework of an automated, general-purpose analysis program, applicable to the solution of scattering from arbitrarily shaped objects residing in any number of dielectric layers. Evaluations of several possible improvements to the original complex -image method are presented. A new approach is also presented for representing the angular-dependent Green's function terms that are required when both horizontal and vertical electric currents are present. The complex-image method is applied in this work to the MoM solution of the mixed-potential form of the electric field integral equation (MPIE). Several numerical results are presented for planar and nonplanar objects, including a microstrip patch antenna, wire dipole antennas penetrating dielectric half-spaces, and a microstrip air bridge. These results are compared with measurements or the results from other programs whenever possible. A brief discussion of scattering parameter extraction is also covered, with a comparison of the Prony and Generalized Pencil-of-Functions (GPOF) methods.
Kim, Kyoohyun; Park, YongKeun
2017-01-01
Optical trapping can manipulate the three-dimensional (3D) motion of spherical particles based on the simple prediction of optical forces and the responding motion of samples. However, controlling the 3D behaviour of non-spherical particles with arbitrary orientations is extremely challenging, due to experimental difficulties and extensive computations. Here, we achieve the real-time optical control of arbitrarily shaped particles by combining the wavefront shaping of a trapping beam and measurements of the 3D refractive index distribution of samples. Engineering the 3D light field distribution of a trapping beam based on the measured 3D refractive index map of samples generates a light mould, which can manipulate colloidal and biological samples with arbitrary orientations and/or shapes. The present method provides stable control of the orientation and assembly of arbitrarily shaped particles without knowing a priori information about the sample geometry. The proposed method can be directly applied in biophotonics and soft matter physics. PMID:28530232
NASA Astrophysics Data System (ADS)
Bittar, Eric; Lavallee, Stephane; Szeliski, Richard
1993-08-01
This paper presents a method to register overlapping 3-D surfaces which we use to reconstruct entire three-dimensional objects from sets of views. We use a range imaging sensor to digitize the object in several positions. Each pair of overlapping images is then registered using the algorithm developed in this paper. Rather than extracting and matching features, we match the complete surface, which we represent using a collection of points. This enables us to reconstruct smooth free-form objects which may lack sufficient features. Our algorithm is an extension of an algorithm we previously developed to register 3-D surfaces. This algorithm first creates an octree-spline from one set of points to quickly compute point to surface distances. It then uses an iterative nonlinear least squares minimization technique to minimize the sum of squared distances from the data point set to the octree point set. In this paper, we replace the squared distance with a function of the distance, which allows the elimination of points that are not in the shared region between the two sets. Once the object has been reconstructed by merging all the views, a continuous surface model is created from the set of points. This method has been successfully used on the limbs of a dummy and on a human head.
Wu, Sean F; Zhao, Xiang
2002-07-01
A combined Helmholtz equation-least squares (CHELS) method is developed for reconstructing acoustic radiation from an arbitrary object. This method combines the advantages of both the HELS method and the Helmholtz integral theory based near-field acoustic holography (NAH). As such it allows for reconstruction of the acoustic field radiated from an arbitrary object with relatively few measurements, thus significantly enhancing the reconstruction efficiency. The first step in the CHELS method is to establish the HELS formulations based on a finite number of acoustic pressure measurements taken on or beyond a hypothetical spherical surface that encloses the object under consideration. Next enough field acoustic pressures are generated using the HELS formulations and taken as the input to the Helmholtz integral formulations implemented through the boundary element method (BEM). The acoustic pressure and normal component of the velocity at the discretized nodes on the surface are then determined by solving two matrix equations using singular value decomposition (SVD) and regularization techniques. Also presented are in-depth analyses of the advantages and limitations of the CHELS method. Examples of reconstructing acoustic radiation from separable and nonseparable surfaces are demonstrated.
NASA Astrophysics Data System (ADS)
Wu, Sean F.; Zhao, Xiang
2002-07-01
A combined Helmholtz equation-least squares (CHELS) method is developed for reconstructing acoustic radiation from an arbitrary object. This method combines the advantages of both the HELS method and the Helmholtz integral theory based near-field acoustic holography (NAH). As such it allows for reconstruction of the acoustic field radiated from an arbitrary object with relatively few measurements, thus significantly enhancing the reconstruction efficiency. The first step in the CHELS method is to establish the HELS formulations based on a finite number of acoustic pressure measurements taken on or beyond a hypothetical spherical surface that encloses the object under consideration. Next enough field acoustic pressures are generated using the HELS formulations and taken as the input to the Helmholtz integral formulations implemented through the boundary element method (BEM). The acoustic pressure and normal component of the velocity at the discretized nodes on the surface are then determined by solving two matrix equations using singular value decomposition (SVD) and regularization techniques. Also presented are in-depth analyses of the advantages and limitations of the CHELS method. Examples of reconstructing acoustic radiation from separable and nonseparable surfaces are demonstrated. copyright 2002 Acoustical Society of America.
Scattering from arbitrarily shaped microstrip patch antennas
NASA Technical Reports Server (NTRS)
Shively, David G.; Deshpande, Manohar D.; Cockrell, Capers R.
1992-01-01
The scattering properties of arbitrarily shaped microstrip patch antennas are examined. The electric field integral equation for a current element on a grounded dielectric slab is developed for a rectangular geometry based on Galerkin's technique with subdomain rooftop basis functions. A shape function is introduced that allows a rectangular grid approximation to the arbitrarily shaped patch. The incident field on the patch is expressed as a function of incidence angle theta(i), phi(i). The resulting system of equations is then solved for the unknown current modes on the patch, and the electromagnetic scattering is calculated for a given angle. Comparisons are made with other calculated results as well as with measurements.
Input impedance of arbitrarily shaped microstrip antennas
NASA Astrophysics Data System (ADS)
Pichon, P.; Mosig, J.; Papiernik, A.
1988-09-01
The paper deals with the analysis of arbitrarily shaped microstrip antennas. A powerful and flexible technique is obtained by combining a mixed potential integral equation, successfully used for rectangular patches, with a method of moments, using a division of the patch into triangular cells and overlapping basis functions, defined over cell couples. The resulting computer algorithm is validated by comparing its predictions with the measurements obtained from an equilateral triangular patch.
Fu Jianwei; Yang Xiaoquan; Wang Kan; Luo Qingming; Gong Hui
2011-12-15
Purpose: A combined system of fluorescence molecular tomography and microcomputed tomography (FMT and mCT) can provide molecular and anatomical information of small animals in a single study with intrinsically coregistered images. The anatomical information provided by the mCT subsystem is commonly used as a reference to locate the fluorophore distribution or as a priori structural information to improve the performance of FMT. Therefore, the transformation between the coordinate systems of the subsystem needs to be determined in advanced. Methods: A cocalibration method for the combined system of FMT and mCT is proposed. First, linear models are adopted to describe the galvano mirrors and the charge-coupled device (CCD) camera in the FMT subsystem. Second, the position and orientation of the galvano mirrors are determined with the input voltages of the galvano mirrors and the markers, whose positions are predetermined. The position, orientation and normalized pixel size of the CCD camera are obtained by analysing the projections of a point-like marker at different positions. Finally, the orientation and position of sources and the corresponding relationship between the detectors and their projections on the image plane are predicted. Because the positions of the markers are acquired with mCT, the registration of the FMT and mCT could be realized by direct image fusion. Results: The accuracy and consistency of this method in the presence of noise is evaluated by computer simulation. Next, a practical implementation for an experimental FMT and mCT system is carried out and validated. The maximum prediction error of the source positions on the surface of a cylindrical phantom is within 0.375 mm and that of the projections of a point-like marker is within 0.629 pixel. Finally, imaging experiments of the fluorophore distribution in a cylindrical phantom and a phantom with a complex shape demonstrate the feasibility of the proposed method. Conclusions: This method is
NASA Astrophysics Data System (ADS)
Ruan, Zhichao; Fan, Shanhui
2012-04-01
We develop a temporal coupled-mode theory to describe the interaction of plane wave with an individual scatterer having an arbitrary shape. The theory involves the expansion of the fields on cylindrical or spherical wave basis for the two-dimensional and three-dimensional cases, respectively, and describes the scattering process in terms of a background scattering matrix and the resonant radiation coefficients into different cylindrical or spherical wave channels. This theory provides a general formula for the scattering and absorption cross sections. We show that for a subwavelength asymmetric scatterer with a single resonance, the scattering and absorption cross sections can exceed the single-resonance limit for some specific incident angles of illumination, but the sum of these cross sections over all angles has an upper limit. We validate the theory with numerical simulations of a metallic scatterer that does not have any rotation symmetry.
Arbitrarily shaped scatterer by moment method
NASA Astrophysics Data System (ADS)
Shu, Yongze; Ma, Feng
1988-12-01
The calculation of radar cross section (RCS) for an arbitrarily shaped and perfectly conducting scatterer with small electric size has been studied by moment method. The starting point of this paper is the reaction integral equation (RIE). Polygonal plates are used to construct models of realistic structures and to segment every plate into modes automatically. Overlap modes can be obtained between the connecting intersecting plates. The piecewise-sinusoidal modes have been chosen as expansion and testing functions. From RIE, the matrix equation IZ = V can be derived. The scattering field and RCS of the scatterer can be obtained. The method has advantages of simplicity and flexibility of input, versatility, and accuracy. The calculating results of RCS for a few scatterers with different shapes, including a realistic rocket, have been given. The results are in good agreement with those published abroad.
Shape-adaptive discrete wavelet transform for coding arbitrarily shaped texture
NASA Astrophysics Data System (ADS)
Li, Shipeng; Li, Weiping
1997-01-01
This paper presents a shape adaptive discrete wavelet transform (SA-DWT) scheme for coding arbitrarily shaped texture. The proposed SA-DWT can be used for object-oriented image coding. The number of coefficients after SA-DWT is identical to the number of pels contained in the arbitrarily shaped image objects. The locality property of wavelet transform and self-similarity among subbands are well preserved throughout this process.For a rectangular region, the SA-DWT is identical to a standard wavelet transform. With SA-DWT, conventional wavelet based coding schemes can be readily extended to the coding of arbitrarily shaped objects. The proposed shape adaptive wavelet transform is not unitary but the small energy increase is restricted at the boundary of objects in subbands. Two approaches of using the SA-DWT algorithm for object-oriented image and video coding are presented. One is to combine scalar SA-DWT with embedded zerotree wavelet (EZW) coding technique, the other is an extension of the normal vector wavelet coding (VWC) technique to arbitrarily shaped objects. Results of applying SA-VWC to real arbitrarily shaped texture coding are also given at the end of this paper.
Electromagnetic analysis of arbitrarily shaped pinched carpets
Dupont, Guillaume; Guenneau, Sebastien; Enoch, Stefan
2010-09-15
We derive the expressions for the anisotropic heterogeneous tensors of permittivity and permeability associated with two-dimensional and three-dimensional carpets of an arbitrary shape. In the former case, we map a segment onto smooth curves whereas in the latter case we map an arbitrary region of the plane onto smooth surfaces. Importantly, these carpets display no singularity of the permeability and permeability tensor components. Moreover, a reduced set of parameters leads to nonmagnetic two-dimensional carpets in p polarization (i.e., for a magnetic field orthogonal to the plane containing the carpet). Such an arbitrarily shaped carpet is shown to work over a finite bandwidth when it is approximated by a checkerboard with 190 homogeneous cells of piecewise constant anisotropic permittivity. We finally perform some finite element computations in the full vector three-dimensional case for a plane wave in normal incidence and a Gaussian beam in oblique incidence. The latter requires perfectly matched layers set in a rotated coordinate axis which exemplifies the role played by geometric transforms in computational electromagnetism.
Casimir interaction of arbitrarily shaped conductors.
Straley, Joseph P; Kolomeisky, Eugene B
2017-04-12
We review a systematic practical implementation of the multiple scattering formalism due to Balian and Duplantier (1977 Ann. Phys. 104 300, 1978 Ann. Phys. 112 165) for the calculation of the Casimir interaction between arbitrarily shaped smooth conductors. The leading two-point scattering term of the expansion has a simple compact form, amenable to exact or accurate numerical evaluation. It is a general expression which improves upon the proximity force and pairwise summation approximations. We show that for many geometries it captures the bulk of the interaction effect. The inclusion of terms beyond the two-point approximation provides an accuracy check and explains screening. As an illustration of the power and versatility of the method we re-evaluate sphere-sphere and sphere-plane interactions and compared the results with previous findings that employed different methods. We also compute for the first time interaction of a hyperboloid (mimicking an atomic force microscope tip) and a plane. We also analyze the anomalous situations involving long cylindrical conductors where the two-point scattering approximation fails qualitatively. In such cases analytic summation of the entire scattering series is carried out and a topological argument is put forward as an explanation of the result. We give the extension of this theory to the case of finite temperatures where the two-point scattering approximation result has a simple compact form, also amenable to exact or accurate numerical evaluation.
Casimir interaction of arbitrarily shaped conductors
NASA Astrophysics Data System (ADS)
Straley, Joseph P.; Kolomeisky, Eugene B.
2017-04-01
We review a systematic practical implementation of the multiple scattering formalism due to Balian and Duplantier (1977 Ann. Phys. 104 300, 1978 Ann. Phys. 112 165) for the calculation of the Casimir interaction between arbitrarily shaped smooth conductors. The leading two-point scattering term of the expansion has a simple compact form, amenable to exact or accurate numerical evaluation. It is a general expression which improves upon the proximity force and pairwise summation approximations. We show that for many geometries it captures the bulk of the interaction effect. The inclusion of terms beyond the two-point approximation provides an accuracy check and explains screening. As an illustration of the power and versatility of the method we re-evaluate sphere–sphere and sphere–plane interactions and compared the results with previous findings that employed different methods. We also compute for the first time interaction of a hyperboloid (mimicking an atomic force microscope tip) and a plane. We also analyze the anomalous situations involving long cylindrical conductors where the two-point scattering approximation fails qualitatively. In such cases analytic summation of the entire scattering series is carried out and a topological argument is put forward as an explanation of the result. We give the extension of this theory to the case of finite temperatures where the two-point scattering approximation result has a simple compact form, also amenable to exact or accurate numerical evaluation.
A THz Tomography System for Arbitrarily Shaped Samples
NASA Astrophysics Data System (ADS)
Stübling, E.; Bauckhage, Y.; Jelli, E.; Fischer, B.; Globisch, B.; Schell, M.; Heinrich, A.; Balzer, J. C.; Koch, M.
2017-06-01
We combine a THz time-domain spectroscopy system with a robotic arm. With this scheme, the THz emitter and receiver can be positioned perpendicular and at defined distance to the sample surface. Our system allows the acquisition of reflection THz tomographic images of samples with an arbitrarily shaped surface.
A THz Tomography System for Arbitrarily Shaped Samples
NASA Astrophysics Data System (ADS)
Stübling, E.; Bauckhage, Y.; Jelli, E.; Fischer, B.; Globisch, B.; Schell, M.; Heinrich, A.; Balzer, J. C.; Koch, M.
2017-10-01
We combine a THz time-domain spectroscopy system with a robotic arm. With this scheme, the THz emitter and receiver can be positioned perpendicular and at defined distance to the sample surface. Our system allows the acquisition of reflection THz tomographic images of samples with an arbitrarily shaped surface.
Semi-analytical solution to arbitrarily shaped beam scattering
NASA Astrophysics Data System (ADS)
Wang, Wenjie; Zhang, Huayong; Sun, Yufa
2017-07-01
Based on the field expansions in terms of appropriate spherical vector wave functions and the method of moments scheme, an exact semi-analytical solution to the scattering of an arbitrarily shaped beam is given. For incidence of a Gaussian beam, zero-order Bessel beam and Hertzian electric dipole radiation, numerical results of the normalized differential scattering cross section are presented to a spheroid and a circular cylinder of finite length, and the scattering properties are analyzed concisely.
Equivalent sources method for supersonic intensity of arbitrarily shaped geometries
NASA Astrophysics Data System (ADS)
Valdivia, Nicolas P.; Williams, Earl G.; Herdic, Peter C.
2015-07-01
Supersonic acoustic intensity is utilized to locate radiating regions on a complex vibrating structure. The supersonic intensity is obtained by a special process that removes the evanescent waves from the near-field acoustical holography measurement. The filtering process is well understood for separable geometries, but unfortunately, there are few results for arbitrarily shaped objects. This work proposes a methodology based on a stable invertible representation of the radiated power operator. The power operator is approximated numerically by the equivalent source formulation and the appropriate complete spectral basis is employed to form the stable invertible operator. The operator is formed with the most efficient radiation modes and these modes are utilized to obtain the supersonic solution for the near-field holographic problem. This concept is tested using numerically generated data in a spherical geometry and the results are validated with the spherical harmonic, supersonic filter. Finally, a vibrating ship-hull structure provides a physical example for application and validation of the proposed methodology in a more complex geometry.
Light squeezing through arbitrarily shaped plasmonic channels and sharp bends
Alu, Andrea; Engheta, Nader
2008-07-15
We propose a mechanism for optical energy squeezing and anomalous light transmission through arbitrarily-shaped plasmonic ultranarrow channels and bends connecting two larger plasmonic metal-insulator-metal waveguides. It is shown how a proper design of subwavelength optical channels at cutoff, patterned by plasmonic implants and connecting larger plasmonic waveguides, may allow enhanced resonant transmission inspired by the anomalous properties of epsilon-near-zero (ENZ) metamaterials. The resonant transmission is shown to be only weakly dependent on the channel length and its specific geometry, such as possible presence of abruptions and bends.
Energy levels in self-assembled quantum arbitrarily shaped dots.
Tablero, C
2005-02-08
A model to determine the electronic structure of self-assembled quantum arbitrarily shaped dots is applied. This model is based principally on constant effective mass and constant potentials of the barrier and quantum dot material. An analysis of the different parameters of this model is done and compared with those which take into account the variation of confining potentials, bands, and effective masses due to strain. The results are compared with several spectra reported in literature. By considering the symmetry, the computational cost is reduced with respect to other methods in literature. In addition, this model is not limited by the geometry of the quantum dot.
Distributed force simulation for arbitrarily shaped IPMC actuators
NASA Astrophysics Data System (ADS)
Martinez, M.; Lumia, R.
2013-07-01
This paper presents a simulation model that predicts the force output of arbitrarily shaped ionic polymer-metal composite (IPMC) actuators. Theoretical and experimental force measurements are compared for a triangular IPMC actuator with a tip length of 11 mm. The results show that the simulated tip force is within 80% of the experimentally determined value. Simulated electrical results for an artificial shark pectoral fin and a 7 mm × 17 mm actuator are also presented. In each case, the voltage is shown to decrease exponentially from the input point. The results of an ion migration simulation for a 180 μm cubic element of Nafion are presented for both a constant 2 V input and a 2 V 0.25 Hz sine signal. Finally, the simulated deformation of an IPMC shark fin is shown.
Brownian motion of arbitrarily shaped particles in two dimensions.
Chakrabarty, Ayan; Konya, Andrew; Wang, Feng; Selinger, Jonathan V; Sun, Kai; Wei, Qi-Huo
2014-11-25
We implement microfabricated boomerang particles with unequal arm lengths as a model for nonsymmetric particles and study their Brownian motion in a quasi-two-dimensional geometry by using high-precision single-particle motion tracking. We show that because of the coupling between translation and rotation, the mean squared displacements of a single asymmetric boomerang particle exhibit a nonlinear crossover from short-time faster to long-time slower diffusion, and the mean displacements for fixed initial orientation are nonzero and saturate out at long times. The measured anisotropic diffusion coefficients versus the tracking point position indicate that there exists one unique point, i.e., the center of hydrodynamic stress (CoH), at which all coupled diffusion coefficients vanish. This implies that in contrast to motion in three dimensions where the CoH exists only for high-symmetry particles, the CoH always exists for Brownian motion in two dimensions. We develop an analytical model based on Langevin theory to explain the experimental results and show that among the six anisotropic diffusion coefficients only five are independent because the translation-translation coupling originates from the translation-rotation coupling. Finally, we classify the behavior of two-dimensional Brownian motion of arbitrarily shaped particles into four groups based on the particle shape symmetry group and discussed potential applications of the CoH in simplifying understanding of the circular motions of microswimmers.
Mass and charge transport in arbitrarily shaped microchannels
NASA Astrophysics Data System (ADS)
Bruus, Henrik; Asger Mortensen, Niels; Okkels, Fridolin; Hoejgaard Olesen, Laurits
2006-11-01
We consider laminar flow of incompressible electrolytes in long, straight channels driven by pressure and electro-osmosis. We use a Hilbert space eigenfunction expansion to address the problem of arbitrarily shaped cross sections and obtain general results in linear-response theory for the mass and charge transport coefficients which satisfy Onsager relations [1,2]. In the limit of non-overlapping Debye layers the transport coefficients are simply expressed in terms of parameters of the electrolyte as well as half the hydraulic diameter R=2 A/P with A and P being the cross- sectional area and perimeter, respectively. In particular, we consider the limits of thin non-overlapping as well as strongly overlapping Debye layers, respectively, and calculate the corrections to the hydraulic resistance due to electro- hydrodynamic interactions.[1] N. A. Mortensen, F. Okkels, and H. Bruus, Phys. Rev. E 71, 057301 (2005) [2] N. A. Mortensen, L. H. Olesen, and H. Bruus, New J. Phys. 8, 37 (2006)
NASA Technical Reports Server (NTRS)
Mishchenko, Michael I.
2003-01-01
We use the concepts of statistical electromagnetics to derive the general radiative transfer equation (RTE) describing multiple scattering of polarized light by sparse discrete random media consisting of arbitrarily shaped and arbitrarily oriented particles. The derivation starts from the volume integral and Lippmann-Schwinger equations for the electric field scattered by a fixed N-particle system and proceeds to the vector form of the Foldy-Lax equations and their approximate far-field version. We then assume that particle positions are completely random and derive the vector RTE by applying the Twersky approximation to the coherent electric field and the Twersky and ladder approximations to the coherency dyad of the diffuse field in the limit N -> infinity. The concluding section discusses the physical meaning of the quantities entering the general vector RTE and the assumptions made in its derivation.
NASA Technical Reports Server (NTRS)
Mishchenko, Michael I.
2003-01-01
We use the concepts of statistical electromagnetics to derive the general radiative transfer equation (RTE) describing multiple scattering of polarized light by sparse discrete random media consisting of arbitrarily shaped and arbitrarily oriented particles. The derivation starts from the volume integral and Lippmann-Schwinger equations for the electric field scattered by a fixed N-particle system and proceeds to the vector form of the Foldy-Lax equations and their approximate far-field version. We then assume that particle positions are completely random and derive the vector RTE by applying the Twersky approximation to the coherent electric field and the Twersky and ladder approximations to the coherency dyad of the diffuse field in the limit N -> infinity. The concluding section discusses the physical meaning of the quantities entering the general vector RTE and the assumptions made in its derivation.
Electromagnetic Scattering Analysis of Arbitrarily Shaped Material Cylinder by FEM-BEM Method
NASA Technical Reports Server (NTRS)
Deshpande, M. D.; Cockrell, C. R.; Reddy, C. J.
1996-01-01
A hybrid method that combines the finite element method (FEM) and the boundary element method (BEM) is developed to analyze electromagnetic scattering from arbitrarily shaped material cylinders. By this method, the material cylinder is first enclosed by a fictitious boundary. Maxwell's equations are then solved by FEM inside and by BEM outside the boundary. Electromagnetic scattering from several arbitrarily shaped material cylinders is computed and compared with results obtained by other numerical techniques.
Haner, M; Warren, W S
1987-09-01
We have produced complex software adjustable laser pulse shapes with ~10-ps resolution, and pulse energies up to 100 microJ for spectroscopic applications. The key devices are a high damage threshold electrooptic directional coupler and a GaAs circuit for synthesizing arbitrarily shaped microwave pulses.
Extracting physical properties of arbitrarily shaped laser-doped micro-scale areas in semiconductors
Heinrich, Martin; Kluska, Sven; Hameiri, Ziv; Hoex, Bram; Aberle, Armin G.
2013-12-23
We present a method that allows the extraction of relevant physical properties such as sheet resistance and dopant profile from arbitrarily shaped laser-doped micro-scale areas formed in semiconductors with a focused pulsed laser beam. The key feature of the method is to use large laser-doped areas with an identical average number of laser pulses per area (laser pulse density) as the arbitrarily shaped areas. The method is verified using sheet resistance measurements on laser-doped silicon samples. Furthermore, the method is extended to doping with continuous-wave lasers by using the average number of passes per area or density of passes.
Tactile feedback to the palm using arbitrarily shaped DEA
NASA Astrophysics Data System (ADS)
Mößinger, Holger; Haus, Henry; Kauer, Michaela; Schlaak, Helmut F.
2014-03-01
Tactile stimulation enhances user experience and efficiency in human machine interaction by providing information via another sensory channel to the human brain. DEA as tactile interfaces have been in the focus of research in recent years. Examples are (vibro-) tactile keyboards or Braille displays. These applications of DEA focus mainly on interfacing with the user's fingers or fingertips only - demonstrating the high spatial resolution achievable with DEA. Besides providing a high resolution, the flexibility of DEA also allows designing free form surfaces equipped with single actuators or actuator matrices which can be fitted to the surface of the human skin. The actuators can then be used to provide tactile stimuli to different areas of the body, not to the fingertips only. Utilizing and demonstrating this flexibility we designed a free form DEA pad shaped to fit into the inside of the human palm. This pad consists of four single actuators which can provide e.g. directional information such as left, right, up and down. To demonstrate the value of such free form actuators we manufactured a PC-mouse using 3d printing processes. The actuator pad is mounted on the back of the mouse, resting against the palm while operating it. Software on the PC allows control of the vibration patterns displayed by the actuators. This allows helping the user by raising attention to certain directions or by discriminating between different modes like "pick" or "manipulate". Results of first tests of the device show an improved user experience while operating the PC mouse.
Modeling the motion of a toy car traveling on an arbitrarily shaped track
NASA Astrophysics Data System (ADS)
Wick, D. P.; Ramsdell, M. W.
2002-07-01
An analysis is performed on the motion of a Matchbox car racing down an arbitrarily shaped track that resides in a two-dimensional vertical plane. The role of friction, track shape, and air resistance on the car's performance is investigated. The parameters that describe the car's effective coefficient of friction and drag constant are experimentally extracted by consideration of its motion on a flat, horizontal track. These parameters are then employed to make predictions of the velocity on an arbitrarily shaped track containing hills and valleys and compared with measured values. A rigidly mounted shield of varying cross-sectional area is used to enhance the effects of drag. This analysis has been successfully incorporated into an advanced group project for an introductory course in classical mechanics and can be customized to accommodate a variety of levels.
Ray-tracing method for creeping waves on arbitrarily shaped nonuniform rational B-splines surfaces.
Chen, Xi; He, Si-Yuan; Yu, Ding-Feng; Yin, Hong-Cheng; Hu, Wei-Dong; Zhu, Guo-Qiang
2013-04-01
An accurate creeping ray-tracing algorithm is presented in this paper to determine the tracks of creeping waves (or creeping rays) on arbitrarily shaped free-form parametric surfaces [nonuniform rational B-splines (NURBS) surfaces]. The main challenge in calculating the surface diffracted fields on NURBS surfaces is due to the difficulty in determining the geodesic paths along which the creeping rays propagate. On one single parametric surface patch, the geodesic paths need to be computed by solving the geodesic equations numerically. Furthermore, realistic objects are generally modeled as the union of several connected NURBS patches. Due to the discontinuity of the parameter between the patches, it is more complicated to compute geodesic paths on several connected patches than on one single patch. Thus, a creeping ray-tracing algorithm is presented in this paper to compute the geodesic paths of creeping rays on the complex objects that are modeled as the combination of several NURBS surface patches. In the algorithm, the creeping ray tracing on each surface patch is performed by solving the geodesic equations with a Runge-Kutta method. When the creeping ray propagates from one patch to another, a transition method is developed to handle the transition of the creeping ray tracing across the border between the patches. This creeping ray-tracing algorithm can meet practical requirements because it can be applied to the objects with complex shapes. The algorithm can also extend the applicability of NURBS for electromagnetic and optical applications. The validity and usefulness of the algorithm can be verified from the numerical results.
Fast superposition T-matrix solution for clusters with arbitrarily-shaped constituent particles
NASA Astrophysics Data System (ADS)
Markkanen, Johannes; Yuffa, Alex J.
2017-03-01
A fast superposition T-matrix solution is formulated for electromagnetic scattering by a collection of arbitrarily-shaped inhomogeneous particles. The T-matrices for individual constituents are computed by expanding the Green's dyadic in the spherical vector wave functions and formulating a volume integral equation, where the equivalent electric current is the unknown and the spherical vector wave functions are treated as excitations. Furthermore, the volume integral equation and the superposition T-matrix are accelerated by the precorrected-FFT algorithm and the fast multipole algorithm, respectively. The approach allows for an efficient scattering analysis of the clusters and aggregates consisting of a large number of arbitrarily-shaped inhomogeneous particles.
Ray tracing method in arbitrarily shaped radial graded-index waveguide.
Tsukada, Kenji; Nihei, Eisuke
2015-10-10
A ray tracing algorithm for an arbitrarily shaped axially symmetric graded index waveguide was proposed. This was achieved by considering the center of the waveguide (optical axis) as a set of discrete points. The refractive index depends on the distance of the ray position from the optical axis. This distance was approximated as the shortest distance between the ray position and a point in the set. Using this algorithm, ray tracing could be performed, regardless of the waveguide configuration. In this study, a precise explanation of the algorithm is given and the errors are evaluated. A technique to reduce computing time is also included.
Boundary conditions for arbitrarily shaped and tightly focused laser pulses in electromagnetic codes
NASA Astrophysics Data System (ADS)
Thiele, Illia; Skupin, Stefan; Nuter, Rachel
2016-09-01
Investigation of laser matter interaction with electromagnetic codes requires to implement sources for the electromagnetic fields. A way to do so is to prescribe the fields at the numerical box boundaries in order to achieve the desired fields inside the numerical box. Here we show that the often used paraxial approximation can lead to unexpected field profiles with strong impact on the laser matter interaction results. We propose an efficient numerical algorithm to compute the required laser boundary conditions consistent with the Maxwell's equations for arbitrarily shaped, tightly focused laser pulses.
Simulations of the Motion of Arbitrarily Shaped Fibers in a Linear Shear Flow
NASA Astrophysics Data System (ADS)
Roshchenko, Andriy; Finlay, Warren; Minev, Peter
2010-11-01
Fibrous airborne particles cause severe adverse health effects when inhaled and deposited in human lungs. For this reason, fiber deposition in the lungs has been studied by numerous authors. However, a complete mechanistic model of fiber dynamics in the lungs has not yet been presented. One of the problems yet to be addressed involves the dynamics of arbitrarily shaped fibers in the lungs. Here, a two-grid fictitious domain method was used for direct simulations of arbitrarily shaped high aspect ratio fibers in linear shear flow, including an improved microscale grid resolution scheme and a Lagrangian-Eulerian approach whereby we transform the equations from a laboratory coordinate system to one fixed with the microgrid. Our simulations show the expected Jeffery orbits for straight, symmetric fibers. However, for asymmetric fiber shapes we observe a surprising secondary rotation that is out of the shear plane. Our findings suggest that studies of deposition efficiencies of fibrous aerosols should account for possible increases in deposition due to asymmetrical aerosol particles or their aggregations.
Poulsen, Per Rugaard; Fledelius, Walther; Keall, Paul J.; Weiss, Elisabeth; Lu Jun; Brackbill, Emily; Hugo, Geoffrey D.
2011-04-15
Purpose: Implanted markers are commonly used in radiotherapy for x-ray based target localization. The projected marker position in a series of cone-beam CT (CBCT) projections can be used to estimate the three dimensional (3D) target trajectory during the CBCT acquisition. This has important applications in tumor motion management such as motion inclusive, gating, and tumor tracking strategies. However, for irregularly shaped markers, reliable segmentation is challenged by large variations in the marker shape with projection angle. The purpose of this study was to develop a semiautomated method for robust and reliable segmentation of arbitrarily shaped radiopaque markers in CBCT projections. Methods: The segmentation method involved the following three steps: (1) Threshold based segmentation of the marker in three to six selected projections with large angular separation, good marker contrast, and uniform background; (2) construction of a 3D marker model by coalignment and backprojection of the threshold-based segmentations; and (3) construction of marker templates at all imaging angles by projection of the 3D model and use of these templates for template-based segmentation. The versatility of the segmentation method was demonstrated by segmentation of the following structures in the projections from two clinical CBCT scans: (1) Three linear fiducial markers (Visicoil) implanted in or near a lung tumor and (2) an artificial cardiac valve in a lung cancer patient. Results: Automatic marker segmentation was obtained in more than 99.9% of the cases. The segmentation failed in a few cases where the marker was either close to a structure of similar appearance or hidden behind a dense structure (data cable). Conclusions: A robust template-based method for segmentation of arbitrarily shaped radiopaque markers in CBCT projections was developed.
Huang, Lei; Zuo, Chao; Idir, Mourad; Qu, Weijuan; Asundi, Anand
2015-04-21
A novel transport-of-intensity equation (TIE) based phase retrieval method is proposed with putting an arbitrarily-shaped aperture into the optical wavefield. In this arbitrarily-shaped aperture, the TIE can be solved under non-uniform illuminations and even non-homogeneous boundary conditions by iterative discrete cosine transforms with a phase compensation mechanism. Simulation with arbitrary phase, arbitrary aperture shape, and non-uniform intensity distribution verifies the effective compensation and high accuracy of the proposed method. Experiment is also carried out to check the feasibility of the proposed method in real measurement. Comparing to the existing methods, the proposed method is applicable for any types of phase distribution under non-uniform illumination and non-homogeneous boundary conditions within an arbitrarily-shaped aperture, which enables the technique of TIE with hard aperture become a more flexible phase retrieval tool in practical measurements.
Huang, Lei; Zuo, Chao; Idir, Mourad; ...
2015-04-21
A novel transport-of-intensity equation (TIE) based phase retrieval method is proposed with putting an arbitrarily-shaped aperture into the optical wavefield. In this arbitrarily-shaped aperture, the TIE can be solved under non-uniform illuminations and even non-homogeneous boundary conditions by iterative discrete cosine transforms with a phase compensation mechanism. Simulation with arbitrary phase, arbitrary aperture shape, and non-uniform intensity distribution verifies the effective compensation and high accuracy of the proposed method. Experiment is also carried out to check the feasibility of the proposed method in real measurement. Comparing to the existing methods, the proposed method is applicable for any types of phasemore » distribution under non-uniform illumination and non-homogeneous boundary conditions within an arbitrarily-shaped aperture, which enables the technique of TIE with hard aperture become a more flexible phase retrieval tool in practical measurements.« less
Improved cost-effective fabrication of arbitrarily shaped μIPMC transducers
NASA Astrophysics Data System (ADS)
Feng, Guo-Hua; Chen, Ri-Hong
2008-01-01
Conventional ionic polymer-metal composite (IPMC) production cuts individual transducers from bulk IPMC sheets. This paper presents a novel photolithographic technique that grows a large array of identical devices on a thin (~µm range) parylene diaphragm supported on a perforated substrate of material that is immune to the subsequent processing liquids. In particular, the new technique relies on a unique wax fill-up and removal concept that can produce arbitrarily shaped Nafion films with micron feature size. The developed process is cheap and results in devices of high uniformity and reliability, with greater design flexibility. Microtensile testing characterizes the fracture profiles of the non-electroded Nafion film and IPMC. Young's modulus is characterized, as well as maximum displacement and current consumption under various loading, driving voltages, waveforms and frequencies. High product quality and low process costs make this process of interest for mass production of micromachined IPMC transducers.
NASA Technical Reports Server (NTRS)
Mackenzie, Anne I.; Baginski, Michael E.; Rao, Sadasiva M.
2008-01-01
In this work, we present a new set of basis functions, defined over a pair of planar triangular patches, for the solution of electromagnetic scattering and radiation problems associated with arbitrarily-shaped surfaces using the method of moments solution procedure. The basis functions are constant over the function subdomain and resemble pulse functions for one and two dimensional problems. Further, another set of basis functions, point-wise orthogonal to the first set, is also defined over the same function space. The primary objective of developing these basis functions is to utilize them for the electromagnetic solution involving conducting, dielectric, and composite bodies. However, in the present work, only the conducting body solution is presented and compared with other data.
NASA Technical Reports Server (NTRS)
Mackenzie, Anne I.; Baginski, Michael E.; Rao, Sadasiva M.
2007-01-01
In this work, we present a new set of basis functions, de ned over a pair of planar triangular patches, for the solution of electromagnetic scattering and radiation problems associated with arbitrarily-shaped surfaces using the method of moments solution procedure. The basis functions are constant over the function subdomain and resemble pulse functions for one and two dimensional problems. Further, another set of basis functions, point-wise orthogonal to the first set, is also de ned over the same function space. The primary objective of developing these basis functions is to utilize them for the electromagnetic solution involving conducting, dielectric, and composite bodies. However, in the present work, only the conducting body solution is presented and compared with other data.
Reduction of the radar cross section of arbitrarily shaped cavity structures
NASA Astrophysics Data System (ADS)
Chou, R.; Ling, H.; Lee, S. W.
1987-08-01
The problem of the reduction of the radar cross section (RCS) of open-ended cavities was studied. The issues investigated were reduction through lossy coating materials on the inner cavity wall and reduction through shaping of the cavity. A method was presented to calculate the RCS of any arbitrarily shaped structure in order to study the shaping problem. The limitations of this method were also addressed. The modal attenuation was studied in a multilayered coated waveguide. It was shown that by employing two layers of coating, it was possible to achieve an increase in both the magnitude of attenuation and the frequency band of effectiveness. The numerical method used in finding the roots of the characteristic equation breaks down when the coating thickness is very lossy and large in terms of wavelength. A new method of computing the RCS of an arbitrary cavity was applied to study the effects of longitudinal bending on RCS reduction. The ray and modal descriptions for the fields in a parallel plate waveguide were compared. To extend the range of validity of the Shooting and Bouncing Ray (SBR) method, the simple ray picture must be modified to account for the beam blurring.
Reduction of the radar cross section of arbitrarily shaped cavity structures
NASA Technical Reports Server (NTRS)
Chou, R.; Ling, H.; Lee, S. W.
1987-01-01
The problem of the reduction of the radar cross section (RCS) of open-ended cavities was studied. The issues investigated were reduction through lossy coating materials on the inner cavity wall and reduction through shaping of the cavity. A method was presented to calculate the RCS of any arbitrarily shaped structure in order to study the shaping problem. The limitations of this method were also addressed. The modal attenuation was studied in a multilayered coated waveguide. It was shown that by employing two layers of coating, it was possible to achieve an increase in both the magnitude of attenuation and the frequency band of effectiveness. The numerical method used in finding the roots of the characteristic equation breaks down when the coating thickness is very lossy and large in terms of wavelength. A new method of computing the RCS of an arbitrary cavity was applied to study the effects of longitudinal bending on RCS reduction. The ray and modal descriptions for the fields in a parallel plate waveguide were compared. To extend the range of validity of the Shooting and Bouncing Ray (SBR) method, the simple ray picture must be modified to account for the beam blurring.
A two-level parallel direct search implementation for arbitrarily sized objective functions
Hutchinson, S.A.; Shadid, N.; Moffat, H.K.
1994-12-31
In the past, many optimization schemes for massively parallel computers have attempted to achieve parallel efficiency using one of two methods. In the case of large and expensive objective function calculations, the optimization itself may be run in serial and the objective function calculations parallelized. In contrast, if the objective function calculations are relatively inexpensive and can be performed on a single processor, then the actual optimization routine itself may be parallelized. In this paper, a scheme based upon the Parallel Direct Search (PDS) technique is presented which allows the objective function calculations to be done on an arbitrarily large number (p{sub 2}) of processors. If, p, the number of processors available, is greater than or equal to 2p{sub 2} then the optimization may be parallelized as well. This allows for efficient use of computational resources since the objective function calculations can be performed on the number of processors that allow for peak parallel efficiency and then further speedup may be achieved by parallelizing the optimization. Results are presented for an optimization problem which involves the solution of a PDE using a finite-element algorithm as part of the objective function calculation. The optimum number of processors for the finite-element calculations is less than p/2. Thus, the PDS method is also parallelized. Performance comparisons are given for a nCUBE 2 implementation.
Direct numerical simulation of an arbitrarily shaped particle at a fluidic interface
NASA Astrophysics Data System (ADS)
Lecrivain, Gregory; Yamamoto, Ryoichi; Hampel, Uwe; Taniguchi, Takashi
2017-06-01
A consistent formulation is presented for the direct numerical simulation of an arbitrarily shaped colloidal particle at a deformable fluidic interface. The rigid colloidal particle is decomposed into a collection of solid spherical beads and the three-phase boundaries are replaced with smoothly spreading interfaces. The major merit of the present formulation lies in the ease with which the geometrical decomposition of the colloidal particle is implemented, yet allows the dynamic simulation of intricate three-dimensional colloidal shapes in a binary fluid. The dynamics of a rodlike, a platelike, and a ringlike particle are presently tested. It is found that platelike particles attach more rapidly to a fluidic interface and are subsequently harder to dislodge when subject to an external force. Using the Bond number, i.e., the ratio of the gravitational force to the reference capillary force, a spherical particle with equal affinity for the two fluids breaks away from a fluidic interface at the critical value Bo=0.75 . This value is in line with our numerical experiments. It is here shown that a plate and a ring of equivalent masses detach at greater critical Bond numbers approximately equal to Bo=1.3 . Results of this study will find applications in the stabilization of emulsions by colloids and in the recovery of colloidal particles by rising bubbles.
NASA Technical Reports Server (NTRS)
Cockrell, C. R.; Beck, Fred B.
1997-01-01
The electromagnetic scattering from an arbitrarily shaped aperture backed by a rectangular cavity recessed in an infinite ground plane is analyzed by the integral equation approach. In this approach, the problem is split into two parts: exterior and interior. The electromagnetic fields in the exterior part are obtained from an equivalent magnetic surface current density assumed to be flowing over the aperture and backed by an infinite ground plane. The electromagnetic fields in the interior part are obtained in terms of rectangular cavity modal expansion functions. The modal amplitudes of cavity modes are determined by enforcing the continuity of the electric field across the aperture. The integral equation with the aperture magnetic current density as an unknown is obtained by enforcing the continuity of magnetic fields across the aperture. The integral equation is then solved for the magnetic current density by the method of moments. The electromagnetic scattering properties of an aperture backed by a rectangular cavity are determined from the magnetic current density. Numerical results on the backscatter radar cross-section (RCS) patterns of rectangular apertures backed by rectangular cavities are compared with earlier published results. Also numerical results on the backscatter RCS patterns of a circular aperture backed by a rectangular cavity are presented.
NASA Astrophysics Data System (ADS)
Quesada-Pereira, F. D.; Vidal, A.; Boria, V. E.; Alvarez-Melcón, A.; Gimeno, B.
2007-10-01
Radomes are usually made of lossy dielectric materials, and their accurate analysis is often cumbersome because of their typical large electrical size and geometrical complexity. In real reflector antenna structures, there are always complex interactions between the radome, the reflector surfaces and the directional feeds, which are typically neglected for the sake of simplicity. In this paper we will consider all such interactions in a very accurate way, thus requiring a high number of unknowns for the numerical solution of the problem. To overcome such drawback, an integral equation formulation based on the Equivalence Principle in combination with the wavelet transform has been employed, obtaining finally a robust and accurate CAD tool for the rigorous analysis of arbitrarily shaped radomes containing continuous and discrete electromagnetic sources. It will be shown that the use of wavelet-like bases substantially improves the numerical efficiency and memory requirements of the original integral equation method. For verification purposes, the results obtained with the new technique are successfully compared with examples taken from the literature. Complex antenna structures are then discussed in order to prove the usefulness of the new method.
Fully automatic segmentation of arbitrarily shaped fiducial markers in cone-beam CT projections
NASA Astrophysics Data System (ADS)
Bertholet, J.; Wan, H.; Toftegaard, J.; Schmidt, M. L.; Chotard, F.; Parikh, P. J.; Poulsen, P. R.
2017-02-01
Radio-opaque fiducial markers of different shapes are often implanted in or near abdominal or thoracic tumors to act as surrogates for the tumor position during radiotherapy. They can be used for real-time treatment adaptation, but this requires a robust, automatic segmentation method able to handle arbitrarily shaped markers in a rotational imaging geometry such as cone-beam computed tomography (CBCT) projection images and intra-treatment images. In this study, we propose a fully automatic dynamic programming (DP) assisted template-based (TB) segmentation method. Based on an initial DP segmentation, the DPTB algorithm generates and uses a 3D marker model to create 2D templates at any projection angle. The 2D templates are used to segment the marker position as the position with highest normalized cross-correlation in a search area centered at the DP segmented position. The accuracy of the DP algorithm and the new DPTB algorithm was quantified as the 2D segmentation error (pixels) compared to a manual ground truth segmentation for 97 markers in the projection images of CBCT scans of 40 patients. Also the fraction of wrong segmentations, defined as 2D errors larger than 5 pixels, was calculated. The mean 2D segmentation error of DP was reduced from 4.1 pixels to 3.0 pixels by DPTB, while the fraction of wrong segmentations was reduced from 17.4% to 6.8%. DPTB allowed rejection of uncertain segmentations as deemed by a low normalized cross-correlation coefficient and contrast-to-noise ratio. For a rejection rate of 9.97%, the sensitivity in detecting wrong segmentations was 67% and the specificity was 94%. The accepted segmentations had a mean segmentation error of 1.8 pixels and 2.5% wrong segmentations.
Sister, Ilya; Leviatan, Yehuda; Schächter, Levi
2017-06-12
Planck's famous blackbody radiation law was derived under the assumption that the dimensions of the radiating body are significantly larger than the radiated wavelengths. What is unique about Planck's formula is the fact that it is independent of the exact loss mechanism and the geometry. Therefore, for a long period of time, it was regarded as a fundamental property of all materials. Deviations from its predictions were attributed to imperfections and referred to as the emissivity of the specific body, a quantity which was always assumed to be smaller than unity. Recent studies showed that the emission spectrum is affected by the geometry of the body and in fact, in a limited frequency range, the emitted spectrum may exceed Planck's prediction provided the typical size of the body is of the same order of magnitude as the emitted wavelength. For the investigation of the blackbody radiation from an arbitrarily shaped body, we developed a code which incorporates the fluctuation-dissipation theorem (FDT) and the source model technique (SMT). The former determines the correlation between the quasi-microscopic current densities in the body and the latter is used to solve the electromagnetic problem numerically. In this study we present the essence of combining the two concepts. We verify the validity of our code by comparing its results obtained for the case of a sphere against analytic results and discuss how the accuracy of the solution is assessed in the general case. Finally, we illustrate several configurations in which the emitted spectrum exceeds Planck's prediction as well as cases in which the geometrical resonances of the body are revealed.
NASA Technical Reports Server (NTRS)
Park, Jong M.; Eversman, W.
1992-01-01
2D sound propagation over an arbitrarily-shaped barrier situated on a locally reacting infinite plane in a homogeneous medium is treated utilizing the BEM. The BIE is formulated so that the integral along an infinite homogeneous plane disappears if the half space Green's function is selected to satisfy the boundary condition of this plane. Comparison of the BEM results with test results by Habault and by Kearns shows good agreement of the sound field utilizing the BEM.
NASA Technical Reports Server (NTRS)
Park, Jong M.; Eversman, W.
1992-01-01
2D sound propagation over an arbitrarily-shaped barrier situated on a locally reacting infinite plane in a homogeneous medium is treated utilizing the BEM. The BIE is formulated so that the integral along an infinite homogeneous plane disappears if the half space Green's function is selected to satisfy the boundary condition of this plane. Comparison of the BEM results with test results by Habault and by Kearns shows good agreement of the sound field utilizing the BEM.
Sugiura, Yuki; Tsuru, Kanji; Ishikawa, Kunio
2017-08-01
Carbonate apatite (CO3Ap) foam with an interconnected porous structure is highly attractive as a scaffold for bone replacement. In this study, arbitrarily shaped CO3Ap foam was formed from α-tricalcium phosphate (α-TCP) foam granules via a two-step process involving treatment with acidic calcium phosphate solution followed by hydrothermal treatment with NaHCO3. The treatment with acidic calcium phosphate solution, which is key to fabricating arbitrarily shaped CO3Ap foam, enables dicalcium hydrogen phosphate dihydrate (DCPD) crystals to form on the α-TCP foam granules. The generated DCPD crystals cause the α-TCP granules to interlock with each other, inducing an α-TCP/DCPD foam. The interlocking structure containing DCPD crystals can survive hydrothermal treatment with NaHCO3. The arbitrarily shaped CO3Ap foam was fabricated from the α-TCP/DCPD foam via hydrothermal treatment at 200 °C for 24 h in the presence of a large amount of NaHCO3.
Object recognition using metric shape.
Lee, Young-Lim; Lind, Mats; Bingham, Ned; Bingham, Geoffrey P
2012-09-15
Most previous studies of 3D shape perception have shown a general inability to visually perceive metric shape. In line with this, studies of object recognition have shown that only qualitative differences, not quantitative or metric ones can be used effectively for object recognition. Recently, Bingham and Lind (2008) found that large perspective changes (≥ 45°) allow perception of metric shape and Lee and Bingham (2010) found that this, in turn, allowed accurate feedforward reaches-to-grasp objects varying in metric shape. We now investigated whether this information would allow accurate and effective recognition of objects that vary in respect to metric shape. Both judgment accuracies (d') and reaction times confirmed that, with the availability of visual information in large perspective changes, recognition of objects using quantitative as compared to qualitative properties was equivalent in accuracy and speed of judgments. The ability to recognize objects based on their metric shape is, therefore, a function of the availability or unavailability of requisite visual information. These issues and results are discussed in the context of the Two Visual System hypothesis of Milner and Goodale (1995, 2006). 2012 Elsevier Ltd. All rights reserved
NASA Astrophysics Data System (ADS)
Gómez-DíAz, J. S.; Quesada-Pereira, F. D.; Gómez-Tornero, J. L.; Pascual-GarcíA, J.; ÁLvarez-Melcón, A.
2007-10-01
In this paper, a spatial image technique is used to efficiently calculate the mixed potential Green's functions associated with electric sources, when they are placed inside arbitrarily shaped cylindrical cavities. The technique is based on placing electric dipole images and charges outside the cavity region. Their strength and orientation are then calculated by imposing the appropriate boundary conditions for the fields at discrete points on the metallic wall. A method for the assessment of the potentials accuracy is proposed, and several optimization techniques are presented. Three cavities are analyzed to demonstrate the usefulness of the techniques. The cutoff frequencies and potentials patterns are compared to those obtained by a standard finite elements technique, showing excellent agreement. Finally, a band-pass filter based on coupled lines is analyzed, demonstrating the practical value of the technique.
NASA Astrophysics Data System (ADS)
Xu, Kai-Jiang; Pan, Xiao-Min; Li, Ren-Xian; Sheng, Xin-Qing
2017-07-01
In optical trapping applications, the optical force should be investigated within a wide range of parameter space in terms of beam configuration to reach the desirable performance. A simple but reliable way of conducting the related investigation is to evaluate optical forces corresponding to all possible beam configurations. Although the optical force exerted on arbitrarily shaped particles can be well predicted by boundary element method (BEM), such investigation is time costing because it involves many repetitions of expensive computation, where the forces are calculated from the equivalent surface currents. An algorithm is proposed to alleviate the difficulty by exploiting our previously developed skeletonization framework. The proposed algorithm succeeds in reducing the number of repetitions. Since the number of skeleton beams is always much less than that of beams in question, the computation can be very efficient. The proposed algorithm is accurate because the skeletonization is accuracy controllable.
Regmi, Rajesh; Lovelock, D. Michael; Hunt, Margie; Zhang, Pengpeng; Pham, Hai; Xiong, Jianping; Yorke, Ellen D.; Goodman, Karyn A.; Rimner, Andreas; Mostafavi, Hassan; Mageras, Gig S.
2014-01-01
Purpose: Certain types of commonly used fiducial markers take on irregular shapes upon implantation in soft tissue. This poses a challenge for methods that assume a predefined shape of markers when automatically tracking such markers in kilovoltage (kV) radiographs. The authors have developed a method of automatically tracking regularly and irregularly shaped markers using kV projection images and assessed its potential for detecting intrafractional target motion during rotational treatment. Methods: Template-based matching used a normalized cross-correlation with simplex minimization. Templates were created from computed tomography (CT) images for phantom studies and from end-expiration breath-hold planning CT for patient studies. The kV images were processed using a Sobel filter to enhance marker visibility. To correct for changes in intermarker relative positions between simulation and treatment that can introduce errors in automatic matching, marker offsets in three dimensions were manually determined from an approximately orthogonal pair of kV images. Two studies in anthropomorphic phantom were carried out, one using a gold cylindrical marker representing regular shape, another using a Visicoil marker representing irregular shape. Automatic matching of templates to cone beam CT (CBCT) projection images was performed to known marker positions in phantom. In patient data, automatic matching was compared to manual matching as an approximate ground truth. Positional discrepancy between automatic and manual matching of less than 2 mm was assumed as the criterion for successful tracking. Tracking success rates were examined in kV projection images from 22 CBCT scans of four pancreas, six gastroesophageal junction, and one lung cancer patients. Each patient had at least one irregularly shaped radiopaque marker implanted in or near the tumor. In addition, automatic tracking was tested in intrafraction kV images of three lung cancer patients with irregularly shaped
Regmi, Rajesh; Lovelock, D. Michael; Hunt, Margie; Zhang, Pengpeng; Pham, Hai; Xiong, Jianping; Yorke, Ellen D.; Mageras, Gig S.; Goodman, Karyn A.; Rimner, Andreas; Mostafavi, Hassan
2014-07-15
Purpose: Certain types of commonly used fiducial markers take on irregular shapes upon implantation in soft tissue. This poses a challenge for methods that assume a predefined shape of markers when automatically tracking such markers in kilovoltage (kV) radiographs. The authors have developed a method of automatically tracking regularly and irregularly shaped markers using kV projection images and assessed its potential for detecting intrafractional target motion during rotational treatment. Methods: Template-based matching used a normalized cross-correlation with simplex minimization. Templates were created from computed tomography (CT) images for phantom studies and from end-expiration breath-hold planning CT for patient studies. The kV images were processed using a Sobel filter to enhance marker visibility. To correct for changes in intermarker relative positions between simulation and treatment that can introduce errors in automatic matching, marker offsets in three dimensions were manually determined from an approximately orthogonal pair of kV images. Two studies in anthropomorphic phantom were carried out, one using a gold cylindrical marker representing regular shape, another using a Visicoil marker representing irregular shape. Automatic matching of templates to cone beam CT (CBCT) projection images was performed to known marker positions in phantom. In patient data, automatic matching was compared to manual matching as an approximate ground truth. Positional discrepancy between automatic and manual matching of less than 2 mm was assumed as the criterion for successful tracking. Tracking success rates were examined in kV projection images from 22 CBCT scans of four pancreas, six gastroesophageal junction, and one lung cancer patients. Each patient had at least one irregularly shaped radiopaque marker implanted in or near the tumor. In addition, automatic tracking was tested in intrafraction kV images of three lung cancer patients with irregularly shaped
A particle-particle collision strategy for arbitrarily shaped particles at low Stokes numbers
NASA Astrophysics Data System (ADS)
Daghooghi, Mohsen; Borazjani, Iman
2016-11-01
We present a collision strategy for particles with any general shape at low Stokes numbers. Conventional collision strategies rely upon a short -range repulsion force along particles centerline, which is a suitable choice for spherical particles and may not work for complex-shaped particles. In the present method, upon the collision of two particles, kinematics of particles are modified so that particles have zero relative velocity toward each other along the direction in which they have the minimum distance. The advantage of this novel technique is that it guaranties to prevent particles from overlapping without unrealistic bounce back at low Stokes numbers, which may occur if repulsive forces are used. This model is used to simulate sedimentation of many particles in a vertical channel and suspensions of non-spherical particles under simple shear flow. This work was supported by the American Chemical Society (ACS) Petroleum Research Fund (PRF) Grant Number 53099-DNI9. The computational resources were partly provided by the Center for Computational Research (CCR) at the University at Buffalo.
Expansion of an arbitrarily oriented, located, and shaped beam in spheroidal coordinates.
Xu, Feng; Ren, Kuanfang; Cai, Xiaoshu
2007-01-01
Within the framework of the generalized Lorenz-Mie theory (GLMT), the incident shaped beam of an arbitrary orientation and location is expanded in terms of the spheroidal vector wave functions in given spheroidal coordinates. The beam shape coefficients (BSCs) in spheroidal coordinates are computed by the quadrature method. The classical localization approximation method for BSC evaluation is found to be inapplicable when the Cartesian coordinates of the beam and the particle are not parallel to each other. Once they are parallel, all the symmetry relationships existing for the BSCs in spherical coordinates (spherical BSCs) [J. Opt. Soc. Am. A11, 1812 (1994)] still pertain to the BSCs in spheroidal coordinates (spheroidal BSCs). In addition, the spheroidal BSCs computed by our method are verified by comparing them with those evaluated by Asano and Yamamoto for plane wave incidence [Appl. Opt.14, 29 (1975)]. Furthermore, formulas are given for field reconstruction from the spheroidal BSCs, and consistency is found between the original incident fields and the reconstructed ones.
NASA Astrophysics Data System (ADS)
Schnitzer, Ory; Giannini, Vincenzo; Maier, Stefan A.; Craster, Richard V.
2016-07-01
According to the hydrodynamic Drude model, surface plasmon resonances of metallic nanostructures blueshift owing to the non-local response of the metal's electron gas. The screening length characterizing the non-local effect is often small relative to the overall dimensions of the metallic structure, which enables us to derive a coarse-grained non-local description using matched asymptotic expansions; a perturbation theory for the blueshifts of arbitrary-shaped nanometallic structures is then developed. The effect of non-locality is not always a perturbation and we present a detailed analysis of the `bonding' modes of a dimer of nearly touching nanowires where the leading-order eigenfrequencies and eigenmode distributions are shown to be a renormalization of those predicted assuming a local metal permittivity.
Giannini, Vincenzo; Maier, Stefan A.; Craster, Richard V.
2016-01-01
According to the hydrodynamic Drude model, surface plasmon resonances of metallic nanostructures blueshift owing to the non-local response of the metal’s electron gas. The screening length characterizing the non-local effect is often small relative to the overall dimensions of the metallic structure, which enables us to derive a coarse-grained non-local description using matched asymptotic expansions; a perturbation theory for the blueshifts of arbitrary-shaped nanometallic structures is then developed. The effect of non-locality is not always a perturbation and we present a detailed analysis of the ‘bonding’ modes of a dimer of nearly touching nanowires where the leading-order eigenfrequencies and eigenmode distributions are shown to be a renormalization of those predicted assuming a local metal permittivity. PMID:27493575
3-D analysis on arbitrarily-shaped ICRF antennas and Faraday shields
Chen, G.L.; Whealton, J.H.; Baity, F.W.; Hoffman, D.J.; Owens, T.L.
1986-01-01
Cavity antennas with Faraday shields are proposed to couple ion cyclotron radio frequency power for heating fusion plasmas. This application requires small, high-power, low-frequency antennas. The results are presented of a theoretical study of the ICRF antennas being developed for this purpose at the Radio Frequency Test Facility (RFTF). The objectives of this work are to optimize experimental designs and to confirm test results. (MOW)
Shooting and bouncing rays - Calculating the RCS of an arbitrarily shaped cavity
NASA Technical Reports Server (NTRS)
Ling, Hao; Chou, Ri-Chee; Lee, Shung-Wu
1989-01-01
A ray-shooting approach is presented for calculating the interior radar cross section (RCS) from a partially open cavity. In the problem considered, a dense grid of rays is launched into the cavity through the opening. The rays bounce from the cavity walls based on the laws of geometrical optics and eventually exit the cavity via the aperture. The ray-bouncing method is based on tracking a large number of rays launched into the cavity through the opening and determining the geometrical optics field associated with each ray by taking into consideration (1) the geometrical divergence factor, (2) polarization, and (3) material loading of the cavity walls. A physical optics scheme is then applied to compute the backscattered field from the exit rays. This method is so simple in concept that there is virtually no restriction on the shape or material loading of the cavity. Numerical results obtained by this method are compared with those for the modal analysis for a circular cylinder terminated by a PEC plate. RCS results for an S-bend circular cylinder generated on the Cray X-MP supercomputer show significant RCS reduction. Some of the limitations and possible extensions of this technique are discussed.
Electron quantization in arbitrarily shaped gold islands on MgO thin films
NASA Astrophysics Data System (ADS)
Stiehler, Christian; Pan, Yi; Schneider, Wolf-Dieter; Koskinen, Pekka; Häkkinen, Hannu; Nilius, Niklas; Freund, Hans-Joachim
2013-09-01
Low-temperature scanning tunneling microscopy has been employed to analyze the formation of quantum well states (QWS) in two-dimensional gold islands, containing between 50 and 200 atoms, on MgO thin films. The energy position and symmetry of the eigenstates are revealed from conductance spectroscopy and imaging. The majority of the QWS originates from overlapping Au 6p orbitals in the individual atoms and is unoccupied. Their characteristic is already reproduced with simple particle-in-a-box models that account for the symmetry of the islands (rectangular, triangular, or linear). However, better agreement is achieved when considering the true atomic structure of the aggregates via a density functional tight-binding approach. Based on a statistically relevant number of single-island data, we have established a correlation between the island geometry and the gap between the highest-occupied and the lowest-unoccupied molecular orbital in the finite-sized islands. The linear eccentricity is identified as a suitable descriptor for this relationship, as it combines information on both island size and island shape. Finally, the depth of the confinement potential is determined from the spatial extension of QWS beyond the physical boundaries of the Au islands. Our paper demonstrates how electron quantization effects can be analyzed in detail in metal nanostructures. The results may help elucidating the interplay between electronic and chemical properties of oxide-supported clusters as used in heterogeneous catalysis.
Shooting and bouncing rays - Calculating the RCS of an arbitrarily shaped cavity
NASA Technical Reports Server (NTRS)
Ling, Hao; Chou, Ri-Chee; Lee, Shung-Wu
1989-01-01
A ray-shooting approach is presented for calculating the interior radar cross section (RCS) from a partially open cavity. In the problem considered, a dense grid of rays is launched into the cavity through the opening. The rays bounce from the cavity walls based on the laws of geometrical optics and eventually exit the cavity via the aperture. The ray-bouncing method is based on tracking a large number of rays launched into the cavity through the opening and determining the geometrical optics field associated with each ray by taking into consideration (1) the geometrical divergence factor, (2) polarization, and (3) material loading of the cavity walls. A physical optics scheme is then applied to compute the backscattered field from the exit rays. This method is so simple in concept that there is virtually no restriction on the shape or material loading of the cavity. Numerical results obtained by this method are compared with those for the modal analysis for a circular cylinder terminated by a PEC plate. RCS results for an S-bend circular cylinder generated on the Cray X-MP supercomputer show significant RCS reduction. Some of the limitations and possible extensions of this technique are discussed.
Shooting and bouncing rays - Calculating the RCS of an arbitrarily shaped cavity
NASA Astrophysics Data System (ADS)
Ling, Hao; Chou, Ri-Chee; Lee, Shung-Wu
1989-02-01
A ray-shooting approach is presented for calculating the interior radar cross section (RCS) from a partially open cavity. In the problem considered, a dense grid of rays is launched into the cavity through the opening. The rays bounce from the cavity walls based on the laws of geometrical optics and eventually exit the cavity via the aperture. The ray-bouncing method is based on tracking a large number of rays launched into the cavity through the opening and determining the geometrical optics field associated with each ray by taking into consideration (1) the geometrical divergence factor, (2) polarization, and (3) material loading of the cavity walls. A physical optics scheme is then applied to compute the backscattered field from the exit rays. This method is so simple in concept that there is virtually no restriction on the shape or material loading of the cavity. Numerical results obtained by this method are compared with those for the modal analysis for a circular cylinder terminated by a PEC plate. RCS results for an S-bend circular cylinder generated on the Cray X-MP supercomputer show significant RCS reduction. Some of the limitations and possible extensions of this technique are discussed.
High performance Lyot and PIAA coronagraphy for arbitrarily shaped telescope apertures
Guyon, Olivier; Hinz, Philip M.; Cady, Eric; Belikov, Ruslan; Martinache, Frantz
2014-01-10
Two high-performance coronagraphic approaches compatible with segmented and obstructed telescope pupils are described. Both concepts use entrance pupil amplitude apodization and a combined phase and amplitude focal plane mask to achieve full coronagraphic extinction of an on-axis point source. While the first concept, called Apodized Pupil Complex Mask Lyot Coronagraph (APCMLC), relies on a transmission mask to perform the pupil apodization, the second concept, called Phase-Induced Amplitude Apodization complex mask coronagraph (PIAACMC), uses beam remapping for lossless apodization. Both concepts theoretically offer complete coronagraphic extinction (infinite contrast) of a point source in monochromatic light, with high throughput and sub-λ/D inner working angle, regardless of aperture shape. The PIAACMC offers nearly 100% throughput and approaches the fundamental coronagraph performance limit imposed by first principles. The steps toward designing the coronagraphs for arbitrary apertures are described for monochromatic light. Designs for the APCMLC and the higher performance PIAACMC are shown for several monolith and segmented apertures, such as the apertures of the Subaru Telescope, Giant Magellan Telescope, Thirty Meter Telescope, the European Extremely Large Telescope, and the Large Binocular Telescope. Performance in broadband light is also quantified, suggesting that the monochromatic designs are suitable for use in up to 20% wide spectral bands for ground-based telescopes.
Zhou, H X
1995-01-01
A general method for calculating translational friction and intrinsic viscosity is developed through exploiting relations between hydrodynamics and electrostatics. An approximate relation xi = 6 pi eta 0C between the translational friction coefficient xi of a particle (eta 0: solvent viscosity) and its capacitance C was derived previously. This involved orientationally preaveraging the Oseen tensor, but the result was found to be very accurate. Based on preaveraging, we find that the intrinsic viscosity [eta] of a particle can be estimated from its polarizability alpha through [eta] = 3/4 alpha + 1/4 Vp, where Vp is the volume of the particle. Both the capacitance and the polarizability can be obtained in a single calculation using the boundary-element technique. An efficient approach is thus found for estimating [eta], a quantity that is very useful in practice because of its sensitivity to particle shape but is notoriously difficult to calculate. Illustrative calculations on ellipsoids, cylinders, and dumbbells demonstrate both the accuracy of the approximate relations and the efficiency of the present method. PMID:8599636
NASA Astrophysics Data System (ADS)
Barchanski, Andreas; Clemens, Markus; De Gersem, Herbert; Weiland, Thomas
2006-05-01
In this paper, we extend the scalar-potential finite-difference (SPFD) approach in order to consider arbitrarily shaped time-harmonic field sources. The SPFD approach is commonly used to compute the currents induced by an externally applied magnetic field in regions with weak, heterogeneous conductivities such as, e.g., the human body. We present the extended scalar-potential finite-difference (Ex-SPFD) approach as a two step algorithm. In the first step, the excitation is computed by solving the magnetoquasistatic curl-curl equation on a coarse grid that is well adapted for the field sources. In the second step, the magnetic vector potential is prolongated onto a finer grid and a divergence correction inside the conductor is applied. Using the Maxwell-grid-equations (MGEs) of the finite integration technique, a geometric discretization scheme for Maxwell's equations, this new approach has been implemented in a parallel environment in order to account for the memory-demanding high-resolution anatomy models used for the calculation of induced currents inside the human body. We demonstrate the validity and the improved numerical performance of the new approach for a test case. Finally, an application example of a human exposed to a realistic electromagnetic field source is presented.
Graspable objects shape number processing.
Ranzini, Mariagrazia; Lugli, Luisa; Anelli, Filomena; Carbone, Rossella; Nicoletti, Roberto; Borghi, Anna M
2011-01-01
The field of numerical cognition represents an interesting case for action-based theories of cognition, since number is a special kind of abstract concept. Several studies have shown that within the parietal lobes adjacent neural regions code numerical magnitude and grasping-related information. This anatomical proximity between brain areas involved in number and sensorimotor processes may account for interactions between numerical magnitude and action. In particular, recent studies have demonstrated a causal role of action perception on numerical magnitude processing. If objects are represented in terms of actions (affordances), the causal role of action on number processing should extend to the case of objects affordances. This study investigates the relationship between numbers and objects affordances in two experiments, without (Experiment 1) or with (Experiment 2) the requirement of an action (i.e., participants were asked to hold an object in their hands during the task). The task consisted in repeating aloud the odd or even digit within a pair depending on the type of the preceding or following object. Order of presentation (object-number vs. number-object), Object type (graspable vs. ungraspable), Object size (small vs. large), and Numerical magnitude (small vs. large) were manipulated for each experiment. Experiment 1 showed a facilitation - in terms of quicker responses - for graspable over ungraspable objects preceded by numbers, and an effect of numerical magnitude after the presentation of graspable objects. Experiment 2 demonstrated that the action execution enhanced overall the sensitivity to numerical magnitude, and that at the same time it interfered with the effects of objects affordances on number processing. Overall, these findings demonstrate that numbers and graspable objects are strongly interrelated, supporting the view that abstract concepts may be grounded in the motor experience.
Graspable Objects Shape Number Processing
Ranzini, Mariagrazia; Lugli, Luisa; Anelli, Filomena; Carbone, Rossella; Nicoletti, Roberto; Borghi, Anna M.
2011-01-01
The field of numerical cognition represents an interesting case for action-based theories of cognition, since number is a special kind of abstract concept. Several studies have shown that within the parietal lobes adjacent neural regions code numerical magnitude and grasping-related information. This anatomical proximity between brain areas involved in number and sensorimotor processes may account for interactions between numerical magnitude and action. In particular, recent studies have demonstrated a causal role of action perception on numerical magnitude processing. If objects are represented in terms of actions (affordances), the causal role of action on number processing should extend to the case of objects affordances. This study investigates the relationship between numbers and objects affordances in two experiments, without (Experiment 1) or with (Experiment 2) the requirement of an action (i.e., participants were asked to hold an object in their hands during the task). The task consisted in repeating aloud the odd or even digit within a pair depending on the type of the preceding or following object. Order of presentation (object–number vs. number–object), Object type (graspable vs. ungraspable), Object size (small vs. large), and Numerical magnitude (small vs. large) were manipulated for each experiment. Experiment 1 showed a facilitation – in terms of quicker responses – for graspable over ungraspable objects preceded by numbers, and an effect of numerical magnitude after the presentation of graspable objects. Experiment 2 demonstrated that the action execution enhanced overall the sensitivity to numerical magnitude, and that at the same time it interfered with the effects of objects affordances on number processing. Overall, these findings demonstrate that numbers and graspable objects are strongly interrelated, supporting the view that abstract concepts may be grounded in the motor experience. PMID:22164141
Manual experience shapes object representations.
Yee, Eiling; Chrysikou, Evangelia G; Hoffman, Esther; Thompson-Schill, Sharon L
2013-06-01
How do people represent object meaning? It is now uncontentious that thinking about manipulable objects (e.g., pencils) activates brain regions underlying action. But is this activation part of the meaning of these objects, or is it merely incidental? The research we report here shows that when the hands are engaged in a task involving motions that are incompatible with those used to interact with frequently manipulated objects, it is more difficult to think about those objects--but not harder to think about infrequently manipulated objects (e.g., bookcases). Critically, the amount of manual experience with the object determines the amount of interference. These findings show that brain activity underlying manual action is part of, not peripheral to, the representation of frequently manipulated objects. Further, they suggest that people's ability to think about an object changes dynamically on the basis of the match between their (experience-based) mental representation of its meaning and whatever they are doing at that moment.
NASA Technical Reports Server (NTRS)
MacKenzie, Anne I.; Rao, Sadasiva M.; Baginski, Michael E.
2007-01-01
A pair of basis functions is presented for the surface integral, method of moment solution of scattering by arbitrarily-shaped, three-dimensional dielectric bodies. Equivalent surface currents are represented by orthogonal unit pulse vectors in conjunction with triangular patch modeling. The electric field integral equation is employed with closed geometries for dielectric bodies; the method may also be applied to conductors. Radar cross section results are shown for dielectric bodies having canonical spherical, cylindrical, and cubic shapes. Pulse basis function results are compared to results by other methods.
NASA Technical Reports Server (NTRS)
Mackenzie, Anne I.; Baginski, Michael E.; Rao, Sadasiva M.
2008-01-01
In this work, we present an alternate set of basis functions, each defined over a pair of planar triangular patches, for the method of moments solution of electromagnetic scattering and radiation problems associated with arbitrarily-shaped, closed, conducting surfaces. The present basis functions are point-wise orthogonal to the pulse basis functions previously defined. The prime motivation to develop the present set of basis functions is to utilize them for the electromagnetic solution of dielectric bodies using a surface integral equation formulation which involves both electric and magnetic cur- rents. However, in the present work, only the conducting body solution is presented and compared with other data.
Wang, Xu; Schiavone, Peter
2014-10-08
We propose an elegant and concise general method for the solution of a problem involving the interaction of a screw dislocation and a nano-sized, arbitrarily shaped, elastic inhomogeneity in which the contribution of interface/surface elasticity is incorporated using a version of the Gurtin-Murdoch model. The analytic function inside the arbitrarily shaped inhomogeneity is represented in the form of a Faber series. The real periodic function arising from the contribution of the surface mechanics is then expanded as a Fourier series. The resulting system of linear algebraic equations is solved through the use of simple matrix algebra. When the elastic inhomogeneity represents a hole, our solution method simplifies considerably. Furthermore, we undertake an analytical investigation of the challenging problem of a screw dislocation interacting with two closely spaced nano-sized holes of arbitrary shape in the presence of surface stresses. Our solutions quite clearly demonstrate that the induced elastic fields and image force acting on the dislocation are indeed size-dependent.
Shape-Memory Probe Grasps Small Objects
NASA Technical Reports Server (NTRS)
Angulo, Earl D.
1992-01-01
Shape-memory device removes foreign objects from ear canal, nose, or throat with little risk of damage to tissue. Thin, flexible wire inserted into cavity. Once positioned, it is made to bend into hook, tweezer, or other "remembered" grasping configuration by heating above critical temperature.
NASA Astrophysics Data System (ADS)
Eiselen, Sasia; Riedel, Sebastian; Schmidt, Michael
2014-05-01
Progressive developments in temporal shaping of short laser pulses offer entirely new approaches at influence and investigate laser-matter-interactions. Commonly used parameters for describing the behavior of short or ultrashort pulses or pulse trains are fluence and intensity. However, fluence does not imply any information about the temporal behavior of energy input during specific pulse duration τ while using the pulse intensity as describing parameter is more meaningful. Nevertheless it still is an averaging over pulse duration and no change in intensity can be determined if the temporal pulse shape changes within a certain combination of pulse duration and pulse energy. Using a flexible programmable MOPA fiber laser experimental studies on the impact of temporal energy distribution within one single laser pulse in micro machining applications were therefore carried out. With this laser source a direct modulation of the temporal pulse shape in the nanosecond regime can easily be controlled. Experiments were carried out with moved as well as with un-moved beam resulting in areas and dimples respectively drilling holes. The presented results clearly show that any averaging over pulse duration results in missing information about time-dependent interactions but can at the same time lead to significant differences in ablation results. Thus, resulting surface roughness Sa can be decreased up to 25 % when changing the pulse shape at constant parameters of fluence and pulse peak power at a pulse duration of 30 ns. It can be observed that the combination of an intensity peak and a lower edge within one pulse can lead to increasing ablation efficiency as well as higher ablation quality compared to the commonly used Gaussian-like temporal pulse shape.
NASA Astrophysics Data System (ADS)
Jafari, Nasrin; Azhari, Mojtaba
2016-11-01
In this paper, the stability analysis of moderately thick time-dependent viscoelastic plates with various shapes is studied using the Laplace-Carson transformation and simple hp cloud meshless method. The shear effect of the plate is described by the first order shear deformation theory. The mechanical properties of the materials are supposed to be linear viscoelastic based on the constant bulk modulus. The displacement field is assumed to be the product of two functions, one being a function of geometrical parameters and the other a known exponential function of time. The simple hp cloud method is used for discretization which is based on Kronecker-delta properties. Thus, the essential boundary conditions can be imposed directly. A numerical investigation is made by employing the inverse of Laplace-Carson transformation. The time history of buckling coefficients of viscoelastic plates of various shapes with different boundary conditions is considered. Moreover, a number of numerical results are presented to study the effect of thickness, aspect ratio, different boundary conditions, and various shapes on the time history of buckling coefficients of the viscoelastic plate.
NASA Astrophysics Data System (ADS)
Jafari, Nasrin; Azhari, Mojtaba
2017-08-01
In this paper, the stability analysis of moderately thick time-dependent viscoelastic plates with various shapes is studied using the Laplace-Carson transformation and simple hp cloud meshless method. The shear effect of the plate is described by the first order shear deformation theory. The mechanical properties of the materials are supposed to be linear viscoelastic based on the constant bulk modulus. The displacement field is assumed to be the product of two functions, one being a function of geometrical parameters and the other a known exponential function of time. The simple hp cloud method is used for discretization which is based on Kronecker-delta properties. Thus, the essential boundary conditions can be imposed directly. A numerical investigation is made by employing the inverse of Laplace-Carson transformation. The time history of buckling coefficients of viscoelastic plates of various shapes with different boundary conditions is considered. Moreover, a number of numerical results are presented to study the effect of thickness, aspect ratio, different boundary conditions, and various shapes on the time history of buckling coefficients of the viscoelastic plate.
Object Manipulation Facilitates Kind-Based Object Individuation of Shape-Similar Objects
ERIC Educational Resources Information Center
Kingo, Osman S.; Krojgaard, Peter
2011-01-01
Five experiments investigated the importance of shape and object manipulation when 12-month-olds were given the task of individuating objects representing exemplars of kinds in an event-mapping design. In Experiments 1 and 2, results of the study from Xu, Carey, and Quint (2004, Experiment 4) were partially replicated, showing that infants were…
Object Manipulation Facilitates Kind-Based Object Individuation of Shape-Similar Objects
ERIC Educational Resources Information Center
Kingo, Osman S.; Krojgaard, Peter
2011-01-01
Five experiments investigated the importance of shape and object manipulation when 12-month-olds were given the task of individuating objects representing exemplars of kinds in an event-mapping design. In Experiments 1 and 2, results of the study from Xu, Carey, and Quint (2004, Experiment 4) were partially replicated, showing that infants were…
Retrieval of Shape Characteristics for Buried Objects with GPR Monitoring
NASA Astrophysics Data System (ADS)
Soldovieri, F.; Comite, D.; Galli, A.; Valerio, G.; Barone, P. M.; Lauro, S. E.; Mattei, E.; Pettinelli, E.
2012-04-01
processing allow us to retrieve results again in the form of radargrams for the scattering features of arbitrarily-composed subsurfaces. Once these types of "direct" (measured and/or simulated) radargram data are obtained, the "inverse" problem is then handled, based on a Born approximation to linearize the scattering problem. The targets are represented in terms of anomalies ("contrast function") of dielectric permittivity and conductivity with respect to the properties of a background environment. The analysis of the relevant results for the spatial distribution of the magnitude of the contrast function shows that, in various even-challenging practical cases, this kind of approach is able to properly locate buried objects, also identifying the relevant shape features. [1] D. J. Daniels (Ed.), Ground penetrating radar. IEE Press, 2004. [2] E. Pettinelli, A. Di Matteo, E. Mattei, L. Crocco, F. Soldovieri, J. D. Redman, and A. P. Annan, "GPR response from buried pipes: measurement on field site and tomographic reconstructions," IEEE Trans. Geosci. Remote Sensing, vol. 47, pp. 2639-2645, Aug. 2009. [3] G. Valerio, A. Galli, P. M. Barone, S. E. Lauro, E. Mattei, and E. Pettinelli, "GPR detectability of rocks in a Martian-like shallow subsoil: a numerical approach," Planet. Space Sci., 10 pp., doi: 10.1016/j.pss.2011.12.003, 2011.
Multi-objective optimization shapes ecological variation.
Kaitaniemi, Pekka; Scheiner, Annette; Klemola, Tero; Ruohomäki, Kai
2012-02-22
Ecological systems contain a huge amount of quantitative variation between and within species and locations, which makes it difficult to obtain unambiguous verification of theoretical predictions. Ordinary experiments consider just a few explanatory factors and are prone to providing oversimplified answers because they ignore the complexity of the factors that underlie variation. We used multi-objective optimization (MO) for a mechanistic analysis of the potential ecological and evolutionary causes and consequences of variation in the life-history traits of a species of moth. Optimal life-history solutions were sought for environmental conditions where different life stages of the moth were subject to predation and other known fitness-reducing factors in a manner that was dependent on the duration of these life stages and on variable mortality rates. We found that multi-objective optimal solutions to these conditions that the moths regularly experience explained most of the life-history variation within this species. Our results demonstrate that variation can have a causal interpretation even for organisms under steady conditions. The results suggest that weather and species interactions can act as underlying causes of variation, and MO acts as a corresponding adaptive mechanism that maintains variation in the traits of organisms.
Divided attention limits perception of 3-D object shapes.
Scharff, Alec; Palmer, John; Moore, Cathleen M
2013-02-12
Can one perceive multiple object shapes at once? We tested two benchmark models of object shape perception under divided attention: an unlimited-capacity and a fixed-capacity model. Under unlimited-capacity models, shapes are analyzed independently and in parallel. Under fixed-capacity models, shapes are processed at a fixed rate (as in a serial model). To distinguish these models, we compared conditions in which observers were presented with simultaneous or sequential presentations of a fixed number of objects (The extended simultaneous-sequential method: Scharff, Palmer, & Moore, 2011a, 2011b). We used novel physical objects as stimuli, minimizing the role of semantic categorization in the task. Observers searched for a specific object among similar objects. We ensured that non-shape stimulus properties such as color and texture could not be used to complete the task. Unpredictable viewing angles were used to preclude image-matching strategies. The results rejected unlimited-capacity models for object shape perception and were consistent with the predictions of a fixed-capacity model. In contrast, a task that required observers to recognize 2-D shapes with predictable viewing angles yielded an unlimited capacity result. Further experiments ruled out alternative explanations for the capacity limit, leading us to conclude that there is a fixed-capacity limit on the ability to perceive 3-D object shapes.
Object shape extraction from cluttered bags
NASA Astrophysics Data System (ADS)
Sirakov, Nikolay Metodiev
2017-05-01
The passengers flow at the US airports increased in the recent years. The larger number of passengers demands for lower number of false alarms and higher accuracy of threat detection at the time of baggage screening. This paper presents an algorithm to detect and extract possible explosive containers in X-Ray- CT bags images. The algorithm is composed by three main stages. The 1st one makes the threat container excels among the other objects in the bag image. The 2nd approach: Extracts the SURF features from the query and the bag images; Matches the SURF feature vectors from the two images. The bag image points (pixels), at which the best match is found, define regions of interest (RoI). Different RoI in a bag are identified by separate clusters of points. At the 3rd stage of the algorithm an enlarging active contour (AC) extracts the boundary of every RoI. The starting point of every AC is the mass center of the corresponding cluster of SURF points. The theory is validated on a number of X-ray/CT images. A qualitative comparison with contemporary methods outlines the advantages and the contribution of the present algorithm.
Hydrodynamic interactions between two forced objects of arbitrary shape. II. Relative translation
NASA Astrophysics Data System (ADS)
Goldfriend, Tomer; Diamant, Haim; Witten, Thomas A.
2016-04-01
We study the relative translation of two arbitrarily shaped objects, caused by their hydrodynamic interaction as they are forced through a viscous fluid in the limit of zero Reynolds number. It is well known that in the case of two rigid spheres in an unbounded fluid, the hydrodynamic interaction does not produce relative translation. More generally, such an effective pair-interaction vanishes in configurations with spatial inversion symmetry; for example, an enantiomorphic pair in mirror image positions has no relative translation. We show that the breaking of inversion symmetry by boundaries of the system accounts for the interactions between two spheres in confined geometries, as observed in experiments. The same general principle also provides new predictions for interactions in other object configurations near obstacles. We examine the time-dependent relative translation of two self-aligning objects, extending the numerical analysis of our preceding publication [Goldfriend, Diamant, and Witten, Phys. Fluids 27, 123303 (2015)], 10.1063/1.4936894. The interplay between the orientational interaction and the translational one, in most cases, leads over time to repulsion between the two objects. The repulsion is qualitatively different for self-aligning objects compared to the more symmetric case of uniform prolate spheroids. The separation between the two objects increases with time t as t1 /3 in the former case, and more strongly, as t , in the latter.
Shape and Color Features for Object Recognition Search
NASA Technical Reports Server (NTRS)
Duong, Tuan A.; Duong, Vu A.; Stubberud, Allen R.
2012-01-01
A bio-inspired shape feature of an object of interest emulates the integration of the saccadic eye movement and horizontal layer in vertebrate retina for object recognition search where a single object can be used one at a time. The optimal computational model for shape-extraction-based principal component analysis (PCA) was also developed to reduce processing time and enable the real-time adaptive system capability. A color feature of the object is employed as color segmentation to empower the shape feature recognition to solve the object recognition in the heterogeneous environment where a single technique - shape or color - may expose its difficulties. To enable the effective system, an adaptive architecture and autonomous mechanism were developed to recognize and adapt the shape and color feature of the moving object. The bio-inspired object recognition based on bio-inspired shape and color can be effective to recognize a person of interest in the heterogeneous environment where the single technique exposed its difficulties to perform effective recognition. Moreover, this work also demonstrates the mechanism and architecture of the autonomous adaptive system to enable the realistic system for the practical use in the future.
It's Taking Shape: Shared Object Features Influence Novel Noun Generalizations
ERIC Educational Resources Information Center
Horst, Jessica S.; Twomey, Katherine E.
2013-01-01
Children's early noun vocabularies are dominated by names for shape-based categories. However, along with shape, material and colour are also important features of many early categories. In the current study, we investigate how the number of shared features among objects influences children's novel noun generalizations, explanations for these…
It's Taking Shape: Shared Object Features Influence Novel Noun Generalizations
ERIC Educational Resources Information Center
Horst, Jessica S.; Twomey, Katherine E.
2013-01-01
Children's early noun vocabularies are dominated by names for shape-based categories. However, along with shape, material and colour are also important features of many early categories. In the current study, we investigate how the number of shared features among objects influences children's novel noun generalizations, explanations for these…
Method and system for producing complex-shape objects
Jeantette, Francisco P.; Keicher, David M.; Romero, Joseph A.; Schanwald, Lee P.
2000-01-01
A method and system are provided for producing complex, three-dimensional, net shape objects from a variety of powdered materials. The system includes unique components to ensure a uniform and continuous flow of powdered materials as well as to focus and locate the flow of powdered materials with respect to a laser beam which results in the melting of the powdered material. The system also includes a controller so that the flow of molten powdered materials can map out and form complex, three-dimensional, net-shape objects by layering the molten powdered material. Advantageously, such complex, three-dimensional net-shape objects can be produced having material densities varying from 90% of theoretical to fully dense, as well as a variety of controlled physical properties. Additionally, such complex, three-dimensional objects can be produced from two or more different materials so that the composition of the object can be transitioned from one material to another.
Lloyd-Jones, Toby J.; Roberts, Mark V.; Leek, E. Charles; Fouquet, Nathalie C.; Truchanowicz, Ewa G.
2012-01-01
Little is known about the timing of activating memory for objects and their associated perceptual properties, such as colour, and yet this is important for theories of human cognition. We investigated the time course associated with early cognitive processes related to the activation of object shape and object shape+colour representations respectively, during memory retrieval as assessed by repetition priming in an event-related potential (ERP) study. The main findings were as follows: (1) we identified a unique early modulation of mean ERP amplitude during the N1 that was associated with the activation of object shape independently of colour; (2) we also found a subsequent early P2 modulation of mean amplitude over the same electrode clusters associated with the activation of object shape+colour representations; (3) these findings were apparent across both familiar (i.e., correctly coloured – yellow banana) and novel (i.e., incorrectly coloured - blue strawberry) objects; and (4) neither of the modulations of mean ERP amplitude were evident during the P3. Together the findings delineate the timing of object shape and colour memory systems and support the notion that perceptual representations of object shape mediate the retrieval of temporary shape+colour representations for familiar and novel objects. PMID:23155393
The Shape Bias Is Affected by Differing Similarity among Objects
ERIC Educational Resources Information Center
Tek, Saime; Jaffery, Gul; Swensen, Lauren; Fein, Deborah; Naigles, Letitia R.
2012-01-01
Previous research has demonstrated that visual properties of objects can affect shape-based categorization in a novel-name extension task; however, we still do not know how a relationship between visual properties of objects affects judgments in a novel-name extension task. We examined effects of increased visual similarity among the target and…
Perceived object stability depends on shape and material properties.
Lupo, Julian; Barnett-Cowan, Michael
2015-04-01
Humans can detect whether an unstable object will fall or right itself, suggesting that the visual system can extract an object's center of mass (COM) and relate this to its base of support. While the COM can be approximated by its shape, this assumes uniform density. We created images of computer-generated goblets made of different materials to assess whether the visual system estimates an object's COM from both shape and material properties. The images were either uniformly dense (e.g., glass, gold, etc.) or made of composite materials (e.g., glass and gold) and positioned upright or upside-down near a table ledge. We compared each goblet's critical angle (CA), the angle at which each goblet is equally likely to fall or right itself, to the perceived CA in a two-alternative-forced-choice paradigm. Participants also rank-ordered 20 materials by density on a questionnaire. The results show that observers accurately estimate the CA for all goblets and are sensitive to subtle changes of an object's COM with change in shape and composite material properties. Importantly, rated density - as measured from the questionnaire - and true material density were positively correlated, suggesting that humans might maintain a representation of relative material density with which to assess object stability. We conclude that the brain is able to assess an object's behavior in a gravitational environment by forming a reliable assessment of an object's COM from both its geometric shape and material properties. Copyright © 2015 Elsevier Ltd. All rights reserved.
2011-08-15
small numbers of sensed features associated with locations on the target geometry, although we plan to consider larger point clouds , or even...Correspondence Problem 7. Shapelets 8. Point Clouds 9. 3D Shape Reconstruction and Shape from Motion 10. Probability and Statistics of Shape...ideas can be used to align ladar data to CAD models and to speed various algorithms for matching point clouds to target models. In some cases it can be
Objective models of compressed breast shapes undergoing mammography.
Feng, Steve Si Jia; Patel, Bhavika; Sechopoulos, Ioannis
2013-03-01
To develop models of compressed breasts undergoing mammography based on objective analysis, that are capable of accurately representing breast shapes in acquired clinical images and generating new, clinically realistic shapes. An automated edge detection algorithm was used to catalogue the breast shapes of clinically acquired cranio-caudal (CC) and medio-lateral oblique (MLO) view mammograms from a large database of digital mammography images. Principal component analysis (PCA) was performed on these shapes to reduce the information contained within the shapes to a small number of linearly independent variables. The breast shape models, one of each view, were developed from the identified principal components, and their ability to reproduce the shape of breasts from an independent set of mammograms not used in the PCA, was assessed both visually and quantitatively by calculating the average distance error (ADE). The PCA breast shape models of the CC and MLO mammographic views based on six principal components, in which 99.2% and 98.0%, respectively, of the total variance of the dataset is contained, were found to be able to reproduce breast shapes with strong fidelity (CC view mean ADE = 0.90 mm, MLO view mean ADE = 1.43 mm) and to generate new clinically realistic shapes. The PCA models based on fewer principal components were also successful, but to a lesser degree, as the two-component model exhibited a mean ADE = 2.99 mm for the CC view, and a mean ADE = 4.63 mm for the MLO view. The four-component models exhibited a mean ADE = 1.47 mm for the CC view and a mean ADE = 2.14 mm for the MLO view. Paired t-tests of the ADE values of each image between models showed that these differences were statistically significant (max p-value = 0.0247). Visual examination of modeled breast shapes confirmed these results. Histograms of the PCA parameters associated with the six principal components were fitted with Gaussian distributions. The six-component model was also used
Objective models of compressed breast shapes undergoing mammography
Feng, Steve Si Jia; Patel, Bhavika; Sechopoulos, Ioannis
2013-03-15
Purpose: To develop models of compressed breasts undergoing mammography based on objective analysis, that are capable of accurately representing breast shapes in acquired clinical images and generating new, clinically realistic shapes. Methods: An automated edge detection algorithm was used to catalogue the breast shapes of clinically acquired cranio-caudal (CC) and medio-lateral oblique (MLO) view mammograms from a large database of digital mammography images. Principal component analysis (PCA) was performed on these shapes to reduce the information contained within the shapes to a small number of linearly independent variables. The breast shape models, one of each view, were developed from the identified principal components, and their ability to reproduce the shape of breasts from an independent set of mammograms not used in the PCA, was assessed both visually and quantitatively by calculating the average distance error (ADE). Results: The PCA breast shape models of the CC and MLO mammographic views based on six principal components, in which 99.2% and 98.0%, respectively, of the total variance of the dataset is contained, were found to be able to reproduce breast shapes with strong fidelity (CC view mean ADE = 0.90 mm, MLO view mean ADE = 1.43 mm) and to generate new clinically realistic shapes. The PCA models based on fewer principal components were also successful, but to a lesser degree, as the two-component model exhibited a mean ADE = 2.99 mm for the CC view, and a mean ADE = 4.63 mm for the MLO view. The four-component models exhibited a mean ADE = 1.47 mm for the CC view and a mean ADE = 2.14 mm for the MLO view. Paired t-tests of the ADE values of each image between models showed that these differences were statistically significant (max p-value = 0.0247). Visual examination of modeled breast shapes confirmed these results. Histograms of the PCA parameters associated with the six principal components were fitted with Gaussian distributions. The six
Reconstruction of shapes of near symmetric and asymmetric objects
Pizlo, Zygmunt; Sawada, Tadamasa; Li, Yunfeng
2013-03-26
A system processes 2D images of 2D or 3D objects, creating a model of the object that is consistent with the image and as veridical as the perception of the 2D image by humans. Vertices of the object that are hidden in the image are recovered by using planarity and symmetry constraints. The 3D shape is recovered by maximizing 3D compactness of the recovered object and minimizing its surface area. In some embodiments, these two criteria are weighted by using the geometric mean.
Reconstruction of shapes of near symmetric and asymmetric objects
Pizlo, Zygmunt; Sawada, Tadamasa; Li, Yunfeng
2013-03-26
A system processes 2D images of 2D or 3D objects, creating a model of the object that is consistent with the image and as veridical as the perception of the 2D image by humans. Vertices of the object that are hidden in the image are recovered by using planarity and symmetry constraints. The 3D shape is recovered by maximizing 3D compactness of the recovered object and minimizing its surface area. In some embodiments, these two criteria are weighted by using the geometric mean.
The Perceived Size and Shape of Objects in Peripheral Vision
Baldwin, Joseph; Burleigh, Alistair; Ruta, Nicole
2016-01-01
Little is known about how we perceive the size and shape of objects in far peripheral vision. Observations made during an artistic study of visual space suggest that objects appear smaller and compressed in the periphery compared with central vision. To test this, we conducted three experiments. In Experiment 1, we asked participants to draw how a set of peripheral discs appeared when viewed peripherally without time or eye movement constraints. In Experiment 2, we used the method of constant stimuli to measure when a briefly presented peripheral stimulus appeared bigger or smaller compared with a central fixated one. In Experiment 3, we measured how accurate participants were in discriminating shapes presented briefly in the periphery. In Experiment 1, the peripheral discs were reported as appearing significantly smaller than the central disc, and as having an elliptical or polygonal contour. In Experiment 2, participants judged the size of peripheral discs as being significantly smaller when compared with the central disc across most of the peripheral field, and in Experiment 3, participants were quite accurate in reporting the shape of the peripheral object, except in the far periphery. Our results show that objects in the visual periphery are perceived as diminished in size when presented for long and brief exposures, suggesting diminution is an intrinsic feature of the structure of the visual space. Shape distortions, however, are reported only with longer exposures. PMID:27698981
The effect of object shape and laser beam shape on lidar system resolution
NASA Astrophysics Data System (ADS)
Cheng, Hongchang; Wang, Jingyi; Ke, Jun
2016-06-01
In a LIDAR system, a pulsed laser beam is propagated to a scene, and then reflected back by objects. Ideally if the beam diameter and the pulse width are close to zero, then the reflected beam in time domain is similar to a delta function, which can accurately locate an object's position. However, in a practical system, the beam has finite size. Therefore, even if the pulse width is small, an object shape will make the reflected beam stretched along the time axis, then affect system resolution. In this paper, we assume the beam with Gaussian shape. The beam can be formulated as a delta function convolved with a shape function, such as a rectangular function, in time domain. Then the reflected beam can be defined as a system response function convolved with the shape function. We use symmetric objects to analyze the reflected beam. Corn, sphere, and cylinder objects are used to find a LIDAR system's response function. The case for large beam size is discussed. We assume the beam shape is similar to a plane wave. With this assumption, we get the simplified LIDAR system response functions for the three kinds of objects. Then we use tiny spheres to emulate an arbitrary object, and study its effect to the returned beam.
Lee, Haemy; Wallraven, Christian
2013-03-01
Humans are experts at shape processing. This expertise has been learned and fine tuned by actively manipulating and perceiving thousands of objects during development. Therefore, shape processing possesses an active component and a perceptual component. Here, we investigate both components in six experiments in which participants view and/or interact with novel, parametrically defined 3D objects using a touch-screen interface. For probing shape processing, we use a similarity rating task. In Experiments 1-3, we show that active manipulation leads to a better perceptual reconstruction of the physical parameter space than judging rotating objects, or passively viewing someone else's exploration pattern. In Experiment 4, we exploit object constancy-the fact that the visual system assumes that objects do not change their identity during manipulation. We show that slow morphing of an object during active manipulation systematically biases similarity ratings-despite the participants being unaware of the morphing. Experiments 5 and 6 investigate the time course of integrating shape information by restricting the morphing to the first and second half of the trial only. Interestingly, the results indicate that participants do not seem to integrate shape information beyond 5 s of exploration time. Finally, Experiment 7 uses a secondary task that suggests that the previous results are not simply due to lack of attention during the later parts of the trial. In summary, our results demonstrate the advantage of active manipulation for shape processing and indicate a continued, perceptual integration of complex shape information within a time window of a few seconds during object interactions.
2011-01-01
Background Kulldorff's spatial scan statistic has been one of the most widely used statistical methods for automatic detection of clusters in spatial data. One limitation of this method lies in the fact that it has to rely on scan windows with predefined shapes in the search process, and therefore it cannot detect cluster with arbitrary shapes. We employ a new neighbor-expanding approach and introduce two new algorithms to detect cluster with arbitrary shapes in spatial data. These two algorithms are called the maximum-likelihood-first (MLF) algorithm and non-greedy growth (NGG) algorithm. We then compare the performance of these two new algorithms with the spatial scan statistic (SaTScan), Tango's flexibly shaped spatial scan statistic (FlexScan), and Duczmal's simulated annealing (SA) method using two datasets. Furthermore, we utilize the methods to examine clusters of murine typhus cases in South Texas from 1996 to 2006. Result When compared with the SaTScan and FlexScan method, the two new algorithms were more flexible and sensitive in detecting the clusters with arbitrary shapes in the test datasets. Clusters detected by the MLF algorithm are statistically more significant than those detected by the NGG algorithm. However, the NGG algorithm appears to be more stable when there are no extreme cluster patterns in the data. For the murine typhus data in South Texas, a large portion of the detected clusters were located in coastal counties where environmental conditions and socioeconomic status of some population groups were at a disadvantage when compared with those in other counties with no clusters of murine typhus cases. Conclusion The two new algorithms are effective in detecting the location and boundary of spatial clusters with arbitrary shapes. Additional research is needed to better understand the etiology of the concentration of murine typhus cases in some counties in south Texas. PMID:21453514
Shape, motion, and optical cues to stiffness of elastic objects.
Paulun, Vivian C; Schmidt, Filipp; van Assen, Jan Jaap R; Fleming, Roland W
2017-01-01
Nonrigid materials, such as jelly, rubber, or sponge move and deform in distinctive ways depending on their stiffness. Which cues do we use to infer stiffness? We simulated cubes of varying stiffness and optical appearance (e.g., wood, metal, wax, jelly) being subjected to two kinds of deformation: (a) a rigid cylinder pushing downwards into the cube to various extents (shape change, but little motion: shape dominant), (b) a rigid cylinder retracting rapidly from the cube (same initial shapes, differences in motion: motion dominant). Observers rated the apparent softness/hardness of the cubes. In the shape-dominant condition, ratings mainly depended on how deeply the rod penetrated the cube and were almost unaffected by the cube's intrinsic physical properties. In contrast, in the motion-dominant condition, ratings varied systematically with the cube's intrinsic stiffness, and were less influenced by the extent of the perturbation. We find that both results are well predicted by the absolute magnitude of deformation, suggesting that when asked to judge stiffness, observers resort to simple heuristics based on the amount of deformation. Softness ratings for static, unperturbed cubes varied substantially and systematically depending on the optical properties. However, when animated, the ratings were again dominated by the extent of the deformation, and the effect of optical appearance was negligible. Together, our results suggest that to estimate stiffness, the visual system strongly relies on measures of the extent to which an object changes shape in response to forces.
Scanning freeform objects by combining shape from silhouette and shape from line structured light
NASA Astrophysics Data System (ADS)
Xiong, Hanwei; Xu, Jun; Xu, Chenxi; Pan, Ming
2014-12-01
Freeform shape is usually designed by reverse engineering method thorough a 3D scanner, which is often expensive to most persons. The paper proposes a new scanning system combining shape from structured light and shape from silhouette, which can be implemented easily with low cost. The two methods are very complementary. For shape from silhouette, it can capture correct topological information of the object and obtain a closed envelop, and for shape from hand-held laser line, precise point clouds with some holes can be obtained. To gain their complementary advantages, a new data fusion strategy based a mesh energy functional is proposed to integrate the information from the two scanning methods, in which the points resulted from laser light will attract closed envelop from silhouette. After fusion, the precision of shape from silhouette is increased, and the topological error of shape from structured light is corrected. The design details are introduced, and a toy model is used to test the new method, which is difficult to scan using other systems. The test results proof the validity of the new method.
Shape determination of unidimensional objects: the virtual image correlation method
NASA Astrophysics Data System (ADS)
Francois, M.; Semin, B.; Auradou, H.; Vatteville, J.
2010-06-01
The proposed method, named Virtual Image Correlation, allows one to identify an analytical expression of the shape of a curvilinear object from its image. It uses a virtual beam, whose curvature field is expressed as a truncated mathematical series. The virtual beam width only needs to be close to the physical one; its gray level (in the transverse direction) is bell-shaped. The method consists in finding the coefficients of the series for which the correlation between physical and virtual beams is the best. The accuracy and the robustness of the method is shown by the mean of two examples. The first details a Young’s modulus identification from a cantilever beam image. The second is relative to a thermal plume image, that have a weak contrast and a lot of noise.
Introducing shape constraints into object-based traveltime tomography
NASA Astrophysics Data System (ADS)
Gaullier, G.; Charbonnier, P.; Heitz, F.; Côte, P.
2016-09-01
Traveltime tomography is a difficult, ill-posed reconstruction problem due to the nonlinearity of the forward model and the limited number of measurements usually available. In such an adverse situation, pixel-based regularization methods are generally unable to provide satisfactory reconstructions. In this paper we propose a novel object-based reconstruction method that introduces prior information about the shape of the structures to be reconstructed, which yields high quality geoacoustic inversion. The proposed method approaches the forward model by a series of linear problems, leading to a sequence of minimizations during which the shape prior is introduced. The method is demonstrated on synthetic and real data, collected on a specific bench dedicated to non-destructive testing of civil engineering structures.
Invariant visual object recognition and shape processing in rats
Zoccolan, Davide
2015-01-01
Invariant visual object recognition is the ability to recognize visual objects despite the vastly different images that each object can project onto the retina during natural vision, depending on its position and size within the visual field, its orientation relative to the viewer, etc. Achieving invariant recognition represents such a formidable computational challenge that is often assumed to be a unique hallmark of primate vision. Historically, this has limited the invasive investigation of its neuronal underpinnings to monkey studies, in spite of the narrow range of experimental approaches that these animal models allow. Meanwhile, rodents have been largely neglected as models of object vision, because of the widespread belief that they are incapable of advanced visual processing. However, the powerful array of experimental tools that have been developed to dissect neuronal circuits in rodents has made these species very attractive to vision scientists too, promoting a new tide of studies that have started to systematically explore visual functions in rats and mice. Rats, in particular, have been the subjects of several behavioral studies, aimed at assessing how advanced object recognition and shape processing is in this species. Here, I review these recent investigations, as well as earlier studies of rat pattern vision, to provide an historical overview and a critical summary of the status of the knowledge about rat object vision. The picture emerging from this survey is very encouraging with regard to the possibility of using rats as complementary models to monkeys in the study of higher-level vision. PMID:25561421
Freud, Erez; Ganel, Tzvi; Avidan, Galia; Gilaie-Dotan, Sharon
2016-03-01
According to the two visual systems model, the cortical visual system is segregated into a ventral pathway mediating object recognition, and a dorsal pathway mediating visuomotor control. In the present study we examined whether the visual control of action could develop normally even when visual perceptual abilities are compromised from early childhood onward. Using his fingers, LG, an individual with a rare developmental visual object agnosia, manually estimated (perceptual condition) the width of blocks that varied in width and length (but not in overall size), or simply picked them up across their width (grasping condition). LG's perceptual sensitivity to target width was profoundly impaired in the manual estimation task compared to matched controls. In contrast, the sensitivity to object shape during grasping, as measured by maximum grip aperture (MGA), the time to reach the MGA, the reaction time and the total movement time were all normal in LG. Further analysis, however, revealed that LG's sensitivity to object shape during grasping emerged at a later time stage during the movement compared to controls. Taken together, these results demonstrate a dissociation between action and perception of object shape, and also point to a distinction between different stages of the grasping movement, namely planning versus online control. Moreover, the present study implies that visuomotor abilities can develop normally even when perceptual abilities developed in a profoundly impaired fashion.
Phasing arbitrarily sampled multidimensional NMR data
NASA Astrophysics Data System (ADS)
Gledhill, John M.; Wand, A. Joshua
2007-08-01
The recent re-introduction of the two-dimensional Fourier transformation (2D-FT) has allows for the transformation of arbitrarily sampled time domain signals. In this respect, radial sampling, where two incremented time dimensions ( t1 and t2) are sampled such that t1 = τcos α and t2 = τsin α, is especially appealing because of the relatively small leakage artifacts that occur upon Fourier transformation. Unfortunately radially sampled time domain data results in a fundamental artifact in the frequency domain manifested as a ridge of intensity extending through the peak positions perpendicular to +/- the radial sampling angle. Successful removal of the ridge artifacts using existing algorithms requires absorptive line shapes. Here we present two procedures for retrospective phase correction of arbitrarily sampled data.
Optical apparatus for laser scattering by objects having complex shapes
Ellingson, William A.; Visher, Robert J.
2006-11-14
Apparatus for observing and measuring in realtime surface and subsurface characteristics of objects having complex shapes includes an optical fiber bundle having first and second opposed ends. The first end includes a linear array of fibers, where the ends of adjacent fibers are in contact and are aligned perpendicular to the surface of the object being studied. The second ends of some of the fibers are in the form of a polished ferrule forming a multi-fiber optical waveguide for receiving laser light. The second ends of the remaining fibers are formed into a linear array suitable for direct connection to a detector, such as a linear CMOS-based optical detector. The output data is analyzed using digital signal processing for the detection of anomalies such as cracks, voids, inclusions and other defects.
Shape Recognition Of Complex Objects By Syntactical Primitives
NASA Astrophysics Data System (ADS)
Lenger, D.; Cipovic, H.
1985-04-01
The paper describes a pattern recognition method based on syntactic image analysis applicable in autonomous systems of robot vision for the purpose of pattern detection or classification. The discrimination of syntactic elements is realized by polygonal approximation of contours employing a very fast algorithm based upon coding, local pixel logic and methods of choice instead of numerical methods. Semantic information is derived from attributes calculated from the filtered shape vector. No a priori information on image objects is required, and the choice of starting point is determined by finding the significant directions on the shape vector. The radius of recognition sphere is minimum Euclidian distance, i.e. maximum similarity between the unknown model and each individual grammar created in the learning phase. By keeping information on derivations of individual syntactic elements, an alternative of parsing recognition is left. The analysis is very flexible, and permits the recognition of highly distorted or even partially visible objects. The output from syntactic analyzer is the measure of irregularity, and the method is thus applicable in any application where sample deformation is being examined.
Shape detection of Gaborized outline versions of everyday objects
Sassi, Michaël; Machilsen, Bart; Wagemans, Johan
2012-01-01
We previously tested the identifiability of six versions of Gaborized outlines of everyday objects, differing in the orientations assigned to elements inside and outside the outline. We found significant differences in identifiability between the versions, and related a number of stimulus metrics to identifiability [Sassi, M., Vancleef, K., Machilsen, B., Panis, S., & Wagemans, J. (2010). Identification of everyday objects on the basis of Gaborized outline versions. i-Perception, 1(3), 121–142]. In this study, after retesting the identifiability of new variants of three of the stimulus versions, we tested their robustness to local orientation jitter in a detection experiment. In general, our results replicated the key findings from the previous study, and allowed us to substantiate our earlier interpretations of the effects of our stimulus metrics and of the performance differences between the different stimulus versions. The results of the detection task revealed a different ranking order of stimulus versions than the identification task. By examining the parallels and differences between the effects of our stimulus metrics in the two tasks, we found evidence for a trade-off between shape detectability and identifiability. The generally simple and smooth shapes that yield the strongest contour integration and most robust detectability tend to lack the distinguishing features necessary for clear-cut identification. Conversely, contours that do contain such identifying features tend to be inherently more complex and, therefore, yield weaker integration and less robust detectability. PMID:23483752
Invariant visual object recognition and shape processing in rats.
Zoccolan, Davide
2015-05-15
Invariant visual object recognition is the ability to recognize visual objects despite the vastly different images that each object can project onto the retina during natural vision, depending on its position and size within the visual field, its orientation relative to the viewer, etc. Achieving invariant recognition represents such a formidable computational challenge that is often assumed to be a unique hallmark of primate vision. Historically, this has limited the invasive investigation of its neuronal underpinnings to monkey studies, in spite of the narrow range of experimental approaches that these animal models allow. Meanwhile, rodents have been largely neglected as models of object vision, because of the widespread belief that they are incapable of advanced visual processing. However, the powerful array of experimental tools that have been developed to dissect neuronal circuits in rodents has made these species very attractive to vision scientists too, promoting a new tide of studies that have started to systematically explore visual functions in rats and mice. Rats, in particular, have been the subjects of several behavioral studies, aimed at assessing how advanced object recognition and shape processing is in this species. Here, I review these recent investigations, as well as earlier studies of rat pattern vision, to provide an historical overview and a critical summary of the status of the knowledge about rat object vision. The picture emerging from this survey is very encouraging with regard to the possibility of using rats as complementary models to monkeys in the study of higher-level vision. Copyright © 2015 The Author. Published by Elsevier B.V. All rights reserved.
Genetic Algorithms Applied to Multi-Objective Aerodynamic Shape Optimization
NASA Technical Reports Server (NTRS)
Holst, Terry L.
2005-01-01
A genetic algorithm approach suitable for solving multi-objective problems is described and evaluated using a series of aerodynamic shape optimization problems. Several new features including two variations of a binning selection algorithm and a gene-space transformation procedure are included. The genetic algorithm is suitable for finding Pareto optimal solutions in search spaces that are defined by any number of genes and that contain any number of local extrema. A new masking array capability is included allowing any gene or gene subset to be eliminated as decision variables from the design space. This allows determination of the effect of a single gene or gene subset on the Pareto optimal solution. Results indicate that the genetic algorithm optimization approach is flexible in application and reliable. The binning selection algorithms generally provide Pareto front quality enhancements and moderate convergence efficiency improvements for most of the problems solved.
Genetic Algorithms Applied to Multi-Objective Aerodynamic Shape Optimization
NASA Technical Reports Server (NTRS)
Holst, Terry L.
2004-01-01
A genetic algorithm approach suitable for solving multi-objective optimization problems is described and evaluated using a series of aerodynamic shape optimization problems. Several new features including two variations of a binning selection algorithm and a gene-space transformation procedure are included. The genetic algorithm is suitable for finding pareto optimal solutions in search spaces that are defined by any number of genes and that contain any number of local extrema. A new masking array capability is included allowing any gene or gene subset to be eliminated as decision variables from the design space. This allows determination of the effect of a single gene or gene subset on the pareto optimal solution. Results indicate that the genetic algorithm optimization approach is flexible in application and reliable. The binning selection algorithms generally provide pareto front quality enhancements and moderate convergence efficiency improvements for most of the problems solved.
Infants' Individuation of Rigid and Plastic Objects Based on Shape
ERIC Educational Resources Information Center
Schaub, Simone; Bertin, Evelyn; Cacchione, Trix
2013-01-01
Recent research suggests that 12-month-old infants use shape to individuate the number of objects present in a scene. This study addressed the question of whether infants would also rely on shape when shape is only a temporary attribute of an object. Specifically, we investigated whether infants realize that shape changes reliably indicate…
Infants' Individuation of Rigid and Plastic Objects Based on Shape
ERIC Educational Resources Information Center
Schaub, Simone; Bertin, Evelyn; Cacchione, Trix
2013-01-01
Recent research suggests that 12-month-old infants use shape to individuate the number of objects present in a scene. This study addressed the question of whether infants would also rely on shape when shape is only a temporary attribute of an object. Specifically, we investigated whether infants realize that shape changes reliably indicate…
Parts and Relations in Young Children's Shape-Based Object Recognition
ERIC Educational Resources Information Center
Augustine, Elaine; Smith, Linda B.; Jones, Susan S.
2011-01-01
The ability to recognize common objects from sparse information about geometric shape emerges during the same period in which children learn object names and object categories. Hummel and Biederman's (1992) theory of object recognition proposes that the geometric shapes of objects have two components--geometric volumes representing major object…
Assembly of objects with not fully predefined shapes
NASA Technical Reports Server (NTRS)
Arlotti, M. A.; Dimartino, V.
1989-01-01
An assembly problem in a non-deterministic environment, i.e., where parts to be assembled have unknown shape, size and location, is described. The only knowledge used by the robot to perform the assembly operation is given by a connectivity rule and geometrical constraints concerning parts. Once a set of geometrical features of parts has been extracted by a vision system, applying such a rule allows the dtermination of the composition sequence. A suitable sensory apparatus allows the control the whole operation.
Press to grasp: how action dynamics shape object categorization.
Triberti, Stefano; Repetto, Claudia; Costantini, Marcello; Riva, Giuseppe; Sinigaglia, Corrado
2016-03-01
Action and object are deeply linked to each other. Not only can viewing an object influence an ongoing action, but motor representations of action can also influence visual categorization of objects. It is tempting to assume that this influence is effector-specific. However, there is indirect evidence suggesting that this influence may be related to the action goal and not just to the effector involved in achieving it. This paper aimed, for the first time, to tackle this issue directly. Participants were asked to categorize different objects in terms of the effector (e.g. hand or foot) typically used to act upon them. The task was delivered before and after a training session in which participants were instructed either just to press a pedal with their foot or to perform the same foot action with the goal of guiding an avatar's hand to grasp a small ball. Results showed that pressing a pedal to grasp a ball influenced how participants correctly identified graspable objects as hand-related ones, making their responses more uncertain than before the training. Just pressing a pedal did not have any similar effect. This is evidence that the influence of action on object categorization can be goal-related rather than effector-specific.
Welder, A N; Graham, S A
2001-01-01
This study examined the influence of object labels and shape similarity on 16- to 21-month-old infants' inductive inferences. In three experiments, a total of 144 infants were presented with novel target objects with or without a nonobvious property, followed by test objects that varied in shape similarity to the target. When objects were not labeled, infants generalized the nonobvious property to test objects that were highly similar in shape (Experiment 1). When objects were labeled with novel nouns, infants relied both on shape similarity and shared labels to generalize properties (Experiment 2). Finally, when objects were labeled with familiar nouns, infants generalized the properties to those objects that shared the same label, regardless of shape similarity (Experiment 3). The results of these experiments delineate the role of perceptual similarity and conceptual information in guiding infants' inductive inferences.
Shape Matching Of Two-Dimensional Occluded Objects
NASA Astrophysics Data System (ADS)
Fong, Yu-Shan; Chu, Jwo-Liang
1987-10-01
Recognition of partially occluded object is a desirable function in a computer vision system, especially one employed in an industrial automation environment. In this controlled environment, the objects to be recognized can be constrained to a relatively flat region (plane of image), and thus be easily modelled by polygons. This paper studies issues in such a computer vision system and presents algorithms for the various processes involved in occluded polygon matching and recognition. The recognition process is carried out by model matching. The scene may contain unknown model objects which may overlap or touch each other, giving rise to partial occlusion. Both the model and the scene objects are represented by their polygon approximations. Features used for matching are extracted from line segments connecting all possible pairs of vertices in the polygon. They are: vertex types at two ends of line segment, angles of these vertices, line type, and line length. A polygon clipping algorithm based on geometrical properties is used to determine the types of line segments. We also develop a context-free grammar for recognizing line types. To speed up the recognition process, only priority features are used in the initial matching. The priority features are identified after some analysis of the geometrical properties of polygons with occlusion. A consistency check also reduces the pool of candidates for matching. The matching algorithm superposes the model object on the scene along line segments in sequence and checks the dissimilarity between the region enclosed by the scene polygon and the region enclosed by the model polygon appearing in the scene. A dissimilarity measure based on the phenomenon of light illumination and the theory of fuzzy subset has been designed to measure the edge consistency between the scene and candidate model to select the best possible fit.
Multi-objective aerodynamic shape optimization of small livestock trailers
NASA Astrophysics Data System (ADS)
Gilkeson, C. A.; Toropov, V. V.; Thompson, H. M.; Wilson, M. C. T.; Foxley, N. A.; Gaskell, P. H.
2013-11-01
This article presents a formal optimization study of the design of small livestock trailers, within which the majority of animals are transported to market in the UK. The benefits of employing a headboard fairing to reduce aerodynamic drag without compromising the ventilation of the animals' microclimate are investigated using a multi-stage process involving computational fluid dynamics (CFD), optimal Latin hypercube (OLH) design of experiments (DoE) and moving least squares (MLS) metamodels. Fairings are parameterized in terms of three design variables and CFD solutions are obtained at 50 permutations of design variables. Both global and local search methods are employed to locate the global minimum from metamodels of the objective functions and a Pareto front is generated. The importance of carefully selecting an objective function is demonstrated and optimal fairing designs, offering drag reductions in excess of 5% without compromising animal ventilation, are presented.
Sharp and round shapes of seen objects have distinct influences on vowel and consonant articulation.
Vainio, L; Tiainen, M; Tiippana, K; Rantala, A; Vainio, M
2017-07-01
The shape and size-related sound symbolism phenomena assume that, for example, the vowel [i] and the consonant [t] are associated with sharp-shaped and small-sized objects, whereas [ɑ] and [m] are associated with round and large objects. It has been proposed that these phenomena are mostly based on the involvement of articulatory processes in representing shape and size properties of objects. For example, [i] might be associated with sharp and small objects, because it is produced by a specific front-close shape of articulators. Nevertheless, very little work has examined whether these object properties indeed have impact on speech sound vocalization. In the present study, the participants were presented with a sharp- or round-shaped object in a small or large size. They were required to pronounce one out of two meaningless speech units (e.g., [i] or [ɑ]) according to the size or shape of the object. We investigated how a task-irrelevant object property (e.g., the shape when responses are made according to size) influences reaction times, accuracy, intensity, fundamental frequency, and formant 1 and formant 2 of vocalizations. The size did not influence vocal responses but shape did. Specifically, the vowel [i] and consonant [t] were vocalized relatively rapidly when the object was sharp-shaped, whereas [u] and [m] were vocalized relatively rapidly when the object was round-shaped. The study supports the view that the shape-related sound symbolism phenomena might reflect mapping of the perceived shape with the corresponding articulatory gestures.
NASA Astrophysics Data System (ADS)
Ning, Xiaojuan; Wang, Yinghui; Meng, Weiliang; Zhang, Xiaopeng
2016-10-01
To understand and recognize the three-dimensional (3-D) objects represented as point cloud data, we use an optimized shape semantic graph (SSG) to describe 3-D objects. Based on the decomposed components of an object, the boundary surface of different components and the topology of components, the SSG gives a semantic description that is consistent with human vision perception. The similarity measurement of the SSG for different objects is effective for distinguishing the type of object and finding the most similar one. Experiments using a shape database show that the SSG is valuable for capturing the components of the objects and the corresponding relations between them. The SSG is not only suitable for an object without any loops but also appropriate for an object with loops to represent the shape and the topology. Moreover, a two-step progressive similarity measurement strategy is proposed to effectively improve the recognition rate in the shape database containing point-sample data.
Shape measurements of microscopic objects using computational shear interferometry
NASA Astrophysics Data System (ADS)
Agour, Mostafa; Falldorf, Claas; Bergmann, Ralf B.
2016-03-01
We present an efficient and less time consuming implementation of Computational Shear Interferometry (CoSI) by applying a smoothness on the assigned wave field. The method is used to recover the three dimensional form of a micro injection molded part from a set of shear measurements. For this purpose, six shear experiments have been recorded with the shears varying in orientation and magnitude. Varying the shears orientation and magnitude is applied using a setup consisting of a 4f filter with a reflective phase-only spatial light modulator (SLM) in the corresponding Fourier plane. The SLM is used as an electronic diffraction grating with a blazed structure. Based on the birefringent properties of the SLM two orthogonally polarized images, one diffracted and one reflected, appear on the camera sensor and produce shear interferograms. The shift between the images depends on the period and the orientation of the blazed grating. From shear interferograms, the phase of light diffracted by the object is reconstructed by CoSI. Thus the height map of the object is determined.
Shapes and sounds as self-objects in learning geography.
Baum, E A
1978-01-01
The pleasure which some children find in maps and map reading is manifold in origin. Children cathect patterns of configuration and color and derive joy from the visual mastery of these. This gratification is enhanced by the child's knowledge that the map represents something bigger than and external to itself. Likewise, some children take pleasure in the pronunciation of names themselves. The phonetic transcription of multisyllabic names is often a plearurable challenge. The vocalized name has its origin in the self, becomes barely external to self, and is self-monitored. Thus, in children both the configurations and the vocalizations associated with map reading have the properties of "self=objects" (Kohut, 1971). From the author's observation the delight which some children take in sounding out geographic names on a map may, in some instances, indicate pre-existing gratifying sound associations. Childish amusement in punning on cognomens may be an even greater stimulant for learning than visual configurations or artificial cognitive devices.
von der Emde, Gerhard; Fetz, Steffen
2007-09-01
In the absence of light, the weakly electric fish Gnathonemus petersii detects and distinguishes objects in the environment through active electrolocation. In order to test which features of an object the fish use under these conditions to discriminate between differently shaped objects, we trained eight individuals in a food-rewarded, two-alternative, forced-choice procedure. All fish learned to discriminate between two objects of different shapes and volumes. When new object combinations were offered in non-rewarded test trials, fish preferred those objects that resembled the one they had been trained to (S+) and avoided objects resembling the one that had not been rewarded (S-). For a decision, fish paid attention to the relative differences between the two objects they had to discriminate. For discrimination, fish used several object features, the most important ones being volume, material and shape. The importance of shape was demonstrated by reducing the objects to their 3-dimensional contours, which sufficed for the fish to distinguish differently shaped objects. Our results also showed that fish attended strongly to the feature ;volume', because all individuals tended to avoid the larger one of two objects. When confronted with metal versus plastic objects, all fish avoided metal and preferred plastic objects, irrespective of training. In addition to volume, material and shape, fish attended to additional parameters, such as corners or rounded edges. When confronted with two unknown objects, fish weighed up the positive and negative properties of these novel objects and based their decision on the outcome of this comparison. Our results suggest that fish are able to link and assemble local features of an electrolocation pattern to construct a representation of an object, suggesting that some form of a feature extraction mechanism enables them to solve a complex object recognition task.
Shape Analysis of Planar Multiply-Connected Objects Using Conformal Welding.
Lok Ming Lui; Wei Zeng; Shing-Tung Yau; Xianfeng Gu
2014-07-01
Shape analysis is a central problem in the field of computer vision. In 2D shape analysis, classification and recognition of objects from their observed silhouettes are extremely crucial but difficult. It usually involves an efficient representation of 2D shape space with a metric, so that its mathematical structure can be used for further analysis. Although the study of 2D simply-connected shapes has been subject to a corpus of literatures, the analysis of multiply-connected shapes is comparatively less studied. In this work, we propose a representation for general 2D multiply-connected domains with arbitrary topologies using conformal welding. A metric can be defined on the proposed representation space, which gives a metric to measure dissimilarities between objects. The main idea is to map the exterior and interior of the domain conformally to unit disks and circle domains (unit disk with several inner disks removed), using holomorphic 1-forms. A set of diffeomorphisms of the unit circle S(1) can be obtained, which together with the conformal modules are used to define the shape signature. A shape distance between shape signatures can be defined to measure dissimilarities between shapes. We prove theoretically that the proposed shape signature uniquely determines the multiply-connected objects under suitable normalization. We also introduce a reconstruction algorithm to obtain shapes from their signatures. This completes our framework and allows us to move back and forth between shapes and signatures. With that, a morphing algorithm between shapes can be developed through the interpolation of the Beltrami coefficients associated with the signatures. Experiments have been carried out on shapes extracted from real images. Results demonstrate the efficacy of our proposed algorithm as a stable shape representation scheme.
Event-related potentials during word mapping to object shape predict toddlers' vocabulary size
Borgström, Kristina; Torkildsen, Janne von Koss; Lindgren, Magnus
2015-01-01
What role does attention to different object properties play in early vocabulary development? This longitudinal study using event-related potentials in combination with behavioral measures investigated 20- and 24-month-olds' (n = 38; n = 34; overlapping n = 24) ability to use object shape and object part information in word-object mapping. The N400 component was used to measure semantic priming by images containing shape or detail information. At 20 months, the N400 to words primed by object shape varied in topography and amplitude depending on vocabulary size, and these differences predicted productive vocabulary size at 24 months. At 24 months, when most of the children had vocabularies of several hundred words, the relation between vocabulary size and the N400 effect in a shape context was weaker. Detached object parts did not function as word primes regardless of age or vocabulary size, although the part-objects were identified behaviorally. The behavioral measure, however, also showed relatively poor recognition of the part-objects compared to the shape-objects. These three findings provide new support for the link between shape recognition and early vocabulary development. PMID:25762957
Discrimination analysis using multi-object statistics of shape and pose
NASA Astrophysics Data System (ADS)
Gorczowski, Kevin; Styner, Martin; Jeong, Ja Yeon; Marron, J. S.; Piven, Joseph; Hazlett, Heather Cody; Pizer, Stephen M.; Gerig, Guido
2007-03-01
A main focus of statistical shape analysis is the description of variability of a population of geometric objects. In this paper, we present work towards modeling the shape and pose variability of sets of multiple objects. Principal geodesic analysis (PGA) is the extension of the standard technique of principal component analysis (PCA) into the nonlinear Riemannian symmetric space of pose and our medial m-rep shape description, a space in which use of PCA would be incorrect. In this paper, we discuss the decoupling of pose and shape in multi-object sets using different normalization settings. Further, we introduce methods of describing the statistics of object pose and object shape, both separately and simultaneously using a novel extension of PGA. We demonstrate our methods in an application to a longitudinal pediatric autism study with object sets of 10 subcortical structures in a population of 47 subjects. The results show that global scale accounts for most of the major mode of variation across time. Furthermore, the PGA components and the corresponding distribution of different subject groups vary significantly depending on the choice of normalization, which illustrates the importance of global and local pose alignment in multi-object shape analysis. Finally, we present results of using distance weighted discrimination analysis (DWD) in an attempt to use pose and shape features to separate subjects according to diagnosis, as well as visualize discriminating differences.
Multivariate Patterns in Object-Selective Cortex Dissociate Perceptual and Physical Shape Similarity
Haushofer, Johannes; Livingstone, Margaret S; Kanwisher, Nancy
2008-01-01
Prior research has identified the lateral occipital complex (LOC) as a critical cortical region for the representation of object shape in humans. However, little is known about the nature of the representations contained in the LOC and their relationship to the perceptual experience of shape. We used human functional MRI to measure the physical, behavioral, and neural similarity between pairs of novel shapes to ask whether the representations of shape contained in subregions of the LOC more closely reflect the physical stimuli themselves, or the perceptual experience of those stimuli. Perceptual similarity measures for each pair of shapes were obtained from a psychophysical same-different task; physical similarity measures were based on stimulus parameters; and neural similarity measures were obtained from multivoxel pattern analysis methods applied to anterior LOC (pFs) and posterior LOC (LO). We found that the pattern of pairwise shape similarities in LO most closely matched physical shape similarities, whereas shape similarities in pFs most closely matched perceptual shape similarities. Further, shape representations were similar across participants in LO but highly variable across participants in pFs. Together, these findings indicate that activation patterns in subregions of object-selective cortex encode objects according to a hierarchy, with stimulus-based representations in posterior regions and subjective and observer-specific representations in anterior regions. PMID:18666833
Haushofer, Johannes; Livingstone, Margaret S; Kanwisher, Nancy
2008-07-29
Prior research has identified the lateral occipital complex (LOC) as a critical cortical region for the representation of object shape in humans. However, little is known about the nature of the representations contained in the LOC and their relationship to the perceptual experience of shape. We used human functional MRI to measure the physical, behavioral, and neural similarity between pairs of novel shapes to ask whether the representations of shape contained in subregions of the LOC more closely reflect the physical stimuli themselves, or the perceptual experience of those stimuli. Perceptual similarity measures for each pair of shapes were obtained from a psychophysical same-different task; physical similarity measures were based on stimulus parameters; and neural similarity measures were obtained from multivoxel pattern analysis methods applied to anterior LOC (pFs) and posterior LOC (LO). We found that the pattern of pairwise shape similarities in LO most closely matched physical shape similarities, whereas shape similarities in pFs most closely matched perceptual shape similarities. Further, shape representations were similar across participants in LO but highly variable across participants in pFs. Together, these findings indicate that activation patterns in subregions of object-selective cortex encode objects according to a hierarchy, with stimulus-based representations in posterior regions and subjective and observer-specific representations in anterior regions.
Yao, Jincao; Yu, Huimin; Hu, Roland
2017-01-01
This paper introduces a new implicit-kernel-sparse-shape-representation-based object segmentation framework. Given an input object whose shape is similar to some of the elements in the training set, the proposed model can automatically find a cluster of implicit kernel sparse neighbors to approximately represent the input shape and guide the segmentation. A distance-constrained probabilistic definition together with a dualization energy term is developed to connect high-level shape representation and low-level image information. We theoretically prove that our model not only derives from two projected convex sets but is also equivalent to a sparse-reconstruction-error-based representation in the Hilbert space. Finally, a "wake-sleep"-based segmentation framework is applied to drive the evolutionary curve to recover the original shape of the object. We test our model on two public datasets. Numerical experiments on both synthetic images and real applications show the superior capabilities of the proposed framework.
Three-dimensional shape measurement of small object based on tri-frequency heterodyne method
NASA Astrophysics Data System (ADS)
Liu, Shouqi; Feng, Wei; Zhang, Qican; Liu, Yuankun
2015-08-01
Among temporal phase unwrapping methods based on structured light projection, tri-frequency heterodyne method, with the merits of less projected fringe, high precision and high reliability, has become a practical method in objects three-dimensional (3D) shape measurement. In this paper, a 3D shape measuring system was developed with a digital micromirror device (DMD) and synchronously trigged CCD camera. The 3D shape of a measured object was reconstructed from the deformed fringe patterns based on tri-frequency heterodyne method. The practical experiments were carried on some coins, and the results show that the system can restore their 3D shape on the tested partition with an accuracy of microns. This measurement system is prominent in 3D shape measurement of small or tiny objects, sample testing, and many other application fields.
Array projector design for projection on arbitrarily curved surfaces
NASA Astrophysics Data System (ADS)
Fischer, Stephanie; Schreiber, Peter; Riedel, Alf; Sieler, Marcel
2015-09-01
The micro-optical array projector is a new and innovative possibility to project patterns onto arbitrary shaped surfaces1 . In contrast to single-aperture systems the illuminance of the projected image is raised by only increasing the lateral extent of the projector while keeping the length constant. Thanks to the setup - analogous to a fly's eye condenser - we obtain a very compact design with homogenization of illumination. The images to be projected are presented as arbitrarily curved CAD-objects. Because of its complexity, the first attempt was a chief-ray backtrace implemented into a CAD-program, with the individual projectorlets modelled as pinhole cameras. With this principle one can trace the slides for several applications like the projection on perpendicular, as well as tilted and curved surfaces. Since aberrations cannot be considered with the simple CAD backtrace described above, we used the commercially available raytracer Zemax®, controlled by a macro, working in conjunction with a CADprogram for improved slide mask generation. Despite both methods, depending on the complexity of the optical system, are generating the fundamental mask data, the paper will show that there is a tradeoff between calculation time and accuracy. Based on this evaluation we will discuss further development as well as the possibility of improvement concerning the calculation methods. The different methods were investigated to determine their advantages and disadvantages. This provides the basis for the scope of application. Further we will demonstrate simulations as well as results obtained with built demonstrators.
Changes in Visual Object Recognition Precede the Shape Bias in Early Noun Learning
Yee, Meagan; Jones, Susan S.; Smith, Linda B.
2012-01-01
Two of the most formidable skills that characterize human beings are language and our prowess in visual object recognition. They may also be developmentally intertwined. Two experiments, a large sample cross-sectional study and a smaller sample 6-month longitudinal study of 18- to 24-month-olds, tested a hypothesized developmental link between changes in visual object representation and noun learning. Previous findings in visual object recognition indicate that children’s ability to recognize common basic level categories from sparse structural shape representations of object shape emerges between the ages of 18 and 24 months, is related to noun vocabulary size, and is lacking in children with language delay. Other research shows in artificial noun learning tasks that during this same developmental period, young children systematically generalize object names by shape, that this shape bias predicts future noun learning, and is lacking in children with language delay. The two experiments examine the developmental relation between visual object recognition and the shape bias for the first time. The results show that developmental changes in visual object recognition systematically precede the emergence of the shape bias. The results suggest a developmental pathway in which early changes in visual object recognition that are themselves linked to category learning enable the discovery of higher-order regularities in category structure and thus the shape bias in novel noun learning tasks. The proposed developmental pathway has implications for understanding the role of specific experience in the development of both visual object recognition and the shape bias in early noun learning. PMID:23227015
Changes in visual object recognition precede the shape bias in early noun learning.
Yee, Meagan; Jones, Susan S; Smith, Linda B
2012-01-01
Two of the most formidable skills that characterize human beings are language and our prowess in visual object recognition. They may also be developmentally intertwined. Two experiments, a large sample cross-sectional study and a smaller sample 6-month longitudinal study of 18- to 24-month-olds, tested a hypothesized developmental link between changes in visual object representation and noun learning. Previous findings in visual object recognition indicate that children's ability to recognize common basic level categories from sparse structural shape representations of object shape emerges between the ages of 18 and 24 months, is related to noun vocabulary size, and is lacking in children with language delay. Other research shows in artificial noun learning tasks that during this same developmental period, young children systematically generalize object names by shape, that this shape bias predicts future noun learning, and is lacking in children with language delay. The two experiments examine the developmental relation between visual object recognition and the shape bias for the first time. The results show that developmental changes in visual object recognition systematically precede the emergence of the shape bias. The results suggest a developmental pathway in which early changes in visual object recognition that are themselves linked to category learning enable the discovery of higher-order regularities in category structure and thus the shape bias in novel noun learning tasks. The proposed developmental pathway has implications for understanding the role of specific experience in the development of both visual object recognition and the shape bias in early noun learning.
An Effective 3D Shape Descriptor for Object Recognition with RGB-D Sensors
Liu, Zhong; Zhao, Changchen; Wu, Xingming; Chen, Weihai
2017-01-01
RGB-D sensors have been widely used in various areas of computer vision and graphics. A good descriptor will effectively improve the performance of operation. This article further analyzes the recognition performance of shape features extracted from multi-modality source data using RGB-D sensors. A hybrid shape descriptor is proposed as a representation of objects for recognition. We first extracted five 2D shape features from contour-based images and five 3D shape features over point cloud data to capture the global and local shape characteristics of an object. The recognition performance was tested for category recognition and instance recognition. Experimental results show that the proposed shape descriptor outperforms several common global-to-global shape descriptors and is comparable to some partial-to-global shape descriptors that achieved the best accuracies in category and instance recognition. Contribution of partial features and computational complexity were also analyzed. The results indicate that the proposed shape features are strong cues for object recognition and can be combined with other features to boost accuracy. PMID:28245553
Perception of Object Shape and Texture in Human Newborns: Evidence from Cross-Modal Transfer Tasks
ERIC Educational Resources Information Center
Sann, Coralie; Streri, Arlette
2007-01-01
The present research investigates newborn infants' perceptions of the shape and texture of objects through studies of the bi-directionality of cross-modal transfer between vision and touch. Using an intersensory procedure, four experiments were performed in newborns to study their ability to transfer shape and texture information from vision to…
Perception of Object Shape and Texture in Human Newborns: Evidence from Cross-Modal Transfer Tasks
ERIC Educational Resources Information Center
Sann, Coralie; Streri, Arlette
2007-01-01
The present research investigates newborn infants' perceptions of the shape and texture of objects through studies of the bi-directionality of cross-modal transfer between vision and touch. Using an intersensory procedure, four experiments were performed in newborns to study their ability to transfer shape and texture information from vision to…
Joint effects of illumination geometry and object shape in the perception of surface reflectance
Olkkonen, Maria; Brainard, David H
2011-01-01
Surface properties provide useful information for identifying objects and interacting with them. Effective utilization of this information, however, requires that the perception of object surface properties be relatively constant across changes in illumination and changes in object shape. Such constancy has been studied separately for changes in these factors. Here we ask whether the separate study of the illumination and shape effects is sufficient, by testing whether joint effects of illumination and shape changes can be predicted from the individual effects in a straightforward manner. We found large interactions between illumination and object shape in their effects on perceived glossiness. In addition, analysis of luminance histogram statistics could not account for the interactions. PMID:23145259
Learning the 3-D structure of objects from 2-D views depends on shape, not format
Tian, Moqian; Yamins, Daniel; Grill-Spector, Kalanit
2016-01-01
Humans can learn to recognize new objects just from observing example views. However, it is unknown what structural information enables this learning. To address this question, we manipulated the amount of structural information given to subjects during unsupervised learning by varying the format of the trained views. We then tested how format affected participants' ability to discriminate similar objects across views that were rotated 90° apart. We found that, after training, participants' performance increased and generalized to new views in the same format. Surprisingly, the improvement was similar across line drawings, shape from shading, and shape from shading + stereo even though the latter two formats provide richer depth information compared to line drawings. In contrast, participants' improvement was significantly lower when training used silhouettes, suggesting that silhouettes do not have enough information to generate a robust 3-D structure. To test whether the learned object representations were format-specific or format-invariant, we examined if learning novel objects from example views transfers across formats. We found that learning objects from example line drawings transferred to shape from shading and vice versa. These results have important implications for theories of object recognition because they suggest that (a) learning the 3-D structure of objects does not require rich structural cues during training as long as shape information of internal and external features is provided and (b) learning generates shape-based object representations independent of the training format. PMID:27153196
FUNCTION FOLLOWS FORM: ACTIVATION OF SHAPE & FUNCTION FEATURES DURING OBJECT IDENTIFICATION
Yee, Eiling; Huffstetler, Stacy; Thompson-Schill, Sharon L.
2011-01-01
Most theories of semantic memory characterize knowledge of a given object as comprising a set of semantic features. But how does conceptual activation of these features proceed during object identification? We present the results of a pair of experiments that demonstrate that object recognition is a dynamically unfolding process in which function follows form. We used eye movements to explore whether activating one object’s concept leads to the activation of others that share perceptual (shape) or abstract (function) features. Participants viewed four-picture displays and clicked on the picture corresponding to a heard word. In critical trials, the conceptual representation of one of the objects in the display was similar in shape or function (i.e., its purpose) to the heard word. Importantly, this similarity was not apparent in the visual depictions (e.g., for the target “frisbee,” the shape-related object was a triangular slice of pizza – a shape that a frisbee cannot take); preferential fixations on the related object were therefore attributable to overlap of the conceptual representations on the relevant features. We observed relatedness effects for both shape and function, but shape effects occurred earlier than function effects. We discuss the implications of these findings for current accounts of the representation of semantic memory. PMID:21417543
NASA Technical Reports Server (NTRS)
Goel, Narendra S.; Rozehnal, Ivan; Thompson, Richard L.
1991-01-01
A computer-graphics-based model, named DIANA, is presented for generation of objects of arbitrary shape and for calculating bidirectional reflectances and scattering from them, in the visible and infrared region. The computer generation is based on a modified Lindenmayer system approach which makes it possible to generate objects of arbitrary shapes and to simulate their growth, dynamics, and movement. Rendering techniques are used to display an object on a computer screen with appropriate shading and shadowing and to calculate the scattering and reflectance from the object. The technique is illustrated with scattering from canopies of simulated corn plants.
Khasnobish, Anwesha; Pal, Monalisa; Sardar, Dwaipayan; Tibarewala, D N; Konar, Amit
2016-08-01
This work is a preliminary study towards developing an alternative communication channel for conveying shape information to aid in recognition of items when tactile perception is hindered. Tactile data, acquired during object exploration by sensor fitted robot arm, are processed to recognize four basic geometric shapes. Patterns representing each shape, classified from tactile data, are generated using micro-controller-driven vibration motors which vibrotactually stimulate users to convey the particular shape information. These motors are attached on the subject's arm and their psychological (verbal) responses are recorded to assess the competence of the system to convey shape information to the user in form of vibrotactile stimulations. Object shapes are classified from tactile data with an average accuracy of 95.21 %. Three successive sessions of shape recognition from vibrotactile pattern depicted learning of the stimulus from subjects' psychological response which increased from 75 to 95 %. This observation substantiates the learning of vibrotactile stimulation in user over the sessions which in turn increase the system efficacy. The tactile sensing module and vibrotactile pattern generating module are integrated to complete the system whose operation is analysed in real-time. Thus, the work demonstrates a successful implementation of the complete schema of artificial tactile sensing system for object-shape recognition through vibrotactile stimulations.
Privileged Coding of Convex Shapes in Human Object-Selective Cortex
Haushofer, Johannes; Baker, Chris I.; Livingstone, Margaret S.; Kanwisher, Nancy
2008-01-01
What is the neural code for object shape? Despite intensive research, the precise nature of object representations in high-level visual cortex remains elusive. Here we use functional magnetic resonance imaging (fMRI) to show that convex shapes are encoded in a privileged fashion by human lateral occipital complex (LOC), a region that has been implicated in object recognition. On each trial, two convex or two concave shapes that were either identical or different were presented sequentially. Critically, the convex and concave stimuli were the same except for a binocular disparity change that reversed the figure–ground assignment. The fMRI response in LOC for convex stimuli was higher for different than that for identical shape pairs, indicating sensitivity to differences in convex shape. However, when the same stimuli were seen as concave, the response for different and identical pairs was the same, indicating lower sensitivity to changes in concave shape than convex shape. This pattern was more pronounced in the anterior than that in the posterior portion of LOC. These results suggest that convex contours could be important elements in cortical object representations. PMID:18579661
Privileged coding of convex shapes in human object-selective cortex.
Haushofer, Johannes; Baker, Chris I; Livingstone, Margaret S; Kanwisher, Nancy
2008-08-01
What is the neural code for object shape? Despite intensive research, the precise nature of object representations in high-level visual cortex remains elusive. Here we use functional magnetic resonance imaging (fMRI) to show that convex shapes are encoded in a privileged fashion by human lateral occipital complex (LOC), a region that has been implicated in object recognition. On each trial, two convex or two concave shapes that were either identical or different were presented sequentially. Critically, the convex and concave stimuli were the same except for a binocular disparity change that reversed the figure-ground assignment. The fMRI response in LOC for convex stimuli was higher for different than that for identical shape pairs, indicating sensitivity to differences in convex shape. However, when the same stimuli were seen as concave, the response for different and identical pairs was the same, indicating lower sensitivity to changes in concave shape than convex shape. This pattern was more pronounced in the anterior than that in the posterior portion of LOC. These results suggest that convex contours could be important elements in cortical object representations.
Proklova, Daria; Kaiser, Daniel; Peelen, Marius V
2016-05-01
Objects belonging to different categories evoke reliably different fMRI activity patterns in human occipitotemporal cortex, with the most prominent distinction being that between animate and inanimate objects. An unresolved question is whether these categorical distinctions reflect category-associated visual properties of objects or whether they genuinely reflect object category. Here, we addressed this question by measuring fMRI responses to animate and inanimate objects that were closely matched for shape and low-level visual features. Univariate contrasts revealed animate- and inanimate-preferring regions in ventral and lateral temporal cortex even for individually matched object pairs (e.g., snake-rope). Using representational similarity analysis, we mapped out brain regions in which the pairwise dissimilarity of multivoxel activity patterns (neural dissimilarity) was predicted by the objects' pairwise visual dissimilarity and/or their categorical dissimilarity. Visual dissimilarity was measured as the time it took participants to find a unique target among identical distractors in three visual search experiments, where we separately quantified overall dissimilarity, outline dissimilarity, and texture dissimilarity. All three visual dissimilarity structures predicted neural dissimilarity in regions of visual cortex. Interestingly, these analyses revealed several clusters in which categorical dissimilarity predicted neural dissimilarity after regressing out visual dissimilarity. Together, these results suggest that the animate-inanimate organization of human visual cortex is not fully explained by differences in the characteristic shape or texture properties of animals and inanimate objects. Instead, representations of visual object properties and object category may coexist in more anterior parts of the visual system.
Shape-independent object category responses revealed by MEG and fMRI decoding
Kaiser, Daniel; Azzalini, Damiano C.
2016-01-01
Neuroimaging research has identified category-specific neural response patterns to a limited set of object categories. For example, faces, bodies, and scenes evoke activity patterns in visual cortex that are uniquely traceable in space and time. It is currently debated whether these apparently categorical responses truly reflect selectivity for categories or instead reflect selectivity for category-associated shape properties. In the present study, we used a cross-classification approach on functional MRI (fMRI) and magnetoencephalographic (MEG) data to reveal both category-independent shape responses and shape-independent category responses. Participants viewed human body parts (hands and torsos) and pieces of clothing that were closely shape-matched to the body parts (gloves and shirts). Category-independent shape responses were revealed by training multivariate classifiers on discriminating shape within one category (e.g., hands versus torsos) and testing these classifiers on discriminating shape within the other category (e.g., gloves versus shirts). This analysis revealed significant decoding in large clusters in visual cortex (fMRI) starting from 90 ms after stimulus onset (MEG). Shape-independent category responses were revealed by training classifiers on discriminating object category (bodies and clothes) within one shape (e.g., hands versus gloves) and testing these classifiers on discriminating category within the other shape (e.g., torsos versus shirts). This analysis revealed significant decoding in bilateral occipitotemporal cortex (fMRI) and from 130 to 200 ms after stimulus onset (MEG). Together, these findings provide evidence for concurrent shape and category selectivity in high-level visual cortex, including category-level responses that are not fully explicable by two-dimensional shape properties. PMID:26740535
Norman, J Farley; Phillips, Flip; Holmin, Jessica S; Norman, Hideko F; Beers, Amanda M; Boswell, Alexandria M; Cheeseman, Jacob R; Stethen, Angela G; Ronning, Cecilia
2012-10-01
A set of three experiments evaluated 96 participants' ability to visually and haptically discriminate solid object shape. In the past, some researchers have found haptic shape discrimination to be substantially inferior to visual shape discrimination, while other researchers have found haptics and vision to be essentially equivalent. A primary goal of the present study was to understand these discrepant past findings and to determine the true capabilities of the haptic system. All experiments used the same task (same vs. different shape discrimination) and stimulus objects (James Gibson's "feelies" and a set of naturally shaped objects--bell peppers). However, the methodology varied across experiments. Experiment 1 used random 3-dimensional (3-D) orientations of the stimulus objects, and the conditions were full-cue (active manipulation of objects and rotation of the visual objects in depth). Experiment 2 restricted the 3-D orientations of the stimulus objects and limited the haptic and visual information available to the participants. Experiment 3 compared restricted and full-cue conditions using random 3-D orientations. We replicated both previous findings in the current study. When we restricted visual and haptic information (and placed the stimulus objects in the same orientation on every trial), the participants' visual performance was superior to that obtained for haptics (replicating the earlier findings of Davidson et al. in Percept Psychophys 15(3):539-543, 1974). When the circumstances resembled those of ordinary life (e.g., participants able to actively manipulate objects and see them from a variety of perspectives), we found no significant difference between visual and haptic solid shape discrimination.
Automatic modelling of building façade objects via primitive shapes
NASA Astrophysics Data System (ADS)
Hetti Arachchige, N.; Perera, S.
2014-08-01
This paper presents a new approach to recognize individual façade objects and to reconstruct such objects in 3D using MLS point clouds. Core of the approach is a primitive shape based algorithm, which introduces building primitives, to identify the façade objects separately from other irrelevant objects and then to model the correct topology. The primitive shape is identified against defined different primitive shapes by using the Douglas-Peucker algorithm. The advantage of this process is that it offers an ability not only to model correct geometric shapes but also to remove occlusion effects from the final model. To evaluate the validity of the proposed approach, experiments have been conducted using two types of street scene point clouds captured by Optech Lynx Mobile Mapper System and Z+F laser scanner. Results of the experiments show that the completeness, correctness, and quality of the reconstructed building façade objects are well over 90 %, proving the proposed method is a promising solution for modelling 3D façade objects with different geometric shapes.
Cheeseman, Jacob R.; Thomason, Kelsey E.; Ronning, Cecilia; Behari, Kriti; Kleinman, Kayla; Calloway, Autum B.; Lamirande, Davora
2016-01-01
It is well known that motion facilitates the visual perception of solid object shape, particularly when surface texture or other identifiable features (e.g., corners) are present. Conventional models of structure-from-motion require the presence of texture or identifiable object features in order to recover 3-D structure. Is the facilitation in 3-D shape perception similar in magnitude when surface texture is absent? On any given trial in the current experiments, participants were presented with a single randomly-selected solid object (bell pepper or randomly-shaped “glaven”) for 12 seconds and were required to indicate which of 12 (for bell peppers) or 8 (for glavens) simultaneously visible objects possessed the same shape. The initial single object’s shape was defined either by boundary contours alone (i.e., presented as a silhouette), specular highlights alone, specular highlights combined with boundary contours, or texture. In addition, there was a haptic condition: in this condition, the participants haptically explored with both hands (but could not see) the initial single object for 12 seconds; they then performed the same shape-matching task used in the visual conditions. For both the visual and haptic conditions, motion (rotation in depth or active object manipulation) was present in half of the trials and was not present for the remaining trials. The effect of motion was quantitatively similar for all of the visual and haptic conditions–e.g., the participants’ performance in Experiment 1 was 93.5 percent higher in the motion or active haptic manipulation conditions (when compared to the static conditions). The current results demonstrate that deforming specular highlights or boundary contours facilitate 3-D shape perception as much as the motion of objects that possess texture. The current results also indicate that the improvement with motion that occurs for haptics is similar in magnitude to that which occurs for vision. PMID:26863531
Arbitrarily tunable orbital angular momentum of photons.
Pan, Yue; Gao, Xu-Zhen; Ren, Zhi-Cheng; Wang, Xi-Lin; Tu, Chenghou; Li, Yongnan; Wang, Hui-Tian
2016-07-05
Orbital angular momentum (OAM) of photons, as a new fundamental degree of freedom, has excited a great diversity of interest, because of a variety of emerging applications. Arbitrarily tunable OAM has gained much attention, but its creation remains still a tremendous challenge. We demonstrate the realization of well-controlled arbitrarily tunable OAM in both theory and experiment. We present the concept of general OAM, which extends the OAM carried by the scalar vortex field to the OAM carried by the azimuthally varying polarized vector field. The arbitrarily tunable OAM we presented has the same characteristics as the well-defined integer OAM: intrinsic OAM, uniform local OAM and intensity ring, and propagation stability. The arbitrarily tunable OAM has unique natures: it is allowed to be flexibly tailored and the radius of the focusing ring can have various choices for a desired OAM, which are of great significance to the benefit of surprising applications of the arbitrary OAM.
Arbitrarily tunable orbital angular momentum of photons
Pan, Yue; Gao, Xu-Zhen; Ren, Zhi-Cheng; Wang, Xi-Lin; Tu, Chenghou; Li, Yongnan; Wang, Hui-Tian
2016-01-01
Orbital angular momentum (OAM) of photons, as a new fundamental degree of freedom, has excited a great diversity of interest, because of a variety of emerging applications. Arbitrarily tunable OAM has gained much attention, but its creation remains still a tremendous challenge. We demonstrate the realization of well-controlled arbitrarily tunable OAM in both theory and experiment. We present the concept of general OAM, which extends the OAM carried by the scalar vortex field to the OAM carried by the azimuthally varying polarized vector field. The arbitrarily tunable OAM we presented has the same characteristics as the well-defined integer OAM: intrinsic OAM, uniform local OAM and intensity ring, and propagation stability. The arbitrarily tunable OAM has unique natures: it is allowed to be flexibly tailored and the radius of the focusing ring can have various choices for a desired OAM, which are of great significance to the benefit of surprising applications of the arbitrary OAM. PMID:27378234
Laser cutting of irregular shape object based on stereo vision laser galvanometric scanning system
NASA Astrophysics Data System (ADS)
Qi, Li; Zhang, Yixin; Wang, Shun; Tang, Zhiqiang; Yang, Huan; Zhang, Xuping
2015-05-01
Irregular shape objects with different 3-dimensional (3D) appearances are difficult to be shaped into customized uniform pattern by current laser machining approaches. A laser galvanometric scanning system (LGS) could be a potential candidate since it can easily achieve path-adjustable laser shaping. However, without knowing the actual 3D topography of the object, the processing result may still suffer from 3D shape distortion. It is desirable to have a versatile auxiliary tool that is capable of generating 3D-adjusted laser processing path by measuring the 3D geometry of those irregular shape objects. This paper proposed the stereo vision laser galvanometric scanning system (SLGS), which takes the advantages of both the stereo vision solution and conventional LGS system. The 3D geometry of the object obtained by the stereo cameras is used to guide the scanning galvanometers for 3D-shape-adjusted laser processing. In order to achieve precise visual-servoed laser fabrication, these two independent components are integrated through a system calibration method using plastic thin film target. The flexibility of SLGS has been experimentally demonstrated by cutting duck feathers for badminton shuttle manufacture.
Attitude Estimation for Unresolved Agile Space Objects with Shape Model Uncertainty
NASA Astrophysics Data System (ADS)
Holzinger, M.; Alfriend, K. T.; Wetterer, C. J.; Luu, K. K.; Sabol, C.; Hamada, K.; Harms, A.
2012-09-01
The increasing number of manufactured on-orbit objects as well as improving sensor capabilities indicate that the number of trackable objects will likely exceed 100,000 within the next several years. Characterizing the large population of non-spatially resolved active spacecraft, retired spacecraft, rocket bodies, debris, and High Area to Mass Ratio (HAMR) objects necessarily involves both attitude and shape estimation. While spatially unresolved space objects cannot be directly imaged, attitude and shape may be inferred by carefully examining their lightcurves. Lightcurves are temporally-resolved sequences of photometric intensity measurements over one or more bandwidths. Because the observable reflected light from an unresolved space object is a strong function of both its shape and attitude, estimating these parameters using lightcurves can provide an avenue to determine both space object attitude and shape. This problem is traditionally called `lightcurve inversion.' While lightcurves have been used for 25 years to characterize spin states and shapes of asteroids, estimating the attitude states and shapes of manufactured space objects involves a new set of challenges. New challenges addressed in this paper are 1) An active (agile) space object is often directly controlling its attitude, meaning that torques acting on the space object are not necessarily zero (non-homogeneous motion) and mass properties may not be known, 2) Shape models must often be estimated, and as such contain errors that need to be accounted for in the measurement function, 3) Dynamics and measurement functions are excessively nonlinear, and manufactured space objects may be quite symmetric about at least one axis of rotation/reflection. This can lead to multiple possible attitude estimate solutions and suggests the use of non-Gaussian estimation approaches. Agile space objects (those that can actively maneuver) pose new problems to lightcurve inversion efforts to estimate attitude. Because
Multi-resolution multi-object statistical shape models based on the locality assumption.
Wilms, Matthias; Handels, Heinz; Ehrhardt, Jan
2017-02-17
Statistical shape models learned from a population of previously observed training shapes are nowadays widely used in medical image analysis to aid segmentation or classification. However, providing an appropriate and representative training population of preferably manual segmentations is typically either very labor-intensive or even impossible. Therefore, statistical shape models in practice frequently suffer from the high-dimension-low-sample-size (HDLSS) problem resulting in models with insufficient expressiveness. In this paper, a novel approach for learning representative multi-resolution multi-object statistical shape models from a small number of training samples that adequately model the variability of each individual object as well as their interrelations is presented. The method is based on the assumption of locality, which means that local shape variations have limited effects in distant areas and, therefore, can be modeled independently. This locality assumption is integrated into the standard statistical shape modeling framework by manipulating the sample covariance matrix (non-zero covariances between distant landmarks are set to zero). To allow for multi-object modeling, a method for computing distances between points located on different object shapes is proposed. Furthermore, different levels of locality are introduced by deriving a multi-resolution scheme, which is equipped with a method to combine variability information modeled at different levels into a single shape model. This combined representation of global and local variability in a single shape model allows the use of the classical active shape model strategy for model-based image segmentation. An extensive evaluation based on a public data base of 247 chest radiographs is performed to show the modeling and segmentation capabilities of the proposed approach in single- and multi-object HDLSS scenarios. The new approach is not only compared to the classical shape modeling method but also
Distractor objects affect fingers' angular distances but not fingers' shaping during grasping.
Ansuini, Caterina; Tognin, Veronica; Turella, Luca; Castiello, Umberto
2007-04-01
The aim of the present study was to determine whether and how hand shaping was affected by the presence of a distractor object adjacent to the to-be-grasped object. Twenty subjects were requested to reach towards and grasp a 'convex' or a 'concave' object in the presence or absence of a distractor object either of the same or different shape than the target object. Flexion/extension at the metacarpal-phalangeal (MCP) and proximal interphalangeal joints of all digits, and abduction angle between digits were measured by resistive sensors embedded in a glove. The results indicate robust interference effects at the level of reach duration and the extent of fingers' abduction angles together with changes at the level of a single joint for the thumb. No distractor effects on individual fingers' joints except for the MCP of the middle and little fingers were found. These findings suggest that the presence of distractor object affects hand shaping in terms of fingers' abduction angles, but not at the level of 'shape dependent' fingers' angular excursions. Furthermore, they support the importance of the thumb for the guidance of selective reach-to-grasp movements. We discuss these results in the context of current theories proposed to explain the object selection processes underlying the control of hand action.
Multi-object segmentation using coupled nonparametric shape and relative pose priors
NASA Astrophysics Data System (ADS)
Uzunbas, Mustafa Gökhan; Soldea, Octavian; Çetin, Müjdat; Ünal, Gözde; Erçil, Aytül; Unay, Devrim; Ekin, Ahmet; Firat, Zeynep
2009-02-01
We present a new method for multi-object segmentation in a maximum a posteriori estimation framework. Our method is motivated by the observation that neighboring or coupling objects in images generate configurations and co-dependencies which could potentially aid in segmentation if properly exploited. Our approach employs coupled shape and inter-shape pose priors that are computed using training images in a nonparametric multi-variate kernel density estimation framework. The coupled shape prior is obtained by estimating the joint shape distribution of multiple objects and the inter-shape pose priors are modeled via standard moments. Based on such statistical models, we formulate an optimization problem for segmentation, which we solve by an algorithm based on active contours. Our technique provides significant improvements in the segmentation of weakly contrasted objects in a number of applications. In particular for medical image analysis, we use our method to extract brain Basal Ganglia structures, which are members of a complex multi-object system posing a challenging segmentation problem. We also apply our technique to the problem of handwritten character segmentation. Finally, we use our method to segment cars in urban scenes.
Multisensory cortical processing of object shape and its relation to mental imagery.
Zhang, Minming; Weisser, Valerie D; Stilla, Randall; Prather, S C; Sathian, K
2004-06-01
Here, we used functional magnetic resonance imaging to investigate the multisensory processing of object shape in the human cerebral cortex and explored the role of mental imagery in such processing. Regions active bilaterally during both visual and haptic shape perception, relative to texture perception in the respective modality, included parts of the superior parietal gyrus, the anterior intraparietal sulcus, and the lateral occipital complex. Of these bimodal regions, the lateral occipital complexes preferred visual over haptic stimuli, whereas the parietal areas preferred haptic over visual stimuli. Whereas most subjects reported little haptic imagery during visual shape perception, experiences of visual imagery during haptic shape perception were common. Across subjects, ratings of the vividness of visual imagery strongly predicted the amount of haptic shape-selective activity in the right, but not in the left, lateral occipital complex. Thus, visual imagery appears to contribute to activation of some, but not all, visual cortical areas during haptic perception.
Programming self assembly by designing the 3D shape of floating objects
NASA Astrophysics Data System (ADS)
Poty, Martin; Lagubeau, Guillaume; Lumay, Geoffroy; Vandewalle, Nicolas
2014-11-01
Self-assembly of floating particles driven by capillary forces at some liquid-air interface leads to the formation of two-dimensionnal structures. Using a 3d printer, milimeter scale objets are produced. Their 3d shape is chosen in order to create capillary multipoles. The capillary interactions between these components can be either attractive or repulsive depending on the interface local deformations along the liquid-air interface. In order to understand how the shape of an object deforms the interface, we developed an original profilometry method. The measurements show that specific structures can be programmed by selecting the 3d branched shapes.
Differentiation of hand posture to object shape in children with unilateral spastic cerebral palsy.
Wolff, Aviva L; Raghavan, Preeti; Kaminski, Terry; Hillstrom, Howard J; Gordon, Andrew M
2015-01-01
Quantifying hand-shaping in children with unilateral spastic cerebral palsy (USCP) is the first step in understanding hand posture differentiation. To quantify this ability and determine how hand posture evolves during reach toward various object shapes in children with unilateral spastic cerebral palsy (USCP), 2 groups of children (10 typically developing, and 10 USCP, ages 6-13) were studied in a single-session cross-sectional study. Subjects grasped rectangular, concave, and convex objects with each hand. Metacarpal and proximal interphalangeal joint finger flexion and finger abduction angles were calculated. The extent to which hand posture reflects object shape was calculated using a "visuomotor efficiency (VME) index" (a score of 100 reflects perfect discrimination between objects). A mixed design ANOVA with repeated measures on time was used to compare the VME between groups. Children with USCP demonstrated a lower VME than controls in the affected hand, indicating less effective hand-shaping; p<.01. There was also a difference between groups in the evolution of VME throughout reach; p<.01. No difference in hand-shaping in the less affected hand in USCP was observed. Analysis of joint angles at contact and VME throughout reach demonstrated that children with USCP differentiated their hand posture to objects of different shapes, but demonstrated deficits in the timing and magnitude of hand-shaping isolated to the affected side. The present study suggests it may be important to consider the quality of hand activity using quantitative approaches such as VME analyses. Rehabilitation approaches that target these deficits to improve joint mobility and motor control are worth testing.
3D shape reconstruction of loop objects in X-ray protein crystallography.
Strutz, Tilo
2011-01-01
Knowledge of the shape of crystals can benefit data collection in X-ray crystallography. A preliminary step is the determination of the loop object, i.e., the shape of the loop holding the crystal. Based on the standard set-up of experimental X-ray stations for protein crystallography, the paper reviews a reconstruction method merely requiring 2D object contours and presents a dedicated novel algorithm. Properties of the object surface (e.g., texture) and depth information do not have to be considered. The complexity of the reconstruction task is significantly reduced by slicing the 3D object into parallel 2D cross-sections. The shape of each cross-section is determined using support lines forming polygons. The slicing technique allows the reconstruction of concave surfaces perpendicular to the direction of projection. In spite of the low computational complexity, the reconstruction method is resilient to noisy object projections caused by imperfections in the image-processing system extracting the contours. The algorithm developed here has been successfully applied to the reconstruction of shapes of loop objects in X-ray crystallography.
Simultaneous object classification and segmentation with high-order multiple shape models.
Lecumberry, Federico; Pardo, Alvaro; Sapiro, Guillermo
2010-03-01
Shape models (SMs), capturing the common features of a set of training shapes, represent a new incoming object based on its projection onto the corresponding model. Given a set of learned SMs representing different objects classes, and an image with a new shape, this work introduces a joint classification-segmentation framework with a twofold goal. First, to automatically select the SM that best represents the object, and second, to accurately segment the image taking into account both the image information and the features and variations learned from the online selected model. A new energy functional is introduced that simultaneously accomplishes both goals. Model selection is performed based on a shape similarity measure, online determining which model to use at each iteration of the steepest descent minimization, allowing for model switching and adaptation to the data. High-order SMs are used in order to deal with very similar object classes and natural variability within them. Position and transformation invariance is included as part of the modeling as well. The presentation of the framework is complemented with examples for the difficult task of simultaneously classifying and segmenting closely related shapes, such as stages of human activities, in images with severe occlusions.
Cristino, Filipe; Davitt, Lina; Hayward, William G; Leek, E Charles
2015-01-01
Current theories of object recognition in human vision make different predictions about whether the recognition of complex, multipart objects should be influenced by shape information about surface depth orientation and curvature derived from stereo disparity. We examined this issue in five experiments using a recognition memory paradigm in which observers (N = 134) memorized and then discriminated sets of 3D novel objects at trained and untrained viewpoints under either mono or stereo viewing conditions. In order to explore the conditions under which stereo-defined shape information contributes to object recognition we systematically varied the difficulty of view generalization by increasing the angular disparity between trained and untrained views. In one series of experiments, objects were presented from either previously trained views or untrained views rotated (15°, 30°, or 60°) along the same plane. In separate experiments we examined whether view generalization effects interacted with the vertical or horizontal plane of object rotation across 40° viewpoint changes. The results showed robust viewpoint-dependent performance costs: Observers were more efficient in recognizing learned objects from trained than from untrained views, and recognition was worse for extrapolated than for interpolated untrained views. We also found that performance was enhanced by stereo viewing but only at larger angular disparities between trained and untrained views. These findings show that object recognition is not based solely on 2D image information but that it can be facilitated by shape information derived from stereo disparity.
Schumacher, Sarah; Burt de Perera, Theresa; von der Emde, Gerhard
2016-12-12
The weakly electric fish Gnathonemus petersii can recognise objects using active electrolocation. Here, we tested two aspects of object recognition; first whether shape recognition might be influenced by movement of the fish, and second whether object discrimination is affected by the presence of electrical noise from conspecifics. (i) Unlike other object features, such as size or volume, no parameter within a single electrical image has been found that encodes object shape. We investigated whether shape recognition might be facilitated by movement-induced modulations (MIM) of the set of electrical images that are created as a fish swims past an object. Fish were trained to discriminate between pairs of objects that either created similar or dissimilar levels of MIM of the electrical images. As predicted, the fish were able to discriminate between objects up to a longer distance if there was a large difference in MIM between the objects than if there was a small difference. This supports an involvement of MIMs in shape recognition but the use of other cues cannot be excluded. (ii) Electrical noise might impair object recognition if the noise signals overlap with the EODs of an electrolocating fish. To avoid jamming, we predicted that fish might employ pulsing strategies to prevent overlaps. To investigate the influence of electrical noise on discrimination performance, two fish were tested either in the presence of a conspecific or of playback signals and the electric signals were recorded during the experiments. The fish were surprisingly immune to jamming by conspecifics: While the discrimination performance of one fish dropped to chance level when more than 22% of its EODs overlapped with the noise signals, the performance of the other fish was not impaired even when all its EODs overlapped. Neither of the fish changed their pulsing behaviour, suggesting that they did not use any kind of jamming avoidance strategy.
Microwave and camera sensor fusion for the shape extraction of metallic 3D space objects
NASA Technical Reports Server (NTRS)
Shaw, Scott W.; Defigueiredo, Rui J. P.; Krishen, Kumar
1989-01-01
The vacuum of space presents special problems for optical image sensors. Metallic objects in this environment can produce intense specular reflections and deep shadows. By combining the polarized RCS with an incomplete camera image, it has become possible to better determine the shape of some simple three-dimensional objects. The radar data are used in an iterative procedure that generates successive approximations to the target shape by minimizing the error between computed scattering cross-sections and the observed radar returns. Favorable results have been obtained for simulations and experiments reconstructing plates, ellipsoids, and arbitrary surfaces.
Microwave and camera sensor fusion for the shape extraction of metallic 3D space objects
NASA Technical Reports Server (NTRS)
Shaw, Scott W.; Defigueiredo, Rui J. P.; Krishen, Kumar
1989-01-01
The vacuum of space presents special problems for optical image sensors. Metallic objects in this environment can produce intense specular reflections and deep shadows. By combining the polarized RCS with an incomplete camera image, it has become possible to better determine the shape of some simple three-dimensional objects. The radar data are used in an iterative procedure that generates successive approximations to the target shape by minimizing the error between computed scattering cross-sections and the observed radar returns. Favorable results have been obtained for simulations and experiments reconstructing plates, ellipsoids, and arbitrary surfaces.
Shaping functional nano-objects by 3D confined supramolecular assembly.
Deng, Renhua; Liang, Fuxin; Li, Weikun; Liu, Shanqin; Liang, Ruijing; Cai, Mingle; Yang, Zhenzhong; Zhu, Jintao
2013-12-20
Nano-objects are generated through 3D confined supramolecular assembly, followed by a sequential disintegration by rupturing the hydrogen bonding. The shape of the nano-objects is tunable, ranging from nano-disc, nano-cup, to nano-toroid. The nano-objects are pH-responsive. Functional materials for example inorganic or metal nanoparticles are easily complexed onto the external surface, to extend both composition and microstructure of the nano-objects. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
The generation and use of numerical shape models for irregular Solar System objects
NASA Technical Reports Server (NTRS)
Simonelli, Damon P.; Thomas, Peter C.; Carcich, Brian T.; Veverka, Joseph
1993-01-01
We describe a procedure that allows the efficient generation of numerical shape models for irregular Solar System objects, where a numerical model is simply a table of evenly spaced body-centered latitudes and longitudes and their associated radii. This modeling technique uses a combination of data from limbs, terminators, and control points, and produces shape models that have some important advantages over analytical shape models. Accurate numerical shape models make it feasible to study irregular objects with a wide range of standard scientific analysis techniques. These applications include the determination of moments of inertia and surface gravity, the mapping of surface locations and structural orientations, photometric measurement and analysis, the reprojection and mosaicking of digital images, and the generation of albedo maps. The capabilities of our modeling procedure are illustrated through the development of an accurate numerical shape model for Phobos and the production of a global, high-resolution, high-pass-filtered digital image mosaic of this Martian moon. Other irregular objects that have been modeled, or are being modeled, include the asteroid Gaspra and the satellites Deimos, Amalthea, Epimetheus, Janus, Hyperion, and Proteus.
Inferring the stiffness of unfamiliar objects from optical, shape, and motion cues.
Schmidt, Filipp; Paulun, Vivian C; van Assen, Jan Jaap R; Fleming, Roland W
2017-03-01
Visually inferring the stiffness of objects is important for many tasks but is challenging because, unlike optical properties (e.g., gloss), mechanical properties do not directly affect image values. Stiffness must be inferred either (a) by recognizing materials and recalling their properties (associative approach) or (b) from shape and motion cues when the material is deformed (estimation approach). Here, we investigated interactions between these two inference types. Participants viewed renderings of unfamiliar shapes with 28 materials (e.g., nickel, wax, cork). In Experiment 1, they viewed nondeformed, static versions of the objects and rated 11 material attributes (e.g., soft, fragile, heavy). The results confirm that the optical materials elicited a wide range of apparent properties. In Experiment 2, using a blue plastic material with intermediate apparent softness, the objects were subjected to physical simulations of 12 shape-transforming processes (e.g., twisting, crushing, stretching). Participants rated softness and extent of deformation. Both correlated with the physical magnitude of deformation. Experiment 3 combined variations in optical cues with shape cues. We find that optical cues completely dominate. Experiment 4 included the entire motion sequence of the deformation, yielding significant contributions of optical as well as motion cues. Our findings suggest participants integrate shape, motion, and optical cues to infer stiffness, with optical cues playing a major role for our range of stimuli.
The generation and use of numerical shape models for irregular Solar System objects
NASA Technical Reports Server (NTRS)
Simonelli, Damon P.; Thomas, Peter C.; Carcich, Brian T.; Veverka, Joseph
1993-01-01
We describe a procedure that allows the efficient generation of numerical shape models for irregular Solar System objects, where a numerical model is simply a table of evenly spaced body-centered latitudes and longitudes and their associated radii. This modeling technique uses a combination of data from limbs, terminators, and control points, and produces shape models that have some important advantages over analytical shape models. Accurate numerical shape models make it feasible to study irregular objects with a wide range of standard scientific analysis techniques. These applications include the determination of moments of inertia and surface gravity, the mapping of surface locations and structural orientations, photometric measurement and analysis, the reprojection and mosaicking of digital images, and the generation of albedo maps. The capabilities of our modeling procedure are illustrated through the development of an accurate numerical shape model for Phobos and the production of a global, high-resolution, high-pass-filtered digital image mosaic of this Martian moon. Other irregular objects that have been modeled, or are being modeled, include the asteroid Gaspra and the satellites Deimos, Amalthea, Epimetheus, Janus, Hyperion, and Proteus.
NASA Astrophysics Data System (ADS)
Anisimov, Andrei G.; Groves, Roger M.
2015-05-01
Shearography (speckle pattern shearing interferometry) is a non-destructive testing technique that provides full-field surface strain characterization. Although real-life objects especially in aerospace, transport or cultural heritage are not flat (e.g. aircraft leading edges or sculptures), their inspection with shearography is of interest for both hidden defect detection and material characterization. Accurate strain measuring of a highly curved or free form surface needs to be performed by combining inline object shape measuring and processing of shearography data in 3D. Previous research has not provided a general solution. This research is devoted to the practical questions of 3D shape shearography system development for surface strain characterization of curved objects. The complete procedure of calibration and data processing of a 3D shape shearography system with integrated structured light projector is presented. This includes an estimation of the actual shear distance and a sensitivity matrix correction within the system field of view. For the experimental part a 3D shape shearography system prototype was developed. It employs three spatially-distributed shearing cameras, with Michelson interferometers acting as the shearing devices, one illumination laser source and a structured light projector. The developed system performance was evaluated with a previously reported cylinder specimen (length 400 mm, external diameter 190 mmm) loaded by internal pressure. Further steps for the 3D shape shearography prototype and the technique development are also proposed.
Object shape and orientation do not routinely influence performance during language processing.
Rommers, Joost; Meyer, Antje S; Huettig, Falk
2013-11-01
The role of visual representations during language processing remains unclear: They could be activated as a necessary part of the comprehension process, or they could be less crucial and influence performance in a task-dependent manner. In the present experiments, participants read sentences about an object. The sentences implied that the object had a specific shape or orientation. They then either named a picture of that object (Experiments 1 and 3) or decided whether the object had been mentioned in the sentence (Experiment 2). Orientation information did not reliably influence performance in any of the experiments. Shape representations influenced performance most strongly when participants were asked to compare a sentence with a picture or when they were explicitly asked to use mental imagery while reading the sentences. Thus, in contrast to previous claims, implied visual information often does not contribute substantially to the comprehension process during normal reading.
Use of Image Based Modelling for Documentation of Intricately Shaped Objects
NASA Astrophysics Data System (ADS)
Marčiš, M.; Barták, P.; Valaška, D.; Fraštia, M.; Trhan, O.
2016-06-01
In the documentation of cultural heritage, we can encounter three dimensional shapes and structures which are complicated to measure. Such objects are for example spiral staircases, timber roof trusses, historical furniture or folk costume where it is nearly impossible to effectively use the traditional surveying or the terrestrial laser scanning due to the shape of the object, its dimensions and the crowded environment. The actual methods of digital photogrammetry can be very helpful in such cases with the emphasis on the automated processing of the extensive image data. The created high resolution 3D models and 2D orthophotos are very important for the documentation of architectural elements and they can serve as an ideal base for the vectorization and 2D drawing documentation. This contribution wants to describe the various usage of image based modelling in specific interior spaces and specific objects. The advantages and disadvantages of the photogrammetric measurement of such objects in comparison to other surveying methods are reviewed.
NASA Astrophysics Data System (ADS)
Bordatchev, Evgueni; Aghayan, Hamid; Yang, Jun
2014-03-01
Presence of contaminants, such as gasoline, moisture, and coolant in the engine lubricant indicates mechanical failure within the engine and significantly reduces lubricant quality. This paper describes a novel sensing system, its methodology and experimental verifications for analysis of the presence of contaminants in the engine lubricants. The sensing methodology is based on the statistical shape analysis methodology utilizing optical analysis of the distortion effect when an object image is obtained through a thin random optical medium. The novelty of the proposed sensing system lies within the employed methodology which an object with a known periodic shape is introduced behind a thin film of the contaminated lubricant. In this case, an acquired image represents a combined lubricant-object optical appearance, where an a priori known periodical structure of the object is distorted by a contaminated lubricant. The object, e.g. a stainless steel woven wire cloth with a mesh size of 65×65 µm2 and a circular wire diameter of 33 µm was placed behind a microfluidic channel, containing engine lubricant and optical images of flowing lubricant with stationary object were acquired and analyzed. Several parameters of acquired optical images, such as, color of lubricant and object, object shape width at object and lubricant levels, object relative color, and object width non-uniformity coefficient, were proposed. Measured on-line parameters were used for optical analysis of fresh and contaminated lubricants. Estimation of contaminant presence and lubricant condition was performed by comparison of parameters for fresh and contaminated lubricants. Developed methodology was verified experimentally showing ability to distinguish lubricants with 1%, 4%, 7%, and 10% coolant, gasoline and water contamination individually and in a combination form of coolant (0%-5%) and gasoline (0%-5%).
Content-Based Search on a Database of Geometric Models: Identifying Objects of Similar Shape
XAVIER, PATRICK G.; HENRY, TYSON R.; LAFARGE, ROBERT A.; MEIRANS, LILITA; RAY, LAWRENCE P.
2001-11-01
The Geometric Search Engine is a software system for storing and searching a database of geometric models. The database maybe searched for modeled objects similar in shape to a target model supplied by the user. The database models are generally from CAD models while the target model may be either a CAD model or a model generated from range data collected from a physical object. This document describes key generation, database layout, and search of the database.
Wu, Yabei; Lu, Huanzhang; Zhao, Fei; Zhang, Zhiyong
2016-01-01
Shape serves as an important additional feature for space target classification, which is complementary to those made available. Since different shapes lead to different projection functions, the projection property can be regarded as one kind of shape feature. In this work, the problem of estimating the projection function from the infrared signature of the object is addressed. We show that the projection function of any rotationally symmetric object can be approximately represented as a linear combination of some base functions. Based on this fact, the signal model of the emissivity-area product sequence is constructed, which is a particular mathematical function of the linear coefficients and micro-motion parameters. Then, the least square estimator is proposed to estimate the projection function and micro-motion parameters jointly. Experiments validate the effectiveness of the proposed method. PMID:27763500
Multi-object active shape model construction for abdomen segmentation: preliminary results.
Gollmer, Sebastian T; Simon, Martin; Bischof, Arpad; Barkhausen, Jorg; Buzug, Thorsten M
2012-01-01
The automatic segmentation of abdominal organs is a pre-requisite for many medical applications. Successful methods typically rely on prior knowledge about the to be segmented anatomy as it is for instance provided by means of active shape models (ASMs). Contrary to most previous ASM based methods, this work does not focus on individual organs. Instead, a more holistic approach that aims at exploiting inter-organ relationships to eventually segment a complex of organs is proposed. Accordingly, a flexible framework for automatic construction of multi-object ASMs is introduced, employed for coupled shape modeling, and used for co-segmentation of liver and spleen based on a new coupled shape/separate pose approach. Our first results indicate feasible segmentation accuracies, whereas pose decoupling leads to substantially better segmentation results and performs in average also slightly better than the standard single-object ASM approach.
Wu, Yabei; Lu, Huanzhang; Zhao, Fei; Zhang, Zhiyong
2016-10-17
Shape serves as an important additional feature for space target classification, which is complementary to those made available. Since different shapes lead to different projection functions, the projection property can be regarded as one kind of shape feature. In this work, the problem of estimating the projection function from the infrared signature of the object is addressed. We show that the projection function of any rotationally symmetric object can be approximately represented as a linear combination of some base functions. Based on this fact, the signal model of the emissivity-area product sequence is constructed, which is a particular mathematical function of the linear coefficients and micro-motion parameters. Then, the least square estimator is proposed to estimate the projection function and micro-motion parameters jointly. Experiments validate the effectiveness of the proposed method.
Confinement effects on the shape and composition of bimetallic nano-objects in carbon nanotubes.
Li, X; Hungria, T; Garcia Marcelot, C; Axet, M R; Fazzini, P-F; Tan, R P; Serp, P; Soulantica, K
2016-02-07
CoPt and FePt nanostructures have been efficiently confined in carbon nanotubes (CNTs). A marked confinement effect has been evidenced, both on bimetallic nano-object shape and composition. In large diameter CNTs small Co- and Fe-rich nanoparticles are formed, while in small diameter CNTs Pt-rich nanowires are selectively produced.
A genetic algorithm based multi-objective shape optimization scheme for cementless femoral implant.
Chanda, Souptick; Gupta, Sanjay; Kumar Pratihar, Dilip
2015-03-01
The shape and geometry of femoral implant influence implant-induced periprosthetic bone resorption and implant-bone interface stresses, which are potential causes of aseptic loosening in cementless total hip arthroplasty (THA). Development of a shape optimization scheme is necessary to achieve a trade-off between these two conflicting objectives. The objective of this study was to develop a novel multi-objective custom-based shape optimization scheme for cementless femoral implant by integrating finite element (FE) analysis and a multi-objective genetic algorithm (GA). The FE model of a proximal femur was based on a subject-specific CT-scan dataset. Eighteen parameters describing the nature of four key sections of the implant were identified as design variables. Two objective functions, one based on implant-bone interface failure criterion, and the other based on resorbed proximal bone mass fraction (BMF), were formulated. The results predicted by the two objective functions were found to be contradictory; a reduction in the proximal bone resorption was accompanied by a greater chance of interface failure. The resorbed proximal BMF was found to be between 23% and 27% for the trade-off geometries as compared to ∼39% for a generic implant. Moreover, the overall chances of interface failure have been minimized for the optimal designs, compared to the generic implant. The adaptive bone remodeling was also found to be minimal for the optimally designed implants and, further with remodeling, the chances of interface debonding increased only marginally.
Dispersion analysis of arbitrarily cut orthorhombic crystals.
Höfer, Sonja; Ivanovski, Vladimir; Uecker, Reinhard; Kwasniewski, Albert; Popp, Jürgen; Mayerhöfer, Thomas G
2017-06-05
We developed a measurement and evaluation scheme to perform dispersion analysis on arbitrarily cut orthorhombic crystals based on the schemes developed for triclinic and uniaxial crystals. As byproduct of dispersion analysis the orientations of the crystal axes are found. In contrast to the spectra of arbitrarily cut uniaxial crystals, where the fit routine has to separate two independent principal spectra, the spectra of arbitrarily cut orthorhombic crystals are a combination of three independent spectra and the evaluation scheme gets more complex. Dispersion analysis is exemplary performed on two different crystals, which show different spectral features and different levels of difficulties to evaluate. Neodymium gallate (NdGaO3) has broad overlapping reflections bands while topaz (Al2SiO4 [F, OH]2) has a quite high total number of infrared active bands. Copyright © 2017 Elsevier B.V. All rights reserved.
A Skeleton-Based 3D Shape Reconstruction of Free-Form Objects with Stereo Vision
NASA Astrophysics Data System (ADS)
Saini, Deepika; Kumar, Sanjeev
2015-12-01
In this paper, an efficient approach is proposed for recovering the 3D shape of a free-form object from its arbitrary pair of stereo images. In particular, the reconstruction problem is treated as the reconstruction of the skeleton and the external boundary of the object. The reconstructed skeleton is termed as the line-like representation or curve-skeleton of the 3D object. The proposed solution for object reconstruction is based on this evolved curve-skeleton. It is used as a seed for recovering shape of the 3D object, and the extracted boundary is used for terminating the growing process of the object. NURBS-skeleton is used to extract the skeleton of both views. Affine invariant property of the convex hulls is used to establish the correspondence between the skeletons and boundaries in the stereo images. In the growing process, a distance field is defined for each skeleton point as the smallest distance from that point to the boundary of the object. A sphere centered at a skeleton point of radius equal to the minimum distance to the boundary is tangential to the boundary. Filling in the spheres centered at each skeleton point reconstructs the object. Several results are presented in order to check the applicability and validity of the proposed algorithm.
NASA Technical Reports Server (NTRS)
Goel, Narenda S.; Rozehnal, I.; Thompson, R. L.
1991-01-01
A general computer graphics based model is presented for computer generation of objects of arbitrary shape and for calculating Bidirectional Reflectance Factor (BRF) and scattering from them, in the optical region. The computer generation uses a modified Lindemayer system (L system) approach. For rendering on a computer screen, the object is divided into polygons, and innovative computer graphics techniques are used to display the object and to calculate the scattering and reflectance from the object. The use of the technique is illustrated with scattering from canopies of simulated corn plants and from a snow covered mountain. The scattering is quantified using measures like BRF and albedo and by rendering the objects with brightness of each of the two facets of a polygon proportional to the amount of light scattered from the object in the viewer's direction.
Perceptual organization of shape, color, shade, and lighting in visual and pictorial objects
Pinna, Baingio
2012-01-01
The main questions we asked in this work are the following: Where are representations of shape, color, depth, and lighting mostly located? Does their formation take time to develop? How do they contribute to determining and defining a visual object, and how do they differ? How do visual artists use them to create objects and scenes? Is the way artists use them related to the way we perceive them? To answer these questions, we studied the microgenetic development of the object perception and formation. Our hypothesis is that the main object properties are extracted in sequential order and in the same order that these roles are also used by artists and children of different age to paint objects. The results supported the microgenesis of object formation according to the following sequence: contours, color, shading, and lighting. PMID:23145283
Hatch, Cory D; Wehby, George L; Nidey, Nichole L; Moreno Uribe, Lina M
2017-09-01
Meeting patient desires for enhanced facial esthetics requires that providers have standardized and objective methods to measure esthetics. The authors evaluated the effects of objective 3-dimensional (3D) facial shape and asymmetry measurements derived from 3D facial images on perceptions of facial attractiveness. The 3D facial images of 313 adults in Iowa were digitized with 32 landmarks, and objective 3D facial measurements capturing symmetric and asymmetric components of shape variation, centroid size, and fluctuating asymmetry were obtained from the 3D coordinate data using geo-morphometric analyses. Frontal and profile images of study participants were rated for facial attractiveness by 10 volunteers (5 women and 5 men) on a 5-point Likert scale and a visual analog scale. Multivariate regression was used to identify the effects of the objective 3D facial measurements on attractiveness ratings. Several objective 3D facial measurements had marked effects on attractiveness ratings. Shorter facial heights with protrusive chins, midface retrusion, faces with protrusive noses and thin lips, flat mandibular planes with deep labiomental folds, any cants of the lip commissures and floor of the nose, larger faces overall, and increased fluctuating asymmetry were rated as significantly (P < .001) less attractive. Perceptions of facial attractiveness can be explained by specific 3D measurements of facial shapes and fluctuating asymmetry, which have important implications for clinical practice and research. Copyright © 2017 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.
Searching surface orientation of microscopic objects for accurate 3D shape recovery.
Shim, Seong-O; Mahmood, Muhammad Tariq; Choi, Tae-Sun
2012-05-01
In this article, we propose a new shape from focus (SFF) method to estimate 3D shape of microscopic objects using surface orientation cue of each object patch. Most of the SFF algorithms compute the focus value of a pixel from the information of neighboring pixels lying on the same image frame based on an assumption that the small object patch corresponding to the small neighborhood of a pixel is a plane parallel to the focal plane. However, this assumption fails in the optics with limited depth of field where the neighboring pixels of an image have different degree of focus. To overcome this problem, we try to search the surface orientation of the small object patch corresponding to each pixel in the image sequence. Searching of the surface orientation is done indirectly by principal component analysis. Then, the focus value of each pixel is computed from the neighboring pixels lying on the surface perpendicular to the corresponding surface orientation. Experimental results on synthetic and real microscopic objects show that the proposed method produces more accurate 3D shape in comparison to the existing techniques.
NASA Astrophysics Data System (ADS)
Sharari, T. M.
2015-03-01
This paper presents a robotic system designed for holding and placing objects based on their colour and shape. The presented robot is given a complete set of instructions of positions and orientation angles for each manipulation motion. The main feature in this paper is that the developed robot used a combination of vision and motion systems for holding and placing the work-objects, mounted on the flat work-plane, based on their shapes and colors. This combination improves the flexibility of manipulation which may help eliminate the use of some expensive manipulation tasks in a variety of industrial applications. The robotic system presented in this paper is designed as an educational robot that possesses the ability for holding-and-placing operations with limited load. To process the various instructions for holding and placing the work objects, a main control unit - Manipulation Control Unit (MCU) is used as well as a slave unit that performed the actual instructions from the MCU.
Fast automated segmentation of multiple objects via spatially weighted shape learning
NASA Astrophysics Data System (ADS)
Chandra, Shekhar S.; Dowling, Jason A.; Greer, Peter B.; Martin, Jarad; Wratten, Chris; Pichler, Peter; Fripp, Jurgen; Crozier, Stuart
2016-11-01
Active shape models (ASMs) have proved successful in automatic segmentation by using shape and appearance priors in a number of areas such as prostate segmentation, where accurate contouring is important in treatment planning for prostate cancer. The ASM approach however, is heavily reliant on a good initialisation for achieving high segmentation quality. This initialisation often requires algorithms with high computational complexity, such as three dimensional (3D) image registration. In this work, we present a fast, self-initialised ASM approach that simultaneously fits multiple objects hierarchically controlled by spatially weighted shape learning. Prominent objects are targeted initially and spatial weights are progressively adjusted so that the next (more difficult, less visible) object is simultaneously initialised using a series of weighted shape models. The scheme was validated and compared to a multi-atlas approach on 3D magnetic resonance (MR) images of 38 cancer patients and had the same (mean, median, inter-rater) Dice’s similarity coefficients of (0.79, 0.81, 0.85), while having no registration error and a computational time of 12-15 min, nearly an order of magnitude faster than the multi-atlas approach.
Shaping biomedical objects across history and philosophy:a conversation with Hans-Jörg Rheinberger.
García-Sancho, Miguel; González-Silva, Matiana; Jesús Santesmases, María; Rheinberger, Hans-Jörg
2014-01-01
Historical epistemology, according to the historian of science Hans-Jörg Rheinberger, is a space through which "to take experimental laboratory work into the realm of philosophy". This key concept, together with the crucial events and challenges of his career, were discussed in a public conversation which took place on the occasion of Rheinberger's retirement. By making sense of natural phenomena in the laboratory, the act of experimenting shapes the object; it is this shaping which became the core of Rheinberger's own research across biology and philosophy into history. For his intellectual agenda, a history of the life sciences so constructed became "epistemologically demanding".
ERIC Educational Resources Information Center
Yonas, Albert; And Others
1987-01-01
A test for sensitivity to binocular disparity and a shape perception test were administered to four-month-olds. Results indicated that disparity-sensitive infants could perceive three-dimensional-object shape from kinetic and binocular depth information. (PCB)
Multi-objective shape and material optimization of composite structures including damping
NASA Technical Reports Server (NTRS)
Saravanos, D. A.; Chamis, Christos C.
1990-01-01
A multi-objective optimal design methodology is developed for light-weight, low cost composite structures of improved dynamic performance. The design objectives include minimization of resonance amplitudes (or maximization of modal damping), weight, and material cost. The design vector includes micromechanics, laminate, and structural shape parameters. Performance constraints are imposed on static displacements, dynamic amplitudes, and natural frequencies. The effects of damping on the dynamics of composite structures are incorporated. Preliminary applications on a cantilever composite beam illustrated that only the proposed multi-objective optimization, as opposed to single objective functions, simultaneously improved all objectives. The significance of composite damping in the design of advanced composite structures was also demonstrated, indicating the design methods based on undamped dynamics may fail to improve the dynamic performance near resonances.
Multi-objective shape and material optimization of composite structures including damping
NASA Technical Reports Server (NTRS)
Saravanos, D. A.; Chamis, C. C.
1990-01-01
A multi-objective optimal design methodology is developed for light-weight, low-cost composite structures of improved dynamic performance. The design objectives include minimization of resonance amplitudes (or maximization of modal damping), weight, and material cost. The design vector includes micromechanics, laminate, and structural shape parameters. Performance constraints are imposed on static displacements, dynamic amplitudes, and natural frequencies. The effects of damping on the dynamics of composite structures are incorporated. Preliminary applications on a cantilever composite beam illustrated that only the proposed multi-objective optimization, as opposed to single objective functions, simultaneously improved all objectives. The significance of composite damping in the design of advanced composite structures was also demonstrated, indicating that design methods based on undamped dynamics may fail to improve the dynamic performance near resonances.
Multi-objective shape and material optimization of composite structures including damping
NASA Technical Reports Server (NTRS)
Saravanos, D. A.; Chamis, C. C.
1990-01-01
A multi-objective optimal design methodology is developed for light-weight, low-cost composite structures of improved dynamic performance. The design objectives include minimization of resonance amplitudes (or maximization of modal damping), weight, and material cost. The design vector includes micromechanics, laminate, and structural shape parameters. Performance constraints are imposed on static displacements, dynamic amplitudes, and natural frequencies. The effects of damping on the dynamics of composite structures are incorporated. Preliminary applications on a cantilever composite beam illustrated that only the proposed multi-objective optimization, as opposed to single objective functions, simultaneously improved all objectives. The significance of composite damping in the design of advanced composite structures was also demonstrated, indicating that design methods based on undamped dynamics may fail to improve the dynamic performance near resonances.
Watson, Derrick G; Kunar, Melina A
2010-12-01
Visual search efficiency improves by presenting (previewing) one set of distractors before the target and remaining distractor items (D. G. Watson & G. W. Humphreys, 1997). Previous work has shown that this preview benefit is abolished if the old items change their shape when the new items are added (e.g., D. G. Watson & G. W. Humphreys, 2002). Here we present 5 experiments that examined whether such object changes are still effective in recapturing attention if the changes occur while the previewed objects are occluded or masked. Overall, the findings suggest that masking transients are effective in preventing both object changes and the presentation of new objects from capturing attention in time-based visual search conditions. The findings are discussed in relation to theories of change blindness, new object capture, and the ecological properties of time-based visual selection.
Smart agile lens remote optical sensor for three-dimensional object shape measurements.
Riza, Nabeel A; Reza, Syed Azer
2010-03-01
We demonstrate what is, to the best of our knowledge, the first electronically controlled variable focus lens (ECVFL)-based sensor for remote object shape sensing. Using a target illuminating laser, the axial depths of the shape features on a given object are measured by observing the intensity profile of the optical beam falling on the object surface and tuning the ECVFL focal length to form a minimum beam spot. Using a lens focal length control calibration table, the object feature depths are computed. Transverse measurement of the dimensions of each object feature is done using a surface-flooding technique that completely illuminates a given feature. Alternately, transverse measurements can also be made by the variable spatial sampling scan technique, where, depending upon the feature sizes, the spatial sampling spot beam size is controlled using the ECVFL. A proof-of-concept sensor is demonstrated using an optical beam from a laser source operating at a power of 10 mW and a wavelength of 633 nm. A three-dimensional (3D) test object constructed from LEGO building blocks forms has three mini-skyscraper structures labeled A, B, and C. The (x, y, z) dimensions for A, B, and C are (8 mm, 8 mm, 124.84 mm), (24.2 mm, 24.2 mm, 38.5 mm), and (15.86 mm, 15.86 mm, 86.74 mm), respectively. The smart sensor experimentally measured (x,y,z) dimensions for A, B, C are (7.95 mm, 7.95 mm, 120 mm), (24.1 mm, 24.1 mm, 37 mm), and (15.8 mm, 15.8 mm, 85 mm), respectively. The average shape sensor transverse measurement percentage errors for A, B, and C are +/-0.625%, +/-0.41%, and +/-0.38%, respectively. The average shape sensor axial measurement percentage errors for A, B, and C are +/-4.03%, +/-3.9%, and +/-2.01%, respectively. Applications for the proposed shape sensor include machine parts inspection, 3D object reconstruction, and animation.
Soft-Docking System for Capture of Irrecularly Shaped, Uncontrolled Space Objects
NASA Astrophysics Data System (ADS)
Branz, F.; Savioli, L.; Francesconi, A.; Sansone, F.; Krahn, J.; Menon, C.
2013-08-01
Over the last decades, the interest around Active Debris Removal missions grew considerably due to the increasing threat represented by the space debris populating near-Earth orbits. This paper presents the concept of a soft docking system suitable for capture of non-cooperative, large objects regardless of shape, surface features and motion. The innovative concept exploits a compliant electro-dry adhesive surface for mating and a robotic support structure composed by smart-material actuators. The adhesion surface combines electrostatic attraction and van der Waals forces; it is highly flexible and compliant to local irregularities of the target surface. The proposed capture concept increases the operative flexibility, tolerating critical scenario uncertainties (i.e. target shape, motion, mass). The active support structure can be controlled to adapt to the target object external geometry and to damp relative motion between target and chaser. Preliminary analysis was conducted both assessing the expected capture loads and the available adhesion forces.
Encountered-type Haptic Interface for Representation of Shape and Rigidity of 3D Virtual Objects.
Takizawa, Naoki; Yano, Hiroaki; Iwata, Hiroo; Oshiro, Yukio; Ohkohch, Nobuhiro
2017-08-17
This paper describes the development of an encountered-type haptic interface that can generate the physical characteristics, such as shape and rigidity, of three-dimensional (3D) virtual objects using an array of newly developed non-expandable balloons. To alter the rigidity of each non-expandable balloon, the volume of air in it is controlled through a linear actuator and a pressure sensor based on Hooke's law. Furthermore, to change the volume of each balloon, its exposed surface area is controlled by using another linear actuator with a trumpet-shaped tube. A position control mechanism is constructed to display virtual objects using the balloons. The 3D position of each balloon is controlled using a flexible tube and a string. The performance of the system is tested and the results confirm the effectiveness of the proposed principle and interface.
Fast laser systems for measuring the geometry of complex-shaped objects
NASA Astrophysics Data System (ADS)
Galiulin, Ravil M.; Galiulin, Rishat M.; Bakirov, J. M.; Vorontsov, A. V.; Ponomarenko, I. V.
1999-01-01
The technical characteristics, advantages and applications of an automated optoelectronic measuring system designed by 'Optel' company, State Aviation University of Ufa, are presented in this paper. The measuring apparatus can be applied for industrial development and research, for example, in rapid prototyping, and for obtaining geometrical parameters in medicine and criminalistics. It essentially is a non-contact and rapid scanning system, allowing measurements of complex shaped objects like metal and plastic workpieces or parts of human body.
Representations of Shape in Object Recognition and Long-Term Visual Memory
1993-02-11
Pinker (1989) proposed the Multiple- Views-Plus-Transformation theory of object recognition. The foundation of this theory is th at objecto a,- represented... Pinker (1990) have shown that such shapes are immediately and consistently recognized independently of their orientation. Consequentially, throughout...along which parts may be located. Tarr and Pinker have shown that such contrasts lead to the use of orientation-dependent recognition mechanisms utilizing
Monostatic Radar Cross Section Estimation of Missile Shaped Object Using Physical Optics Method
NASA Astrophysics Data System (ADS)
Sasi Bhushana Rao, G.; Nambari, Swathi; Kota, Srikanth; Ranga Rao, K. S.
2017-08-01
Stealth Technology manages many signatures for a target in which most radar systems use radar cross section (RCS) for discriminating targets and classifying them with regard to Stealth. During a war target’s RCS has to be very small to make target invisible to enemy radar. In this study, Radar Cross Section of perfectly conducting objects like cylinder, truncated cone (frustum) and circular flat plate is estimated with respect to parameters like size, frequency and aspect angle. Due to the difficulties in exactly predicting the RCS, approximate methods become the alternative. Majority of approximate methods are valid in optical region and where optical region has its own strengths and weaknesses. Therefore, the analysis given in this study is purely based on far field monostatic RCS measurements in the optical region. Computation is done using Physical Optics (PO) method for determining RCS of simple models. In this study not only the RCS of simple models but also missile shaped and rocket shaped models obtained from the cascaded objects with backscatter has been computed using Matlab simulation. Rectangular plots are obtained for RCS in dbsm versus aspect angle for simple and missile shaped objects using Matlab simulation. Treatment of RCS, in this study is based on Narrow Band.
Shape and micromotion parameters estimation of exoatmosphere object from the infrared signature
NASA Astrophysics Data System (ADS)
Wu, Yabei; Lu, Huanzhang; Liu, Junliang; Zhao, Fei
2017-03-01
The infrared signature has been used extensively to discriminate exoatmosphere objects. The performance of the discriminating system is heavily dependent on the choice of features. Although numerous features have been extracted, the shape and micromotion parameters still serve as important additional features. However, there is little research on extracting the shape and micromotion parameters from the infrared signature. An estimating method of the nutation angle and half cone angle for a precession conical object is investigated. The time variation of an IR signature is found to be complicated yet valuable for estimating the micromotion and shape parameters. Based on the fact that the temperature changes a small amount during a short interval, the band exitance of the object in a short time window is approximated to be a constant to reduce the number of the model parameters. A least square estimator is used to estimate the nutation angle and half cone angle from the IR signature. Simulation experiments and the resulting discussion are carried out to demonstrate the effectiveness of the proposed estimation method.
Davitt, Lina I; Cristino, Filipe; Wong, Alan C-N; Leek, E Charles
2014-04-01
This study examines the kinds of shape features that mediate basic- and subordinate-level object recognition. Observers were trained to categorize sets of novel objects at either a basic (between-families) or subordinate (within-family) level of classification. We analyzed the spatial distributions of fixations and compared them to model distributions of different curvature polarity (regions of convex or concave bounding contour), as well as internal part boundaries. The results showed a robust preference for fixation at part boundaries and for concave over convex regions of bounding contour, during both basic- and subordinate-level classification. In contrast, mean saccade amplitudes were shorter during basic- than subordinate-level classification. These findings challenge models of recognition that do not posit any special functional status to part boundaries or curvature polarity. We argue that both basic- and subordinate-level classification are mediated by object representations. These representations make explicit internal part boundaries, and distinguish concave and convex regions of bounding contour. The classification task constrains how shape information in these representations is used, consistent with the hypothesis that both parts-based, and image-based, operations support object recognition in human vision.
Extracting contours of oval-shaped objects by Hough transform and minimal path algorithms
NASA Astrophysics Data System (ADS)
Tleis, Mohamed; Verbeek, Fons J.
2014-04-01
Circular and oval-like objects are very common in cell and micro biology. These objects need to be analyzed, and to that end, digitized images from the microscope are used so as to come to an automated analysis pipeline. It is essential to detect all the objects in an image as well as to extract the exact contour of each individual object. In this manner it becomes possible to perform measurements on these objects, i.e. shape and texture features. Our measurement objective is achieved by probing contour detection through dynamic programming. In this paper we describe a method that uses Hough transform and two minimal path algorithms to detect contours of (ovoid-like) objects. These algorithms are based on an existing grey-weighted distance transform and a new algorithm to extract the circular shortest path in an image. The methods are tested on an artificial dataset of a 1000 images, with an F1-score of 0.972. In a case study with yeast cells, contours from our methods were compared with another solution using Pratt's figure of merit. Results indicate that our methods were more precise based on a comparison with a ground-truth dataset. As far as yeast cells are concerned, the segmentation and measurement results enable, in future work, to retrieve information from different developmental stages of the cell using complex features.
Object Recognition in Flight: How Do Bees Distinguish between 3D Shapes?
Werner, Annette; Stürzl, Wolfgang; Zanker, Johannes
2016-01-01
Honeybees (Apis mellifera) discriminate multiple object features such as colour, pattern and 2D shape, but it remains unknown whether and how bees recover three-dimensional shape. Here we show that bees can recognize objects by their three-dimensional form, whereby they employ an active strategy to uncover the depth profiles. We trained individual, free flying honeybees to collect sugar water from small three-dimensional objects made of styrofoam (sphere, cylinder, cuboids) or folded paper (convex, concave, planar) and found that bees can easily discriminate between these stimuli. We also tested possible strategies employed by the bees to uncover the depth profiles. For the card stimuli, we excluded overall shape and pictorial features (shading, texture gradients) as cues for discrimination. Lacking sufficient stereo vision, bees are known to use speed gradients in optic flow to detect edges; could the bees apply this strategy also to recover the fine details of a surface depth profile? Analysing the bees' flight tracks in front of the stimuli revealed specific combinations of flight maneuvers (lateral translations in combination with yaw rotations), which are particularly suitable to extract depth cues from motion parallax. We modelled the generated optic flow and found characteristic patterns of angular displacement corresponding to the depth profiles of our stimuli: optic flow patterns from pure translations successfully recovered depth relations from the magnitude of angular displacements, additional rotation provided robust depth information based on the direction of the displacements; thus, the bees flight maneuvers may reflect an optimized visuo-motor strategy to extract depth structure from motion signals. The robustness and simplicity of this strategy offers an efficient solution for 3D-object-recognition without stereo vision, and could be employed by other flying insects, or mobile robots.
Object Recognition in Flight: How Do Bees Distinguish between 3D Shapes?
Werner, Annette; Stürzl, Wolfgang; Zanker, Johannes
2016-01-01
Honeybees (Apis mellifera) discriminate multiple object features such as colour, pattern and 2D shape, but it remains unknown whether and how bees recover three-dimensional shape. Here we show that bees can recognize objects by their three-dimensional form, whereby they employ an active strategy to uncover the depth profiles. We trained individual, free flying honeybees to collect sugar water from small three-dimensional objects made of styrofoam (sphere, cylinder, cuboids) or folded paper (convex, concave, planar) and found that bees can easily discriminate between these stimuli. We also tested possible strategies employed by the bees to uncover the depth profiles. For the card stimuli, we excluded overall shape and pictorial features (shading, texture gradients) as cues for discrimination. Lacking sufficient stereo vision, bees are known to use speed gradients in optic flow to detect edges; could the bees apply this strategy also to recover the fine details of a surface depth profile? Analysing the bees’ flight tracks in front of the stimuli revealed specific combinations of flight maneuvers (lateral translations in combination with yaw rotations), which are particularly suitable to extract depth cues from motion parallax. We modelled the generated optic flow and found characteristic patterns of angular displacement corresponding to the depth profiles of our stimuli: optic flow patterns from pure translations successfully recovered depth relations from the magnitude of angular displacements, additional rotation provided robust depth information based on the direction of the displacements; thus, the bees flight maneuvers may reflect an optimized visuo-motor strategy to extract depth structure from motion signals. The robustness and simplicity of this strategy offers an efficient solution for 3D-object-recognition without stereo vision, and could be employed by other flying insects, or mobile robots. PMID:26886006
Arbitrarily slow, non-quasistatic, isothermal transformations
NASA Astrophysics Data System (ADS)
Gavrilov, Momčilo; Bechhoefer, John
2016-06-01
For an overdamped colloidal particle diffusing in a fluid in a controllable, virtual potential, we show that arbitrarily slow transformations, produced by smooth deformations of a double-well potential, need not be reversible. The arbitrarily slow transformations do need to be fast compared to the barrier crossing time, but that time can be extremely long. We consider two types of cyclic, isothermal transformations of a double-well potential. Both start and end in the same equilibrium state, and both use the same basic operations —but in different order. By measuring the work for finite cycle times and extrapolating to infinite times, we found that one transformation required no work, while the other required a finite amount of work, no matter how slowly it was carried out. The difference traces back to the observation that when time is reversed, the two protocols have different outcomes, when carried out arbitrarily slowly. A recently derived formula relating work production to the relative entropy of forward and backward path probabilities predicts the observed work average.
Measuring the 3D shape of high temperature objects using blue sinusoidal structured light
NASA Astrophysics Data System (ADS)
Zhao, Xianling; Liu, Jiansheng; Zhang, Huayu; Wu, Yingchun
2015-12-01
The visible light radiated by some high temperature objects (less than 1200 °C) almost lies in the red and infrared waves. It will interfere with structured light projected on a forging surface if phase measurement profilometry (PMP) is used to measure the shapes of objects. In order to obtain a clear deformed pattern image, a 3D measurement method based on blue sinusoidal structured light is proposed in this present work. Moreover, a method for filtering deformed pattern images is presented for correction of the unwrapping phase. Blue sinusoidal phase-shifting fringe pattern images are projected on the surface by a digital light processing (DLP) projector, and then the deformed patterns are captured by a 3-CCD camera. The deformed pattern images are separated into R, G and B color components by the software. The B color images filtered by a low-pass filter are used to calculate the fringe order. Consequently, the 3D shape of a high temperature object is obtained by the unwrapping phase and the calibration parameter matrixes of the DLP projector and 3-CCD camera. The experimental results show that the unwrapping phase is completely corrected with the filtering method by removing the high frequency noise from the first harmonic of the B color images. The measurement system can complete the measurement in a few seconds with a relative error of less than 1 : 1000.
Ashby, Samantha E; Snodgrass, Suzanne H; Rivett, Darren A; Russell, Trevor
2016-09-01
The development of student-practitioners' practical clinical skills is essential in health professional education. Objective Structured Clinical Examinations are central to the assessment of students performing clinical procedures on simulated patients (actors). While feedback is considered core to learning providing timely, individualised student OSCE feedback is difficult. This study explored the perceptions of students about the multiple factors which shape the utility of e-feedback following an electronic Objective Structured Clinical Examinations, which utilized iPad and specialised software. The e-feedback was trialled in four courses within occupational therapy and physiotherapy pre-professional programs with a cohort of 204 students. Evaluation of student perceptions about feedback was collected using two surveys and eight focus groups. This data showed three factors shaped perceptions of the utility of e- Objective Structured Clinical Examinations feedback: 1) timely accessibility within one day of the assessment, 2) feedback demonstrating examiners' academic literacy and 3) feedback orientated to ways of improving future performance of clinical skills. The study found training in the provision of feedback using IPads and software is needed for examiners to ensure e-feedback meets students' needs for specific, future-oriented e-feedback and institutional requirements for justification of grades.
NASA Astrophysics Data System (ADS)
Mesa, F.; Medina, F.
2006-12-01
This work presents a new implementation of the mixed potential integral equation (MPIE) for planar structures that can include ferrite layers arbitrarily magnetized. The implementation of the MPIE here reported is carried out in the space domain. Thus it will combine the well-known numerical advantages of working with potentials as well as the flexibility for analyzing nonrectangular shape conductors with the additional ability of including anisotropic layers of arbitrarily magnetized ferrites. In this way, our approach widens the scope of the space domain MPIE and sets this method as a very efficient and versatile numerical tool to deal with a wide class of planar microwave circuits and antennas.
Outline shape is a mediator of object recognition that is particularly important for living things.
Lloyd-Jones, Toby J; Luckhurst, Linda
2002-06-01
We assess the importance of outline shape in mediating the recognition of living and nonliving things. Natural objects were presented as shaded line drawings or silhouettes, and were living and nonliving things. For object decision (deciding whether an object may be encountered in real life) there were longer response times to nonliving than to living things. Importantly, this category difference was greater for silhouettes than for shaded line drawings. For naming, similar category and stimulus differences were evident, but were not as pronounced. We also examined effects of prior naming on subsequent object decision performance. Repetition priming was equivalent for nonliving and living things. However, prior presentation of silhouettes (but not shaded line drawings) reduced the longer RT to nonliving things relative to living things in silhouette object decision. We propose that outline contour benefits recognition of living things more than nonliving things: For nonliving things, there may be greater 2-D/3-D interpretational ambiguity, and/or they may possess fewer salient features.
Implicit Shape Models for Object Detection in 3d Point Clouds
NASA Astrophysics Data System (ADS)
Velizhev, A.; Shapovalov, R.; Schindler, K.
2012-07-01
We present a method for automatic object localization and recognition in 3D point clouds representing outdoor urban scenes. The method is based on the implicit shape models (ISM) framework, which recognizes objects by voting for their center locations. It requires only few training examples per class, which is an important property for practical use. We also introduce and evaluate an improved version of the spin image descriptor, more robust to point density variation and uncertainty in normal direction estimation. Our experiments reveal a significant impact of these modifications on the recognition performance. We compare our results against the state-of-the-art method and get significant improvement in both precision and recall on the Ohio dataset, consisting of combined aerial and terrestrial LiDAR scans of 150,000 m2 of urban area in total.
NASA Astrophysics Data System (ADS)
Cao, Pei; Yoo, David; Shuai, Qi; Tang, J.
2017-04-01
Structural damage identification has been continuously pursued in engineering practices to facilitate diagnosis and prognosis in structural health monitoring (SHM) systems. In SHM, the changes of modal parameters are frequently used as inputs. In this research, we employ the multiple damage location assurance criterion (MDLAC) to characterize the correlation between predictions of both frequency changes and single mode shape change with the measured data. The damage locations and severities can be obtained by maximizing the MDLAC values. Thereafter, a multi-objective optimization problem based on their MDLAC values can be formulated and optimized by applying a newly devised multi-objective DIRECT approach. The proposed approach offers practical attractions of only requiring a short amount of computational time, and the results are conclusive and repeatable.
NASA Astrophysics Data System (ADS)
Pfister, Thorsten; Günther, Philipp; Büttner, Lars; Czarske, Jürgen
2008-09-01
In this contribution a novel laser Doppler distance (LDD) sensor is presented, which allows simultaneous measurement of axial position and tangential velocity and, thus, determination of the shape of moving and especially rotating objects with one single sensor. Conventional laser Doppler velocimeters measure only velocities. A concurrent position measurement can be realized by generating two fan-shaped interference fringe systems with contrary fringe spacing gradients and evaluating the quotient of the two resulting Doppler frequencies. Alternatively, two tilted fringe systems in combination with phase evaluation can be employed. It will be shown that, in contrast to conventional distance sensors, high temporal resolution below 3 μs and high position resolution of about 1 μm can be achieved simultaneously, because the position uncertainty of the LDD sensor is in principle independent of the object velocity. This is advantageous especially for monitoring highly dynamic processes e.g. at turbo machines, where in-process measurements of tip clearance and rotor vibrations are reported for up to 600 m/s blade tip velocity.
Shape and vibration measurement of fast rotating objects employing novel laser Doppler techniques
NASA Astrophysics Data System (ADS)
Pfister, Thorsten; Günther, Philipp; Büttner, Lars; Czarske, Jürgen
2007-06-01
This contribution presents novel laser Doppler techniques, which allow simultaneous measurement of radial position and tangential velocity and, thus, determination of the shape of rotating objects with one single sensor. Conventional laser Doppler velocimeters measure only velocities. A concurrent position measurement can be realized by generating two fan-like interference fringe systems with contrary fringe spacing gradients and evaluating the quotient of the two resulting Doppler frequencies. Alternatively, two tilted fringe systems in combination with phase evaluation can be employed. It is shown that the position uncertainty of this sensor is not only independent of the surface roughness but, most notably, that it is in principle independent of the object velocity. Thus, in contrast to conventional distance sensors, the novel laser Doppler position sensor offers high temporal resolution below 3 μs and high position resolution in the micrometer range simultaneously. The sensor was applied to automatic 3D shape measurements of turning parts and to monitoring rotor unbalance and dynamic deformations. Furthermore, in situ measurements of tip clearance and rotor vibrations at turbo machines for up to 600 m/s blade tip velocity are reported. The results are in excellent agreement with those of triangulation and capacitive probes, respectively.
Multifeatural shape processing in rats engaged in invariant visual object recognition.
Alemi-Neissi, Alireza; Rosselli, Federica Bianca; Zoccolan, Davide
2013-04-03
The ability to recognize objects despite substantial variation in their appearance (e.g., because of position or size changes) represents such a formidable computational feat that it is widely assumed to be unique to primates. Such an assumption has restricted the investigation of its neuronal underpinnings to primate studies, which allow only a limited range of experimental approaches. In recent years, the increasingly powerful array of optical and molecular tools that has become available in rodents has spurred a renewed interest for rodent models of visual functions. However, evidence of primate-like visual object processing in rodents is still very limited and controversial. Here we show that rats are capable of an advanced recognition strategy, which relies on extracting the most informative object features across the variety of viewing conditions the animals may face. Rat visual strategy was uncovered by applying an image masking method that revealed the features used by the animals to discriminate two objects across a range of sizes, positions, in-depth, and in-plane rotations. Noticeably, rat recognition relied on a combination of multiple features that were mostly preserved across the transformations the objects underwent, and largely overlapped with the features that a simulated ideal observer deemed optimal to accomplish the discrimination task. These results indicate that rats are able to process and efficiently use shape information, in a way that is largely tolerant to variation in object appearance. This suggests that their visual system may serve as a powerful model to study the neuronal substrates of object recognition.
Secondary pattern computation of an arbitrarily shaped main reflector
NASA Technical Reports Server (NTRS)
Lee, S. W.; Lam, P. T. C.; Acosta, R. J.
1985-01-01
The secondary pattern of a perfectly conducting offset main reflector being illuminated by a point feed at an arbitrary location is studied. The method of analysis is based upon the application of the Fast Fourier Transform (FFT) to the aperture fields obtained using geometrical optics (GO) and geometrical theory of diffraction (GTD). Key features of the present work are (1) the reflector surface is completely arbitrary, (2) the incident field from the feed is most general with arbitrary polarization and location, and (3) the edge diffraction is calculated by either UAT or by UTD. Comparison of this technique for an offset parabolic reflector with the Jacobi-Bessel and Fourier-Bessel techniques shows good agreement. Near field, far field, and scan data of a large refelctor are presented.
Secondary pattern computation of an arbitrarily shaped main reflector
NASA Technical Reports Server (NTRS)
Lam, P. T. C.; Lee, S. W.; Acosta, R.
1984-01-01
The secondary pattern of a perfectly conducting offset main reflector being illuminated by a point feed at an arbitrary location was studied. The method of analysis is based upon the application of the Fast Fourier Transform (FFT) to the aperture fields obtained using geometrical optics (GO) and geometrical theory of diffraction (GTD). Key features of the reflector surface is completely arbitrary, the incident field from the feed is most general with arbitrary polarization and location, and the edge diffraction is calculated by either UAT or by UTD. Comparison of this technique for an offset parabolic reflector with the Jacobi-Bessel and Fourier-Bessel techniques shows good agreement. Near field, far field, and scan data of a large reflector are presented.
Leek, E Charles; Roberts, Mark; Oliver, Zoe J; Cristino, Filipe; Pegna, Alan J
2016-08-01
Here we investigated the time course underlying differential processing of local and global shape information during the perception of complex three-dimensional (3D) objects. Observers made shape matching judgments about pairs of sequentially presented multi-part novel objects. Event-related potentials (ERPs) were used to measure perceptual sensitivity to 3D shape differences in terms of local part structure and global shape configuration - based on predictions derived from hierarchical structural description models of object recognition. There were three types of different object trials in which stimulus pairs (1) shared local parts but differed in global shape configuration; (2) contained different local parts but shared global configuration or (3) shared neither local parts nor global configuration. Analyses of the ERP data showed differential amplitude modulation as a function of shape similarity as early as the N1 component between 146-215ms post-stimulus onset. These negative amplitude deflections were more similar between objects sharing global shape configuration than local part structure. Differentiation among all stimulus types was reflected in N2 amplitude modulations between 276-330ms. sLORETA inverse solutions showed stronger involvement of left occipitotemporal areas during the N1 for object discrimination weighted towards local part structure. The results suggest that the perception of 3D object shape involves parallel processing of information at local and global scales. This processing is characterised by relatively slow derivation of 'fine-grained' local shape structure, and fast derivation of 'coarse-grained' global shape configuration. We propose that the rapid early derivation of global shape attributes underlies the observed patterns of N1 amplitude modulations.
Prior Knowledge of Object Associations Shapes Attentional Templates and Information Acquisition.
Wu, Rachel; Zhao, Jiaying
2017-01-01
Studies on attentional selection typically use unpredictable and meaningless stimuli, such as simple shapes and oriented lines. The assumption is that using these stimuli minimizes effects due to learning or prior knowledge, such that the task performance indexes a "pure" measure of the underlying cognitive ability. However, prior knowledge of the test stimuli and related stimuli acquired before or during the task impacts performance in meaningful ways. This mini review focuses on prior knowledge of object associations, because it is an important, yet often ignored, aspect of attentional selection. We first briefly review recent studies demonstrating that how objects are selected during visual search depends on the participant's prior experience with other objects associated with the target. These effects appear with both task-relevant and task-irrelevant knowledge. We then review how existing object associations may influence subsequent learning of new information, which is both a driver and a consequence of selection processes. These insights highlight the importance of one aspect of prior knowledge for attentional selection and information acquisition. We briefly discuss how this work with young adults may inform other age groups throughout the lifespan, as learners gradually increase their prior knowledge. Importantly, these insights have implications for developing more accurate measurements of cognitive abilities.
NASA Astrophysics Data System (ADS)
Stoja, Endri; Hoxha, Julian; Domnori, Elton; Pajewski, Lara; Frezza, Fabrizio
2017-04-01
In this study the electromagnetic field scattered by a buried object is obtained by use of a commercial full-wave frequency-domain solver which implements the Finite Element Method (FEM). The buried object is supposed to have different simple shapes and material composition such as a cylinder or cylindrical shell modelling for example a void in concrete or a poly-vinyl chloride (PVC) pipeline, respectively. Material properties available in literature are correctly modelled by data interpolation. The model is excited by a linearly-polarized plane wave impinging normally on the interface between air and soil/cement half-space. Comparison with simulation data provided by another simulator implementing the finite-difference time domain (FDTD) technique in the case of a simple buried perfect electric cylinder allows for FEM data validation. We further study the properties and the spatial variation of the scattered fields in different contexts by varying the geometrical and material properties of the model relative to the impinging wave characteristics. The aim is to clearly determine the conditions under which detection is possible. Moreover, by application of signal processing techniques to scattered field data, the position, shape, and object orientation recognition problems are considered. Results from different DSP algorithms are compared with the goal to find the best performing one relative to the context. Performance is evaluated in terms of detection success and resolving ability. The use of ground penetrating radar (GPR) techniques in the field of Civil Engineering offers inspection capabilities in the structure with no destructive intervention. Acknowledgement This abstract is a contribution to COST Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar", www.GPRadar.eu, www.cost.eu.
ERIC Educational Resources Information Center
Bremner, J. Gavin; Slater, Alan M.; Mason, Uschi C.; Spring, Jo; Johnson, Scott P.
2013-01-01
Previous work has demonstrated that infants use object trajectory continuity as a cue to the constant identity of an object, but results are equivocal regarding the role of object features, with some work suggesting that a change in the appearance of an object does not cue a change in identity. In an experiment involving 72 participants, we…
ERIC Educational Resources Information Center
Bremner, J. Gavin; Slater, Alan M.; Mason, Uschi C.; Spring, Jo; Johnson, Scott P.
2013-01-01
Previous work has demonstrated that infants use object trajectory continuity as a cue to the constant identity of an object, but results are equivocal regarding the role of object features, with some work suggesting that a change in the appearance of an object does not cue a change in identity. In an experiment involving 72 participants, we…
Multi-objective shape optimization of runner blade for Kaplan turbine
NASA Astrophysics Data System (ADS)
Semenova, A.; Chirkov, D.; Lyutov, A.; Chemy, S.; Skorospelov, V.; Pylev, I.
2014-03-01
Automatic runner shape optimization based on extensive CFD analysis proved to be a useful design tool in hydraulic turbomachinery. Previously the authors developed an efficient method for Francis runner optimization. It was successfully applied to the design of several runners with different specific speeds. In present work this method is extended to the task of a Kaplan runner optimization. Despite of relatively simpler blade shape, Kaplan turbines have several features, complicating the optimization problem. First, Kaplan turbines normally operate in a wide range of discharges, thus CFD analysis of each variant of the runner should be carried out for several operation points. Next, due to a high specific speed, draft tube losses have a great impact on the overall turbine efficiency, and thus should be accurately evaluated. Then, the flow in blade tip and hub clearances significantly affects the velocity profile behind the runner and draft tube behavior. All these features are accounted in the present optimization technique. Parameterization of runner blade surface using 24 geometrical parameters is described in details. For each variant of runner geometry steady state three-dimensional turbulent flow computations are carried out in the domain, including wicket gate, runner, draft tube, blade tip and hub clearances. The objectives are maximization of efficiency in best efficiency and high discharge operation points, with simultaneous minimization of cavitation area on the suction side of the blade. Multiobjective genetic algorithm is used for the solution of optimization problem, requiring the analysis of several thousands of runner variants. The method is applied to optimization of runner shape for several Kaplan turbines with different heads.
Pole-Shaped Object Detection Using Mobile LIDAR Data in Rural Road Environments
NASA Astrophysics Data System (ADS)
Yadav, M.; Husain, A.; Singh, A. K.; Lohani, B.
2015-08-01
Pole-shaped objects (PSOs) located along a road play key role in road safety and planning. Automation is required for calculating the numbers of trees need to be removed and utility poles need to be relocated during rural road widening. Road-side poles are among the most frequently struck road-side objects during road-side accidents. An automatic method is therefore proposed for detecting PSOs using LiDAR point cloud captured along the roadway using Mobile LiDAR system. The proposed method is tested on the point cloud data of rural road environment in India. Dataset of study area having text file size of 1.22 GB is processed in 13 minutes resulting in completeness of 88.63 % and correctness of 95.12 % in identifying PSOs within 10m of the road boundary. In data of across road coverage of 5m of the road boundary, the completeness of 93.10 % and correctness of 100% are achieved. Poles attached with other objects, tilted poles and the poles occluded by tree branches and shrubs are detected by the proposed method.
Camargo, Anyela; Papadopoulou, Dimitra; Spyropoulou, Zoi; Vlachonasios, Konstantinos; Doonan, John H; Gay, Alan P
2014-01-01
Computer-vision based measurements of phenotypic variation have implications for crop improvement and food security because they are intrinsically objective. It should be possible therefore to use such approaches to select robust genotypes. However, plants are morphologically complex and identification of meaningful traits from automatically acquired image data is not straightforward. Bespoke algorithms can be designed to capture and/or quantitate specific features but this approach is inflexible and is not generally applicable to a wide range of traits. In this paper, we have used industry-standard computer vision techniques to extract a wide range of features from images of genetically diverse Arabidopsis rosettes growing under non-stimulated conditions, and then used statistical analysis to identify those features that provide good discrimination between ecotypes. This analysis indicates that almost all the observed shape variation can be described by 5 principal components. We describe an easily implemented pipeline including image segmentation, feature extraction and statistical analysis. This pipeline provides a cost-effective and inherently scalable method to parameterise and analyse variation in rosette shape. The acquisition of images does not require any specialised equipment and the computer routines for image processing and data analysis have been implemented using open source software. Source code for data analysis is written using the R package. The equations to calculate image descriptors have been also provided.
Camargo, Anyela; Papadopoulou, Dimitra; Spyropoulou, Zoi; Vlachonasios, Konstantinos; Doonan, John H.; Gay, Alan P.
2014-01-01
Computer-vision based measurements of phenotypic variation have implications for crop improvement and food security because they are intrinsically objective. It should be possible therefore to use such approaches to select robust genotypes. However, plants are morphologically complex and identification of meaningful traits from automatically acquired image data is not straightforward. Bespoke algorithms can be designed to capture and/or quantitate specific features but this approach is inflexible and is not generally applicable to a wide range of traits. In this paper, we have used industry-standard computer vision techniques to extract a wide range of features from images of genetically diverse Arabidopsis rosettes growing under non-stimulated conditions, and then used statistical analysis to identify those features that provide good discrimination between ecotypes. This analysis indicates that almost all the observed shape variation can be described by 5 principal components. We describe an easily implemented pipeline including image segmentation, feature extraction and statistical analysis. This pipeline provides a cost-effective and inherently scalable method to parameterise and analyse variation in rosette shape. The acquisition of images does not require any specialised equipment and the computer routines for image processing and data analysis have been implemented using open source software. Source code for data analysis is written using the R package. The equations to calculate image descriptors have been also provided. PMID:24804972
Pfister, Thorsten; Büttner, Lars; Czarske, Jürgen
2009-01-01
For monitoring the position and shape of fast moving and, especially, rotating objects such as turbo machine rotors, contactless and compact sensors with a high measurement rate as well as high precision are required. We present for the first time, to the best of our knowledge, a novel laser Doppler sensor employing a single fan-shaped interference fringe system, which allows measuring for the position and shape of fast moving solid bodies with known tangential velocity. It is shown theoretically as well as experimentally that this sensor offers concurrently high position resolution and high temporal resolution in contrast to conventional measurement techniques, since its measurement uncertainty is, in principle, independent of the object velocity. Moreover, it can be built very compact, because it features low complexity. To prove its operational capability and its potential for practical applications, radial and axial shape measurements of rotating bodies are demonstrated in comparison with triangulation. An average position resolution of about 2 microm could be achieved.
Haptic discrimination of object shape in humans: two-dimensional angle discrimination.
Voisin, Julien; Benoit, Geneviève; Chapman, C Elaine
2002-07-01
The human ability to recognize objects on the basis of their shape, as defined by active exploratory movements, is dependent on sensory feedback from mechanoreceptors located both in the skin and in deep structures ( haptic feedback). Surprisingly, we have little information about the mechanisms for integrating these different signals into a single sensory percept. With the eventual aim of studying the underlying central neural mechanisms, we developed a shape discrimination test that required active exploration of objects, but was restricted to one component of shape, two-dimensional (2D) angles. The angles were machined from 1-cm-thick Plexiglas, and consisted of two 8-cm-long arms that met to form an angle of 90 degrees (standard) or 91 degrees to 103 degrees (comparison angles). Subjects scanned pairs of angles with the index finger of the outstretched arm and identified the larger angle of each pair explored. Discrimination threshold (75% correct) was 4.7 degrees (range 0.7 degrees to 12.1 degrees), giving a precision of 5.2% (0.8-13.4%: difference/standard). Repeated blocks of trials, either in the same session or on different days, had no effect on discrimination threshold. In contrast, the motor strategy was partly modified: scanning speed increased but dwell-time at the intersection did not change. Finally, 2D angle discrimination was not significantly modified by rotating the orientation of one of the angles in the pair (0 degrees, 4 degrees or 8 degrees rotation towards the midline, in the vertical plane), providing evidence that subjects evaluated each angle independently in each trial. Subject reports indicated that they relied on cutaneous feedback from the exploring digit (amount of compression of the finger at the angle) and mental images of the angles, most likely arising from proprioceptive information (from the shoulder) generated during the to-and-fro scans over the angle. In terms of shoulder angles, the mean discrimination threshold here was 0
NASA Astrophysics Data System (ADS)
Willomitzer, Florian; Ettl, Svenja; Arold, Oliver; Häusler, Gerd
2013-05-01
The three-dimensional shape acquisition of objects has become more and more important in the last years. Up to now, there are several well-established methods which already yield impressive results. However, even under quite common conditions like object movement or a complex shaping, most methods become unsatisfying. Thus, the 3D shape acquisition is still a difficult and non-trivial task. We present our measurement principle "Flying Triangulation" which enables a motion-robust 3D acquisition of complex-shaped object surfaces by a freely movable handheld sensor. Since "Flying Triangulation" is scalable, a whole sensor-zoo for different object sizes is presented. Concluding, an overview of current and future fields of investigation is given.
2015-02-25
Services (DLA DS) is facing substantial potential budget cuts, which will require the organization to increase efficiency and cut costs. DLA DS is assessing...the feasibility to improve the item disposal process with an object/shape recognition technology as a. means to increase efficiency . The technology...assessed obj ect/shape recognition technologies as a. means to suppmi efficiency while taking into account wider govenunent policy and objectives in
3D shape measurement of objects with high dynamic range of surface reflectivity
NASA Astrophysics Data System (ADS)
Liu, Gui-Hua; Liu, Xian-Yong; Feng, Quan-Yuan
2011-08-01
This paper presents a method that allows a conventional dual-camera structured light system to directly acquire the three-dimensional shape of the whole surface of an object with high dynamic range of surface reflectivity. To reduce the degradation in area-based correlation caused by specular highlights and diffused darkness, we first disregard these highly specular and dark pixels. Then, to solve this problem and further obtain unmatched area data, this binocular vision system was also used as two camera-projector monocular systems operated from different viewing angles at the same time to fill in missing data of the binocular reconstruction. This method involves producing measurable images by integrating such techniques as multiple exposures and high dynamic range imaging to ensure the capture of high-quality phase of each point. An image-segmentation technique was also introduced to distinguish which monocular system is suitable to reconstruct a certain lost point accurately. Our experiments demonstrate that these techniques extended the measurable areas on the high dynamic range of surface reflectivity such as specular objects or scenes with high contrast to the whole projector-illuminated field.
Rommers, Joost; Meyer, Antje S; Praamstra, Peter; Huettig, Falk
2013-02-01
When comprehending concrete words, listeners and readers can activate specific visual information such as the shape of the words' referents. In two experiments we examined whether such information can be activated in an anticipatory fashion. In Experiment 1, listeners' eye movements were tracked while they were listening to sentences that were predictive of a specific critical word (e.g., "moon" in "In 1969 Neil Armstrong was the first man to set foot on the moon"). 500 ms before the acoustic onset of the critical word, participants were shown four-object displays featuring three unrelated distractor objects and a critical object, which was either the target object (e.g., moon), an object with a similar shape (e.g., tomato), or an unrelated control object (e.g., rice). In a time window before shape information from the spoken target word could be retrieved, participants already tended to fixate both the target and the shape competitors more often than they fixated the control objects, indicating that they had anticipatorily activated the shape of the upcoming word's referent. This was confirmed in Experiment 2, which was an ERP experiment without picture displays. Participants listened to the same lead-in sentences as in Experiment 1. The sentence-final words corresponded to the predictable target, the shape competitor, or the unrelated control object (yielding, for instance, "In 1969 Neil Armstrong was the first man to set foot on the moon/tomato/rice"). N400 amplitude in response to the final words was significantly attenuated in the shape-related compared to the unrelated condition. Taken together, these results suggest that listeners can activate perceptual attributes of objects before they are referred to in an utterance. Copyright © 2012 Elsevier Ltd. All rights reserved.
NASA Astrophysics Data System (ADS)
Yen, Sidney; Kondraske, George V.
1992-02-01
A hierarchical shape decomposition method called Convex-Hull Carving, derived from Sklansky's Concavity Tree and designed to accommodate the incorporation of human flexible resolution visual perception strategies in machine recognition, is proposed. The method characterizes an arbitrary complex shape at multiple hierarchical levels starting from a gross perspective of the entire shape itself, and progressing to decomposed and quantified convex sub-shapes, etc. Calculation complexity and the amount of data to be processed for object recognition applications are reduced. Sklansky's Concavity Tree is a hierarchical arrangement for describing nonconvex shapes. The concavity tree of a shape is defined as a tree describing the hierarchical arrangement of concavities; i.e., concavities within concavities. In the proposed Convex-Hull Carving method, the concavity tree structure is converted to a structure analogous to a chemical molecule. Tree components represent the `atoms' of the molecule and are characterized by their geometric position and a recently defined quantitative shape attribute called the shape quantifier. In addition, the number of hierarchical levels of shape description employed during recognition is driven by: (1) meeting `need to discriminate' criteria; or (2) the determination that all components (`atoms') are convex within predefined acceptance criteria (i.e., no further reduction is possible). The method was implemented to classify a set of two-dimensional aircraft shapes. Results showed that the method is stable with variation of rotation, scaling, and image resolution factors, as well as small viewing angle projection changes.
NASA Astrophysics Data System (ADS)
Ali, Sahirzeeshan; Madabhushi, Anant
2011-03-01
Active contours and active shape models (ASM) have been widely employed in image segmentation. A major limitation of active contours, however, is in their (a) inability to resolve boundaries of intersecting objects and to (b) handle occlusion. Multiple overlapping objects are typically segmented out as a single object. On the other hand, ASMs are limited by point correspondence issues since object landmarks need to be identified across multiple objects for initial object alignment. ASMs are also are constrained in that they can usually only segment a single object in an image. In this paper, we present a novel synergistic boundary and region-based active contour model that incorporates shape priors in a level set formulation. We demonstrate an application of these synergistic active contour models using multiple level sets to segment nuclear and glandular structures on digitized histopathology images of breast and prostate biopsy specimens. Unlike previous related approaches, our model is able to resolve object overlap and separate occluded boundaries of multiple objects simultaneously. The energy functional of the active contour is comprised of three terms. The first term comprises the prior shape term, modeled on the object of interest, thereby constraining the deformation achievable by the active contour. The second term, a boundary based term detects object boundaries from image gradients. The third term drives the shape prior and the contour towards the object boundary based on region statistics. The results of qualitative and quantitative evaluation on 100 prostate and 14 breast cancer histology images for the task of detecting and segmenting nuclei, lymphocytes, and glands reveals that the model easily outperforms two state of the art segmentation schemes (Geodesic Active Contour (GAC) and Roussons shape based model) and resolves up to 92% of overlapping/occluded lymphocytes and nuclei on prostate and breast cancer histology images.
Computational techniques to enable visualizing shapes of objects of extra spatial dimensions
NASA Astrophysics Data System (ADS)
Black, Don Vaughn, II
Envisioning extra dimensions beyond the three of common experience is a daunting challenge for three dimensional observers. Intuition relies on experience gained in a three dimensional environment. Gaining experience with virtual four dimensional objects and virtual three manifolds in four-space on a personal computer may provide the basis for an intuitive grasp of four dimensions. In order to enable such a capability for ourselves, it is first necessary to devise and implement a computationally tractable method to visualize, explore, and manipulate objects of dimension beyond three on the personal computer. A technology is described in this dissertation to convert a representation of higher dimensional models into a format that may be displayed in realtime on graphics cards available on many off-the-shelf personal computers. As a result, an opportunity has been created to experience the shape of four dimensional objects on the desktop computer. The ultimate goal has been to provide the user a tangible and memorable experience with mathematical models of four dimensional objects such that the user can see the model from any user selected vantage point. By use of a 4D GUI, an arbitrary convex hull or 3D silhouette of the 4D model can be rotated, panned, scrolled, and zoomed until a suitable dimensionally reduced view or Aspect is obtained. The 4D GUI then allows the user to manipulate a 3-flat hyperplane cutting tool to slice the model at an arbitrary orientation and position to extract or "pluck" an embedded 3D slice or "aspect" from the embedding four-space. This plucked 3D aspect can be viewed from all angles via a conventional 3D viewer using three multiple POV viewports, and optionally exported to a third party CAD viewer for further manipulation. Plucking and Manipulating the Aspect provides a tangible experience for the end-user in the same manner as any 3D Computer Aided Design viewing and manipulation tool does for the engineer or a 3D video game provides
Effect of Gaussian curvature modulus on the shape of deformed hollow spherical objects.
Quilliet, C; Farutin, A; Marmottant, P
2016-06-01
A popular description of soft membranes uses the surface curvature energy introduced by Helfrich, which includes a spontaneous curvature parameter. In this paper we show how the Helfrich formula can also be of interest for a wider class of spherical elastic surfaces, namely with shear elasticity, and likely to model other deformable hollow objects. The key point is that when a stress-free state with spherical symmetry exists before subsequent deformation, its straightforwardly determined curvature ("geometrical spontaneous curvature") differs most of the time from the Helfrich spontaneous curvature parameter that should be considered in order to have the model being correctly used. Using the geometrical curvature in a set of independent parameters unveils the role of the Gaussian curvature modulus, which appears to play on the shape of an elastic surface even though this latter is closed, contrary to what happens for surfaces without spontaneous curvature. In appendices, clues are given to apply this alternative and convenient formulation of the elastic surface model to the particular case of thin spherical shells of isotropic material (TSSIMs).
Object-adapted trapping and shape-tracking to probe a bacterial protein chain motor
NASA Astrophysics Data System (ADS)
Roth, Julian; Koch, Matthias; Rohrbach, Alexander
2015-03-01
The helical bacterium Spiroplasma is a motile plant and anthropod pathogen which swims by propagating pairs of kinks along its cell body. As a well suited model system for bacterial locomotion, understanding the cell's molecular motor is of vital interest also regarding the combat of bacterial diseases. The extensive deformations related to these kinks are caused by a contractile cytoskeletal protein ribbon representing a linear motor in contrast to common rotary motors as, e.g., flagella. We present new insights into the working of this motor through experiments with object-adapted optical traps and shape-tracking techniques. We use the given laser irradiation from the optical trap to hinder bacterial energy (ATP) production through the production of O2 radicals. The results are compared with experiments performed under the influence of an O2-Scavenger and ATP inhibitors, respectively. Our results show clear dependences of the kinking properties on the ATP concentration inside the bacterium. The experiments are supported by a theoretical model which we developed to describe the switching of the ribbon's protein subunits.
Braida, Daniela; Donzelli, Andrea; Martucci, Roberta; Ponzoni, Luisa; Pauletti, Alberto; Langus, Alan; Sala, Mariaelvina
2013-04-01
Selective attention can be assessed with the novel object recognition (NOR) test. In the standard version of this test the selection of objects to be used is critical. We created a modified version of NOR, the virtual object recognition test (VORT) in mice, where the 3D objects were replaced with highly discriminated geometrical shapes and presented on two 3.5-inch widescreen displays. No difference in the discrimination index (from 5min to 96h of inter-trial) was found between NOR and VORT. Scopolamine and mecamylamine decreased the discrimination index. Conversely, the discrimination index increased when nicotine was given to mice. No further improvement in the discrimination index was observed when nicotine was injected in mice presented with highly discriminable shapes. To test the possibility that object movements increased mice's attention in the VORT, different movements were applied to the same geometrical shapes previously presented. Mice were able to distinguish among different movements (horizontal, vertical, oblique). Notably, the shapes previously found not distinguishable when stationary were better discriminated when moving. Collectively, these findings indicate that VORT, based on virtual geometric simple shapes, offers the possibility to obtain rapid information on amnesic/pro-amnestic potential of new drugs. The introduction of motion is a strong cue that makes the task more valuable to study attention.
Jansen van Rensburg, Gerhardus J; Wilke, Daniel N; Kok, Schalk
2012-01-01
Variation in masticatory induced stress, caused by shape changes in the human skull, is quantified in this article. A comparison on masticatory induced stress is presented subject to a variation in human skull shape. Non-rigid registration is employed to obtain appropriate computational domain representations. This procedure allows the isolation of shape from other variations that could affect the results. An added benefit, revealed through the use of non-rigid registration to acquire appropriate domain representation, is the possibility of direct and objective comparison and manipulation. The effect of mapping uncertainty on the direct comparison is also quantified. As shown in this study, exact difference values are not necessarily obtained, but a non-rigid map between subject shapes and numerical results gives an objective indication on the location of differences.
Fast quantum computation at arbitrarily low energy
NASA Astrophysics Data System (ADS)
Jordan, Stephen P.
2017-03-01
One version of the energy-time uncertainty principle states that the minimum time T⊥ for a quantum system to evolve from a given state to any orthogonal state is h /(4 Δ E ) , where Δ E is the energy uncertainty. A related bound called the Margolus-Levitin theorem states that T⊥≥h /(2
Arbitrarily high order nodal and characteristic methods
Azmy, Y.Y.
1994-09-01
The quest for higher computational efficiency initially led researchers in the neutron transport area to develop and implement high-order approximations for solving the linear Boltzmann equational. This drive aimed at achieving higher accuracy on coarse meshes, thereby resulting in a net savings of computational resources represented by execution time and memory. Many endeavors succeeded in reaching this goal, producing a variety of elegent, albeit complicated, formalisms, that proved extremely accurate and efficient in solving test, as well as practical applications, problems. The two main classes of high order transport methods that recieved the most attention are the Nodal and Characteristic methods. A de facto linear order standard for the spatial approximation (even though Quadratic Nodal Methods were also considered) was dictated by the algebraic complexity of the derivation of the discrete variable equations, the programming complexity of implementing and verifying them in codes, and limitations on computational resources available to run such codes. The significant advances in computational resources in terms of hardware capacity and speed, as well as architectural innovations such as vector and parallel processing, all but eliminated the third (above) obstacle towards the development and implementation of even higher order methods. The algebraic and programming complexities, on the other hand, were alleviated to some extent by the development of Arbitrarily High Order Transport methods of the Nodal and the Characteristic types, which are discussed in this report.
Solutions for transients in arbitrarily branching cables
Major, Guy; Evans, Jonathan D.; Jack, J. Julian B.
1993-01-01
Analytical solutions are derived for arbitrarily branching passive neurone models with a soma and somatic shunt, for synaptic inputs and somatic voltage commands, for both perfect and imperfect somatic voltage clamp. The solutions are infinite exponential series. Perfect clamp decouples different dendritic trees at the soma: each exponential component exists only in one tree; its time constant is independent of stimulating and recording position within the tree; its amplitude is the product of a factor constant over that entire tree and factors dependent on stimulating and recording positions. Imperfect clamp to zero is mathematically equivalent to voltage recording with a shunt. As the series resistance increases, different dendritic trees become more strongly coupled. A number of interesting response symmetries are evident. The solutions reveal parameter dependencies, including an insensitivity of the early parts of the responses to specific membrane resistivity and somatic shunt, and an approximately linear dependence of the slower time constants on series resistance, for small series resistances. The solutions are illustrated using a “cartoon” representation of a CA1 pyramidal cell and a two-cylinder + soma model. PMID:8369449
Pfister, Thorsten; Buettner, Lars; Czarske, Juergen
2009-01-01
For monitoring the position and shape of fast moving and, especially, rotating objects such as turbo machine rotors, contactless and compact sensors with a high measurement rate as well as high precision are required. We present for the first time, to the best of our knowledge, a novel laser Doppler sensor employing a single fan-shaped interference fringe system, which allows measuring for the position and shape of fast moving solid bodies with known tangential velocity. It is shown theoretically as well as experimentally that this sensor offers concurrently high position resolution and high temporal resolution in contrast to conventional measurement techniques, since its measurement uncertainty is, in principle, independent of the object velocity. Moreover, it can be built very compact, because it features low complexity. To prove its operational capability and its potential for practical applications, radial and axial shape measurements of rotating bodies are demonstrated in comparison with triangulation. An average position resolution of about 2 {mu}m could be achieved.
Baode Wang; David R. Lance; Joseph A. Francese; Zhichun Xu; Fengyong Jia; Youqing Luo; Victor C. Mastro
2003-01-01
Silhouettes of different colors, shapes and sizes made of bamboo frames covered with cloth, paired in different color sets, were placed equidistantly around the perimeter of a circle with a 7.5 m radius, in an open area.
Curvature and shape variance based landmark tagging methods for building statistical object models
NASA Astrophysics Data System (ADS)
Rueda, Sylvia; Udupa, Jayaram K.; Bai, Li
2009-02-01
Model-based segmentation approaches, such as those employing Active Shape Models (ASMs), have proved to be useful for medical image segmentation and understanding. To build the model, however, we need an annotated training set of shapes wherein corresponding landmarks are identified in every shape. Manual positioning of landmarks is a tedious, time consuming, and error prone task, and almost impossible in the 3D space. In an attempt to overcome some of these drawbacks, we have devised several automatic methods under two approaches: c-scale based and shape variance based. The c-scale based methods use the concept of local curvature to find landmarks on the mean shape of the training set. These landmarks are then propagated to all the shapes of the training set to establish correspondence in a local-to-global manner. The variance-based method is guided by the strategy of equalization of the shape variance contained in the training set for selecting landmarks. The main premise here is that this strategy itself takes care of the correspondence issue and at the same time deploys landmarks very frugally and optimally considering shape variations. The desired landmarks are positioned around each contour so as to equally distribute the total variance existing in the training set in a global-to-local manner. The methods are evaluated on 40 MRI foot data sets and compared in terms of compactness. The results show that, for the same number of landmarks, the proposed methods are more compact than manual and equally spaced methods of annotation, and the variance equalization method tops the list.
Shape-based discriminative analysis of combined bilateral hippocampi using multiple object alignment
NASA Astrophysics Data System (ADS)
Shen, Li; Makedon, Fillia; Saykin, Andrew
2004-05-01
Shape analysis of hippocampi in schizophrenia has been preformed previously using the spherical harmonic SPHARM description. In these studies, the left and right hippocampi are aligned independently and the spatial relation between them is not explored. This paper presents a new SPHARM-based technique which examines not only the individual shape information of the two hippocampi but also the spatial relation between them. The left and right hippocampi are treated as a single shape configuration. A ploy-shape alignment algorithm is developed for aligning configurations of multiple SPHARM surfaces as follows: (1) the total volume is normalized; (2) the parameter space is aligned for creating the surface correspondence; (3) landmarks are created by a uniform sampling of multiple surfaces for each configuration; (4) a quaternion-based algorithm is employed to align each landmark representation to the mean configuration through the least square rotation and translation iteratively until the mean converges. After applying the poly-shape alignment algorithm, a point distribution model is applied to aligned landmarks for feature extraction. Classification is performed using Fisher's linear discriminant with an effective feature selection scheme. Applying the above procedure to our hippocampal data (14 controls versus 25 schizophrenics, all right-handed males), we achieve the best cross-validation accuracy of 92%, supporting the idea that the whole shape configuration of the two hippocampi provides valuable information in detecting schizophrenia. The results of an ROC analysis and a visualization of discriminative patterns are also included.
Lopes, Oscar; Reyes, Miguel; Escalera, Sergio; Gonzàlez, Jordi
2014-12-01
The use of depth maps is of increasing interest after the advent of cheap multisensor devices based on structured light, such as Kinect. In this context, there is a strong need of powerful 3-D shape descriptors able to generate rich object representations. Although several 3-D descriptors have been already proposed in the literature, the research of discriminative and computationally efficient descriptors is still an open issue. In this paper, we propose a novel point cloud descriptor called spherical blurred shape model (SBSM) that successfully encodes the structure density and local variabilities of an object based on shape voxel distances and a neighborhood propagation strategy. The proposed SBSM is proven to be rotation and scale invariant, robust to noise and occlusions, highly discriminative for multiple categories of complex objects like the human hand, and computationally efficient since the SBSM complexity is linear to the number of object voxels. Experimental evaluation in public depth multiclass object data, 3-D facial expressions data, and a novel hand poses data sets show significant performance improvements in relation to state-of-the-art approaches. Moreover, the effectiveness of the proposal is also proved for object spotting in 3-D scenes and for real-time automatic hand pose recognition in human computer interaction scenarios.
Raghavan, Preeti; Santello, Marco; Gordon, Andrew M; Krakauer, John W
2010-06-01
Efficient grasping requires planned and accurate coordination of finger movements to approximate the shape of an object before contact. In healthy subjects, hand shaping is known to occur early in reach under predominantly feedforward control. In patients with hemiparesis after stroke, execution of coordinated digit motion during grasping is impaired as a result of damage to the corticospinal tract. The question addressed here is whether patients with hemiparesis are able to compensate for their execution deficit with a qualitatively different grasp strategy that still allows them to differentiate hand posture to object shape. Subjects grasped a rectangular, concave, and convex object while wearing an instrumented glove. Reach-to-grasp was divided into three phases based on wrist kinematics: reach acceleration (reach onset to peak horizontal wrist velocity), reach deceleration (peak horizontal wrist velocity to reach offset), and grasp (reach offset to lift-off). Patients showed reduced finger abduction, proximal interphalangeal joint (PIP) flexion, and metacarpophalangeal joint (MCP) extension at object grasp across all three shapes compared with controls; however, they were able to partially differentiate hand posture for the convex and concave shapes using a compensatory strategy that involved increased MCP flexion rather than the PIP flexion seen in controls. Interestingly, shape-specific hand postures did not unfold initially during reach acceleration as seen in controls, but instead evolved later during reach deceleration, which suggests increased reliance on sensory feedback. These results indicate that kinematic analysis can identify and quantify within-limb compensatory motor control strategies after stroke. From a clinical perspective, quantitative study of compensation is important to better understand the process of recovery from brain injury. From a motor control perspective, compensation can be considered a model for how joint redundancy is exploited
Santello, Marco; Gordon, Andrew M.; Krakauer, John W.
2010-01-01
Efficient grasping requires planned and accurate coordination of finger movements to approximate the shape of an object before contact. In healthy subjects, hand shaping is known to occur early in reach under predominantly feedforward control. In patients with hemiparesis after stroke, execution of coordinated digit motion during grasping is impaired as a result of damage to the corticospinal tract. The question addressed here is whether patients with hemiparesis are able to compensate for their execution deficit with a qualitatively different grasp strategy that still allows them to differentiate hand posture to object shape. Subjects grasped a rectangular, concave, and convex object while wearing an instrumented glove. Reach-to-grasp was divided into three phases based on wrist kinematics: reach acceleration (reach onset to peak horizontal wrist velocity), reach deceleration (peak horizontal wrist velocity to reach offset), and grasp (reach offset to lift-off). Patients showed reduced finger abduction, proximal interphalangeal joint (PIP) flexion, and metacarpophalangeal joint (MCP) extension at object grasp across all three shapes compared with controls; however, they were able to partially differentiate hand posture for the convex and concave shapes using a compensatory strategy that involved increased MCP flexion rather than the PIP flexion seen in controls. Interestingly, shape-specific hand postures did not unfold initially during reach acceleration as seen in controls, but instead evolved later during reach deceleration, which suggests increased reliance on sensory feedback. These results indicate that kinematic analysis can identify and quantify within-limb compensatory motor control strategies after stroke. From a clinical perspective, quantitative study of compensation is important to better understand the process of recovery from brain injury. From a motor control perspective, compensation can be considered a model for how joint redundancy is exploited
NASA Astrophysics Data System (ADS)
Jalali, Tahmineh
2014-03-01
Lens-shaped particles with different sizes for various refractive indices have been investigated under plane wave illumination by using 2D-MMP simulation. Distribution of the power in the vicinity of opposite boundary of the particle has resulted in a tightly focused photonic nanojet in specific conditions. The results show that the beam waists are smaller than the diffraction limit, and they propagate over several optical wavelengths without significant diffraction while the beam reaches a high intensity. In this paper, it is argued the manipulation of various dielectric lens shapes with respect to a highly confined power distribution in the producing nanojet has been parameterized according to the beam waist and divergence with regards to particular refractive index (glass, plastic and patinal), and appropriate structure shapes. Optimized dimensions of the nanojets for different physical properties are calculated.
Shape and color conjunction stimuli are represented as bound objects in visual working memory.
Luria, Roy; Vogel, Edward K
2011-05-01
The integrated object view of visual working memory (WM) argues that objects (rather than features) are the building block of visual WM, so that adding an extra feature to an object does not result in any extra cost to WM capacity. Alternative views have shown that complex objects consume additional WM storage capacity so that it may not be represented as bound objects. Additionally, it was argued that two features from the same dimension (i.e., color-color) do not form an integrated object in visual WM. This led some to argue for a "weak" object view of visual WM. We used the contralateral delay activity (the CDA) as an electrophysiological marker of WM capacity, to test those alternative hypotheses to the integrated object account. In two experiments we presented complex stimuli and color-color conjunction stimuli, and compared performance in displays that had one object but varying degrees of feature complexity. The results supported the integrated object account by showing that the CDA amplitude corresponded to the number of objects regardless of the number of features within each object, even for complex objects or color-color conjunction stimuli.
Generalized dispersion analysis of arbitrarily cut monoclinic crystals.
Höfer, Sonja; Ivanovski, Vladimir; Uecker, Reinhard; Kwasniewski, Albert; Popp, Jürgen; Mayerhöfer, Thomas G
2017-10-05
Dispersion analysis is applicable to arbitrarily cut monoclinic crystals of unknown orientation in order to find the symmetry axis. By this it is possible to differentiate between the transition moments oriented parallel and normal to the b-axis and to determine the dielectric tensor functions of those two principal directions. Dispersion analysis of arbitrarily cut monoclinic crystals is based on an extension of the evaluation scheme developed for arbitrarily cut orthorhombic crystals. We present dispersion analysis of monoclinic crystals exemplarily on spodumene (LiAl(SiO3)2) and yttrium orthosilicate (Y2SiO5). Copyright © 2017 Elsevier B.V. All rights reserved.
Generalized dispersion analysis of arbitrarily cut monoclinic crystals
NASA Astrophysics Data System (ADS)
Höfer, Sonja; Ivanovski, Vladimir; Uecker, Reinhard; Kwasniewski, Albert; Popp, Jürgen; Mayerhöfer, Thomas G.
2017-10-01
Dispersion analysis is applicable to arbitrarily cut monoclinic crystals of unknown orientation in order to find the symmetry axis. By this it is possible to differentiate between the transition moments oriented parallel and normal to the b-axis and to determine the dielectric tensor functions of those two principal directions. Dispersion analysis of arbitrarily cut monoclinic crystals is based on an extension of the evaluation scheme developed for arbitrarily cut orthorhombic crystals. We present dispersion analysis of monoclinic crystals exemplarily on spodumene (LiAl(SiO3)2) and yttrium orthosilicate (Y2SiO5).
Method for determining depth and shape of a sub-surface conductive object
NASA Astrophysics Data System (ADS)
Lee, D. O.; Montoya, P. C.; Wayland, J. R., Jr.
1984-06-01
The depth to and size of an underground object may be determined by sweeping a controlled source audio magnetotelluric (CSAMT) signal and locating a peak response when the receiver spans the edge of the object. The depth of the object is one quarter wavelength in the subsurface media of the frequency of the peak.
CSAMT method for determining depth and shape of a sub-surface conductive object
Lee, David O.; Montoya, Paul C.; Wayland, Jr., J. Robert
1986-01-01
The depth to and size of an underground object may be determined by sweeping a CSAMT signal and locating a peak response when the receiver spans the edge of the object. The depth of the object is one quarter wavelength in the subsurface media of the frequency of the peak.
Method for determining depth and shape of a sub-surface conductive object
Lee, D.O.; Montoya, P.C.; Wayland, Jr.
1984-06-27
The depth to and size of an underground object may be determined by sweeping a controlled source audio magnetotelluric (CSAMT) signal and locating a peak response when the receiver spans the edge of the object. The depth of the object is one quarter wavelength in the subsurface media of the frequency of the peak. 3 figures.
Function Follows Form: Activation of Shape and Function Features during Object Identification
ERIC Educational Resources Information Center
Yee, Eiling; Huffstetler, Stacy; Thompson-Schill, Sharon L.
2011-01-01
Most theories of semantic memory characterize knowledge of a given object as comprising a set of semantic features. But how does conceptual activation of these features proceed during object identification? We present the results of a pair of experiments that demonstrate that object recognition is a dynamically unfolding process in which function…
Function Follows Form: Activation of Shape and Function Features during Object Identification
ERIC Educational Resources Information Center
Yee, Eiling; Huffstetler, Stacy; Thompson-Schill, Sharon L.
2011-01-01
Most theories of semantic memory characterize knowledge of a given object as comprising a set of semantic features. But how does conceptual activation of these features proceed during object identification? We present the results of a pair of experiments that demonstrate that object recognition is a dynamically unfolding process in which function…
Lawson, Rebecca
2014-02-01
The limits of generalization of our 3-D shape recognition system to identifying objects by touch was investigated by testing exploration at unusual locations and using untrained effectors. In Experiments 1 and 2, people found identification by hand of real objects, plastic 3-D models of objects, and raised line drawings placed in front of themselves no easier than when exploration was behind their back. Experiment 3 compared one-handed, two-handed, one-footed, and two-footed haptic object recognition of familiar objects. Recognition by foot was slower (7 vs. 13 s) and much less accurate (9 % vs. 47 % errors) than recognition by either one or both hands. Nevertheless, item difficulty was similar across hand and foot exploration, and there was a strong correlation between an individual's hand and foot performance. Furthermore, foot recognition was better with the largest 20 of the 80 items (32 % errors), suggesting that physical limitations hampered exploration by foot. Thus, object recognition by hand generalized efficiently across the spatial location of stimuli, while object recognition by foot seemed surprisingly good given that no prior training was provided. Active touch (haptics) thus efficiently extracts 3-D shape information and accesses stored representations of familiar objects from novel modes of input.
Attitude Estimation for Unresolved Agile Space Objects with Shape Model Uncertainty
2012-09-01
While lightcurves have been used for at least 25 years to characterize spin states and shapes of asteroids (for an introduction see [3, 4]), estimating...safety, implementing international treaties and agreements, protecting space capabilities, and preserving national interests [2]. Characterizing the...be inferred by carefully examining their lightcurves . Lightcurves are temporally-resolved sequences of photometric intensity measurements over one or
ERIC Educational Resources Information Center
Watson, Derrick G.; Kunar, Melina A.
2010-01-01
Visual search efficiency improves by presenting (previewing) one set of distractors before the target and remaining distractor items (D. G. Watson & G. W. Humphreys, 1997). Previous work has shown that this preview benefit is abolished if the old items change their shape when the new items are added (e.g., D. G. Watson & G. W. Humphreys,…
ERIC Educational Resources Information Center
Watson, Derrick G.; Kunar, Melina A.
2010-01-01
Visual search efficiency improves by presenting (previewing) one set of distractors before the target and remaining distractor items (D. G. Watson & G. W. Humphreys, 1997). Previous work has shown that this preview benefit is abolished if the old items change their shape when the new items are added (e.g., D. G. Watson & G. W. Humphreys,…
It Is Not Just about Location: Infants Perseverate to Container Shape during Object Search
ERIC Educational Resources Information Center
Noland, Julia S.
2007-01-01
In searching for a toy hidden at a new location, infants will err by searching at the previously correct location. This study investigated the possibility that 8.5-month-old infants would perseverate on the basis of other visual features by which covers could be individuated. Infants saw a toy hidden under 1 of 2 distinctly shaped covers.…
It Is Not Just about Location: Infants Perseverate to Container Shape during Object Search
ERIC Educational Resources Information Center
Noland, Julia S.
2007-01-01
In searching for a toy hidden at a new location, infants will err by searching at the previously correct location. This study investigated the possibility that 8.5-month-old infants would perseverate on the basis of other visual features by which covers could be individuated. Infants saw a toy hidden under 1 of 2 distinctly shaped covers.…
NASA Astrophysics Data System (ADS)
Chen, Peilong
2013-12-01
We prove that, for an object with a finitefold rotational symmetry (except for a twofold one) around an axis and mirror symmetries (such as a square rod or pentagonal slab, etc.), dynamics of the symmetry axis in low Reynolds number shear flow exactly follows the same form as that of a uniaxial object (e.g., a circular rod or symmetric ellipsoid) as the so-called Jeffery orbits. We use the formulation in which the dynamics of the rigid body follows first-order ordinary differential equations in time [Phys. Rev. EPRESCM1539-375510.1103/PhysRevE.84.056309 84, 056309 (2011)]. Interaction between the object and the shear flow enters through a set of scalar coefficients, and the flow field does not need to be solved dynamically. Results of numerical simulations for general-shaped objects also are discussed. In the second part, Brownian dynamics of a uniaxial object is studied numerically. With D as the rotational diffusion constant, α as a parameter characterizing the aspect ratio, and γ as the shear rate, the object starts to align with the flow when the value of D/(γα) decreases near 1. At large α (the long object limit), the results suggest much lower flow alignment when D/(γα)>1.
Peters, Megan A K; Balzer, Jonathan; Shams, Ladan
2015-01-01
If one nondescript object's volume is twice that of another, is it necessarily twice as heavy? As larger objects are typically heavier than smaller ones, one might assume humans use such heuristics in preparing to lift novel objects if other informative cues (e.g., material, previous lifts) are unavailable. However, it is also known that humans are sensitive to statistical properties of our environments, and that such sensitivity can bias perception. Here we asked whether statistical regularities in properties of liftable, everyday objects would bias human observers' predictions about objects' weight relationships. We developed state-of-the-art computer vision techniques to precisely measure the volume of everyday objects, and also measured their weight. We discovered that for liftable man-made objects, "twice as large" doesn't mean "twice as heavy": Smaller objects are typically denser, following a power function of volume. Interestingly, this "smaller is denser" relationship does not hold for natural or unliftable objects, suggesting some ideal density range for objects designed to be lifted. We then asked human observers to predict weight relationships between novel objects without lifting them; crucially, these weight predictions quantitatively match typical weight relationships shown by similarly-sized objects in everyday environments. These results indicate that the human brain represents the statistics of everyday objects and that this representation can be quantitatively abstracted and applied to novel objects. Finally, that the brain possesses and can use precise knowledge of the nonlinear association between size and weight carries important implications for implementation of forward models of motor control in artificial systems.
Azzopardi, George; Petkov, Nicolai
2014-01-01
The remarkable abilities of the primate visual system have inspired the construction of computational models of some visual neurons. We propose a trainable hierarchical object recognition model, which we call S-COSFIRE (S stands for Shape and COSFIRE stands for Combination Of Shifted FIlter REsponses) and use it to localize and recognize objects of interests embedded in complex scenes. It is inspired by the visual processing in the ventral stream (V1/V2 → V4 → TEO). Recognition and localization of objects embedded in complex scenes is important for many computer vision applications. Most existing methods require prior segmentation of the objects from the background which on its turn requires recognition. An S-COSFIRE filter is automatically configured to be selective for an arrangement of contour-based features that belong to a prototype shape specified by an example. The configuration comprises selecting relevant vertex detectors and determining certain blur and shift parameters. The response is computed as the weighted geometric mean of the blurred and shifted responses of the selected vertex detectors. S-COSFIRE filters share similar properties with some neurons in inferotemporal cortex, which provided inspiration for this work. We demonstrate the effectiveness of S-COSFIRE filters in two applications: letter and keyword spotting in handwritten manuscripts and object spotting in complex scenes for the computer vision system of a domestic robot. S-COSFIRE filters are effective to recognize and localize (deformable) objects in images of complex scenes without requiring prior segmentation. They are versatile trainable shape detectors, conceptually simple and easy to implement. The presented hierarchical shape representation contributes to a better understanding of the brain and to more robust computer vision algorithms. PMID:25126068
Eguchi, Akihiro; Mender, Bedeho M. W.; Evans, Benjamin D.; Humphreys, Glyn W.; Stringer, Simon M.
2015-01-01
Neurons in successive stages of the primate ventral visual pathway encode the spatial structure of visual objects. In this paper, we investigate through computer simulation how these cell firing properties may develop through unsupervised visually-guided learning. Individual neurons in the model are shown to exploit statistical regularity and temporal continuity of the visual inputs during training to learn firing properties that are similar to neurons in V4 and TEO. Neurons in V4 encode the conformation of boundary contour elements at a particular position within an object regardless of the location of the object on the retina, while neurons in TEO integrate information from multiple boundary contour elements. This representation goes beyond mere object recognition, in which neurons simply respond to the presence of a whole object, but provides an essential foundation from which the brain is subsequently able to recognize the whole object. PMID:26300766
Hawking Temperature of an Arbitrarily Accelerating Black Hole
NASA Astrophysics Data System (ADS)
Pan, Wei-Zhen; Liu, Wei
2014-09-01
Hawking temperature of an arbitrarily accelerating black hole with electric and magnetic charges are obtained based on the Klein-Gordon equation with a correct-dimension new tortoise coordinate transformation.
Peters, Megan A. K.; Balzer, Jonathan; Shams, Ladan
2015-01-01
If one nondescript object’s volume is twice that of another, is it necessarily twice as heavy? As larger objects are typically heavier than smaller ones, one might assume humans use such heuristics in preparing to lift novel objects if other informative cues (e.g., material, previous lifts) are unavailable. However, it is also known that humans are sensitive to statistical properties of our environments, and that such sensitivity can bias perception. Here we asked whether statistical regularities in properties of liftable, everyday objects would bias human observers’ predictions about objects’ weight relationships. We developed state-of-the-art computer vision techniques to precisely measure the volume of everyday objects, and also measured their weight. We discovered that for liftable man-made objects, “twice as large” doesn’t mean “twice as heavy”: Smaller objects are typically denser, following a power function of volume. Interestingly, this “smaller is denser” relationship does not hold for natural or unliftable objects, suggesting some ideal density range for objects designed to be lifted. We then asked human observers to predict weight relationships between novel objects without lifting them; crucially, these weight predictions quantitatively match typical weight relationships shown by similarly-sized objects in everyday environments. These results indicate that the human brain represents the statistics of everyday objects and that this representation can be quantitatively abstracted and applied to novel objects. Finally, that the brain possesses and can use precise knowledge of the nonlinear association between size and weight carries important implications for implementation of forward models of motor control in artificial systems. PMID:25768977
Echo-acoustic flow shapes object representation in spatially complex acoustic scenes.
Greiter, Wolfgang; Firzlaff, Uwe
2017-03-08
Echolocating bats use echoes of their sonar emissions to determine the position and distance of objects or prey. Target distance is represented as a map of echo delay in the auditory cortex (AC) of bats. During a bat's flight through a natural complex environment, echo streams are reflected from multiple objects along its flight path. Separating such complex streams of echoes or other sounds is a challenge for the auditory system of bats as well as other animals. We investigated the representation of multiple echo streams in the AC of anaesthetized bats (Phyllostomus discolor) and tested the hypothesis, if neurons can lock on echoes from specific objects in a complex echo-acoustic pattern while the representation of surrounding objects is suppressed. We combined naturalistic pulse/echo sequences simulating a bat's flight through a virtual acoustic space with extracellular recordings. Neurons could selectively lock on echoes from one object in complex echo streams originating from two different objects along a virtual flight path. The objects were processed sequentially in the order in which they were approached. Object selection depended on sequential changes of echo delay and amplitude but not on absolute values. Furthermore, the detailed representation of the object echo delays in the cortical target range map was not fixed but could be dynamically adapted depending on the temporal pattern of sonar emission during target approach within a simulated flight sequence.
Laser Doppler position sensor for position and shape measurements of fast rotating objects
NASA Astrophysics Data System (ADS)
Czarske, Jürgen; Pfister, Thorsten; Büttner, Lars
2006-08-01
We report about a novel optical method based on laser Doppler velocimetry for position and shape measurements of moved solid state surfaces with approximately one micrometer position resolution. 3D shape measurements of a rotating cylinder inside a turning machine as well as tip clearance measurements at a transonic centrifugal compressor performed during operation at 50,000 rpm and 586 m/s blade tip velocity are presented. All results are in good agreement with conventional reference probes. The measurement accuracy of the laser Doppler position sensor is investigated in dependence of the speckle pattern. Furthermore, it is shown that this sensor offers high temporal resolution and high position resolution simultaneously and that shading can be reduced compared to triangulation. Consequently, the presented laser Doppler position sensor opens up new perspectives in the field of real-time manufacturing metrology and process control, for example controlling the turning and the grinding process or for future developments of turbo machines.
Tsuruhara, Aki; Sawada, Tadamasa; Kanazawa, So; Yamaguchi, Masami K; Corrow, Sherryse; Yonas, Albert
2010-10-01
A "transfer-across-depth-cues" method was used to explore the development of the ability to generate and use spatial representations of an object as specified by static pictorial depth cues. Infants were habituated to an object with depth specified by one cue and then presented with the same shape with depth specified by a different cue. Only if an abstract representation of that object had been formed could transfer across cues occur. Shading and line junctions uniquely determined the 3D shapes in these displays so that they appeared to be either a slice of cake with a flat top or a rocket. Without these cues, both line drawings were identical. Infants aged 6 to 7 months showed significant evidence of transfer, while infants aged 4 to 5 months did not. A control experiment demonstrated that the younger infants could discriminate between the objects when a single depth cue specified the shapes. These results are similar to our previous findings, which indicated that 6- to 7-month-old infants show transfer across shading and surface-contour cues, specifying convex and concave surfaces (A. Tsuruhara, T. Sawada, S. Kanazawa, M. K. Yamaguchi, & A. Yonas, 2009). This work supports the hypothesis that the ability to form 3D spatial representations from pictorial depth cues develops at about 6 months of age.
Kaldy, Zsuzsa; Blaser, Erik
2009-01-01
What kind of featural information do infants rely on when they are trying to recognize a previously seen object? The question of whether infants use certain features (e.g. shape or color) more than others (e. g. luminance), can only be studied legitimately if visual salience is controlled, since the magnitude of feature values – how noticeable and interesting they are – will affect results. We employed a novel methodology, ‘Interdimensional Salience Mapping’, that allowed us to quantify and calibrate salience changes along shape, luminance and color feature dimensions. We then compared 9-month-old infants' identification of objects, employing feature changes that were equally salient. These results show that infants more readily identify objects on the basis of color and shape than luminance. Additionally, we show that relative salience changes rapidly in infancy – in particular, we found significantly higher salience thresholds for color in younger (6.5-month-old) infants – but that individual differences within an age group are remarkably modest. PMID:20161281
NASA Astrophysics Data System (ADS)
Wang, Fengpeng; Wang, Dayong; Rong, Lu; Wang, Yunxin; Zhao, Jie
2017-05-01
In this paper, a hybrid method of phase retrieval and off-axis digital holography is proposed for imaging of the complex shape objects. Off-axis digital hologram and in-line hologram are recorded. The approximate phase distributions in the recording plane and object plane are obtained by constrained optimization approach from the off-axis hologram, and they are used as the initial value and the constraints in the phase retrieval for eliminating the twin image of in-line holography. Numerical simulations and optical experiments were carried out to validate the proposed method.
NASA Astrophysics Data System (ADS)
Karlsen, Brian; Sorensen, Helge B. D.; Larsen, Jan; Jakobsen, Kaj B.
2003-09-01
This paper addresses the detection of mine-like objects in stepped-frequency ground penetrating radar (SF-GPR) data as a function of object size, object content, and burial depth. The detection approach is based on a Selective Independent Component Analysis (SICA). SICA provides an automatic ranking of components, which enables the suppression of clutter, hence extraction of components carrying mine information. The goal of the investigation is to evaluate various time and frequency domain ICA approaches based on SICA. The performance comparison is based on a series of mine-like objects ranging from small-scale anti-personal (AP) mines to large-scale anti-tank (AT) mines. Large-scale SF-GPR measurements on this series of mine-like objects buried in soil were performed. The SF-GPR data was acquired using a wideband monostatic bow-tie antenna operating in the frequency range 750 MHz - 3.0 GHz. The detection and clutter reduction approaches based on SICA are successfully evaluated on this SF-GPR dataset.
An objective view of biological diversity: how history and epistemology shaped current treatment.
Eduardo, Anderson A; Carmo, Ricardo
2017-05-11
The concept of biological diversity has inspired important discussions throughout the history of ecology. Although its meaning and usefulness have been questioned, it is currently one of the key artifacts of ecology. One way to try to understand why such a concept has undergone so many discussions is to examine its emergence and history from the epistemology perspective. In the present work, we investigated how the emergence of mechanical objectivity (as an epistemic virtue) and trained judgment affected how ecologists address the concept of biological diversity. Thus, we employed the theoretical framework of objectivity (provided by Daston and Galison in Objectivity. Zone Books, New York, 2007) to analyze different periods of scientific literature in ecology ("initial period": end of the nineteenth century and beginning of the twentieth century; "intermediate period": mid-twentieth century; "contemporary period": from the second half of the 1980s). Our results showed that the emergence of mechanical objectivity and trained judgment affected biological diversity research. In particular, the ideal of objectivity behind the way in which the concept of biological diversity is addressed in different fields of contemporary ecology could not be the same.
Vision Algorithms to Determine Shape and Distance for Manipulation of Unmodeled Objects
NASA Technical Reports Server (NTRS)
Montes, Leticia; Bowers, David; Lumia, Ron
1998-01-01
This paper discusses the development of a robotic system for general use in an unstructured environment. This is illustrated through pick and place of randomly positioned, un-modeled objects. There are many applications for this project, including rock collection for the Mars Surveyor Program. This system is demonstrated with a Puma560 robot, Barrett hand, Cognex vision system, and Cimetrix simulation and control, all running on a PC. The demonstration consists of two processes: vision system and robotics. The vision system determines the size and location of the unknown objects. The robotics part consists of moving the robot to the object, configuring the hand based on the information from the vision system, then performing the pick/place operation. This work enhances and is a part of the Low Cost Virtual Collaborative Environment which provides remote simulation and control of equipment.
Vision Algorithms to Determine Shape and Distance for Manipulation of Unmodeled Objects
NASA Technical Reports Server (NTRS)
Montes, Leticia; Bowers, David; Lumia, Ron
1998-01-01
This paper discusses the development of a robotic system for general use in an unstructured environment. This is illustrated through pick and place of randomly positioned, un-modeled objects. There are many applications for this project, including rock collection for the Mars Surveyor Program. This system is demonstrated with a Puma560 robot, Barrett hand, Cognex vision system, and Cimetrix simulation and control, all running on a PC. The demonstration consists of two processes: vision system and robotics. The vision system determines the size and location of the unknown objects. The robotics part consists of moving the robot to the object, configuring the hand based on the information from the vision system, then performing the pick/place operation. This work enhances and is a part of the Low Cost Virtual Collaborative Environment which provides remote simulation and control of equipment.
Geometric Methods for ATR: Shape Spaces, Metrics, Object/Image Relations, and Shapelets
2007-09-30
and only if Kr - 4 C L r - 3 C H r - l C r This fact and the incidence relations given in Theorem I, §5, Chapter VII of Hodge and Pedoe [4] give us our...Springer-Verlag, 1992. 4. W.V.D. Hodge and D. Pedoe , Methods of Algebraic Geometry, nos. 1, 2, and 3, in Mathematical Library Series, Cambridge...and Pedoe [5] give us our object-image relations. Theorem 2.4. Let Pi = (xi, yi, zi), 1 < i < r be an object configuration with corresponding matrix M
NASA Astrophysics Data System (ADS)
Delmas, Anthony; Maoult, Yannick Le; Buchlin, Jean-Marie; Sentenac, Thierry; Orteu, Jean-José
2013-04-01
The goal of this study is to examine the perturbation induced by the convective effect (or mirage effect) on shape measurement and to give an estimation of the error induced. This work explores the mirage effect in different spectral bands and single wavelengths. A numerical approach is adopted and an original setup has been developed in order to investigate easily all the spectral bands of interest with the help of a CCD camera (Si, 0.35-1.1 μm), a near infrared camera (VisGaAs, 0.8-1.7 μm) or infrared cameras (8-12 μm). Displacements due to the perturbation for each spectral band are measured and finally some hints about how to correct them are given.
Minor planets and related objects. XIX - Shape and pole orientation of /39/ Laetitia
NASA Technical Reports Server (NTRS)
Sather, R. E.
1976-01-01
Results are reported for analyses of UBV photoelectric photometric data and light curves of the asteroid Laetitia. The pole orientation is determined using a technique for reducing the scatter in the magnitude-phase relation. No significant variations in color are found over the surface, and the light curves are found to indicate topographic elements (peaks, scarps, or depressions) approximately 10 km in radius. It is shown that the light-curve amplitudes as well as the wide scatter in observed magnitude and phase relation can be explained by a triaxial ellipsoidal figure with a dimensional ratio of about 15:9:5. It is concluded that the size, shape, and composition of this asteroid are highly suggestive of a major collisional fragment from a substantially more massive differentiated parent body.
Linkenauger, Sally A.; Leyrer, Markus; Bülthoff, Heinrich H.; Mohler, Betty J.
2013-01-01
The notion of body-based scaling suggests that our body and its action capabilities are used to scale the spatial layout of the environment. Here we present four studies supporting this perspective by showing that the hand acts as a metric which individuals use to scale the apparent sizes of objects in the environment. However to test this, one must be able to manipulate the size and/or dimensions of the perceiver’s hand which is difficult in the real world due to impliability of hand dimensions. To overcome this limitation, we used virtual reality to manipulate dimensions of participants’ fully-tracked, virtual hands to investigate its influence on the perceived size and shape of virtual objects. In a series of experiments, using several measures, we show that individuals’ estimations of the sizes of virtual objects differ depending on the size of their virtual hand in the direction consistent with the body-based scaling hypothesis. Additionally, we found that these effects were specific to participants’ virtual hands rather than another avatar’s hands or a salient familiar-sized object. While these studies provide support for a body-based approach to the scaling of the spatial layout, they also demonstrate the influence of virtual bodies on perception of virtual environments. PMID:23874681
Linkenauger, Sally A; Leyrer, Markus; Bülthoff, Heinrich H; Mohler, Betty J
2013-01-01
The notion of body-based scaling suggests that our body and its action capabilities are used to scale the spatial layout of the environment. Here we present four studies supporting this perspective by showing that the hand acts as a metric which individuals use to scale the apparent sizes of objects in the environment. However to test this, one must be able to manipulate the size and/or dimensions of the perceiver's hand which is difficult in the real world due to impliability of hand dimensions. To overcome this limitation, we used virtual reality to manipulate dimensions of participants' fully-tracked, virtual hands to investigate its influence on the perceived size and shape of virtual objects. In a series of experiments, using several measures, we show that individuals' estimations of the sizes of virtual objects differ depending on the size of their virtual hand in the direction consistent with the body-based scaling hypothesis. Additionally, we found that these effects were specific to participants' virtual hands rather than another avatar's hands or a salient familiar-sized object. While these studies provide support for a body-based approach to the scaling of the spatial layout, they also demonstrate the influence of virtual bodies on perception of virtual environments.
Non-destructive 3D shape measurement of transparent and black objects with thermal fringes
NASA Astrophysics Data System (ADS)
Brahm, Anika; Rößler, Conrad; Dietrich, Patrick; Heist, Stefan; Kühmstedt, Peter; Notni, Gunther
2016-05-01
Fringe projection is a well-established optical method for the non-destructive contactless three-dimensional (3D) measurement of object surfaces. Typically, fringe sequences in the visible wavelength range (VIS) are projected onto the surfaces of objects to be measured and are observed by two cameras in a stereo vision setup. The reconstruction is done by finding corresponding pixels in both cameras followed by triangulation. Problems can occur if the properties of some materials disturb the measurements. If the objects are transparent, translucent, reflective, or strongly absorbing in the VIS range, the projected patterns cannot be recorded properly. To overcome these challenges, we present a new alternative approach in the infrared (IR) region of the electromagnetic spectrum. For this purpose, two long-wavelength infrared (LWIR) cameras (7.5 - 13 μm) are used to detect the emitted heat radiation from surfaces which is induced by a pattern projection unit driven by a CO2 laser (10.6 μm). Thus, materials like glass or black objects, e.g. carbon fiber materials, can be measured non-destructively without the need of any additional paintings. We will demonstrate the basic principles of this heat pattern approach and show two types of 3D systems based on a freeform mirror and a GOBO wheel (GOes Before Optics) projector unit.
NASA Astrophysics Data System (ADS)
Czarske, J. W.; Kuschmierz, R.; Günther, P.
2013-06-01
Precise measurements of distance, eccentricity and 3D-shape of fast moving objects such as turning parts of lathes, gear shafts, magnetic bearings, camshafts, crankshafts and rotors of vacuum pumps are on the one hand important tasks. On the other hand they are big challenges, since contactless precise measurement techniques are required. Optical techniques are well suitable for distance measurements of non-moving surfaces. However, measurements of laterally fast moving surfaces are still challenging. For such tasks the laser Doppler distance sensor technique was invented by the TU Dresden some years ago. This technique has been realized by two mutually tilted interference fringe systems, where the distance is coded in the phase difference between the generated interference signals. However, due to the speckle effect different random envelopes and phase jumps of the interference signals occur. They disturb the phase difference estimation between the interference signals. In this paper, we will report on a scientific breakthrough on the measurement uncertainty budget which has been achieved recently. Via matching of the illumination and receiving optics the measurement uncertainty of the displacement and distance can be reduced by about one magnitude. For displacement measurements of a recurring rough surface a standard deviation of 110 nm were attained at lateral velocities of 5 m / s. Due to the additionally measured lateral velocity and the rotational speed, the two-dimensional shape of rotating objects is calculated. The three-dimensional shape can be conducted by employment of a line camera. Since the measurement uncertainty of the displacement, vibration, distance, eccentricity, and shape is nearly independent of the lateral surface velocity, this technique is predestined for fast-rotating objects. Especially it can be advantageously used for the quality control of workpieces inside of a lathe towards the reduction of process tolerances, installation times and
1998 SM165: A large Kuiper belt object with an irregular shape
Romanishin, W.; Tegler, S. C.; Rettig, T. W.; Consolmagno, G.; Botthof, B.
2001-01-01
The recent discovery of an ancient reservoir of icy bodies at and beyond the orbit of Neptune—the Kuiper belt—has opened a new frontier in astronomy. Measurements of the physical and chemical nature of Kuiper belt objects (KBOs) can constrain our ideas of the processes of planet formation and evolution. Our 1.8-m Vatican Advanced Technology Telescope and charge-coupled device camera observations of the KBO 1998 SM165 indicate its brightness periodically varies by 0.56 magnitudes over a 4-h interval. If we assume a uniform albedo of 0.04, which is typical of values found in the literature for a handful of KBOs, and an “equator-on” aspect, we find 1998 SM165 has axes of length 600 × 360 km. If our assumptions are correct, such dimensions put 1998 SM165 among the largest elongated objects known in our solar system. Perhaps long ago, two nearly spherical KBOs of comparable size coalesced to form a compound object, or perhaps 1998 SM165 is the residual core of a catastrophic fragmentation of a larger precursor. PMID:11572937
1998 SM165: a large Kuiper belt object with an irregular shape.
Romanishin, W; Tegler, S C; Rettig, T W; Consolmagno, G; Botthof, B
2001-10-09
The recent discovery of an ancient reservoir of icy bodies at and beyond the orbit of Neptune-the Kuiper belt-has opened a new frontier in astronomy. Measurements of the physical and chemical nature of Kuiper belt objects (KBOs) can constrain our ideas of the processes of planet formation and evolution. Our 1.8-m Vatican Advanced Technology Telescope and charge-coupled device camera observations of the KBO 1998 SM(165) indicate its brightness periodically varies by 0.56 magnitudes over a 4-h interval. If we assume a uniform albedo of 0.04, which is typical of values found in the literature for a handful of KBOs, and an "equator-on" aspect, we find 1998 SM(165) has axes of length 600 x 360 km. If our assumptions are correct, such dimensions put 1998 SM(165) among the largest elongated objects known in our solar system. Perhaps long ago, two nearly spherical KBOs of comparable size coalesced to form a compound object, or perhaps 1998 SM(165) is the residual core of a catastrophic fragmentation of a larger precursor.
Electrophoresis of composite objects: effect of shape, topology and polymer stiffness
NASA Astrophysics Data System (ADS)
Chubynsky, Mykyta V.; Slater, Gary W.
2014-03-01
In several methods of electrophoretic separation, DNA fragments are conjugated or form complexes with objects of various kinds (linear and branched polymers, globular proteins, gold nanoparticles, micelles) having a different electrophoretic mobility. With these applications in mind, we study the free-solution electrophoresis of various composite objects (diblock copolymers with blocks of different stiffnesses, a polymer attached to a sphere, a branched polymer). We use the approach of Long et al. [J. Chem. Phys. 108 (1998) 1234], calculating hydrodynamic interactions within the Kirkwood-Riseman approximation, and we extend the approach to the case where some parts are solid objects, rather than polymers. We find, in particular, that for diblock copolymers the results depend strongly on the relative stiffness of the blocks. If the mobility of the complex is represented as a weighted average of the mobilities of the individual parts, then when a polymer is attached to a sphere or forms a branch the weights are lower for the parts near the attachment point.
Circularity measuring system: A shape gauge designed especially for use on large objects
NASA Technical Reports Server (NTRS)
Rohrkaste, G. R.
1990-01-01
The Circularity Measuring System (CMS) was developed to make an in-situ determination of shape similarity for selected fit large cylinders (RSRM segments). It does this to a repeatable accuracy of 0.10 mm (0.004 inch). This is less that the goal of 0.07 mm (0.003 inch), but was determined adequate because of the addition of an assembly aid that increased the entry chamfer of the clevis side of the joint. The usefulness of the CMS is demonstrated by the application to measurements other than its specified design purpose, such as submarine hull circularity, SRM mid-case circularity, as well as circularity of interfacing SRM tooling, specifically the rounding devices and horizontal disassembly devices. Commercialization of the tool is being pursued, since it is an enhancement of metrology technology for circularity determination. The most accurate in-situ technology it replaces is determined from a template. The CMS is an improvement in accuracy and operation.
Circularity measuring system: A shape gauge designed especially for use on large objects
NASA Astrophysics Data System (ADS)
Rohrkaste, G. R.
1990-04-01
The Circularity Measuring System (CMS) was developed to make an in-situ determination of shape similarity for selected fit large cylinders (RSRM segments). It does this to a repeatable accuracy of 0.10 mm (0.004 inch). This is less that the goal of 0.07 mm (0.003 inch), but was determined adequate because of the addition of an assembly aid that increased the entry chamfer of the clevis side of the joint. The usefulness of the CMS is demonstrated by the application to measurements other than its specified design purpose, such as submarine hull circularity, SRM mid-case circularity, as well as circularity of interfacing SRM tooling, specifically the rounding devices and horizontal disassembly devices. Commercialization of the tool is being pursued, since it is an enhancement of metrology technology for circularity determination. The most accurate in-situ technology it replaces is determined from a template. The CMS is an improvement in accuracy and operation.
NASA Astrophysics Data System (ADS)
Hau, L. C.; Fung, E. H. K.
2004-08-01
This work presents the use of a multi-objective genetic algorithm (MOGA) to solve an integrated optimization problem for the shape control of flexible beams with an active constrained layer damping (ACLD) treatment. The design objectives are to minimize the total weight of the system, the input voltages and the steady-state error between the achieved and desired shapes. Design variables include the thickness of the constraining and viscoelastic layers, the arrangement of the ACLD patches, as well as the control gains. In order to set up an evaluator for the MOGA, the finite element method (FEM), in conjunction with the Golla-Hughes-McTavish (GHM) method, is employed to model a clamped-free beam with ACLD patches to predict the dynamic behaviour of the system. As a result of the optimization, reasonable Pareto solutions are successfully obtained. It is shown that ACLD treatment is suitable for shape control of flexible structures and that the MOGA is applicable to the present integrated optimization problem.
NASA Astrophysics Data System (ADS)
Clifton, Yeaton H.
We simulated light scattering by objects similar to biological cells using the FDTD method. The characteristics of the cell-like objects were based on electron micrographs of cells grown in vitro. Three homogeneous cell-like objects were created from micrographs depicting normal prostate cells, and three from micrographs depicting malignant prostate cells. These six models used as the basis of our light scattering simulations led to the following conclusions: (1) The populations of normal and abnormal cell-like objects could be distinguished in terms of forward light scattering in a flow cytometry experiment; (2) The phase functions of light scattered by irregular objects averaged over several angles of incidence and several angles of observations are much smoother than the phase function of a perfect sphere; (3) There is a significant decrease in the ratio of scattering cross section of the non-spherical object to the scattering cross-section of the perfect sphere with equal volume, as the ratio of largest axis to smallest axis of the non-spherical object decreases; (4) For certain cell-like objects the phase functions of the scattered light obtained using the Henyey-Greenstein approximation or Mie theory are very different from those generated by FDTD calculations. Further calculations compared a homogeneous cell-like object, to a cell-like object of identical shape with heterogeneities added. The following are the results from the comparison of light scattering by a homogeneous cell-like object to heterogeneous cell-like object: (1) There are indications that there is a smoothing effect on the phase function data (for light scattered by the heterogeneous cell-like object) created by organelles both in data averaged over a range of orientations and in data collected at single orientations. This smoothing effect (unlike the one discussed for homogeneous cell-like objects) is observable from a single azimuth angle of observation and a single orientation of the cell
Shaping of the cat paw for food taking and object manipulation: an X-ray analysis.
Boczek-Funcke, A; Kuhtz-Buschbeck, J P; Raethjen, J; Paschmeyer, B; Illert, M
1998-12-01
The kinematics of the cat distal forelimb during food-taking were analysed to obtain information on the movement processes within the paw before and during object taking in a species without monosynaptic corticomotoneuronal projections. The behaviour was investigated with two tests: either the table test (TT, food offered on a table located at ground level in a reaching distance of 22 and 28 cm) or the horizontal test (HT, food offered in a small container located at shoulder level, height 18-25 cm, reaching distance 6-12 cm). In five animals, the changes in configuration and the conjoint actions of the wrist, the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints were assessed with three-dimensional X-ray cinematography (time resolution 20 ms, spatial resolution 1 mm) and video analysis. While approaching the target, the digits were first extended and subsequently abducted. This 'preshaping' consisted of combined angular changes in the MCP and PIP joints, thereby attaining an adequate grip aperture. Each cat used a stable strategy, but different cats used different strategies. In the TT, preshaping involved an MCP extension and a PIP flexion. In the HT, predominant extension of the MCP, predominant extension of the PIP, or a combination of both were used, followed by MCP flexion and PIP flexion. The grip aperture started to decrease before object contact, earlier in the TT, later in the HT. Grasping was achieved by flexion of first the PIP and later the MCP. The X-ray analysis gave evidence for individuated digit movements. Correlation analysis of the angular position of the joints between the different phalanges showed that digits 3 and 4 acted in concert, as did digits 2 and 5, but with clear independence between the different pairs. Furthermore, the different phalanges served different purposes during the grasp. Digits 3, 4 established object contact, digits 2, 5 were mainly used to stabilize the paw onto the surface. The cat distal forelimb
Xu, Gang; Liang, Xifeng; Yao, Shuanbao; Chen, Dawei
2017-01-01
Minimizing the aerodynamic drag and the lift of the train coach remains a key issue for high-speed trains. With the development of computing technology and computational fluid dynamics (CFD) in the engineering field, CFD has been successfully applied to the design process of high-speed trains. However, developing a new streamlined shape for high-speed trains with excellent aerodynamic performance requires huge computational costs. Furthermore, relationships between multiple design variables and the aerodynamic loads are seldom obtained. In the present study, the Kriging surrogate model is used to perform a multi-objective optimization of the streamlined shape of high-speed trains, where the drag and the lift of the train coach are the optimization objectives. To improve the prediction accuracy of the Kriging model, the cross-validation method is used to construct the optimal Kriging model. The optimization results show that the two objectives are efficiently optimized, indicating that the optimization strategy used in the present study can greatly improve the optimization efficiency and meet the engineering requirements. PMID:28129365
Xu, Gang; Liang, Xifeng; Yao, Shuanbao; Chen, Dawei; Li, Zhiwei
2017-01-01
Minimizing the aerodynamic drag and the lift of the train coach remains a key issue for high-speed trains. With the development of computing technology and computational fluid dynamics (CFD) in the engineering field, CFD has been successfully applied to the design process of high-speed trains. However, developing a new streamlined shape for high-speed trains with excellent aerodynamic performance requires huge computational costs. Furthermore, relationships between multiple design variables and the aerodynamic loads are seldom obtained. In the present study, the Kriging surrogate model is used to perform a multi-objective optimization of the streamlined shape of high-speed trains, where the drag and the lift of the train coach are the optimization objectives. To improve the prediction accuracy of the Kriging model, the cross-validation method is used to construct the optimal Kriging model. The optimization results show that the two objectives are efficiently optimized, indicating that the optimization strategy used in the present study can greatly improve the optimization efficiency and meet the engineering requirements.
Computer-aided laser-optoelectronic OPTEL 3D measurement systems of complex-shaped object geometry
NASA Astrophysics Data System (ADS)
Galiulin, Ravil M.; Galiulin, Rishat M.; Bakirov, J. M.; Bogdanov, D. R.; Shulupin, C. O.; Khamitov, D. H.; Khabibullin, M. G.; Pavlov, A. F.; Ryabov, M. S.; Yamaliev, K. N.
1996-03-01
Technical characteristics, advantages and applications of automated optoelectronic measuring systems designed at the Regional Interuniversity Optoelectronic Systems Laboratory ('OPTEL') of Ufa State Aviation Technical University are given. The suggested range of systems is the result of the long-term scientific and research experiments, work on design and introduction work. The system can be applied in industrial development and research, in the field of high precision measurement of geometrical parameters in aerospace, robotic, etc., where non-contact and fast measurements of complicated shape objects made of various materials including brittle and plastic articles are required.
Cornelis, Els V K; van Doorn, Andrea J; Wagemans, Johan
2009-01-01
Mirror reflections and planar rotations of a picture do not result in any variations concerning the internal geometrical layout of the objects depicted in the picture. We examined to what extent these picture plane transformations gave rise to perceptual differences. A large set of pictures was generated by mirror-reflecting and rotating a set of six original photographs in the picture plane. We externalised the percepts of the depicted objects by using a direct perceptual method: the gauge-figure method. Participants had to adjust a gauge figure so that it seemed to be painted on the surface of the depicted object. From an extensive set of settings collected this way, we computed for each picture the three-dimensional interpretation--or pictorial relief--of the depicted object. On the basis of this set of pictorial reliefs, we addressed the effects of mirror reflections and rotations of pictures on the shape percept of the depicted object. Mirror-reflecting a picture around the horizontal axis resulted in large differences in pictorial reliefs, whereas mirror-reflecting pictures around the vertical axis resulted in only small differences in pictorial reliefs. Clockwise 90 degrees, 180 degrees, and 270 degrees rotation affected the pictorial relief significantly. In all cases, the differences between the pictorial reliefs could be resolved by affine transformations, and could thus be ascribed to different solutions of the depth ambiguities inherent in pictures.
Günther, Philipp; Kuschmierz, Robert; Pfister, Thorsten; Czarske, Jürgen W
2013-05-01
The precise distance measurement of fast-moving rough surfaces is important in several applications such as lathe monitoring. A nonincremental interferometer based on two mutually tilted interference fringe systems has been realized for this task. The distance is coded in the phase difference between the generated interference signals corresponding to the fringe systems. Large tilting angles between the interference fringe systems are necessary for a high sensitivity. However, due to the speckle effect at rough surfaces, different envelopes and phase jumps of the interference signals occur. At large tilting angles, these signals become dissimilar, resulting in a small correlation coefficient and a high measurement uncertainty. Based on a matching of illumination and receiving optics, the correlation coefficient and the phase difference estimation have been improved significantly. For axial displacement measurements of recurring rough surfaces, laterally moving with velocities of 5 m/s, an uncertainty of 110 nm has been attained. For nonrecurring surfaces, a distance measurement uncertainty of 830 nm has been achieved. Incorporating the additionally measured lateral velocity and the rotational speed, the two-dimensional shape of rotating objects results. Since the measurement uncertainty of the displacement, distance, and shape is nearly independent of the lateral surface velocity, this technique is predestined for fast-rotating objects, such as crankshafts, camshafts, vacuum pump shafts, or turning parts of lathes.
NASA Astrophysics Data System (ADS)
Nefediev, L. A.; Khakimzyanova, E. I.; Garnaeva, G. I.
2013-12-01
We have studied the information locking effect and the effect of correlation of the shape of an object laser pulse with the shape of a stimulated photon echo response in the presence of external spatially inhomogeneous electric fields. We have shown that, for the transition 3H4-3P0 in a LaF3:Pr3+ crystal, one can observe the effect of the correlation of the shape of an object laser pulse with the shape of a stimulated photon echo response and, depending on the scheme of the action of external spatially inhomogeneous electric fields, either the information locking effect or the information destroying effect.
Photon Rockets Moving Arbitrarily in any Dimension
NASA Astrophysics Data System (ADS)
Podolský, Jiří
A family of explicit exact solutions of Einstein's equations in four and higher dimensions is studied which describes the gravitational field of an object accelerating due to an anisotropic emission of photons. It is possible to prescribe an arbitrary motion, so that the acceleration of such photon rocket need not be uniform — both its magnitude and direction may vary with time. Except at the location of the rocket the space-times have no curvature singularities, and topological defects like cosmic strings are also absent. Any value of a cosmological constant is allowed. We investigate some particular examples of motion, namely a straight flight and a circular trajectory, and we derive the corresponding radiation patterns and the mass loss of the rockets. We also demonstrate the absence of "gravitational aberration" in such space-times. This interesting member of the higher-dimensional Robinson-Trautman class of pure radiation space-times of algebraic Type D generalizes the class of Kinnersley's solutions that has long been known in four-dimensional general relativity.
van Doorn, Andrea J.; Wagemans, Johan
2016-01-01
Research on the influence of reference frames has generally focused on visual phenomena such as the oblique effect, the subjective visual vertical, the perceptual upright, and ambiguous figures. Another line of research concerns mental rotation studies in which participants had to discriminate between familiar or previously seen 2-D figures or pictures of 3-D objects and their rotated versions. In the present study, we disentangled the influence of the environmental and the viewer-centered reference frame, as classically done, by comparing the performances obtained in various picture and participant orientations. However, this time, the performance is the pictorial relief: the probed 3-D shape percept of the depicted object reconstructed from the local attitude settings of the participant. Comparisons between the pictorial reliefs based on different picture and participant orientations led to two major findings. First, in general, the pictorial reliefs were highly similar if the orientation of the depicted object was vertical with regard to the environmental or the viewer-centered reference frame. Second, a viewpoint-from-above interpretation could almost completely account for the shears occurring between the pictorial reliefs. More specifically, the shears could largely be considered as combinations of slants generated from the viewpoint-from-above, which was determined by the environmental as well as by the viewer-centered reference frame. PMID:27433329
NASA Astrophysics Data System (ADS)
Yue, Huimin; Zhao, Biyu; Wu, Yuxiang; Li, Mingyang
2016-06-01
Calibration is a crucial step in fringe projection profilometry, which establishes the relationship between unwrapped phase and (FPP) three-dimensional (3-D) shape data (X,Y,h). For an arbitrarily arranged FPP system, a simple geometrical model and mathematical descriptions of the relationships among phase, height distribution, and transverse coordinate are presented. Based on this, a flexible global calibration method is presented to reconstruct 3-D shape by just using a checkerboard with known separation and alternating white and blue. The calibration board is placed at several random positions to determine the relationship between phase and height, and the relationship between pixel position and X, Y coordinates. To get high accuracy, distortion for each pixel is considered. The validity, flexibility, and practicality of this system and calibration technique are verified by experiments.
Pastukhov, Alexander; Lissner, Anna; Braun, Jochen
2014-02-01
Perceptual adaptation destabilizes the phenomenal appearance of multistable visual displays. Prolonged dominance of a perceptual state fatigues the associated neural population, lowering the likelihood of renewed perception of the same appearance (Nawrot & Blake in Perception & Psychophysics, 49, 230-44, 1991). Here, we used a selective adaptation paradigm to investigate perceptual adaptation for the illusory rotation of ambiguous structure-from-motion (SFM) displays. Specifically, we generated SFM objects with different three-dimensional shapes and presented them in random order, separating successive objects by brief blank periods, which included a mask. To assess the specificity of perceptual adaptation to the shape of SFM objects, we established the probability that a perceived direction of rotation persisted between successive objects of similar or dissimilar shape. We found that the strength of negative aftereffects depended on the volume, but not the shape, of adaptor and probe objects. More voluminous objects were both more effective as adaptor objects and more sensitive as probe objects. Surprisingly, we found these volume effects to be completely independent, since any relationship between two shapes (such as overlap between volumes, similarity of shape, or similarity of velocity profiles) failed to modulate the negative aftereffect. This pattern of results was the opposite of that observed for sensory memory of SFM objects, which reflects similarity between objects, but not volume of individual objects (Pastukhov et al. in Attention, Perception & Psychophysics, 75, 1215-1229, 2013). The disparate specificities of perceptual adaptation and sensory memory for identical SFM objects suggest that the two aftereffects engage distinct neural representations, consistent with recent brain imaging results (Schwiedrzik et al. in Cerebral Cortex, 2012).
String black holes as particle accelerators to arbitrarily high energy
NASA Astrophysics Data System (ADS)
Pradhan, Parthapratim
2014-07-01
We show that an extremal Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole may act as a particle accelerator with arbitrarily high energy when two uncharged particles falling freely from rest to infinity on the near horizon. We show that the center of mass energy of collision is independent of the extreme fine tuning of the angular momentum of the colliding particles. We further show that the center of mass energy of collisions of particles at the ISCO ( r ISCO ) or at the photon orbit ( r ph ) or at the marginally bound circular orbit ( r mb ) i.e. at r≡ r ISCO = r ph = r mb =2 M could be arbitrarily large for the aforementioned space-time, which is quite different from the Schwarzschild and the Reissner-Nordstrøm space-time. For non-extremal GMGHS space-time the CM energy is finite and depends upon the asymptotic value of the dilation field ( ϕ 0).
A cylindrical shell with an arbitrarily oriented crack
NASA Technical Reports Server (NTRS)
Yahsi, O. S.; Erdogan, F.
1982-01-01
The general problem of a shallow shell with constant curvatures is considered. It is assumed that the shell contains an arbitrarily oriented through crack and the material is specially orthotropic. The nonsymmetric problem is solved for arbitrary self equilibrating crack surface tractions, which, added to an appropriate solution for an uncracked shell, would give the result for a cracked shell under most general loading conditions. The problem is reduced to a system of five singular integral equations in a set of unknown functions representing relative displacements and rotations on the crack surfaces. The stress state around the crack tip is asymptotically analyzed and it is shown that the results are identical to those obtained from the two dimensional in plane and antiplane elasticity solutions. The numerical results are given for a cylindrical shell containing an arbitrarily oriented through crack. Some sample results showing the effect of the Poisson's ratio and the material orthotropy are also presented.
Arbitrarily modulated beam for phase-only optical encryption
NASA Astrophysics Data System (ADS)
Chen, Wen; Chen, Xudong
2014-10-01
Optical encryption has attracted more and more attention recently due to its remarkable advantages, such as parallel processing and multiple-dimensional characteristics. In this paper, we propose to apply an arbitrarily modulated beam for phase-only optical encryption. In optical security systems, the plane wave is commonly used for the illumination, and unauthorized receivers may easily obtain or estimate the information related to the illumination beam. The proposed strategy with an arbitrarily modulated illumination beam can effectively enhance system security, since a beam modulation pattern (such as a pinhole-array pattern or a random phase-only pattern) can be considered an additional security key. The phase-only optical encryption is taken as an example for illustrating the validity of the proposed method; however it could be straightforward to apply the proposed strategy to other optical security systems.
Traversable wormholes with arbitrarily small energy condition violations.
Visser, Matt; Kar, Sayan; Dadhich, Naresh
2003-05-23
Traversable wormholes necessarily require violations of the averaged null energy condition, this being the definition of "exotic matter." However, the theorems which guarantee the energy condition violation are remarkably silent when it comes to making quantitative statements regarding the "total amount" of energy condition violating matter in the spacetime. We develop a suitable measure for quantifying this notion and demonstrate the existence of spacetime geometries containing traversable wormholes that are supported by arbitrarily small quantities of exotic matter.
Simple model of a random walk with arbitrarily long memory
NASA Astrophysics Data System (ADS)
Berrones, Arturo; Larralde, Hernán
2001-03-01
We present a generalization of the persistent random-walk model in which the step at time n depends on the state of the step at time n-T, for arbitrary T. This gives rise to arbitrarily long memory effects, yet by an appropriate transformation the model is tractable by essentially the same techniques applicable to the usual persistent random-walk problem. We apply our results to the specific case of delayed ``step'' persistence, and analyze its asymptotic statistical properties.
Kerr black holes as particle accelerators to arbitrarily high energy.
Bañados, Máximo; Silk, Joseph; West, Stephen M
2009-09-11
We show that intermediate mass black holes conjectured to be the early precursors of supermassive black holes and surrounded by relic cold dark matter density spikes can act as particle accelerators with collisions, in principle, at arbitrarily high center-of-mass energies in the case of Kerr black holes. While the ejecta from such interactions will be highly redshifted, we may anticipate the possibility of a unique probe of Planck-scale physics.
NASA Astrophysics Data System (ADS)
Dias-Oliveira, A.; Sicardy, B.; Ortiz, J. L.; Braga-Ribas, F.; Leiva, R.; Vieira-Martins, R.; Benedetti-Rossi, G.; Camargo, J. I. B.; Assafin, M.; Gomes-Júnior, A. R.; Baug, T.; Chandrasekhar, T.; Desmars, J.; Duffard, R.; Santos-Sanz, P.; Ergang, Z.; Ganesh, S.; Ikari, Y.; Irawati, P.; Jain, J.; Liying, Z.; Richichi, A.; Shengbang, Q.; Behrend, R.; Benkhaldoun, Z.; Brosch, N.; Daassou, A.; Frappa, E.; Gal-Yam, A.; Garcia-Lozano, R.; Gillon, M.; Jehin, E.; Kaspi, S.; Klotz, A.; Lecacheux, J.; Mahasena, P.; Manfroid, J.; Manulis, I.; Maury, A.; Mohan, V.; Morales, N.; Ofek, E.; Rinner, C.; Sharma, A.; Sposetti, S.; Tanga, P.; Thirouin, A.; Vachier, F.; Widemann, T.; Asai, A.; Hayato, Watanabe; Hiroyuki, Watanabe; Owada, M.; Yamamura, H.; Hayamizu, T.; Bradshaw, J.; Kerr, S.; Tomioka, H.; Andersson, S.; Dangl, G.; Haymes, T.; Naves, R.; Wortmann, G.
2017-07-01
We present results derived from four stellar occultations by the plutino object (208996) 2003 AZ84, detected on 2011 January 8 (single-chord event), 2012 February 3 (multi-chord), 2013 December 2 (single-chord), and 2014 November 15 (multi-chord). Our observations rule out an oblate spheroid solution for 2003 AZ84's shape. Instead, assuming hydrostatic equilibrium, we find that a Jacobi triaxial solution with semiaxes (470+/- 20)× (383+/- 10)× (245+/- 8) km can better account for all our occultation observations. Combining these dimensions with the rotation period of the body (6.75 hr) and the amplitude of its rotation light curve, we derive a density ρ =0.87+/- 0.01 g cm-3, a geometric albedo {p}V=0.097+/- 0.009. A grazing chord observed during the 2014 occultation reveals a topographic feature along 2003 AZ84's limb, which can be interpreted as an abrupt chasm of width ˜23 km and depth > 8 km, or a smooth depression of width ˜80 km and depth ˜13 km (or an intermediate feature between those two extremes).
Ferrara, Matthew; Arnold, Gregory; Stuff, Mark
2009-10-01
This paper describes an invariant-based shape- and motion reconstruction algorithm for 3D-to-1D orthographically projected range data taken from unknown viewpoints. The algorithm exploits the object-image relation that arises in echo-based range data and represents a simplification and unification of previous work in the literature. Unlike one proposed approach, this method does not require uniqueness constraints, which makes its algorithmic form independent of the translation removal process (centroid removal, range alignment, etc.). The new algorithm, which simultaneously incorporates every projection and does not use an initialization in the optimization process, requires fewer calculations and is more straightforward than the previous approach. Additionally, the new algorithm is shown to be the natural extension of the approach developed by Tomasi and Kanade for 3D-to-2D orthographically projected data and is applied to a realistic inverse synthetic aperture radar imaging scenario, as well as experiments with varying amounts of aperture diversity and noise.
Erguel, Ozguer; Guerel, Levent
2008-12-01
We present a novel stabilization procedure for accurate surface formulations of electromagnetic scattering problems involving three-dimensional dielectric objects with arbitrarily low contrasts. Conventional surface integral equations provide inaccurate results for the scattered fields when the contrast of the object is low, i.e., when the electromagnetic material parameters of the scatterer and the host medium are close to each other. We propose a stabilization procedure involving the extraction of nonradiating currents and rearrangement of the right-hand side of the equations using fictitious incident fields. Then, only the radiating currents are solved to calculate the scattered fields accurately. This technique can easily be applied to the existing implementations of conventional formulations, it requires negligible extra computational cost, and it is also appropriate for the solution of large problems with the multilevel fast multipole algorithm. We show that the stabilization leads to robust formulations that are valid even for the solutions of extremely low-contrast objects.
Baldassi, Carlo; Alemi-Neissi, Alireza; Pagan, Marino; Dicarlo, James J; Zecchina, Riccardo; Zoccolan, Davide
2013-01-01
The anterior inferotemporal cortex (IT) is the highest stage along the hierarchy of visual areas that, in primates, processes visual objects. Although several lines of evidence suggest that IT primarily represents visual shape information, some recent studies have argued that neuronal ensembles in IT code the semantic membership of visual objects (i.e., represent conceptual classes such as animate and inanimate objects). In this study, we investigated to what extent semantic, rather than purely visual information, is represented in IT by performing a multivariate analysis of IT responses to a set of visual objects. By relying on a variety of machine-learning approaches (including a cutting-edge clustering algorithm that has been recently developed in the domain of statistical physics), we found that, in most instances, IT representation of visual objects is accounted for by their similarity at the level of shape or, more surprisingly, low-level visual properties. Only in a few cases we observed IT representations of semantic classes that were not explainable by the visual similarity of their members. Overall, these findings reassert the primary function of IT as a conveyor of explicit visual shape information, and reveal that low-level visual properties are represented in IT to a greater extent than previously appreciated. In addition, our work demonstrates how combining a variety of state-of-the-art multivariate approaches, and carefully estimating the contribution of shape similarity to the representation of object categories, can substantially advance our understanding of neuronal coding of visual objects in cortex.
Arbitrarily high super-resolving phase measurements at telecommunication wavelengths
Kothe, Christian; Bjoerk, Gunnar; Bourennane, Mohamed
2010-06-15
We present two experiments that achieve phase super-resolution at telecommunication wavelengths. One of the experiments is realized in the space domain and the other is realized in the time domain. Both experiments show high visibility and are performed with standard lasers and single-photon detectors. The first experiment uses six-photon coincidences, whereas the latter experiment needs no coincidence measurements, is easy to perform, and achieves, in principle, arbitrarily high phase super-resolution. Here, we demonstrate a 30-fold increase of the resolution. We stress that neither entanglement nor joint detection is needed in these experiments, which demonstrates that neither is necessary to achieve phase super-resolution.
Carrier recovery systems for arbitrarily mapped APK signals
NASA Astrophysics Data System (ADS)
Matsuo, Y.; Namiki, J.
1982-10-01
This paper introduces new carrier recovery techniques for general amplitude-phase keying (APK) modulation signals. The APK's include not only normal QAM but also arbitrarily mapped APK's, including an unsymmetrical APK. Difficulty in phase error detection due to signal mapping complexity, undesirable stable-lock point existence, and the contradiction between a fast acquisition and an accurate steady state performance can be overcome. For that purpose, an acquisition mode and a steady-state mode are used. Furthermore, read-only memories (ROM) are used for recognizing various system states. Random sampling controlled PLL noise performance and acquisition mode carrier recovery circuit pull-in performance with hysteresis property was obtained.
A finite crack with arbitrarily varied surface piezoelectricity
NASA Astrophysics Data System (ADS)
Xu, Yang; Wang, Xu
2017-01-01
We study the contribution of arbitrarily varied surface piezoelectricity to the anti-plane deformation and in-plane electric fields of a hexagonal piezoelectric material containing a finite crack. The varied surface piezoelectricity is incorporated by using an extended version of the continuum-based surface/interface model of Gurtin and Murdoch. In our discussion, the surface properties, including the surface elastic stiffness, the surface piezoelectric modulus and the surface dielectric permittivity, are assumed to be varied arbitrarily along the crack surfaces. By using the Green’s function method, the original boundary value problem is reduced to a system of two coupled first-order Cauchy singular integro-differential equations. Through a diagonalization strategy, the coupled system is transformed into two independent singular integro-differential equations, each of which can be numerically solved by using the collocation method. Our results indicate that the variation of the surface electroelastic moduli exerts a significant influence on the crack opening displacement, the electric potential jump across the crack faces and on the strengths of the logarithmic singularity in stresses and electric displacements at the crack tips.
Analysis of electrophoretic patterns of arbitrarily primed PCR profiling.
Trifunović, Dragana; Radović, Milan; Ristić, Zoran; Guzvić, Miodrag; Dimitrijević, Bogomir
2005-11-01
We present a mathematical algorithm for the analysis of electrophoretic patterns resulting from arbitrarily primed PCR profiling. The algorithm is based on the established mathematical procedures applied to the analysis of digital images of gel patterns. The algorithm includes (a) transformation of the image into a matrix form, (b) identification of every electrophoretic lane as a set of matrix columns that are further mathematically processed, (c) averaging of matrix columns corresponding to electrophoretic lanes that define lane representatives, (d) elimination of "smiling" bands, (e) solving the problem of a lane offset, and (f) removal of the background. Representation of individual electrophoretic lanes in the form of functions allows interlane comparisons and further mathematical analysis. Direct comparison of selected lanes was obtained by employing correlation analysis. Gel images were those obtained after arbitrarily primed PCR analysis of DNA that underwent damage induced by gamma radiation from a (60)Co source. The applied method proved to be useful for elimination of subjectivity of visual inspection. It offers the possibility to avoid overlooking important differences in case of suboptimal electrophoretic resolution. In addition, higher precision is achieved in the assessment of quantitative differences due to better insight into experimental artifacts. These simple mathematical methods offer an open-type algorithm, i.e., this algorithm enables easy implementation of different parameters that may be useful for other analytical needs.
Shape integral method for magnetospheric shapes. [boundary layer calculations
NASA Technical Reports Server (NTRS)
Michel, F. C.
1979-01-01
A method is developed for calculating the shape of any magnetopause to arbitrarily high precision. The method uses an integral equation which is evaluated for a trial shape. The resulting values of the integral equation as a function of auxiliary variables indicate how close one is to the desired solution. A variational method can then be used to improve the trial shape. Some potential applications are briefly mentioned.
Tomo-PIV measurement of flow around an arbitrarily moving body with surface reconstruction
NASA Astrophysics Data System (ADS)
Im, Sunghyuk; Jeon, Young Jin; Sung, Hyung Jin
2015-02-01
A three-dimensional surface of an arbitrarily moving body in a flow field was reconstructed using the DAISY descriptor and epipolar geometry constraints. The surface shape of a moving body was reconstructed with tomographic PIV flow measurement. Experimental images were captured using the tomographic PIV system, which consisted of four high-speed cameras and a laser. The originally captured images, which contained the shape of the arbitrary moving body and the tracer particles, were separated into the particle and surface images using a Gaussian smoothing filter. The weak contrast of the surface images was enhanced using a local histogram equalization method. The histogram-equalized surface images were used to reconstruct the surface shape of the moving body. The surface reconstruction method required a sufficiently detailed surface pattern to obtain the intensity gradient profile of the local descriptor. The separated particle images were used to reconstruct the particle volume intensity via tomographic reconstruction approaches. Voxels behind the reconstructed body surface were neglected during the tomographic reconstruction and velocity calculation. The three-dimensional three-component flow vectors were calculated based on the cross-correlation functions between the reconstructed particle volumes. Three-dimensional experiments that modeled the flows around a flapping flag, a rotating cylinder, and a flapping robot fish tail were conducted to validate the present technique.
Paiton, Dylan M.; Kenyon, Garrett T.; Brumby, Steven P.; Schultz, Peter F.; George, John S.
2015-07-28
An approach to detecting objects in an image dataset may combine texture/color detection, shape/contour detection, and/or motion detection using sparse, generative, hierarchical models with lateral and top-down connections. A first independent representation of objects in an image dataset may be produced using a color/texture detection algorithm. A second independent representation of objects in the image dataset may be produced using a shape/contour detection algorithm. A third independent representation of objects in the image dataset may be produced using a motion detection algorithm. The first, second, and third independent representations may then be combined into a single coherent output using a combinatorial algorithm.
Paiton, Dylan M.; Kenyon, Garrett T.; Brumby, Steven P.; Schultz, Peter F.; George, John S.
2016-10-25
An approach to detecting objects in an image dataset may combine texture/color detection, shape/contour detection, and/or motion detection using sparse, generative, hierarchical models with lateral and top-down connections. A first independent representation of objects in an image dataset may be produced using a color/texture detection algorithm. A second independent representation of objects in the image dataset may be produced using a shape/contour detection algorithm. A third independent representation of objects in the image dataset may be produced using a motion detection algorithm. The first, second, and third independent representations may then be combined into a single coherent output using a combinatorial algorithm.
An active contour-based SSD algorithm for tracking a moving object
NASA Astrophysics Data System (ADS)
Han, Youngjoon; Song, Piljae; Chung, Hwanik; Hahn, Hernsoo
2004-05-01
Since the shape of a 3D object moving in 3D space changes a lot in 2D image due to translation and rotation, it is very difficult to track the object using the SSD algorithm which finds the matching object in the input image using the template of the moving object. To solve the problem, this paper presents an enhanced SSD algorithm which updates the template based on an extended snake algorithm adaptive to the shape variation. The proposed snake algorithm uses the derivative of the area as the constraint energy to determine the boundary of an interested area considering the progressive variation of the shape. The performance of the proposed algorithm has been proved by the experiments where a mobile robot with one camera tracks a 3D target object translating and rotating arbitrarily in the 3D workspace.
Arbitrarily Applicable Comparative Relations: Experimental Evidence for a Relational Operant
Berens, Nicholas M; Hayes, Steven C
2007-01-01
Arbitrarily applicable derived relational responding has been argued by relational frame theorists to be a form of operant behavior. The present study examined this idea with 4 female participants, ages 4 to 5 years old, who could not perform a series of problem-solving tasks involving arbitrary more than and less than relations. In a combined multiple baseline (across responses and participants) and multiple probe design (with trained and untrained stimuli), it was shown that reinforced multiple-exemplar training facilitated the development of arbitrary comparative relations, and that these skills generalized not just across stimuli but also across trial types. The sequence of training identified potential prerequisites in the development of comparative relations (e.g., nonarbitrary comparative relations). Taken as a whole, the present data, along with previous work by others in this area, suggest that relating arbitrary events comparatively is an operant. The implications of this conclusion for the analysis of complex behavior are discussed. PMID:17471793
Arbitrarily laminated, anisotropic cylindrical shell under internal pressure
NASA Technical Reports Server (NTRS)
Chaudhuri, Reaz Z.; Balaraman, K.; Kunukkasseril, Vincent X.
1986-01-01
An arbitrarily laminated, anisotropic cylindrical shell of finite length, under uniform internal pressure, is analyzed using Love-Timoshenko's kinematic relations and under the framework of classical lamination theory. The previously obtained solutions for asymmetrically laminated orthotropic (cross-ply) as well as unbalanced-symmetric and balanced-unsymmetric (angle-ply) cylindrical shells under the same loading conditions have been shown to be special cases of the present closed-form solution. Numerical results have been presented for a two-layer cylindrical shell and compared with those obtained using finite element solutions based on the layerwise constant shear-angle theory. These are expected to serve as benchmark solutions for future comparisons and to facilitate the use of unsymmetric lamination in design.
Arbitrarily Primed PCR To Type Vibrio spp. Pathogenic for Shrimp
Goarant, Cyrille; Merien, Fabrice; Berthe, Franck; Mermoud, Isabelle; Perolat, Philippe
1999-01-01
A molecular typing study on Vibrio strains implicated in shrimp disease outbreaks in New Caledonia and Japan was conducted by using AP-PCR (arbitrarily primed PCR). It allowed rapid identification of isolates at the genospecies level and studies of infraspecific population structures of epidemiological interest. Clusters identified within the species Vibrio penaeicida were related to their area of origin, allowing discrimination between Japanese and New Caledonian isolates, as well as between those from two different bays in New Caledonia separated by only 50 km. Other subclusters of New Caledonian V. penaeicida isolates could be identified, but it was not possible to link those differences to accurate epidemiological features. This contribution of AP-PCR to the study of vibriosis in penaeid shrimps demonstrates its high discriminating power and the relevance of the epidemiological information provided. This approach would contribute to better knowledge of the ecology of Vibrio spp. and their implication in shrimp disease in aquaculture. PMID:10049875
Classical broadcasting is possible with arbitrarily high fidelity and resolution.
Walker, Thomas A; Braunstein, Samuel L
2007-02-23
We quantify the resolution with which any probability distribution may be distinguished from a displaced copy of itself in terms of a characteristic width. This width, which we call the resolution, is well defined for any normalizable probability distribution. We use this concept to study the broadcasting of classical probability distributions. Ideal classical broadcasting creates two (or more) output random variables each of which has the same distribution as the input random variable. We show that the universal broadcasting of probability distributions may be achieved with arbitrarily high fidelities for any finite resolution. By restricting probability distributions to any finite resolution we have therefore shown that the classical limit of quantum broadcasting is consistent with the actual classical case.
Arbitrarily laminated, anisotropic cylindrical shell under internal pressure
NASA Technical Reports Server (NTRS)
Chaudhuri, Reaz Z.; Balaraman, K.; Kunukkasseril, Vincent X.
1986-01-01
An arbitrarily laminated, anisotropic cylindrical shell of finite length, under uniform internal pressure, is analyzed using Love-Timoshenko's kinematic relations and under the framework of classical lamination theory. The previously obtained solutions for asymmetrically laminated orthotropic (cross-ply) as well as unbalanced-symmetric and balanced-unsymmetric (angle-ply) cylindrical shells under the same loading conditions have been shown to be special cases of the present closed-form solution. Numerical results have been presented for a two-layer cylindrical shell and compared with those obtained using finite element solutions based on the layerwise constant shear-angle theory. These are expected to serve as benchmark solutions for future comparisons and to facilitate the use of unsymmetric lamination in design.
Interaction between a circular inclusion and an arbitrarily oriented crack
NASA Technical Reports Server (NTRS)
Erdogan, F.; Gupta, G. D.; Ratwani, M.
1973-01-01
The plane interaction problem for a circular elastic inclusion imbedded into an elastic matrix which contains an arbitrarily oriented crack is considered. Using the existing solutions for the edge dislocations as Green's functions, first the general problem of a through crack in the form of an arbitrary smooth arc located in the matrix in the vicinity of the inclusion is formulated. The integral equations for the line crack are then obtained as a system of singular integral equation with simple Cauchy kernels. The singular behavior of the stresses around the crack tips is examined and the expressions for the stress intensity factors representing the strength of the stress singularities are obtained in terms of the asymptotic values of the density functions of the integral equations. The problem is solved for various typical crack orientations and the corresponding stress intensity factors are given.
Arbitrarily massive sterile neutrinos at the neutrino factory
Meloni, Davide; Tang Jian; Winter, Walter
2011-10-06
We study the effects of one additional sterile neutrino at the Neutrino Factory. On the one hand, we do not impose any constraint on the additional mass squared splitting, which is different from earlier discussions where LSND motivated Q(1)eV{sup 2} is always assumed. We find that a combination of near detectors and long baselines is good at searching for arbitrarily massive sterile neutrinos at the neutrino factory. On the other hand, we compare our sensitivities of mixing angles with the MINOS results where |{Delta}m{sub 41}{sup 2}|>>{Delta}m{sub 31}{sup 2}| is assumed and the fast oscillations in the far detectors are averaged out.
DiCarlo, James J.; Zecchina, Riccardo; Zoccolan, Davide
2013-01-01
The anterior inferotemporal cortex (IT) is the highest stage along the hierarchy of visual areas that, in primates, processes visual objects. Although several lines of evidence suggest that IT primarily represents visual shape information, some recent studies have argued that neuronal ensembles in IT code the semantic membership of visual objects (i.e., represent conceptual classes such as animate and inanimate objects). In this study, we investigated to what extent semantic, rather than purely visual information, is represented in IT by performing a multivariate analysis of IT responses to a set of visual objects. By relying on a variety of machine-learning approaches (including a cutting-edge clustering algorithm that has been recently developed in the domain of statistical physics), we found that, in most instances, IT representation of visual objects is accounted for by their similarity at the level of shape or, more surprisingly, low-level visual properties. Only in a few cases we observed IT representations of semantic classes that were not explainable by the visual similarity of their members. Overall, these findings reassert the primary function of IT as a conveyor of explicit visual shape information, and reveal that low-level visual properties are represented in IT to a greater extent than previously appreciated. In addition, our work demonstrates how combining a variety of state-of-the-art multivariate approaches, and carefully estimating the contribution of shape similarity to the representation of object categories, can substantially advance our understanding of neuronal coding of visual objects in cortex. PMID:23950700
Tawbe, Bilal; Cretu, Ana-Maria
2017-01-01
The realistic representation of deformations is still an active area of research, especially for deformable objects whose behavior cannot be simply described in terms of elasticity parameters. This paper proposes a data-driven neural-network-based approach for capturing implicitly and predicting the deformations of an object subject to external forces. Visual data, in the form of 3D point clouds gathered by a Kinect sensor, is collected over an object while forces are exerted by means of the probing tip of a force-torque sensor. A novel approach based on neural gas fitting is proposed to describe the particularities of a deformation over the selectively simplified 3D surface of the object, without requiring knowledge of the object material. An alignment procedure, a distance-based clustering, and inspiration from stratified sampling support this process. The resulting representation is denser in the region of the deformation (an average of 96.6% perceptual similarity with the collected data in the deformed area), while still preserving the object’s overall shape (86% similarity over the entire surface) and only using on average of 40% of the number of vertices in the mesh. A series of feedforward neural networks is then trained to predict the mapping between the force parameters characterizing the interaction with the object and the change in the object shape, as captured by the fitted neural gas nodes. This series of networks allows for the prediction of the deformation of an object when subject to unknown interactions. PMID:28492473
Zhao, Zhiyang; Peng, Fang; Cavicchi, Kevin A; Cakmak, Mukerrem; Weiss, R A; Vogt, Bryan D
2017-08-16
Three-dimensional printing enables the net shape manufacturing of objects with minimal material waste and low tooling costs, but the functionality is generally limited by available materials, especially for extrusion-based printing, such as fused deposition modeling (FDM). Here, we demonstrate shape memory behavior of 3D printed objects with FDM using a commercially available olefin ionomer, Surlyn 9520, which is zinc-neutralized poly(ethylene-co-methacrylic acid). The initial fixity for 3D printed and compression-molded samples was similar, but the initial recovery was much lower for the 3D printed sample (R = 58%) than that for the compression-molded sample (R = 83%). The poor recovery in the first cycle is attributed to polyethylene crystals formed during programming that act to resist the permanent network recovery. This effect is magnified in the 3D printed part due to the higher strain (lower modulus in the 3D printed part) at a fixed programming stress. The fixity and recovery in subsequent shape memory cycles are greater for the 3D printed part than for the compression-molded part. Moreover, the programmed strain can be systematically modulated by inclusion of porosity in the printed part without adversely impacting the fixity or recovery. These characteristics enable the direct formation of complex shapes of thermoplastic shape memory polymers that can be recovered in three dimensions with the appropriate trigger, such as heat, through the use of FDM as a 3D printing technology.
NASA Astrophysics Data System (ADS)
Abe, M.; Nakayama, T.; Okamura, S.; Matsuoka, K.
2004-11-01
A new technique to calculate an arbitrarily shaped coil winding path for a target magnetic field distribution has been developed. The technique is called DUCAS (Design tool Using Current potentials And SVD, SVD= Singular Value Decomposition). The coil winding surface (CWS) is modeled by triangular finite elements (FEs). The SVD is applied on the response matrix from the current potentials (CPs) of the FE nodes to the magnetic field, to get eigen distribution functions of CPs and singular values (SVs). Using the eigen functions with large SVs, the CP distribution is determined on the CWS so as to reproduce a given magnetic field distribution. Discrete coil shapes are determined along the contour (flow) lines of CPs. The arbitrarily formed CWS is acceptable in DUCAS. We applied the DUCAS on CHS-qa (quasi-axisymmetric Compact Helical System) modular coils and confirmed that the technique is applicable on designs of helical system modular coils.
ERIC Educational Resources Information Center
Field, Charlotte; Allen, Melissa L.; Lewis, Charlie
2016-01-01
We investigate the function bias--generalising words to objects with the same function--in typically developing (TD) children, children with autism spectrum disorder (ASD) and children with other developmental disorders. Across four trials, a novel object was named and its function was described and demonstrated. Children then selected the other…
ERIC Educational Resources Information Center
Holmes, Scott A.; Heath, Matthew
2013-01-01
An issue of continued debate in the visuomotor control literature surrounds whether a 2D object serves as a representative proxy for a 3D object in understanding the nature of the visual information supporting grasping control. In an effort to reconcile this issue, we examined the extent to which aperture profiles for grasping 2D and 3D objects…
ERIC Educational Resources Information Center
Holmes, Scott A.; Heath, Matthew
2013-01-01
An issue of continued debate in the visuomotor control literature surrounds whether a 2D object serves as a representative proxy for a 3D object in understanding the nature of the visual information supporting grasping control. In an effort to reconcile this issue, we examined the extent to which aperture profiles for grasping 2D and 3D objects…
ERIC Educational Resources Information Center
Field, Charlotte; Allen, Melissa L.; Lewis, Charlie
2016-01-01
We investigate the function bias--generalising words to objects with the same function--in typically developing (TD) children, children with autism spectrum disorder (ASD) and children with other developmental disorders. Across four trials, a novel object was named and its function was described and demonstrated. Children then selected the other…
NASA Astrophysics Data System (ADS)
Djupkep Dizeu, F. B.; Laurendeau, Denis; Bendada, Abdelhakim
2016-12-01
Infrared thermography allows contactless non-destructive testing of objects based on their thermal behavior. Quantitative inspection of an object aims to characterize its internal defects by estimating their size and their depth. In the field, a one-dimensional thermal model has been used for depth estimation. Unfortunately, the methods based on this model become inaccurate when the inspected object has a high thermal diffusivity, a complex shape, or when the defects, like corrosion, have a complex geometry. For such cases, a 3D formulation of the problem is needed. In this paper, we consider the defect characterization as an inverse geometry problem and we propose a new method: the rear surface reconstruction by temporal tracking of the thermal front. The idea is to follow the thermal front while it propagates inside the object. Referring to the duality time-depth, at every moment, the penetration depth of the thermal front can be estimated. As soon as the thermal front reaches the rear surface, a temperature change will be noticeable on the frontal surface. It is then possible to update the internal geometry of the object at each time step in such a way that the difference between the theoretical temperature, obtained by a 3D solver, and the experimental temperature, recorded by an infrared camera, is minimized. The proposed method shows accurate results and can address situations involving rear surfaces with complex geometry and objects with high thermal diffusivity and a complex shape.
Spin-torque ferromagnetic resonance in arbitrarily magnetized thin films
NASA Astrophysics Data System (ADS)
Sklenar, Joseph
The spin Hall effect (SHE) in non-magnetic metals can be used to generate spin-transfer-torque (STT), subsequently inducing ferromagnetic resonance (FMR) in magnetic thin films; this experimental method is termed spin-torque ferromagnetic resonance (ST-FMR). Most ST-FMR experiments that are reported have an applied magnetic field in the plane of the sample and the research focuses on material combinations that have large and efficient STT. The most common way ST-FMR signals are detected is through an anisotropic magnetoresistance (AMR) rectification process. In this work we will present ST-FMR results in thin films where the magnetization has both an in-plane and out-of-plane component. The arbitrary magnetization direction is achieved by tipping the applied magnetic field out of the sample plane. We find that when the material system is a permalloy/Pt bilayer, ST-FMR signals are not mirror-symmetric upon magnetic field reversal . This is because the combination of both a STT from the bulk SHE and the Oersted field-like torque from the device do not drive the dynamics in the same manner when the field is reversed. We interpret our results in the Py/Pt experiment by extending an already established ST-FMR lineshape model to describe the general case of arbitrarily magnetized films. We compare and contrast our Py/Pt experiment with another system we measured, a Py/MoS2 bilayer. For the Py/MoS2 system, in-plane experiments suggest that a large STT is present and are comparable to what is observed for the more traditional Py/Pt system . On the other hand, the out-of-plane experiment for the Py/MoS2 system is qualitatively very different from Py/Pt. Our results suggest that ST-FMR experiments for arbitrarily magnetized magnetic films are useful in characterizing STT generated from interface rather than bulk effects. Work at Northwestern was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Materials Science and Engineering Division under grant
Lim, Ik Soo; Leek, E Charles
2012-07-01
Previous empirical studies have shown that information along visual contours is known to be concentrated in regions of high magnitude of curvature, and, for closed contours, segments of negative curvature (i.e., concave segments) carry greater perceptual relevance than corresponding regions of positive curvature (i.e., convex segments). Lately, Feldman and Singh (2005, Psychological Review, 112, 243-252) proposed a mathematical derivation to yield information content as a function of curvature along a contour. Here, we highlight several fundamental errors in their derivation and in its associated implementation, which are problematic in both mathematical and psychological senses. Instead, we propose an alternative mathematical formulation for information measure of contour curvature that addresses these issues. Additionally, unlike in previous work, we extend this approach to 3-dimensional (3D) shape by providing a formal measure of information content for surface curvature and outline a modified version of the minima rule relating to part segmentation using curvature in 3D shape. Copyright 2012 APA, all rights reserved.
NASA Astrophysics Data System (ADS)
Seda Ünal, Gül; Yapar, Ali; Akduman, Ibrahim
2009-06-01
This paper has substantial overlap with the paper 'Reconstruction of surface impedance of an object located over a planar PEC surface' by Gül Seda Ünal, Mehmet Çayören and Evrim Tetik (2008 Journal of Physics: Conference Series 135 012099). Therefore this article has been retracted by IOP Publishing and by the authors, Gül Seda Ünal, Ali Yapar and Ibrahim Akduman.
Iwaki, Sunao; Bonmassar, Giorgio; Belliveau, John W
2013-09-01
Recent neuroimaging studies implicate that both the dorsal and ventral visual pathways, as well as the middle temporal (MT) areas which are critical for the perception of visual motion, are involved in the perception of three-dimensional (3D) structure from two-dimensional (2D) motion (3D-SFM). However, the neural dynamics underlying the reconstruction of a 3D object from 2D optic flow is not known. Here we combined magnetoencephalography (MEG) and functional MRI (fMRI) measurements to investigate the spatiotemporal brain dynamics during 3D-SFM. We manipulated parametrically the coherence of randomly moving groups of dots to create different levels of 3D perception and to study the associated changes in brain activity. At different latencies, the posterior infero-temporal (pIT), the parieto-occipital (PO), and the intraparietal (IP) regions showed increased neural activity during highly coherent motion conditions in which subjects perceived a robust 3D object. Causality analysis between these regions indicated significant causal influence from IP to pIT and from pIT to PO only in conditions where subjects perceived a robust 3D object. Current results suggest that the perception of a 3D object from 2D motion includes integration of global motion and 3D mental image processing, as well as object recognition that are accomplished by interactions between the dorsal and ventral visual pathways.
Thermal modeling of bore fields with arbitrarily oriented boreholes
NASA Astrophysics Data System (ADS)
Lazzarotto, Alberto
2016-04-01
The accurate prediction of the thermal behavior of bore fields for shallow geothermal applications is necessary to carry out a proper design of such systems. A classical methodology to perform this analysis is the so-called g-function method. Most commercial tools implementing this methodology are designed to handle only bore fields configurations with vertical boreholes. This is a limitation since this condition might not apply in a real installation. In a recent development by the author, a semi-analytical method to determine g-function for bore fields with arbitrarily oriented boreholes was introduced. The strategy utilized is based on the idea introduced by Cimmino of representing boreholes as stacked finite line sources. The temperature along these finite lines is calculated by applying the superposition of the effects of each linear heat source in the field. This modeling technique allows to approximate uneven heat distribution along the boreholes which is a key feature for the calculation of g-functions according to Eskilson's boundary conditions. The method has been tested for a few simple configurations and showed results that are similar compare to previous results computed numerically by Eskilson. The method has been then successfully applied to the g-function calculation of an existing large scale highly asymmetrical bore field.
On wormholes with arbitrarily small quantities of exotic matter
Fewster, Christopher J.; Roman, Thomas A.
2005-08-15
Recently several models of traversable wormholes have been proposed which require only arbitrarily small amounts of negative energy to hold them open against self-collapse. If the exotic matter is assumed to be provided by quantum fields, then quantum inequalities can be used to place constraints on the negative energy densities required. In this paper, we introduce an alternative method for obtaining constraints on wormhole geometries, using a recently derived quantum inequality bound on the null-contracted stress-energy averaged over a timelike worldline. The bound allows us to perform a simplified analysis of general wormhole models, not just those with small quantities of exotic matter. We then use it to study, in particular, the models of Visser, Kar, and Dadhich (VKD) and the models of Kuhfittig. The VKD models are constrained to be either submicroscopic or to have a large discrepancy between throat size and curvature radius. A recent model of Kuhfittig is shown to be nontraversable. This is due to the fact that the throat of his wormhole flares outward so slowly that light rays and particles, starting from outside the throat, require an infinite lapse of affine parameter to reach the throat.
Mathematical Constraints on FST: Biallelic Markers in Arbitrarily Many Populations.
Alcala, Nicolas; Rosenberg, Noah A
2017-07-01
[Formula: see text] is one of the most widely used statistics in population genetics. Recent mathematical studies have identified constraints that challenge interpretations of [Formula: see text] as a measure with potential to range from 0 for genetically similar populations to 1 for divergent populations. We generalize results obtained for population pairs to arbitrarily many populations, characterizing the mathematical relationship between [Formula: see text] the frequency M of the more frequent allele at a polymorphic biallelic marker, and the number of subpopulations K We show that for fixed K, [Formula: see text] has a peculiar constraint as a function of M, with a maximum of 1 only if [Formula: see text] for integers i with [Formula: see text] For fixed M, as K grows large, the range of [Formula: see text] becomes the closed or half-open unit interval. For fixed K, however, some [Formula: see text] always exists at which the upper bound on [Formula: see text] lies below [Formula: see text] We use coalescent simulations to show that under weak migration, [Formula: see text] depends strongly on M when K is small, but not when K is large. Finally, examining data on human genetic variation, we use our results to explain the generally smaller [Formula: see text] values between pairs of continents relative to global [Formula: see text] values. We discuss implications for the interpretation and use of [Formula: see text]. Copyright © 2017 by the Genetics Society of America.
Arbitrarily Complex Chemical Reactions on Particles
NASA Astrophysics Data System (ADS)
Benson, D. A.; Bolster, D.
2016-12-01
Previous particle-tracking (PT) algorithms for chemical reaction conceptualize each particle being composed of one species. Reactions occur by either complete or partial birth/death processes between interacting particles. Here we extend the method by placing any number of chemical species on each particle, thereby allowing the single-step calculation of arbitrarily complex reactions using standard methods. The algorithm relies on calculating the correct mass transfer of species between particles, which is exactly given by our previous probabilistic algorithm. The various novel components of the new method are verified against analytic solutions where possible. The potential benefits of the method have been discussed elsewhere in the context of simple bimolecular reactions: the PT method does not artificially mix constituents by numerical dispersion, the particles do not have a Courant number criterion for stability, and the number of particles is very often going to be smaller than the number of cells in a typical grid-based simulation, so that the number of numerical geochemical calculations is similarly smaller.
Funnell, Elaine; Wilding, John
2011-02-01
We report a longitudinal study of an exceptional child (S.R.) whose early-acquired visual agnosia, following encephalitis at 8 weeks of age, did not prevent her from learning to construct an increasing vocabulary of visual object forms (drawn from different categories), albeit slowly. S.R. had problems perceiving subtle differences in shape; she was unable to segment local letters within global displays; and she would bring complex scenes close to her eyes: a symptom suggestive of an attempt to reduce visual crowding. Investigations revealed a robust ability to use the gestalt grouping factors of proximity and collinearity to detect fragmented forms in noisy backgrounds, compared with a very weak ability to segment fragmented forms on the basis of contrasts of shape. When contrasts in spatial grouping and shape were pitted against each other, shape made little contribution, consistent with problems in perceiving complex scenes, but when shape contrast was varied, and spatial grouping was held constant, S.R. showed the same hierarchy of difficulty as the controls, although her responses were slowed. This is the first report of a child's visual-perceptual development following very early neurological impairments to the visual cortex. Her ability to learn to perceive visual shape following damage at a rudimentary stage of perceptual development contrasts starkly with the loss of such ability in childhood cases of acquired visual agnosia that follow damage to the established perceptual system. Clearly, there is a critical period during which neurological damage to the highly active, early developing visual-perceptual system does not prevent but only impairs further learning.
Moment Method Solutions for Radiation and Scattering from Arbitrarily Shaped Surfaces.
1981-02-01
without changing the exterior fields, but making fields inter- ior to S vanish 5 3 The exterior scattered fields generated by (s, !s) 7 4 Thin-wire V...From the surface-equivalence theorem of Schelkunoff [18], the field interior to the surface S will vanish without changing the exterior field if the...are placed on S without changing the exterior fields, bui making fields interior to S vanish. 5 If (Ji’ M1) generate the incident fields (E., H
Video coding using arbitrarily shaped block partitions in globally optimal perspective
NASA Astrophysics Data System (ADS)
Paul, Manoranjan; Murshed, Manzur
2011-12-01
Algorithms using content-based patterns to segment moving regions at the macroblock (MB) level have exhibited good potential for improved coding efficiency when embedded into the H.264 standard as an extra mode. The content-based pattern generation (CPG) algorithm provides local optimal result as only one pattern can be optimally generated from a given set of moving regions. But, it failed to provide optimal results for multiple patterns from entire sets. Obviously, a global optimal solution for clustering the set and then generation of multiple patterns enhances the performance farther. But a global optimal solution is not achievable due to the non-polynomial nature of the clustering problem. In this paper, we propose a near- optimal content-based pattern generation (OCPG) algorithm which outperforms the existing approach. Coupling OCPG, generating a set of patterns after clustering the MBs into several disjoint sets, with a direct pattern selection algorithm by allowing all the MBs in multiple pattern modes outperforms the existing pattern-based coding when embedded into the H.264.
Transport coefficients for electrolytes in arbitrarily shaped nano- and microfluidic channels
NASA Astrophysics Data System (ADS)
Mortensen, N. A.; Olesen, L. H.; Bruus, H.
2006-03-01
We consider laminar flow of incompressible electrolytes in long, straight channels driven by pressure and electro-osmosis. We use a Hilbert space eigenfunction expansion to address the general problem of an arbitrary cross-section and obtain general results in linear-response theory for the hydraulic and electrical transport coefficients which satisfy Onsager relations. In the limit of non-overlapping Debye layers, the transport coefficients are simply expressed in terms of parameters of the electrolyte as well as the geometrical correction factor for the Hagen Poiseuille part of the problem. In particular, we consider the limits of thin non-overlapping as well as strongly overlapping Debye layers, respectively, and calculate the corrections to the hydraulic resistance due to electro-hydrodynamic interactions.
NASA Astrophysics Data System (ADS)
Elsner, Robert; Puhlmann, Dirk; Pieplow, Gregor; Heuer, Axel; Menzel, Ralf
2015-09-01
Entangled photons generated by spontaneous parametric down conversion inside a nonlinear crystal exhibit a complex spatial photon count distribution. A quantitative description of this distribution helps with the interpretation of experiments that depend on this structure. We developed a theoretical model and an accompanying numerical calculation that includes the effects of phase matching and the crystal properties to describe a wide range of spatial effects in two-photon experiments. The numerical calculation was tested against selected analytical approximations. We furthermore performed a double-slit experiment where we measured the visibility V and the distinguishability D and obtained $D^2 + V^2 = 1.43$. The numerical model accurately predicts these experimental results.
1980-12-01
show measurementson a circular cylinder 2.76 wavelengths long for E and H plane aspect angles. Figure Ila and llb show the measured data for flat...34 Proc. IEEE, Vol. 68, pp. 248-263, Feb. 1980. 18. S.W. Lee, J. Boersma,C.L. Law and G.A. Deschamps, "Singularity in Green’s function and its numerical...and R. Sikorski, Theory of Distributions - the Sequential Approach, Elsevier Scientific Publishing Company . Amsterdam, 1973. 2 . L. Schwartz, Th&orie
Analysis and Measurements of Three-Dimensional Arbitrarily-Shaped Dielectric Scatterers.
1980-05-01
the principal volume and considered it a part of the definition for the Green’s function in the source region. Lee and Law [231 showed that AV in...known. The close agreement shows that accurate measurements can be made for small scatterers with low echo return. Figure Ila and llb show measurementson...Methods of Theoretical Physics, New York: McGraw-Hill Company , 1953. 6. R.E. Collin, Field Theory of Guided Waves, New York: McGraw-Hill Company , 1960. 7. J
A contact stress model for multifingered grasps of rough objects
NASA Technical Reports Server (NTRS)
Sinha, Pramath Raj; Abel, Jacob M.
1990-01-01
The model developed utilizes a contact-stress analysis of an arbitrarily shaped object in a multifingered grasp. The fingers and the object are all treated as elastic bodies, and the region of contact is modeled as a deformable surface patch. The relationship between the friction and normal forces is nonlocal and nonlinear in nature and departs from the Coulomb approximation. The nature of the constraints arising out of conditions for compatibility and static equilibrium motivated the formulation of the model as a nonlinear constrained minimization problem. The model is able to predict the magnitude of the inwardly directed normal forces and both the magnitude and direction of the tangential (friction) forces at each finger-object interface for grasped objects in static equilibrium.
A contact stress model for multifingered grasps of rough objects
NASA Technical Reports Server (NTRS)
Sinha, Pramath Raj; Abel, Jacob M.
1990-01-01
The model developed utilizes a contact-stress analysis of an arbitrarily shaped object in a multifingered grasp. The fingers and the object are all treated as elastic bodies, and the region of contact is modeled as a deformable surface patch. The relationship between the friction and normal forces is nonlocal and nonlinear in nature and departs from the Coulomb approximation. The nature of the constraints arising out of conditions for compatibility and static equilibrium motivated the formulation of the model as a nonlinear constrained minimization problem. The model is able to predict the magnitude of the inwardly directed normal forces and both the magnitude and direction of the tangential (friction) forces at each finger-object interface for grasped objects in static equilibrium.
2016-01-01
Previous studies have shown that the perceptual organization of the visual scene constrains the deployment of attention. Here we investigated how the organization of multiple elements into larger configurations alters their attentional weight, depending on the “pertinence” or behavioral importance of the elements’ features. We assessed object-based effects on distinct aspects of the attentional priority map: top-down control, reflecting the tendency to encode targets rather than distracters, and the spatial distribution of attention weights across the visual scene, reflecting the tendency to report elements belonging to the same rather than different objects. In 2 experiments participants had to report the letters in briefly presented displays containing 8 letters and digits, in which pairs of characters could be connected with a line. Quantitative estimates of top-down control were obtained using Bundesen’s Theory of Visual Attention (1990). The spatial distribution of attention weights was assessed using the “paired response index” (PRI), indicating responses for within-object pairs of letters. In Experiment 1, grouping along the task-relevant dimension (targets with targets and distracters with distracters) increased top-down control and enhanced the PRI; in contrast, task-irrelevant grouping (targets with distracters) did not affect performance. In Experiment 2, we disentangled the effect of target-target and distracter-distracter grouping: Pairwise grouping of distracters enhanced top-down control whereas pairwise grouping of targets changed the PRI. We conclude that object-based perceptual representations interact with pertinence values (of the elements’ features and location) in the computation of attention weights, thereby creating a widespread pattern of attentional facilitation across the visual scene. PMID:26752732
Waxman, Sandra R.; Fu, Xiaolan; Ferguson, Brock; Geraghty, Kathleen; Leddon, Erin; Liang, Jing; Zhao, Min-Fang
2016-01-01
Researchers have proposed that the culture in which we are raised shapes the way that we attend to the objects and events that surround us. What remains unclear, however, is how early any such culturally-inflected differences emerge in development. Here, we address this issue directly, asking how 24-month-old infants from the US and China deploy their attention to objects and actions in dynamic scenes. By analyzing infants' eye movements while they observed dynamic scenes, the current experiment revealed striking convergences, overall, in infants' patterns of visual attention in the two communities, but also pinpointed a brief period during which their attention reliably diverged. This divergence, though modest, suggested that infants from the US devoted relatively more attention to the objects and those from China devoted relatively more attention to the actions in which they were engaged. This provides the earliest evidence for strong overlap in infants' attention to objects and events in dynamic scenes, but also raises the possibility that by 24 months, infants' attention may also be shaped subtly by the culturally-inflected attentional proclivities characteristic of adults in their cultural communities. PMID:26903905
Waxman, Sandra R; Fu, Xiaolan; Ferguson, Brock; Geraghty, Kathleen; Leddon, Erin; Liang, Jing; Zhao, Min-Fang
2016-01-01
Researchers have proposed that the culture in which we are raised shapes the way that we attend to the objects and events that surround us. What remains unclear, however, is how early any such culturally-inflected differences emerge in development. Here, we address this issue directly, asking how 24-month-old infants from the US and China deploy their attention to objects and actions in dynamic scenes. By analyzing infants' eye movements while they observed dynamic scenes, the current experiment revealed striking convergences, overall, in infants' patterns of visual attention in the two communities, but also pinpointed a brief period during which their attention reliably diverged. This divergence, though modest, suggested that infants from the US devoted relatively more attention to the objects and those from China devoted relatively more attention to the actions in which they were engaged. This provides the earliest evidence for strong overlap in infants' attention to objects and events in dynamic scenes, but also raises the possibility that by 24 months, infants' attention may also be shaped subtly by the culturally-inflected attentional proclivities characteristic of adults in their cultural communities.
Marquis, R; Schmittbuhl, M; Mazzella, W D; Taroni, F
2005-05-28
In view of contributing to the scientific validation of the individuality of handwriting, the testing of the two so called fundamental laws of handwriting--1: no two people write exactly alike; 2: no one person writes the same word exactly the same way twice--was approached by analysing the shape of 445 handwritten capital characters O produced by three individuals. A methodology based on classical Fourier descriptors was applied to the characters contours, which were extracted through an automated procedure of image analysis. Precise individual characterization of the shape was possible through Fourier analysis. Within-writer variability of the shape of character O for the writers selected could be shown in an objective and quantitative way through the statistical analysis of the Fourier descriptors. It was demonstrated that this polymorphism differed between the three writers. Differentiation between writers was quantitatively demonstrated by discriminant analysis of the Fourier descriptors, and by the existence of marked morphological distances between the set of characters O of each writer. The degree of dissimilitude of the character O writings could, thus, be assessed. Because of relatively reduced within-writer variability and a pronounced differentiation between the writers, a morphological profile could be established and discrimination between writers could be obtained through the quantification of the shape of one handwritten character.
Deceleration of arbitrarily magnetized GRB ejecta: the complete evolution
NASA Astrophysics Data System (ADS)
Mimica, P.; Giannios, D.; Aloy, M. A.
2009-02-01
Context: The role of magnetic fields in gamma-ray burst (GRB) flows remains debated. If of sufficient strength, they can leave their signature on the initial phases of the afterglow by substantially changing the backreaction of the flow as a consequence of its interaction with the external medium. Aims: We attempt to understand quantitatively the dynamical effect and observational signatures of GRB ejecta magnetization on the onset of the afterglow. Methods: We perform ultrahigh-resolution, one-dimensional, relativistic MHD simulations of the interaction between a radially expanding, magnetized ejecta with the interstellar medium. We require ultrahigh numerical resolution because of the extreme jump conditions in the region of interaction between the ejecta and the circumburst medium. We study the complete evolution of an ultrarelativistic shell to the self-similar asymptotic phase. Results: Our simulations demonstrate that the complete evolution can be characterized in terms of two parameters, the ξ parameter introduced by Sari and Piran and the magnetization σ_0. We use this fact in producing numerical models in which the shell Lorentz factor γ0 is between 10 and 20 and rescaling the results to arbitrarily large values of γ_0. We find that the reverse shock is typically weak or absent for ejecta characterized by σ_0⪆ 1. The onset of the forward shock emission is strongly dependent on the magnetization. On the other hand, the magnetic energy of the shell is transferred into the external medium on a short timescale (of several times the duration of the burst). The later forward shock emission contains no information about the initial magnetization of the flow. The asymptotic evolution of strongly magnetized shells, after experiencing significant deceleration, resembles that of hydrodynamic shells, i.e. they enter fully into the Blandford-McKee self-similar regime.
NASA Astrophysics Data System (ADS)
Yoshizawa, Toru; Yamamoto, Masayuki; Ikeda, Takahiro
2005-08-01
Non-contact displacement measurement is one of important topics to analyze materials strength and structural deformation. In addition to the industrial applications in mechanical engineering, some research works in such fields as medical and dental fields, life science, textile industry, and even in cosmetics industry require non-contact methods for their specified research areas. Here we propose that both displacement of surface points and profile of an objective are able to be captured by processing textured random pattern on the surface and projected fringe pattern onto the sample. A few potentiall applications to dental and cosmetics fields using our proposal are included.
NASA Astrophysics Data System (ADS)
Qi, Li; Wang, Shun; Zhang, Yixin; Sun, Yingying; Zhang, Xuping
2015-11-01
The quality inspection process is usually carried out after first processing of the raw materials such as cutting and milling. This is because the parts of the materials to be used are unidentified until they have been trimmed. If the quality of the material is assessed before the laser process, then the energy and efforts wasted on defected materials can be saved. We proposed a new production scheme that can achieve quantitative quality inspection prior to primitive laser cutting by means of three-dimensional (3-D) vision measurement. First, the 3-D model of the object is reconstructed by the stereo cameras, from which the spatial cutting path is derived. Second, collaborating with another rear camera, the 3-D cutting path is reprojected to both the frontal and rear views of the object and thus generates the regions-of-interest (ROIs) for surface defect analysis. An accurate visual guided laser process and reprojection-based ROI segmentation are enabled by a global-optimization-based trinocular calibration method. The prototype system was built and tested with the processing of raw duck feathers for high-quality badminton shuttle manufacture. Incorporating with a two-dimensional wavelet-decomposition-based defect analysis algorithm, both the geometrical and appearance features of the raw feathers are quantified before they are cut into small patches, which result in fully automatic feather cutting and sorting.
NASA Astrophysics Data System (ADS)
Boche, Holger; Cai, Minglai; Deppe, Christian; Nötzel, Janis
2017-01-01
We determine the secrecy capacities under common randomness assisted coding of arbitrarily varying classical-quantum wiretap channels. Furthermore, we determine the secrecy capacity of a mixed channel model which is compound from the sender to the legitimate receiver and varies arbitrarily from the sender to the eavesdropper. We examine when the secrecy capacity is a continuous function of the system parameters as an application and show that resources, e.g., having access to a perfect copy of the outcome of a random experiment, can guarantee continuity of the capacity function of arbitrarily varying classical-quantum wiretap channels.
Braga-Ribas, F.; Vieira-Martins, R.; Camargo, J. I. B.; Sicardy, B.; Lellouch, E.; Lecacheux, J.; Ortiz, J. L.; Morales, N.; Tancredi, G.; Roland, S.; Bruzzone, S.; Assafin, M.; Vachier, F.; Colas, F.; Maury, A.; Emilio, M.; Amorim, A.; Unda-Sanzana, E.; Almeida, L. A.; and others
2013-08-10
We present results derived from the first multi-chord stellar occultations by the transneptunian object (50000) Quaoar, observed on 2011 May 4 and 2012 February 17, and from a single-chord occultation observed on 2012 October 15. If the timing of the five chords obtained in 2011 were correct, then Quaoar would possess topographic features (crater or mountain) that would be too large for a body of this mass. An alternative model consists in applying time shifts to some chords to account for possible timing errors. Satisfactory elliptical fits to the chords are then possible, yielding an equivalent radius R{sub equiv} = 555 {+-} 2.5 km and geometric visual albedo p{sub V} = 0.109 {+-} 0.007. Assuming that Quaoar is a Maclaurin spheroid with an indeterminate polar aspect angle, we derive a true oblateness of {epsilon}= 0.087{sup +0.0268}{sub -0.0175}, an equatorial radius of 569{sup +24}{sub -17} km, and a density of 1.99 {+-} 0.46 g cm{sup -3}. The orientation of our preferred solution in the plane of the sky implies that Quaoar's satellite Weywot cannot have an equatorial orbit. Finally, we detect no global atmosphere around Quaoar, considering a pressure upper limit of about 20 nbar for a pure methane atmosphere.
Speiser, Daniel I; Gagnon, Yakir Luc; Chhetri, Raghav K; Oldenburg, Amy L; Johnsen, Sönke
2016-11-01
The eyes of scallops form images using a concave spherical mirror and contain two separate retinas, one layered on top of the other. Behavioral and electrophysiological studies indicate that the images formed by these eyes have angular resolutions of about 2°. Based on previous ray-tracing models, it has been thought that the more distal of the two retinas lies near the focal point of the mirror and that the proximal retina, positioned closer to the mirror at the back of the eye, receives light that is out-of-focus. Here, we propose three mechanisms through which both retinas may receive focused light: (1) chromatic aberration produced by the lens may cause the focal points for longer and shorter wavelengths to fall near the distal and proximal retinas, respectively; (2) focused light from near and far objects may fall on the distal and proximal retinas, respectively; and (3) the eyes of scallops may be dynamic structures that change shape to determine which retina receives focused light. To test our hypotheses, we used optical coherence tomography (OCT), a method of near-infrared optical depth-ranging, to acquire virtual cross-sections of live, intact eyes from the bay scallop Argopecten irradians Next, we used a custom-built ray-tracing model to estimate the qualities of the images that fall on an eye's distal and proximal retinas as functions of the wavelengths of light entering the eye (400-700 nm), object distances (0.01-1 m), and the overall shape of the eye. When we assume 550 nm wavelength light and object distances greater than 0.01 m, our model predicts that the angular resolutions of the distal and proximal retinas are 2° and 7°, respectively. Our model also predicts that neither chromatic aberration nor differences in object distance lead to focused light falling on the distal and proximal retinas simultaneously. However, if scallops can manipulate the shapes of their eyes, perhaps through muscle contractions, we speculate that they may be able
Speckle size of light scattered from 3D rough objects.
Zhang, Geng; Wu, Zhensen; Li, Yanhui
2012-02-13
From scalar Helmholtz integral relation and by coordinate system transformation, this paper begins with a derivation of the far-zone speckle field in the observation plane perpendicular to the scattering direction from an arbitrarily shaped conducting rough object illuminated by a plane wave illumination, followed by the spatial correlation function of the speckle intensity to obtain the speckle size from the objects. Especially, the specific expressions for the speckle sizes of light backscattered from spheres, cylinders and cones are obtained in detail showing that the speckle size along one direction in the observation plane is proportional to the incident wavelength and the distance between the object and the observation plane, and is inverse proportional to the maximal illuminated dimension of the object parallel to the direction. In addition, the shapes of the speckle of the rough objects with different shapes are different. The investigation on the speckle size in this paper will be useful for the statistical properties of speckle from complicated rough objects and the speckle imaging to target detection and identification.
Balashov, Victor; Cherkasova, Maria; Kruglov, Kirill; Kudriavtsev, Arseny; Masherov, Pavel; Mogulkin, Andrey; Obukhov, Vladimir; Riaby, Valentin; Svotina, Victoria
2017-08-01
A theoretical-experimental research has been carried out to determine the characteristics of a radio frequency (RF) ion source for the generation of a weakly expanding wedge-shaped xenon ion beam. Such ion beam geometry is of interest as a prototype of an on-board ion injector for contactless "ion shepherding" by service spacecraft to remove large space debris objects from geostationary orbits. The wedge shape of the ion beam increases its range. The device described herein comprises an inductive gas discharge chamber and a slit-type three-electrode ion extraction grid (IEG) unit. Calculations of accelerating cell geometries and ion trajectories determined the dependence of beam expansion half-angle on normalized perveance based on the measurements of the spatial distributions of the xenon plasma parameters at the IEG entrance for a xenon flow rate q ≈ 0.2 mg/s and an incident RF power Pin ≤ 250 W at a driving frequency f = 2 MHz. Experimental studies showed that the ion beam, circular at the IEG exit, accepted the elliptical form at the distance of 580 mm with half-angle of beam expansion across IEG slits about 2°-3° and close to 0° along them. Thus, the obtained result proved the possibility of creating a new-generation on-board ion injector that could be used in spacecrafts for removal of debris.
NASA Astrophysics Data System (ADS)
Balashov, Victor; Cherkasova, Maria; Kruglov, Kirill; Kudriavtsev, Arseny; Masherov, Pavel; Mogulkin, Andrey; Obukhov, Vladimir; Riaby, Valentin; Svotina, Victoria
2017-08-01
A theoretical-experimental research has been carried out to determine the characteristics of a radio frequency (RF) ion source for the generation of a weakly expanding wedge-shaped xenon ion beam. Such ion beam geometry is of interest as a prototype of an on-board ion injector for contactless "ion shepherding" by service spacecraft to remove large space debris objects from geostationary orbits. The wedge shape of the ion beam increases its range. The device described herein comprises an inductive gas discharge chamber and a slit-type three-electrode ion extraction grid (IEG) unit. Calculations of accelerating cell geometries and ion trajectories determined the dependence of beam expansion half-angle on normalized perveance based on the measurements of the spatial distributions of the xenon plasma parameters at the IEG entrance for a xenon flow rate q ≈ 0.2 mg/s and an incident RF power Pin ≤ 250 W at a driving frequency f = 2 MHz. Experimental studies showed that the ion beam, circular at the IEG exit, accepted the elliptical form at the distance of 580 mm with half-angle of beam expansion across IEG slits about 2°-3° and close to 0° along them. Thus, the obtained result proved the possibility of creating a new-generation on-board ion injector that could be used in spacecrafts for removal of debris.
The creation of local clusters in arbitrarily given grids
NASA Technical Reports Server (NTRS)
Eiseman, Peter R.
1986-01-01
A method is presented to smoothly insert pointwise clusters into any given grid regardless of its origin, its topology, or its dimensionality. The process amounts to a local movement of the given coordinate curves or surfaces to more highly resolve an object. The object about which clustering is created can be a point, a curve, a surface, or segments of a curve or surface. The basic clustering capability is established by forming a grid operator for a single cluster. With a view toward multiple clusters being created about various objects, the basic operator is seen as an elementary operator. An algorithm is presented to execute the general elementary operation in three dimensions. In FORTRAN, this assumes the form of a subroutine which is fully operational and is presented to serve as a basic model for any such elementary clustering operation.
NASA Technical Reports Server (NTRS)
Chiang, C. K.; Xue, David Y.; Mei, Chuh
1993-01-01
A finite element formulation is presented for determining the large-amplitude free and steady-state forced vibration response of arbitrarily laminated anisotropic composite thin plates using the Discrete Kirchhoff Theory (DKT) triangular elements. The nonlinear stiffness and harmonic force matrices of an arbitrarily laminated composite triangular plate element are developed for nonlinear free and forced vibration analyses. The linearized updated-mode method with nonlinear time function approximation is employed for the solution of the system nonlinear eigenvalue equations. The amplitude-frequency relations for convergence with gridwork refinement, triangular plates, different boundary conditions, lamination angles, number of plies, and uniform versus concentrated loads are presented.
Entanglement-assisted classical capacities of compound and arbitrarily varying quantum channels
NASA Astrophysics Data System (ADS)
Boche, Holger; Janßen, Gisbert; Kaltenstadler, Stephan
2017-04-01
We consider classical message transmission under entanglement assistance for compound memoryless and arbitrarily varying quantum channels. In both cases, we prove general coding theorems together with corresponding weak converse bounds. In this way, we obtain single-letter characterizations of the entanglement-assisted classical capacities for both channel models. Moreover, we show that the entanglement-assisted classical capacity does exhibit no strong converse property for some compound quantum channels for the average as well as the maximal error criterion. A strong converse to the entanglement-assisted classical capacities does hold for each arbitrarily varying quantum channel.
An arbitrarily short reply to Sheldon Smith on instantaneous velocities
NASA Astrophysics Data System (ADS)
Arntzenius, Frank
The main issue is the question whether the standard calculus definition of velocities allows velocities to be part of the instantaneous states of objects. According to David Albert and I this is implausible, for if they were, then the instantaneous state of an object at a time t would in virtue of logic and definition alone impose a severe constraint on the history of instantaneous states of that object at other times. One can picture the constraint as follows: represent the position at time t by a dot on a piece of paper; represent the velocity at time t by an arrow that points away from that dot. The positions around time t can then be represented as a (parameterized) curve. The constraint now is that the curve must have the arrow as its tangent: as one gets close to t the curve must become parallel to the arrow (and must be parameterized at a rate that corresponds to the length of the arrow). This rules out many possible histories at times other than t. But surely an instantaneous state at time t ought not by logic and definition alone to constrain histories of instantaneous states at other times. Laws of nature and contingent relations can imply such constraints, but logic and definition should not. Compare: the intrinsic state at some spatial location x ought not by logic and definition alone to constrain the intrinsic states at other spatial locations. (For Lewis (1986) this is virtually a definition of "intrinsic".)
High Frequency Scattering from Arbitrarily Oriented Dielectric Disks
NASA Technical Reports Server (NTRS)
Levine, D. M.; Meneghini, R.; Lang, R. H.; Seker, S. S.
1982-01-01
Calculations have been made of electromagnetic wave scattering from dielectric disks of arbitrary shape and orientation in the high frequency (physical optics) regime. The solution is obtained by approximating the fields inside the disk with the fields induced inside an identically oriented slab (i.e. infinite parallel planes) with the same thickness and dielectric properties. The fields inside the disk excite conduction and polarization currents which are used to calculate the scattered fields by integrating the radiation from these sources over the volume of the disk. This computation has been executed for observers in the far field of the disk in the case of disks with arbitrary orientation and for arbitrary polarization of the incident radiation. The results have been expressed in the form of a dyadic scattering amplitude for the disk. The results apply to disks whose diameter is large compared to wavelength and whose thickness is small compared to diameter, but the thickness need not be small compared to wavelength. Examples of the dependence of the scattering amplitude on frequency, dielectric properties of the disk and disk orientation are presented for disks of circular cross section.
Compact stars in the braneworld: A new branch of stellar configurations with arbitrarily large mass
NASA Astrophysics Data System (ADS)
Lugones, Germán; Arbañil, José D. V.
2017-03-01
We study the properties of compact stars in the Randall-Sundrum type-II braneworld (BW) model. To this end, we solve the braneworld generalization of the stellar structure equations for a static fluid distribution with spherical symmetry considering that the spacetime outside the star is described by a Schwarzschild metric. First, the stellar structure equations are integrated employing the so-called causal limit equation of state (EOS), which is constructed using a well-established EOS at densities below a fiducial density, and the causal EOS P =ρ above it. It is a standard procedure in general relativistic stellar structure calculations to use such EOSs for obtaining a limit in the mass radius diagram, known as the causal limit, above which no stellar configurations are possible if the EOS fulfills the condition that the sound velocity is smaller than the speed of light. We find that the equilibrium solutions in the braneworld model can violate the general relativistic causal limit, and for sufficiently large mass they approach asymptotically to the Schwarzschild limit M =2 R . Then, we investigate the properties of hadronic and strange quark stars using two typical EOSs: a nonlinear relativistic mean-field model for hadronic matter and the Massachusetts Institute of Technology (MIT) bag model for quark matter. For masses below ˜1.5 M⊙- 2 M⊙ , the mass versus radius curves show the typical behavior found within the frame of general relativity. However, we also find a new branch of stellar configurations that can violate the general relativistic causal limit and that, in principle, may have an arbitrarily large mass. The stars belonging to this new branch are supported against collapse by the nonlocal effects of the bulk on the brane. We also show that these stars are always stable under small radial perturbations. These results support the idea that traces of extra dimensions might be found in astrophysics, specifically through the analysis of masses and
NASA Astrophysics Data System (ADS)
Mundhenk, T. Nathan; Flores, Arturo; Hoffman, Heiko
2013-12-01
3D reconstruction of objects via Shape from Motion (SFM) has made great strides recently. Utilizing images from a variety of poses, objects can be reconstructed in 3D without knowing a priori the camera pose. These feature points can then be bundled together to create large scale scene reconstructions automatically. A shortcoming of current methods of SFM reconstruction is in dealing with specular or flat low feature surfaces. The inability of SFM to handle these places creates holes in a 3D reconstruction. This can cause problems when the 3D reconstruction is used for proximity detection and collision avoidance by a space vehicle working around another space vehicle. As such, we would like the automatic ability to recognize when a hole in a 3D reconstruction is in fact not a hole, but is a place where reconstruction has failed. Once we know about such a location, methods can be used to try to either more vigorously fill in that region or to instruct a space vehicle to proceed with more caution around that area. Detecting such areas in earth orbiting objects is non-trivial since we need to parse out complex vehicle features from complex earth features, particularly when the observing vehicle is overhead the target vehicle. To do this, we have created a Space Object Classifier and Segmenter (SOCS) hole finder. The general principle we use is to classify image features into three categories (earth, man-made, space). Classified regions are then clustered into probabilistic regions which can then be segmented out. Our categorization method uses an augmentation of a state of the art bag of visual words method for object categorization. This method works by first extracting PHOW (dense SIFT like) features which are computed over an image and then quantized via KD Tree. The quantization results are then binned into histograms and results classified by the PEGASOS support vector machine solver. This gives a probability that a patch in the image corresponds to one of three
Reid, M. T. Homer; White, Jacob; Johnson, Steven G.
2011-07-15
We extend a recently introduced method for computing Casimir forces between arbitrarily shaped metallic objects [M. T. H. Reid et al., Phys. Rev. Lett. 103 040401 (2009)] to allow treatment of objects with arbitrary material properties, including imperfect conductors, dielectrics, and magnetic materials. Our original method considered electric currents on the surfaces of the interacting objects; the extended method considers both electric and magnetic surface current distributions, and obtains the Casimir energy of a configuration of objects in terms of the interactions of these effective surface currents. Using this new technique, we present the first predictions of Casimir interactions in several experimentally relevant geometries that would be difficult to treat with any existing method. In particular, we investigate Casimir interactions between dielectric nanodisks embedded in a dielectric fluid; we identify the threshold surface-surface separation at which finite-size effects become relevant, and we map the rotational energy landscape of bound nanoparticle diclusters.
NASA Astrophysics Data System (ADS)
Carlini, A.; Hosoya, A.
2001-02-01
Grover's quantum algorithm for an unstructured search problem and the COUNT algorithm by Brassard et al. are generalized to the case when the initial state is arbitrarily and maximally entangled. This ansatz might be relevant with quantum subroutines, when the computational qubits and the environment are coupled, and in general when the control over the quantum system is partial.
Lück, Ferdinand; Kolditz, Daniel; Hupfer, Martin; Steiding, Christian; Kalender, Willi A
2014-10-07
The purpose of this study was to validate the use of a single shaped filter (SF) for computed tomography (CT) using variable source-to-filter distance (SFD) for the examination of different object diameters.A SF was designed by performing simulations with the purpose of achieving noise homogeneity in the reconstructed volume and dose reduction for arbitrary phantom diameters. This was accomplished by using a filter design method thats target is to achieve a homogeneous detector noise, but also uses a correction factor for the filtered back projection process. According to simulation results, a single SF designed for one of the largest phantom diameters meets the requirements for all diameters when SFD can be adjusted. To validate these results, a SF made of aluminium alloy was manufactured. Measurements were performed on a CT scanner with polymethyl methacrylate (PMMA) phantoms of diameters from 40-100 mm. The filter was positioned at SFDs ranging from 97-168 mm depending on the phantom diameter. Image quality was evaluated for the reconstructed volume by assessing CT value accuracy, noise homogeneity, contrast-to-noise ratio weighted by dose (CNRD) and spatial resolution. Furthermore, scatter distribution was determined with the use of a beam-stop phantom. Dose was measured for a PMMA phantom with a diameter of 100 mm using a calibrated ionization chamber.The application of a single SF at variable SFD led to improved noise uniformity and dose reduction: noise homogeneity was improved from 15% down to about 0%, and dose was reduced by about 37%. Furthermore, scatter dropped by about 32%, which led to reduced cupping artifacts and improved CT value accuracy. Spatial resolution and CNRD was not affected by the SF.By means of a single SF with variable SFD designed for CT, significant dose reduction can be achieved and image quality can be improved by reducing noise inhomogeneity as well as scatter-induced artifacts.
Ray Scattering by an Arbitrarily Oriented Spheroid: 2. Transmission and Cross-polarization Effects
NASA Technical Reports Server (NTRS)
Lock, James A.
1996-01-01
Transmission of an arbitrarily polarized plane wave by an arbitrarily oriented spheroid in the short-wavelength limit is considered in the context of ray theory. The transmitted electric field is added to the diffracted plus reflected ray-theory electric field that was previously derived to obtain an approximation to the far-zone scattered intensity in the forward hemisphere. Two different types of cross-polarization effects are found. These are: (a) a rotation of the polarization state of the transmitted rays from when they are referenced with respect to their entrance into the spheroid to when they are referenced with respect to their exit from it and (b) a rotation of the polarization state of the transmitted rays when they are referenced with respect to the polarization state of the diffracted plus reflected rays.
A novel synthesis approach for birefringent filters having arbitrarily amplitude transmittances
NASA Astrophysics Data System (ADS)
Halassi, Abde Rezzaq; Hamdi, Rachid; Bendimerad, Djalal Falih; Benkelfat, Badr-Eddine
2016-06-01
In this paper, we present a novel procedure for the synthesis of a filter having an arbitrarily specified amplitude transmittance. The filter configuration consists of N birefringent stages placed between a polarizer and an analyzer, with each stage containing an identical section and a variable section. An additional variable section is placed in front of the analyzer. The synthesis procedure is based on the resolution of a generalized nonlinear equation system directly deducted from the Jones matrix formalism to determine the angles of each stage, the angle of the analyzer and the phase shifts of the variable sections. A typical example of a 6-stage birefringent filter having an arbitrarily non-symmetric amplitude transmittance is shown and the opto-geometrical parameters are given to demonstrate the efficiency of the proposed synthesis procedure. The results obtained show an excellent agreement with those developed in the literature.
1984-10-01
and second Fr~ chet derivatives of 3(v) 1 n L(v) are given by (Tapia, 1971) n d I n(xi) n (1- d )I X I iv MxZ) ’-t)dt -2 < v,rn and n d 2. (X-n j~i (v)i...8217 first APLE; SurvivaZ e.t..a- tion; Random censor-hip; Nonparaet"c density estimation; Reliability. AB STRACT D Based on arbitrarily right-censored...functional 0: H(n) -I R. Given the arbitrarily right-censored sample (xi,dt), i11,2,... ,n, the #-penalized likelihood of v c H(n) is defined by %I n d
Doughty, Michael J
2011-07-01
To objectively assess the cell and nucleus dimensions of human bulbar conjunctival cells in female soft contact lens wearers to illustrate a method for assessment of the nucleus-to-cytoplasm ratio based on simple linear measures. Impression cytology samples were taken from the nasal side exposed bulbar conjunctiva surface from 12 young adult, white European females with a history of successful daily soft contact lens wear. A Millcell(®)-CM filter was used after topical anesthesia, which was stained with Giemsa. Color images of portions of the cells, in a monolayer at 200× magnification by light microscopy, were graded by the Nelson scale and then a projection overlay method was used to outline the cell and nucleus borders. The cell longest dimension (LONG), shorter dimension (SHORT), and the longest dimension of the nucleus (NUCLONG) were measured. A nucleus-to-cytoplasm N:C ratio was calculated from (LONG-NUCLONG)/NUCLONG. Cells had appearances consistent with a grade 2 or 3 squamous metaplasia and were moderately enlarged (mean LONG ± SD of 46.0 ± 3.8 microm), only slightly elongated (mean LONG:SHORT ratio of 1.397 ± 0.101) and the nucleus size was consistently greater than normal (man 12.8 ± 1.3 microm). A calculation of N:C showed a relatively wide range of values with average values from 1:2.143 to 1:3.317 (for an overall mean of 2.675 ± 0.371). These studies further indicate that grade 2 to 3 squamous metaplasia of the exposed bulbar conjunctival cells is an expected consequence of soft contact lens wear. The cell enlargement is not associated with a significant change in cell shape (i.e., the LONG:SHORT ratio is little different from grade 0 cells) but is associated in a slight increase in nucleus size. The calculated N:C ratio based on linear measures is no higher than 1:5 and more likely closer to 1:2.5.
NASA Astrophysics Data System (ADS)
Mitri, F. G.
2014-03-01
The axial and transverse radiation forces on a fluid sphere placed arbitrarily in the acoustical field of Bessel beams of standing waves are evaluated. The three-dimensional components of the time-averaged force are expressed in terms of the beam-shape coefficients of the incident field and the scattering coefficients of the fluid sphere using a partial-wave expansion (PWE) method. Examples are chosen for which the standing wave field is composed of either a zero-order (non-vortex) Bessel beam, or a first-order Bessel vortex beam. It is shown here, that both transverse and axial forces can push or pull the fluid sphere to an equilibrium position depending on the chosen size parameter ka (where k is the wave-number and a the sphere's radius). The corresponding results are of particular importance in biophysical applications for the design of lab-on-chip devices operating with Bessel beams standing wave tweezers. Moreover, potential investigations in acoustic levitation and related applications in particle rotation in a vortex beam may benefit from the results of this study.
Mitri, F.G.
2014-03-15
The axial and transverse radiation forces on a fluid sphere placed arbitrarily in the acoustical field of Bessel beams of standing waves are evaluated. The three-dimensional components of the time-averaged force are expressed in terms of the beam-shape coefficients of the incident field and the scattering coefficients of the fluid sphere using a partial-wave expansion (PWE) method. Examples are chosen for which the standing wave field is composed of either a zero-order (non-vortex) Bessel beam, or a first-order Bessel vortex beam. It is shown here, that both transverse and axial forces can push or pull the fluid sphere to an equilibrium position depending on the chosen size parameter ka (where k is the wave-number and a the sphere’s radius). The corresponding results are of particular importance in biophysical applications for the design of lab-on-chip devices operating with Bessel beams standing wave tweezers. Moreover, potential investigations in acoustic levitation and related applications in particle rotation in a vortex beam may benefit from the results of this study. -- Highlights: •The axial and transverse forces on a fluid sphere in acoustical Bessel beams tweezers are evaluated. •The attraction or repulsion to an equilibrium position in the standing wave field is examined. •Potential applications are in particle manipulation using standing waves.
Solving the two-center nuclear shell-model problem with arbitrarily oriented deformed potentials.
Diaz-Torres, Alexis
2008-09-19
A general new technique to solve the two-center problem with arbitrarily oriented deformed realistic potentials is demonstrated, which is based on the powerful potential separable expansion method. As an example, molecular single-particle spectra for (12)C+(12)C-->(24)Mg are calculated using deformed Woods-Saxon potentials. These clearly show that nonaxial symmetric configurations play a crucial role in molecular resonances observed in reaction processes for this system at low energy.
NASA Astrophysics Data System (ADS)
Na, Seong-Won; Kallivokas, Loukas F.
2008-03-01
In this article we discuss a formal framework for casting the inverse problem of detecting the location and shape of an insonified scatterer embedded within a two-dimensional homogeneous acoustic host, in terms of a partial-differential-equation-constrained optimization approach. We seek to satisfy the ensuing Karush-Kuhn-Tucker first-order optimality conditions using boundary integral equations. The treatment of evolving boundary shapes, which arise naturally during the search for the true shape, resides on the use of total derivatives, borrowing from recent work by Bonnet and Guzina [1-4] in elastodynamics. We consider incomplete information collected at stations sparsely spaced at the assumed obstacle’s backscattered region. To improve on the ability of the optimizer to arrive at the global optimum we: (a) favor an amplitude-based misfit functional; and (b) iterate over both the frequency- and wave-direction spaces through a sequence of problems. We report numerical results for sound-hard objects with shapes ranging from circles, to penny- and kite-shaped, including obstacles with arbitrarily shaped non-convex boundaries.
Noh, Heung-Ryoul; Moon, Han Seb
2010-09-15
This paper reports a theoretical study on the transmission spectra of an arbitrarily polarized laser beam through a rubidium cell with or without a buffer gas in Hanle-type coherent population trapping (CPT). This study examined how laser polarization, transverse magnetic field, and collisions with buffer gas affects the spectrum. The transmission spectrum due to CPT and the absorption spectrum due to the level crossing absorption (LCA) were calculated according to the laser polarization. The results show that the LCA is strongly dependent on the transverse magnetic field and interaction time of the atoms with a laser light via collisions with the buffer gas. In addition, the spectral shape of the calculated Hanle spectrum is closely related to the direction between the (stray) transverse magnetic field and polarization of the laser.
R. M. Ferrer; Y. Y. Azmy
2009-05-01
We present a robust arbitrarily high order transport method of the characteristic type for unstructured tetrahedral grids. Previously encountered difficulties have been addressed through the reformulation of the method based on coordinate transformations, evaluation of the moments balance relation as a linear system of equations involving the expansion coefficients of the projected basis, and the asymptotic expansion of the integral kernels in the thin cell limit. The proper choice of basis functions for the high-order spatial expansion of the solution is discussed and its effect on problems involving scattering discussed. Numerical tests are presented to illustrate the beneficial effect of these improvements, and the improved robustness they yield.
NASA Astrophysics Data System (ADS)
Zhenfeng, Niu; Wenbiao, Liu
2006-07-01
After a new tortoise coordinate transformation is adopted, the entropy and non-thermal radiation of an arbitrarily accelerating charged black hole are discussed as an example of non-stationary black holes. The same cut-off relation is chosen as static case, which is independent of space-time, and then the entropy of the non-stationary black hole is also proportional to the area of its event horizon. Meanwhile, the crossing of the particle energy levels near the event horizon is studied, the representative of the maximum value of the crossing energy levels is the same as the usual tortoise coordinate transformation.
NASA Astrophysics Data System (ADS)
Heitz, Eric
2017-04-01
We present a geometric method for computing an ellipse that subtends the same solid-angle domain as an arbitrarily positioned ellipsoid. With this method we can extend existing analytical solid-angle calculations of ellipses to ellipsoids. Our idea consists of applying a linear transformation on the ellipsoid such that it is transformed into a sphere from which a disk that covers the same solid-angle domain can be computed. We demonstrate that by applying the inverse linear transformation on this disk we obtain an ellipse that subtends the same solid-angle domain as the ellipsoid. We provide a MATLAB implementation of our algorithm and we validate it numerically.
A half plane and a strip with an arbitrarily located crack
NASA Technical Reports Server (NTRS)
Erdogan, F.; Arin, K.
1973-01-01
A technique is presented for dealing with the problem of an elastic domain containing an arbitrarily oriented internal crack. The problem is formulated as a system of integral equations for a fictitious layer of body forces imbedded in the plane along a closed smooth curve encircling the original domain. The problems of a half plane with a crack in the neighborhood of its free boundary and of an infinite strip containing a symmetrically located internal crack with an arbitrary orientation are considered as examples. In each case the stress intensity factors are computed and are given as functions of the crack angle.
NASA Astrophysics Data System (ADS)
Nötzel, J.
2014-06-01
We report a proof of the quantum Sanov theorem by the elementary application of basic facts about representations of the symmetric group, together with a complete characterization of the optimal error exponent in a situation where the null hypothesis is given by an arbitrarily varying quantum source instead. Our approach differs from previous ones in two ways. First, it supports a reasoning inspired by the ‘method of types’. Second, the measurement scheme we propose to distinguish the two alternatives not only does that job asymptotically perfectly, but also yields additional information about the null hypothesis. An example of that is given. The measurement is composed of projections onto permutation-invariant subspaces, thus providing a direct link between one of the most basic tasks in quantum information on the one hand and fundamental objects in representation theory on the other. We additionally connect to the representation theory by proving a relation between Kostka numbers and quantum states, and to state estimation via a generalization of a well-known spectral estimation theorem to non-i.i.d. sequences.
NASA Astrophysics Data System (ADS)
Angeli, D.; Stalio, E.; Corticelli, M. A.; Barozzi, G. S.
2015-11-01
A parallel algorithm is presented for the Direct Numerical Simulation of buoyancy- induced flows in open or partially confined periodic domains, containing immersed cylindrical bodies of arbitrary cross-section. The governing equations are discretized by means of the Finite Volume method on Cartesian grids. A semi-implicit scheme is employed for the diffusive terms, which are treated implicitly on the periodic plane and explicitly along the homogeneous direction, while all convective terms are explicit, via the second-order Adams-Bashfort scheme. The contemporary solution of velocity and pressure fields is achieved by means of a projection method. The numerical resolution of the set of linear equations resulting from discretization is carried out by means of efficient and highly parallel direct solvers. Verification and validation of the numerical procedure is reported in the paper, for the case of flow around an array of heated cylindrical rods arranged in a square lattice. Grid independence is assessed in laminar flow conditions, and DNS results in turbulent conditions are presented for two different grids and compared to available literature data, thus confirming the favorable qualities of the method.
NASA Astrophysics Data System (ADS)
Nakamura, Ryosuke
2017-01-01
Numerical simulations demonstrate that mid-infrared pulses are arbitrarily shaped during the differential frequency mixing of two femtosecond near-infrared pulses propagating in an engineered quasi-periodic poled medium with optical nonlinearity and group velocity dispersion. Shaped pulses, including linearly chirped pulses and pulse trains, are generated with high conversion efficiencies.
NASA Astrophysics Data System (ADS)
Zhang, Lijuan; Li, Yuhao; Zhou, Yunshan
2010-04-01
The reaction of an aqueous solution of sodium molybdate with L-tyrosine in the presence of reducing agent results in the formation of a new compound of the formula of Na 8Co 3[Mo VI126 Mo V28O 462H 14(H 2O) 46(HOC 6H 4CH 2CH( NH3+)COO -) 12]·ca. 200H 2O. The compound contains nanosized ring-shaped clusters with tyrosine ligands possessing different types of functional groups (one -CO 2, one -NH3+ and one -ArOH) coordinated through the carboxylate groups at the active sites of the inner cavity. Importantly, the result demonstrates that not only active sites/areas of the cluster surface under a specified condition can be directly monitored and detected but also novel type surfaces within the cavity of a nano-structured ring-shaped cluster can be generated simultaneously. The nonlinear optical properties of the new cluster are studied using the well-known Z-scan technique at a wavelength of 532 nm with laser pulse duration of 18 ps. The results show that the new cluster exhibits interesting self-focusing nonlinear optical response with the real and imaginary parts of the third-order nonlinear optical susceptibility χ(3) being 1.069 × 10 -13(esu) and 2.529 × 10 -15(esu), respectively, which may find application in material science.
Sainath, Kamalesh; Teixeira, Fernando L; Donderici, Burkay
2014-01-01
We develop a general-purpose formulation, based on two-dimensional spectral integrals, for computing electromagnetic fields produced by arbitrarily oriented dipoles in planar-stratified environments, where each layer may exhibit arbitrary and independent anisotropy in both its (complex) permittivity and permeability tensors. Among the salient features of our formulation are (i) computation of eigenmodes (characteristic plane waves) supported in arbitrarily anisotropic media in a numerically robust fashion, (ii) implementation of an hp-adaptive refinement for the numerical integration to evaluate the radiation and weakly evanescent spectra contributions, and (iii) development of an adaptive extension of an integral convergence acceleration technique to compute the strongly evanescent spectrum contribution. While other semianalytic techniques exist to solve this problem, none have full applicability to media exhibiting arbitrary double anisotropies in each layer, where one must account for the whole range of possible phenomena (e.g., mode coupling at interfaces and nonreciprocal mode propagation). Brute-force numerical methods can tackle this problem but only at a much higher computational cost. The present formulation provides an efficient and robust technique for field computation in arbitrary planar-stratified environments. We demonstrate the formulation for a number of problems related to geophysical exploration.
Arbitrarily Accessible 3D Microfluidic Device for Combinatorial High-Throughput Drug Screening
Chen, Zhuofa; Li, Weizhi; Choi, Gihoon; Yang, Xiaonan; Miao, Jun; Cui, Liwang; Guan, Weihua
2016-01-01
Microfluidics-based drug-screening systems have enabled efficient and high-throughput drug screening, but their routine uses in ordinary labs are limited due to the complexity involved in device fabrication and system setup. In this work, we report an easy-to-use and low-cost arbitrarily accessible 3D microfluidic device that can be easily adopted by various labs to perform combinatorial assays for high-throughput drug screening. The device is capable of precisely performing automatic and simultaneous reagent loading and aliquoting tasks and performing multistep assays with arbitrary sequences. The device is not intended to compete with other microfluidic technologies regarding ultra-low reaction volume. Instead, its freedom from tubing or pumping systems and easy operation makes it an ideal platform for routine high-throughput drug screening outside traditional microfluidic labs. The functionality and quantitative reliability of the 3D microfluidic device were demonstrated with a histone acetyltransferase-based drug-screening assay using the recombinant Plasmodium falciparum GCN5 enzyme, benchmarked with a traditional microtiter plate-based method. This arbitrarily accessible, multistep capable, low-cost, and easy-to-use device can be widely adopted in various combinatorial assays beyond high-throughput drug screening. PMID:27690055
NASA Technical Reports Server (NTRS)
Long, S. A. T.
1974-01-01
Formulas are derived for the root-mean-square (rms) displacement, slope, and curvature errors in an azimuth-elevation image trace of an elongated object in space, as functions of the number and spacing of the input data points and the rms elevation error in the individual input data points from a single observation station. Also, formulas are derived for the total rms displacement, slope, and curvature error vectors in the triangulation solution of an elongated object in space due to the rms displacement, slope, and curvature errors, respectively, in the azimuth-elevation image traces from different observation stations. The total rms displacement, slope, and curvature error vectors provide useful measure numbers for determining the relative merits of two or more different triangulation procedures applicable to elongated objects in space.
Visualization: a really generic approach or the art of mapping data to graphical objects
NASA Astrophysics Data System (ADS)
Trilk, Joern; Schuetz, Frank
1998-05-01
Visualization is an important technology for analyzing large amounts of data. However, the process of creating meaningful visualizations is quite difficult. The success of this process depends heavily on a good mapping of objects present in the application domain to objects used in the graphical representation. Both kinds of objects possess several attributes. Whereas data objects have attributes of certain types (e.g. integers, strings) graphical objects are characterized by their appearance (shape, color, size, etc.). In our approach, the user may map arbitrarily data attributes to graphical attributes, leading to a great flexibility. In our opinion, this is the only possibility to achieve a really generic approach. To evaluate our ideas, we developed a tool called ProViS. This tool indicates the possible attributes of data objects as well as graphical objects. Depending on his goals, the user can then 'connect' (freely) attributes of data objects to attributes of their graphical counterparts. The structure behind the application objects can be worked out very easily with the help of various layout algorithms. In addition, we integrated several mechanisms (e.g. ghosting, hiding, grouping, fisheye views) to reduce complexity and to further enhance the three-dimensional visualization. In this paper, first of all we take a look at the basic principle of visualization: mapping data. Then we present, ProViS, a visualization tool implementing our idea of mapping.
An arbitrary-shaped acoustic cloak with merits beyond the internal and external cloaks
NASA Astrophysics Data System (ADS)
Li, Baolei; Li, Tinghua; Wu, Jun; Hui, Ming; Yuan, Gang; Zhu, Yongsheng
2017-01-01
Based on transformation acoustics, an arbitrary-shaped acoustic cloak capable of functioning as an information exchange-enabling internal cloak and a movement-allowing external cloak is presented. The general expressions of material parameters for the acoustic cloaks with arbitrarily conformal or non-conformal boundaries are derived, and then the performances of developed cloaks are validated by full-wave simulations. Finally, the different characteristics of the linear and nonlinear transformations-based cloaks are compared and analyzed. The proposed cloak could lead to wider applications beyond that of normal cloaks, since it effectively compensates the insufficiencies of traditional internal and external cloaks. Besides, this work also provides a new method to design bifunctional device and suggests an alternative way to make a large object invisible.
Object Oriented Learning Objects
ERIC Educational Resources Information Center
Morris, Ed
2005-01-01
We apply the object oriented software engineering (OOSE) design methodology for software objects (SOs) to learning objects (LOs). OOSE extends and refines design principles for authoring dynamic reusable LOs. Our learning object class (LOC) is a template from which individualised LOs can be dynamically created for, or by, students. The properties…
Object Oriented Learning Objects
ERIC Educational Resources Information Center
Morris, Ed
2005-01-01
We apply the object oriented software engineering (OOSE) design methodology for software objects (SOs) to learning objects (LOs). OOSE extends and refines design principles for authoring dynamic reusable LOs. Our learning object class (LOC) is a template from which individualised LOs can be dynamically created for, or by, students. The properties…
A new cut-cell algorithm for DSMC simulations of rarefied gas flows around immersed moving objects
NASA Astrophysics Data System (ADS)
Jin, Wenjie; Ommen, J. Ruud van; Kleijn, Chris R.
2017-03-01
Direct Simulation Monte Carlo (DSMC) is a widely applied numerical technique to simulate rarefied gas flows. For flows around immersed moving objects, the use of body fitted meshes is inefficient, whereas published methods using cut-cells in a fixed background mesh have important limitations. We present a novel cut-cell algorithm, which allows for accurate DSMC simulations around arbitrarily shaped moving objects. The molecule-surface interaction occurs exactly at the instantaneous collision point on the moving body surface, and accounts for its instantaneous velocity, thus precisely imposing the desired boundary conditions. A simple algorithm to calculate the effective volume of cut cells is presented and shown to converge linearly with grid refinement. The potential and efficiency of method is demonstrated by calculating rarefied gas flow drag forces on steady and moving immersed spheres. The obtained results are in excellent agreement with results obtained with a body-fitted mesh, and with analytical approximations for high-Knudsen number flows.
Cut set-based risk and reliability analysis for arbitrarily interconnected networks
Wyss, Gregory D.
2000-01-01
Method for computing all-terminal reliability for arbitrarily interconnected networks such as the United States public switched telephone network. The method includes an efficient search algorithm to generate minimal cut sets for nonhierarchical networks directly from the network connectivity diagram. Efficiency of the search algorithm stems in part from its basis on only link failures. The method also includes a novel quantification scheme that likewise reduces computational effort associated with assessing network reliability based on traditional risk importance measures. Vast reductions in computational effort are realized since combinatorial expansion and subsequent Boolean reduction steps are eliminated through analysis of network segmentations using a technique of assuming node failures to occur on only one side of a break in the network, and repeating the technique for all minimal cut sets generated with the search algorithm. The method functions equally well for planar and non-planar networks.
Subtyping of Legionella pneumophila isolates by arbitrarily primed polymerase chain reaction.
Ledesma, E; Camaró, M L; Carbonell, E; Sacristán, T; Martí, A; Pellicer, S; Llorca, J; Herrero, P; Dasí, M A
1995-09-01
Arbitrarily primed polymerase chain reaction (AP-PCR) was used to differentiate strains of Legionella pneumophila isolated from different water sources in a resort hotel in Benidorm, Alicante, Spain, where an outbreak of Legionnaires' disease occurred among a group of tourists between 65 and 80 years of age. All isolates were L. pneumophila serogroup 1, subtype Pontiac (Knoxville 1). Five different patterns (P1 to P5) were obtained by AP-PCR. The number of bands per pattern varied between 4 and 11. Patterns P1 and P2 represented 60 and 20% of L. pneumophila isolates, respectively. Since different subpopulations of L. pneumophila coexisted (up to three different AP-PCR patterns were identified in a single room), it was not possible to link an individual L. pneumophila strain to the occurrence of this outbreak.
Van Der Knaap, Esther; Rodriguez, Russell J.; Freckman, Diana W.
1993-01-01
Arbitrarily-primed polymerase chain reaction (ap-PCR) was used to differentiate closely related bacterial-feeding nematodes of the genera: Caenorhabditis, Acrobeloides, Cephalobus and Zeldia. Average percentage similarity of bands generated by ap-PCR with seven different primers between 14 isolates of Caenorhabditis elegans was ⪢ 90%, whereas between C. elegans, C. briggsae and C. remanei similarity was < 20%. Based on intra- and inter-specific similarity between Caenorhabditis isolates, analysis of Acrobeloides, Cephalobus and Zeldia isolates revealed either similar or different genotypes. Distinct genotypes were verified by morphological analyses. In addition, the genotypes obtained from single egg-derived nematode populations were also obtained from ap-PCR analysis of single worms. Due to the difficulty of identification of soil nematodes, the ap-PCR offers potential as a rapid and reliable technique to assess biodiversity. Ap-PCR will make it feasible, for the first time, to study the ecological interactions of unique nematode genotypes in soil habitats.
Hennessy, K J; Iandolo, J J; Fenwick, B W
1993-01-01
Rapid and accurate determination of the Actinobacillus pleuropneumoniae serotype involved in a disease outbreak is important both in limiting the severity of an outbreak and for tracing the source of the infecting organism. This study describes the use of arbitrarily primed polymerase chain reaction (AP-PCR) as a rapid, precise, and genetically based procedure to identify A. pleuropneumoniae. AP-PCR amplification of bacterial genomic DNA results in specific DNA profiles, which can be used to differentiate currently recognized serotypes. This technique is especially useful for identifying previously nontypeable and serologically cross-reactive A. pleuropneumoniae field isolates. Consecutive passages of isolates on different media, freezing, and subsequent infection of pigs did not alter the AP-PCR genomic profile. We propose the use of M13 and T3-T7 oligodeoxynucleotide primers for diagnostic and epidemiological identification of A. pleuropneumoniae by AP-PCR techniques. Images PMID:8501215
Multiple scattering of arbitrarily incident Bessel beams by random discrete particles.
Cui, Zhiwei; Han, Yiping; Ai, Xia
2013-11-01
In this paper, we introduce an efficient numerical method to characterize the multiple scattering by random discrete particles illuminated by Bessel beams with arbitrary incidence. Specifically, the vector expressions of Bessel beams that perfectly satisfy Maxwell's equations in combination with rotation Euler angles are used to represent the arbitrarily incident Bessel beams. A hybrid vector finite element-boundary integral-characteristic-basis function method is utilized to formulate the scattering problems involving multiple discrete particles with a random distribution. Due to the flexibility of the finite element method, the adopted method can conveniently deal with the problems of multiple scattering by randomly distributed homogeneous particles, inhomogeneous particles, and anisotropic particles. Some numerical results are included to illustrate the validity and capability of the proposed method and to show the scattering behaviors of random discrete particles when they are illuminated by Bessel beams.
Prediction of Debye-Scherrer diffraction patterns in arbitrarily strained samples
Higginbotham, Andrew; McGonegle, David
2014-05-07
The prediction of Debye-Scherrer diffraction patterns from strained samples is typically conducted in the small strain limit. Although valid for small deviations from the hydrostat (such as the conditions of finite strength typically observed in diamond anvil cells) this assertion is likely to fail for the large strain anisotropies (often of order 10% in normal strain) found in uniaxially loaded dynamic compression experiments. In this paper, we derive a general form for the (θ{sub B},ϕ) dependence of the diffraction for an arbitrarily deformed polycrystalline sample in any geometry, and of any crystal symmetry. We show that this formula is consistent with ray traced diffraction for highly strained computationally generated polycrystals, and that the formula shows deviations from the widely used small strain solutions previously reported.
Markson, Lori; Diesendruck, Gil; Bloom, Paul
2008-03-01
When children learn the name of a novel object, they tend to extend that name to other objects similar in shape - a phenomenon referred to as the shape bias. Does the shape bias stem from learned associations between names and categories of objects, or does it derive from more general properties of children's understanding of language and the world? We argue here for the second alternative, presenting evidence that the shape bias emerges early in development, is not limited to names, and is intimately related to how children make sense of categories.
Synthetic generation of arbitrarily long series of flood hydrographs for flood risk assessment
NASA Astrophysics Data System (ADS)
Flores, Isabel; Sordo-Ward, Alvaro; Mediero, Luis; Garrote, Luis
2013-04-01
Flood risk assessment is an essential component of natural disaster management. Flood frequency analysis has traditionally been approached by fitting relatively short series of annual maxima of observations to a parametric probability distribution. Under this approach, only one relevant variable (usually peak discharge) can be analyzed, while in many practical applications, like dam safety analysis, the entire flood hydrograph is of interest. Obtaining a good representation of the ensemble of hydrographs would require extremely long historical flood series which almost never exist. Hydrometeorological modelling tools can be applied to extend the relatively short series of observations and generate an arbitrarily long series of synthetic events that can be used in flood risk assessment. The heavy computational burden of these processes requires the contribution of Information and Communication Technology (ICT) developments to enable the practical application of the hydrometeorological modelling chain for this purpose. In this paper, an example of this methodology is applied to the Santillana reservoir, located in the Manzanares basin, in Spain. The methodology is based on the Monte Carlo generation of synthetic hydrographs from rainstorms events extracted from arbitrarily long synthetic rainfall time series. The rainfall series are generated with the RainSim software, a model based on a spatial-temporal Neyman-Scott rectangular pulses process. The highest event of every year is chosen, based on three different criterions. The selected rainstorm events are transformed into runoff by the RIBS distributed rainfall-runoff event model, obtaining the ensemble of hydrographs which make possible to evaluate the associated flood risk. The procedure has been validated by comparing the observed flood frequency series in the Santillana reservoir with the synthetic ones, obtaining a good agreement.
Fischer, Stefan; Hartl, Caroline; Frank, Kilian; Rädler, Joachim O; Liedl, Tim; Nickel, Bert
2016-07-13
Scaffolded DNA origami nanostructures enable the self-assembly of arbitrarily shaped objects with unprecedented accuracy. Yet, varying physiological conditions are prone to induce slight structural changes in the nanoscale architecture. Here, we report on high precision measurements of overall shape and interhelical distance of three prototypic DNA origami structures in solution using synchrotron small-angle X-ray scattering. Sheet-, brick-, and cylinder-shaped DNA constructs were assembled and the shape factors determined with angstrom resolution from fits to the scattering profiles. With decreasing MgCl2 concentration electrostatic swelling of both shape cross section and interhelical DNA spacing of the DNA origami structures is observed. The structures tolerate up to 10% interhelical expansion before they disintegrate. In contrast, with increasing temperature, the cylinder-shaped structures show no thermal expansion in a wide temperature window before they abruptly melt above 50 °C. Details on molecular structure of DNA origami can also be obtained using in-house X-ray scattering equipment and, hence, allow for routine folding and stability testing of DNA-based agents that are designed to operate under varying salt conditions.
Kaur, Jaspreet; Nygren, Anders; Vigmond, Edward J
2014-01-01
Fitting parameter sets of non-linear equations in cardiac single cell ionic models to reproduce experimental behavior is a time consuming process. The standard procedure is to adjust maximum channel conductances in ionic models to reproduce action potentials (APs) recorded in isolated cells. However, vastly different sets of parameters can produce similar APs. Furthermore, even with an excellent AP match in case of single cell, tissue behaviour may be very different. We hypothesize that this uncertainty can be reduced by additionally fitting membrane resistance (Rm). To investigate the importance of Rm, we developed a genetic algorithm approach which incorporated Rm data calculated at a few points in the cycle, in addition to AP morphology. Performance was compared to a genetic algorithm using only AP morphology data. The optimal parameter sets and goodness of fit as computed by the different methods were compared. First, we fit an ionic model to itself, starting from a random parameter set. Next, we fit the AP of one ionic model to that of another. Finally, we fit an ionic model to experimentally recorded rabbit action potentials. Adding the extra objective (Rm, at a few voltages) to the AP fit, lead to much better convergence. Typically, a smaller MSE (mean square error, defined as the average of the squared error between the target AP and AP that is to be fitted) was achieved in one fifth of the number of generations compared to using only AP data. Importantly, the variability in fit parameters was also greatly reduced, with many parameters showing an order of magnitude decrease in variability. Adding Rm to the objective function improves the robustness of fitting, better preserving tissue level behavior, and should be incorporated.
Method and System for Object Recognition Search
NASA Technical Reports Server (NTRS)
Duong, Tuan A. (Inventor); Duong, Vu A. (Inventor); Stubberud, Allen R. (Inventor)
2012-01-01
A method for object recognition using shape and color features of the object to be recognized. An adaptive architecture is used to recognize and adapt the shape and color features for moving objects to enable object recognition.
NASA Technical Reports Server (NTRS)
Ranganath, H. S.; Mcingvale, Pat; Sage, Heinz
1988-01-01
Geometric and intensity features are very useful in object recognition. An intensity feature is a measure of contrast between object pixels and background pixels. Geometric features provide shape and size information. A model based approach is presented for computing geometric features. Knowledge about objects and imaging system is used to estimate orientation of objects with respect to the line of sight.
2008-02-15
penicillin -susceptible and peni- cillin-resistant Streptococcnspneuttmoniae serotypes in Canada. J Infect Dis Streptococcus pneumoniae Surveillance Group...Gray for the Streptococcus pneumonia Surveillance Group Report No. 00-44 Approved for public release; distribution unlimited. NAVAL HEALTH RESEARCH...Defense Surveillance for Invasive Streptococcus pneumoniae : Antibiotic Resistance, Serotype Distribution, and Arbitrarily Primed Polymerase Chain
Visual hull method for tomographic PIV of flow around moving objects
NASA Astrophysics Data System (ADS)
Adhikari, Deepak; Longmire, Ellen
2011-11-01
Measurement of velocity around arbitrarily moving objects is of interest in many applications. This includes flow around marine animals and flying insects, flow around supercavitating projectiles, and flow around discrete drops or particles in multiphase flows. We present a visual hull technique that employs existing tomographic PIV reconstruction software to automate identification, masking and tracking of discrete objects within a three-dimensional volume, while allowing computation and avoiding contamination of the surrounding three-component fluid velocity vectors. The technique is demonstrated by considering flow around falling objects of different shape, namely a sphere, cube, tetrahedron and cylinder. Four high-speed cameras and a laser are used to acquire images of these objects falling within liquid seeded with tracer particles. The acquired image sets are then processed to reconstruct both the object and the surrounding tracer particles. The reconstructed object is used to estimate the object location at each time step and mask the reconstructed particle volume, while the reconstructed tracer particles are cross-correlated with subsequent particle volumes to obtain the fluid velocity vectors. Supported by NSF IDBR Grant #0852875.
Koenderink, Jan; van Doorn, Andrea
2015-01-01
Local solid shape applies to the surface curvature of small surface patches—essentially regions of approximately constant curvatures—of volumetric objects that are smooth volumetric regions in Euclidean 3-space. This should be distinguished from local shape in pictorial space. The difference is categorical. Although local solid shape has naturally been explored in haptics, results in vision are not forthcoming. We describe a simple experiment in which observers judge shape quality and magnitude of cinematographic presentations. Without prior training, observers readily use continuous shape index and Casorati curvature scales with reasonable resolution. PMID:27648217
Boche, H. E-mail: janis.noetzel@tum.de; Nötzel, J. E-mail: janis.noetzel@tum.de
2014-12-15
This work is motivated by a quite general question: Under which circumstances are the capacities of information transmission systems continuous? The research is explicitly carried out on finite arbitrarily varying quantum channels (AVQCs). We give an explicit example that answers the recent question whether the transmission of messages over AVQCs can benefit from assistance by distribution of randomness between the legitimate sender and receiver in the affirmative. The specific class of channels introduced in that example is then extended to show that the unassisted capacity does have discontinuity points, while it is known that the randomness-assisted capacity is always continuous in the channel. We characterize the discontinuity points and prove that the unassisted capacity is always continuous around its positivity points. After having established shared randomness as an important resource, we quantify the interplay between the distribution of finite amounts of randomness between the legitimate sender and receiver, the (nonzero) probability of a decoding error with respect to the average error criterion and the number of messages that can be sent over a finite number of channel uses. We relate our results to the entanglement transmission capacities of finite AVQCs, where the role of shared randomness is not yet well understood, and give a new sufficient criterion for the entanglement transmission capacity with randomness assistance to vanish.
Scarpa, A; Taruscio, D; Scardoni, M; Iosi, F; Paradisi, S; Ennas, M G; Rigaud, G; Moore, P S; Menestrina, F
1999-11-01
We used arbitrarily primed polymerase chain reaction (AP-PCR) fingerprinting to identify chromosomal imbalances in six primary mediastinal B-cell lymphomas (PMBLs). Seventy-four chromosomal imbalances were detected, consisting of 49 sequence gains and 25 losses. Amplifications on chromosome X were seen in five cases, four of which involved the same chromosomal locus. Nonrandom gains at the same locus were also identified on chromosomes 2 and 7 in four cases and on chromosomes 5, 9, and 12 in three cases. Five PMBLs were also analyzed by comparative genomic hybridization (CGH), which found chromosome arm 9p amplification as the only nonrandom imbalance. Our data demonstrate that chromosomal amplifications outnumber losses in PMBL. These mainly involve chromosomes 9 and X and may reflect more complex phenomena, such as translocations or other chromosomal rearrangements, as AP-PCR found coexistent gains and losses on these chromosomes. Comparison between AP-PCR and CGH suggests that anomalies affecting the same chromosomal regions may occur at much higher frequencies than expected by CGH, suggesting that genomic amplifications are usually confined to DNA segments smaller than the megabase long segments required for detection in CGH. Modest increases in genetic material may be as effective as higher-level amplifications when affecting sites where a proto-oncogene resides. Copyright 1999 Wiley-Liss, Inc.
Start-up of electrophoresis of an arbitrarily oriented dielectric cylinder.
Chen, Guan Y; Keh, Huan J
2014-09-01
An analytical study is presented for the transient electrophoretic response of a circular cylindrical particle to the step application of an electric field. The electric double layer adjacent to the particle surface is thin but finite compared with the radius of the particle. The time-evolving electroosmotic velocity at the outer boundary of the double layer is utilized as a slip condition so that the transient momentum conservation equation for the bulk fluid flow is solved. Explicit formulas for the unsteady electrophoretic velocity of the particle are obtained for both axially and transversely applied electric fields, and can be linearly superimposed for an arbitrarily-oriented applied field. If the cylindrical particle is neutrally buoyant in the suspending fluid, the transient electrophoretic velocity is independent of the orientation of the particle relative to the applied electric field and will be in the direction of the applied field. If the particle is different in density from the fluid, then the direction of electrophoresis will not coincide with that of the applied field until the steady state is attained. The growth of the electrophoretic mobility with the elapsed time for a cylindrical particle is substantially slower than for a spherical particle.
Welsh, J; McClelland, M
1991-01-01
Polymorphisms in genomic fingerprints generated by arbitrarily primed PCR (AP-PCR) can distinguish between slightly divergent strains of any organism. Single oligodeoxyribonucleotide (oligo) primers have been used to generate such fingerprints, with the same primer being present at the 5' end of both strands for every PCR product. We used three arbitrary oligos, individually and in pairs, to generate six different genomic fingerprints of the same mouse genomic DNAs. Fewer than half of the products in genomic fingerprints generated using the oligos in pairs were the same as those produced by AP-PCR using one of the three oligos alone. Thus, a few oligos could be used in a very large number of single and pairwise combinations, each producing a distinct AP-PCR fingerprint with the potential to identify new polymorphisms. For example, 50 oligos can be used in a matrix of pairwise combinations to produce 2,500 fingerprints, in which at least half the data can be expected to be unique to each pair. We demonstrate this principle by using two oligos, alone and together, to generate three sets of fingerprints and map thirteen polymorphisms in the C57BL/6J x DBA/2J set of recombinant inbred mice. Images PMID:1923811
NASA Astrophysics Data System (ADS)
Boche, H.; Nötzel, J.
2014-12-01
This work is motivated by a quite general question: Under which circumstances are the capacities of information transmission systems continuous? The research is explicitly carried out on finite arbitrarily varying quantum channels (AVQCs). We give an explicit example that answers the recent question whether the transmission of messages over AVQCs can benefit from assistance by distribution of randomness between the legitimate sender and receiver in the affirmative. The specific class of channels introduced in that example is then extended to show that the unassisted capacity does have discontinuity points, while it is known that the randomness-assisted capacity is always continuous in the channel. We characterize the discontinuity points and prove that the unassisted capacity is always continuous around its positivity points. After having established shared randomness as an important resource, we quantify the interplay between the distribution of finite amounts of randomness between the legitimate sender and receiver, the (nonzero) probability of a decoding error with respect to the average error criterion and the number of messages that can be sent over a finite number of channel uses. We relate our results to the entanglement transmission capacities of finite AVQCs, where the role of shared randomness is not yet well understood, and give a new sufficient criterion for the entanglement transmission capacity with randomness assistance to vanish.
Exploring arbitrarily high orders of optimized perturbation theory in QCD with nf → 161/2
NASA Astrophysics Data System (ADS)
Stevenson, P. M.
2016-09-01
Perturbative QCD with nf flavours of massless quarks becomes simple in the hypothetical limit nf → 161/2, where the leading β-function coefficient vanishes. The Banks-Zaks (BZ) expansion in a0 ≡8/321 (161/2 -nf) is straightforward to obtain from perturbative results in MS ‾ or any renormalization scheme (RS) whose nf dependence is 'regular'. However, 'irregular' RS's are perfectly permissible and should ultimately lead to the same BZ results. We show here that the 'optimal' RS determined by the Principle of Minimal Sensitivity does yield the same BZ-expansion results when all orders of perturbation theory are taken into account. The BZ limit provides an arena for exploring optimized perturbation theory at arbitrarily high orders. These explorations are facilitated by a 'master equation' expressing the optimization conditions in the fixed-point limit. We find an intriguing strong/weak coupling duality a →a*2 / a about the fixed point a*.
Freeman, S.; Rodriguez, R.J.
1995-01-01
A collection of 39 isolates of Colletotrichum acutatum, C. fragariae and C. gloeosporioides, which cause anthracnose on strawberry, was grouped into species based on the arbitrarily primed polymerase chain reaction (ap-PCR). All isolates used had previously been identified according to classical taxonomic morphology. Ap-PCR amplification of genomic DNA using four different primers allowed for reliable differentiation between isolates of C. acutatum, C. fragariae and two genotypes of C. gloeosporioides. Fifteen of the 18 C. acutatum isolates were very similar, although three isolates which produced a red pigment had distinctly different banding patterns. Nearly identical banding patterns were observed for all nine isolates of C. fragariae. The 12 C. gloeosporioides isolates were more diverse and two separate genotypes, Cgl-1 (six isolates) and Cgl-2 (five isolates) were distinguished by ap-PCR. An additional isolate did not conform to either the Cgl-1 or Cgl-2 genotypes. The utility of ap-PCR compared with other molecular techniques for reliable identification of Colletotrichum isolates pathogenic on strawberry is discussed.
Developmental Differences in Shape Processing
ERIC Educational Resources Information Center
Sera, Maria D.; Gordon Millett, Katherine
2011-01-01
Considerable evidence indicates that shape similarity plays a major role in object recognition, identification and categorization. However, little is known about shape processing and its development. Across four experiments, we addressed two related questions. First, what makes objects similar in shape? Second, how does the processing of shape…
Shaped beam scattering by an anisotropic particle
NASA Astrophysics Data System (ADS)
Chen, Zhenzhen; Zhang, Huayong; Huang, Zhixiang; Wu, Xianliang
2017-03-01
An exact semi-analytical solution to the electromagnetic scattering from an optically anisotropic particle illuminated by an arbitrarily shaped beam is proposed. The scattered fields and fields within the anisotropic particle are expanded in terms of spherical vector wave functions. The unknown expansion coefficients are determined by using the boundary conditions and the method of moments scheme. For incidence of a Gaussian beam, zero-order Bessel beam and Hertzian electric dipole radiation, numerical results of the normalized differential scattering cross section are given to a uniaxial, gyrotropic anisotropic spheroid and circular cylinder of finite length. The scattering properties are analyzed concisely.
Momentum Transfer by Laser Ablation of Irregularly Shaped Space Debris
Liedahl, D A; Libby, S B; Rubenchik, A
2010-02-04
Proposals for ground-based laser remediation of space debris rely on the creation of appropriately directed ablation-driven impulses to either divert the fragment or drive it into an orbit with a perigee allowing atmospheric capture. For a spherical fragment, the ablation impulse is a function of the orbital parameters and the laser engagement angle. If, however, the target is irregularly shaped and arbitrarily oriented, new impulse effects come into play. Here we present an analysis of some of these effects.
Momentum Transfer by Laser Ablation of Irregularly Shaped Space Debris
Liedahl, Duane A.; Libby, Stephen B.; Rubenchik, Alexander
2010-10-08
Proposals for ground-based laser remediation of space debris rely on the creation of appropriately directed ablation-driven impulses to either divert the fragment or drive it into an orbit with a perigee allowing atmospheric capture. For a spherical fragment, the ablation impulse is a function of the orbital parameters and the laser engagement angle. If, however, the target is irregularly shaped and arbitrarily oriented, new impulse effects come into play. Here we present an analysis of some of these effects.
Low-speckle holographic beam shaping of high-coherence EUV sources
Anderson, Christopher N.; Miyakawa, Ryan H.; Naulleau, Patrick
2010-08-01
This paper describes a method to arbitrarily shape and homogenize high-coherence extreme ultraviolet sources using time-varying holographic optical elements and a scanning subsystem to mitigate speckle. In systems with integration times longer than 100 ms, a speckle contrast below 1% can be achieved.
NASA Technical Reports Server (NTRS)
Rahmat-Samii, Y.; Galindo-Israel, V.
1980-01-01
A vector radiation integral is derived for an offset shaped reflector illuminated by an arbitrarily located and oriented source. A procedure for expressing the integral in terms of a series of the Fourier transforms of an effective aperture distribution is discussed. The Jacobi-Bessel series is used to evaluate the Fourier transforms. Numerical results are presented for different reflector configurations and source locations.
NASA Technical Reports Server (NTRS)
Rahmat-Samii, Y.; Galindo-Israel, V.
1980-01-01
A vector radiation integral is derived for an offset shaped reflector illuminated by an arbitrarily located and oriented source. A procedure for expressing the integral in terms of a series of the Fourier transforms of an effective aperture distribution is discussed. The Jacobi-Bessel series is used to evaluate the Fourier transforms. Numerical results are presented for different reflector configurations and source locations.
ERIC Educational Resources Information Center
Rule, Audrey C.
This document describes a game that provides students with practice in recognizing three dimensional crystal shapes and planar geometric shapes of crystal faces. It contains information on the objective of the game, game preparation, and rules for playing. Play cards are included (four to a page). (ASK)
NASA Technical Reports Server (NTRS)
Deshpande, Manohar D.
2005-01-01
A new numerical simulation method using the finite element methodology (FEM) is presented to study electromagnetic scattering due to an arbitrarily shaped material body doped randomly with thin and short metallic wires. The FEM approach described in many standard text books is appropriately modified to account for the presence of thin and short metallic wires distributed randomly inside an arbitrarily shaped material body. Using this modified FEM approach, the electromagnetic scattering due to cylindrical, spherical material body doped randomly with thin metallic wires is studied.
NASA Astrophysics Data System (ADS)
Dev, Apul N.; Deka, Manoj Kr.
2017-10-01
The evolution characteristics of dust-acoustic shock wave phenomenon in an arbitrarily charged dusty plasma in presence of pair-ion are investigated by deriving modified Complex Burgers' equation. In this work, the effect of state of both the ions on the shock wave potential is analysed and discussed in detail. It has been observed that the variation of the non-linear coefficient is more consistent with the non-isothermal positive ions moving toward thermal equilibrium than with non-isothermal negative ions. A significant effect on the amplitude of the shock wave potential is observed as the distribution of the non-isothermal positive and negative ions changes from a hump shape through the flat-topped to Boltzmann type. A weighty effect on the height of the shock wave is observed as and when the Mach number of positive and negative ions changes. The shock wave potential shows a greater (lesser) value with negative (positive) ions moving ahead for thermal equilibrium.
NASA Astrophysics Data System (ADS)
Pavičić, Mladen
2017-06-01
Quantum contextuality turns out to be a necessary resource for universal quantum computation and important in the field of quantum information processing. It is therefore of interest both for theoretical considerations and for experimental implementation to find new types and instances of contextual sets and develop methods of their optimal generation. We present an arbitrarily exhaustive hypergraph-based generation of the most explored contextual sets [Kochen-Specker (KS) ones] in 4, 6, 8, 16, and 32 dimensions. We consider and analyze 12 KS classes and obtain numerous properties of theirs, which we then compare with the results previously obtained in the literature. We generate several thousand additional types and instances of KS sets, including all KS sets in three of the classes and the upper part of a fourth set. We make use of the McKay-Megill-Pavičić (MMP) hypergraph language, algorithms, and programs to generate KS sets strictly following their definition from the Kochen-Specker theorem. This approach proves to be particularly advantageous over the parity-proof-based ones (which prevail in the literature) since it turns out that only a very few KS sets have a parity proof (in six KS classes <0.01% and in one of them 0%). MMP hypergraph formalism enables a translation of an exponentially complex task of solving systems of nonlinear equations, describing KS vector orthogonalities, into a statistically linearly complex task of evaluating vertex states of hypergraph edges, thus exponentially speeding up the generation of KS sets and enabling us to generate billions of novel instances of them. The MMP hypergraph notation also enables us to graphically represent KS sets and to visually discern their features.
Multicenter evaluation of arbitrarily primed PCR for typing of Staphylococcus aureus strains.
van Belkum, A; Kluytmans, J; van Leeuwen, W; Bax, R; Quint, W; Peters, E; Fluit, A; Vandenbroucke-Grauls, C; van den Brule, A; Koeleman, H
1995-01-01
Fifty-nine isolates of Staphylococcus aureus and a single strain of Staphylococcus intermedius were typed by arbitrarily primed PCR (AP-PCR). To study reproducibility and discriminatory abilities, AP-PCR was carried out in seven laboratories with a standardized amplification protocol, template DNA isolated in a single institution, and a common set of three primers with different resolving powers. The 60 strains could be divided into 16 to 30 different genetic types, depending on the laboratory. This difference in resolution was due to differences in technical procedures (as shown by the deliberate introduction of experimental variables) and/or the interpretation of the DNA fingerprints. However, this did not hamper the epidemiologically correct clustering of related strains. The average number of different genotypes identified exceeded those of the more traditional typing strategies (F. C. Tenover, R. Arbeit, G. Archer, J. Biddle, S. Byrne, R. Goering, G. Hancock, G. A. Hebert, B. Hill, R. Hollis, W. R. Jarvis, B. Kreiswirth, W. Eisner, J. Maslow, L. K. McDougal, J. M. Miller, M. Mulligan, and M. A. Pfaller, J. Clin. Microbiol. 32:407-415, 1994). Comparison of AP-PCR with pulsed-field gel electrophoresis (PFGE) indicated the existence of strains with constant PFGE types but variable AP-PCR types. The reverse (constant AP-PCR and variable PFGE patterns) was also observed. This indicates additional resolution for combined analyses. It is concluded that AP-PCR is well suited for genetic analysis and monitoring of nosocomial spreading of staphylococci. The interlaboratory reproducibility of DNA-banding patterns and the intralaboratory standardization need improvement. PMID:7650182
Multicenter evaluation of arbitrarily primed PCR for typing of Staphylococcus aureus strains.
van Belkum, A; Kluytmans, J; van Leeuwen, W; Bax, R; Quint, W; Peters, E; Fluit, A; Vandenbroucke-Grauls, C; van den Brule, A; Koeleman, H
1995-06-01
Fifty-nine isolates of Staphylococcus aureus and a single strain of Staphylococcus intermedius were typed by arbitrarily primed PCR (AP-PCR). To study reproducibility and discriminatory abilities, AP-PCR was carried out in seven laboratories with a standardized amplification protocol, template DNA isolated in a single institution, and a common set of three primers with different resolving powers. The 60 strains could be divided into 16 to 30 different genetic types, depending on the laboratory. This difference in resolution was due to differences in technical procedures (as shown by the deliberate introduction of experimental variables) and/or the interpretation of the DNA fingerprints. However, this did not hamper the epidemiologically correct clustering of related strains. The average number of different genotypes identified exceeded those of the more traditional typing strategies (F. C. Tenover, R. Arbeit, G. Archer, J. Biddle, S. Byrne, R. Goering, G. Hancock, G. A. Hebert, B. Hill, R. Hollis, W. R. Jarvis, B. Kreiswirth, W. Eisner, J. Maslow, L. K. McDougal, J. M. Miller, M. Mulligan, and M. A. Pfaller, J. Clin. Microbiol. 32:407-415, 1994). Comparison of AP-PCR with pulsed-field gel electrophoresis (PFGE) indicated the existence of strains with constant PFGE types but variable AP-PCR types. The reverse (constant AP-PCR and variable PFGE patterns) was also observed. This indicates additional resolution for combined analyses. It is concluded that AP-PCR is well suited for genetic analysis and monitoring of nosocomial spreading of staphylococci. The interlaboratory reproducibility of DNA-banding patterns and the intralaboratory standardization need improvement.
Gomez-Lus, P; Fields, B S; Benson, R F; Martin, W T; O'Connor, S P; Black, C M
1993-01-01
Arbitrarily primed polymerase chain reaction (AP-PCR) was used to characterize Legionella pneumophila serogroup 1. Cells from a single colony could be subtyped by AP-PCR within a few hours. The discrimination between strains of L. pneumophila serogroup 1 by AP-PCR was equivalent to that by monoclonal antibody analysis and ribotyping. Four strains representing the monoclonal antibody pattern most frequently associated with outbreaks all yielded unique amplicon patterns by AP-PCR. Images PMID:8394380
Sigurdardottir, Heida M; Sheinberg, David L
2015-07-01
The lateral intraparietal area (LIP) is thought to play an important role in the guidance of where to look and pay attention. LIP can also respond selectively to differently shaped objects. We sought to understand to what extent short-term and long-term experience with visual orienting determines the responses of LIP to objects of different shapes. We taught monkeys to arbitrarily associate centrally presented objects of various shapes with orienting either toward or away from a preferred spatial location of a neuron. The training could last for less than a single day or for several months. We found that neural responses to objects are affected by such experience, but that the length of the learning period determines how this neural plasticity manifests. Short-term learning affects neural responses to objects, but these effects are only seen relatively late after visual onset; at this time, the responses to newly learned objects resemble those of familiar objects that share their meaning or arbitrary association. Long-term learning affects the earliest bottom-up responses to visual objects. These responses tend to be greater for objects that have been associated with looking toward, rather than away from, LIP neurons' preferred spatial locations. Responses to objects can nonetheless be distinct, although they have been similarly acted on in the past and will lead to the same orienting behavior in the future. Our results therefore indicate that a complete experience-driven override of LIP object responses may be difficult or impossible. We relate these results to behavioral work on visual attention.
Relations among early object recognition skills: Objects and letters.
Augustine, Elaine; Jones, Susan S; Smith, Linda B; Longfield, Erica
2015-04-01
Human visual object recognition is multifaceted, with several domains of expertise. Developmental relations between young children's letter recognition and their 3-dimensional object recognition abilities are implicated on several grounds but have received little research attention. Here, we ask how preschoolers' success in recognizing letters relates to their ability to recognize 3-dimensional objects from sparse shape information alone. A relation is predicted because perception of the spatial relations is critical in both domains. Seventy-three 2 ½- to 4-year-old children completed a Letter Recognition task, measuring the ability to identify a named letter among 3 letters with similar shapes, and a "Shape Caricature Recognition" task, measuring recognition of familiar objects from sparse, abstract information about their part shapes and the spatial relations among those parts. Children also completed a control "Shape Bias" task, in which success depends on recognition of overall object shape but not of relational structure. Children's success in letter recognition was positively related to their shape caricature recognition scores, but not to their shape bias scores. The results suggest that letter recognition builds upon developing skills in attending to and representing the relational structure of object shape, and that these skills are common to both 2-dimensional and 3-dimensional object perception.
NASA Technical Reports Server (NTRS)
Hunter, W. F.
1974-01-01
A derivation of the equations which govern the deformation of an arbitrarily curved and twisted space beam is presented. These equations differ from those of the classical theory in that (1) extensional effects are included; (2) the strain-displacement relations are derived; and (3) the expressions for the stress resultants are developed from the strain displacement relations. It is shown that the torsional stress resultant obtained by the classical approach is basically incorrect except when the cross-section is circular. The governing equations are given in the form of first-order differential equations. A numerical algorithm is given for obtaining the natural vibration characteristics and example problems are presented.
Wide-angle point-to-point x-ray imaging with almost arbitrarily large angles of incidence
Bitter, M.; Hill, K. W.; Scott, S.; Feder, R.; Ko, Jinseok; Ince-Cushman, A.; Rice, J. E.
2008-10-15
The paper describes a new scheme for wide-angle point-to-point x-ray imaging with almost arbitrarily large angles of incidence by a matched pair of spherically bent crystals to eliminate the astigmatism, which is a well-known imaging error of spherical mirrors. In addition to x rays, the scheme should be applicable to a very broad spectrum of the electromagnetic radiation, including microwaves, infrared and visible light, as well as UV and extreme UV radiation, if the crystals are replaced with appropriate spherical reflectors. The scheme may also be applicable to the imaging with ultrasound.
Object tracking with stereo vision
NASA Technical Reports Server (NTRS)
Huber, Eric
1994-01-01
A real-time active stereo vision system incorporating gaze control and task directed vision is described. Emphasis is placed on object tracking and object size and shape determination. Techniques include motion-centroid tracking, depth tracking, and contour tracking.
Design charts for arbitrarily pivoted, liquid-lubricated flat-sector-pad thrust bearing
NASA Technical Reports Server (NTRS)
Etsion, I.
1977-01-01
A flat, sector-shaped geometry for a liquid-lubricated thrust bearing is analyzed considering both the pitch and roll of the pad. Results are presented in design charts that enable a direct approach to the design of point- and line-pivoted, tilting pad bearings. A comparison is made with the Mitchell bearing approximation and it is found that this approximation always overestimates load capacity.
NASA Astrophysics Data System (ADS)
Horváth, Gábor; Buchta, Krisztián; Varjú, Dezsö
2003-06-01
It is a well-known phenomenon that when we look into the water with two aerial eyes, both the apparent position and the apparent shape of underwater objects are different from the real ones because of refraction at the water surface. Earlier studies of the refraction-distorted structure of the underwater binocular visual field of aerial observers were restricted to either vertically or horizontally oriented eyes. We investigate a generalized version of this problem: We calculate the position of the binocular image point of an underwater object point viewed by two arbitrarily positioned aerial eyes, including oblique orientations of the eyes relative to the flat water surface. Assuming that binocular image fusion is performed by appropriate vergent eye movements to bring the object's image onto the foveas, the structure of the underwater binocular visual field is computed and visualized in different ways as a function of the relative positions of the eyes. We show that a revision of certain earlier treatments of the aerial imaging of underwater objects is necessary. We analyze and correct some widespread erroneous or incomplete representations of this classical geometric optical problem that occur in different textbooks. Improving the theory of aerial binocular imaging of underwater objects, we demonstrate that the structure of the underwater binocular visual field of aerial observers distorted by refraction is more complex than has been thought previously. (vision).
Freeman, S.; Pham, M.; Rodriguez, R.J.
1993-01-01
Molecular genotyping of Colletotrichum species based on arbitrarily primed PCR, A + T-rich DNA, and nuclear DNA analyses. Experimental Mycology 17, 309-322. Isolates of Colletotrichum were grouped into 10 separate species based on arbitrarily primed PCR (ap-PCR), A + T-rich DNA (AT-DNA) and nuclear DNA banding patterns. In general, the grouping of Colletotrichum isolates by these molecular approaches corresponded to that done by classical taxonomic identification, however, some exceptions were observed. PCR amplification of genomic DNA using four different primers allowed for reliable differentiation between isolates of the 10 species. HaeIII digestion patterns of AT-DNA also distinguished between species of Colletotrichum by generating species-specific band patterns. In addition, hybridization of the repetitive DNA element (GcpR1) to genomic DNA identified a unique set of Pst 1-digested nuclear DNA fragments in each of the 10 species of Colletotrichum tested. Multiple isolates of C. acutatum, C. coccodes, C. fragariae, C. lindemuthianum, C. magna, C. orbiculare, C. graminicola from maize, and C. graminicola from sorghum showed 86-100% intraspecies similarity based on ap-PCR and AT-DNA analyses. Interspecies similarity determined by ap-PCR and AT-DNA analyses varied between 0 and 33%. Three distinct banding patterns were detected in isolates of C. gloeosporioides from strawberry. Similarly, three different banding patterns were observed among isolates of C. musae from diseased banana.
Boche, H. Janßen, G.
2014-08-01
We consider one-way quantum state merging and entanglement distillation under compound and arbitrarily varying source models. Regarding quantum compound sources, where the source is memoryless, but the source state an unknown member of a certain set of density matrices, we continue investigations begun in the work of Bjelaković et al. [“Universal quantum state merging,” J. Math. Phys. 54, 032204 (2013)] and determine the classical as well as entanglement cost of state merging. We further investigate quantum state merging and entanglement distillation protocols for arbitrarily varying quantum sources (AVQS). In the AVQS model, the source state is assumed to vary in an arbitrary manner for each source output due to environmental fluctuations or adversarial manipulation. We determine the one-way entanglement distillation capacity for AVQS, where we invoke the famous robustification and elimination techniques introduced by Ahlswede. Regarding quantum state merging for AVQS we show by example that the robustification and elimination based approach generally leads to suboptimal entanglement as well as classical communication rates.
System for controlled acoustic rotation of objects
NASA Technical Reports Server (NTRS)
Barmatz, M. B. (Inventor)
1983-01-01
A system is described for use with acoustically levitated objects, which enables close control of rotation of the object. One system includes transducers that propagate acoustic waves along the three dimensions (X, Y, Z) of a chamber of rectangular cross section. Each transducers generates one wave which is resonant to a corresponding chamber dimension to acoustically levitate an object, and additional higher frequency resonant wavelengths for controlling rotation of the object. The three chamber dimensions and the corresponding three levitation modes (resonant wavelengths) are all different, to avoid degeneracy, or interference, of waves with one another, that could have an effect on object rotation. Only the higher frequencies, with pairs of them having the same wavelength, are utilized to control rotation, so that rotation is controlled independently of levitation and about any arbitrarily chosen axis.
Object Classification via Planar Abstraction
NASA Astrophysics Data System (ADS)
Oesau, Sven; Lafarge, Florent; Alliez, Pierre
2016-06-01
We present a supervised machine learning approach for classification of objects from sampled point data. The main idea consists in first abstracting the input object into planar parts at several scales, then discriminate between the different classes of objects solely through features derived from these planar shapes. Abstracting into planar shapes provides a means to both reduce the computational complexity and improve robustness to defects inherent to the acquisition process. Measuring statistical properties and relationships between planar shapes offers invariance to scale and orientation. A random forest is then used for solving the multiclass classification problem. We demonstrate the potential of our approach on a set of indoor objects from the Princeton shape benchmark and on objects acquired from indoor scenes and compare the performance of our method with other point-based shape descriptors.
[Cell membrane electroporator with digital generation of random shaped pulses].
Iakovenko, S A; Trubitsin, B V
2003-01-01
A Digital Poration System (DPS), a versatile device for electrotreatment of biological objects by electric field pulses; was designed, constructed, and implemented. A feature distinguishing DPS from the currently available electroporators based on capacitor discharge through the load is the use of a digital-to-analog converter card as a generator of pulses applied for electroporation of biological membranes, with further amplification of the pulse by both voltage and current. The shape of pulses, including bipolar pulses, is arbitrarily programmable in DPS unlike other electroporators providing exponentially decaying and square-wave pulses only. Thus, the application area of DPS is substantially extended. In DPS, many of the drawbacks inherent in capacitor electroporators are removed, including the need for an additional external pulse analyzer monitoring and logging the electroporation processes, the necessity to recharge the capacitor before any new pulse, a poor precision of setting and measuring the pulse parameters, the need for an additional generator of long-lasting low-voltage signals for electrophoresis of ions into the porated object, the need for additional AC generators for the alignment of cells before, after, and during electroporation, and the need for an additional microprocessor to control multi-pulse and/or repetitive protocols. DPS provides a slew rate of about 1 V/1 ns required for the electroporation of most mammalian somatic cells, with +/- 250 V output voltage and 500 Ohm load resistance. The application area of DPS is much wider than for the available porators. It includes electrochemotherapy, cell electrofusion, oocyte activation by mimicking calcium waves (the latter two are the crucial components of mammalian organism cloning technology), dielectrophoretic bunching and orientation ordering of cells, sorting of cells, and electrophoresis of charged species into the cells.
Pesyna, Colin; Pundi, Krishna; Flanders, Martha
2011-01-01
The neural control of hand movement involves coordination of the sensory, motor and memory systems. Recent studies have documented the motor coordinates for hand shape, but less is known about the corresponding patterns of somatosensory activity. To initiate this line of investigation, the present study characterized the sense of hand shape by evaluating the influence of differences in the amount of grasping or twisting force, and differences in forearm orientation. Human subjects were asked to use the left hand to report the perceived shape of the right hand. In Experiment 1, six commonly grasped items were arranged on the table in front of the subject: bottle, doorknob, egg, notebook, carton, pan. With eyes closed, subjects used the right hand to lightly touch, forcefully support or imagine holding each object, while 15 joint angles were measured in each hand with a pair of wired gloves. The forces introduced by supporting or twisting did not influence the perceptual report of hand shape, but for most objects, the report was distorted in a consistent manner by differences in forearm orientation. Subjects appeared to adjust the intrinsic joint angles of the left hand, as well as the left wrist posture, so as to maintain the imagined object in its proper spatial orientation. In a second experiment, this result was largely replicated with unfamiliar objects. Thus somatosensory and motor information appear to be coordinated in an object-based, spatial coordinate system, sensitive to orientation relative to gravitational forces, but invariant to grasp forcefulness. PMID:21389230
Estimation of continuous object distributions from limited Fourier magnitude measurements
NASA Astrophysics Data System (ADS)
Byrne, Charles L.; Fiddy, Michael A.
1987-01-01
From finite complex spectral data one can construct a continuous object with a given support that is consistent with the data. Given Fourier magnitude data only, one can choose the phases arbitrarily in the above construction. The energy in the extrapolated spectrum is phase-dependent and provides a cost function to be used in phase retrieval. The minimization process is performed iteratively, using an algorithm that can be viewed as a combination of Gerchberg-Papoulis and Fienup error reduction.
Subjectively Interpreted Shape Dimensions as Privileged and Orthogonal Axes in Mental Shape Space
ERIC Educational Resources Information Center
Ons, Bart; De Baene, Wouter; Wagemans, Johan
2011-01-01
The shape of an object is fundamental in object recognition but it is still an open issue to what extent shape differences are perceived analytically (i.e., by the dimensional structure of the shapes) or holistically (i.e., by the overall similarity of the shapes). The dimensional structure of a stimulus is available in a primary stage of…
Gross, Michael
2015-10-05
Earth is much more complex than all the other solar system objects that we know. Thanks to its rich and diverse geology, our planet can offer habitats to a wide range of living species. Emerging insights suggest that this is not just a happy coincidence, but that life itself has in many ways helped to shape the planet.
NASA Astrophysics Data System (ADS)
Lošdorfer Božič, Anže; Podgornik, Rudolf
2013-02-01
Inhomogeneous charge distributions have important repercussions on electrostatic interactions in systems of charged particles but are often difficult to examine theoretically. We investigate how electrostatic interactions are influenced by patchy charge distributions exhibiting certain point group symmetries. We derive a general form of the electrostatic interaction energy of two permeable, arbitrarily charged spherical shells in the Debye-Hückel approximation and apply it to the case of particles with icosahedral, octahedral, and tetrahedral inhomogeneous charge distributions. We analyze in detail how charge distribution symmetry modifies the interaction energy and find that local charge inhomogeneities reduce the repulsion of two overall equally charged particles, while sufficient orientational variation in the charge distribution can turn the minimum interaction energy into an attraction. Additionally, we show that larger patches and thus lower symmetries and wave numbers result in bigger attraction given the same variation.
NASA Technical Reports Server (NTRS)
Degani, D.
1984-01-01
A numerical algorithm that is second-order accurate in time has been developed for the conjugated problem of a separated, compressible flow field and a conductive solid body. The full two-dimensional time-dependent Navier-Stokes equations are coupled with the time-dependent energy equation for the solid body and are solved simultaneously. using implicit algorithms. The energy equation for the solid body may include arbitrarily distributed heat sources. The algorithm has been exmined for the case of two-dimensional supersonic compression-corner interaction, with a heat source embedded in the wall in the vicinity of the separation bubble and the attached boundary layer. The effect of the heat source on the flow field is studied for steady and transient cases.
NASA Astrophysics Data System (ADS)
Kang, Seokkoo; Sotiropoulos, Fotis
2010-11-01
A numerical method is developed for simulating three-dimensional free surface flows in open channels of arbitrarily complex bathymetry. The complex geometry is handled using the curvilinear immersed boundary (CURVIB) method of Ge and Sotiropoulos (J. of Computational Physics, 2007) and free surface deformation is modeled by employing a two-phase flow level-set approach. A new method is developed for solving the level-set equations and the reinitialization equation in the context of the CURVIB framework. The method is validated for various free-surface model problems and its capabilities are demonstrated by applying to simulate turbulent free-surface flow in an open channel with embedded complex hydraulic structures.
Rahman, O.; Mamun, A. A.
2011-08-15
The nonlinear propagation of dust-ion-acoustic (DIA) waves in a dusty plasma containing trapped electrons following vortex-like distribution, cold mobile ions, and arbitrarily charged static dust is theoretically investigated. The properties of small but finite amplitude DIA solitary waves (SWs) are studied by employing the reductive perturbation technique. It is found that owing to the departure from the Maxwellian electron distribution to a vortex-like one, the dynamics of such DIA SWs is governed by a modified Korteweg-de Vries equation. The basic features (amplitude, width, speed, etc.) of such DIA SWs, which are found to be significantly modified by the vortex-like electron distribution and dust polarity, are also examined. The implications of our results to space and laboratory dusty plasmas are briefly discussed.
NASA Technical Reports Server (NTRS)
Meitner, Peter L.
2004-01-01
A calculation procedure is presented which allows the one-dimensional determination of flow distributions in arbitrarily connected (branching) flow passages having multiple inlets and exits. The procedure uses an adaptation of the finite element technique, iteratively coupled with an accurate one-dimensional flow solver. The procedure eliminates the usual restrictions inherent with finite element flow calculations. Unlike existing one-dimensional methods, which require simplifications to the flow equations (uncoupling the momentum and energy equations), to allow for arbitrary branching and multiple inlets and exits, the only limitation of the described methodology is that, at present, it can only accommodate non-rotating configurations (no pumping effects). The calculation procedure is robust, and will always converge for physically possible flow. The procedure is described, and its use is illustrated by an example.
NASA Technical Reports Server (NTRS)
Wang, T. N. C.; Bell, T. F.
1972-01-01
With the use of a power integral formulation, a study is made of the vlf/elf radiation patterns of arbitrarily oriented electric and magnetic dipoles in a cold lossless multicomponent magnetoplasma. Expressions for the ray patterns are initially developed that apply for arbitrary values of driving frequency, static magnetic-field strength, plasma density, and composition. These expressions are subsequently specialized to vlf/elf radiation in a plasma modeled on the magnetosphere. A series of representative pattern plots are presented for frequencies between the proton and electron gyrofrequencies. These patterns illustrate the fact that focusing effects that arise from the geometrical properties of the refractive index surface tend to dominate the radiation distribution over the entire range from the electron gyrofrequency to 4.6 times the proton gyrofrequency. It is concluded that focusing effects should be of significant importance in the design of a vlf/elf satellite transmitting system in the magnetosphere.
NASA Astrophysics Data System (ADS)
Pan, Wei-Zhen; Yang, Xue-Jun; Xie, Zhi-Kun
2011-04-01
Using a new tortoise coordinate transformation, this paper investigates the Hawking effect from an arbitrarily accelerating charged black hole by the improved Damour—Ruffini method. After the tortoise coordinate transformation, the Klein—Gordon equation can be written as the standard form at the event horizon. Then extending the outgoing wave from outside to inside of the horizon analytically, the surface gravity and Hawking temperature can be obtained automatically. It is found that the Hawking temperatures of different points on the surface are different. The quantum nonthermal radiation characteristics of a black hole near the event horizon is also discussed by studying the Hamilton—Jacobi equation in curved spacetime and the maximum overlap of the positive and negative energy levels near the event horizon is given. There is a dimensional problem in the standard tortoise coordinate and the present results may be more reasonable.
NASA Astrophysics Data System (ADS)
Yi, Xi; Chen, Weiting; Wu, Linhui; Zhang, Wei; Li, Jiao; Wang, Xin; Zhang, Limin; Zhao, Huijuan; Gao, Feng
2013-03-01
At present, the most widely accepted forward model in diffuse optical tomography (DOT) is the diffusion equation, which is derived from the radiative transfer equation by employing the P1 approximation. However, due to its validity restricted to highly scattering regions, this model has several limitations for the whole-body imaging of small-animals, where some cavity and low scattering areas exist. To overcome the difficulty, we presented a Graphic-Processing- Unit(GPU) implementation of Monte-Carlo (MC) modeling for photon migration in arbitrarily heterogeneous turbid medium, and, based on this GPU-accelerated MC forward calculation, developed a fast, universal DOT image reconstruction algorithm. We experimentally validated the proposed method using a continuous-wave DOT system in the photon-counting mode and a cylindrical phantom with a cavity inclusion.
ERIC Educational Resources Information Center
Butterworth, James R.
1975-01-01
Industrial objectives, if they are employee oriented, produce feedback, and the motivation derived from the feedback helps reduce turnover. Feedback is the power to clarify objectives, to stimulate communication, and to motivate people. (Author/MW)
ERIC Educational Resources Information Center
Butterworth, James R.
1975-01-01
Industrial objectives, if they are employee oriented, produce feedback, and the motivation derived from the feedback helps reduce turnover. Feedback is the power to clarify objectives, to stimulate communication, and to motivate people. (Author/MW)
What Features Can Tell Us about Shape.
Schreck, Tobias
2017-01-01
3D shape representations are essential when storing shape information for natural and manmade objects. To make use of shape information, many applications require shape-processing functionality, such as for search, annotation, classification, modeling, restoration, or collection exploration. This article discusses feature-based approaches and how they can support such functionality.
Real-time 3-D shape measurement with composite phase-shifting fringes and multi-view system.
Tao, Tianyang; Chen, Qian; Da, Jian; Feng, Shijie; Hu, Yan; Zuo, Chao
2016-09-05
In recent years, fringe projection has become an established and essential method for dynamic three-dimensional (3-D) shape measurement in different fields such as online inspection and real-time quality control. Numerous high-speed 3-D shape measurement methods have been developed by either employing high-speed hardware, minimizing the number of pattern projection, or both. However, dynamic 3-D shape measurement of arbitrarily-shaped objects with full sensor resolution without the necessity of additional pattern projections is still a big challenge. In this work, we introduce a high-speed 3-D shape measurement technique based on composite phase-shifting fringes and a multi-view system. The geometry constraint is adopted to search the corresponding points independently without additional images. Meanwhile, by analysing the 3-D position and the main wrapped phase of the corresponding point, pairs with an incorrect 3-D position or a considerable phase difference are effectively rejected. All of the qualified corresponding points are then corrected, and the unique one as well as the related period order is selected through the embedded triangular wave. Finally, considering that some points can only be captured by one of the cameras due to the occlusions, these points may have different fringe orders in the two views, so a left-right consistency check is employed to eliminate those erroneous period orders in this case. Several experiments on both static and dynamic scenes are performed, verifying that our method can achieve a speed of 120 frames per second (fps) with 25-period fringe patterns for fast, dense, and accurate 3-D measurement.
Young Children's Self-Generated Object Views and Object Recognition
ERIC Educational Resources Information Center
James, Karin H.; Jones, Susan S.; Smith, Linda B.; Swain, Shelley N.
2014-01-01
Two important and related developments in children between 18 and 24 months of age are the rapid expansion of object name vocabularies and the emergence of an ability to recognize objects from sparse representations of their geometric shapes. In the same period, children also begin to show a preference for planar views (i.e., views of objects held…
Beyond singular values and loop shapes
NASA Technical Reports Server (NTRS)
Stein, G.
1985-01-01
The status of singular value loop-shaping as a design paradigm for multivariable feedback systems is reviewed. It shows that this paradigm is an effective design tool whenever the problem specifications are spacially round. The tool can be arbitrarily conservative, however, when they are not. This happens because singular value conditions for robust performance are not tight (necessary and sufficient) and can severely overstate actual requirements. An alternate paradign is discussed which overcomes these limitations. The alternative includes a more general problem formulation, a new matrix function mu, and tight conditions for both robust stability and robust performance. The state of the art currently permits analysis of feedback systems within this new paradigm. Synthesis remains a subject of research.
Nonlocal optical response of metal nanostructures with arbitrary shape.
McMahon, J. M.; Gray, S. K.; Schatz, G. C.; Northwestern Univ.
2009-08-28
We present an implementation of Maxwell's equations that incorporates the spatially nonlocal response of materials, an effect necessary to describe the optical properties of structures with features less than 10 nm. For the first time it is possible to investigate the nonlocal optical response of structures without spherical or planar shape, and outside of the electrostatic limit. As an illustration, we calculate the optical properties of Au nanowires and show that nonlocal effects are particularly important in structures with apex features, even for arbitrarily large sizes.
Becchio, Cristina; Bertone, Cesare
2003-07-01
Recent studies show that what connotes an object is first of all a certain spatio-temporal structure. In this paper we describe some of the temporal features characterizing the temporal structure of objects: pre-existence, persistence, conservation of identity in spite of perceptive discontinuity, surviving changes in colour, size, and shape. We argue that time is an indispensable attribute for every type of object and briefly discuss the implication of this view with respect to a specific neuropsychological syndrome: unilateral spatial neglect.
NASA Astrophysics Data System (ADS)
Kulikov, K. G.
2012-12-01
A mathematical model is proposed for predicting optical characteristics (refractive index and absorption coefficient) of a biotissue being simulated, which is probed in vivo by a laser beam. Blood corpuscles in this case are simulated by particles of irregular shape and various sizes, which are oriented arbitrarily in free space.
NASA Astrophysics Data System (ADS)
Kobayashi, Kiyoshi; Yamashita, Fumihiro; Abe, Jun-Ichi; Ueba, Masazumi
This paper presents a prototype group modem for a hyper-multipoint data gathering satellite communication system. It can handle arbitrarily and dynamically assigned FDMA signals by employing a novel FFT-type block demultiplexer/multiplexer. We clarify its configuration and operational principle. Experiments show that the developed modem offers excellent performance.
1993-11-28
degrees of freedom. Within each object, the programmer’s job is to manage the degrees of freedom in the object by adding subobjects and constraints...other constraint satisfiction mechanisms such as propagation of values. However, Siri recomputes the state of an object by solving a combination of...languages need not be as complicated as they are; a small number of powerful constructs can do the job just as well, and perhaps more elegantly. 154
Visual object affordances: object orientation.
Symes, Ed; Ellis, Rob; Tucker, Mike
2007-02-01
Five experiments systematically investigated whether orientation is a visual object property that affords action. The primary aim was to establish the existence of a pure physical affordance (PPA) of object orientation, independent of any semantic object-action associations or visually salient areas towards which visual attention might be biased. Taken together, the data from these experiments suggest that firstly PPAs of object orientation do exist, and secondly, the behavioural effects that reveal them are larger and more robust when the object appears to be graspable, and is oriented in depth (rather than just frontally) such that its leading edge appears to point outwards in space towards a particular hand of the viewer.
How shape from contours affects shape from shading.
Todorović, Dejan
2014-10-01
The spatial pattern of reflected light carries detailed but ambiguous information about 3D shapes of illuminated objects. A little studied factor that affects the perceived 3D relief of 2D shaded figures is the shape of their contours. An experiment is reported in which 102 subjects matched twelve contoured grating displays (horizontal three-cycle gratings with variously shaped top and bottom contours) with perspective line drawings of different 3D shapes, and also judged their depth extent and direction of illumination. The results showed that contour shapes can have surprisingly strong and salient effects on perceived relief. For each display there was a dominant matching drawing, chosen by the largest percentage of subjects, which varied from 95% to 26% across the set of displays. The luminance distribution of contoured gratings is essentially 1D, so that, compared to the general 2D case, their mathematical analysis is considerably simplified, and shape can in certain cases be recovered from shading in analytical form, yielding a three-parameter family of solutions. An analysis of subject responses showed that most reported reliefs had shapes which were closely related to members of the solution family. Furthermore, the particular perceived shapes of contoured gratings could with some success be predicted from the shapes of their contours, based on a simple shape-from-contours rule. However, the data also indicated the presence of a convexity tendency, independent from contour shape.
NONCONVEX REGULARIZATION FOR SHAPE PRESERVATION
CHARTRAND, RICK
2007-01-16
The authors show that using a nonconvex penalty term to regularize image reconstruction can substantially improve the preservation of object shapes. The commonly-used total-variation regularization, {integral}|{del}u|, penalizes the length of the object edges. They show that {integral}|{del}u|{sup p}, 0 < p < 1, only penalizes edges of dimension at least 2-p, and thus finite-length edges not at all. We give numerical examples showing the resulting improvement in shape preservation.
ERIC Educational Resources Information Center
German, Senta; Harris, Jim
2017-01-01
In this article, the authors argue that the art-historical canon, however it is construed, has little relevance to the selection of objects for museum-based teaching. Their contention is that all objects are fundamentally agile and capable of interrogation from any number of disciplinary standpoints, and that the canon of museum education,…
NASA Technical Reports Server (NTRS)
Olczak, Eugene G. (Inventor)
2011-01-01
An objective lens and a method for using same. The objective lens has a first end, a second end, and a plurality of optical elements. The optical elements are positioned between the first end and the second end and are at least substantially symmetric about a plane centered between the first end and the second end.
ERIC Educational Resources Information Center
Hanover School System, MA.
This statement of educational objectives was produced during the 1972-73 school year by the cooperative efforts of the teaching staff of the Hanover School System, Hanover, Massachusetts. The objectives were formulated by teachers working as a total group and in 13 committees: Health, Business, Music, Vocational Education, Reading, Mathematics,…
ERIC Educational Resources Information Center
Hodgkin, Robin A.
1988-01-01
Reflecting on obsessional play objects of infants, Hodgkin suggests that a proper understanding of these "transitional" or "cognitive" objects could lead to an educational model of a "learner" involving a number of human competencies, all developing synergistically. Contends that such a model may be truer to life than…
Extending ALE3D, an Arbitrarily Connected hexahedral 3D Code, to Very Large Problem Size (U)
Nichols, A L
2010-12-15
As the number of compute units increases on the ASC computers, the prospect of running previously unimaginably large problems is becoming a reality. In an arbitrarily connected 3D finite element code, like ALE3D, one must provide a unique identification number for every node, element, face, and edge. This is required for a number of reasons, including defining the global connectivity array required for domain decomposition, identifying appropriate communication patterns after domain decomposition, and determining the appropriate load locations for implicit solvers, for example. In most codes, the unique identification number is defined as a 32-bit integer. Thus the maximum value available is 231, or roughly 2.1 billion. For a 3D geometry consisting of arbitrarily connected hexahedral elements, there are approximately 3 faces for every element, and 3 edges for every node. Since the nodes and faces need id numbers, using 32-bit integers puts a hard limit on the number of elements in a problem at roughly 700 million. The first solution to this problem would be to replace 32-bit signed integers with 32-bit unsigned integers. This would increase the maximum size of a problem by a factor of 2. This provides some head room, but almost certainly not one that will last long. Another solution would be to replace all 32-bit int declarations with 64-bit long long declarations. (long is either a 32-bit or a 64-bit integer, depending on the OS). The problem with this approach is that there are only a few arrays that actually need to extended size, and thus this would increase the size of the problem unnecessarily. In a future computing environment where CPUs are abundant but memory relatively scarce, this is probably the wrong approach. Based on these considerations, we have chosen to replace only the global identifiers with the appropriate 64-bit integer. The problem with this approach is finding all the places where data that is specified as a 32-bit integer needs to be
Nonlinear inversion for arbitrarily-oriented anisotropic models II: Inversion techniques
NASA Astrophysics Data System (ADS)
Bremner, P. M.; Panning, M. P.
2011-12-01
We present output models from inversion of a synthetic surface wave dataset. We implement new 3-D finite-frequency kernels, based on the Born approximation, to invert for upper mantle structure beneath western North America. The kernels are formulated based on a hexagonal symmetry with an arbitrary orientation. Numerical tests were performed to achieve a robust inversion scheme. Four synthetic input models were created, to include: isotropic, constant strength anisotropic, variable strength anisotropic, and both anisotropic and isotropic together. The reference model was a simplified version of PREM (dubbed PREM LIGHT) in which the crust and 220 km discontinuity have been removed. Output models from inversions of calculated synthetic data are compared against these input models to test for accurate reproduction of input model features, and the resolution of those features. The object of this phase of the study was to determine appropriate nonlinear inversion schemes that adequately recover the input models. The synthetic dataset consists of collected seismic waveforms of 126 earthquake mechanisms, of magnitude 6-7 from Dec 2006 to Feb 2009, from the IRIS database. Events were selected to correlate with USArray deployments, and to have as complete an azimuthal coverage as possible. The events occurred within a circular region of radius 150o centered about 44o lat, -110o lon (an arbitrary location within USArray coverage). Synthetic data were calculated utilizing a spectral element code (SEM) coupled to a normal mode solution. The mesh consists of a 3-D heterogeneous outer shell, representing the upper mantle above 450 km depth, coupled to a spherically symmetric inner sphere. From the synthetic dataset, multi-taper fundamental mode surface wave phase delay measurements are taken. The orthogonal 2.5π -prolate spheroidal wave function eigentapers (Slepian tapers) reduce noise biasing, and can provide error estimates in phase delay measurements. This study is a
Set Size, Individuation, and Attention to Shape
ERIC Educational Resources Information Center
Cantrell, Lisa; Smith, Linda B.
2013-01-01
Much research has demonstrated a shape bias in categorizing and naming solid objects. This research has shown that when an entity is conceptualized as an individual object, adults and children attend to the object's shape. Separate research in the domain of numerical cognition suggest that there are distinct processes for quantifying small and…
Epstein, Ariel; Wong, Joseph P. S.; Eleftheriades, George V.
2016-01-01
One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators. PMID:26790605
Perolat, P; Merien, F; Ellis, W A; Baranton, G
1994-08-01
Leptospira serovar hardjo isolates of the hardjoprajitno and hardjobovis genotypes were characterized by ribotyping, arbitrarily primed PCR (AP-PCR) fingerprinting, and the study of mapped restriction site polymorphisms (MRSPs) in rrs and rrl genes. After restriction of chromosomal DNA with BglII, EcoRI, or HindIII, each genotype was individualized with a distinct ribotype. The fingerprints produced by AP-PCR with seven primers clearly separated the two groups; primers KF and RSP produced species-specific products which assigned hardjoprajitno and hardjobovis isolates to the species L. interrogans sensu stricto and L. borgpetersenii, respectively. Furthermore, AP-PCR fingerprints gave evidence of a considerable genomic heterogeneity at the strain level among the hardjobovis group. Conversely, the hardjoprajitno group was homogeneous. MRSP profiles in ribosomal genes indicated that hardjoprajitno and hardjobovis isolates belonged to L. interrogans MRSP group B and L. borgpetersenii group C, respectively. AP-PCR and determination of MRSPs in ribosomal genes proved to be quick and reliable methods for typing Leptospira strains and for studying intraspecific population structures.
NASA Astrophysics Data System (ADS)
Comastri, S. A.; Perez, Liliana I.; Pérez, Gervasio D.; Bastida, K.; Martin, G.
2008-04-01
The wavefront aberration of any image forming system and, in particular, of a human eye, is often expanded in Zernike modes each mode being weighed by a coefficient that depends both on the image forming components of the system and on the contour, size and centering of the pupil. In the present article, expanding up to 7th order the wavefront aberration, an analytical method to compute a new set of Zernike coefficients corresponding to a pupil in terms of an original set evaluated via ray tracing for a dilated and transversally arbitrarily displaced pupil is developed. A transformation matrix of dimension 36×36 is attained multiplying the scaling-horizontal traslation matrix previously derived by appropriate rotation matrices. Multiplying the original coefficients by this transformation matrix, analytical formulas for each new coefficient are attained and supplied and, for the information concerning the wavefront aberration to be available, these formulas must be employed in cases in which the new pupil is contained in the original one. The use of these analytical formulas is exemplified applying them to study the effect of pupil contraction and/or decentering in 3 situations: calculation of corneal aberrations of a keratoconic subject for the natural photopic pupil size and various decenterings; coma compensation by means of pupil shift in a fictitious system solely having primary aberrations and evaluation of the amount of astigmatism and coma of a hypothetical system originally having spherical aberration alone.
NASA Astrophysics Data System (ADS)
YOUNG, P. G.
2000-11-01
A three-dimensional shell theory is presented which is applicable to doubly curved thick open shells which are arbitrarily deep (have a large side-length to radius of curvature ratio) in one principal direction but are shallow in the other direction. The strain-displacement equations for the proposed “deep-shallow” shell theory are expressed in Cartesian co-ordinates and the limits of applicability of these equations are discussed. These equations are then used in a Ritz variational formulation with algebraic polynomials as trial functions to solve for the natural frequencies of a number of doubly curved shell problems. A novel approach is also proposed in which penalty functions are introduced to enforce continuity of displacements at two opposite ends of a shell of rectangular platform, increasing the range of problems which can be treated to include closed shells, such as cylinders, barrels, cooling-tower-type structures, toroids, rings, etc. (a sub-class of shells of revolution).
Askar`yan, G.A.; Batanov, G.M.; Barkhudarov, A.E.; Gritsinin, S.I.; Korchagina, E.G.; Kossyi, I.A.; Silakov, V.P.; Tarasova, N.M.
1992-09-01
It is proposed to use intense microwave beams to cleanse the atmospheric pool of freon contaminants (CF{sub 2}Cl{sub 2}, CFCl{sub 3}, etc.), which act destructively on the earth`s ozone layer. The possibility of exciting an arbitrarily located microwave discharge in the troposphere is considered. A relation is established between the amount of freon destroyed and the discharge parameters, the energy expended for this purpose is estimated, and the possible undesirable consequences of the associated phenomena (e.g., the formation of nitrogen oxides) are analyzed. The mechanism of dissociative attachment of electrons produced in the cold decaying plasma of the pulsed microwave discharge is assumed to be the main mechanism leading to the dissociation of chlorofluorocarbons. Results are presented from a model laboratory experiment, in which the efficiency with which freon impurities are dissociated under the action of the discharge excited in air by a beam of high-power microwave radiation is studied under conditions close to those in free space. The results of the experiment are consistent with the conclusions that follow from analyzing the elementary processes responsible for destruction of the freon components. 32 refs., 7 figs.
Epstein, Ariel; Wong, Joseph P S; Eleftheriades, George V
2016-01-21
One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators.
Louie, M; Jayaratne, P; Luchsinger, I; Devenish, J; Yao, J; Schlech, W; Simor, A
1996-01-01
Fifty-one clinical isolates of Listeria monocytogenes (15 isolates from two outbreaks and 36 epidemiologically unrelated isolates) were typed by conventional serotyping, ribotyping (RT), pulsed-field gel electrophoresis (PFGE), and arbitrarily primed PCR (AP-PCR). Serotyping was unable to distinguish between related and unrelated strains of L. monocytogenes. Each of the three molecular methods showed excellent typeability and reproducibility. Restriction with EcoRI and PvuII gave 16 and 23 RT patterns, respectively. Restriction with ApaI or SmaI generated 22 and 26 PFGE profiles, respectively. ApaI profiles were easier to interpret, with 10 to 15 bands each, while SmaI profiles had 15 to 20 bands each. AP-PCR with two different primers yielded 29 and 31 randomly amplified polymorphic DNA patterns, respectively. Strains from the same outbreak shared concordant patterns by each of the three methods. Of the three techniques evaluated, RT was the least discriminating and could not distinguish between strains from the two outbreaks. The abilities of AP-PCR and PFGE to differentiate between strains were comparable. However, AP-PCR was more rapid and easier to perform. We conclude that the DNA profiles generated by either AP-PCR or PFGE can be used to differentiate outbreak strains from epidemiologically unrelated strains and to clearly identify unrelated strains as being distinct from one another. We recommend that at least two independent primers be used for AP-PCR typing in order to improve its discriminatory power. PMID:8748263
1998-07-31
The advantage in utilizing 15 shape-memory cables made of Nitinol for size reduction of the remote control actuator system is 1 Fi well suited for...a submarine environment because of its non-magnetic and corrosion resistance 17 properties. Use of thermoelastic Nitinol introduces other...problems because of the cooling and 18 resetting properties of Nitinol cables. It is therefore an important object of the present invention 19 on to