Effects of Specular Highlights on Perceived Surface Convexity
Adams, Wendy J.; Elder, James H.
2014-01-01
Shading is known to produce vivid perceptions of depth. However, the influence of specular highlights on perceived shape is unclear: some studies have shown that highlights improve quantitative shape perception while others have shown no effect. Here we ask how specular highlights combine with Lambertian shading cues to determine perceived surface curvature, and to what degree this is based upon a coherent model of the scene geometry. Observers viewed ambiguous convex/concave shaded surfaces, with or without highlights. We show that the presence/absence of specular highlights has an effect on qualitative shape, their presence biasing perception toward convex interpretations of ambiguous shaded objects. We also find that the alignment of a highlight with the Lambertian shading modulates its effect on perceived shape; misaligned highlights are less likely to be perceived as specularities, and thus have less effect on shape perception. Increasing the depth of the surface or the slant of the illuminant also modulated the effect of the highlight, increasing the bias toward convexity. The effect of highlights on perceived shape can be understood probabilistically in terms of scene geometry: for deeper objects and/or highly slanted illuminants, highlights will occur on convex but not concave surfaces, due to occlusion of the illuminant. Given uncertainty about the exact object depth and illuminant direction, the presence of a highlight increases the probability that the surface is convex. PMID:24811069
Turbulent boundary layer on a convex, curved surface
NASA Technical Reports Server (NTRS)
Gillis, J. C.; Johnston, J. P.; Kays, W. M.; Moffat, R. J.
1980-01-01
The effects of strong convex curvature on boundary layer turbulence were investigated. The data gathered on the behavior of Reynolds stress suggested the formulation of a simple turbulence model. Three sets of data were taken on two separate facilities. Both rigs had flow from a flat surface, over a convex surface with 90 deg of turning, and then onto a flat recovery surface. The geometry was adjusted so that, for both rigs, the pressure gradient along the test surface was zero - thus avoiding any effects of streamwise acceleration on the wall layers. Results show that after a sudden introduction of curvature, the shear stress in the outer part of the boundary layer is sharply diminished and is even slightly negative near the edge. The wall shear also drops off quickly downstream. In contrast, when the surface suddenly becomes flat again, the wall shear and shear stress profiles recover very slowly towards flat wall conditions.
Matthews, Harold; Hill, Harold; Palmisano, Stephen
2012-01-01
Evidence suggests that experiencing the hollow-face illusion involves perceptual reversal of the binocular disparities associated with the face even though the rest of the scene appears unchanged. This suggests stereoscopic processing of object shape may be independent of scene-based processing of the layout of objects in depth. We investigated the effects of global scene-based and local object-based disparity on the compellingness of the perceived convexity of the face. We took stereoscopic photographs of people in scenes, and independently reversed the binocular disparities associated with the head and scene. Participants rated perceived convexity of a natural disparity ("convex") or reversed disparity ("concave") face shown either in its original context with reversed or natural disparities or against a black background. Faces with natural disparity were rated as more convincingly convex independent of the background, showing that the local disparities can affect perceived convexity independent of disparities across the rest of the image. However, the apparent convexity of the faces was also greater in natural disparity scenes compared to either a reversed disparity scene or a zero disparity black background. This independent effect of natural scene disparity suggests that the 'solidity' associated with natural scene disparities spread to enhance the perceived convexity of the face itself. Together, these findings suggest that global and local disparity exert independent and additive effects upon the perceived convexity of the face. PMID:22670345
Monodispersed Spray Generation from Convex Surfaces
NASA Astrophysics Data System (ADS)
Shroff, Shilpa; Liepmann, Dorian
1999-11-01
Flow of a fluid sheet over a concave surface has been found to amplify streamwise vorticity leading to a new mechanism for droplet formation. An instability leading to waves that travel in the streamwise direction is also observed. The resultant grid-like structure produces monodispersed droplets at the intersections of the two instabilities as the flow develops. The presentation will focus on the dominant physics associated with the interaction between the solid surface and the fluid sheet and discuss how these control the formation of the droplets. The cross-stream ridges result from a wave instability that depends on the curvature of the bed and the Froude Number. There has been some analytical work done on determining the stability characteristic of flow in curved beds by Eagles, which indicates a weak instability even at Reynolds numbers approaching zero. The possibility of streamwise vortices was also investigated as the source of the streamwise ridges. This vorticity may be introduced into the flow by the angle between the jet and the sheet during the initial contact. An analytic model as well as experimental work has been developed to determine the physical phenomena that influence the dynamics of this flow. In addition, work has been done to identify important scaling parameters, especially those that control the development of the surface deformation and droplet formation.
Approximating convex Pareto surfaces in multiobjective radiotherapy planning
Craft, David L.; Halabi, Tarek F.; Shih, Helen A.; Bortfeld, Thomas R.
2006-09-15
Radiotherapy planning involves inherent tradeoffs: the primary mission, to treat the tumor with a high, uniform dose, is in conflict with normal tissue sparing. We seek to understand these tradeoffs on a case-to-case basis, by computing for each patient a database of Pareto optimal plans. A treatment plan is Pareto optimal if there does not exist another plan which is better in every measurable dimension. The set of all such plans is called the Pareto optimal surface. This article presents an algorithm for computing well distributed points on the (convex) Pareto optimal surface of a multiobjective programming problem. The algorithm is applied to intensity-modulated radiation therapy inverse planning problems, and results of a prostate case and a skull base case are presented, in three and four dimensions, investigating tradeoffs between tumor coverage and critical organ sparing.
Discrete-hole film cooling characteristics over concave and convex surfaces
NASA Astrophysics Data System (ADS)
Ko, Shao-Yen; Yao, Yong-Qing; Xia, Bin; Tsou, Fu-Kang
The local film-cooling effectiveness and local pressure distribution for single-row discrete holes were measured over the whole areas of concave and convex surfaces, using a plexiglass test section with curvature radii of 140 mm and 70 mm for the concave and the convex surfaces and film-cooling holes (34 on the convex surface and 22 on the concave surface) 8 mm in diameter. The results indicate that the concave surface has the widest film-cooling coverage area in the z-direction (perpendicular to the x-flow direction), while the highest film-cooling effectiveness of the convex surface is near the ejection hole. High blowing ratios at holes have an adverse effect on film cooling. The weakest cooling region is near the center line between holes; such a poorly cooled region is larger on convex surfaces than on the concave ones. Optimal design characteristics for turbine blades surfaces are discussed.
Pitt, K G; Newton, J M; Stanley, P
1991-04-01
The porosity and tensile strength of convex-faced aspirin tablets formed under a compaction pressure in the range 40-320 MPa and at punch velocities in the range 0.008 to 500 mm s-1 have been determined. The material tensile strength, sigma f, was calculated from the observed fracture load, Ps, using the equation of Pitt et al (1988): sigma f = 10 Ps/pi D2(2.84 t/D - 0.126 t/W + 3.15 W/D + 0.01)-1 where D is the tablet diameter, t is the overall tablet thickness and W is the central cylinder thickness. Tablets formed at lower compaction pressures had a higher porosity and lower tensile strength than those formed at higher compaction pressures. Tablets of face curvature ratio (D/R) in the range 0.25-0.67 and a normalized cylinder length (W/D) of 0.2 had the optimum tensile strength. (R is the radius of curvature of the tablet face.) Tablets formed at high compaction rates were significantly weaker than those formed at lower compaction rates. PMID:1676731
Rationally convex domains and singular Lagrangian surfaces in $mathbb {C}(2) $ C 2
NASA Astrophysics Data System (ADS)
Nemirovski, Stefan; Siegel, Kyler
2016-01-01
We give a complete characterization of those disk bundles over surfaces which embed as rationally convex strictly pseudoconvex domains in $\\mathbb{C}^2$. We recall some classical obstructions and prove some deeper ones related to symplectic and contact topology. We explain the close connection to Lagrangian surfaces with isolated singularities and develop techniques for constructing such surfaces. Our proof also gives a complete characterization of Lagrangian surfaces with open Whitney umbrellas, answering a question first posed by Givental in 1986.
NASA Technical Reports Server (NTRS)
Wang, T.; Simon, T. W.
1987-01-01
The test section of the present experiment to ascertain the effects of convex curvature and freestream turbulence on boundary layer momentum and heat transfer during natural transition provided a two-dimensional boundary layer flow on a uniformly heated curved surface, with bending to various curvature radii, R. Attention is given to results for the cases of R = infinity, 180 cm, and 90 cm, each with two freestream turbulence intensity levels. While the mild convex curvature of R = 180 cm delays transition, further bending to R = 90 cm leads to no signifucant further delay of transition. Cases with both curvature and higher freestream disturbance effects exhibit the latter's pronounced dominance. These data are pertinent to the development of transition prediction models for gas turbine blade design.
A simple device for sub-aperture stitching of fast convex surfaces
NASA Astrophysics Data System (ADS)
Aguirre-Aguirre, D.; Izazaga-Pérez, R.; Villalobos-Mendoza, B.; Carrasco-Licea, E.; Granados-Agustin, F. S.; Percino-Zacarías, M. E.; Salazar-Morales, M. F.; Cruz-Zavala, E.
2015-10-01
In this work, we show a simple device that helps in the use of the sub-aperture stitching method for testing convex surfaces with large diameter and a small f/#. This device was designed at INAOE's Optical work shop to solve the problem that exists when a Newton Interferometer and the sub-aperture stitching method are used. It is well known that if the f/# of a surface is small, the slopes over the surface increases rapidly and this is critical for points far from the vertex. Therefore, if we use a reference master in the Newton interferometer to test a convex surface with a large diameter and an area far from the vertex, the master tends to slide causing scratches over the surface under test. To solve this problem, a device for mounting the surface under test with two freedom degrees, a rotating axis and a lever to tilt the surface, was designed. As result, the optical axis of the master can be placed in vertical position avoiding undesired movements of the master and making the sub-aperture stitching easier. We describe the proposed design and the results obtained with this device.
Experimental data and model for the turbulent boundary layer on a convex, curved surface
NASA Technical Reports Server (NTRS)
Gillis, J. C.; Johnson, J. P.; Moffat, R. J.; Kays, W. M.
1981-01-01
Experiments were performed to determine how boundary layer turbulence is affected by strong convex curvature. The data gathered on the behavior of the Reynolds stress suggested the formulation of a simple turbulence model. Data were taken on two separate facilities. Both rigs had flow from a flat surface, over a convex surface with 90 deg of turning and then onto a flat recovery surface. The geometry was adjusted so that, for both rigs, the pressure gradient along the test surface was zero. Two experiments were performed at delta/R approximately 0.10, and one at weaker curvature with delta/R approximately 0.05. Results show that after a sudden introduction of curvature the shear stress in the outer part of the boundary layer is sharply diminished and is even slightly negative near the edge. The wall shear also drops off quickly downstream. When the surface suddenly becomes flat again, the wall shear and shear stress profiles recover very slowly towards flat wall conditions. A simple turbulence model, which was based on the theory that the Prandtl mixing length in the outer layer should scale on the velocity gradient layer, was shown to account for the slow recovery.
NASA Astrophysics Data System (ADS)
Jha, R. M.; Wiesbeck, W.
1995-04-01
A generalized approach to analytical surface-ray tracing in three dimensions, and a review of its application to convex conducting bodies, is presented, using the Eisenhart Coordinate System. The ray-parameters so obtained, for quadric cylinders (QUACYLs) and surfaces of revolution (QUASORs), are in a one-parameter form for UTD mutual-coupling applications. The ray analysis is also extended to the hybrid QUACYLs (e.g., aircraft wings) and hybrid QUASORs (e.g., satellite-launch vehicles), by introducing Hertz's principle of particle dynamics to EM theory. This mathematical formulation is applicable even to other important non-Eisenhart surfaces, such as the ogive. A summary of the mathematical formulations is included.
NASA Astrophysics Data System (ADS)
Dave, Nikunj
Direct numerical simulation results are used to establish the effect of streamwise convex surface curvature on the development of turbulent boundary layers, and the effect of such curvature on the forced-convection heat transfer variations observed at certain supercritical thermodynamic states. The results illustrate the stabilizing effects of this flow geometry through modification of the structure and distribution of hairpin-like vortical flow structures in the boundary layer. Specifically, the radial equilibrium mechanism existing on the streamwise convex surface acts to decrease the streamwise spacing of hairpin-like structures within a wave packet and increase the spanwise spacing of the hairpin-like structures in comparison to the behaviour of such structures within the boundary layer on a flat surface. Furthermore, enhancement of convective heat transfer realized at a particular heat flux-to-mass flux ratio with the working fluid at a supercritical thermodynamic state is observed to be reduced by the stabilizing effect of convex surface curvature.
Advanced Face Gear Surface Durability Evaluations
NASA Technical Reports Server (NTRS)
Lewicki, David G.; Heath, Gregory F.
2016-01-01
The surface durability life of helical face gears and isotropic super-finished (ISF) face gears was investigated. Experimental fatigue tests were performed at the NASA Glenn Research Center. Endurance tests were performed on 10 sets of helical face gears in mesh with tapered involute helical pinions, and 10 sets of ISF-enhanced straight face gears in mesh with tapered involute spur pinions. The results were compared to previous tests on straight face gears. The life of the ISF configuration was slightly less than that of previous tests on straight face gears. The life of the ISF configuration was slightly greater than that of the helical configuration.
Streamwise Vortices on the Convex Surfaces of Circular Cylinders and Turbomachinery Blading
NASA Technical Reports Server (NTRS)
Gostelow, Paul
2010-01-01
In assessing the results please recall that the Mach number regimes and model geometries differ considerably. Selection of the radius of curvature at the 10% chord location is consistent but arbitrary, although it does seem representative for most blades and gives a good fit for the results. Measured spanwise wavelengths of the periodic vortex arrays on blading are predicted well by the Kestin and Wood theory. If this behavior is at all common it could have implications for turbine aerodynamic and blade cooling design. The outcome is to establish that organized streamwise vorticity may occur more frequently on convex surfaces, such as turbine blade suction surfaces, than hitherto appreciated. Investigations and predictions of flow behavior should be extended to encompass that possibility.
Smart, passive sun facing surfaces
Hively, Lee M.
1996-01-01
An article adapted for selectively utilizing solar radiation comprises an absorptive surface and a reflective surface, the absorptive surface and the reflective surface oriented to absorb solar radiation when the sun is in a relatively low position, and to reflect solar radiation when the sun is in a relatively high position.
Smart, passive sun facing surfaces
Hively, L.M.
1996-04-30
An article adapted for selectively utilizing solar radiation comprises an absorptive surface and a reflective surface, the absorptive surface and the reflective surface oriented to absorb solar radiation when the sun is in a relatively low position, and to reflect solar radiation when the sun is in a relatively high position. 17 figs.
Fiber coupler end face wavefront surface metrology
NASA Astrophysics Data System (ADS)
Compertore, David C.; Ignatovich, Filipp V.; Marcus, Michael A.
2015-09-01
Despite significant technological advances in the field of fiber optic communications, one area remains surprisingly `low-tech': fiber termination. In many instances it involves manual labor and subjective visual inspection. At the same time, high quality fiber connections are one of the most critical parameters in constructing an efficient communication link. The shape and finish of the fiber end faces determines the efficiency of a connection comprised of coupled fiber end faces. The importance of fiber end face quality becomes even more critical for fiber connection arrays and for in the field applications. In this article we propose and demonstrate a quantitative inspection method for the fiber connectors using reflected wavefront technology. The manufactured and polished fiber tip is illuminated by a collimated light from a microscope objective. The reflected light is collected by the objective and is directed to a Shack-Hartmann wavefront sensor. A set of lenses is used to create the image of the fiber tip on the surface of the sensor. The wavefront is analyzed by the sensor, and the measured parameters are used to obtain surface properties of the fiber tip, and estimate connection loss. For example, defocus components in the reflected light indicate the presence of bow in the fiber end face. This inspection method provides a contact-free approach for quantitative inspection of fiber end faces and for estimating the connection loss, and can potentially be integrated into a feedback system for automated inspection and polishing of fiber tips and fiber tip arrays.
NASA Astrophysics Data System (ADS)
Mahata, Paritosh; Das, Sovan Lal
2014-12-01
Adsorption of proteins on membrane surfaces plays an important role in cell biological processes. In this work, we develop a two-dimensional fluid model for proteins. The protein molecules have been modeled as two-dimensional convex and soft particles. The Lennard-Jones potential for circular particles and Kihara (12,6) potential for elliptical particles with hard core have been used to model pairwise intermolecular interactions. The equation of state of the fluid model has been derived using Weeks-Chandler-Andersen decomposition and it involves three parameters, an attraction, a repulsion, and a size parameter, which depend on the shape and core size of the molecules. For validation of the model, a two-dimensional molecular dynamics simulation has been performed. Finally, the model has been applied to study the adsorption of proteins on a flat membrane. In comparison with the existing model of hard and convex particles for protein adsorption, our model predicts a higher packing fraction for the adsorption equilibria. Although the present work is based on Lennard-Jones-type interaction, it can be extended for other specific soft interactions between convex molecules. Thus the model has general applicability for any other two-dimensional adsorption systems of molecules with soft interaction.
Mehrotra, Sanjay; Papp, Dávid
2014-01-01
We present and analyze a central cutting surface algorithm for general semi-infinite convex optimization problems and use it to develop a novel algorithm for distributionally robust optimization problems in which the uncertainty set consists of probability distributions with given bounds on their moments. Moments of arbitrary order, as well as nonpolynomial moments, can be included in the formulation. We show that this gives rise to a hierarchy of optimization problems with decreasing levels of risk-aversion, with classic robust optimization at one end of the spectrum and stochastic programming at the other. Although our primary motivation is to solve distributionally robust optimization problems with moment uncertainty, the cutting surface method for general semi-infinite convex programs is also of independent interest. The proposed method is applicable to problems with nondifferentiable semi-infinite constraints indexed by an infinite dimensional index set. Examples comparing the cutting surface algorithm to the central cutting plane algorithm of Kortanek and No demonstrate the potential of our algorithm even in the solution of traditional semi-infinite convex programming problems, whose constraints are differentiable, and are indexed by an index set of low dimension. After the rate of convergence analysis of the cutting surface algorithm, we extend the authors' moment matching scenario generation algorithm to a probabilistic algorithm that finds optimal probability distributions subject to moment constraints. The combination of this distribution optimization method and the central cutting surface algorithm yields a solution to a family of distributionally robust optimization problems that are considerably more general than the ones proposed to date.
Mehrotra, Sanjay; Papp, Dávid
2014-01-01
We present and analyze a central cutting surface algorithm for general semi-infinite convex optimization problems and use it to develop a novel algorithm for distributionally robust optimization problems in which the uncertainty set consists of probability distributions with given bounds on their moments. Moments of arbitrary order, as well as nonpolynomial moments, can be included in the formulation. We show that this gives rise to a hierarchy of optimization problems with decreasing levels of risk-aversion, with classic robust optimization at one end of the spectrum and stochastic programming at the other. Although our primary motivation is to solve distributionally robustmore » optimization problems with moment uncertainty, the cutting surface method for general semi-infinite convex programs is also of independent interest. The proposed method is applicable to problems with nondifferentiable semi-infinite constraints indexed by an infinite dimensional index set. Examples comparing the cutting surface algorithm to the central cutting plane algorithm of Kortanek and No demonstrate the potential of our algorithm even in the solution of traditional semi-infinite convex programming problems, whose constraints are differentiable, and are indexed by an index set of low dimension. After the rate of convergence analysis of the cutting surface algorithm, we extend the authors' moment matching scenario generation algorithm to a probabilistic algorithm that finds optimal probability distributions subject to moment constraints. The combination of this distribution optimization method and the central cutting surface algorithm yields a solution to a family of distributionally robust optimization problems that are considerably more general than the ones proposed to date.« less
Sadeghi, Mohammad Hossein; Hassanpour, Hamed
2014-01-01
Advancement in machining technology of curved surfaces for various engineering applications is increasing. Various methodologies and computer tools have been developed by the manufacturers to improve efficiency of freeform surface machining. Selection of the right sets of cutter path strategies and appropriate cutting conditions is extremely important in ensuring high productivity rate, meeting the better quality level, and lower cutting forces. In this paper, cutting force as a new decision criterion for the best selection of tool paths on convex surfaces is presented. Therefore, this work aims at studying and analyzing different finishing strategies to assess their influence on surface texture, cutting forces, and machining time. Design and analysis of experiments are performed by means of Taguchi technique and analysis of variance. In addition, the significant parameters affecting the cutting force in each strategy are introduced. Machining strategies employed include raster, 3D-offset, radial, and spiral. The cutting parameters were feed rate, cutting speed, and step over. The experiments were carried out on low curvature convex surfaces of stainless steel 1.4903. The conclusion is that radial strategy provokes the best surface texture and the lowest cutting forces and spiral strategy signifies the worst surface texture and the highest cutting forces. PMID:24701163
Shajari, Shaghayegh; Sadeghi, Mohammad Hossein; Hassanpour, Hamed
2014-01-01
Advancement in machining technology of curved surfaces for various engineering applications is increasing. Various methodologies and computer tools have been developed by the manufacturers to improve efficiency of freeform surface machining. Selection of the right sets of cutter path strategies and appropriate cutting conditions is extremely important in ensuring high productivity rate, meeting the better quality level, and lower cutting forces. In this paper, cutting force as a new decision criterion for the best selection of tool paths on convex surfaces is presented. Therefore, this work aims at studying and analyzing different finishing strategies to assess their influence on surface texture, cutting forces, and machining time. Design and analysis of experiments are performed by means of Taguchi technique and analysis of variance. In addition, the significant parameters affecting the cutting force in each strategy are introduced. Machining strategies employed include raster, 3D-offset, radial, and spiral. The cutting parameters were feed rate, cutting speed, and step over. The experiments were carried out on low curvature convex surfaces of stainless steel 1.4903. The conclusion is that radial strategy provokes the best surface texture and the lowest cutting forces and spiral strategy signifies the worst surface texture and the highest cutting forces. PMID:24701163
ERIC Educational Resources Information Center
Alexandrov, V. A.
1998-01-01
Discusses some questions connected with Cauchy's theorem which states that two convex closed polyhedral surfaces whose corresponding faces are congruent and whose faces adjoin each other in the same way are congruent. Describes how to construct a flexible polyhedron. (ASK)
Tensile property of H13 die steel with convex-shaped biomimetic surface
NASA Astrophysics Data System (ADS)
Zhang, Z. H.; Zhou, H.; Ren, L. Q.; Tong, X.; Shan, H. Y.; Cao, Y.
2007-09-01
The H13 steel specimens with non-smooth surface were fabricated by biomimetic method and laser technique, and the effect of these biomimetic surfaces on the tensile properties was investigated. The results indicated that the biomimetic surface has an advantageous effect on improving the tensile properties of H13 steel. As the area ratio occupied by non-smooth units on the biomimetic surface grows to 26.7%, the ultimate tensile strength (UTS) and 0.2% yield strength (YS) of materials linearly increase by about 8.4% and 17.2%, respectively. The elongation to fracture of materials reaches to the peak value of about 41.3% at the point of 17.1% area ratio, and further heightening the area ratio can result in a reduced ductility relative to this peak value. This improvement of tensile properties can be attributed to the combined effects of the microstructure characteristics within the unit zone and the unit-distribution features on the surface. Meanwhile, the regressed relation equations of UTS, YS and elongation regarding the area ratio were obtained via statistical theory. The tests of regression significance showed that the confidence of these equations achieved 99% above.
ERIC Educational Resources Information Center
Scott, Paul
2006-01-01
A "convex" polygon is one with no re-entrant angles. Alternatively one can use the standard convexity definition, asserting that for any two points of the convex polygon, the line segment joining them is contained completely within the polygon. In this article, the author provides a solution to a problem involving convex lattice polygons.
NASA Technical Reports Server (NTRS)
Syed, H. H.; Volakis, John L.
1992-01-01
Asymptotic/high-frequency solutions are developed for analyzing the non-specular scattering mechanisms associated with coated convex surfaces and edges simulated by approximate boundary conditions. In particular, the standard impedance boundary conditions (SIBC's) and the second order generalized impedance boundary conditions (GIBC's) are employed for a characterization of the edge diffraction, creeping wave, and surface diffracted wave contributions. To study the creeping wave and surface diffracted wave mechanisms, rigorous UTD (uniform geometrical theory of diffraction) diffraction coefficients are developed for a convex coated cylinder simulated with SIBC's and GIBC's. The ray solutions obtained remain valid in the transition region and reduce uniformly to those in the deep lit and shadow regions. A uniform asymptotic solution is also presented for observations in the close vicinity of the cylinder. The diffraction coefficient for a convex cylinder are obtained via a generalization of the corresponding ones of the circular cylinder. To validate the asymptotic/high-frequency solution, integral equations are derived for both E and H-polarization and solved numerically using the method of moments. Results are presented for a single and three layered coated convex cylinder. Some insights are also provided on the accuracy of the employed GIBC's versus SIBC's for application to curved surfaces. To characterize the scattering by impedance wedges illuminated at skew incidence, diffraction coefficients are derived from an approximate solution of the governing functional difference equations. This solution exactly recovers the known ones for an impedance half plane or an arbitrary wedge at normal incidence, and to validate it for other wedge angles, a moment method code was used. Finally, to test the usefulness of the approximate skew incidence impedance wedge diffraction coefficient for three dimensional structures, equivalent currents are derived in the context of the
3D face recognition based on matching of facial surfaces
NASA Astrophysics Data System (ADS)
Echeagaray-Patrón, Beatriz A.; Kober, Vitaly
2015-09-01
Face recognition is an important task in pattern recognition and computer vision. In this work a method for 3D face recognition in the presence of facial expression and poses variations is proposed. The method uses 3D shape data without color or texture information. A new matching algorithm based on conformal mapping of original facial surfaces onto a Riemannian manifold followed by comparison of conformal and isometric invariants computed in the manifold is suggested. Experimental results are presented using common 3D face databases that contain significant amount of expression and pose variations.
RDS-21 Face-Gear Surface Durability Tests
NASA Technical Reports Server (NTRS)
Lewicki, David G.; Heath, Gregory F.; Filler, Robert R.; Slaughter, Stephen C.; Fetty, Jason
2007-01-01
Experimental fatigue tests were performed to determine the surface durability life of a face gear in mesh with a tapered spur involute pinion. Twenty-four sets of gears were tested at three load levels: 7200, 8185, and 9075 lb-in face gear torque, and 2190 to 3280 rpm face gear speed. The gears were carburized and ground, shot-peened and vibro-honed, and made from VIM-VAR Pyrowear 53 steel per AMS 6308. The tests produced 17 gear tooth spalling failures and 7 suspensions. For all the failed sets, spalling occurred on at least one tooth of all the pinions. In some cases, the spalling initiated a crack in the pinion teeth which progressed to tooth fracture. Also, spalling occurred on some face gear teeth. The AGMA endurance allowable stress for a tapered spur involute pinion in mesh with a face gear was determined to be 275 ksi for the material tested. For the application of a tapered spur involute pinion in mesh with a face gear, proper face gear shim controlled the desired gear tooth contact pattern while proper pinion shim was an effective way of adjusting backlash without severely affecting the contact pattern.
NASA Technical Reports Server (NTRS)
Tennille, Geoffrey M.; Howser, Lona M.
1993-01-01
The use of the CONVEX computers that are an integral part of the Supercomputing Network Subsystems (SNS) of the Central Scientific Computing Complex of LaRC is briefly described. Features of the CONVEX computers that are significantly different than the CRAY supercomputers are covered, including: FORTRAN, C, architecture of the CONVEX computers, the CONVEX environment, batch job submittal, debugging, performance analysis, utilities unique to CONVEX, and documentation. This revision reflects the addition of the Applications Compiler and X-based debugger, CXdb. The document id intended for all CONVEX users as a ready reference to frequently asked questions and to more detailed information contained with the vendor manuals. It is appropriate for both the novice and the experienced user.
Observations of quenching of downward-facing surfaces
Chu, T.Y.; Bainbridge, B.L.; Bentz, J.H.; Simpson, R.B.
1994-01-01
This report documents results of a series of scoping experiments on boiling from downward-facing surfaces in support of the Sandia New Production Reactor, Vessel-Pool Boiling Heat Transfer task. Quenching experiments have been performed to examine the boiling processes from downward-facing surfaces using two 61-centimeter diameter test masses, one with a flat test surface and one with a curved test surface having a radius of curvature of 335 cm, matching that of the Cylindrical Boiling facility test vessel. Boiling curves were obtained for both test surfaces facing horizontally downward. The critical beat flux was found to be essentially the same, having an average value of approximately 0.5 MW/m{sup 2}. This value is substantially higher than current estimates of the heat dissipation rates required for in-vessel retention of core debris in the Heavy Water New Production Reactor as well as some of the advanced light water reactors under design. The nucleate boiling process was found to be cyclic with four relatively distinct phases: direct liquid/solid contact, nucleation and growth of bubbles, coalescence, and ejection.
Plasma Facing Surface Composition During NSTX Li Experiments
Skinner, C. H.; Sullenberger, R.; Koel, B. E.; Jaworski, M. A.; Kugel, H. W.
2012-07-20
Lithium conditioned plasma facing surfaces have lowered recycling and enhanced plasma performance on many fusion devices. However, the nature of the plasma-lithium surface interaction has been obscured by the difficulty of in-tokamak surface analysis. We report laboratory studies of the chemical composition of lithium surfaces exposed to typical residual gases found in tokamaks. Solid lithium and a molybdenum alloy (TZM) coated with lithium has been examined using x-ray photoelectron spectroscopy, temperature programmed desorption, and Auger electron spectroscopy both in ultrahigh vacuum conditions and after exposure to trace gases. Lithium surfaces near room temperature were oxidized after exposure to 1-2 Langmuirs of oxygen or water vapor. The oxidation rate by carbon monoxide was four times less. Lithiated PFC surfaces in tokamaks will be oxidized in about 100 s depending on the tokamak vacuum conditions.
ERIC Educational Resources Information Center
Hodge, Jonathan K.; Marshall, Emily; Patterson, Geoff
2010-01-01
Convexity-based measures of shape compactness provide an effective way to identify irregularities in congressional district boundaries. A low convexity coefficient may suggest that a district has been gerrymandered, or it may simply reflect irregularities in the corresponding state boundary. Furthermore, the distribution of population within a…
Stereotype locally convex spaces
NASA Astrophysics Data System (ADS)
Akbarov, S. S.
2000-08-01
We give complete proofs of some previously announced results in the theory of stereotype (that is, reflexive in the sense of Pontryagin duality) locally convex spaces. These spaces have important applications in topological algebra and functional analysis.
Generalized convexity and inequalities
NASA Astrophysics Data System (ADS)
Anderson, G. D.; Vamanamurthy, M. K.; Vuorinen, M.
2007-11-01
Let and let be the family of all mean values of two numbers in (some examples are the arithmetic, geometric, and harmonic means). Given , we say that a function is (m1,m2)-convex if f(m1(x,y))[less-than-or-equals, slant]m2(f(x),f(y)) for all . The usual convexity is the special case when both mean values are arithmetic means. We study the dependence of (m1,m2)-convexity on m1 and m2 and give sufficient conditions for (m1,m2)-convexity of functions defined by Maclaurin series. The criteria involve the Maclaurin coefficients. Our results yield a class of new inequalities for several special functions such as the Gaussian hypergeometric function and a generalized Bessel function.
NASA Astrophysics Data System (ADS)
Nakai, Yasuharu; Nakao, Takeshi; Nishiyama, Kenji; Kadota, Michio
2009-07-01
The transition bandwidth of 20 MHz between the transmission (Tx: 1850-1910 MHz) and the receiving (Rx: 1930-1990 MHz) bands of personal communication service (PCS) handy phones in the United States (US) is very narrow compared with those of other systems. We have already realized surface acoustic wave (SAW) duplexers with sizes of 5.0×5.0×1.7 and 3.0×2.5×1.2 mm3 for PCS handy phones in the US with an excellent temperature coefficient of frequency (TCF) by using a shear horizontal (SH) wave on a flattened SiO2/Cu electrode/36-48° YX-LiTaO3 structure and a Rayleigh wave on a SiO2/Cu electrode/120-128° YX-LiNbO3 structure. Although the surface of the above-mentioned structures is flattened SiO2, we have also studied the shape of the SiO2 surface. As a result, in addition to increasing the stop-band width, which corresponds to the reflection coefficient, the TCF and power durability have been improved by forming convex portions on the surface of the SiO2 over the interdigital transducer (IDT) gaps.
Optical metrology for very large convex aspheres
NASA Astrophysics Data System (ADS)
Burge, J. H.; Su, P.; Zhao, C.
2008-07-01
Telescopes with very large diameter or with wide fields require convex secondary mirrors that may be many meters in diameter. The optical surfaces for these mirrors can be manufactured to the accuracy limited by the surface metrology. We have developed metrology systems that are specifically optimized for measuring very large convex aspheric surfaces. Large aperture vibration insensitive sub-aperture Fizeau interferometer combined with stitching software give high resolution surface measurements. The global shape is corroborated with a coordinate measuring machine based on the swing arm profilometer.
Computing convex quadrangulations☆
Schiffer, T.; Aurenhammer, F.; Demuth, M.
2012-01-01
We use projected Delaunay tetrahedra and a maximum independent set approach to compute large subsets of convex quadrangulations on a given set of points in the plane. The new method improves over the popular pairing method based on triangulating the point set. PMID:22389540
Statistical properties of convex clustering
Tan, Kean Ming; Witten, Daniela
2016-01-01
In this manuscript, we study the statistical properties of convex clustering. We establish that convex clustering is closely related to single linkage hierarchical clustering and k-means clustering. In addition, we derive the range of the tuning parameter for convex clustering that yields a non-trivial solution. We also provide an unbiased estimator of the degrees of freedom, and provide a finite sample bound for the prediction error for convex clustering. We compare convex clustering to some traditional clustering methods in simulation studies.
Convex geometry analysis method of hyperspectral data
NASA Astrophysics Data System (ADS)
Gong, Yanjun; Wang, XiChang; Qi, Hongxing; Yu, BingXi
2003-06-01
We present matrix expression of convex geometry analysis method of hyperspectral data by linear mixing model and establish a mathematic model of endmembers. A 30-band remote sensing image is applied to testify the model. The results of analysis reveal that the method can analyze mixed pixel questions. The targets that are smaller than earth surface pixel can be identified by applying the method.
Localized surface plasmons in face to face dimer silver triangular prism nanoparticles
NASA Astrophysics Data System (ADS)
Azarian, Abas; Babaei, Ferydon
2016-05-01
Using the discrete dipole approximation method, all plasmonic bands in 80 nm silver face to face dimer triangular prism nanoparticles were reported. The characteristics of plasmonics peaks were investigated with variations of dimer gap and refractive index of the surrounding medium of dimer. We found that there are three and four plasmonic bands, respectively, for dimer separation 2 and 4 nm. The extinction spectra and electric field distribution showed that the dipole-dipole interaction creates strong plasmonic band, but the quadrupole-quadrupole interaction relates to weak plasmonic band. The results revealed that the strong plasmonic bands have high sensitivity factors with respect to weak plasmonic bands. This study may be used in the synthesis of asymmetric dimers made of metal nanoparticles with new plasmonics properties.
Effects of surface materials on polarimetric-thermal measurements: applications to face recognition.
Short, Nathaniel J; Yuffa, Alex J; Videen, Gorden; Hu, Shuowen
2016-07-01
Materials, such as cosmetics, applied to the face can severely inhibit biometric face-recognition systems operating in the visible spectrum. These products are typically made up of materials having different spectral properties and color pigmentation that distorts the perceived shape of the face. The surface of the face emits thermal radiation, due to the living tissue beneath the surface of the skin. The emissivity of skin is approximately 0.99; in comparison, oil- and plastic-based materials, commonly found in cosmetics and face paints, have an emissivity range of 0.9-0.95 in the long-wavelength infrared part of the spectrum. Due to these properties, all three are good thermal emitters and have little impact on the heat transferred from the face. Polarimetric-thermal imaging provides additional details of the face and is also dependent upon the thermal radiation from the face. In this paper, we provide a theoretical analysis on the thermal conductivity of various materials commonly applied to the face using a metallic sphere. Additionally, we observe the impact of environmental conditions on the strength of the polarimetric signature and the ability to recover geometric details. Finally, we show how these materials degrade the performance of traditional face-recognition methods and provide an approach to mitigating this effect using polarimetric-thermal imaging. PMID:27409214
Plasma temperature rise toward the plasma-facing surface
NASA Astrophysics Data System (ADS)
Nishijima, D.; Doerner, R. P.; Seraydarian, R. P.; De Temmerman, G.; van der Meiden, H. J.
2015-08-01
Detailed measurements of axial electron temperature, Te, profiles in the presheath region were carried out using a Langmuir probe and the line intensity ratio technique for both He I (728.1 nm/706.5 nm) and Be II (467.3 nm/313.1 nm). The results show that Te increases toward the material surface, which contradicts the standard picture that Te is constant along the magnetic field in the sheath-limited regime. While no target bias voltage, Vb, dependence is seen, the Te rise becomes more prominent with decreasing neutral pressure. Similarly, the ion temperature, Ti, evaluated from Doppler broadening of a He II line emission at 468.6 nm is found to increase toward the surface, but also does not depend on Vb. Possible mechanisms of the Te and Ti rise as well as validity of the line intensity ratio technique near the material surface are discussed.
Thermal expansion compensator having an elastic conductive element bonded to two facing surfaces
NASA Technical Reports Server (NTRS)
Determan, William (Inventor); Matejczyk, Daniel Edward (Inventor)
2012-01-01
A thermal expansion compensator is provided and includes a first electrode structure having a first surface, a second electrode structure having a second surface facing the first surface and an elastic element bonded to the first and second surfaces and including a conductive element by which the first and second electrode structures electrically and/or thermally communicate, the conductive element having a length that is not substantially longer than a distance between the first and second surfaces.
More Realistic Face Model Surface Improves Relevance of Pediatric In-Vitro Aerosol Studies
Amirav, Israel; Halamish, Asaf; Gorenberg, Miguel; Omar, Hamza; Newhouse, Michael T.
2015-01-01
Background Various hard face models are commonly used to evaluate the efficiency of aerosol face masks. Softer more realistic “face” surface materials, like skin, deform upon mask application and should provide more relevant in-vitro tests. Studies that simultaneously take into consideration many of the factors characteristic of the in vivo face are lacking. These include airways, various application forces, comparison of various devices, comparison with a hard-surface model and use of a more representative model face based on large numbers of actual faces. Aim To compare mask to “face” seal and aerosol delivery of two pediatric masks using a soft vs. a hard, appropriately representative, pediatric face model under various applied forces. Methods Two identical face models and upper airways replicas were constructed, the only difference being the suppleness and compressibility of the surface layer of the “face.” Integrity of the seal and aerosol delivery of two different masks [AeroChamber (AC) and SootherMask (SM)] were compared using a breath simulator, filter collection and realistic applied forces. Results The soft “face” significantly increased the delivery efficiency and the sealing characteristics of both masks. Aerosol delivery with the soft “face” was significantly greater for the SM compared to the AC (p< 0.01). No statistically significant difference between the two masks was observed with the hard “face.” Conclusions The material and pliability of the model “face” surface has a significant influence on both the seal and delivery efficiency of face masks. This finding should be taken into account during in-vitro aerosol studies. PMID:26090661
Surface reconstruction and graphene formation on face-to-face 6H-SiC at 2000 ^oC
NASA Astrophysics Data System (ADS)
Elmquist, Randolph E.; Real, Mariano; Bush, Brian G.; Shen, Tian; Stiles, Mark D.; Lass, Eric A.
2012-02-01
Improved epitaxial graphene films have been widely reported when the sublimation rate of Si is reduced by ambient Ar gas, vapor phase silane, or confined Si vapor. We describe graphene growth on (0001) 6H-SiC samples annealed ``face-to-face'' [1]; in our modified method the separation is limited only by the flatness of the surfaces. After annealing in 100 kPa Ar gas at 2000 ^oC for 300 s, atomic force microscopy (AFM) and electrostatic force microscopy (EFM) show graphene coverage is typically between one and a few layers. Samples without prior hydrogen etching undergo surface reconstruction in the graphitization process, resulting in atomically flat terraces with step bunching. Estimates of the sequestered carbon in the form of graphene are compared to calculated levels due to sublimation and diffusion rates where the sublimated gas is dominated by Si atoms below 2100 ^oC. The 2000 ^oC samples are contrasted against samples processed between 1700 ^oC and 1900 ^oC and transport results on large-scale graphene devices are presented.[4pt] [1] X.Z Yu, C.G. Hwang, C.M. Jozwiak, A. Kohl, A.K. Schmid and A. Lanzara, New synthesis method for the growth of epitaxial graphene, Journal of Electron Spectroscopy and Related Phenomena 184 (2011) 100-106.
Surface Stereo Imager on Mars, Face-On
NASA Technical Reports Server (NTRS)
2008-01-01
This image is a view of NASA's Phoenix Mars Lander's Surface Stereo Imager (SSI) as seen by the lander's Robotic Arm Camera. This image was taken on the afternoon of the 116th Martian day, or sol, of the mission (September 22, 2008). The mast-mounted SSI, which provided the images used in the 360 degree panoramic view of Phoenix's landing site, is about 4 inches tall and 8 inches long. The two 'eyes' of the SSI seen in this image can take photos to create three-dimensional views of the landing site.
The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.
Convex polytopes and quantum separability
NASA Astrophysics Data System (ADS)
Holik, F.; Plastino, A.
2011-12-01
We advance a perspective of the entanglement issue that appeals to the Schlienz-Mahler measure [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.52.4396 52, 4396 (1995)]. Related to it, we propose a criterium based on the consideration of convex subsets of quantum states. This criterium generalizes a property of product states to convex subsets (of the set of quantum states) that is able to uncover an interesting geometrical property of the separability property.
Convex polytopes and quantum separability
Holik, F.; Plastino, A.
2011-12-15
We advance a perspective of the entanglement issue that appeals to the Schlienz-Mahler measure [Phys. Rev. A 52, 4396 (1995)]. Related to it, we propose a criterium based on the consideration of convex subsets of quantum states. This criterium generalizes a property of product states to convex subsets (of the set of quantum states) that is able to uncover an interesting geometrical property of the separability property.
Computing Surface Coordinates Of Face-Milled Spiral-Bevel Gear Teeth
NASA Technical Reports Server (NTRS)
Handschuh, Robert F.; Litvin, Faydor L.
1995-01-01
Surface coordinates of face-milled spiral-bevel gear teeth computed by method involving numerical solution of governing equations. Needed to generate mathematical models of tooth surfaces for use in finite-element analyses of stresses, strains, and vibrations in meshing spiral-bevel gears.
Three-dimensional clustering of Janus cylinders by convex curvature and hydrophobic interactions.
Kim, Jongmin; Oh, Myung Seok; Choi, Chang-Hyung; Kang, Sung-Min; Kwak, Moo Jin; You, Jae Bem; Im, Sung Gap; Lee, Chang-Soo
2015-06-28
The three-dimensional (3D) clustering of Janus cylinders is controlled by simply tuning the cylinder geometry and hydrophobic interactions. Janus cylinders were prepared by combining two approaches: micromolding and initiated chemical vapor deposition (iCVD). Hydrophilic cylinders with a flat- or convex-top curvature were prepared by micromolding based on surface tension-induced flow. The iCVD process then provides a hydrophobic domain through the simple and precise deposition of a polymer film on the top surface, forming monodisperse Janus microcylinders. We use these Janus cylinders as building blocks to form 2D or 3D clusters via hydrophobic interactions in methanol. We investigate how cylinder geometry or degree of hydrophobic interaction affects the resulting cluster geometries. The convex-top Janus cylinders lead to 3D clustering through tip-to-tip interactions, and the flat-top Janus cylinders lead to 2D clustering through face-to-face attraction. The number of Janus cylinders in 3D clusters is tuned by controlling the degree of hydrophobic (or hydrophilic) interaction. PMID:26008176
Thermodynamic study of reconstructed crystal surfaces.. The octopolar (111) face of LiF crystals
NASA Astrophysics Data System (ADS)
Rubbo, Marco; Bruno, Marco; Prencipe, Mauro
2015-02-01
Dipolar crystal faces, although reconstructed, have a high surface energy and are forbidden in a Wulff plot at 0 K, in a vacuum. However, they do grow far from equilibrium and due to the relatively open surface structure, are eligible for adsorption, epitaxy and incorporation of foreign substances. In this paper, we study the surface structure of the (111) dipolar face of LiF and calculate the thermal contribution to the surface energy, in the harmonic limit at the Hartree-Fock level. The surface energy calculated at 0 K, of the Li and F terminated (111) faces are 0.767 and 0.698 J/m2, respectively. When the vibrational energy and entropy are considered the surface energies at 298.15 K decrease to 0.720 (Li terminated) and 0.670 (F terminated) J/m2. Finally, when the configurational entropy is also taken into account, the surface energies are 0.663 (Li terminated) and 0.612 (F terminated) J/m2.
Convex dynamics: Unavoidable difficulties in bounding some greedy algorithms
NASA Astrophysics Data System (ADS)
Nowicki, Tomasz; Tresser, Charles
2004-03-01
A greedy algorithm for scheduling and digital printing with inputs in a convex polytope, and vertices of this polytope as successive outputs, has recently been proven to be bounded for any convex polytope in any dimension. This boundedness property follows readily from the existence of some invariant region for a dynamical system equivalent to the algorithm, which is what one proves. While the proof, and some constructions of invariant regions that can be made to depend on a single parameter, are reasonably simple for convex polygons in the plane, the proof of boundedness gets quite complicated in dimension three and above. We show here that such complexity is somehow justified by proving that the most natural generalization of the construction that works for polygons does not work in any dimension above two, even if we allow for as many parameters as there are faces. We first prove that some polytopes in dimension greater than two admit no invariant region to which they are combinatorially equivalent. We then modify these examples to get polytopes such that no invariant region can be obtained by pushing out the borders of the half spaces that intersect to form the polytope. We also show that another mechanism prevents some simplices (the simplest polytopes in any dimension) from admitting invariant regions to which they would be similar. By contrast in dimension two, one can always get an invariant region by pushing these borders far enough in some correlated way; for instance, pushing all borders by the same distance builds an invariant region for any polygon if the push is at a distance big enough for that polygon. To motivate the examples that we provide, we discuss briefly the bifurcations of polyhedra associated with pushing half spaces in parallel to themselves. In dimension three, the elementary codimension one bifurcation resembles the unfolding of the elementary degenerate singularity for codimension one foliations on surfaces. As the subject of this
Convex dynamics: unavoidable difficulties in bounding some greedy algorithms.
Nowicki, Tomasz; Tresser, Charles
2004-03-01
A greedy algorithm for scheduling and digital printing with inputs in a convex polytope, and vertices of this polytope as successive outputs, has recently been proven to be bounded for any convex polytope in any dimension. This boundedness property follows readily from the existence of some invariant region for a dynamical system equivalent to the algorithm, which is what one proves. While the proof, and some constructions of invariant regions that can be made to depend on a single parameter, are reasonably simple for convex polygons in the plane, the proof of boundedness gets quite complicated in dimension three and above. We show here that such complexity is somehow justified by proving that the most natural generalization of the construction that works for polygons does not work in any dimension above two, even if we allow for as many parameters as there are faces. We first prove that some polytopes in dimension greater than two admit no invariant region to which they are combinatorially equivalent. We then modify these examples to get polytopes such that no invariant region can be obtained by pushing out the borders of the half spaces that intersect to form the polytope. We also show that another mechanism prevents some simplices (the simplest polytopes in any dimension) from admitting invariant regions to which they would be similar. By contrast in dimension two, one can always get an invariant region by pushing these borders far enough in some correlated way; for instance, pushing all borders by the same distance builds an invariant region for any polygon if the push is at a distance big enough for that polygon. To motivate the examples that we provide, we discuss briefly the bifurcations of polyhedra associated with pushing half spaces in parallel to themselves. In dimension three, the elementary codimension one bifurcation resembles the unfolding of the elementary degenerate singularity for codimension one foliations on surfaces. As the subject of this
3D face recognition using simulated annealing and the surface interpenetration measure.
Queirolo, Chauã C; Silva, Luciano; Bellon, Olga R P; Segundo, Maurício Pamplona
2010-02-01
This paper presents a novel automatic framework to perform 3D face recognition. The proposed method uses a Simulated Annealing-based approach (SA) for range image registration with the Surface Interpenetration Measure (SIM), as similarity measure, in order to match two face images. The authentication score is obtained by combining the SIM values corresponding to the matching of four different face regions: circular and elliptical areas around the nose, forehead, and the entire face region. Then, a modified SA approach is proposed taking advantage of invariant face regions to better handle facial expressions. Comprehensive experiments were performed on the FRGC v2 database, the largest available database of 3D face images composed of 4,007 images with different facial expressions. The experiments simulated both verification and identification systems and the results compared to those reported by state-of-the-art works. By using all of the images in the database, a verification rate of 96.5 percent was achieved at a False Acceptance Rate (FAR) of 0.1 percent. In the identification scenario, a rank-one accuracy of 98.4 percent was achieved. To the best of our knowledge, this is the highest rank-one score ever achieved for the FRGC v2 database when compared to results published in the literature. PMID:20075453
Convex analysis and ideal tensegrities
NASA Astrophysics Data System (ADS)
Maceri, Franco; Marino, Michele; Vairo, Giuseppe
2011-11-01
A theoretical framework based on convex analysis is formulated and developed to study tensegrity structures under steady-state loads. Many classical results for ideal tensegrities are rationally deduced from subdifferentiable models in a novel mechanical perspective. Novel energy-based criteria for rigidity and pre-stressability are provided, allowing to formulate numerical algorithms for computations.
Computational redesign of the lipid-facing surface of the outer membrane protein OmpA
Stapleton, James A.; Whitehead, Timothy A.; Nanda, Vikas
2015-01-01
Advances in computational design methods have made possible extensive engineering of soluble proteins, but designed β-barrel membrane proteins await improvements in our understanding of the sequence determinants of folding and stability. A subset of the amino acid residues of membrane proteins interact with the cell membrane, and the design rules that govern this lipid-facing surface are poorly understood. We applied a residue-level depth potential for β-barrel membrane proteins to the complete redesign of the lipid-facing surface of Escherichia coli OmpA. Initial designs failed to fold correctly, but reversion of a small number of mutations indicated by backcross experiments yielded designs with substitutions to up to 60% of the surface that did support folding and membrane insertion. PMID:26199411
NASA Astrophysics Data System (ADS)
Horsky, Thomas Neil
Low energy positron diffraction (LEPD) is used to determine the surface structure of the wurtzite CdSe(1010) and CdSe(1120) cleavage faces. Low energy electron diffraction (LEED) is also performed, utilizing a beam optical system which produces both a e^+ and e ^- beam with the same phase-space characteristics, i.e. 1 mm-deg. Both e^+ and e^- measurements were collected from the same sample surface of each cleavage face, removing systematic errors from the comparison. Dynamical calculations were performed for both the LEPD and LEED using the R-factor methodology of Duke et al. For the (1010) surface, the calculations and analyses were performed at Brandeis via link to the John Von Neumann Supercomputer Center at Princeton, NJ. For the (1120) surface, the LEPD calculations and analysis was performed by Battelle Pacific Northwest Laboratories, while the LEED calculations were performed by Princeton University. Resulting surface structures for CdSe(1010) are in accord with the proposed reconstruction model of Wang and Duke, indicating a bond-length-conserving rotation of the surface dimer. The best-fit values of the bond-rotation angle omega are 15^circ +/- 5^circ as determined by LEPD and omega = 21.5^ circ +/- 4^ circ as determined by LEED. These values are in agreement with the predicted value of omega = 17^circ. For CdSe(1120), the best-fit LEPD results indicate an omega of 27^circ +/- 7^circ while preliminary LEED results indicate an omega of 35^circ +/- 5^circ. Both values for this previously undetermined surface are also in agreement with the theoretically predicted value of omega = 32^circ . These results serve to confirm a universal model of reconstruction which describes the surface structures of both the zincblende and wurtzite compound semiconductor cleavage faces.
Revisiting separation properties of convex fuzzy sets
Technology Transfer Automated Retrieval System (TEKTRAN)
Separation of convex sets by hyperplanes has been extensively studied on crisp sets. In a seminal paper separability and convexity are investigated, however there is a flaw on the definition of degree of separation. We revisited separation on convex fuzzy sets that have level-wise (crisp) disjointne...
Convex lens-induced nanoscale templating
Berard, Daniel J.; Michaud, François; Mahshid, Sara; Ahamed, Mohammed Jalal; McFaul, Christopher M. J.; Leith, Jason S.; Bérubé, Pierre; Sladek, Rob; Reisner, Walter; Leslie, Sabrina R.
2014-01-01
We demonstrate a new platform, convex lens-induced nanoscale templating (CLINT), for dynamic manipulation and trapping of single DNA molecules. In the CLINT technique, the curved surface of a convex lens is used to deform a flexible coverslip above a substrate containing embedded nanotopography, creating a nanoscale gap that can be adjusted during an experiment to confine molecules within the embedded nanostructures. Critically, CLINT has the capability of transforming a macroscale flow cell into a nanofluidic device without the need for permanent direct bonding, thus simplifying sample loading, providing greater accessibility of the surface for functionalization, and enabling dynamic manipulation of confinement during device operation. Moreover, as DNA molecules present in the gap are driven into the embedded topography from above, CLINT eliminates the need for the high pressures or electric fields required to load DNA into direct-bonded nanofluidic devices. To demonstrate the versatility of CLINT, we confine DNA to nanogroove and nanopit structures, demonstrating DNA nanochannel-based stretching, denaturation mapping, and partitioning/trapping of single molecules in multiple embedded cavities. In particular, using ionic strengths that are in line with typical biological buffers, we have successfully extended DNA in sub–30-nm nanochannels, achieving high stretching (90%) that is in good agreement with Odijk deflection theory, and we have mapped genomic features using denaturation analysis. PMID:25092333
Convex Lens-Induced Nanoscale Templating
NASA Astrophysics Data System (ADS)
Berard, Daniel; Michaud, Francois; McFaul, Christopher; Mahsid, Sara; Reisner, Walter; Leslie, Sabrina
2014-03-01
We demonstrate a new platform, ``Convex Lens-Induced Nanoscale Templating'' (CLINT), for dynamic manipulation and trapping of single DNA molecules. In the CLINT technique, the curved surface of a convex lens is used to deform a flexible coverslip above a substrate containing embedded nanotopography, creating a nanoscale gap that can be adjusted during an experiment to confine molecules within the embedded nanostructures. Critically, CLINT has the capability of actively transforming a macroscale flow-cell into a nanofluidic device without need for high-temperature direct bonding, leading to ease of sample loading and greater accessibility of the surface. Moreover, as DNA molecules present in the gap will be driven into the embedded topography from above, CLINT eliminates the need for the high pressures or electric fields necessitated by direct bonded nanofluidic devices for loading DNA in the confined structures. To demonstrate the versatility of CLINT, we confine DNA to nanogroove structures, demonstrating DNA nanochannel-based stretching. Using ionic strengths that are in line with typical biological buffers, we have successfully extended DNA in sub 30nm nanochannels, achieving high stretching (90%) that is in good agreement with Odijk deflection theory.
Convex accelerated maximum entropy reconstruction
NASA Astrophysics Data System (ADS)
Worley, Bradley
2016-04-01
Maximum entropy (MaxEnt) spectral reconstruction methods provide a powerful framework for spectral estimation of nonuniformly sampled datasets. Many methods exist within this framework, usually defined based on the magnitude of a Lagrange multiplier in the MaxEnt objective function. An algorithm is presented here that utilizes accelerated first-order convex optimization techniques to rapidly and reliably reconstruct nonuniformly sampled NMR datasets using the principle of maximum entropy. This algorithm - called CAMERA for Convex Accelerated Maximum Entropy Reconstruction Algorithm - is a new approach to spectral reconstruction that exhibits fast, tunable convergence in both constant-aim and constant-lambda modes. A high-performance, open source NMR data processing tool is described that implements CAMERA, and brief comparisons to existing reconstruction methods are made on several example spectra.
Evaluating convex roof entanglement measures.
Tóth, Géza; Moroder, Tobias; Gühne, Otfried
2015-04-24
We show a powerful method to compute entanglement measures based on convex roof constructions. In particular, our method is applicable to measures that, for pure states, can be written as low order polynomials of operator expectation values. We show how to compute the linear entropy of entanglement, the linear entanglement of assistance, and a bound on the dimension of the entanglement for bipartite systems. We discuss how to obtain the convex roof of the three-tangle for three-qubit states. We also show how to calculate the linear entropy of entanglement and the quantum Fisher information based on partial information or device independent information. We demonstrate the usefulness of our method by concrete examples. PMID:25955038
Convex Diffraction Grating Imaging Spectrometer
NASA Technical Reports Server (NTRS)
Chrisp, Michael P. (Inventor)
1999-01-01
A 1:1 Offner mirror system for imaging off-axis objects is modified by replacing a concave spherical primary mirror that is concentric with a convex secondary mirror with two concave spherical mirrors M1 and M2 of the same or different radii positioned with their respective distances d1 and d2 from a concentric convex spherical diffraction grating having its grooves parallel to the entrance slit of the spectrometer which replaces the convex secondary mirror. By adjusting their distances d1 and d2 and their respective angles of reflection alpha and beta, defined as the respective angles between their incident and reflected rays, all aberrations are corrected without the need to increase the spectrometer size for a given entrance slit size to reduce astigmatism, thus allowing the imaging spectrometer volume to be less for a given application than would be possible with conventional imaging spectrometers and still give excellent spatial and spectral imaging of the slit image spectra over the focal plane.
Simulated plasma facing component measurements for an in situ surface diagnostic on Alcator C-Mod
Hartwig, Z. S.; Whyte, D. G.
2010-10-15
The ideal in situ plasma facing component (PFC) diagnostic for magnetic fusion devices would perform surface element and isotope composition measurements on a shot-to-shot ({approx}10 min) time scale with {approx}1 {mu}m depth and {approx}1 cm spatial resolution over large areas of PFCs. To this end, the experimental adaptation of the customary laboratory surface diagnostic - nuclear scattering of MeV ions - to the Alcator C-Mod tokamak is being guided by ACRONYM, a Geant4 synthetic diagnostic. The diagnostic technique and ACRONYM are described, and synthetic measurements of film thickness for boron-coated PFCs are presented.
Simulated plasma facing component measurements for an in situ surface diagnostic on Alcator C-Moda)
NASA Astrophysics Data System (ADS)
Hartwig, Z. S.; Whyte, D. G.
2010-10-01
The ideal in situ plasma facing component (PFC) diagnostic for magnetic fusion devices would perform surface element and isotope composition measurements on a shot-to-shot (˜10 min) time scale with ˜1 μm depth and ˜1 cm spatial resolution over large areas of PFCs. To this end, the experimental adaptation of the customary laboratory surface diagnostic—nuclear scattering of MeV ions—to the Alcator C-Mod tokamak is being guided by ACRONYM, a Geant4 synthetic diagnostic. The diagnostic technique and ACRONYM are described, and synthetic measurements of film thickness for boron-coated PFCs are presented.
Convex-profile inversion of asteroid lightcurves - Theory and applications
NASA Technical Reports Server (NTRS)
Ostro, Steven J.; Connelly, Robert; Dorogi, Mark
1988-01-01
A theory for asteroid light curve interpretation is derived from the reformulation, extension, and calibration of Ostro and Connely's (1984) convex-profile inversion, and then used to constrain the shapes of selected asteroids. The ideal conditions for the estimation of an asteroid's main cross-section from a light curve are (1) that the viewing-illumination geometry be equatorial, (2) that the scattering be uniform and geometric, (3) that the asteroid surface contours parallel to the equatorial plane be convex, (4) and that the solar angle not equal zero. Results are presented from simulations calibrating the kind, severity, and predictability of systematic errors.
High-speed surface temperature measurements on plasma facing materials for fusion applications
Araki, M.; Kobayashi, M.
1996-01-01
For the lifetime evaluation of plasma facing materials in fusion experimental machines, it is essential to investigate their surface behavior and their temperature responses during an off-normal event such as the plasma disruptions. An infrared thermometer with a sampling speed as fast as 1{times}10{sup {minus}6} s/data, namely, the high-speed infrared thermometer (HSIR), has been developed by the National Research Laboratory of Metrology in Japan. To evaluate an applicability of the newly developed HSIR on the surface temperature measurement of plasma facing materials, high heat flux beam irradiation experiments have been performed with three different materials under the surface heat fluxes up to 170 MW/m{sup 2} for 0.04 s in a hydrogen ion beam test facility at the Japan Atomic Energy Research Institute. As for the results, HSIR can be applicable for measuring the surface temperature responses of the armor tile materials with a little modification. It is also confirmed that surface temperatures measured with the HSIR thermometer show good agreement with the analytical results for stainless steel and carbon based materials at a temperature range of up to 2500{degree}C. However, for aluminum the HSIR could measure the temperature of the high dense vapor cloud which was produced during the heating due to lower melting temperature. Based on the result, a multichannel arrayed HSIR thermometer has been designed and fabricated. {copyright} {ital 1996 American Institute of Physics.}
Molecular Graphics of Convex Body Fluids.
Gabriel, Adrian T; Meyer, Timm; Germano, Guido
2008-03-01
Coarse-grained modeling of molecular fluids is often based on nonspherical convex rigid bodies like ellipsoids or spherocylinders representing rodlike or platelike molecules or groups of atoms, with site-site interaction potentials depending both on the distance among the particles and the relative orientation. In this category of potentials, the Gay-Berne family has been studied most extensively. However, conventional molecular graphics programs are not designed to visualize such objects. Usually the basic units are atoms displayed as spheres or as vertices in a graph. Atomic aggregates can be highlighted through an increasing amount of stylized representations, e.g., Richardson ribbon diagrams for the secondary structure of proteins, Connolly molecular surfaces, density maps, etc., but ellipsoids and spherocylinders are generally missing, especially as elementary simulation units. We fill this gap providing and discussing a customized OpenGL-based program for the interactive, rendered representation of large ensembles of convex bodies, useful especially in liquid crystal research. We pay particular attention to the performance issues for typical system sizes in this field. The code is distributed as open source. PMID:26620787
NASA Astrophysics Data System (ADS)
Salazar-Camacho, Carlos; Villalobos, Mario
2010-04-01
We developed a model that describes quantitatively the arsenate adsorption behavior for any goethite preparation as a function of pH and ionic strength, by using one basic surface arsenate stoichiometry, with two affinity constants. The model combines a face distribution-crystallographic site density model for goethite with tenets of the Triple Layer and CD-MUSIC surface complexation models, and is self-consistent with its adsorption behavior towards protons, electrolytes, and other ions investigated previously. Five different systems of published arsenate adsorption data were used to calibrate the model spanning a wide range of chemical conditions, which included adsorption isotherms at different pH values, and adsorption pH-edges at different As(V) loadings, both at different ionic strengths and background electrolytes. Four additional goethite-arsenate systems reported with limited characterization and adsorption data were accurately described by the model developed. The adsorption reaction proposed is: lbond2 FeOH +lbond2 SOH +AsO43-+H→lbond2 FeOAsO3[2-]…SOH+HO where lbond2 SOH is an adjacent surface site to lbond2 FeOH; with log K = 21.6 ± 0.7 when lbond2 SOH is another lbond2 FeOH, and log K = 18.75 ± 0.9, when lbond2 SOH is lbond2 Fe 2OH. An additional small contribution of a protonated complex was required to describe data at low pH and very high arsenate loadings. The model considered goethites above 80 m 2/g as ideally composed of 70% face (1 0 1) and 30% face (0 0 1), resulting in a site density for lbond2 FeOH and for lbond2 Fe 3OH of 3.125/nm 2 each. Below 80 m 2/g surface capacity increases progressively with decreasing area, which was modeled by considering a progressively increasing proportion of faces (0 1 0)/(1 0 1), because face (0 1 0) shows a much higher site density of lbond2 FeOH groups. Computation of the specific proportion of faces, and thus of the site densities for the three types of crystallographic surface groups present in
Crack-face displacements for embedded elliptic and semi-elliptical surface cracks
NASA Technical Reports Server (NTRS)
Raju, I. S.
1989-01-01
Analytical expressions for the crack-face displacements of an embedded elliptic crack in infinite solid subjected to arbitrary tractions are obtained. The tractions on the crack faces are assumed to be expressed in a polynomial form. These displacements expressions complete the exact solution of Vijayakumar and Atluri, and Nishioki and Atluri. For the special case of an embedded crack in an infinite solid subjected to uniform pressure loading, the present displacements agree with those by Green and Sneddon. The displacement equations derived were used with the finite-element alternating method (FEAM) for the analysis of a semi-elliptic surface crack in a finite solid subjected to remote tensile loading. The maximum opening displacements obtained with FEAM are compared to those with the finite-element method with singularity elements. The maximum crack opening displacements by the two methods showed good agreement.
Effects of hydrogen surface processes on hydrogen retention in plasma facing components
NASA Astrophysics Data System (ADS)
Guterl, Jerome; Smirnov, Roman; Krasheninnikov, Sergei
2014-10-01
Hydrogen retention and recycling on metallic plasma-facing components (PFCs) are among the key-issues for future fusion devices due to both safety and operational reasons. For tungsten, which has been chosen as divertor material in ITER, parameters of hydrogen desorption from Wsurfaces, experimentally measured for fusion-related conditions, show a large discrepancy. Indeed, various complex phenomena may affect hydrogen desorption (e.g atomic islands, roughness, surface reconstruction, impurities, ect). In this work, we investigate effects of hydrogen desorption from W surfaces on hydrogen retention in W material. Two regimes of hydrogen surface desorption (readsorption-limited and recombination-limited) can be identified and may affect the kinetic order of desorption. Within these desorption regimes, it is shown that release of hydrogen from W material in fusion-related conditions may be surface-limited at low temperature and diffusion-limited at high temperature. Analyses of hydrogen release regimes for thermodesorption experiments and plasma operations in fusion reactors show that surface processes may strongly affect retention and release of hydrogen from W material. In this context, effects of W surface coverage with oxygen on hydrogen desorption are discussed since high concentrations of oxygen on PFCs surfaces are expected in future fusion devices. This work is performed under the auspices of USDOE Grant No. DE-FG02-04ER54739 and the PSI Science Center Grant DE-SC0001999 at UCSD.
NASA Astrophysics Data System (ADS)
Tseng, Huan-Wan
1998-07-01
In the first part of this work, a hybrid approach is developed, which combines the asymptotic high-frequency based uniform geometrical theory of diffraction (UTD) ray technique with a numerical method of moments (MM), to analyze the EM scattering of blade, slot, and composite slot-blade cavity backed antenna structures, respectively residing on the surface of electrically large circular cylinders. The MM is used to solve an integral equation formulation for the unknown equivalent current distributions over the blade and the slot. In that MM solution of the integral equation formulation, a UTD approximation for the dyadic Green's function for a perfectly conducting circular cylinder is employed to calculate the excitation vector by an incoming local plane wave. After these equivalent current distributions become known via the MM solutions, the UTD dyadic Green's functions are next also used to calculate the radiation from these equivalent current distributions in the presence of the circular cylinder. The UTD can describe the effects of the large cylinder in a rather simple closed form fashion while the MM is used essentially to deal with the much smaller blade and slot antennas which cannot directly be analyzed by the UTD. In the second part of this work, this hybrid MM/UTD technique is employed to analyze the radiation from a composite slot-blade cavity backed antenna located on realistic aircraft configurations. The excitation of the antenna is due to a delta gap generator in a thin-wire probe feed that is placed inside a rectangular cavity. The MM procedure is used first to solve coupled integral equations that are formulated for the unknown equivalent electric current distribution on the blade and the unknown equivalent magnetic current distribution on the slot, when this composite slot-blade antenna configuration resides on an infinite ground plane. Finally the UTD is used to efficiently and accurately calculate the radiation from these equivalent current
Natural and orbital debris particles on LDEF's trailing and forward-facing surfaces
NASA Technical Reports Server (NTRS)
Hoerz, Friedrich; See, Thomas H.; Bernhard, Ronald P.; Brownlee, Donald E.
1995-01-01
Approximately 1000 impact craters on the Chemistry of Meteoroid Experiment (CME) have been analyzed by means of Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDXA) to determine the compositional make-up of projectile residues. This report completes our systematic survey of gold and aluminum surfaces exposed at the trailing-edge (A03) and forward-facing (A11) LDEF sites, respectively. The major categories for the projectile residues were (1) natural, with diverse subgroups such as chondritic, monomineralic silicates, and sulfides, and (2) man made, that were classified into aluminum (metallic or oxide) and miscellaneous materials (such as stainless steel, paint flakes, etc). On CME gold collectors on LDEF's trailing edge approximately 11 percent of all craters greater than 100 micron in diameter were due to man-made debris, the majority (8.6 percent) caused by pure aluminum, approximately 31.4 percent were due to cosmic dust, while the remaining 58 percent were indeterminate via the analytical techniques utilized in this study. The aluminum surfaces located at the A11 forward-facing site did not permit analysis of aluminum impactors, but approximately 9.4 percent of all craters were demonstratably caused by miscellaneous debris materials and approximately 39.2 percent were the result of natural particles, leaving approximately 50 percent which were indeterminate. Model considerations and calculations are presented that focus on the crater-production rates for features greater than 100 micron in diameter, and on assigning the intermediate crater population to man-made or natural particles. An enhancement factor of 6 in the crater-production rate of natural impactors for the 'forward-facing' versus the 'trailing-edge' CME collectors was found to best explain all observations (i.e., total crater number(s), as well as their computational characteristics). Enhancement factors of 10 and 4 are either too high or too low. It is also suggested that
Moving-Surface Plasma-Facing Components for Particle Control in Steady State Magnetic Fusion Devices
Hirooka, Yoshi; Fukushima, Hoju; Ohno, Noriyasu; Takamura, Shuichi; Nishikawa, Masahiro
2004-01-15
This paper will report on the proof-of-principle (POP) experiments conducted to demonstrate reduced wall recycling, using a laboratory-scale test unit, constructed based on the concept of moving-surface plasma-facing component (MS-PFC). In this concept, the moving-surface exposed to edge plasmas in steady state magnetic fusion devices is continuously deposited ex-situ with a getter material, so that particle trapping capabilities can be regenerated prior to the subsequent exposure. In our previous paper, the construction details of the MS-PFC test unit and the first results in the case of titanium gettering was reported, but in the present paper preliminary results in the case of lithium gettering will be presented for comparison. Results indicate that the H{sub {alpha}} light intensity used as the measure of hydrogen recycling is reduced by {approx}6% due to titanium gettering and by {approx}12% due to lithium gettering, both at steady state.
Surface roughness of rock faces through the curvature of triangulated meshes
NASA Astrophysics Data System (ADS)
Lai, P.; Samson, C.; Bose, P.
2014-09-01
In this paper, we examine three different measures of roughness based on a geometric property of surfaces known as curvature. These methods were demonstrated using an image of a large rock face made up of a smooth blocky limestone in contact with a rough friable dolostone. The point cloud analysed contained 10,334,288 points and was acquired at a distance of 3 m from the rock face. The point cloud was first decimated using an epsilon-net and then meshed using the Poisson surface reconstruction method before the proposed measures of roughness were applied. The first measure of roughness is defined as the difference in curvature between a mesh and a smoothed version of the same mesh. The second measure of roughness is a voting system applied to each vertex which identifies the subset of vertices which represent rough regions within the mesh. The third measure of roughness uses a combination of spatial partitioning data structures and data clustering in order to define roughness for a region in the mesh. The spatial partitioning data structure allows for a hierarchy of roughness values which is related to the size of the region being considered. All of the proposed measures of roughness are visualised using colour-coded displays which allows for an intuitive interpretation.
2D surface temperature measurement of plasma facing components with modulated active pyrometry
Amiel, S.; Loarer, T.; Pocheau, C.; Roche, H.; Gauthier, E.; Aumeunier, M.-H.; Courtois, X.; Jouve, M.; Balorin, C.; Moncada, V.; Le Niliot, C.; Rigollet, F.
2014-10-01
In nuclear fusion devices, such as Tore Supra, the plasma facing components (PFC) are in carbon. Such components are exposed to very high heat flux and the surface temperature measurement is mandatory for the safety of the device and also for efficient plasma scenario development. Besides this measurement is essential to evaluate these heat fluxes for a better knowledge of the physics of plasma-wall interaction, it is also required to monitor the fatigue of PFCs. Infrared system (IR) is used to manage to measure surface temperature in real time. For carbon PFCs, the emissivity is high and known (ε ~ 0.8), therefore the contribution of the reflected flux from environment and collected by the IR cameras can be neglected. However, the future tokamaks such as WEST and ITER will be equipped with PFCs in metal (W and Be/W, respectively) with low and variable emissivities (ε ~ 0.1–0.4). Consequently, the reflected flux will contribute significantly in the collected flux by IR camera. The modulated active pyrometry, using a bicolor camera, proposed in this paper allows a 2D surface temperature measurement independently of the reflected fluxes and the emissivity. Experimental results with Tungsten sample are reported and compared with simultaneous measurement performed with classical pyrometry (monochromatic and bichromatic) with and without reflective flux demonstrating the efficiency of this method for surface temperature measurement independently of the reflected flux and the emissivity.
Nitrogen retention mechanisms in tokamaks with beryllium and tungsten plasma-facing surfaces
NASA Astrophysics Data System (ADS)
Oberkofler, M.; Meisl, G.; Hakola, A.; Drenik, A.; Alegre, D.; Brezinsek, S.; Craven, R.; Dittmar, T.; Keenan, T.; Romanelli, S. G.; Smith, R.; Douai, D.; Herrmann, A.; Krieger, K.; Kruezi, U.; Liang, G.; Linsmeier, Ch; Mozetic, M.; Rohde, V.; the ASDEX Upgrade Team; the EUROfusion MST1 Team; Contributors, JET
2016-02-01
Global gas balance experiments at ASDEX Upgrade (AUG) and JET have shown that a considerable fraction of nitrogen injected for radiative cooling is not recovered as N2 upon regeneration of the liquid helium cryo pump. The most probable loss channels are ion implantation into plasma-facing materials, co-deposition and ammonia formation. These three mechanisms are investigated in laboratory and tokamak experiments and by numerical simulations. Laboratory experiments have shown that implantation of nitrogen ions into beryllium and tungsten leads to the formation of surface nitrides, which may decompose under thermal loads. On beryllium the presence of nitrogen at the surface has been seen to reduce the sputtering yield. On tungsten surfaces it has been observed that the presence of nitrogen can increase hydrogen retention. The global nitrogen retention in AUG by implantation into the tungsten surfaces saturates. At JET the steady state nitrogen retention is increased by co-deposition with beryllium. The tokamak experiments are interpreted in detail by simulations of the global migration with WallDYN. Mass spectrometry of the exhaust gas of AUG and JET has revealed the conversion of nitrogen to ammonia at percent-levels. Conclusions are drawn on the potential implications of nitrogen seeding on the operation of a reactor in a deuterium-tritium mix.
2D surface temperature measurement of plasma facing components with modulated active pyrometry
NASA Astrophysics Data System (ADS)
Amiel, S.; Loarer, T.; Pocheau, C.; Roche, H.; Gauthier, E.; Aumeunier, M.-H.; Le Niliot, C.; Rigollet, F.; Courtois, X.; Jouve, M.; Balorin, C.; Moncada, V.
2014-10-01
In nuclear fusion devices, such as Tore Supra, the plasma facing components (PFC) are in carbon. Such components are exposed to very high heat flux and the surface temperature measurement is mandatory for the safety of the device and also for efficient plasma scenario development. Besides this measurement is essential to evaluate these heat fluxes for a better knowledge of the physics of plasma-wall interaction, it is also required to monitor the fatigue of PFCs. Infrared system (IR) is used to manage to measure surface temperature in real time. For carbon PFCs, the emissivity is high and known (ɛ ˜ 0.8), therefore the contribution of the reflected flux from environment and collected by the IR cameras can be neglected. However, the future tokamaks such as WEST and ITER will be equipped with PFCs in metal (W and Be/W, respectively) with low and variable emissivities (ɛ ˜ 0.1-0.4). Consequently, the reflected flux will contribute significantly in the collected flux by IR camera. The modulated active pyrometry, using a bicolor camera, proposed in this paper allows a 2D surface temperature measurement independently of the reflected fluxes and the emissivity. Experimental results with Tungsten sample are reported and compared with simultaneous measurement performed with classical pyrometry (monochromatic and bichromatic) with and without reflective flux demonstrating the efficiency of this method for surface temperature measurement independently of the reflected flux and the emissivity.
Flat tori in three-dimensional space and convex integration
Borrelli, Vincent; Jabrane, Saïd; Lazarus, Francis; Thibert, Boris
2012-01-01
It is well-known that the curvature tensor is an isometric invariant of C2 Riemannian manifolds. This invariant is at the origin of the rigidity observed in Riemannian geometry. In the mid 1950s, Nash amazed the world mathematical community by showing that this rigidity breaks down in regularity C1. This unexpected flexibility has many paradoxical consequences, one of them is the existence of C1 isometric embeddings of flat tori into Euclidean three-dimensional space. In the 1970s and 1980s, M. Gromov, revisiting Nash’s results introduced convex integration theory offering a general framework to solve this type of geometric problems. In this research, we convert convex integration theory into an algorithm that produces isometric maps of flat tori. We provide an implementation of a convex integration process leading to images of an embedding of a flat torus. The resulting surface reveals a C1 fractal structure: Although the tangent plane is defined everywhere, the normal vector exhibits a fractal behavior. Isometric embeddings of flat tori may thus appear as a geometric occurrence of a structure that is simultaneously C1 and fractal. Beyond these results, our implementation demonstrates that convex integration, a theory still confined to specialists, can produce computationally tractable solutions of partial differential relations. PMID:22523238
ERIC Educational Resources Information Center
Swanson, David
2011-01-01
We give elementary proofs of formulas for the area and perimeter of a planar convex body surrounded by a band of uniform thickness. The primary tool is a integral formula for the perimeter of a convex body which describes the perimeter in terms of the projections of the body onto lines in the plane.
How to name and order convex polyhedra.
Voytekhovsky, Yury L
2016-09-01
In this paper a method is suggested for naming any convex polyhedron by a numerical code arising from the adjacency matrix of its edge graph. A polyhedron is uniquely fixed by its name and can be built using it. Classes of convex n-acra (i.e. n-vertex polyhedra) are strictly ordered by their names. PMID:27580206
Shazman, Shula; Elber, Gershon; Mandel-Gutfreund, Yael
2011-01-01
Protein nucleic acid interactions play a critical role in all steps of the gene expression pathway. Nucleic acid (NA) binding proteins interact with their partners, DNA or RNA, via distinct regions on their surface that are characterized by an ensemble of chemical, physical and geometrical properties. In this study, we introduce a novel methodology based on differential geometry, commonly used in face recognition, to characterize and predict NA binding surfaces on proteins. Applying the method on experimentally solved three-dimensional structures of proteins we successfully classify double-stranded DNA (dsDNA) from single-stranded RNA (ssRNA) binding proteins, with 83% accuracy. We show that the method is insensitive to conformational changes that occur upon binding and can be applicable for de novo protein-function prediction. Remarkably, when concentrating on the zinc finger motif, we distinguish successfully between RNA and DNA binding interfaces possessing the same binding motif even within the same protein, as demonstrated for the RNA polymerase transcription-factor, TFIIIA. In conclusion, we present a novel methodology to characterize protein surfaces, which can accurately tell apart dsDNA from an ssRNA binding interfaces. The strength of our method in recognizing fine-tuned differences on NA binding interfaces make it applicable for many other molecular recognition problems, with potential implications for drug design. PMID:21693557
Artificial Neural Networks for Surface Roughness Prediction when Face Milling Al 7075-T7351
NASA Astrophysics Data System (ADS)
Muñoz-Escalona, Patricia; Maropoulos, Paul G.
2010-03-01
In this work, different artificial neural networks (ANN) are developed for the prediction of surface roughness ( R a ) values in Al alloy 7075-T7351 after face milling machining process. The radial base (RBNN), feed forward (FFNN), and generalized regression (GRNN) networks were selected, and the data used for training these networks were derived from experiments conducted using a high-speed milling machine. The Taguchi design of experiment was applied to reduce the time and cost of the experiments. From this study, the performance of each ANN used in this research was measured with the mean square error percentage and it was observed that FFNN achieved the best results. Also the Pearson correlation coefficient was calculated to analyze the correlation between the five inputs (cutting speed, feed per tooth, axial depth of cut, chip’s width, and chip’s thickness) selected for the network with the selected output (surface roughness). Results showed a strong correlation between the chip thickness and the surface roughness followed by the cutting speed.
Shazman, Shula; Elber, Gershon; Mandel-Gutfreund, Yael
2011-09-01
Protein nucleic acid interactions play a critical role in all steps of the gene expression pathway. Nucleic acid (NA) binding proteins interact with their partners, DNA or RNA, via distinct regions on their surface that are characterized by an ensemble of chemical, physical and geometrical properties. In this study, we introduce a novel methodology based on differential geometry, commonly used in face recognition, to characterize and predict NA binding surfaces on proteins. Applying the method on experimentally solved three-dimensional structures of proteins we successfully classify double-stranded DNA (dsDNA) from single-stranded RNA (ssRNA) binding proteins, with 83% accuracy. We show that the method is insensitive to conformational changes that occur upon binding and can be applicable for de novo protein-function prediction. Remarkably, when concentrating on the zinc finger motif, we distinguish successfully between RNA and DNA binding interfaces possessing the same binding motif even within the same protein, as demonstrated for the RNA polymerase transcription-factor, TFIIIA. In conclusion, we present a novel methodology to characterize protein surfaces, which can accurately tell apart dsDNA from an ssRNA binding interfaces. The strength of our method in recognizing fine-tuned differences on NA binding interfaces make it applicable for many other molecular recognition problems, with potential implications for drug design. PMID:21693557
Critical heat flux (CHF) phenomenon on a downward facing curved surface
Cheung, F.B.; Haddad, K.H.; Liu, Y.C.
1997-06-01
This report describes a theoretical and experimental study of the boundary layer boiling and critical heat flux phenomena on a downward facing curved heating surface, including both hemispherical and toroidal surfaces. A subscale boundary layer boiling (SBLB) test facility was developed to measure the spatial variation of the critical heat flux and observe the underlying mechanisms. Transient quenching and steady-state boiling experiments were performed in the SBLB facility under both saturated and subcooled conditions to obtain a complete database on the critical heat flux. To complement the experimental effort, an advanced hydrodynamic CHF model was developed from the conservation laws along with sound physical arguments. The model provides a clear physical explanation for the spatial variation of the CHF observed in the SBLB experiments and for the weak dependence of the CHF data on the physical size of the vessel. Based upon the CHF model, a scaling law was established for estimating the local critical heat flux on the outer surface of a heated hemispherical vessel that is fully submerged in water. The scaling law, which compares favorably with all the available local CHF data obtained for various vessel sizes, can be used to predict the local CHF limits on large commercial-size vessels. This technical information represents one of the essential elements that is needed in assessing the efficacy of external cooling of core melt by cavity flooding as a severe accident management strategy. 83 figs., 3 tabs.
The impact of surface morphology on C- and Si-face 4H-SiC Schottky barrier diodes
NASA Astrophysics Data System (ADS)
Lee, Kung-Yen; Huang, Chih-Fang; Chen, Wenzhou; Capano, Michael A.
2007-12-01
The goal of this research is to investigate the correlation of reverse characteristics of Schottky barrier diodes (SBDs) and surface morphological defects on 4° (off-axis) carbon (C) face, 4° and 8° silicon (Si) face 4H-SiC. Different dimensions of SBDs with boron-implanted edge terminations are fabricated on 4° C-face, 4° and 8° Si-face 4H-SiC samples. The ideality factor for these three samples is about 1.1. Average breakdown voltages of 4° Si-face 4H-SiC SBDs are higher than the other two samples, particularly for large size SBDs. Breakdown voltages of 1500 and 2000 μm 4° Si-face SBDs can reach over 1000 V. This value is about two times higher than the other two samples, though the root-mean-square (RMS) roughness of 4° Si-face samples obtained from atomic force microscopy (AFM) is 3.5 nm. The yield of 1500 and 2000 μm 4° Si-face 4H-SiC SBDs with a breakdown voltage over 1000 V is more than 50%, much higher than the other two samples.
Neck and face surface electromyography for prosthetic voice control after total laryngectomy.
Stepp, Cara E; Heaton, James T; Rolland, Rebecca G; Hillman, Robert E
2009-04-01
The electrolarynx (EL) is a common rehabilitative speech aid for individuals who have undergone total laryngectomy, but they typically lack pitch control and require the exclusive use of one hand. The viability of using neck and face surface electromyography (sEMG) to control the onset, offset, and pitch of an EMG-controlled EL (EMG-EL) was studied. Eight individuals who had undergone total laryngectomy produced serial and running speech using a typical handheld EL and the EMG-EL while attending to real-time visual sEMG biofeedback. Running speech tokens produced with the EMG-EL were examined for naturalness by 10 listeners relative to those produced with a typical EL using a visual analog scale. Serial speech performance was assessed as the percentage of words that were fully voiced and pauses that were successfully produced. Results of the visual analog scale assessment indicated that individuals were able to use the EMG-EL without training to produce running speech perceived as natural as that produced with a typical handheld EL. All participants were able to produce running and serial speech with the EMG-EL controlled by sEMG from multiple recording locations, with the superior ventral neck or submental surface locations providing at least one of the two best control locations. PMID:19304494
Stepp, Cara E; Heaton, James T; Givens, Rebecca N; Hillman, Robert E
2012-01-01
The electrolarynx (EL) is a common rehabilitative speech aid for individuals who have undergone total laryngectomy, but typically lack pitch control and require the exclusive use of one hand. The viability of using neck and face surface electromyography (sEMG) to control the onset, offset, and pitch of an EMG-controlled EL (EMG-EL) was studied. Eight individuals who had undergone total laryngectomy produced serial and running speech using a typical handheld EL and the EMG-EL while attending to real-time visual sEMG biofeedback. Running speech tokens produced with the EMG-EL were examined for naturalness by 10 listeners relative to those produced with a typical EL using a visual analog scale. Serial speech performance was assessed as the percentage of words that were fully voiced and pauses that were successfully produced. Results of the visual analog scale assessment indicated that individuals were able to use the EMG-EL without training to produce running speech perceived as natural as that produced with a typical handheld EL. All participants were able to produce running and serial speech with the EMG-EL controlled by sEMG from multiple recording locations, with the superior ventral neck or submental surface locations providing at least one of the two best control locations. PMID:19304494
Surface Potentials of (001), (012), (113) Hematite (α-Fe2O3) Crystal Faces in Aqueous Solution
Chatman, Shawn ME; Zarzycki, Piotr P.; Rosso, Kevin M.
2013-09-05
Hematite (α-Fe2O3) is an important candidate electrode for energy system technologies such as photoelectrochemical water splitting. Conversion efficiency issues with this material are presently being addressed through nanostructuring, doping, and surface modification. However, key electrochemical properties of hematite/electrolyte interfaces remain poorly understood at a fundamental level, in particular those of crystallographically well-defined hematite faces likely present as interfacial components at the grain scale. We report a combined measurement and theory study that isolates and evaluates the equilibrium surface potentials of three nearly defect-free single crystal faces of hematite, titrated from pH 3 to 11.25. We link measured surface potentials with atomic-scale surface topology, namely the ratio and distributions of surface protonation/deprotonation site types expected from the bulk structure. The data reveal face-specific points of zero potential (PZP) relatable to points of zero net charge (PZC) that lie within a small pH window (8.35-8.85). Over the entire pH range the surface potentials show strong non-Nernstian charging at pH extremes separated by a wide central plateau in agreement with surface complexation modeling predictions, but with important face-specific distinctions. We introduce a new surface complexation model based on fitting the entire data set that depends primarily only on the proton affinities of two site types and the two associated electrical double layer capacitances. The data and model show that magnitudes of surface potential biases at the pH extremes are on the order of 100 mV, similar to the activation energy for electron hopping mobility. An energy band diagram for hematite crystallites with specific face expression and pH effects is proposed that could provide a baseline for understanding water splitting performance enhancement effects from nanostructuring, and guide morphology targets and pH for systematic improvements in
Effect of Surface Site Interactions on Potentiometric Titration of Hematite (α-Fe2O3) Crystal Faces
Chatman, Shawn ME; Zarzycki, Piotr P.; Preocanin, Tajana; Rosso, Kevin M.
2013-02-01
Time dependent potentiometric pH titrations were used to study the effect of atomic scale surface structure on the protonation behavior of the structurally well defined hematite/aqueous electrolyte interfaces. Our recently proposed thermodynamic model [1,23] was applied to measured acidimetric and alkalimetric titration hysteresis loops, collected from highly organized (001), (012), and (113) crystal face terminations using pH equilibration times ranging from 15 to 30 mins. Hysteresis loop areas indicate that (001) faces equilibrate faster than the (012) and (113) faces, consistent with the different expected ensembles of singly, doubly, and triply coordinated surface sites on each face. Strongly non-linear hysteretic pH-potential relationships were found, with slopes exceeding Nernstian, collectively indicating that protonation and deprotonation is much more complex than embodied in present day surface complexation models. The asymmetrical shape of the acidimetric and alkalimetric titration branches were used to illustrate a proposed steric "leaky screen" repulsion/trapping interaction mechanism that stems from high affinity singly-coordinated sites electrostatically and sterically screening lower affinity doubly and triply coordinated sites. Our data indicate that site interaction is the dominant phenomenon defining surface potential accumulation behavior on single crystal faces of metal oxide minerals.
Lower Bound for Energies of Harmonic Tangent Unit-Vector Fields on Convex Polyhedra
NASA Astrophysics Data System (ADS)
Majumdar, A.; Robbins, J. M.; Zyskin, M.
2004-11-01
We derive a lower bound for energies of harmonic maps of convex polyhedra in $ \\R^3 $ to the unit sphere $S^2,$ with tangent boundary conditions on the faces. We also establish that $C^\\infty$ maps, satisfying tangent boundary conditions, are dense with respect to the Sobolev norm, in the space of continuous tangent maps of finite energy.
Geometric-Harmonic convexity and integral inequalities
NASA Astrophysics Data System (ADS)
Akdemir, Ahmet Ocak; Yalçin, Abdüllatif; Polat, Fatma; Kavurmaci-Önalan, Havva
2016-04-01
In this paper, some new integral inequalities have been proved for functions whose absolute value of derivatives are GH-convex functions by using integral equalities that have been obtained previously.
Ohkubo, Hidetoshi; Nishio, Shigefumi )
1993-04-01
The effects of cooling rate and thermal conductivity of a heat-transfer plate on mist-cooling heat transfer were investigated experimentally for the high-temperature region. Experiments were conducted for horizontal upward-facing surfaces made of silver, stainless steel, and fused quartz. The experimental conditions of mist flow were as follows: The air velocity V[sub a] = 20 m/s, the temperature of water droplet T[sub l] = 21 C, and the volumetric droplet-flow-rate D = 0.00043-0.00472[sup 3]/(m[sup 2]s). It was found that, in the case where the horizontal surfaces face upward, the thermal properties of surface material does not significantly affect the heat-transfer coefficient, but the cooling rate of the surface affects it if the heat capacity of the surface is less than a critical value.
Univalent harmonic mappings convex in one direction
NASA Astrophysics Data System (ADS)
Ponnusamy, S.; Kaliraj, A. Sairam
2014-09-01
In this paper, we present a criterion for a harmonic function to be convex in one direction. Also, we discuss the class of harmonic functions starlike in one direction in the unit disk and obtain a method to construct univalent harmonic functions convex in one direction. Although the converse of classical Alexander's theorem for harmonic functions was proved to be false, we obtain a version of converse of it under a suitable additional condition.
Slyfield, C R; Niemeyer, K E; Tkachenko, E V; Tomlinson, R E; Steyer, G G; Patthanacharoenphon, C G; Kazakia, G J; Wilson, D L; Hernandez, C J
2009-10-01
Serial block face imaging is a microscopy technique in which the top of a specimen is cut or ground away and a mosaic of images is collected of the newly revealed cross-section. Images collected from each slice are then digitally stacked to achieve 3D images. The development of fully automated image acquisition devices has made serial block face imaging more attractive by greatly reducing labour requirements. The technique is particularly attractive for studies of biological activity within cancellous bone as it has the capability of achieving direct, automated measures of biological and morphological traits and their associations with one another. When used with fluorescence microscopy, serial block face imaging has the potential to achieve 3D images of tissue as well as fluorescent markers of biological activity. Epifluorescence-based serial block face imaging presents a number of unique challenges for visualizing bone specimens due to noise generated by sub-surface signal and local variations in tissue autofluorescence. Here we present techniques for processing serial block face images of trabecular bone using a combination of non-uniform illumination correction, precise tiling of the mosaic in each cross-section, cross-section alignment for vertical stacking, removal of sub-surface signal and segmentation. The resulting techniques allow examination of bone surface texture that will enable 3D quantitative measures of biological processes in cancellous bone biopsies. PMID:19772536
Surface acoustic load sensing using a face-shear PIN-PMN-PT single-crystal resonator.
Kim, Kyungrim; Zhang, Shujun; Jiang, Xiaoning
2012-11-01
Pb(In(0.5)Nb(0.5))O(3)-Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PIN-PMN-PT) resonators for surface acoustic load sensing are presented in this paper. Different acoustic loads are applied to thickness mode, thickness-shear mode, and face-shear mode resonators, and the electrical impedances at resonance and anti-resonance frequencies are recorded. More than one order of magnitude higher sensitivity (ratio of electrical impedance change to surface acoustic impedance change) at the resonance is achieved for the face-shear-mode resonator compared with other resonators with the same dimensions. The Krimholtz, Leedom, and Matthaei (KLM) model is used to verify the surface acoustic loading effect on the electrical impedance spectrum of face-shear PIN-PMN-PT single-crystal resonators. The demonstrated high sensitivity of face-shear mode resonators to surface loads is promising for a broad range of applications, including artificial skin, biological and chemical sensors, touch screens, and other touch-based sensors. PMID:23192819
What causes the facing-the-viewer bias in biological motion?
Weech, Séamas; McAdam, Matthew; Kenny, Sophie; Troje, Nikolaus F
2014-01-01
Orthographically projected biological motion point-light displays are generally ambiguous with respect to their orientation in depth, yet observers consistently prefer the facing-the-viewer interpretation. There has been discussion as to whether this bias can be attributed to the social relevance of biological motion stimuli or relates to local, low-level stimulus properties. In the present study we address this question. In Experiment 1, we compared the facing-the-viewer bias produced by a series of four stick figures and three human silhouettes that differed in posture, gender, and the presence versus absence of walking motion. Using a paradigm in which we asked observers to indicate the spinning direction of these figures, we found no bias when participants observed silhouettes, whereas a pronounced degree of bias was elicited by most stick figures. We hypothesized that the ambiguous surface normals on the lines and dots that comprise stick figures are prone to a visual bias that assumes surfaces to be convex. The local surface orientations of the occluding contours of silhouettes are unambiguous, and as such the convexity bias does not apply. In Experiment 2, we tested the role of local features in ambiguous surface perception by adding dots to the elbows and knees of silhouettes. We found biases consistent with the facing directions implied by a convex body surface. The results unify a number of findings regarding the facing-the-viewer bias. We conclude that the facing-the-viewer bias is established at the level of surface reconstruction from local image features rather than on a semantic level. PMID:25761278
Convex-relaxed kernel mapping for image segmentation.
Ben Salah, Mohamed; Ben Ayed, Ismail; Jing Yuan; Hong Zhang
2014-03-01
This paper investigates a convex-relaxed kernel mapping formulation of image segmentation. We optimize, under some partition constraints, a functional containing two characteristic terms: 1) a data term, which maps the observation space to a higher (possibly infinite) dimensional feature space via a kernel function, thereby evaluating nonlinear distances between the observations and segments parameters and 2) a total-variation term, which favors smooth segment surfaces (or boundaries). The algorithm iterates two steps: 1) a convex-relaxation optimization with respect to the segments by solving an equivalent constrained problem via the augmented Lagrange multiplier method and 2) a convergent fixed-point optimization with respect to the segments parameters. The proposed algorithm can bear with a variety of image types without the need for complex and application-specific statistical modeling, while having the computational benefits of convex relaxation. Our solution is amenable to parallelized implementations on graphics processing units (GPUs) and extends easily to high dimensions. We evaluated the proposed algorithm with several sets of comprehensive experiments and comparisons, including: 1) computational evaluations over 3D medical-imaging examples and high-resolution large-size color photographs, which demonstrate that a parallelized implementation of the proposed method run on a GPU can bring a significant speed-up and 2) accuracy evaluations against five state-of-the-art methods over the Berkeley color-image database and a multimodel synthetic data set, which demonstrates competitive performances of the algorithm. PMID:24723519
Ogren, E.
1993-01-01
Photosynthesis in the intermediate light range is most efficient when the convexity of the photosynthetic light-response curve is high. Factors determining the convexity were examined for intact leaves using Salix sp. and for a plant cell culture using the green microalga Coccomyxa sp. It was found that the leaf had lower convexity than diluted plant cells because the light gradient through the leaf was not fully matched by a corresponding gradient in photosynthetic capacity. The degree to which the leaf gradients were matched was quantified by measuring photosynthesis at both leaf surfaces using modulated fluorescence. Two principal growth conditions were identified as those causing mismatch of leaf gradients and lowering of the convexity relative to cells. The first was growth under low light, where leaves did not develop any noteworthy gradient in photosynthetic capacity. This led to decreased convexity, particularly in old leaves with high chlorophyll content and, hence, steep light gradients. Second and less conspicuous was growth under high light conditions when light was given bilaterally rather than unilaterally, which yielded leaves of high photosynthetic capacity at both surfaces. Two situations were also identified that caused the convexity to decrease at the chloroplast level: (a) increased light during growth, for both leaves and cells, and (b) increased CO2 concentration during measurement of high-light-grown leaves. These changes of the intrinsic convexity were interpreted to indicate that the convexity declines with increased capacity of ribulose-1,5-bisphosphate carboxylase/oxygenase relative to the capacity of electron transport. PMID:12231754
Effects of an aft facing step on the surface of a laminar flow glider wing
NASA Technical Reports Server (NTRS)
Sandlin, Doral R.; Saiki, Neal
1993-01-01
A motor glider was used to perform a flight test study on the effects of aft facing steps in a laminar boundary layer. This study focuses on two dimensional aft facing steps oriented spanwise to the flow. The size and location of the aft facing steps were varied in order to determine the critical size that will force premature transition. Transition over a step was found to be primarily a function of Reynolds number based on step height. Both of the step height Reynolds numbers for premature and full transition were determined. A hot film anemometry system was used to detect transition.
Kudrawiec, R.; Janicki, L.; Gladysiewicz, M.; Misiewicz, J.; Cywinski, G.; Boćkowski, M.; Muzioł, G.
2013-07-29
Two series of N- and Ga-face GaN Van Hoof structures were grown by plasma-assisted molecular beam epitaxy to study the surface potential barrier by contactless electroreflectance (CER). A clear CER resonance followed by strong Franz-Keldysh oscillation of period varying with the thickness of undoped GaN layer was observed for these structures. This period was much shorter for N-polar structures that means smaller surface potential barrier in these structures than in Ga-polar structures. From the analysis of built-in electric field it was determined that the Fermi-level is located 0.27 ± 0.05 and 0.60 ± 0.05 eV below the conduction band for N- and Ga-face GaN surface, respectively.
Automatic Treatment Planning with Convex Imputing
NASA Astrophysics Data System (ADS)
Sayre, G. A.; Ruan, D.
2014-03-01
Current inverse optimization-based treatment planning for radiotherapy requires a set of complex DVH objectives to be simultaneously minimized. This process, known as multi-objective optimization, is challenging due to non-convexity in individual objectives and insufficient knowledge in the tradeoffs among the objective set. As such, clinical practice involves numerous iterations of human intervention that is costly and often inconsistent. In this work, we propose to address treatment planning with convex imputing, a new-data mining technique that explores the existence of a latent convex objective whose optimizer reflects the DVH and dose-shaping properties of previously optimized cases. Using ten clinical prostate cases as the basis for comparison, we imputed a simple least-squares problem from the optimized solutions of the prostate cases, and show that the imputed plans are more consistent than their clinical counterparts in achieving planning goals.
NASA Technical Reports Server (NTRS)
Palac, Donald T.
2011-01-01
The Fission Surface Power Systems Project became part of the ETDP on October 1, 2008. Its goal was to demonstrate fission power system technology readiness in an operationally relevant environment, while providing data on fission system characteristics pertinent to the use of a fission power system on planetary surfaces. During fiscal years 08 to 10, the FSPS project activities were dominated by hardware demonstrations of component technologies, to verify their readiness for inclusion in the fission surface power system. These Pathfinders demonstrated multi-kWe Stirling power conversion operating with heat delivered via liquid metal NaK, composite Ti/H2O heat pipe radiator panel operations at 400 K input water temperature, no-moving-part electromagnetic liquid metal pump operation with NaK at flight-like temperatures, and subscale performance of an electric resistance reactor simulator capable of reproducing characteristics of a nuclear reactor for the purpose of system-level testing, and a longer list of component technologies included in the attached report. Based on the successful conclusion of Pathfinder testing, work began in 2010 on design and development of the Technology Demonstration Unit (TDU), a full-scale 1/4 power system-level non-nuclear assembly of a reactor simulator, power conversion, heat rejection, instrumentation and controls, and power management and distribution. The TDU will be developed and fabricated during fiscal years 11 and 12, culminating in initial testing with water cooling replacing the heat rejection system in 2012, and complete testing of the full TDU by the end of 2014. Due to its importance for Mars exploration, potential applicability to missions preceding Mars missions, and readiness for an early system-level demonstration, the Enabling Technology Development and Demonstration program is currently planning to continue the project as the Fission Power Systems project, including emphasis on the TDU completion and testing.
Convex Regression with Interpretable Sharp Partitions
Petersen, Ashley; Simon, Noah; Witten, Daniela
2016-01-01
We consider the problem of predicting an outcome variable on the basis of a small number of covariates, using an interpretable yet non-additive model. We propose convex regression with interpretable sharp partitions (CRISP) for this task. CRISP partitions the covariate space into blocks in a data-adaptive way, and fits a mean model within each block. Unlike other partitioning methods, CRISP is fit using a non-greedy approach by solving a convex optimization problem, resulting in low-variance fits. We explore the properties of CRISP, and evaluate its performance in a simulation study and on a housing price data set.
SEM study on the dorsal lingual surface of the lesser dog-faced fruit bat, Cynopterus brachyotis.
Emura, S; Hayakawa, D; Chen, H; Shoumura, S; Atoji, Y; Agungpriyono, S
2001-10-01
The dorsal lingual surface of the lesser dog-faced fruit bat was examined by scanning electron microscopy (SEM). Filiform (Fi), fungiform (Fu) and vallate papillae (V) were observed. The Fi papillae were distributed over the entire dorsal surface of the tongue. The Fi papillae notably differed in morphology by their location on the tongue and could be classified into 5 types: 1) crown-like papillae, 2) giant trifid papillae, 3) scale-like papillae, 4) small conical papillae, and 5) large conical papillae. The Fu papillae were present rounded bodies on the anterior 2/3 of the tongue. The lesser dog-faced fruit bat showed the triangular arrangement of the three V, with the apex of the triangle directed posteriorly. PMID:11774747
NASA Astrophysics Data System (ADS)
Simunovic, K.; Simunovic, G.; Saric, T.
2013-10-01
The surface roughness is a very significant indicator of surface quality. It represents an essential exploitation requirement and influences technological time and costs, i.e. productivity. For that reason, the main objective of this paper is to analyse the influence of face milling cutting parameters (number of revolution, feed rate and depth of cut) on the surface roughness of aluminium alloy. Hence, a statistical (regression) model has been developed to predict the surface roughness by using the methodology of experimental design. Central composite design is chosen for fitting response surface. Also, numerical optimization considering two goals simultaneously (minimum propagation of error and minimum roughness) was performed throughout the experimental region. In this way, the settings of cutting parameters causing the minimum variability in response were determined for the estimated variations of the significant regression factors.
NASA Astrophysics Data System (ADS)
Lucia, M.; Kaita, R.; Majeski, R.; Bedoya, F.; Allain, J. P.; Abrams, T.; Bell, R. E.; Boyle, D. P.; Jaworski, M. A.; Schmitt, J. C.
2015-08-01
The Materials Analysis and Particle Probe (MAPP) diagnostic has been implemented on the Lithium Tokamak Experiment (LTX) at PPPL, providing the first in situ X-ray photoelectron spectroscopy (XPS) surface characterization of tokamak plasma facing components (PFCs). MAPP samples were exposed to argon glow discharge conditioning (GDC), lithium evaporations, and hydrogen tokamak discharges inside LTX. Samples were analyzed with XPS, and alterations to surface conditions were correlated against observed LTX plasma performance changes. Argon GDC caused the accumulation of nm-scale metal oxide layers on the PFC surface, which appeared to bury surface carbon and oxygen contamination and thus improve plasma performance. Lithium evaporation led to the rapid formation of a lithium oxide (Li2O) surface; plasma performance was strongly improved for sufficiently thick evaporative coatings. Results indicate that a 5 h argon GDC or a 50 nm evaporative lithium coating will both significantly improve LTX plasma performance.
Robust Utility Maximization Under Convex Portfolio Constraints
Matoussi, Anis; Mezghani, Hanen Mnif, Mohamed
2015-04-15
We study a robust maximization problem from terminal wealth and consumption under a convex constraints on the portfolio. We state the existence and the uniqueness of the consumption–investment strategy by studying the associated quadratic backward stochastic differential equation. We characterize the optimal control by using the duality method and deriving a dynamic maximum principle.
Convex Formulations of Learning from Crowds
NASA Astrophysics Data System (ADS)
Kajino, Hiroshi; Kashima, Hisashi
It has attracted considerable attention to use crowdsourcing services to collect a large amount of labeled data for machine learning, since crowdsourcing services allow one to ask the general public to label data at very low cost through the Internet. The use of crowdsourcing has introduced a new challenge in machine learning, that is, coping with low quality of crowd-generated data. There have been many recent attempts to address the quality problem of multiple labelers, however, there are two serious drawbacks in the existing approaches, that are, (i) non-convexity and (ii) task homogeneity. Most of the existing methods consider true labels as latent variables, which results in non-convex optimization problems. Also, the existing models assume only single homogeneous tasks, while in realistic situations, clients can offer multiple tasks to crowds and crowd workers can work on different tasks in parallel. In this paper, we propose a convex optimization formulation of learning from crowds by introducing personal models of individual crowds without estimating true labels. We further extend the proposed model to multi-task learning based on the resemblance between the proposed formulation and that for an existing multi-task learning model. We also devise efficient iterative methods for solving the convex optimization problems by exploiting conditional independence structures in multiple classifiers.
Local Convexity-Preserving C2 Rational Cubic Spline for Convex Data
Abd Majid, Ahmad; Ali, Jamaludin Md.
2014-01-01
We present the smooth and visually pleasant display of 2D data when it is convex, which is contribution towards the improvements over existing methods. This improvement can be used to get the more accurate results. An attempt has been made in order to develop the local convexity-preserving interpolant for convex data using C2 rational cubic spline. It involves three families of shape parameters in its representation. Data dependent sufficient constraints are imposed on single shape parameter to conserve the inherited shape feature of data. Remaining two of these shape parameters are used for the modification of convex curve to get a visually pleasing curve according to industrial demand. The scheme is tested through several numerical examples, showing that the scheme is local, computationally economical, and visually pleasing. PMID:24757421
On strongly GA-convex functions and stochastic processes
Bekar, Nurgül Okur; Akdemir, Hande Günay; İşcan, İmdat
2014-08-20
In this study, we introduce strongly GA-convex functions and stochastic processes. We provide related well-known Kuhn type results and Hermite-Hadamard type inequality for strongly GA-convex functions and stochastic processes.
On strongly GA-convex functions and stochastic processes
NASA Astrophysics Data System (ADS)
Bekar, Nurgül Okur; Akdemir, Hande Günay; Işcan, Imdat
2014-08-01
In this study, we introduce strongly GA-convex functions and stochastic processes. We provide related well-known Kuhn type results and Hermite-Hadamard type inequality for strongly GA-convex functions and stochastic processes.
Gourdin, W H; Dzenitis, E; Martin, D; Listiyo, K; Sherman, G; Kent, W; Butlin, R; Stolz, C J; Pryatel, J
2004-11-10
We describe a system to inspect and remove surface debris in-situ from the surfaces of upward-facing mirrors that transport 1053 nm laser light to the target chamber of the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory. Grazing angle (2-5{sup o}) illumination with a bar light highlights debris {approx}10 {micro}m in size and larger, which is then viewed through windows in the enclosures of selected mirrors. Debris is removed with 1-second bursts of high velocity (76 m/s) clean air delivered across the optic surfaces by a commercially available linear nozzle (''gas knife''). Experiments with aluminum, stainless steel, glass and polystyrene particles of various sizes >30 {micro}m show that particle removal efficiency is near 100% over most of the mirror surfaces for all sizes tested.
Face-dependent Auger neutralization and ground-state energy shift for He in front of Al surfaces
Wethekam, S.; Winter, H.; Valdes, Diego; Monreal, R. C.
2008-08-15
He atoms and ions with keV energies are scattered under grazing angles of incidence from Al(111), Al(100), and Al(110) surfaces. Fractions of surviving ions and normal energy gains of He{sup +} ions prior to neutralization, derived from shifts of angular distributions for incident atoms and ions, are compared to results from three-dimensional Monte Carlo simulations based on theoretically calculated Auger neutralization rates and He ground-state energy shifts. From the good agreement of experimental data with simulations, we conclude a detailed microscopic understanding for a model system of ion-surface interactions. Our work provides further evidence for the recently reported surface Miller index dependence for the neutralization of He{sup +} ions at metal surfaces. The study is extended to the face dependence of the He ground-state energy shift.
Duquenne, Philippe; Simon, Xavier; Demange, Valérie; Harper, Martin; Wild, Pascal
2015-05-01
A set of 270 bioaerosol samples was taken from 15 composting facilities using polystyrene closed-face filter cassettes (CFCs). The objective was to measure the quantity of endotoxin deposits on the inner surfaces of the cassettes (sometimes referred to as 'wall deposits'). The results show that endotoxins are deposited on the inner surfaces of the CFCs through sampling and/or handling of samples. The quantity of endotoxins measured on inner surfaces range between 0.05 (the limit of detection of the method) and 3100 endotoxin units per cassette. The deposits can represent a large and variable percentage of the endotoxins sampled. More than a third of the samples presented a percentage of inner surface deposits >40% of the total quantity of endotoxins collected (filter + inner surfaces). Omitting these inner surface deposits in the analytical process lead to measurement errors relative to sampling all particles entering the CFC sampler, corresponding to a developing consensus on matching the inhalable particulate sampling convention. The result would be underestimated exposures and could affect the decision as to whether or not a result is acceptable in comparison to airborne concentration limits defined in terms of the inhalability convention. The results of this study suggest including the endotoxins deposited on the inner surfaces of CFCs during analysis. Further researches are necessary to investigate endotoxin deposits on the inner cassette surfaces in other working sectors. PMID:25535181
Weinberg, SM; Naidoo, SD; Bardi, KM; Brandon, CA; Neiswanger, K; Resick, JM; Martin, RA; Marazita, ML
2009-01-01
Objective Various lines of evidence suggest that face shape may be a predisposing factor for nonsyndromic cleft lip with or without cleft palate (CL/P). In the present study, 3D surface imaging and statistical shape analysis were used to evaluate face shape differences between the unaffected (non-cleft) parents of individuals with CL/P and unrelated controls. Methods Sixteen facial landmarks were collected from 3D captures of 80 unaffected parents and 80 matched controls. Prior to analysis, each unaffected parent was assigned to a subgroup on the basis of prior family history (positive or negative). A geometric morphometric approach was utilized to scale and superimpose the landmark coordinate data (Procrustes analysis), test for omnibus group differences in face shape, and uncover specific modes of shape variation capable of discriminating unaffected parents from controls. Results Significant disparity in face shape was observed between unaffected parents and controls (p < 0.01). Notably, these changes were specific to parents with a positive family history of CL/P. Shape changes associated with CL/P predisposition included marked flattening of the facial profile (midface retrusion), reduced upper facial height, increased lower facial height and excess interorbital width. Additionally, a sex-specific pattern of parent-control difference was evident in the transverse dimensions of the nasolabial complex. Conclusions The faces of unaffected parents from multiplex cleft families display meaningful shape differences compared with the general population. Quantitative assessment of the facial phenotype in cleft families may enhance efforts to discover the root causes of CL/P. PMID:19840279
The many faces of Mars. [Mariner 9 photography of Mars surface, satellites, and atmosphere
NASA Technical Reports Server (NTRS)
1973-01-01
The Mariner Mars 1971 spacecraft was the first to orbit another planet. For 349 days, it transmitted a vast amount of data, including 7300 television pictures, gathered by its five scientific instruments. This memorandum presents some of the findings on the characteristics of the surface, atmosphere, and satellites of Mars. Included are photographs of the surface, atmosphere, satellites, surface maps, and spectrometric data for the atmosphere.
NASA Technical Reports Server (NTRS)
Weinberg, I.; Hsu, L. C.
1977-01-01
Increased solar cell efficiencies are attained by reduction of surface recombination and variation of impurity concentration profiles at the n(+) surface of silicon solar cells. Diagnostic techniques are employed to evaluate the effects of specific materials preparation methodologies on surface and near surface concentrations. It is demonstrated that the MOS C-V method, when combined with a bulk measurement technique, yields more complete concentration data than are obtainable by either method alone. Specifically, new solar cell MOS C-V measurements are combined with bulk concentrations obtained by a successive layer removal technique utilizing measurements of sheet resistivity and Hall coefficient.
Face-related segregation reversal at Pt 50Ni 50 surfaces studied with the embedded atom method
NASA Astrophysics Data System (ADS)
Deurinck, P.; Creemers, C.
1999-11-01
The segregation to the three low-index surfaces of a Pt50Ni50 single crystal is modelled by Monte Carlo simulations combined with the embedded atom method (EAM). Using the best fit EAM parameters from the literature for the six transition metals of the Ni and Cu groups does not yield satisfactory results. In this work the EAM parameters are recalculated and optimised exclusively for the Pt-Ni alloy system under study. Only then does EAM reliably reproduce the driving forces for segregation. The experimental results [Y. Gauthier et al., Phys. Rev. B 31 (1985) 6216; Y. Gauthier et al., Phys. Rev. B 35 (1987) 7867; S.M. Foiles, in: P.A. Dobson, A. Miller (Eds.), Surface Segregation Phenomena, CRC Press, Boca Raton, FL, 1990, p. 79] reveal a face-related segregation reversal for the Pt50Ni50 single crystal. It appears from the simulations that this is caused by a relatively small difference in surface energy in close competition with the elastic strain release. At the open (110) surface the difference in surface energy dominates causing Ni segregation. At the (100) and (111) surfaces the difference in surface energy is overpowered by the elastic strain leading to Pt segregation. The simulations are in good agreement with the experimental results and reproduce quantitatively the Ni segregation to the (110) surface and the Pt segregation to the (100) and (111) surfaces. Only at the (110) surface significant relaxations are predicted in good agreement with experimental evidence. Atomic vibrations can be included by allowing a large number of very small displacements or with a more classical treatment of vibrational entropy. Both approaches yield the same results and show that the inclusion of atomic vibrations is important only for the (110) surface and tend to attenuate the Ni segregation profile.
Use of convexity in pouching: a comprehensive review.
Hoeflok, Jo; Kittscha, Julia; Purnell, Paris
2013-01-01
A comprehensive literature review was conducted to examine research, current best evidence, and best practice recommendations associated with the use of convex skin barriers for patients living with an ostomy. The review revealed a fragmented array of citations related to convexity and a paucity of evidence regarding convexity product descriptions and application. Most convexity choices appear to be based on the clinician experience over time using trial and error to determine clinical application. Current descriptors used for convexity products are creating confusion, and a standardized approach to product nomenclature does not exist. The development of assistive clinical practice guidelines, in conjunction with further research, is recommended. PMID:24448619
Convex nonnegative matrix factorization with manifold regularization.
Hu, Wenjun; Choi, Kup-Sze; Wang, Peiliang; Jiang, Yunliang; Wang, Shitong
2015-03-01
Nonnegative Matrix Factorization (NMF) has been extensively applied in many areas, including computer vision, pattern recognition, text mining, and signal processing. However, nonnegative entries are usually required for the data matrix in NMF, which limits its application. Besides, while the basis and encoding vectors obtained by NMF can represent the original data in low dimension, the representations do not always reflect the intrinsic geometric structure embedded in the data. Motivated by manifold learning and Convex NMF (CNMF), we propose a novel matrix factorization method called Graph Regularized and Convex Nonnegative Matrix Factorization (GCNMF) by introducing a graph regularized term into CNMF. The proposed matrix factorization technique not only inherits the intrinsic low-dimensional manifold structure, but also allows the processing of mixed-sign data matrix. Clustering experiments on nonnegative and mixed-sign real-world data sets are conducted to demonstrate the effectiveness of the proposed method. PMID:25523040
Solving ptychography with a convex relaxation
Chen, Richard Y; Ou, Xiaoze; Ames, Brendan; Tropp, Joel A; Yang, Changhuei
2015-01-01
Ptychography is a powerful computational imaging technique that transforms a collection of low-resolution images into a high-resolution sample reconstruction. Unfortunately, algorithms that currently solve this reconstruction problem lack stability, robustness, and theoretical guarantees. Recently, convex optimization algorithms have improved the accuracy and reliability of several related reconstruction efforts. This paper proposes a convex formulation of the ptychography problem. This formulation has no local minima, it can be solved using a wide range of algorithms, it can incorporate appropriate noise models, and it can include multiple a priori constraints. The paper considers a specific algorithm, based on low-rank factorization, whose runtime and memory usage are near-linear in the size of the output image. Experiments demonstrate that this approach offers a 25% lower background variance on average than alternating projections, the ptychographic reconstruction algorithm that is currently in widespread use. PMID:26146480
On the convexity of relativistic hydrodynamics
NASA Astrophysics Data System (ADS)
Ibáñez, José M.; Cordero-Carrión, Isabel; Martí, José M.; Miralles, Juan A.
2013-03-01
The relativistic hydrodynamic system of equations for a perfect fluid obeying a causal equation of state is hyperbolic (Anile 1989 Relativistic Fluids and Magneto-Fluids (Cambridge: Cambridge University Press)). In this report, we derive the conditions for this system to be convex in terms of the fundamental derivative of the equation of state (Menikoff and Plohr1989 Rev. Mod. Phys. 61 75). The classical limit is recovered. Communicated by L Rezzolla
Convex relaxations for gas expansion planning
Borraz-Sanchez, Conrado; Bent, Russell Whitford; Backhaus, Scott N.; Hijazi, Hassan; Van Hentenryck, Pascal
2016-01-01
Expansion of natural gas networks is a critical process involving substantial capital expenditures with complex decision-support requirements. Here, given the non-convex nature of gas transmission constraints, global optimality and infeasibility guarantees can only be offered by global optimisation approaches. Unfortunately, state-of-the-art global optimisation solvers are unable to scale up to real-world size instances. In this study, we present a convex mixed-integer second-order cone relaxation for the gas expansion planning problem under steady-state conditions. The underlying model offers tight lower bounds with high computational efficiency. In addition, the optimal solution of the relaxation can often be used to derive high-quality solutions to the original problem, leading to provably tight optimality gaps and, in some cases, global optimal solutions. The convex relaxation is based on a few key ideas, including the introduction of flux direction variables, exact McCormick relaxations, on/off constraints, and integer cuts. Numerical experiments are conducted on the traditional Belgian gas network, as well as other real larger networks. The results demonstrate both the accuracy and computational speed of the relaxation and its ability to produce high-quality solution
Convex relaxations for gas expansion planning
Borraz-Sanchez, Conrado; Bent, Russell Whitford; Backhaus, Scott N.; Hijazi, Hassan; Van Hentenryck, Pascal
2016-01-01
Expansion of natural gas networks is a critical process involving substantial capital expenditures with complex decision-support requirements. Here, given the non-convex nature of gas transmission constraints, global optimality and infeasibility guarantees can only be offered by global optimisation approaches. Unfortunately, state-of-the-art global optimisation solvers are unable to scale up to real-world size instances. In this study, we present a convex mixed-integer second-order cone relaxation for the gas expansion planning problem under steady-state conditions. The underlying model offers tight lower bounds with high computational efficiency. In addition, the optimal solution of the relaxation can often be used to derive high-quality solutionsmore » to the original problem, leading to provably tight optimality gaps and, in some cases, global optimal solutions. The convex relaxation is based on a few key ideas, including the introduction of flux direction variables, exact McCormick relaxations, on/off constraints, and integer cuts. Numerical experiments are conducted on the traditional Belgian gas network, as well as other real larger networks. The results demonstrate both the accuracy and computational speed of the relaxation and its ability to produce high-quality solution« less
Generalized vector calculus on convex domain
NASA Astrophysics Data System (ADS)
Agrawal, Om P.; Xu, Yufeng
2015-06-01
In this paper, we apply recently proposed generalized integral and differential operators to develop generalized vector calculus and generalized variational calculus for problems defined over a convex domain. In particular, we present some generalization of Green's and Gauss divergence theorems involving some new operators, and apply these theorems to generalized variational calculus. For fractional power kernels, the formulation leads to fractional vector calculus and fractional variational calculus for problems defined over a convex domain. In special cases, when certain parameters take integer values, we obtain formulations for integer order problems. Two examples are presented to demonstrate applications of the generalized variational calculus which utilize the generalized vector calculus developed in the paper. The first example leads to a generalized partial differential equation and the second example leads to a generalized eigenvalue problem, both in two dimensional convex domains. We solve the generalized partial differential equation by using polynomial approximation. A special case of the second example is a generalized isoperimetric problem. We find an approximate solution to this problem. Many physical problems containing integer order integrals and derivatives are defined over arbitrary domains. We speculate that future problems containing fractional and generalized integrals and derivatives in fractional mechanics will be defined over arbitrary domains, and therefore, a general variational calculus incorporating a general vector calculus will be needed for these problems. This research is our first attempt in that direction.
Manufacturing and testing of a convex aspherical mirror for ASSIST
NASA Astrophysics Data System (ADS)
ter Horst, Rik; Stuik, Remko
2012-09-01
ASSIST is the testbed for the ESO Adaptive Optics Facility. The main objective of ASSIST is the characterization of the 1.2 meter deformable mirror which will replace the existing secondary of one of the 8 meter VLT telescopes. A large concave 1.65 meter diameter aspherical primary mirror combined with a 140 mm diameter convex aspherical secondary forms the main optical system of ASSIST. Two additional optical units provide the light sources and the wave front analyzing optics. Without having the possibility for checking the entire optical system as a whole, each individual mirror had to be manufactured and tested using reliable techniques. The secondary mirror for ASSIST (AM2) is made of an optically transparent material (BK7) with a specific and accurate backside radius in order to achieve a null test in transmission. Furthermore, not only the overall RMS surface error of AM2 is important, but due to the fact that it will be used in a setup that measures specific spatial frequencies, also the spatial frequencies of the surface error of AM2 is important. The aspherical surface is tested in double pass using an optical flat and an interferometer with a transmission sphere. Manufacturing of this asphere is mainly done by hand at the optical lab of NOVA-ASTRON. The final accuracy of the reflecting surface is within the required 50 nm RMS with a surface roughness of less than 2 nm RMS. This paper reports in more detail on manufacturing and testing of the a-spherical convex mirror.
Rapid Generation of Optimal Asteroid Powered Descent Trajectories Via Convex Optimization
NASA Technical Reports Server (NTRS)
Pinson, Robin; Lu, Ping
2015-01-01
This paper investigates a convex optimization based method that can rapidly generate the fuel optimal asteroid powered descent trajectory. The ultimate goal is to autonomously design the optimal powered descent trajectory on-board the spacecraft immediately prior to the descent burn. Compared to a planetary powered landing problem, the major difficulty is the complex gravity field near the surface of an asteroid that cannot be approximated by a constant gravity field. This paper uses relaxation techniques and a successive solution process that seeks the solution to the original nonlinear, nonconvex problem through the solutions to a sequence of convex optimal control problems.
NASA Astrophysics Data System (ADS)
Sizyuk, Tatyana; Hassanein, Ahmed
2015-03-01
The present work studies the combined effects of collisional sputtering and mixing processes of carbon impurities in tungsten plasma-facing material integrated with thermal processes including surface segregation and diffusion. We used our ITMC-DYN package, which includes description of all collisional and thermal processes, for the analysis of recent experimental results of tungsten erosion and carbon implantation at various target temperatures. Self-consistent integrated modeling predicted thermal processes effects on erosion/deposition dynamics and defined decisive parameters range and their importance. Critical parameters were estimated based on available experimental data. The integrated simulation reproduced the experimental results and predicted the transition from enhanced tungsten erosion to significant carbon coverage on the tungsten surface. These effects for wider range of system conditions with C/H ions irradiation and for reactor conditions can be predicted by including detailed modeling of chemical erosion processes in a self-consistent manner.
NASA Astrophysics Data System (ADS)
Mason, L. J.; Pederson, D. T.; Goble, R. J.
2004-12-01
More than 200 waterfalls exist along the southern spring branch tributaries that feed an approximately twenty-five mile section of the Niobrara River, east of Valentine, Nebraska. Many of these waterfalls posses a convex shape in the horizontal plane and are buttressed. This morphology is controlled by focused, season-specific weathering along the escarpments adjacent to the waterfall face and a lack of stream erosion on the actual waterfall face. The waterfalls are composed of the Rosebud Formation, a poorly indurated siltstone that should be easily eroded by stream flow. The spring creeks are ineffective at significantly eroding the waterfall face mainly due to their relatively low discharge, three to five cubic feet per second, and low sediment load. The erosive power of the streams is further reduced at the site of the waterfall by the buttressed shape spreading the flow into a thin sheet. The buttressed shape of the waterfall develops in response to stress relief. The only areas of the waterfall face showing stream erosion and lack of diatom cover is where free falling water is impacting the waterfall face. Large, loose talus slopes at the base of the waterfall escarpments further support that the weathering processes operate at a faster rate than stream erosion. Observable groundwater seepage from the escarpments on either side of the waterfalls exposes the faces to season-specific weathering processes. The moisture content of the escarpments varies with exposure to sunlight and changes in air temperature. Cyclic differential expansion and contraction of clays and minerals as well as precipitation and hydration of salts operate on a daily and seasonal basis. These repeated stresses give the escarpments a flaky, shingle like appearance and can cause rapid deterioration of the escarpment. During the winter, the seeping groundwater and waterfall spray form large ice flows on either side of the waterfall face. Freeze-thaw processes operate on a seasonal and
Deuterium retention enhancement in lithiated graphite plasma-facing surfaces in fusion devices
NASA Astrophysics Data System (ADS)
Allain, Jean Paul
2011-10-01
Lithium conditioning has been adopted in a number of magnetic confinement devices resulting in significant effects on plasma performance. In NSTX for example effects include: reduction of ELMs, reduced edge neutral density, increased pedestal electron and ion temperature, and improved energy confinement. The main assumption conjectured for the effects observed in NSTX plasmas is the retention of hydrogen by coatings of lithium on ATJ graphite tile surfaces. The main binding channel understood to be the ionic lithium hydride bond. However, the likelihood that the dominant retention mechanism is governed by lithium-hydride bonding seems less probable based on well-known intercalation effects of lithium in graphite. The observed effects on plasma behavior in NSTX, despite the strong chemical interaction of D, Li, O and carbon, indicate an enhanced mechanism for retaining hydrogen in addition to Li-D binding. This paper summarizes the key mechanisms understood today of enhanced hydrogen retention in lithium-treated ATJ graphite surfaces. The mechanisms are elucidated by four major efforts: 1) controlled in-situ off-line experiments at Purdue,, 2) post-mortem NSTX tile analysis, 3) in-vacuo PMI probe data in NSTX, and 4) computational quantum-based atomistic simulations. Results show that a saturation limit of D pumping by lithium conditioning of ATJ graphite surfaces is reached in a few number of shots. Computational modeling using semi-empirical quantum mechanics of electrons and classical mechanics of nuclei elucidate on the polar-covalent interactions that emerge between lithium and the C-D-O system.
Morphological convexity measures for terrestrial basins derived from digital elevation models
NASA Astrophysics Data System (ADS)
Lim, Sin Liang; Daya Sagar, B. S.; Chet Koo, Voon; Tien Tay, Lea
2011-09-01
Geophysical basins of terrestrial surfaces have been quantitatively characterized through a host of indices such as topological quantities (e.g. channel bifurcation and length ratios), allometric scaling exponents (e.g. fractal dimensions), and other geomorphometric parameters (channel density, Hack's and Hurst exponents). Channel density, estimated by taking the ratio between the length of channel network ( L) and the area of basin ( A) in planar form, provides a quantitative index that has hitherto been related to various geomorphologically significant processes. This index, computed by taking the planar forms of channel network and its corresponding basin, is a kind of convexity measure in the two-dimensional case. Such a measure - estimated in general as a function of basin area and channel network length, where the important elevation values of the topological region within a basin and channel network are ignored - fails to capture the spatial variability between homotopic basins possessing different altitude-ranges. Two types of convexity measures that have potential to capture the terrain elevation variability are defined as the ratio of (i) length of channel network function and area of basin function and (ii) areas of basin and its convex hull functions. These two convexity measures are estimated in three data sets that include (a) synthetic basin functions, (b) fractal basin functions, and (c) realistic digital elevation models (DEMs) of two regions of peninsular Malaysia. It is proven that the proposed convexity measures are altitude-dependent and that they could capture the spatial variability across the homotopic basins of different altitudes. It is also demonstrated on terrestrial DEMs that these convexity measures possess relationships with other quantitative indexes such as fractal dimensions and complexity measures (roughness indexes).
NASA Astrophysics Data System (ADS)
Luo, Yongkun; Qin, Rongshan
2014-06-01
The structure and the anisotropic properties of the surfaces of face-centred-cubic (FCC) metals have been studied using the broken-bond model while considering the third and fourth nearest neighbouring (3rd and 4th NN) interactions. The pair potential expressions are obtained using the Rose-Vinet universal potential equation. The model is suitable for calculation of the property of a surface with arbitrary crystallographic orientations and can provide absolute unrelaxed surface energy values using three input parameters, namely the lattice constant, bulk modulus and cohesive energy. These parameters are available for the majority of FCC metals. The numerical results for 7 FCC metals have been obtained and compared with these obtained from ab initio calculations and experimental measurements. Good agreement is observed between the two. Taking into account up to the 4th NN interactions, the overall surface energy anisotropy for FCC metals was found to be between 12% to 16%, and the ratio between the surface energies at (100) and (111) planes was found to be 1.05. These values are less than those reported by conventional calculations but more similar to experimental measurements. It is found that the strength of 3rd and 4th NN interactions differs from one element to another, the Ni and Cu interactions being the most significant while the Au, Pt and Pb interactions are the least significant. This suggests that the polar diagrams of the surface energy of Ni and Cu are different from those of Au, Pt and Pb by showing cusps of the unconventional {110} and high-index {210}, {311} and possibly {135} poles. This provides explanations to the recent experimental observations of the {110}, {210}, {311} and {135} facets in equilibrated Ni and Cu crystallines.
CVXPY: A Python-Embedded Modeling Language for Convex Optimization
Diamond, Steven; Boyd, Stephen
2016-01-01
CVXPY is a domain-specific language for convex optimization embedded in Python. It allows the user to express convex optimization problems in a natural syntax that follows the math, rather than in the restrictive standard form required by solvers. CVXPY makes it easy to combine convex optimization with high-level features of Python such as parallelism and object-oriented design. CVXPY is available at http://www.cvxpy.org/ under the GPL license, along with documentation and examples. PMID:27375369
Hirooka, Yoshi; Ohgaki, Hirotsugu; Hosaka, Souichirou; Ohtsuka, Yusuke; Nishikawa, Masahiro
2005-04-15
In our previous work, the first proof-of-principle experiments were successfully conducted on the particle control capability based on the concept of moving-surface plasma-facing component (MS-PFC). Over a continuously titanium-gettered rotating drum, hydrogen recycling was found to be reduced down to levels around 94% even at steady state. These experiments on the MS-PFC concept have now been extended to the second stage where lithium is employed as the getter material, while using the same rotating drum. These experiments are intended to pilot the potential use of lithium as a flowing liquid facing the edge plasmas in steady state reactors beyond ITER. Reported in this paper are rather dramatic findings that hydrogen recycling is reduced down to levels around 76% and 86% at steady state over the rotating drum at the lithium deposition rates of 9.5 A/s and 7.3 A/s, respectively. These steady state recycling data have been nicely reproduced by a simple zero-dimensional particle balance model.
Regression models for convex ROC curves.
Lloyd, C J
2000-09-01
The performance of a diagnostic test is summarized by its receiver operating characteristic (ROC) curve. Under quite natural assumptions about the latent variable underlying the test, the ROC curve is convex. Empirical data on a test's performance often comes in the form of observed true positive and false positive relative frequencies under varying conditions. This paper describes a family of regression models for analyzing such data. The underlying ROC curves are specified by a quality parameter delta and a shape parameter mu and are guaranteed to be convex provided delta > 1. Both the position along the ROC curve and the quality parameter delta are modeled linearly with covariates at the level of the individual. The shape parameter mu enters the model through the link functions log(p mu) - log(1 - p mu) of a binomial regression and is estimated either by search or from an appropriate constructed variate. One simple application is to the meta-analysis of independent studies of the same diagnostic test, illustrated on some data of Moses, Shapiro, and Littenberg (1993). A second application, to so-called vigilance data, is given, where ROC curves differ across subjects and modeling of the position along the ROC curve is of primary interest. PMID:10985227
NASA Astrophysics Data System (ADS)
Yashkin, S. N.; Svetlov, D. A.; Klimochkin, Yu. N.
2011-10-01
The thermodynamic characteristics of adsorption (TCA) for isomeric molecules of mono-, di-, tri-, and tetrafluoroadamantanes were determined for the first time experimentally and by molecular statistics on the surface of graphitized thermal black (GTB). The parameters of atom-atom potential function of pair intermolecular interaction (φ( r)) for F atoms included in fluoroadamantanes with C atoms on the basal face of graphite were calculated for the first time within an atom-atom approximation of the semi-empirical molecular statistical theory of adsorption. The adsorption non-equivalence of F atoms in various positions of an adamantane framework, a consequence of the mutual effect of atoms in a framework molecule, was determined. On the basis of the definite TCA values, the conclusion was drawn as to the possibility of isolation of isomeric fluoroadamantanes under the conditions of gas-adsorption chromatography on GTB.
Cheung, F.B.; Haddad, K.H.
1996-03-01
Steady-state boiling experiments were performed in the SBLB test facility to observe the two-phase boundary layer flow behavior on the outer surface of a heated hemispherical vessel near the critical heat flux (CHF) limit and to measure the spatial variation of the local CHF along the vessel outer surface. Based upon the flow observations, an advanced hydrodynamic CHF model was developed. The model considers the existence of a micro-layer underneath an elongated vapor slug on the downward facing curved heating surface. The micro-layer is treated as a thin liquid film with numerous micro-vapor jets penetrating through it. The micro-jets have the characteristic size dictated by Helmholtz instability. Local dryout is considered to occur when the supply of fresh liquid from the two phase boundary layer to the micro-layer is not sufficient to prevent depletion of the liquid film by boiling. A boundary layer analysis, treating the two-phase motion as a separated flow, is performed to determine the liquid supply rate and thus the local critical heat flux. The model provides a clear physical explanation for the spatial variation of the CHF observed in the SBLB experiments and for the weak dependence of the CHF data on the physical size of the vessel.
El-Genk, M.S.; Glebov, A.G.
1995-09-01
Quenching experiments were performed to investigate the effects of water subcooling and wall thickness on pool boiling from a downward-facing curved surface. Experiments used three copper sections of the same diameter (50.8 mm) and surface radius (148 mm), but different thickness (12.8, 20 and 30 mm). Local and average pool boiling curves were obtained at saturation and 5 K, 10 K, and 14 K subcooling. Water subcooling increased the maximum heat flux, but decreased the corresponding wall superheat. The minimum film boiling heat flux and the corresponding wall superheat, however, increased with increased subcooling. The maximum and minimum film boiling heat fluxes were independent of wall thickness above 20 mm and Biot Number > 0.8, indicating that boiling curves for the 20 and 30 thick sections were representative of quasi steady-state, but not those for the 12.8 mm thick section. When compared with that for a flat surface section of the same thickness, the data for the 12.8 mm thick section showed significant increases in both the maximum heat flux (from 0.21 to 0.41 MW/m{sup 2}) and the minimum film boiling heat flux (from 2 to 13 kW/m{sup 2}) and about 11.5 K and 60 K increase in the corresponding wall superheats, respectively.
Material probe analysis for plasma facing surface in the Large Helical Device
NASA Astrophysics Data System (ADS)
Hino, T.; Sagara, A.; Nobuta, Y.; Inoue, N.; Hirohata, Y.; Yamauchi, Y.; Masuzaki, S.; Noda, N.; Suzuki, H.; Komori, A.; Ohyabu, N.; Motojima, O.; LHD Experimental Group
2004-04-01
Material probes have been installed at the inner walls along the poloidal direction in large helical device (LHD) from the first experimental campaign. After each campaign, the impurity deposition and the gas retention have been examined to study the plasma surface interaction and the degree of wall cleaning. In the 2nd campaign, the entire wall was thoroughly cleaned by glow discharge conditioning and the number of main discharge shots increased. For the 3rd and 4th campaigns, graphite tiles were installed over the entire divertor strike region, and then the wall condition was significantly changed compared with the case of a stainless steel (SS) wall. It was seen that graphite tiles in the divertor were eroded mainly during main discharges, and the SS first wall mainly during glow discharges. During main discharges the eroded carbon was deposited on the entire wall. A reduction of metal impurities in the plasma was observed, which corresponds to the carbonized wall. The deposition thickness was great at the wall far from the plasma. Since the entire wall was carbonized, the amount of discharge gases retained such as H and He became large. In particular, helium retention was large at a position close to the anodes used for helium glow discharge cleanings. One characteristic of the LHD wall is a large retention of helium since the wall temperature is limited to below 368 K. In order to reduce the recycling of the discharge gas, wall heating is necessary.
NASA Astrophysics Data System (ADS)
Chiwa, M.; Oshiro, N.; Miyake, T.; Nakatani, N.; Kimura, N.; Yuhara, T.; Hashimoto, N.; Sakugawa, H.
Dry deposition and dew components on pine foliage were measured from 1998 to 2000 on the urban- and mountain-facing sides of Mt. Gokurakuji in order to estimate the effect of anthropogenic activities to dry deposition and dew concentration on the surfaces of pine foliage. A leaf wash experiment was employed to determine the dry deposition rates on the pine foliage. The NO 3- and SO 42- dry deposition rates per unit surface area of pine foliage were 1.47 and 0.28 μmol m -2 h -1 respectively on the urban-facing side and 0.32 and 0.09 μmol m -2 h -1 on the mountain-facing side. Dry deposition fluxes of N (NO 3-+NH 4+) and S (SO 42-) to the forest floors were 8.4 kg N ha -1 yr -1 and 2.8 kg S ha -1 yr -1 on the urban-facing, and 3.3 kg N ha -1 yr -1 and 1.8 kg S ha -1 yr -1 on the mountain-facing side, respectively. The higher dry deposition fluxes of N and S on the urban-facing side could be attributed to its proximity to traffic roads and the urban area. The concentrations of most ions in the dew were higher on the urban-facing side (U130) than on the mountain-facing side (M430). NO 3- and SO 42- concentrations in dew at U130 were 802 and 428 μeq l -1, respectively, while at M430 they were 199 and 222 μeq l -1, respectively, suggesting that higher dry deposition rates on the urban-facing side enhanced their concentrations in the dew on this side. The role of dry deposits and subsequently dissolved ones in dew on the needle surfaces is discussed in terms of pine tree damage by atmospheric depositions.
NASA Astrophysics Data System (ADS)
Suslova, A.; El-Atwani, O.; Harilal, S. S.; Hassanein, A.
2015-03-01
We investigated the effect of edge-localized mode like transient heat events on pristine samples for two different grades of deformed tungsten with ultrafine and nanocrystalline grains as potential candidates for plasma-facing components. Pulses from a laser beam with durations ∼1 ms and operating in the near infrared wavelength were used for simulating transient heat loading in fusion devices. We specifically focused on investigating and analysis of different mechanisms for material removal from the sample surface under repetitive transient heat loads. Several techniques were applied for analysing different mechanisms leading to material removal from the W surface under repetitive transient heat loads which include witness plates for collected ejected material, and subsequent analysis using x-ray photoelectron spectroscopy and scanning electron microscopy, visible imaging using fast-gated camera, and evaluating thermal emission from the particles using optical emission spectroscopy. Our results show a significantly improved performance of polycrystalline cold-rolled tungsten compared to tungsten produced using an orthogonal machining process under repetitive transient loads for a wide range of the power densities.
NASA Astrophysics Data System (ADS)
Kihm, K. D.; Cheeti, S. K. R.
1994-08-01
A laser specklegram or speckle photography technique allows a direct measurement of surface temperature gradients and provides a full field interrogation with an extremely high resolution from a single data taking. The specklegram technique has been successfully applied to investigate the natural convection heat transfer from an upward-facing isothermal plate. For a plate with a large aspect ratio of 15, both local and global Nusselt numbers have been determined from the direct measurement of local temperature gradients. The Rayleigh number, based on the length scale equivalent to the ratio of the surface area to the perimeter, has been varied from 9.0 × 103 to 4.0 × 104. The present result for the global heat transfer has shown that a 1/5-power law, i.e., Nu = C1 Ra 1/5, correlates the data more properly whilst previously published results showed a large scatter in the exponent, ranging from 1/8-power to 1/4-power. The proportional constant, C1 has been determined to be 0.56 which shows a fairly good agreement with previously published theoretical results. The laser specklegram technique has shown a strong potential as a powerful and convenient method for an experimental assessment of natural convection heat transfer problems. The specklegram technique at the same time has eliminated the deficiencies of both the mass transfer analogy technique and the classical heat transfer measurement technique.
Convex Lower Bounds for Free Energy Minimization
NASA Astrophysics Data System (ADS)
Moussa, Jonathan
We construct lower bounds on free energy with convex relaxations from the nonlinear minimization over probabilities to linear programs over expectation values. Finite-temperature expectation values are further resolved into distributions over energy. A superset of valid expectation values is delineated by an incomplete set of linear constraints. Free energy bounds can be improved systematically by adding constraints, which also increases their computational cost. We compute several free energy bounds of increasing accuracy for the triangular-lattice Ising model to assess the utility of this method. This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.
Imaging spectrometer/camera having convex grating
NASA Technical Reports Server (NTRS)
Reininger, Francis M. (Inventor)
2000-01-01
An imaging spectrometer has fore-optics coupled to a spectral resolving system with an entrance slit extending in a first direction at an imaging location of the fore-optics for receiving the image, a convex diffraction grating for separating the image into a plurality of spectra of predetermined wavelength ranges; a spectrometer array for detecting the spectra; and at least one concave sperical mirror concentric with the diffraction grating for relaying the image from the entrance slit to the diffraction grating and from the diffraction grating to the spectrometer array. In one embodiment, the spectrometer is configured in a lateral mode in which the entrance slit and the spectrometer array are displaced laterally on opposite sides of the diffraction grating in a second direction substantially perpendicular to the first direction. In another embodiment, the spectrometer is combined with a polychromatic imaging camera array disposed adjacent said entrance slit for recording said image.
On some interpolation properties in locally convex spaces
Pater, Flavius
2015-03-10
The aim of this paper is to introduce the notion of interpolation between locally convex spaces, the real method, and to present some elementary results in this setting. This represents a generalization from the Banach spaces framework to the locally convex spaces sequentially complete one, where the operators acting on them are locally bounded.
Infants' Perception of Information along Object Boundaries: Concavities versus Convexities
ERIC Educational Resources Information Center
Bhatt, Ramesh S.; Hayden, Angela; Reed, Andrea; Bertin, Evelin; Joseph, Jane
2006-01-01
Object parts are signaled by concave discontinuities in shape contours. In seven experiments, we examined whether 5- and 6 1/2-month-olds are sensitive to concavities as special aspects of contours. Infants of both ages detected discrepant concave elements amid convex distractors but failed to discriminate convex elements among concave…
Study on the method to test large-aperture hyperboloid convex mirror
NASA Astrophysics Data System (ADS)
Meng, Xiaohui; Dong, Huiwen; Guo, Wen; Wang, Huijun
2014-08-01
There are numerous reflecting optical system designs that call for large-aperture convex surfaces, such as secondary mirror in on-axis three mirror anastigmatic (TMA). Several methods to test high accuracy hyperboloid convex surfaces are introduced separately in this paper. A kind of arrangement is chosen to test a surface with diameter of 420mm, radius of 1371mm, and conic K -2.1229. The CGH compensator for testing is designed, which is made up of illumination lens and hologram test plate with designed residual wavefront aberration less than 0.001λ (RMS). The second transmitted method that is equipped with a technical flat surface coating by Ag film in the bottom of surface mirror under test, which form an auto-collimation optical system to eliminate the aberration. The Hindle-Simpson test that requires a larger meniscus lens to compensate the optical aberration, and the designed result of optical test system is less than 0.0016λ. Contrasting the CGH compensator and the second transmitted method, the Hindle-Simpson testing method has the advantage of it is easily to manufacture and adjust; meanwhile the test result is stable and has been less affected by the environment. It has been found that the method is rational and reliable, and it can fulfill the requirement of manufacturing and testing process for hyperboloid convex mirrors.
CPU timing routines for a CONVEX C220 computer system
NASA Technical Reports Server (NTRS)
Bynum, Mary Ann
1989-01-01
The timing routines available on the CONVEX C220 computer system in the Structural Mechanics Division (SMD) at NASA Langley Research Center are examined. The function of the timing routines, the use of the timing routines in sequential, parallel, and vector code, and the interpretation of the results from the timing routines with respect to the CONVEX model of computing are described. The timing routines available on the SMD CONVEX fall into two groups. The first group includes standard timing routines generally available with UNIX 4.3 BSD operating systems, while the second group includes routines unique to the SMD CONVEX. The standard timing routines described in this report are /bin/csh time,/bin/time, etime, and ctime. The routines unique to the SMD CONVEX are getinfo, second, cputime, toc, and a parallel profiling package made up of palprof, palinit, and palsum.
Fabrication of ф 160 mm convex hyperbolic mirror for remote sensing instrument
NASA Astrophysics Data System (ADS)
Kuo, Ching-Hsiang; Yu, Zong-Ru; Ho, Cheng-Fang; Hsu, Wei-Yao; Chen, Fong-Zhi
2012-10-01
In this study, efficient polishing processes with inspection procedures for a large convex hyperbolic mirror of Cassegrain optical system are presented. The polishing process combines the techniques of conventional lapping and CNC polishing. We apply the conventional spherical lapping process to quickly remove the sub-surface damage (SSD) layer caused by grinding process and to get the accurate radius of best-fit sphere (BFS) of aspheric surface with fine surface texture simultaneously. Thus the removed material for aspherization process can be minimized and the polishing time for SSD removal can also be reduced substantially. The inspection procedure was carried out by using phase shift interferometer with CGH and stitching technique. To acquire the real surface form error of each sub aperture, the wavefront errors of the reference flat and CGH flat due to gravity effect of the vertical setup are calibrated in advance. Subsequently, we stitch 10 calibrated sub-aperture surface form errors to establish the whole irregularity of the mirror in 160 mm diameter for correction polishing. The final result of the In this study, efficient polishing processes with inspection procedures for a large convex hyperbolic mirror of Cassegrain optical system are presented. The polishing process combines the techniques of conventional lapping and CNC polishing. We apply the conventional spherical lapping process to quickly remove the sub-surface damage (SSD) layer caused by grinding process and to get the accurate radius of best-fit sphere (BFS) of aspheric surface with fine surface texture simultaneously. Thus the removed material for aspherization process can be minimized and the polishing time for SSD removal can also be reduced substantially. The inspection procedure was carried out by using phase shift interferometer with CGH and stitching technique. To acquire the real surface form error of each sub aperture, the wavefront errors of the reference flat and CGH flat due to
A scalable projective scaling algorithm for l(p) loss with convex penalizations.
Zhou, Hongbo; Cheng, Qiang
2015-02-01
This paper presents an accurate, efficient, and scalable algorithm for minimizing a special family of convex functions, which have a lp loss function as an additive component. For this problem, well-known learning algorithms often have well-established results on accuracy and efficiency, but there exists rarely any report on explicit linear scalability with respect to the problem size. The proposed approach starts with developing a second-order learning procedure with iterative descent for general convex penalization functions, and then builds efficient algorithms for a restricted family of functions, which satisfy the Karmarkar's projective scaling condition. Under this condition, a light weight, scalable message passing algorithm (MPA) is further developed by constructing a series of simpler equivalent problems. The proposed MPA is intrinsically scalable because it only involves matrix-vector multiplication and avoids matrix inversion operations. The MPA is proven to be globally convergent for convex formulations; for nonconvex situations, it converges to a stationary point. The accuracy, efficiency, scalability, and applicability of the proposed method are verified through extensive experiments on sparse signal recovery, face image classification, and over-complete dictionary learning problems. PMID:25608289
Schein, Stan; Gayed, James Maurice
2014-01-01
The three known classes of convex polyhedron with equal edge lengths and polyhedral symmetry––tetrahedral, octahedral, and icosahedral––are the 5 Platonic polyhedra, the 13 Archimedean polyhedra––including the truncated icosahedron or soccer ball––and the 2 rhombic polyhedra reported by Johannes Kepler in 1611. (Some carbon fullerenes, inorganic cages, icosahedral viruses, geodesic structures, and protein complexes resemble these fundamental shapes.) Here we add a fourth class, “Goldberg polyhedra,” which are also convex and equilateral. We begin by decorating each of the triangular facets of a tetrahedron, an octahedron, or an icosahedron with the T vertices and connecting edges of a “Goldberg triangle.” We obtain the unique set of internal angles in each planar face of each polyhedron by solving a system of n equations and n variables, where the equations set the dihedral angle discrepancy about different types of edge to zero, and the variables are a subset of the internal angles in 6gons. Like the faces in Kepler’s rhombic polyhedra, the 6gon faces in Goldberg polyhedra are equilateral and planar but not equiangular. We show that there is just a single tetrahedral Goldberg polyhedron, a single octahedral one, and a systematic, countable infinity of icosahedral ones, one for each Goldberg triangle. Unlike carbon fullerenes and faceted viruses, the icosahedral Goldberg polyhedra are nearly spherical. The reasoning and techniques presented here will enable discovery of still more classes of convex equilateral polyhedra with polyhedral symmetry. PMID:24516137
Razavi, Sonia M; Gonzalez, Marcial; Cuitiño, Alberto M
2015-04-30
We propose a general framework for determining optimal relationships for tensile strength of doubly convex tablets under diametrical compression. This approach is based on the observation that tensile strength is directly proportional to the breaking force and inversely proportional to a non-linear function of geometric parameters and materials properties. This generalization reduces to the analytical expression commonly used for flat faced tablets, i.e., Hertz solution, and to the empirical relationship currently used in the pharmaceutical industry for convex-faced tablets, i.e., Pitt's equation. Under proper parametrization, optimal tensile strength relationship can be determined from experimental results by minimizing a figure of merit of choice. This optimization is performed under the first-order approximation that a flat faced tablet and a doubly curved tablet have the same tensile strength if they have the same relative density and are made of the same powder, under equivalent manufacturing conditions. Furthermore, we provide a set of recommendations and best practices for assessing the performance of optimal tensile strength relationships in general. Based on these guidelines, we identify two new models, namely the general and mechanistic models, which are effective and predictive alternatives to the tensile strength relationship currently used in the pharmaceutical industry. PMID:25683146
Cromrich, J.; Cromrich, L.B.
1990-10-16
This patent describes a method for forming insulated brick intended solely for use in building walls and having superior insulation qualities and lighter weight consonant with the load bearing capabilities of building bricks and the appearance of facing brick. It comprises dry mixing two parts of vermiculite and one part of brick clay, thereby forming a dry mixture having a vermiculite to clay ratio of approximately two-to-one by volume; adding water to the dry mixture and mixing, so that a substantially dry admixture having expanded vermiculite and brick clay is formed; forming a facing layer solely from brick clay; molding and compressing the substantially dry admixture, so as to form a generally rectangular main body layer having parallel top and bottom faces, a pair of parallel side faces and a pair of parallel end faces, respectively, the top and bottom faces being substantially larger in area than the respective side faces, and the side faces being substantially larger in area than the respective end faces, the body layer further having at least one bore formed therein, the bore running from the top face to the bottom face perpendicularly thereto and substantially parallel to the side surfaces thereof, the bore being substantially centrally disposed and wherein the facing layer is disposed on one of the side surfaces of the body portion; curing the molded admixture having the facing layer disposed thereon; whereby a cured brick is formed; and firing the cured brick and the facing layer disposed thereon, whereby an integral brick is formed having top and bottom faces of the brick which are entirely devoid of facing layers, wherein the brick has the desired load bearing capability substantially between its top and bottom faces, whereby the outer facing layer only provides the desired appearance and weather resistance, and further whereby the weight of the brick is substantially reduced.
Nonparametric illumination correction for scanned document images via convex hulls.
Meng, Gaofeng; Xiang, Shiming; Zheng, Nanning; Pan, Chunhong
2013-07-01
A scanned image of an opened book page often suffers from various scanning artifacts known as scanning shading and dark borders noises. These artifacts will degrade the qualities of the scanned images and cause many problems to the subsequent process of document image analysis. In this paper, we propose an effective method to rectify these scanning artifacts. Our method comes from two observations: that the shading surface of most scanned book pages is quasi-concave and that the document contents are usually printed on a sheet of plain and bright paper. Based on these observations, a shading image can be accurately extracted via convex hulls-based image reconstruction. The proposed method proves to be surprisingly effective for image shading correction and dark borders removal. It can restore a desired shading-free image and meanwhile yield an illumination surface of high quality. More importantly, the proposed method is nonparametric and thus does not involve any user interactions or parameter fine-tuning. This would make it very appealing to nonexpert users in applications. Extensive experiments based on synthetic and real-scanned document images demonstrate the efficiency of the proposed method. PMID:23681999
Faceted Gold Nanorods: Nanocuboids, Convex Nanocuboids, and Concave Nanocuboids.
Zhang, Qingfeng; Zhou, Yadong; Villarreal, Esteban; Lin, Ye; Zou, Shengli; Wang, Hui
2015-06-10
Au nanorods are optically tunable anisotropic nanoparticles with built-in catalytic activities. The state-of-the-art seed-mediated nanorod synthesis offers excellent control over the aspect ratios of cylindrical Au nanorods, which enables fine-tuning of plasmon resonances over a broad spectral range. However, facet control of Au nanorods with atomic-level precision remains significantly more challenging. The coexistence of various types of low-index and high-index facets on the highly curved nanorod surfaces makes it extremely challenging to quantitatively elucidate the atomic-level structure-property relationships that underpin the catalytic competence of Au nanorods. Here we demonstrate that cylindrical Au nanorods undergo controlled facet evolution during their overgrowth in the presence of Cu(2+) and cationic surfactants, resulting in the formation of anisotropic nanostructures enclosed by well-defined facets, such as low-index faceting nanocuboids and high-index faceting convex nanocuboids and concave nanocuboids. These faceted Au nanorods exhibit enriched optical extinction spectral features, broader plasmonic tuning range, and enhanced catalytic tunability in comparison to the conventional cylindrical Au nanorods. The capabilities to both fine-tailor the facets and fine-tune the plasmon resonances of anisotropic Au nanoparticles open up unique opportunities for us to study, in great detail, the facet-dependent interfacial molecular transformations on Au nanocatalysts using surface-enhanced Raman scattering as a time-resolved spectroscopic tool. PMID:25927399
Convex Image Orientation from Relative Orientations
NASA Astrophysics Data System (ADS)
Reich, M.; Heipke, C.
2016-06-01
In this paper we propose a novel workflow for the estimation of global image orientations given relative orientations between pairs of overlapping images. Our approach is convex and independent on initial values. First, global rotations are estimated in a relaxed semidefinite program (SDP) and refined in an iterative least squares adjustment in the tangent space of SO(3). A critical aspect is the handling of outliers in the relative orientations. We present a novel heuristic graph based approach for filtering the relative rotations that outperforms state-of-the-art robust rotation averaging algorithms. In a second part we make use of point-observations, tracked over a set of overlapping images and formulate a linear homogeneous system of equations to transfer the scale information between triplets of images, using estimated global rotations and relative translation directions. The final step consists of refining the orientation parameters in a robust bundle adjustment. The proposed approach handles outliers in the homologous points and relative orientations in every step of the processing chain. We demonstrate the robustness of the procedure on synthetic data. Moreover, the performance of our approach is illustrated on real world benchmark data.
Entropy and convexity for nonlinear partial differential equations
Ball, John M.; Chen, Gui-Qiang G.
2013-01-01
Partial differential equations are ubiquitous in almost all applications of mathematics, where they provide a natural mathematical description of many phenomena involving change in physical, chemical, biological and social processes. The concept of entropy originated in thermodynamics and statistical physics during the nineteenth century to describe the heat exchanges that occur in the thermal processes in a thermodynamic system, while the original notion of convexity is for sets and functions in mathematics. Since then, entropy and convexity have become two of the most important concepts in mathematics. In particular, nonlinear methods via entropy and convexity have been playing an increasingly important role in the analysis of nonlinear partial differential equations in recent decades. This opening article of the Theme Issue is intended to provide an introduction to entropy, convexity and related nonlinear methods for the analysis of nonlinear partial differential equations. We also provide a brief discussion about the content and contributions of the papers that make up this Theme Issue. PMID:24249768
Non-parametric Single View Reconstruction of Curved Objects Using Convex Optimization
NASA Astrophysics Data System (ADS)
Oswald, Martin R.; Töppe, Eno; Kolev, Kalin; Cremers, Daniel
We propose a convex optimization framework delivering intuitive and reasonable 3D meshes from a single photograph. For a given input image, the user can quickly obtain a segmentation of the object in question. Our algorithm then automatically generates an admissible closed surface of arbitrary topology without the requirement of tedious user input. Moreover we provide a tool by which the user is able to interactively modify the result afterwards through parameters and simple operations in a 2D image space. The algorithm targets a limited but relevant class of real world objects. The object silhouette and the additional user input enter a functional which can be optimized globally in a few seconds using recently developed convex relaxation techniques parallelized on state-of-the-art graphics hardware.
Convex Lens-induced Confinement to Visualize Biopolymers and Interaction Parameters
NASA Astrophysics Data System (ADS)
Stabile, Frank; Berard, Daniel; Henkin, Gil; Shayegan, Marjan; Michaud, François; Leslie, Sabrina
In this poster, we present a versatile CLiC (Convex Lens-induced Confinement) microscopy system to access a broad range of biopolymer visualization and interaction parameters. In the CLiC technique, the curved surface of a convex lens is used to deform a flexible coverslip above a glass substrate, creating a nanoscale gap that can be tuned during an experiment to load and confine molecules into nanoscale features, both linear and circular, embedded in the bottom substrate. We demonstrate and characterize massively parallel DNA nanochannel-based stretching, building on prior work. Further, we demonstrate controlled insertion of reagent molecules within the CLiC imaging chamber. We visualize real-time reaction dynamics of nanoconfined species, including dye/DNA intercalation and DNA/DNA ligation reactions, demonstrating the versatility of this nanoscale microscopy platform.
NASA Astrophysics Data System (ADS)
Borodkina, I. E.; Komm, M.; Tsvetkov, I. V.
2015-08-01
Simple analytical formulas are derived for calculation of the electric field potential distribution in the magnetic pre-layer and the Debye layer near the plasma facing surfaces. It is shown that the calculated potential profiles are in good agreement with the dependences of the potential distribution on the magnetic field inclination obtained by solving the magnetic hydrodynamic (MHD) equations and modeling using the PIC code SPICE2. Dependences of the angular distribution of ions incident on the surface of plasma facing elements on the magnetic field inclination are obtained. Results of calculations demonstrate that the surface areas, on which the magnetic field is incident at sliding angles, are critical from the viewpoint of the increase of sputtering.
Shape recognition: convexities, concavities and things in between.
Schmidtmann, Gunnar; Jennings, Ben J; Kingdom, Frederick A A
2015-01-01
Visual objects are effortlessly recognized from their outlines, largely irrespective of viewpoint. Previous studies have drawn different conclusions regarding the importance to shape recognition of specific shape features such as convexities and concavities. However, most studies employed familiar objects, or shapes without curves, and did not measure shape recognition across changes in scale and position. We present a novel set of random shapes with well-defined convexities, concavities and inflections (intermediate points), segmented to isolate each feature type. Observers matched the segmented reference shapes to one of two subsequently presented whole-contour shapes (target or distractor) that were re-scaled and re-positioned. For very short segment lengths, performance was significantly higher for convexities than for concavities or intermediate points and for convexities remained constant with increasing segment length. For concavities and intermediate points, performance improved with increasing segment length, reaching convexity performance only for long segments. No significant differences between concavities and intermediates were found. These results show for the first time that closed curvilinear shapes are encoded using the positions of convexities, rather than concavities or intermediate regions. A shape-template model with no free parameters gave an excellent account of the data. PMID:26598139
Object perception and masking: contributions of sides and convexities.
Poirier, Frédéric J A M; Wilson, Hugh R
2007-10-01
Object perception uses a variety of visual cues, including shape cues derived from sides and convexities. Two recent masking studies using radial frequency patterns have argued, respectively, for a predominant role of convexity [Habak, C., Wilkinson, F., Zakher, B., & Wilson, H. R. (2004). Curvature population coding for complex shapes in human vision. Vision Research, 44 (24), 2815-2823] or side information [Hess, R. F., Wang, Y. -Z., & Dakin, S. C. (1999). Are judgements of circularity local or global? Vision Research, 39, 4354-4360]. Here we resolve the controversy by separating the masks into their parts (e.g., convexities and sides), and measuring the relative masking influences of the different mask components. We found that both side and convexity information contribute to masking. However, masking due to side information was much less dependent on alignment compared to masking due to convexities. This supports a theory where convexities constitute a prime source of information for shape processing, and sides do also contribute but to a smaller extent. PMID:17889924
Shape recognition: convexities, concavities and things in between
Schmidtmann, Gunnar; Jennings, Ben J.; Kingdom, Frederick A. A.
2015-01-01
Visual objects are effortlessly recognized from their outlines, largely irrespective of viewpoint. Previous studies have drawn different conclusions regarding the importance to shape recognition of specific shape features such as convexities and concavities. However, most studies employed familiar objects, or shapes without curves, and did not measure shape recognition across changes in scale and position. We present a novel set of random shapes with well-defined convexities, concavities and inflections (intermediate points), segmented to isolate each feature type. Observers matched the segmented reference shapes to one of two subsequently presented whole-contour shapes (target or distractor) that were re-scaled and re-positioned. For very short segment lengths, performance was significantly higher for convexities than for concavities or intermediate points and for convexities remained constant with increasing segment length. For concavities and intermediate points, performance improved with increasing segment length, reaching convexity performance only for long segments. No significant differences between concavities and intermediates were found. These results show for the first time that closed curvilinear shapes are encoded using the positions of convexities, rather than concavities or intermediate regions. A shape-template model with no free parameters gave an excellent account of the data. PMID:26598139
Face pain may be dull and throbbing or an intense, stabbing discomfort in the face or forehead. It can occur in one or ... Pain that starts in the face may be caused by a nerve problem, injury, or infection. Face pain may also begin in other places in the body. ...
Weaver, M L; Qiu, S R; Hoyer, J R; Casey, W H; Nancollas, G H; De Yoreo, J J
2008-05-28
The growth of calcium oxalate monohydrate in the presence of Tamm-Horsfall protein (THP), osteopontin (OPN), and the 27-residue synthetic peptides (DDDS){sub 6}DDD and (DDDG){sub 6}DDD [where D = aspartic acid and X = S (serine) or G (glycine)] was investigated via in situ atomic force microscopy (AFM). The results show that these three growth modulators create extensive deposits on the crystal faces. Depending on the modulator and crystal face, these deposits can occur as discrete aggregates, filamentary structures, or uniform coatings. These proteinaceous films can lead to either the inhibition or increase of the step speeds (with respect to the impurity-free system) depending on a range of factors that include peptide or protein concentration, supersaturation and ionic strength. While THP and the linear peptides act, respectively, to exclusively increase and inhibit growth on the (-101) face, both exhibit dual functionality on the (010) face, inhibiting growth at low supersaturation or high modulator concentration and accelerating growth at high supersaturation or low modulator concentration. Based on analyses of growth morphologies and dependencies of step speeds on supersaturation and protein or peptide concentration, we argue for a picture of growth modulation that accounts for the observations in terms of the strength of binding to the surfaces and steps and the interplay of electrostatic and solvent-induced forces at crystal surface.
Vergence and facing patterns in large-scale sheath folds
NASA Astrophysics Data System (ADS)
Alsop, G. I.; Holdsworth, R. E.
1999-10-01
The careful geometric analysis of minor structural detail elucidates the relationships and evolution of associated large-scale curvilinear hinge geometries, developed during WNW-directed Caledonian thrusting exposed in Neoproterozoic Moine psammites of the Moine Nappe. Reversals in the polarity of structural facing associated with minor folding, mark the position of major sheath folds which parallel transport. Upwardly convex sheaths (closing in the direction of thrust transport) cored by older gneissose basement inliers are termed culminations, whilst those opening in the transport direction (and cored by Moine psammites) are termed depressions. Sheath folds are bisected by transport parallel and foliation normal (culmination/depression) surfaces which separate not only the reversals in facing, but also delineate zones of minor fold hinge obliquity into clockwise and anticlockwise domains relative to the transport direction. The sense of obliquity of minor Z and S folds is thus dependent on position with respect to the surfaces of culmination and depression and not the fold axial surfaces. Surfaces of culmination and depression may be superimposed on original overturned antiformal and synformal folds to produce a variety of dome (culmination on antiform), saddle (depression on antiform), inverted saddle (culmination on synform) and basin (depression on synform) configurations. The curvilinear hinges of minor folds may also be asymmetrical about the transport direction and within the plane of the regional foliation to define patterns of fold hinge-line vergence. Classical concepts of fold limb vergence may thus relate to larger antiformal and synformal hinges, whilst the fold hinge-line vergence defines major curvilinear hinges associated with culminations and depressions. Major sheath folds may therefore be interpreted in terms of both minor fold hinge-line and limb vergence, coupled with fold axis obliquity and reversals in the polarity of structural facing. The
The Knaster-Kuratowski-Mazurkiewicz theorem and abstract convexities
NASA Astrophysics Data System (ADS)
Cain, George L., Jr.; González, Luis
2008-02-01
The Knaster-Kuratowski-Mazurkiewicz covering theorem (KKM), is the basic ingredient in the proofs of many so-called "intersection" theorems and related fixed point theorems (including the famous Brouwer fixed point theorem). The KKM theorem was extended from Rn to Hausdorff linear spaces by Ky Fan. There has subsequently been a plethora of attempts at extending the KKM type results to arbitrary topological spaces. Virtually all these involve the introduction of some sort of abstract convexity structure for a topological space, among others we could mention H-spaces and G-spaces. We have introduced a new abstract convexity structure that generalizes the concept of a metric space with a convex structure, introduced by E. Michael in [E. Michael, Convex structures and continuous selections, Canad. J. MathE 11 (1959) 556-575] and called a topological space endowed with this structure an M-space. In an article by Shie Park and Hoonjoo Kim [S. Park, H. Kim, Coincidence theorems for admissible multifunctions on generalized convex spaces, J. Math. Anal. Appl. 197 (1996) 173-187], the concepts of G-spaces and metric spaces with Michael's convex structure, were mentioned together but no kind of relationship was shown. In this article, we prove that G-spaces and M-spaces are close related. We also introduce here the concept of an L-space, which is inspired in the MC-spaces of J.V. Llinares [J.V. Llinares, Unified treatment of the problem of existence of maximal elements in binary relations: A characterization, J. Math. Econom. 29 (1998) 285-302], and establish relationships between the convexities of these spaces with the spaces previously mentioned.
NASA Technical Reports Server (NTRS)
Gratz, Andrew J.; Bird, Peter; Quiro, Glenn B.
1990-01-01
A highly accurate method, called the negative crystal method, for determining the rate of dissolution on specific crystallographic faces of crystals was developed, in which the dissolution rates of nominally perfect crystal faces are obtained by measuring the size of individual negative crystals during a sequence of dissolution steps. The method was applied to determine the apparent activation energy and rate constants for the dissolution of quartz in 0.01 M KOH solutions at temperatures from 106 to 236 C. Also investigated were the effects of hydroxyl activity and ionic strength. The apparent activation energies for the dissolution of the prism and of the rhomb were determined.
Direct single-layered fabrication of 3D concavo convex patterns in nano-stereolithography
NASA Astrophysics Data System (ADS)
Lim, T. W.; Park, S. H.; Yang, D. Y.; Kong, H. J.; Lee, K. S.
2006-09-01
A nano-surfacing process (NSP) is proposed to directly fabricate three-dimensional (3D) concavo convex-shaped microstructures such as micro-lens arrays using two-photon polymerization (TPP), a promising technique for fabricating arbitrary 3D highly functional micro-devices. In TPP, commonly utilized methods for fabricating complex 3D microstructures to date are based on a layer-by-layer accumulating technique employing two-dimensional sliced data derived from 3D computer-aided design data. As such, this approach requires much time and effort for precise fabrication. In this work, a novel single-layer exposure method is proposed in order to improve the fabricating efficiency for 3D concavo convex-shaped microstructures. In the NSP, 3D microstructures are divided into 13 sub-regions horizontally with consideration of the heights. Those sub-regions are then expressed as 13 characteristic colors, after which a multi-voxel matrix (MVM) is composed with the characteristic colors. Voxels with various heights and diameters are generated to construct 3D structures using a MVM scanning method. Some 3D concavo convex-shaped microstructures were fabricated to estimate the usefulness of the NSP, and the results show that it readily enables the fabrication of single-layered 3D microstructures.
NASA Astrophysics Data System (ADS)
Ivey, Christopher B.; Moin, Parviz
2015-11-01
This paper presents a framework for extending the height-function technique for the calculation of interface normals and curvatures to unstructured non-convex polyhedral meshes with application to the piecewise-linear interface calculation volume-of-fluid method. The methodology is developed with reference to a collocated node-based finite-volume two-phase flow solver that utilizes the median-dual mesh, requiring a set of data structures and algorithms for non-convex polyhedral operations: truncation of a polyhedron by a plane, intersection of two polyhedra, joining of two convex polyhedra, volume enforcement of a polyhedron by a plane, and volume fraction initialization by a signed-distance function. By leveraging these geometric tools, a geometric interpolation strategy for embedding structured height-function stencils in unstructured meshes is developed. The embedded height-function technique is tested on surfaces with known interface normals and curvatures, namely cylinder, sphere, and ellipsoid. Tests are performed on the median duals of a uniform cartesian mesh, a wedge mesh, and a tetrahedral mesh, and comparisons are made with conventional methods. Across the tests, the embedded height-function technique outperforms contemporary methods and its accuracy approaches the accuracy that the traditional height-function technique exemplifies on uniform cartesian meshes.
Convexity Bias and Perspective Cues in the Reverse-Perspective Illusion.
Dobias, Joshua J; Papathomas, Thomas V; Vlajnic, Vanja M
2016-01-01
The present experiment was designed to examine the roles of painted linear perspective cues, and the convexity bias that are known to influence human observers' perception of three-dimensional (3D) objects and scenes. Reverse-perspective stimuli were used to elicit a depth-inversion illusion, in which far points on the stimulus appear to be closer than near points and vice versa, with a 2 (Type of stimulus) × 2 (Fixation mark position) design. To study perspective, two types of stimuli were used: a version with painted linear perspective cues and a version with blank (unpainted) surfaces. To examine the role of convexity, two locations were used for the fixation mark: either in a locally convex or a locally concave part of each stimulus (painted and unpainted versions). Results indicated that the reverse-perspective illusion was stronger when the stimulus contained strong perspective cues and when observers fixated a locally concave region within the scene. PMID:27482372
Convexity Bias and Perspective Cues in the Reverse-Perspective Illusion
Papathomas, Thomas V.; Vlajnic, Vanja M.
2016-01-01
The present experiment was designed to examine the roles of painted linear perspective cues, and the convexity bias that are known to influence human observers’ perception of three-dimensional (3D) objects and scenes. Reverse-perspective stimuli were used to elicit a depth-inversion illusion, in which far points on the stimulus appear to be closer than near points and vice versa, with a 2 (Type of stimulus) × 2 (Fixation mark position) design. To study perspective, two types of stimuli were used: a version with painted linear perspective cues and a version with blank (unpainted) surfaces. To examine the role of convexity, two locations were used for the fixation mark: either in a locally convex or a locally concave part of each stimulus (painted and unpainted versions). Results indicated that the reverse-perspective illusion was stronger when the stimulus contained strong perspective cues and when observers fixated a locally concave region within the scene. PMID:27482372
Anderson, I A; Carman, J B
2000-03-01
Models of regular cellular-solids representing femoral head 'medial group' bone were used to (1) compare thickness data for plate-like and beam-like structures at realistic surface areas and densities; (2) test the validity of a standard formula for trabecular thickness (Tb.Th); and (3) study how systematic changes in cancellous bone thicknesses, spacing, and face-connectivity affect relative density and surface area. Models of different face-connectivities, produced by plate removal from the unit cell, were fitted to bone density and surface area data. The medial group bone was anisotropic: the supero-inferior (SI) direction was the principal direction for bone plate alignment and the plane normal to this had the largest number of bone/void intersections per unit line length (P(I)). A comparison of boundary perimeter per unit area data, in planes normal to SI, with surface area data placed the medial group bone between prismatic structures in which walls are parallel to one principal direction and isotropic structures. Selective removal of plates from a closed-cell model produced a similar result. For the same relative density and surface-area, plate-like models had significantly thinner cross-sections than beam-like models. The formula for Tb.Th produced overestimates of model plate thickness by up to 20% at realistic femoral cancellous densities. Trends in data on surface area to volume ratio and density observed on sampled medial group bone could be simulated by plate thickness changes on models of intermediate face-connectivity (approximately 1.5) or by plate removal from models with relatively thick and short (low aspect-ratio) plates. The latter mechanism is unrealistic for it resulted in beam-like structures at low 'medial group' densities, an architecture unlike the predominantly plate-like bone in the sample. PMID:10673116
NASA Astrophysics Data System (ADS)
Su, C. W.; Huang, M. S.; Tsai, T. H.; Chang, S. C.
2012-12-01
Is crystalline ZnO(0 0 0 1¯) O-face surface believed to be enriched by Zn atoms? This study may get the answer. We proposed a simplified model to simulate surface concentration ratio on (0 0 0 1¯)-O or (0 0 0 1)-Zn surface based on the hard-sphere model. The simulation ratio was performed by integrating electron signals from the assumed Auger emission, in which the electron mean free path and relative atomic layer arrangements inside the different polarity ZnO crystal surface were considered as relevant parameters. After counting more than 100 experimental observations of Zn/O ratios, the high frequency peak ratio was found at around 0.428, which was near the value predicted by the proposed model using the IMFP database. The ratio larger than the peak value corresponds to that observed in the annealed samples. A downward trend of the ratio evaluated on the post-sputtering sample indicates the possibility of a Zn-enriched phase appearing on the annealed O-face surface. This phenomenon can further elucidate the O-deficiency debate on most ZnO materials.
ERIC Educational Resources Information Center
Weiner, Jill
2005-01-01
In this article, the author discusses "Game Face: Life Lessons Across the Curriculum", a teaching kit that challenges assumptions and builds confidence. Game Face, which is derived from a book and art exhibition, "Game Face: What Does a Female Athlete Look Like?", uses layered and powerful images of women and girls participating in sports to teach…
Diffractive analysis of circular computer-generated hologram for convex aspheric test
NASA Astrophysics Data System (ADS)
Liu, Hua
2015-11-01
Convex aspheric surface is tested by a circular amplitude computer-generated hologram (CGH) fabricated with our equipment and techniques, and much research work has been done simultaneously. However, the analysis of the detailed characters of the CGH used in the test system has not been systematically given in detail, including the correct phase, amplitude, and filter condition of the CGH. The calculation equation of the proper duty circle and the phase of the CGH are deduced, the frequency filter condition of the different diffracted orders of the CGH is demonstrated, and the deduction results are validated by the related experiment. The conclusion can help us to determine the radius ratio of the uncontrolled area over the full aperture of the aspheric surface during the process of optical system design, and it also points out that the radius ratio can be reduced by adjusting the radius of curvature of the reference surface and the distance between the reference surface and the convex aspheric surface. The work can assist us in designing the test system efficiently and correctly with CGH.
Design of quasi-phasematching gratings via convex optimization.
Phillips, C R; Gallmann, L; Fejer, M M
2013-04-22
We propose a new approach to quasi-phasematching (QPM) design based on convex optimization. We show that with this approach, globally optimum solutions to several important QPM design problems can be determined. The optimization framework is highly versatile, enabling the user to trade-off different objectives and constraints according to the particular application. The convex problems presented consist of simple objective and constraint functions involving a few thousand variables, and can therefore be solved quite straightforwardly. We consider three examples: (1) synthesis of a target pulse profile via difference frequency generation (DFG) from two ultrashort input pulses, (2) the design of a custom DFG transfer function, and (3) a new approach enabling the suppression of spectral gain narrowing in chirped-QPM-based optical parametric chirped pulse amplification (OPCPA). These examples illustrate the power and versatility of convex optimization in the context of QPM devices. PMID:23609719
Worst case estimation of homology design by convex analysis
NASA Technical Reports Server (NTRS)
Yoshikawa, N.; Elishakoff, Isaac; Nakagiri, S.
1998-01-01
The methodology of homology design is investigated for optimum design of advanced structures. for which the achievement of delicate tasks by the aid of active control system is demanded. The proposed formulation of homology design, based on the finite element sensitivity analysis, necessarily requires the specification of external loadings. The formulation to evaluate the worst case for homology design caused by uncertain fluctuation of loadings is presented by means of the convex model of uncertainty, in which uncertainty variables are assigned to discretized nodal forces and are confined within a conceivable convex hull given as a hyperellipse. The worst case of the distortion from objective homologous deformation is estimated by the Lagrange multiplier method searching the point to maximize the error index on the boundary of the convex hull. The validity of the proposed method is demonstrated in a numerical example using the eleven-bar truss structure.
Non-deterministic fatigue life analysis using convex set models
NASA Astrophysics Data System (ADS)
Sun, WenCai; Yang, ZiChun; Li, KunFeng
2013-04-01
The non-probabilistic approach to fatigue life analysis was studied using the convex models—interval, ellipsoidal and multi-convex models. The lower and upper bounds of the fatigue life were obtained by using the second-order Taylor series and Lagrange multiplier method. The solving process for derivatives of the implicit life function was presented. Moreover, a median ellipsoidal model was proposed which can take into account the sample blind zone and almost impossibility of concurrence of some small probability events. The Monte Carlo method for multi-convex model was presented, an important alternative when the analytical method does not work. A project example was given. The feasibility and rationality of the presented approach were verified. It is also revealed that the proposed method is conservative compared to the traditional probabilistic method, but it is a useful complement when it is difficult to obtain the accurate probability densities of parameters.
Entanglement Quantification Made Easy: Polynomial Measures Invariant under Convex Decomposition
NASA Astrophysics Data System (ADS)
Regula, Bartosz; Adesso, Gerardo
2016-02-01
Quantifying entanglement in composite systems is a fundamental challenge, yet exact results are available in only a few special cases. This is because hard optimization problems are routinely involved, such as finding the convex decomposition of a mixed state with the minimal average pure-state entanglement, the so-called convex roof. We show that under certain conditions such a problem becomes trivial. Precisely, we prove by a geometric argument that polynomial entanglement measures of degree 2 are independent of the choice of pure-state decomposition of a mixed state, when the latter has only one pure unentangled state in its range. This allows for the analytical evaluation of convex roof extended entanglement measures in classes of rank-2 states obeying such a condition. We give explicit examples for the square root of the three-tangle in three-qubit states, and we show that several representative classes of four-qubit pure states have marginals that enjoy this property.
NASA Astrophysics Data System (ADS)
Skala, Vaclav
2016-06-01
There are many space subdivision and space partitioning techniques used in many algorithms to speed up computations. They mostly rely on orthogonal space subdivision, resp. using hierarchical data structures, e.g. BSP trees, quadtrees, octrees, kd-trees, bounding volume hierarchies etc. However in some applications a non-orthogonal space subdivision can offer new ways for actual speed up. In the case of convex polygon in E2 a simple Point-in-Polygon test is of the O(N) complexity and the optimal algorithm is of O(log N) computational complexity. In the E3 case, the complexity is O(N) even for the convex polyhedron as no ordering is defined. New Point-in-Convex Polygon and Point-in-Convex Polyhedron algorithms are presented based on space subdivision in the preprocessing stage resulting to O(1) run-time complexity. The presented approach is simple to implement. Due to the principle of duality, dual problems, e.g. line-convex polygon, line clipping, can be solved in a similarly.
Interpolation Error Estimates for Mean Value Coordinates over Convex Polygons.
Rand, Alexander; Gillette, Andrew; Bajaj, Chandrajit
2013-08-01
In a similar fashion to estimates shown for Harmonic, Wachspress, and Sibson coordinates in [Gillette et al., AiCM, to appear], we prove interpolation error estimates for the mean value coordinates on convex polygons suitable for standard finite element analysis. Our analysis is based on providing a uniform bound on the gradient of the mean value functions for all convex polygons of diameter one satisfying certain simple geometric restrictions. This work makes rigorous an observed practical advantage of the mean value coordinates: unlike Wachspress coordinates, the gradient of the mean value coordinates does not become large as interior angles of the polygon approach π. PMID:24027379
Interpolation Error Estimates for Mean Value Coordinates over Convex Polygons
Rand, Alexander; Gillette, Andrew; Bajaj, Chandrajit
2012-01-01
In a similar fashion to estimates shown for Harmonic, Wachspress, and Sibson coordinates in [Gillette et al., AiCM, to appear], we prove interpolation error estimates for the mean value coordinates on convex polygons suitable for standard finite element analysis. Our analysis is based on providing a uniform bound on the gradient of the mean value functions for all convex polygons of diameter one satisfying certain simple geometric restrictions. This work makes rigorous an observed practical advantage of the mean value coordinates: unlike Wachspress coordinates, the gradient of the mean value coordinates does not become large as interior angles of the polygon approach π. PMID:24027379
Laser micromilling of convex microfluidic channels onto glassy carbon for glass molding dies
NASA Astrophysics Data System (ADS)
Tseng, Shih-Feng; Chen, Ming-Fei; Hsiao, Wen-Tse; Huang, Chien-Yao; Yang, Chung-Heng; Chen, Yu-Sheng
2014-06-01
This study reports the fabrication of convex microfluidic channels on glassy carbon using an ultraviolet laser processing system to produce glass molding dies. The laser processing parameters, including various laser fluences and scanning speeds of galvanometers, were adjusted to mill a convex microchannel on a glassy carbon substrate to identify the effects of material removal. The machined glassy carbon substrate was then applied as a glass molding die to fabricate a glass-based microfluidic biochip. The surface morphology, milled width and depth, and surface roughness of the microchannel die after laser micromilling were examined using a three-dimensional confocal laser scanning microscope. This study also investigates the transcription rate of microchannels after the glass molding process. To produce a 180 μm high microchannel on the GC substrate, the optimal number of milled cycles, laser fluence, and scanning speed were 25, 4.9 J/cm2, and 200 mm/s, respectively. The width, height, and surface roughness of milled convex microchannels were 119.6±0.217 μm, 180.26±0.01 μm, and 0.672±0.08 μm, respectively. These measured values were close to the predicted values and suitable for a glass molding die. After the glass molding process, a typical glass-based microchannel chip was formed at a molding temperature of 660 °C and the molding force of 0.45 kN. The transcription rates of the microchannel width and depth were 100% and 99.6%, respectively. Thus, the proposed approach is suitable for performing in chemical, biochemical, or medical reactions.
NASA Technical Reports Server (NTRS)
Kantsios, A. G.; Henley, W. C., Jr.; Snow, W. L.
1982-01-01
The use of a photographic pyrometer for nonintrusive measurement of high temperature surfaces in a wind tunnel test is described. The advantages of the pyrometer for measuring surfaces whose unique shape makes use of thermocouples difficult are pointed out. The use of computer operated densitometers or optical processors for the data reduction is recommended.
NASA Astrophysics Data System (ADS)
Chen, Jian; Deng, Xin; Gong, Manfeng; Liu, Wei; Wu, Shanghua
2016-09-01
This paper systematically investigated a set of functionally graded WC-TiC-Mo-Co cemented carbides with modified surface layer (called fcc-rich surface layer in this study), which is mainly composed of fcc phases (Ti(CN) and TiN) and WC. Nitridation at liquid phase sintering temperature is the key process making this fcc-rich surface layer. The functionally graded WC-TiC-Mo-Co cemented carbides synthesized in this study show 3 layer structure: the outer layer, i.e. the fcc-rich surface layer; the intermediate layer, which is characterized by abnormally large WC and high Co content; and the inner layer. It was found that TiC is the most critical component for the formation of fcc-rich surface layer. The higher content of TiC results in the thicker fcc-rich outer layer, higher (Ti(CN) and TiN) content in the outer layer, and higher hardness of the fcc-rich outer layer. The formation of this fcc-rich surface layer is mainly due to the nitridation process between Ti and N, which leads to the diffusion of Ti outwards (from the inside of the sample to the surface) and the subsequent migration of liquid cobalt inwards (from surface to the inside of the sample). The three-layer structure developed in this study provides the excellent combination of high wear resistance and high toughness, which is favorable for some applications.
Preconditioning 2D Integer Data for Fast Convex Hull Computations.
Cadenas, José Oswaldo; Megson, Graham M; Luengo Hendriks, Cris L
2016-01-01
In order to accelerate computing the convex hull on a set of n points, a heuristic procedure is often applied to reduce the number of points to a set of s points, s ≤ n, which also contains the same hull. We present an algorithm to precondition 2D data with integer coordinates bounded by a box of size p × q before building a 2D convex hull, with three distinct advantages. First, we prove that under the condition min(p, q) ≤ n the algorithm executes in time within O(n); second, no explicit sorting of data is required; and third, the reduced set of s points forms a simple polygonal chain and thus can be directly pipelined into an O(n) time convex hull algorithm. This paper empirically evaluates and quantifies the speed up gained by preconditioning a set of points by a method based on the proposed algorithm before using common convex hull algorithms to build the final hull. A speedup factor of at least four is consistently found from experiments on various datasets when the condition min(p, q) ≤ n holds; the smaller the ratio min(p, q)/n is in the dataset, the greater the speedup factor achieved. PMID:26938221
Systematization of problems on ball estimates of a convex compactum
NASA Astrophysics Data System (ADS)
Dudov, S. I.
2015-09-01
We consider a class of finite-dimensional problems on the estimation of a convex compactum by a ball of an arbitrary norm in the form of extremal problems whose goal function is expressed via the function of the distance to the farthest point of the compactum and the function of the distance to the nearest point of the compactum or its complement. Special attention is devoted to the problem of estimating (approximating) a convex compactum by a ball of fixed radius in the Hausdorff metric. It is proved that this problem plays the role of the canonical problem: solutions of any problem in the class under consideration can be expressed via solutions of this problem for certain values of the radius. Based on studying and using the properties of solutions of this canonical problem, we obtain ranges of values of the radius in which the canonical problem expresses solutions of the problems on inscribed and circumscribed balls, the problem of uniform estimate by a ball in the Hausdorff metric, the problem of asphericity of a convex body, the problems of spherical shells of the least thickness and of the least volume for the boundary of a convex body. This makes it possible to arrange the problems in increasing order of the corresponding values of the radius. Bibliography: 34 titles.
NONPARAMETRIC ESTIMATION OF MULTIVARIATE CONVEX-TRANSFORMED DENSITIES
Seregin, Arseni; Wellner, Jon A.
2011-01-01
We study estimation of multivariate densities p of the form p(x) = h(g(x)) for x ∈ ℝd and for a fixed monotone function h and an unknown convex function g. The canonical example is h(y) = e−y for y ∈ ℝ; in this case, the resulting class of densities P(e−y)={p=exp(−g):gis convex}is well known as the class of log-concave densities. Other functions h allow for classes of densities with heavier tails than the log-concave class. We first investigate when the maximum likelihood estimator p̂ exists for the class P(h) for various choices of monotone transformations h, including decreasing and increasing functions h. The resulting models for increasing transformations h extend the classes of log-convex densities studied previously in the econometrics literature, corresponding to h(y) = exp(y). We then establish consistency of the maximum likelihood estimator for fairly general functions h, including the log-concave class P(e−y) and many others. In a final section, we provide asymptotic minimax lower bounds for the estimation of p and its vector of derivatives at a fixed point x0 under natural smoothness hypotheses on h and g. The proofs rely heavily on results from convex analysis. PMID:21423877
Preconditioning 2D Integer Data for Fast Convex Hull Computations
2016-01-01
In order to accelerate computing the convex hull on a set of n points, a heuristic procedure is often applied to reduce the number of points to a set of s points, s ≤ n, which also contains the same hull. We present an algorithm to precondition 2D data with integer coordinates bounded by a box of size p × q before building a 2D convex hull, with three distinct advantages. First, we prove that under the condition min(p, q) ≤ n the algorithm executes in time within O(n); second, no explicit sorting of data is required; and third, the reduced set of s points forms a simple polygonal chain and thus can be directly pipelined into an O(n) time convex hull algorithm. This paper empirically evaluates and quantifies the speed up gained by preconditioning a set of points by a method based on the proposed algorithm before using common convex hull algorithms to build the final hull. A speedup factor of at least four is consistently found from experiments on various datasets when the condition min(p, q) ≤ n holds; the smaller the ratio min(p, q)/n is in the dataset, the greater the speedup factor achieved. PMID:26938221
Parametric R-norm directed-divergence convex function
NASA Astrophysics Data System (ADS)
Garg, Dhanesh; Kumar, Satish
2016-06-01
In this paper, we define parametric R-norm directed-divergence convex function and discuss their special cases and prove some properties similar to Kullback-Leibler information measure. From R-norm divergence measure new information measures have also been derived and their relations with different measures of entropy have been obtained and give its application in industrial engineering.
NASA Astrophysics Data System (ADS)
Aref'eva, L. P.; Shebzukhova, I. G.
2016-07-01
A technique for the evaluation of the electron work function of metallic single crystals and the electron work function anisotropy has been developed in the framework of the electron-statistical method. The surface energy and the electron work function have been calculated for crystal faces of allotropic modifications of 4 d- and 5 d-metals. A change in the electron work function due to the allotropic transformations has been estimated, and the periodic dependence of the electron work function has been determined. It has been shown that the results obtained using the proposed technique correlate with the available experimental data for polycrystals.
ERIC Educational Resources Information Center
Brooks, Diana
1995-01-01
Discusses the use of face painting as a technique for making the endangered species issue tangible for children while addressing the complexity of the issue. Children are "given" an animal of their own and are educated about the animal while having their faces painted to resemble the animal. (LZ)
NASA Technical Reports Server (NTRS)
Weddendorf, Bruce C. (Inventor)
1991-01-01
A double face sealing device for mounting between two surfaces to provide an airtight and fluid-tight seal between a closure member bearing one of the surfaces and a structure or housing bearing the other surface which extends around the opening or hatchway to be closed. The double face sealing device includes a plurality of sections or segments mounted to one of the surfaces, each having a main body portion, a pair of outwardly extending and diverging, cantilever, spring arms, and a pair of inwardly extending and diverging, cantilever, spring arms, an elastomeric cover on the distal, free, ends of the outwardly extending and diverging spring arms, and an elastomeric cover on the distal, free, ends of the inwardly extending and diverging spring arms. The double face sealing device has application or use in all environments requiring a seal, but is particularly useful to seal openings or hatchways between compartments of spacecraft or aircraft.
Bao, Luyao; Hu, Haibao; Wen, Jun; Sepri, Paavo; Luo, Kai
2016-01-01
A liquid in the vicinity of a solid-liquid interface (SLI) may exhibit complex structures. In this study, we used molecular dynamics simulations demonstrating for the first time that the liquid adjacent to the SLI can have a two-level structure in some cases: a major structure and a minor structure. Through a time-averaging process of molecular motions, we identified the type of the liquid structure by calculating positions of the maximum liquid density in three spatial dimensions, and these positions were found to distribute in many dispersed zones (called high-density zones (HDZs)). The major structure appears throughout the SLI, while the minor structure only occurs significantly within the third layer. Instead of the previously reported body-centered cubic (BCC) or face-centered-cubic (FCC) types, the major structure was found to show a body-centered tetragonal (BCT) type. The adjacent HDZs are connected by specific junctions, demonstrating that atoms diffuse along some particular high probability paths from one HDZ to another. By considering the three-dimensional liquid density distribution from the continuum point of view, more complete details of the structure and diffusive behavior of liquids in the SLI are also possible to be revealed. PMID:27430188
NASA Astrophysics Data System (ADS)
Bao, Luyao; Hu, Haibao; Wen, Jun; Sepri, Paavo; Luo, Kai
2016-07-01
A liquid in the vicinity of a solid-liquid interface (SLI) may exhibit complex structures. In this study, we used molecular dynamics simulations demonstrating for the first time that the liquid adjacent to the SLI can have a two-level structure in some cases: a major structure and a minor structure. Through a time-averaging process of molecular motions, we identified the type of the liquid structure by calculating positions of the maximum liquid density in three spatial dimensions, and these positions were found to distribute in many dispersed zones (called high-density zones (HDZs)). The major structure appears throughout the SLI, while the minor structure only occurs significantly within the third layer. Instead of the previously reported body-centered cubic (BCC) or face-centered-cubic (FCC) types, the major structure was found to show a body-centered tetragonal (BCT) type. The adjacent HDZs are connected by specific junctions, demonstrating that atoms diffuse along some particular high probability paths from one HDZ to another. By considering the three-dimensional liquid density distribution from the continuum point of view, more complete details of the structure and diffusive behavior of liquids in the SLI are also possible to be revealed.
Convex hull matching and hierarchical decomposition for multimodality medical image registration.
Yang, Jian; Fan, Jingfan; Fu, Tianyu; Ai, Danni; Zhu, Jianjun; Li, Qin; Wang, Yongtian
2015-01-01
This study proposes a novel hierarchical pyramid strategy for 3D registration of multimodality medical images. The surfaces of the source and target volume data are first extracted, and the surface point clouds are then aligned roughly using convex hull matching. The convex hull matching registration procedure could align images with large-scale transformations. The original images are divided into blocks and the corresponding blocks in the two images are registered by affine and non-rigid registration procedures. The sub-blocks are iteratively smoothed by the Gaussian kernel with different sizes during the registration procedure. The registration result of the large kernel is taken as the input of the small kernel registration. The fine registration of the two volume data sets is achieved by iteratively increasing the number of blocks, in which increase in similarity measure is taken as a criterion for acceptation of each iteration level. Results demonstrate the effectiveness and robustness of the proposed method in registering the multiple modalities of medical images. PMID:25882735
... gets worse when you bend forward) Tic douloureux Temporomandibular joint dysfunction syndrome Sometimes the reason for the face pain ... is persistent, unexplained, or accompanied by other unexplained symptoms. Call your primary provider. What to Expect at ...
On Rank One Convex Functions that are Homogeneous of Degree One
NASA Astrophysics Data System (ADS)
Kirchheim, Bernd; Kristensen, Jan
2016-07-01
We show that positively 1-homogeneous rank one convex functions are convex at 0 and at matrices of rank one. The result is a special case of an abstract convexity result that we establish for positively 1-homogeneous directionally convex functions defined on an open convex cone in a finite dimensional vector space. From these results we derive a number of consequences including various generalizations of the Ornstein L1 non inequalities. Most of the results were announced in ( C R Acad Sci Paris Ser I 349:407-409, 2011).
Recognition of Graphs with Convex Quadratic Stability Number
NASA Astrophysics Data System (ADS)
Pacheco, Maria F.; Cardoso, Domingos M.
2009-09-01
A stable set of a graph is a set of mutually non-adjacent vertices. The determination of a maximum size stable set, which is called maximum stable set, and the determination of its size, which is called stability number, are central combinatorial optimization problems. However, given a nonnegative integer k, to determine if a graph G has a stable set of size k is NP-complete. In this paper we deal with graphs for which the stability number can be determined by solving a convex quadratic programming problem. Such graphs were introduced in [13] and are called graphs with convex-QP stability number. A few algorithmic techniques for the recognition of this type of graphs in particular families are presented.
Delivering Sound Energy along an Arbitrary Convex Trajectory
Zhao, Sipei; Hu, Yuxiang; Lu, Jing; Qiu, Xiaojun; Cheng, Jianchun; Burnett, Ian
2014-01-01
Accelerating beams have attracted considerable research interest due to their peculiar properties and various applications. Although there have been numerous research on the generation and application of accelerating light beams, few results have been published on the generation of accelerating acoustic beams. Here we report on the experimental observation of accelerating acoustic beams along arbitrary convex trajectories. The desired trajectory is projected to the spatial phase profile on the boundary which is discretized and sampled spatially. The sound field distribution is formulated with the Green function and the integral equation method. Both the paraxial and the non-paraxial regimes are examined and observed in the experiments. The effect of obstacle scattering in the sound field is also investigated and the results demonstrate that the approach is robust against obstacle scattering. The realization of accelerating acoustic beams will have an impact on various applications where acoustic information and energy are required to be delivered along an arbitrary convex trajectory. PMID:25316353
Shock wave reflection over convex and concave wedge
NASA Astrophysics Data System (ADS)
Kitade, M.; Kosugi, T.; Yada, K.; Takayama, Kazuyoshi
2001-04-01
It is well known that the transition criterion nearly agrees with the detachment criterion in the case of strong shocks, two-dimensional, and pseudosteady flow. However, when the shock wave diffracts over a wedge whose angle is below the detachment criterion, that is, in the domain of Mach reflection, precursory regular reflection (PRR) appears near the leading edge and as the shock wave propagates, the PRR is swept away by the overtaking corner signal (cs) that forces the transition to Mach reflection. It is clear that viscosity and thermal conductivity influences transition and the triple point trajectory. On the other hand, the reflection over concave and convex wedges is truly unsteady flow, and the effect of viscosity and thermal conductivity on transition and triple point trajectory has not been reported. This paper describes that influence of viscosity over convex and concave corners investigated both experiments and numerical simulations.
A convex penalty for switching control of partial differential equations
Clason, Christian; Rund, Armin; Kunisch, Karl; Barnard, Richard C.
2016-01-19
A convex penalty for promoting switching controls for partial differential equations is introduced; such controls consist of an arbitrary number of components of which at most one should be simultaneously active. Using a Moreau–Yosida approximation, a family of approximating problems is obtained that is amenable to solution by a semismooth Newton method. In conclusion, the efficiency of this approach and the structure of the obtained controls are demonstrated by numerical examples.
Convexity properties of images under nonlinear integral operators
Kokurin, M Yu
2014-12-31
Conditions are obtained for the image of a given set under a general completely continuous nonlinear integral operator to have convex closure. These results are used to establish the uniqueness of quasi-solutions of nonlinear integral equations of the first kind and to prove the solvability of equations of the first kind on a dense subset of the right-hand sides. Bibliography: 11 titles.
Convex Clustering: An Attractive Alternative to Hierarchical Clustering
Chen, Gary K.; Chi, Eric C.; Ranola, John Michael O.; Lange, Kenneth
2015-01-01
The primary goal in cluster analysis is to discover natural groupings of objects. The field of cluster analysis is crowded with diverse methods that make special assumptions about data and address different scientific aims. Despite its shortcomings in accuracy, hierarchical clustering is the dominant clustering method in bioinformatics. Biologists find the trees constructed by hierarchical clustering visually appealing and in tune with their evolutionary perspective. Hierarchical clustering operates on multiple scales simultaneously. This is essential, for instance, in transcriptome data, where one may be interested in making qualitative inferences about how lower-order relationships like gene modules lead to higher-order relationships like pathways or biological processes. The recently developed method of convex clustering preserves the visual appeal of hierarchical clustering while ameliorating its propensity to make false inferences in the presence of outliers and noise. The solution paths generated by convex clustering reveal relationships between clusters that are hidden by static methods such as k-means clustering. The current paper derives and tests a novel proximal distance algorithm for minimizing the objective function of convex clustering. The algorithm separates parameters, accommodates missing data, and supports prior information on relationships. Our program CONVEXCLUSTER incorporating the algorithm is implemented on ATI and nVidia graphics processing units (GPUs) for maximal speed. Several biological examples illustrate the strengths of convex clustering and the ability of the proximal distance algorithm to handle high-dimensional problems. CONVEXCLUSTER can be freely downloaded from the UCLA Human Genetics web site at http://www.genetics.ucla.edu/software/ PMID:25965340
Stochastic Homogenization of Nonconvex Unbounded Integral Functionals with Convex Growth
NASA Astrophysics Data System (ADS)
Duerinckx, Mitia; Gloria, Antoine
2016-03-01
We consider the well-trodden ground of the problem of the homogenization of random integral functionals. When the integrand has standard growth conditions, the qualitative theory is well-understood. When it comes to unbounded functionals, that is, when the domain of the integrand is not the whole space and may depend on the space-variable, there is no satisfactory theory. In this contribution we develop a complete qualitative stochastic homogenization theory for nonconvex unbounded functionals with convex growth. We first prove that if the integrand is convex and has p-growth from below (with p > d, the dimension), then it admits homogenization regardless of growth conditions from above. This result, that crucially relies on the existence and sublinearity at infinity of correctors, is also new in the periodic case. In the case of nonconvex integrands, we prove that a similar homogenization result holds provided that the nonconvex integrand admits a two-sided estimate by a convex integrand (the domain of which may depend on the space variable) that itself admits homogenization. This result is of interest to the rigorous derivation of rubber elasticity from polymer physics, which involves the stochastic homogenization of such unbounded functionals.
Stochastic Homogenization of Nonconvex Unbounded Integral Functionals with Convex Growth
NASA Astrophysics Data System (ADS)
Duerinckx, Mitia; Gloria, Antoine
2016-09-01
We consider the well-trodden ground of the problem of the homogenization of random integral functionals. When the integrand has standard growth conditions, the qualitative theory is well-understood. When it comes to unbounded functionals, that is, when the domain of the integrand is not the whole space and may depend on the space-variable, there is no satisfactory theory. In this contribution we develop a complete qualitative stochastic homogenization theory for nonconvex unbounded functionals with convex growth. We first prove that if the integrand is convex and has p-growth from below (with p > d, the dimension), then it admits homogenization regardless of growth conditions from above. This result, that crucially relies on the existence and sublinearity at infinity of correctors, is also new in the periodic case. In the case of nonconvex integrands, we prove that a similar homogenization result holds provided that the nonconvex integrand admits a two-sided estimate by a convex integrand (the domain of which may depend on the space variable) that itself admits homogenization. This result is of interest to the rigorous derivation of rubber elasticity from polymer physics, which involves the stochastic homogenization of such unbounded functionals.
Constrained spacecraft reorientation using mixed integer convex programming
NASA Astrophysics Data System (ADS)
Tam, Margaret; Glenn Lightsey, E.
2016-10-01
A constrained attitude guidance (CAG) system is developed using convex optimization to autonomously achieve spacecraft pointing objectives while meeting the constraints imposed by on-board hardware. These constraints include bounds on the control input and slew rate, as well as pointing constraints imposed by the sensors. The pointing constraints consist of inclusion and exclusion cones that dictate permissible orientations of the spacecraft in order to keep objects in or out of the field of view of the sensors. The optimization scheme drives a body vector towards a target inertial vector along a trajectory that consists solely of permissible orientations in order to achieve the desired attitude for a given mission mode. The non-convex rotational kinematics are handled by discretization, which also ensures that the quaternion stays unity norm. In order to guarantee an admissible path, the pointing constraints are relaxed. Depending on how strict the pointing constraints are, the degree of relaxation is tuneable. The use of binary variables permits the inclusion of logical expressions in the pointing constraints in the case that a set of sensors has redundancies. The resulting mixed integer convex programming (MICP) formulation generates a steering law that can be easily integrated into an attitude determination and control (ADC) system. A sample simulation of the system is performed for the Bevo-2 satellite, including disturbance torques and actuator dynamics which are not modeled by the controller. Simulation results demonstrate the robustness of the system to disturbances while meeting the mission requirements with desirable performance characteristics.
Designing null phase screens to test a fast plano-convex aspheric lens
NASA Astrophysics Data System (ADS)
DelOlmo-Márquez, Jesús; Castán-Ricaño, Diana; Avendaño-Alejo, Maximino; Díaz-Uribe, Rufino
2015-08-01
We have obtained a formula to represent the wavefront produced by a plano-convex aspheric lens with symmetry of revolution considering a plane wavefront propagating parallel to the optical axis and impinging on the refracting surface, it is called a zero-distance phase front, being it the first wavefront to be out of the optical system. Using a concept of differential geometry called parallel curves it is possible to obtain an analytic formula to represent the wavefront propagated at arbitrary distances through the optical axis. In order to evaluate qualitatively a plano-convex aspheric lens, we have modified slightly an interferometer Tywman-Green as follow: In the reference beam we use a plane mirror and the beam of test we have used a spatial light modulator (SLM) to compensate the phase produced by the lens under test. It will be called a null phase interferometer. The main idea is to recombine both wavefronts in order to get a null interferogram, otherwise we will associate the patterns of the interferogram to deformations of the lens under test. The null phase screens are formed with concentric circumferences assuming different gray levels printed on SLM.
Creeping waves and resonances in transient scattering by smooth convex objects
NASA Astrophysics Data System (ADS)
Heyman, E.; Felsen, L. B.
1983-05-01
The surface currents induced by an impulsive line source of magnetic currents located on the surface of a perfectly conducting circular cylinder are determined. The transient field is Fourier transformed to reduce it to the time-harmonic domain. Alternative field representations, based on the method of characteristic Green's functions, are constructed directly and without intervention of the Watson transformation to yield expansions in terms of angular eigenfunctions, radial eigenfunctions, and resonant eigenfunctions. The various ways of dealing with the creeping waves in the time-harmonic and the transient regimes, and the connection between the creeping waves and the singularity expansion method (SEM) resonances are emphasized. The results are employed to develop alternative hybrid formulations by collective treatment of a group of creeping waves or of a group of SEM resonant solutions. The generalization to scattering by cylinderical objects with arbitrary convex curvature is given.
NASA Astrophysics Data System (ADS)
Samoylenko, V. V.; Lenivtseva, O. G.; Polyakov, I. A.; Laptev, I. S.; Martyushev, N. V.
2016-04-01
The influence of electron-beam facing modes on the structure of Ti-Ta layers formed on the surface of commercially pure titanium VT1-0 has been studied in the paper. The mode of the electron-beam treatment of alloying powder mixture, by which there were no defects in the pad, has been identified. The methods of optical microscopy and scanning electron microscopy have shown that in pads there is dendritic segregation typical for the process of initial crystallisation. At greater magnifications it is possible to observe a structure of the laminar type. The X-ray phase analysis of titanium-tantalum layers justifies the presence of two phases: a hexagonal α'-phase and a cubic (β-phase of titanium.
NASA Astrophysics Data System (ADS)
Earman, S.; Dettinger, M.
2007-12-01
Groundwater is a vital resource in the western USA, accounting for over a quarter of total supplies and irrigation uses. In addition, groundwater is a major contributor to surface-water resources, sustaining baseflows throughout the year, and contributes important fractions of streamflows even during high-flow periods following rainfall and snowmelt. Because mountains are generally cooler and wetter than adjacent basins, groundwater in the West is derived mostly from mountain precipitation. Large infiltrations of water are required to break through the region's thick unsaturated zones. Because snowpacks store and then release precipitation from several storms at once, snowmelt contributes disproportionately more recharge than does rain. Warming temperatures have already caused declines in Western snowpacks and earlier flows in melt-fed streams. Current projections of future climate suggest that these trends will continue. Snowline elevations are expected to rise, reducing snow-covered areas in western mountains, and decreasing the amount of snow in areas where snowpacks remain. If so, mountain-block recharge also may also decline, as recharge areas shrink and snow available for melt generation dwindles. Declines in mountain recharge triggered by loss of snowpack would have immediate impacts on mountain water resources, including low flows and stream temperatures, and may also have serious impacts on long-term ground-water supplies in surrounding basins. Although recharge that supplies mountain groundwater may decline, much of this unrecharged water may run off onto fans and basins, increasing recharge beyond the mountains. However, if the water that is not recharged in the mountains is mostly evapotranspired from the mountain soils, the overall recharge (mountain plus basin) may decline. Changes in temperature will bring concomitant changes in water temperatures, and thus in streambed conductance and leakance; changes in dominant vegetation may also occur. All
ERIC Educational Resources Information Center
Greene, Yvonne
2000-01-01
Presents a torn-paper and gadget-print activity for younger students, specifically pre-kindergarten to first grade, that can be done any time over the school year or at Halloween. Discusses how the students create their funny faces and lists the materials needed. (CMK)
Iida, Ryo; Kawamura, Hitoshi; Niikura, Kenichi; Kimura, Takashi; Sekiguchi, Shota; Joti, Yasumasa; Bessho, Yoshitaka; Mitomo, Hideyuki; Nishino, Yoshinori; Ijiro, Kuniharu
2015-04-14
This study aims at the synthesis of Janus gold nanoparticles (Janus GNPs) with hydrophilic/hydrophobic faces by a simple ligand exchange reaction in an homogeneous system and at the elucidation of the self-assembled structures of the Janus GNPs in water. As hydrophilic surface ligands, we synthesized hexaethylene glycol (E6)-terminated thiolate ligands with C3, C7, or C11 alkyl chains, referred to as E6C3, E6C7, and E6C11, respectively. As a hydrophobic ligand, a butyl-headed thiolate ligand C4-E6C11, in which a C4 alkyl was introduced on the E6C11 terminus, was synthesized. The degree of segregation between the two ligands on the GNPs (5 nm in diameter) was examined by matrix-assisted laser desorption/ionization time-of fright mass spectrometry (MALDI-TOF MS) analysis. We found that the choice of immobilization methods, one-step or two-step addition of the two ligands to the GNP solution, crucially affects the degree of segregation. The two-step addition of a hydrophilic ligand (E6C3) followed by a hydrophobic ligand (C4-E6C11) produced a large degree of segregation on the GNPs, providing Janus-like GNPs. When dispersed in water, these Janus-like GNPs formed assemblies of ∼160 nm in diameter, whereas Domain GNPs, in which the two ligands formed partial domains on the surface, were precipitated even when the molar ratio of the hydrophilic ligand and the hydrophobic ligand on the surface of the NPs was almost 1:1. The assembled structure of the Janus-like GNPs in water was directly observed by pulsed coherent X-ray solution scattering using an X-ray free-electron laser, revealing irregular spherical structures with uneven surfaces. PMID:25796963
Choi, Samuel; Watanabe, Tomoya; Suzuki, Takamasa; Nin, Fumiaki; Hibino, Hiroshi; Sasaki, Osami
2015-08-10
Microvibrations that occur in bio-tissues are considered to play pivotal roles in organ function; however techniques for their measurement have remained underdeveloped. To address this issue, in the present study we have developed a novel optical coherence tomography (OCT) method that utilizes multifrequency swept interferometry. The OCT volume data can be acquired by sweeping the multifrequency modes produced by combining a tunable Fabry-Perot filter and an 840 nm super-luminescent diode with a bandwidth of 160 nm. The system employing the wide-field heterodyne method does not require mechanical scanning probes, which are usually incorporated in conventional Doppler OCTs and heterodyne-type interferometers. These arrangements allow obtaining not only 3D tomographic images but also various vibration parameters such as spatial amplitude, phase, and frequency, with high temporal and transverse resolutions over a wide field. Indeed, our OCT achieved the axial resolution of ~2.5 μm when scanning the surface of a glass plate. Moreover, when examining a mechanically resonant multilayered bio-tissue in full-field configuration, we captured 22 nm vibrations of its internal surfaces at 1 kHz by reconstructing temporal phase variations. This so-called "multifrequency swept common-path en-face OCT" can be applied for measuring microdynamics of a variety of biological samples, thus contributing to the progress in life sciences research. PMID:26367958
NASA Astrophysics Data System (ADS)
Lyu, Ming; Méndez, Mariano; Altamirano, Diego; Zhang, Guobao
2016-08-01
We investigated the convexity of all type I X-ray bursts with millihertz quasi-periodic oscillations (mHz QPOs) in 4U 1636-53 using archival observations with the Rossi X-ray Timing Explorer. We found that, at a 3.5σ confidence level, in all 39 cases in which the mHz QPOs disappeared at the time of an X-ray burst, the convexity of the burst is positive. The convexity measures the shape of the rising part of the burst light curve and, according to recent models, it is related to the ignition site of bursts on the neutron-star surface. This finding suggests that in 4U 1636-53 these 39 bursts and the marginally-stable nuclear burning process responsible for the mHz QPOs take place at the neutron-star equator. This scenario could explain the inconsistency between the high accretion rate required for triggering mHz QPOs in theoretical models and the relatively low accretion rate derived from observations.
Confined buckling of inextensible rods by convex difference algorithms
NASA Astrophysics Data System (ADS)
Alart, Pierre; Pagano, Stéphane
2002-12-01
In this Note we present an approach to determine the local minima of a specific class of minimization problems. Attention is focused on the inextensibility condition of flexible rods expressed as a nonconvex constraint. Two algorithms are derived from a special splitting of the Lagrangian into the difference of two convex functions (DC). They are compared to the augmented Lagrangian methods used in this context. These DC formulations are easily extended to contact problems and applied to the determination of confined buckling shapes. To cite this article: P. Alart, S. Pagano, C. R. Mecanique 330 (2002) 819-824.
Computation of nonparametric convex hazard estimators via profile methods
Jankowski, Hanna K.; Wellner, Jon A.
2010-01-01
This paper proposes a profile likelihood algorithm to compute the nonparametric maximum likelihood estimator of a convex hazard function. The maximisation is performed in two steps: First the support reduction algorithm is used to maximise the likelihood over all hazard functions with a given point of minimum (or antimode). Then it is shown that the profile (or partially maximised) likelihood is quasi-concave as a function of the antimode, so that a bisection algorithm can be applied to find the maximum of the profile likelihood, and hence also the global maximum. The new algorithm is illustrated using both artificial and real data, including lifetime data for Canadian males and females. PMID:20300560
On the structure of self-affine convex bodies
Voynov, A S
2013-08-31
We study the structure of convex bodies in R{sup d} that can be represented as a union of their affine images with no common interior points. Such bodies are called self-affine. Vallet's conjecture on the structure of self-affine bodies was proved for d = 2 by Richter in 2011. In the present paper we disprove the conjecture for all d≥3 and derive a detailed description of self-affine bodies in R{sup 3}. Also we consider the relation between properties of self-affine bodies and functional equations with a contraction of an argument. Bibliography: 10 titles.
Use of Convex supercomputers for flight simulation at NASA Langley
NASA Technical Reports Server (NTRS)
Cleveland, Jeff I., II
1992-01-01
The use of the Convex Computer Corporation supercomputers for flight simulation is discussed focusing on a real-time input/output system for supporting the flight simulation. The flight simulation computing system is based on two single processor control data corporation CYBER 175 computers, coupled through extended memory. The Advanced Real-Time Simulation System for digital data distribution and signal conversion is a state-of-the-art, high-speed fiber-optic-based, ring network system which is based on the computer automated measurement and control technology.
Off-Grid DOA Estimation Based on Analysis of the Convexity of Maximum Likelihood Function
NASA Astrophysics Data System (ADS)
LIU, Liang; WEI, Ping; LIAO, Hong Shu
Spatial compressive sensing (SCS) has recently been applied to direction-of-arrival (DOA) estimation owing to advantages over conventional ones. However the performance of compressive sensing (CS)-based estimation methods decreases when true DOAs are not exactly on the discretized sampling grid. We solve the off-grid DOA estimation problem using the deterministic maximum likelihood (DML) estimation method. In this work, we analyze the convexity of the DML function in the vicinity of the global solution. Especially under the condition of large array, we search for an approximately convex range around the ture DOAs to guarantee the DML function convex. Based on the convexity of the DML function, we propose a computationally efficient algorithm framework for off-grid DOA estimation. Numerical experiments show that the rough convex range accords well with the exact convex range of the DML function with large array and demonstrate the superior performance of the proposed methods in terms of accuracy, robustness and speed.
Multiband RF pulses with improved performance via convex optimization
NASA Astrophysics Data System (ADS)
Shang, Hong; Larson, Peder E. Z.; Kerr, Adam; Reed, Galen; Sukumar, Subramaniam; Elkhaled, Adam; Gordon, Jeremy W.; Ohliger, Michael A.; Pauly, John M.; Lustig, Michael; Vigneron, Daniel B.
2016-01-01
Selective RF pulses are commonly designed with the desired profile as a low pass filter frequency response. However, for many MRI and NMR applications, the spectrum is sparse with signals existing at a few discrete resonant frequencies. By specifying a multiband profile and releasing the constraint on "don't-care" regions, the RF pulse performance can be improved to enable a shorter duration, sharper transition, or lower peak B1 amplitude. In this project, a framework for designing multiband RF pulses with improved performance was developed based on the Shinnar-Le Roux (SLR) algorithm and convex optimization. It can create several types of RF pulses with multiband magnitude profiles, arbitrary phase profiles and generalized flip angles. The advantage of this framework with a convex optimization approach is the flexible trade-off of different pulse characteristics. Designs for specialized selective RF pulses for balanced SSFP hyperpolarized (HP) 13C MRI, a dualband saturation RF pulse for 1H MR spectroscopy, and a pre-saturation pulse for HP 13C study were developed and tested.
Extra-axial isolated cerebral varix misdiagnosed as convexity meningioma
Tan, Zhi-Gang; Zhou, Qian; Cui, Yan; Yi, Lei; Ouyang, Yian; Jiang, Yugang
2016-01-01
Abstract Isolated cerebral varix is a rare cerebrovascular anomaly, which is easily misdiagnosed as other brain tumors. A 59-year-old female patient with noncontributory medical history presented with headache and insomnia for the last 2 months. Upon admission, her neurological examination was unremarkable. Magnetic resonance imaging revealed a well-demarcated extra medullary mass, 11 × 11 mm in size, within the subdural space at the right frontal lobe. The lesion was initially interpreted as a convexity meningioma. After conducting a craniotomy on the patient, an extra-axial varix was exposed and resected subsequently. The patient's headache was resolved soon after surgery and charged without neurologic sequelae. Extra-axial isolated cerebral varix is mimicking convexity meningioma on MR images and should be considered as a differential diagnosis. The focal erosion in the inner table of the skull could be an important character of extra-axial isolated cerebral varix. An extremely round shape and smooth contour of the lesion was another important character. Isolated cerebral varix is rare vascular lesion that is treated surgically in the case of rupture or compression of adjacent structures. The information obtained with noninvasive imaging techniques should include CTA to make a clinical decision. PMID:27368037
Mixed convection heat transfer in concave and convex channels
Moukalled, F.; Doughan, A.; Acharya, S.
1997-07-01
Mixed convection heat transfer studies in the literature have been primarily confined to pipe and rectangular channel geometry's. In some applications, however, heat transfer in curved channels may be of interest (e.g., nozzle and diffuser shaped passages in HVAC systems, fume hoods, chimneys, bell-shaped or dome-shaped chemical reactors, etc.). A numerical investigation of laminar mixed convection heat transfer of air in concave and convex channels is presented. Six different channel aspects ratios (R/L = 1.04, 1.25, 2.5, 5, 10, and {infinity}) and five different values of Gr/Re{sup 2} (Gr/Re{sup 2} = 0, 0.1, 1, 3, 5) are considered. Results are displayed in terms of streamline and isotherm plots, velocity and temperature profiles, and local and average Nusselt number estimates. Numerical predictions reveal that compared to straight channels of equal height, concave channels of low aspect ratio have lower heat transfer at relatively low values of Gr/Re{sup 2} and higher heat transfer at high values of Gr/Re{sup 2}. When compared to straight channels of equal heated length, concave channels are always found to have lower heat transfer and for all values of Gr/Re{sup 2}. On the other hand, predictions for convex channels revealed enhancement in heat transfer compared to straight channels of equal height and/or equal heated length for all values of Gr/Re{sup 2}.
Supersonic cavity flows over concave and convex walls
NASA Astrophysics Data System (ADS)
Ye, A. Ran; Das, Rajarshi; Setoguchi, Toshiaki; Kim, Heuy Dong
2016-04-01
Supersonic cavity flows are characterized by compression and expansion waves, shear layer, and oscillations inside the cavity. For decades, investigations into cavity flows have been conducted, mostly with flows at zero pressure gradient entering the cavity in straight walls. Since cavity flows on curved walls exert centrifugal force, the features of these flows are likely to differ from those of straight wall flows. The aim of the present work is to study the flow physics of a cavity that is cut out on a curved wall. Steady and unsteady numerical simulations were carried out for supersonic flow through curved channels over the cavity with L/H = 1. A straight channel flow was also analyzed which serves as the base model. The velocity gradient along the width of the channel was observed to increase with increasing the channel curvature for both concave and convex channels. The pressure on the cavity floor increases with the increase in channel curvature for concave channels and decreases for convex channels. Moreover, unsteady flow characteristics are more dependent on channel curvature under supersonic free stream conditions.
A Deep-Cutting-Plane Technique for Reverse Convex Optimization.
Moshirvaziri, K; Amouzegar, M A
2011-08-01
A large number of problems in engineering design and in many areas of social and physical sciences and technology lend themselves to particular instances of problems studied in this paper. Cutting-plane methods have traditionally been used as an effective tool in devising exact algorithms for solving convex and large-scale combinatorial optimization problems. Its utilization in nonconvex optimization has been also promising. A cutting plane, essentially a hyperplane defined by a linear inequality, can be used to effectively reduce the computational efforts in search of a global solution. Each cut is generated in order to eliminate a large portion of the search domain. Thus, a deep cut is intuitively superior in which it will exclude a larger set of extraneous points from consideration. This paper is concerned with the development of deep-cutting-plane techniques applied to reverse-convex programs. An upper bound and a lower bound for the optimal value are found, updated, and improved at each iteration. The algorithm terminates when the two bounds collapse or all the generated subdivisions have been fathomed. Finally, computational considerations and numerical results on a set of test problems are discussed. An illustrative example, walking through the steps of the algorithm and explaining the computational process, is presented. PMID:21296710
A convex minimization approach to data association with prior constraints
NASA Astrophysics Data System (ADS)
Chen, Huimin; Kirubarajan, Thiagalingam
2004-08-01
In this paper we propose a new formulation for reliably solving the measurement-to-track association problem with a priori constraints. Those constraints are incorporated into the scalar objective function in a general formula. This is a key step in most target tracking problems when one has to handle the measurement origin uncertainty. Our methodology is able to formulate the measurement-to-track correspondence problem with most of the commonly used assumptions and considers target feature measurements and possibly unresolved measurements as well. The resulting constrained optimization problem deals with the whole combinatorial space of possible feature selections and measurement-to-track correspondences. To find the global optimal solution, we build a convex objective function and relax the integer constraint. The special structure of this extended problem assures its equivalence to the original one, but it can be solved optimally by efficient algorithms to avoid the cominatorial search. This approach works for any cost function with continuous second derivatives. We use a track formation example and a multisensor tracking scenario to illustrate the effectiveness of the convex programming approach.
Multiband RF pulses with improved performance via convex optimization.
Shang, Hong; Larson, Peder E Z; Kerr, Adam; Reed, Galen; Sukumar, Subramaniam; Elkhaled, Adam; Gordon, Jeremy W; Ohliger, Michael A; Pauly, John M; Lustig, Michael; Vigneron, Daniel B
2016-01-01
Selective RF pulses are commonly designed with the desired profile as a low pass filter frequency response. However, for many MRI and NMR applications, the spectrum is sparse with signals existing at a few discrete resonant frequencies. By specifying a multiband profile and releasing the constraint on "don't-care" regions, the RF pulse performance can be improved to enable a shorter duration, sharper transition, or lower peak B1 amplitude. In this project, a framework for designing multiband RF pulses with improved performance was developed based on the Shinnar-Le Roux (SLR) algorithm and convex optimization. It can create several types of RF pulses with multiband magnitude profiles, arbitrary phase profiles and generalized flip angles. The advantage of this framework with a convex optimization approach is the flexible trade-off of different pulse characteristics. Designs for specialized selective RF pulses for balanced SSFP hyperpolarized (HP) (13)C MRI, a dualband saturation RF pulse for (1)H MR spectroscopy, and a pre-saturation pulse for HP (13)C study were developed and tested. PMID:26754063
Convex foundations for generalized MaxEnt models
NASA Astrophysics Data System (ADS)
Frongillo, Rafael; Reid, Mark D.
2014-12-01
We present an approach to maximum entropy models that highlights the convex geometry and duality of generalized exponential families (GEFs) and their connection to Bregman divergences. Using our framework, we are able to resolve a puzzling aspect of the bijection of Banerjee and coauthors between classical exponential families and what they call regular Bregman divergences. Their regularity condition rules out all but Bregman divergences generated from log-convex generators. We recover their bijection and show that a much broader class of divergences correspond to GEFs via two key observations: 1) Like classical exponential families, GEFs have a "cumulant" C whose subdifferential contains the mean: Eo˜pθ[φ(o)]∈∂C(θ) ; 2) Generalized relative entropy is a C-Bregman divergence between parameters: DF(pθ,pθ')= D C(θ,θ') , where DF becomes the KL divergence for F = -H. We also show that every incomplete market with cost function C can be expressed as a complete market, where the prices are constrained to be a GEF with cumulant C. This provides an entirely new interpretation of prediction markets, relating their design back to the principle of maximum entropy.
Shultz, Mary Jane; Brumberg, Alexandra; Bisson, Patrick J.; Shultz, Ryan
2015-01-01
The ability to prepare single-crystal faces has become central to developing and testing models for chemistry at interfaces, spectacularly demonstrated by heterogeneous catalysis and nanoscience. This ability has been hampered for hexagonal ice, Ih––a fundamental hydrogen-bonded surface––due to two characteristics of ice: ice does not readily cleave along a crystal lattice plane and properties of ice grown on a substrate can differ significantly from those of neat ice. This work describes laboratory-based methods both to determine the Ih crystal lattice orientation relative to a surface and to use that orientation to prepare any desired face. The work builds on previous results attaining nearly 100% yield of high-quality, single-crystal boules. With these methods, researchers can prepare authentic, single-crystal ice surfaces for numerous studies including uptake measurements, surface reactivity, and catalytic activity of this ubiquitous, fundamental solid. PMID:26512102
Convex Structures: Ray and Modal Techniques for Propagation and Scattering.
NASA Astrophysics Data System (ADS)
Heyman, Ehud
A self-contained theory of two-dimensional time -harmonic and transient fields scattered by and/or guided along a smooth convex object is presented. Emphasis is on the high frequency region where ray methods are applicable. Guidance along a smooth convex boundary is formulated in terms of a self-consistent system of rays which are complex due to energy leakage. These complex ray congruences are generated by a complex caustic whose location relative to the boundary determines the type of the guided mode: trapped wave with slight leakage, creeping wave or leaky wave. While closure can be invoked globally when the object has circular symmetry, a local closure condition can be found in the case of variable curvature when the caustic is close to the boundary. By imposing circumferential periodicity on the guided modes traveling around the object, one may synthesize the complex resonances which form the basis for analysis of transient scattering by the Singularity Expansion Method (SEM). A hybrid method is developed therefrom which expresses transient scattering by a perfectly conducting smooth convex cylinder in terms of a well-defined combination of traveling (creeping) wave fields and of SEM resonances. The former describe efficiently the high-frequency effects that dominate the early time response while the latter are more appropriate for the lower frequency behavior at later times. Intimately related to the phenomena described above is the mechanism of excitation of ray fields, and the associated energy transfer, when a source is located near a curved interface. This problem is explored for a canonical prototype that involves a high-frequency line source on the concave (interior) side of a curved dielectric interface, which side also contains the denser medium. A detailed study of the transmitted field resolves the intricate behavior in the vicinity of the critically refracted ray in terms of GTD parameters appropriate to regular and to transition regions. The
Chance-Constrained Guidance With Non-Convex Constraints
NASA Technical Reports Server (NTRS)
Ono, Masahiro
2011-01-01
Missions to small bodies, such as comets or asteroids, require autonomous guidance for descent to these small bodies. Such guidance is made challenging by uncertainty in the position and velocity of the spacecraft, as well as the uncertainty in the gravitational field around the small body. In addition, the requirement to avoid collision with the asteroid represents a non-convex constraint that means finding the optimal guidance trajectory, in general, is intractable. In this innovation, a new approach is proposed for chance-constrained optimal guidance with non-convex constraints. Chance-constrained guidance takes into account uncertainty so that the probability of collision is below a specified threshold. In this approach, a new bounding method has been developed to obtain a set of decomposed chance constraints that is a sufficient condition of the original chance constraint. The decomposition of the chance constraint enables its efficient evaluation, as well as the application of the branch and bound method. Branch and bound enables non-convex problems to be solved efficiently to global optimality. Considering the problem of finite-horizon robust optimal control of dynamic systems under Gaussian-distributed stochastic uncertainty, with state and control constraints, a discrete-time, continuous-state linear dynamics model is assumed. Gaussian-distributed stochastic uncertainty is a more natural model for exogenous disturbances such as wind gusts and turbulence than the previously studied set-bounded models. However, with stochastic uncertainty, it is often impossible to guarantee that state constraints are satisfied, because there is typically a non-zero probability of having a disturbance that is large enough to push the state out of the feasible region. An effective framework to address robustness with stochastic uncertainty is optimization with chance constraints. These require that the probability of violating the state constraints (i.e., the probability of
NASA Technical Reports Server (NTRS)
Weddendorf, Bruce (Inventor)
1991-01-01
A double face sealing device is disclosed for mounting between two surfaces to provide an air-tight and fluid-tight seal between a closure member bearing one of the surfaces and a structure or housing bearing the other surface which extends around the opening or hatchway to be closed. The double face sealing device includes a plurality of sections or segments mounted to one of the surfaces, each having a main body portion, a pair of outwardly extending and diverging, cantilever, spring arms, and a pair of inwardly extending and diverging, cantilever, spring arms, an elastomeric cover on the distal, free ends of the outwardly extending and diverging spring arms, and an elastomeric cover on the distal, free, ends of the outwardly extending and diverging spring arms, and an elastomeric cover on the distal, free ends of the inwardly extending and diverging spring arms. The double face sealing device has application or use in all environments requiring a seal, but is particularly useful to seal openings or hatchways between compartments of spacecraft or aircraft.
Fast inference of ill-posed problems within a convex space
NASA Astrophysics Data System (ADS)
Fernandez-de-Cossio-Diaz, J.; Mulet, R.
2016-07-01
In multiple scientific and technological applications we face the problem of having low dimensional data to be justified by a linear model defined in a high dimensional parameter space. The difference in dimensionality makes the problem ill-defined: the model is consistent with the data for many values of its parameters. The objective is to find the probability distribution of parameter values consistent with the data, a problem that can be cast as the exploration of a high dimensional convex polytope. In this work we introduce a novel algorithm to solve this problem efficiently. It provides results that are statistically indistinguishable from currently used numerical techniques while its running time scales linearly with the system size. We show that the algorithm performs robustly in many abstract and practical applications. As working examples we simulate the effects of restricting reaction fluxes on the space of feasible phenotypes of a genome scale Escherichia coli metabolic network and infer the traffic flow between origin and destination nodes in a real communication network.
Wang, Tianyun; Lu, Xinfei; Yu, Xiaofei; Xi, Zhendong; Chen, Weidong
2014-01-01
In recent years, various applications regarding sparse continuous signal recovery such as source localization, radar imaging, communication channel estimation, etc., have been addressed from the perspective of compressive sensing (CS) theory. However, there are two major defects that need to be tackled when considering any practical utilization. The first issue is off-grid problem caused by the basis mismatch between arbitrary located unknowns and the pre-specified dictionary, which would make conventional CS reconstruction methods degrade considerably. The second important issue is the urgent demand for low-complexity algorithms, especially when faced with the requirement of real-time implementation. In this paper, to deal with these two problems, we have presented three fast and accurate sparse reconstruction algorithms, termed as HR-DCD, Hlog-DCD and Hlp-DCD, which are based on homotopy, dichotomous coordinate descent (DCD) iterations and non-convex regularizations, by combining with the grid refinement technique. Experimental results are provided to demonstrate the effectiveness of the proposed algorithms and related analysis. PMID:24675758
Wang, Tianyun; Lu, Xinfei; Yu, Xiaofei; Xi, Zhendong; Chen, Weidong
2014-01-01
In recent years, various applications regarding sparse continuous signal recovery such as source localization, radar imaging, communication channel estimation, etc., have been addressed from the perspective of compressive sensing (CS) theory. However, there are two major defects that need to be tackled when considering any practical utilization. The first issue is off-grid problem caused by the basis mismatch between arbitrary located unknowns and the pre-specified dictionary, which would make conventional CS reconstruction methods degrade considerably. The second important issue is the urgent demand for low-complexity algorithms, especially when faced with the requirement of real-time implementation. In this paper, to deal with these two problems, we have presented three fast and accurate sparse reconstruction algorithms, termed as HR-DCD, Hlog-DCD and Hlp-DCD, which are based on homotopy, dichotomous coordinate descent (DCD) iterations and non-convex regularizations, by combining with the grid refinement technique. Experimental results are provided to demonstrate the effectiveness of the proposed algorithms and related analysis. PMID:24675758
A convex complementarity approach for simulating large granular flows.
Tasora, A.; Anitescu, M.; Mathematics and Computer Science; Univ. degli Studi di Parma
2010-07-01
Aiming at the simulation of dense granular flows, we propose and test a numerical method based on successive convex complementarity problems. This approach originates from a multibody description of the granular flow: all the particles are simulated as rigid bodies with arbitrary shapes and frictional contacts. Unlike the discrete element method (DEM), the proposed approach does not require small integration time steps typical of stiff particle interaction; this fact, together with the development of optimized algorithms that can run also on parallel computing architectures, allows an efficient application of the proposed methodology to granular flows with a large number of particles. We present an application to the analysis of the refueling flow in pebble-bed nuclear reactors. Extensive validation of our method against both DEM and physical experiments results indicates that essential collective characteristics of dense granular flow are accurately predicted.
Nonparametric instrumental regression with non-convex constraints
NASA Astrophysics Data System (ADS)
Grasmair, M.; Scherzer, O.; Vanhems, A.
2013-03-01
This paper considers the nonparametric regression model with an additive error that is dependent on the explanatory variables. As is common in empirical studies in epidemiology and economics, it also supposes that valid instrumental variables are observed. A classical example in microeconomics considers the consumer demand function as a function of the price of goods and the income, both variables often considered as endogenous. In this framework, the economic theory also imposes shape restrictions on the demand function, such as integrability conditions. Motivated by this illustration in microeconomics, we study an estimator of a nonparametric constrained regression function using instrumental variables by means of Tikhonov regularization. We derive rates of convergence for the regularized model both in a deterministic and stochastic setting under the assumption that the true regression function satisfies a projected source condition including, because of the non-convexity of the imposed constraints, an additional smallness condition.
Convex probe endobronchial ultrasound: applications beyond conventional indications
Li, Peng; Zheng, Wei
2015-01-01
Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is maturing and gaining acceptance by more and more clinicians for lymph node staging of lung cancer and diagnosis of mediastinal and hilar masses or lymph node enlargement by convex probe endobronchial ultrasound (CP-EBUS). The application of CP-EBUS, however, is not limited to conventional indications. Diagnostically, elastography is a new technology for the differentiation of benign and malignant lymph nodes before aspiration. CP-EBUS can also be used for pulmonary vascular diseases, such as pulmonary embolism (PE) and non-thrombotic endovascular lesions (NELs). Therapeutically, CP-EBUS can be used for cyst drainage and drug injections. CP-EBUS is not limited to observation and aspiration of mediastinal masses and lymph nodes, but is also suitable for exploration of other tissues external to the central airway, which necessitates unprecedented skills for the bronchoscopist. PMID:26543618
Convex crystal x-ray spectrometer for laser plasma experiments
May, M.; Heeter, R.; Emig, J.
2004-10-01
Measuring time and space-resolved spectra is important for understanding Hohlraum and Halfraum plasmas. Experiments at the OMEGA laser have used the Nova TSPEC which was not optimized for the OMEGA diagnostic space envelope or for the needed spectroscopic coverage and resolution. An improved multipurpose spectrometer snout, the MSPEC, has been constructed and fielded on OMEGA. The MSPEC provides the maximal internal volume for mounting crystals without any beam interferences at either 2x or 3x magnification. The RAP crystal is in a convex mounting geometry bent to a 20 cm radius of curvature. The spectral resolution, E/dE, is about 200 at 2.5 keV. The spectral coverage is 2 to 4.5 keV. The MSPEC can record four separate spectra on the framing camera at time intervals of up to several ns. The spectrometer design and initial field-test performance will be presented and compared to that of the TSPEC.
Laplace's equation on convex polyhedra via the unified method
Ashton, A. C. L.
2015-01-01
We provide a new method to study the classical Dirichlet problem for Laplace's equation on a convex polyhedron. This new approach was motivated by Fokas’ unified method for boundary value problems. The central object in this approach is the global relation: an integral equation which couples the known boundary data and the unknown boundary values. This integral equation depends holomorphically on two complex parameters, and the resulting analysis takes place on a Banach space of complex analytic functions closely related to the classical Paley–Wiener space. We write the global relation in the form of an operator equation and prove that the relevant operator is bounded below using some novel integral identities. We give a new integral representation to the solution to the underlying boundary value problem which serves as a concrete realization of the fundamental principle of Ehrenpreis.
Convexity at finite temperature and non-extensive thermodynamics
NASA Astrophysics Data System (ADS)
Alexandre, J.
2016-09-01
Assuming that tunnel effect between two degenerate bare minima occurs, in a scalar field theory at finite volume, this article studies the consequences for the effective potential, to all loop orders. Convexity is achieved only if the two bare minima are taken into account in the path integral, and a new derivation of the effective potential is given, in the large volume limit. The effective potential then has a universal form, it is suppressed by the space time volume, and does not feature spontaneous symmetry breaking as long as the volume is finite. The finite temperature analysis leads to surprising thermal properties, following from the non-extensive expression for the free energy. Although the physical relevance of these results is not clear, the potential application to ultra-light scalar particles is discussed.
Computational stoning method for surface defect detection
NASA Astrophysics Data System (ADS)
Ma, Ninshu; Zhu, Xinhai
2013-12-01
Surface defects on outer panels of automotive bodies must be controlled in order to improve the surface quality. The detection and quantitative evaluation of surface defects are quite difficult because the deflection of surface defects is very small. One of detecting methods for surface defects used in factories is a stoning method in which a stone block is moved on the surface of a stamped panel. The computational stoning method was developed to detect surface low defect by authors based on a geometry contact algorithm between a stone block and a stamped panel. If the surface is convex, the stone block always contacts with the convex surface of a stamped panel and the contact gap between them is zero. If there is a surface low, the stone block does not contact to the surface and the contact gap can be computed based on contact algorithm. The convex surface defect can also be detected by applying computational stoning method to the back surface of a stamped panel. By performing two way stoning computations from both the normal surface and the back surface, not only the depth of surface low defect but also the height of convex surface defect can be detected. The surface low defect and convex surface defect can also be detected through multi-directions. Surface defects on the handle emboss of outer panels were accurately detected using the computational stoning method and compared with the real shape. A very good accuracy was obtained.
Laboratory radiometric calibration for the convex grating imaging spectrometer
NASA Astrophysics Data System (ADS)
Zhou, Jiankang; Chen, Xinhua; Chen, Yuheng; Ji, Yiqun; Shen, Weimin
2014-09-01
The radiometric calibration of imaging spectrometer plays an import role for scientific application of spectral data. The radiometric calibration accuracy is influenced by many factors, such as the stability and uniformity of light source, the transfer precision of radiation standard and so on. But the deviation from the linear response mode and the polarization effect of the imaging spectrometer are always neglected. In this paper, the linear radiometric calibration model is constructed and the radiometric linear response capacity is test by adjusting electric gain, exposure time and radiance level. The linear polarizer and the sine function fitting algorithm are utilized to measure polarization effect. The integrating sphere calibration system is constructed in our Lab and its spectral radiance is calibrated by a well-characterized and extremely stable NIST traceable transfer spectroradiometer. Our manufactured convex grating imaging spectrometer is relative and absolute calibrated based on the integrating sphere calibration system. The relative radiometric calibration data is used to remove or reduce the radiometric response non-uniformity every pixel of imaging spectrometer while the absolute radiometric calibration is used to construct the relationship between the physical radiant of the scene and the digital number of the image. The calibration coefficients are acquired at ten radiance levels. The diffraction noise in the images can be corrected by the calibration coefficients and the uniform radiance image can be got. The calibration result shows that our manufactured imaging spectrometer with convex grating has 3.0% degree of polarization and the uncertainties of the relative and absolute radiometric calibrations are 2.4% and 5.6% respectively.
Convexity of momentum map, Morse index, and quantum entanglement
NASA Astrophysics Data System (ADS)
Sawicki, Adam; Oszmaniec, Michał; Kuś, Marek
2014-03-01
We analyze from the topological perspective the space of all SLOCC (Stochastic Local Operations with Classical Communication) classes of pure states for composite quantum systems. We do it for both distinguishable and indistinguishable particles. In general, the topology of this space is rather complicated as it is a non-Hausdorff space. Using geometric invariant theory (GIT) and momentum map geometry, we propose a way to divide the space of all SLOCC classes into mathematically and physically meaningful families. Each family consists of possibly many "asymptotically" equivalent SLOCC classes. Moreover, each contains exactly one distinguished SLOCC class on which the total variance (a well-defined measure of entanglement) of the state Var[v] attains maximum. We provide an algorithm for finding critical sets of Var[v], which makes use of the convexity of the momentum map and allows classification of such defined families of SLOCC classes. The number of families is in general infinite. We introduce an additional refinement into finitely many groups of families using some developments in the momentum map geometry known as the Kirwan-Ness stratification. We also discuss how to define it equivalently using the convexity of the momentum map applied to SLOCC classes. Moreover, we note that the Morse index at the critical set of the total variance of state has an interpretation of number of non-SLOCC directions in which entanglement increases and calculate it for several exemplary systems. Finally, we introduce the SLOCC-invariant measure of entanglement as a square root of the total variance of state at the critical point and explain its geometric meaning.
Path Following in the Exact Penalty Method of Convex Programming
Zhou, Hua; Lange, Kenneth
2015-01-01
Classical penalty methods solve a sequence of unconstrained problems that put greater and greater stress on meeting the constraints. In the limit as the penalty constant tends to ∞, one recovers the constrained solution. In the exact penalty method, squared penalties are replaced by absolute value penalties, and the solution is recovered for a finite value of the penalty constant. In practice, the kinks in the penalty and the unknown magnitude of the penalty constant prevent wide application of the exact penalty method in nonlinear programming. In this article, we examine a strategy of path following consistent with the exact penalty method. Instead of performing optimization at a single penalty constant, we trace the solution as a continuous function of the penalty constant. Thus, path following starts at the unconstrained solution and follows the solution path as the penalty constant increases. In the process, the solution path hits, slides along, and exits from the various constraints. For quadratic programming, the solution path is piecewise linear and takes large jumps from constraint to constraint. For a general convex program, the solution path is piecewise smooth, and path following operates by numerically solving an ordinary differential equation segment by segment. Our diverse applications to a) projection onto a convex set, b) nonnegative least squares, c) quadratically constrained quadratic programming, d) geometric programming, and e) semidefinite programming illustrate the mechanics and potential of path following. The final detour to image denoising demonstrates the relevance of path following to regularized estimation in inverse problems. In regularized estimation, one follows the solution path as the penalty constant decreases from a large value. PMID:26366044
Stereo and shading contribute independently to shape convexity-concavity discrimination.
Aubin, Mercédès; Arguin, Martin
2014-01-01
The present study examined the joint contribution of shading and stereopsis to the perception of shape convexity-concavity. The stimuli were the images of a synthetic convex 3-D shape seen from viewpoints leading to ambiguity as to its convexity. Illumination came from either above or below, and from either the right or the left, and stimuli were presented dichoptically with normal binocular disparity, reversed disparity, or no disparity. Participants responded "convex" more often when the lighting came from above than from below. Also, participants responded that the shape was convex more often with normal than with zero disparity, and more often with zero disparity than with reversed stereopsis. The effects of lighting direction and display mode were additive--that is, they did not interact. This indicates that shading and stereopsis contribute independently to shape perception. PMID:25109021
Xiao, Jing; Liu, Shuo; Tian, Na; Zhou, Zhi-You; Liu, Hai-Xia; Xu, Bin-Bin; Sun, Shi-Gang
2013-12-18
Systematic manipulation of nanocrystal shapes is prerequisite for revealing their shape-dependent physical and chemical properties. Here we successfully prepared a complex shape of Pt micro/nanocrystals: convex hexoctahedron (HOH) enclosed with 48 {15 5 3} high-index facets by electrochemical square-wave-potential (SWP) method. This shape is the last crystal single form that had not been achieved previously for face-centered-cubic (fcc) metals. We further realized the shape evolution of Pt nanocrystals with high-index facets from tetrahexahedron (THH) to the HOH, and finally to trapezohedron (TPH) by increasing either the upper (EU) or lower potential (EL). The shape evolution, accompanied by the decrease of low-coordinated kink atoms, can be correlated with the competitive interactions between preferentially oxidative dissolution of kink atoms at high EU and the redeposition of Pt atoms at the EL. PMID:24299234
Podczeck, Fridrun; Drake, Kevin R; Newton, J Michael
2013-09-15
In the literature various solutions exist for the calculation of the diametral compression tensile strength of doubly-convex tablets and each approach is based on experimental data obtained from single materials (gypsum, microcrystalline cellulose) only. The solutions are represented by complex equations and further differ for elastic and elasto-plastic behaviour of the compacts. The aim of this work was to develop a general equation that is applicable independently of deformation behaviour and which is based on simple tablet dimensions such as diameter and total tablet thickness only. With the help of 3D-FEM analysis the tensile failure stress of doubly-convex tables with central cylinder to total tablet thickness ratios W/D between 0.06 and 0.50 and face-curvature ratios D/R between 0.25 and 1.85 were evaluated. Both elastic and elasto-plastic deformation behaviour were considered. The results of 80 individual simulations were combined and showed that the tensile failure stress σt of doubly-convex tablets can be calculated from σt=(2P/πDW)(W/T)=2P/πDT with P being the failure load, D the diameter, W the central cylinder thickness, and T the total thickness of the tablet. This equation converts into the standard Brazilian equation (σt=2P/πDW) when W equals T, i.e. is equally valid for flat cylindrical tablets. In practice, the use of this new equation removes the need for complex measurements of tablet dimensions, because it only requires values for diameter and total tablet thickness. It also allows setting of standards for the mechanical strength of doubly-convex tablets. The new equation holds both for elastic and elasto-plastic deformation behaviour of the tablets under load. It is valid for all combinations of W/D-ratios between 0.06 and 0.50 with D/R-ratios between 0.00 and 1.85 except for W/D=0.50 in combination with D/R-ratios of 1.85 and 1.43 and for W/D-ratios of 0.40 and 0.30 in combination with D/R=1.85. FEM-analysis indicated a tendency to
NASA Astrophysics Data System (ADS)
Blinov, E. V.
2016-01-01
The structure of the surface layer in high-nitrogen 05Kh22AG15N8M2F steel workpieces subjected to face turning is studied by electron microscopy. It is found that improved machinability by VK8 alloy cutting tools is achieved at a cutting depth of 0.25 mm and that the cutting-tool life decreases sharply when the cutting depth increases to 1 mm. A nanocrystalline structure with nanocrystal sizes from several to several tens of nanometers forms in the surface layer upon face turning in the as-cast, hot-rolled, and thermally deformed states. The structure of the surface layer is characterized by a high dislocation density and large austenite fragments with broad subgrains and deformation twins.
NASA Astrophysics Data System (ADS)
Nemec, Lydia; Lazarevic, Florian; Rinke, Patrick; Scheffler, Matthias; Blum, Volker
2015-04-01
We address the stability of the surface phases that occur on the C side of 3 C -SiC (1 ¯1 ¯1 ¯) at the onset of graphene formation. In this growth range, experimental reports reveal a coexistence of several surface phases. This coexistence can be explained by a Si-rich model for the unknown (3 ×3 ) reconstruction, the known (2 ×2 )C adatom phase, and the graphene-covered (2 ×2)C phase. By constructing an ab initio surface phase diagram using a van der Waals corrected density functional, we show that the formation of a well defined interface structure like the "buffer layer" on the Si side is blocked by Si-rich surface reconstructions.
Maximum margin classification based on flexible convex hulls for fault diagnosis of roller bearings
NASA Astrophysics Data System (ADS)
Zeng, Ming; Yang, Yu; Zheng, Jinde; Cheng, Junsheng
2016-01-01
A maximum margin classification based on flexible convex hulls (MMC-FCH) is proposed and applied to fault diagnosis of roller bearings. In this method, the class region of each sample set is approximated by a flexible convex hull of its training samples, and then an optimal separating hyper-plane that maximizes the geometric margin between flexible convex hulls is constructed by solving a closest pair of points problem. By using the kernel trick, MMC-FCH can be extended to nonlinear cases. In addition, multi-class classification problems can be processed by constructing binary pairwise classifiers as in support vector machine (SVM). Actually, the classical SVM also can be regarded as a maximum margin classification based on convex hulls (MMC-CH), which approximates each class region with a convex hull. The convex hull is a special case of the flexible convex hull. To train a MMC-FCH classifier, time-domain and frequency-domain statistical parameters are extracted not only from raw vibration signals but also from the resulting intrinsic mode functions (IMFs) by performing empirical mode decomposition (EMD) on the raw signals, and then the distance evaluation technique (DET) is used to select salient features from the whole statistical features. The experiments on bearing datasets show that the proposed method can reliably recognize different bearing faults.
On the Convergence of the Iterative Shrinkage/Thresholding Algorithm With a Weakly Convex Penalty
NASA Astrophysics Data System (ADS)
Bayram, Ilker
2016-03-01
We consider the iterative shrinkage/thresholding algorithm (ISTA) applied to a cost function composed of a data fidelity term and a penalty term. The penalty is non-convex but the concavity of the penalty is accounted for by the data fidelity term so that the overall cost function is convex. We provide a generalization of the convergence result for ISTA viewed as a forward-backward splitting algorithm. We also demonstrate experimentally that for the current setup, using large stepsizes in ISTA can accelerate convergence more than existing schemes proposed for the convex case, like TwIST or FISTA.
Min-max identities on boundaries of convex sets around the origin
Grcar, Joseph F.
2002-01-31
Min-max and max-min identities are found for inner products on the boundaries of compact, convex sets whose interiors contain the origin. The identities resemble the minimax theorem but they are different from it. Specifically, the value of each min-max (or max-min) equals the value of a dual problem of the same type. Their solution sets can be characterized geometrically in terms of the enclosed convex sets and their polar sets. However, the solution sets need not be convex nor even connected.
NASA Technical Reports Server (NTRS)
2003-01-01
MGS MOC Release No. MOC2-361, 15 May 2003
Every day, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) wide angle instruments obtain a global view of the planet to help monitor weather and seasonal patterns of frost deposition and removal. The two pictures shown here are taken from the same daily global image mosaic (the only difference is that each was processed slightly differently). The pictures show Galle Crater, informally known as 'Happy Face,' as it appeared in early southern winter. The white-ish gray surfaces are coated with wintertime carbon dioxide frost. The pattern of frost distribution gives the appearance that 'Happy Face' has opened its mouth. Galle Crater is located on the east rim of Argyre at 51oS, 31oW. Sunlight illuminates the scene from the upper left. Galle Crater is 230 km (143 mi) across.
Optimization-based mesh correction with volume and convexity constraints
D'Elia, Marta; Ridzal, Denis; Peterson, Kara J.; Bochev, Pavel; Shashkov, Mikhail
2016-02-24
Here, we consider the problem of finding a mesh such that 1) it is the closest, with respect to a suitable metric, to a given source mesh having the same connectivity, and 2) the volumes of its cells match a set of prescribed positive values that are not necessarily equal to the cell volumes in the source mesh. Also, this volume correction problem arises in important simulation contexts, such as satisfying a discrete geometric conservation law and solving transport equations by incremental remapping or similar semi-Lagrangian transport schemes. In this paper we formulate volume correction as a constrained optimization problemmore » in which the distance to the source mesh defines an optimization objective, while the prescribed cell volumes, mesh validity and/or cell convexity specify the constraints. We solve this problem numerically using a sequential quadratic programming (SQP) method whose performance scales with the mesh size. To achieve scalable performance we develop a specialized multigrid-based preconditioner for optimality systems that arise in the application of the SQP method to the volume correction problem. Numerical examples illustrate the importance of volume correction, and showcase the accuracy, robustness and scalability of our approach.« less
On the length and area spectrum of analytic convex domains
NASA Astrophysics Data System (ADS)
Martín, Pau; Ramírez-Ros, Rafael; Tamarit-Sariol, Anna
2016-01-01
Area-preserving twist maps have at least two different (p, q)-periodic orbits and every (p, q)-periodic orbit has its (p, q)-periodic action for suitable couples (p, q). We establish an exponentially small upper bound for the differences of (p, q)-periodic actions when the map is analytic on a (m, n)-resonant rotational invariant curve (resonant RIC) and p/q is ‘sufficiently close’ to m/n. The exponent in this upper bound is closely related to the analyticity strip width of a suitable angular variable. The result is obtained in two steps. First, we prove a Neishtadt-like theorem, in which the n-th power of the twist map is written as an integrable twist map plus an exponentially small remainder on the distance to the RIC. Second, we apply the MacKay-Meiss-Percival action principle. We apply our exponentially small upper bound to several billiard problems. The resonant RIC is a boundary of the phase space in almost all of them. For instance, we show that the lengths (respectively, areas) of all the (1, q)-periodic billiard (respectively, dual billiard) trajectories inside (respectively, outside) analytic strictly convex domains are exponentially close in the period q. This improves some classical results of Marvizi, Melrose, Colin de Verdière, Tabachnikov, and others about the smooth case.
A Localization Method for Multistatic SAR Based on Convex Optimization
2015-01-01
In traditional localization methods for Synthetic Aperture Radar (SAR), the bistatic range sum (BRS) estimation and Doppler centroid estimation (DCE) are needed for the calculation of target localization. However, the DCE error greatly influences the localization accuracy. In this paper, a localization method for multistatic SAR based on convex optimization without DCE is investigated and the influence of BRS estimation error on localization accuracy is analysed. Firstly, by using the information of each transmitter and receiver (T/R) pair and the target in SAR image, the model functions of T/R pairs are constructed. Each model function’s maximum is on the circumference of the ellipse which is the iso-range for its model function’s T/R pair. Secondly, the target function whose maximum is located at the position of the target is obtained by adding all model functions. Thirdly, the target function is optimized based on gradient descent method to obtain the position of the target. During the iteration process, principal component analysis is implemented to guarantee the accuracy of the method and improve the computational efficiency. The proposed method only utilizes BRSs of a target in several focused images from multistatic SAR. Therefore, compared with traditional localization methods for SAR, the proposed method greatly improves the localization accuracy. The effectivity of the localization approach is validated by simulation experiment. PMID:26566031
Convex Crystal X-ray Spectrometer for Laser Plasma Experiments
May, M; Heeter, R; Emig, J
2004-04-15
Measuring time and space-resolved spectra is important for understanding Hohlraum and Halfraum plasmas. Experiments at the OMEGA laser have used the Nova TSPEC which was not optimized for the OMEGA diagnostic space envelope or for the needed spectroscopic coverage and resolution. An improved multipurpose spectrometer snout, the MSPEC, has been constructed and fielded on OMEGA. The MSPEC provides the maximal internal volume for mounting crystals without any beam interferences at either 2x or 3x magnification. The RAP crystal is in a convex mounting geometry bent to a 20 cm radius of curvature. The spectral resolution, E/dE, is about 200 at 2.5 keV. The spectral coverage is 2 to 4.5 keV. The MSPEC can record four separate spectra on the framing camera at time intervals of up to several ns. The spectrometer design and initial field-test performance will be presented and compared to that of the TSPEC. Work supported by U. S. DoE/UC LLNL contract W-7405-ENG-48
A Localization Method for Multistatic SAR Based on Convex Optimization.
Zhong, Xuqi; Wu, Junjie; Yang, Jianyu; Sun, Zhichao; Huang, Yuling; Li, Zhongyu
2015-01-01
In traditional localization methods for Synthetic Aperture Radar (SAR), the bistatic range sum (BRS) estimation and Doppler centroid estimation (DCE) are needed for the calculation of target localization. However, the DCE error greatly influences the localization accuracy. In this paper, a localization method for multistatic SAR based on convex optimization without DCE is investigated and the influence of BRS estimation error on localization accuracy is analysed. Firstly, by using the information of each transmitter and receiver (T/R) pair and the target in SAR image, the model functions of T/R pairs are constructed. Each model function's maximum is on the circumference of the ellipse which is the iso-range for its model function's T/R pair. Secondly, the target function whose maximum is located at the position of the target is obtained by adding all model functions. Thirdly, the target function is optimized based on gradient descent method to obtain the position of the target. During the iteration process, principal component analysis is implemented to guarantee the accuracy of the method and improve the computational efficiency. The proposed method only utilizes BRSs of a target in several focused images from multistatic SAR. Therefore, compared with traditional localization methods for SAR, the proposed method greatly improves the localization accuracy. The effectivity of the localization approach is validated by simulation experiment. PMID:26566031
JPEG2000-coded image error concealment exploiting convex sets projections.
Atzori, Luigi; Ginesu, Giaime; Raccis, Alessio
2005-04-01
Transmission errors in JPEG2000 can be grouped into three main classes, depending on the affected area: LL, high frequencies at the lower decomposition levels, and high frequencies at the higher decomposition levels. The first type of errors are the most annoying but can be concealed exploiting the signal spatial correlation like in a number of techniques proposed in the past; the second are less annoying but more difficult to address; the latter are often imperceptible. In this paper, we address the problem of concealing the second class or errors when high bit-planes are damaged by proposing a new approach based on the theory of projections onto convex sets. Accordingly, the error effects are masked by iteratively applying two procedures: low-pass (LP) filtering in the spatial domain and restoration of the uncorrupted wavelet coefficients in the transform domain. It has been observed that a uniform LP filtering brought to some undesired side effects that negatively compensated the advantages. This problem has been overcome by applying an adaptive solution, which exploits an edge map to choose the optimal filter mask size. Simulation results demonstrated the efficiency of the proposed approach. PMID:15825483
Guaranteed Blind Sparse Spikes Deconvolution via Lifting and Convex Optimization
NASA Astrophysics Data System (ADS)
Chi, Yuejie
2016-06-01
Neural recordings, returns from radars and sonars, images in astronomy and single-molecule microscopy can be modeled as a linear superposition of a small number of scaled and delayed copies of a band-limited or diffraction-limited point spread function, which is either determined by the nature or designed by the users; in other words, we observe the convolution between a point spread function and a sparse spike signal with unknown amplitudes and delays. While it is of great interest to accurately resolve the spike signal from as few samples as possible, however, when the point spread function is not known a priori, this problem is terribly ill-posed. This paper proposes a convex optimization framework to simultaneously estimate the point spread function as well as the spike signal, by mildly constraining the point spread function to lie in a known low-dimensional subspace. By applying the lifting trick, we obtain an underdetermined linear system of an ensemble of signals with joint spectral sparsity, to which atomic norm minimization is applied. Under mild randomness assumptions of the low-dimensional subspace as well as a separation condition of the spike signal, we prove the proposed algorithm, dubbed as AtomicLift, is guaranteed to recover the spike signal up to a scaling factor as soon as the number of samples is large enough. The extension of AtomicLift to handle noisy measurements is also discussed. Numerical examples are provided to validate the effectiveness of the proposed approaches.
Optimization-based mesh correction with volume and convexity constraints
NASA Astrophysics Data System (ADS)
D'Elia, Marta; Ridzal, Denis; Peterson, Kara J.; Bochev, Pavel; Shashkov, Mikhail
2016-05-01
We consider the problem of finding a mesh such that 1) it is the closest, with respect to a suitable metric, to a given source mesh having the same connectivity, and 2) the volumes of its cells match a set of prescribed positive values that are not necessarily equal to the cell volumes in the source mesh. This volume correction problem arises in important simulation contexts, such as satisfying a discrete geometric conservation law and solving transport equations by incremental remapping or similar semi-Lagrangian transport schemes. In this paper we formulate volume correction as a constrained optimization problem in which the distance to the source mesh defines an optimization objective, while the prescribed cell volumes, mesh validity and/or cell convexity specify the constraints. We solve this problem numerically using a sequential quadratic programming (SQP) method whose performance scales with the mesh size. To achieve scalable performance we develop a specialized multigrid-based preconditioner for optimality systems that arise in the application of the SQP method to the volume correction problem. Numerical examples illustrate the importance of volume correction, and showcase the accuracy, robustness and scalability of our approach.
Face adaptation depends on seeing the face.
Moradi, Farshad; Koch, Christof; Shimojo, Shinsuke
2005-01-01
Retinal input that is suppressed from visual awareness can nevertheless produce measurable aftereffects, revealing neural processes that do not directly result in a conscious percept. We here report that the face identity-specific aftereffect requires a visible face; it is effectively cancelled by binocular suppression or by inattentional blindness of the inducing face. Conversely, the same suppression does not interfere with the orientation-specific aftereffect. Thus, the competition between incompatible or interfering visual inputs to reach awareness is resolved before those aspects of information that are exploited in face identification are processed. We also found that the face aftereffect remained intact when the visual distracters in the inattention experiment were replaced with auditory distracters. Thus, cross-modal or cognitive interference that does not affect the visibility of the face does not interfere with the face aftereffect. We conclude that adaptation to face identity depends on seeing the face. PMID:15629711
Pongakkasira, Kaewmart; Bindemann, Markus
2015-04-01
Human face detection might be driven by skin-coloured face-shaped templates. To explore this idea, this study compared the detection of faces for which the natural height-to-width ratios were preserved with distorted faces that were stretched vertically or horizontally. The impact of stretching on detection performance was not obvious when faces were equated to their unstretched counterparts in terms of their height or width dimension (Experiment 1). However, stretching impaired detection when the original and distorted faces were matched for their surface area (Experiment 2), and this was found with both vertically and horizontally stretched faces (Experiment 3). This effect was evident in accuracy, response times, and also observers' eye movements to faces. These findings demonstrate that height-to-width ratios are an important component of the cognitive template for face detection. The results also highlight important differences between face detection and face recognition. PMID:25727491
NASA Technical Reports Server (NTRS)
2004-01-01
[figure removed for brevity, see original site]
Released 31 May 2004 This image was collected May 29, 2002 during northern spring season. The local time at the image location was about 3:30 pm. The image shows an area between Isidis Basin and Syrtis Major regions.
The THEMIS VIS camera is capable of capturing color images of the martian surface using its five different color filters. In this mode of operation, the spatial resolution and coverage of the image must be reduced to accommodate the additional data volume produced from the use of multiple filters. To make a color image, three of the five filter images (each in grayscale) are selected. Each is contrast enhanced and then converted to a red, green, or blue intensity image. These three images are then combined to produce a full color, single image. Because the THEMIS color filters don't span the full range of colors seen by the human eye, a color THEMIS image does not represent true color. Also, because each single-filter image is contrast enhanced before inclusion in the three-color image, the apparent color variation of the scene is exaggerated. Nevertheless, the color variation that does appear is representative of some change in color, however subtle, in the actual scene. Note that the long edges of THEMIS color images typically contain color artifacts that do not represent surface variation.
Image information: VIS instrument. Latitude 14, Longitude 79.1 East (28.9 West). 38 meter/pixel resolution.
Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.
NASA's Jet
NASA Astrophysics Data System (ADS)
Kuo, K.; Clune, T.; Pearson, C.; Olson, W. S.; Skofronick-Jackson, G.; Gravner, J.; Griffeath, D.
2010-12-01
This study improves upon an earlier, preliminary study using only three size bins based on maximum diameter in which it is found that the single-scattering properties of ensembles of non-spherical precipitation particles can be better characterized by considering the non-convexity of these particles. The difficulty of retrievals involving non-spherical particles stems not only from the fact that these particles are not spherical but also the fact that the shape composition of an ensemble of particles is usually unknown and the possibility of its mixture is infinite. Being able to adequately characterize the single-scattering properties of ensembles involving these non-spherical particles with as few parameters as possible is at the heart of solving this thorny remote sensing problem. Inspired by how well three parameters, i.e. water content, effective radius, and effective variance (or their equivalent), characterize the single-scattering properties of an ensemble of spherical particles of varying sizes, we set out to find additional parameters that generalize these three for ensembles of non-spherical particles. We find that a non-convexity measure appears to be one of these additional parameters. Non-convexity is expressed as a ratio of two effective radii derived from the moments of a given particle size distribution (PSD), each of which is in essence a ratio of ensemble particle volume to area. The effective radius in the numerator (denoted as rA) of the non-convexity ratio is based on the projection area of the particle ensemble whereas the one in the denominator (denoted as rS) is based on the surface area. In the preliminary study with PSDs having only three size bins, it is found that variations in the single-scattering properties, such as the scattering and extinction coefficients, the asymmetry factor, and even the scattering phase function, of a particle ensemble with a specified water content are very limited (practically non-existent), if 1) the habit
New integral inequalities for co-ordinated m-convex functions
NASA Astrophysics Data System (ADS)
Akdemir, Ahmet Ocak; Özdemir, M. Emin
2016-04-01
In this paper, we prove some new integral inequalities for co-ordinated m -convex functions by using a new integral identity and basic definitions. We also give some reduced results by selecting special value of parameter m.
A Convex Atomic-Norm Approach to Multiple Sequence Alignment and Motif Discovery
Yen, Ian E. H.; Lin, Xin; Zhang, Jiong; Ravikumar, Pradeep; Dhillon, Inderjit S.
2016-01-01
Multiple Sequence Alignment and Motif Discovery, known as NP-hard problems, are two fundamental tasks in Bioinformatics. Existing approaches to these two problems are based on either local search methods such as Expectation Maximization (EM), Gibbs Sampling or greedy heuristic methods. In this work, we develop a convex relaxation approach to both problems based on the recent concept of atomic norm and develop a new algorithm, termed Greedy Direction Method of Multiplier, for solving the convex relaxation with two convex atomic constraints. Experiments show that our convex relaxation approach produces solutions of higher quality than those standard tools widely-used in Bioinformatics community on the Multiple Sequence Alignment and Motif Discovery problems. PMID:27559428
Constrained iterations for blind deconvolution and convexity issues
NASA Astrophysics Data System (ADS)
Spaletta, Giulia; Caucci, Luca
2006-12-01
The need for image restoration arises in many applications of various scientific disciplines, such as medicine and astronomy and, in general, whenever an unknown image must be recovered from blurred and noisy data [M. Bertero, P. Boccacci, Introduction to Inverse Problems in Imaging, Institute of Physics Publishing, Philadelphia, PA, USA, 1998]. The algorithm studied in this work restores the image without the knowledge of the blur, using little a priori information and a blind inverse filter iteration. It represents a variation of the methods proposed in Kundur and Hatzinakos [A novel blind deconvolution scheme for image restoration using recursive filtering, IEEE Trans. Signal Process. 46(2) (1998) 375-390] and Ng et al. [Regularization of RIF blind image deconvolution, IEEE Trans. Image Process. 9(6) (2000) 1130-1134]. The problem of interest here is an inverse one, that cannot be solved by simple filtering since it is ill-posed. The imaging system is assumed to be linear and space-invariant: this allows a simplified relationship between unknown and observed images, described by a point spread function modeling the distortion. The blurring, though, makes the restoration ill-conditioned: regularization is therefore also needed, obtained by adding constraints to the formulation. The restoration is modeled as a constrained minimization: particular attention is given here to the analysis of the objective function and on establishing whether or not it is a convex function, whose minima can be located by classic optimization techniques and descent methods. Numerical examples are applied to simulated data and to real data derived from various applications. Comparison with the behavior of methods [D. Kundur, D. Hatzinakos, A novel blind deconvolution scheme for image restoration using recursive filtering, IEEE Trans. Signal Process. 46(2) (1998) 375-390] and [M. Ng, R.J. Plemmons, S. Qiao, Regularization of RIF Blind Image Deconvolution, IEEE Trans. Image Process. 9
SLOPE—ADAPTIVE VARIABLE SELECTION VIA CONVEX OPTIMIZATION
Bogdan, Małgorzata; van den Berg, Ewout; Sabatti, Chiara; Su, Weijie; Candès, Emmanuel J.
2015-01-01
We introduce a new estimator for the vector of coefficients β in the linear model y = Xβ + z, where X has dimensions n × p with p possibly larger than n. SLOPE, short for Sorted L-One Penalized Estimation, is the solution to minb∈ℝp12‖y−Xb‖ℓ22+λ1|b|(1)+λ2|b|(2)+⋯+λp|b|(p),where λ1 ≥ λ2 ≥ … ≥ λp ≥ 0 and |b|(1)≥|b|(2)≥⋯≥|b|(p) are the decreasing absolute values of the entries of b. This is a convex program and we demonstrate a solution algorithm whose computational complexity is roughly comparable to that of classical ℓ1 procedures such as the Lasso. Here, the regularizer is a sorted ℓ1 norm, which penalizes the regression coefficients according to their rank: the higher the rank—that is, stronger the signal—the larger the penalty. This is similar to the Benjamini and Hochberg [J. Roy. Statist. Soc. Ser. B 57 (1995) 289–300] procedure (BH) which compares more significant p-values with more stringent thresholds. One notable choice of the sequence {λi} is given by the BH critical values λBH(i)=z(1−i⋅q/2p), where q ∈ (0, 1) and z(α) is the quantile of a standard normal distribution. SLOPE aims to provide finite sample guarantees on the selected model; of special interest is the false discovery rate (FDR), defined as the expected proportion of irrelevant regressors among all selected predictors. Under orthogonal designs, SLOPE with λBH provably controls FDR at level q. Moreover, it also appears to have appreciable inferential properties under more general designs X while having substantial power, as demonstrated in a series of experiments running on both simulated and real data. PMID:26709357
ERIC Educational Resources Information Center
Thompson, Greg; Cook, Ian
2013-01-01
This paper uses Deleuze and Guattari's concept of faciality to analyse the teacher's face. According to Deleuze and Guattari, the teacher-face is a special type of face because it is an "overcoded" face produced in specific landscapes. This paper suggests four limit-faces for teacher faciality that actualise different mixes of significance and…
Learning Faces from Photographs
ERIC Educational Resources Information Center
Longmore, Christopher A.; Liu, Chang Hong; Young, Andrew W.
2008-01-01
Previous studies examining face learning have mostly used only a single exposure to 1 image of each of the faces to be learned. However, in daily life, faces are usually learned from multiple encounters. These 6 experiments examined the effects on face learning of repeated exposures to single or multiple images of a face. All experiments…
A Face Inversion Effect without a Face
ERIC Educational Resources Information Center
Brandman, Talia; Yovel, Galit
2012-01-01
Numerous studies have attributed the face inversion effect (FIE) to configural processing of internal facial features in upright but not inverted faces. Recent findings suggest that face mechanisms can be activated by faceless stimuli presented in the context of a body. Here we asked whether faceless stimuli with or without body context may induce…
Wang, Qin; Zhang, Bo; Wang, Muhua; Wu, Jiang; Li, Yuyou; Gao, Yingxin; Li, Weicheng; Jin, Yong
2016-11-01
The batch and column experimental studies on the adsorption of phosphate onto synthetic lepidocrocite from reclaimed water are presented. A second-order polynomial model in the batch study is successfully applied to describe phosphate immobilization performance using the response surface methodology. The model proposed is further linked with the convex optimization method to determine the optimal variables for maximum phosphate uptake since convex method is a global optimization method. Consequently, under optimal parameters determined as pH of 3.88, an initial P concentration of 0.66 mg/L, and a dosage of 0.15 g, the corresponding phosphate removal efficiency can reach up to 97.4%. Adsorption behavior is further revealed by X-ray photoelectron spectroscopy observation and FTIR spectra. A comparative column study indicates that co-existing competing anions in artificial reclaimed water do not significantly interfere with P adsorption under the neutral condition. The experimental results highlight that synthetic lepidocrocite is an excellent absorbent for sustainable P removal from reclaimed water. PMID:27121116
NASA Technical Reports Server (NTRS)
Munson, John
2009-01-01
In the seal literature you can find many attempts by various researchers to adapt film riding seals to the gas turbine engine. None have been successful, potential distortion of the sealing faces is the primary reason. There is a film riding device that does accommodate distortion and is in service in aircraft applications, namely the foil bearing. More specifically a foil thrust bearing. These are not intended to be seals, and they do not accommodate large axial movement between shaft & static structure. By combining the 2 a unique type of face seal has been created. It functions like a normal face seal. The foil thrust bearing replaces the normal primary sealing surface. The compliance of the foil bearing allows the foils to track distortion of the mating seal ring. The foil seal has several perceived advantages over existing hydrodynamic designs, enumerated in the chart. Materials and design methodology needed for this application already exist. Also the load capacity requirements for the foil bearing are low since it only needs to support itself and overcome friction forces at the antirotation keys.
Imaging through a convex interface with unknown position and shape using an ultrasonic linear array
NASA Astrophysics Data System (ADS)
Matuda, Marcelo Y.; Buiochi, Flávio; Adamowski, Julio C.
2012-05-01
This paper presents a technique for improving the internal imaging of a solid object immersed in water using an ultrasonic array. This technique consists in determining the position and shape of a convex object surface using a combination of synthetic transmit aperture (STA) and sign coherence factor (SCF) methods. The SCF attenuates the grating lobe noise. The technique is applied to a cylindrical aluminium object with internal holes simulating defects. The first step is the acquisition of a sequence of STA images with SCF, using a distinct group of adjacent array elements for each image. In the second step, a circle is fitted to the positions of the peak values in each image. Finally, using the Fermat's principle and this circle as the interface between the water and the metallic object, the propagation delays from the array elements to the image grid points may be calculated and used in another STA image. In this final image, the small holes in the cylindrical object can clearly be identified. The effects of the SCF for a large diameter circular reflector are simulated and compared with experimental data.
Melecky, Roman; Socha, Vladimir; Kutilek, Patrik; Hanakova, Lenka; Takac, Peter; Schlenker, Jakub; Svoboda, Zdenek
2016-01-01
Techniques to quantify postural stability usually rely on the evaluation of only two variables, that is, two coordinates of COP. However, by using three variables, that is, three components of acceleration vector, it is possible to describe human movement more precisely. For this purpose, a single three-axis accelerometer was used, making it possible to evaluate 3D movement by use of a novel method, convex polyhedron (CP), together with a traditional method, based on area of the confidence ellipse (ACE). Ten patients (Pts) with cerebellar ataxia and eleven healthy individuals of control group (CG) participated in the study. The results show a significant increase of volume of the CP (CPV) in Pts or CG standing on foam surface with eyes open (EO) and eyes closed (EC) after the EC phase. Significant difference between Pts and CG was found in all cases as well. Correlation coefficient indicates strong correlation between the CPV and ACE in most cases of patient examinations, thus confirming the possibility of quantification of postural instability by the introduced method of CPV. PMID:27195465
Head and face reconstruction is surgery to repair or reshape deformities of the head and face (craniofacial). ... How surgery for head and face deformities (craniofacial reconstruction) ... and the person's condition. Surgical repairs involve the ...
Plasmonic black metals by broadband light absorption in ultra-sharp convex grooves
NASA Astrophysics Data System (ADS)
Beermann, Jonas; Eriksen, René L.; Søndergaard, Thomas; Holmgaard, Tobias; Pedersen, Kjeld; Bozhevolnyi, Sergey I.
2013-07-01
We have recently reported broadband (450-850 nm) and efficient (96% on average) light absorption on gold surfaces with arrays of ultra-sharp convex grooves via excitation and subsequent adiabatic nanofocusing and absorption of gap surface plasmon modes (Søndergaard et al 2012 Nature Commun. 3 969). Here, we significantly extend our spectroscopy investigations of one- and two-dimensional (1D and 2D) groove arrays in gold covering the wavelength range of 500-1700 nm and report first results on broadband light absorption by 1D groove arrays in nickel. For 1D groove arrays (periods 250 and 350 nm, groove depth 450 nm) in gold, the experimental characterization as well as numerical simulations based on the surface integral equation method reveal gradually increasing reflectivity for wavelengths above ˜650 nm reaching finally ˜60% at 1700 nm, but with a remarkable dip around 1150-1250 nm featuring only ˜10% reflectivity. Results indicate that the dip position can be adjusted with the precise groove geometry, a feature that could prove particularly useful for selective thermal emitters in thermophotovoltaics. Furthermore, investigations of field enhancement at the groove bottoms of 1D groove arrays in gold, mapped via diffraction-limited two-photon photoluminescence (TPL) scanning microscopy, reveal very selective polarization properties of excitation and TPL emission from the groove bottoms. 1D groove arrays in nickel were fabricated by making parallel 300 nm periodic adiabatic grooves of depths 100, 200, 300, 400 or 500 nm in a 600 nm thick nickel film. Their experimental characterization verifies that the structures are indeed very dark, exhibiting only 5-8% reflectivity over an entire wavelength range 400-1700 nm for the deepest grooves, which is in good correspondence with simulations.
Energy Science and Technology Software Center (ESTSC)
2007-07-20
This software distribution contains MATLAB and C++ code to enable identity verification using 3D images that may or may not contain a texture component. The code is organized to support system performance testing and system capability demonstration through the proper configuration of the available user interface. Using specific algorithm parameters the face recognition system has been demonstrated to achieve a 96.6% verification rate (Pd) at 0.001 false alarm rate. The system computes robust facial featuresmore » of a 3D normalized face using Principal Component Analysis (PCA) and Fisher Linear Discriminant Analysis (FLDA). A 3D normalized face is obtained by alighning each face, represented by a set of XYZ coordinated, to a scaled reference face using the Iterative Closest Point (ICP) algorithm. The scaled reference face is then deformed to the input face using an iterative framework with parameters that control the deformed surface regulation an rate of deformation. A variety of options are available to control the information that is encoded by the PCA. Such options include the XYZ coordinates, the difference of each XYZ coordinates from the reference, the Z coordinate, the intensity/texture values, etc. In addition to PCA/FLDA feature projection this software supports feature matching to obtain similarity matrices for performance analysis. In addition, this software supports visualization of the STL, MRD, 2D normalized, and PCA synthetic representations in a 3D environment.« less
Russ, Trina; Koch, Mark; Koudelka, Melissa; Peters, Ralph; Little, Charles; Boehnen, Chris; Peters, Tanya
2007-07-20
This software distribution contains MATLAB and C++ code to enable identity verification using 3D images that may or may not contain a texture component. The code is organized to support system performance testing and system capability demonstration through the proper configuration of the available user interface. Using specific algorithm parameters the face recognition system has been demonstrated to achieve a 96.6% verification rate (Pd) at 0.001 false alarm rate. The system computes robust facial features of a 3D normalized face using Principal Component Analysis (PCA) and Fisher Linear Discriminant Analysis (FLDA). A 3D normalized face is obtained by alighning each face, represented by a set of XYZ coordinated, to a scaled reference face using the Iterative Closest Point (ICP) algorithm. The scaled reference face is then deformed to the input face using an iterative framework with parameters that control the deformed surface regulation an rate of deformation. A variety of options are available to control the information that is encoded by the PCA. Such options include the XYZ coordinates, the difference of each XYZ coordinates from the reference, the Z coordinate, the intensity/texture values, etc. In addition to PCA/FLDA feature projection this software supports feature matching to obtain similarity matrices for performance analysis. In addition, this software supports visualization of the STL, MRD, 2D normalized, and PCA synthetic representations in a 3D environment.
On the convexity of ROC curves estimated from radiological test results
Pesce, Lorenzo L.; Metz, Charles E.; Berbaum, Kevin S.
2010-01-01
Rationale and Objectives Although an ideal observer’s receiver operating characteristic (ROC) curve must be convex — i.e., its slope must decrease monotonically — published fits to empirical data often display “hooks.” Such fits sometimes are accepted on the basis of an argument that experiments are done with real, rather than ideal, observers. However, the fact that ideal observers must produce convex curves does not imply that convex curves describe only ideal observers. This paper aims to identify the practical implications of non-convex ROC curves and the conditions that can lead to empirical and/or fitted ROC curves that are not convex. Materials and Methods This paper views non-convex ROC curves from historical, theoretical and statistical perspectives, which we describe briefly. We then consider population ROC curves with various shapes and analyze the types of medical decisions that they imply. Finally, we describe how sampling variability and curve-fitting algorithms can produce ROC curve estimates that include hooks. Results We show that hooks in population ROC curves imply the use of an irrational decision strategy, even when the curve doesn’t cross the chance line, and therefore usually are untenable in medical settings. Moreover, we sketch a simple approach to improve any non-convex ROC curve by adding statistical variation to the decision process. Finally, we sketch how to test whether hooks present in ROC data are likely to have been caused by chance alone and how some hooked ROCs found in the literature can be easily explained as fitting artifacts or modeling issues. Conclusion In general, ROC curve fits that show hooks should be looked upon with suspicion unless other arguments justify their presence. PMID:20599155
Pinhole Viewing Strengthens the Hollow-Face Illusion
Koessler, Trent
2015-01-01
A hollow (concave) mask appears convex when viewed from beyond a certain distance even when viewed stereoscopically—this is the hollow-face illusion. At close viewing distances, the same mask is seen as hollow even when disparity information is eliminated by monocular viewing. A potential source of nonpictorial, monocular information that favors a veridical percept at close distances is accommodation in conjunction with focus blur. In this article, we used pinhole viewing to minimize this potential source of information and test whether it affects whether a hollow mask is seen as veridical (concave) or illusory (convex). Since monocular viewing also facilitates the illusory (convex) percept, it was included in the design both as a comparison and to test whether any effect of accommodation depends on vergence. Pinhole viewing was found favor the illusory percept, and its effect was at least as large as, and added to, that of monocular viewing. A control experiment using tinted glasses that attenuate illumination at least as much as the pinholes did not strengthen the illusion ruling out explanations in terms of reduced luminance. For pinhole viewing, there was no difference between monocular and binocular conditions. The results are interpreted as evidence that focus driven depth information affects perceived three-dimensional shape at close distances even when other sources of depth information are available. The lack of a difference between monocular and binocular pinhole viewing suggests that, by disrupting accommodation, pinholes may also interfere with linked vergence cues to depth. PMID:27433315
Pinhole Viewing Strengthens the Hollow-Face Illusion.
Koessler, Trent; Hill, Harold
2015-08-01
A hollow (concave) mask appears convex when viewed from beyond a certain distance even when viewed stereoscopically-this is the hollow-face illusion. At close viewing distances, the same mask is seen as hollow even when disparity information is eliminated by monocular viewing. A potential source of nonpictorial, monocular information that favors a veridical percept at close distances is accommodation in conjunction with focus blur. In this article, we used pinhole viewing to minimize this potential source of information and test whether it affects whether a hollow mask is seen as veridical (concave) or illusory (convex). Since monocular viewing also facilitates the illusory (convex) percept, it was included in the design both as a comparison and to test whether any effect of accommodation depends on vergence. Pinhole viewing was found favor the illusory percept, and its effect was at least as large as, and added to, that of monocular viewing. A control experiment using tinted glasses that attenuate illumination at least as much as the pinholes did not strengthen the illusion ruling out explanations in terms of reduced luminance. For pinhole viewing, there was no difference between monocular and binocular conditions. The results are interpreted as evidence that focus driven depth information affects perceived three-dimensional shape at close distances even when other sources of depth information are available. The lack of a difference between monocular and binocular pinhole viewing suggests that, by disrupting accommodation, pinholes may also interfere with linked vergence cues to depth. PMID:27433315
Facing facts: neuronal mechanisms of face perception.
Dekowska, Monika; Kuniecki, Michał; Jaśkowski, Piotr
2008-01-01
The face is one of the most important stimuli carrying social meaning. Thanks to the fast analysis of faces, we are able to judge physical attractiveness and features of their owners' personality, intentions, and mood. From one's facial expression we can gain information about danger present in the environment. It is obvious that the ability to process efficiently one's face is crucial for survival. Therefore, it seems natural that in the human brain there exist structures specialized for face processing. In this article, we present recent findings from studies on the neuronal mechanisms of face perception and recognition in the light of current theoretical models. Results from brain imaging (fMRI, PET) and electrophysiology (ERP, MEG) show that in face perception particular regions (i.e. FFA, STS, IOA, AMTG, prefrontal and orbitofrontal cortex) are involved. These results are confirmed by behavioral data and clinical observations as well as by animal studies. The developmental findings reviewed in this article lead us to suppose that the ability to analyze face-like stimuli is hard-wired and improves during development. Still, experience with faces is not sufficient for an individual to become an expert in face perception. This thesis is supported by the investigation of individuals with developmental disabilities, especially with autistic spectrum disorders (ASD). PMID:18511959
ERIC Educational Resources Information Center
Langton, Stephen R. H.; Law, Anna S.; Burton, A. Mike; Schweinberger, Stefan R.
2008-01-01
We report three experiments that investigate whether faces are capable of capturing attention when in competition with other non-face objects. In Experiment 1a participants took longer to decide that an array of objects contained a butterfly target when a face appeared as one of the distracting items than when the face did not appear in the array.…
NASA Astrophysics Data System (ADS)
Jafarpur, Khosrow
An analytical and experimental study of laminar free convection from bodies of arbitrary convex shape is performed to determine the effect of shape, aspect ratio, and orientation of isothermal bodies on the area-averaged Nusselt number over a wide range of Rayleigh and Prandtl numbers. Also, a simple procedure is provided for predicting laminar free convection heat transfer from bodies of arbitrary convex shape, based upon a characteristic length using the square root of the total body surface area, square root of A. To examine the theoretical basis for the Nu-Ra expressions, a new simple, but accurate, approximate analytical method is developed. The proposed method is novel in: linearizing the convective terms, reducing a convective problem to a simpler transient conduction problem for which a solution may exist, and also obtaining an explicit expression for an 'effective velocity' in free convection boundary layer flow, as a function of the Prandtl number. The end result of this method is an explicit expression in terms of a simple superposition of two limits: diffusive limit and laminar boundary layer solution. To predict the laminar boundary layer limit, information regarding the dependency on Prandtl number and the body gravity function is required. By providing different exact and approximate methods, such as the same characteristic lengths and aspect ratios method or the inscribing and circumscribing method (the bounds method), the two asymptotes can be determined for any given shape. This includes body shapes such as the so-called two-dimensional bodies, disks, bodies of small aspect ratios and vertical cylinders of different aspect ratios. In the experimental program, through a transient cooling process and pressure variation technique, the measurement of heat transfer by free convection from isothermal bodies to air is conducted. Due to the nature of the experimental technique adopted and the need for the heat capacity, in a separate and single test at
On the complexity of a combined homotopy interior method for convex programming
NASA Astrophysics Data System (ADS)
Yu, Bo; Xu, Qing; Feng, Guochen
2007-03-01
In [G.C. Feng, Z.H. Lin, B. Yu, Existence of an interior pathway to a Karush-Kuhn-Tucker point of a nonconvex programming problem, Nonlinear Anal. 32 (1998) 761-768; G.C. Feng, B. Yu, Combined homotopy interior point method for nonlinear programming problems, in: H. Fujita, M. Yamaguti (Eds.), Advances in Numerical Mathematics, Proceedings of the Second Japan-China Seminar on Numerical Mathematics, Lecture Notes in Numerical and Applied Analysis, vol. 14, Kinokuniya, Tokyo, 1995, pp. 9-16; Z.H. Lin, B. Yu, G.C. Feng, A combined homotopy interior point method for convex programming problem, Appl. Math. Comput. 84 (1997) 193-211.], a combined homotopy was constructed for solving non-convex programming and convex programming with weaker conditions, without assuming the logarithmic barrier function to be strictly convex and the solution set to be bounded. It was proven that a smooth interior path from an interior point of the feasible set to a K-K-T point of the problem exists. This shows that combined homotopy interior point methods can solve the problem that commonly used interior point methods cannot solveE However, so far, there is no result on its complexity, even for linear programming. The main difficulty is that the objective function is not monotonically decreasing on the combined homotopy path. In this paper, by taking a piecewise technique, under commonly used conditions, polynomiality of a combined homotopy interior point method is given for convex nonlinear programming.
Image deconvolution with multi-stage convex relaxation and its perceptual evaluation.
Hou, Tingbo; Wang, Sen; Qin, Hong
2011-12-01
This paper proposes a new image deconvolution method using multi-stage convex relaxation, and presents a metric for perceptual evaluation of deconvolution results. Recent work in image deconvolution addresses the deconvolution problem via minimization with non-convex regularization. Since all regularization terms in the objective function are non-convex, this problem can be well modeled and solved by multi-stage convex relaxation. This method, adopted from machine learning, iteratively refines the convex relaxation formulation using concave duality. The newly proposed deconvolution method has outstanding performance in noise removal and artifact control. A new metric, transduced contrast-to-distortion ratio (TCDR), is proposed based on a human vision system (HVS) model that simulates human responses to visual contrasts. It is sensitive to ringing and boundary artifacts, and very efficient to compute. We conduct comprehensive perceptual evaluation of image deconvolution using visual signal-to-noise ratio (VSNR) and TCDR. Experimental results of both synthetic and real data demonstrate that our method indeed improves the visual quality of deconvolution results with low distortions and artifacts. PMID:21550886
Faciotopy-A face-feature map with face-like topology in the human occipital face area.
Henriksson, Linda; Mur, Marieke; Kriegeskorte, Nikolaus
2015-11-01
The occipital face area (OFA) and fusiform face area (FFA) are brain regions thought to be specialized for face perception. However, their intrinsic functional organization and status as cortical areas with well-defined boundaries remains unclear. Here we test these regions for "faciotopy", a particular hypothesis about their intrinsic functional organisation. A faciotopic area would contain a face-feature map on the cortical surface, where cortical patches represent face features and neighbouring patches represent features that are physically neighbouring in a face. The faciotopy hypothesis is motivated by the idea that face regions might develop from a retinotopic protomap and acquire their selectivity for face features through natural visual experience. Faces have a prototypical configuration of features, are usually perceived in a canonical upright orientation, and are frequently fixated in particular locations. To test the faciotopy hypothesis, we presented images of isolated face features at fixation to subjects during functional magnetic resonance imaging. The responses in V1 were best explained by low-level image properties of the stimuli. OFA, and to a lesser degree FFA, showed evidence for faciotopic organization. When a single patch of cortex was estimated for each face feature, the cortical distances between the feature patches reflected the physical distance between the features in a face. Faciotopy would be the first example, to our knowledge, of a cortical map reflecting the topology, not of a part of the organism itself (its retina in retinotopy, its body in somatotopy), but of an external object of particular perceptual significance. PMID:26235800
Matsuda, Yoshi-Taka; Myowa-Yamakoshi, Masako; Hirata, Satoshi
2016-01-01
Highly social animals possess a well-developed ability to distinguish the faces of familiar from novel conspecifics to induce distinct behaviors for maintaining society. However, the behaviors of animals when they encounter ambiguous faces of familiar yet novel conspecifics, e.g., strangers with faces resembling known individuals, have not been well characterised. Using a morphing technique and preferential-looking paradigm, we address this question via the chimpanzee's facial-recognition abilities. We presented eight subjects with three types of stimuli: (1) familiar faces, (2) novel faces and (3) intermediate morphed faces that were 50% familiar and 50% novel faces of conspecifics. We found that chimpanzees spent more time looking at novel faces and scanned novel faces more extensively than familiar or intermediate faces. Interestingly, chimpanzees looked at intermediate faces in a manner similar to familiar faces with regards to the fixation duration, fixation count, and saccade length for facial scanning, even though the participant was encountering the intermediate faces for the first time. We excluded the possibility that subjects merely detected and avoided traces of morphing in the intermediate faces. These findings suggest a bias for a feeling-of-familiarity that chimpanzees perceive familiarity with an intermediate face by detecting traces of a known individual, as 50% alternation is sufficient to perceive familiarity. PMID:27602275
Myowa-Yamakoshi, Masako
2016-01-01
Highly social animals possess a well-developed ability to distinguish the faces of familiar from novel conspecifics to induce distinct behaviors for maintaining society. However, the behaviors of animals when they encounter ambiguous faces of familiar yet novel conspecifics, e.g., strangers with faces resembling known individuals, have not been well characterised. Using a morphing technique and preferential-looking paradigm, we address this question via the chimpanzee’s facial–recognition abilities. We presented eight subjects with three types of stimuli: (1) familiar faces, (2) novel faces and (3) intermediate morphed faces that were 50% familiar and 50% novel faces of conspecifics. We found that chimpanzees spent more time looking at novel faces and scanned novel faces more extensively than familiar or intermediate faces. Interestingly, chimpanzees looked at intermediate faces in a manner similar to familiar faces with regards to the fixation duration, fixation count, and saccade length for facial scanning, even though the participant was encountering the intermediate faces for the first time. We excluded the possibility that subjects merely detected and avoided traces of morphing in the intermediate faces. These findings suggest a bias for a feeling-of-familiarity that chimpanzees perceive familiarity with an intermediate face by detecting traces of a known individual, as 50% alternation is sufficient to perceive familiarity. PMID:27602275
Programmed versus Face-to-Face Counseling
ERIC Educational Resources Information Center
Gilbert, William M.; Ewing, Thomas N.
1971-01-01
A comparison was made of the effectiveness of a programmed Self-Counseling Manual and a normal precollege counseling interview by experienced counselors. Findings supported the use of programmed counseling as an adjunct to or substitute for face-to-face counseling. (Author)
A Shape-Based Account for Holistic Face Processing
ERIC Educational Resources Information Center
Zhao, Mintao; Bülthoff, Heinrich H.; Bülthoff, Isabelle
2016-01-01
Faces are processed holistically, so selective attention to 1 face part without any influence of the others often fails. In this study, 3 experiments investigated what type of facial information (shape or surface) underlies holistic face processing and whether generalization of holistic processing to nonexperienced faces requires extensive…
Improving the accuracy of convexity splitting methods for gradient flow equations
NASA Astrophysics Data System (ADS)
Glasner, Karl; Orizaga, Saulo
2016-06-01
This paper introduces numerical time discretization methods which significantly improve the accuracy of the convexity-splitting approach of Eyre (1998) [7], while retaining the same numerical cost and stability properties. A first order method is constructed by iteration of a semi-implicit method based upon decomposing the energy into convex and concave parts. A second order method is also presented based on backwards differentiation formulas. Several extrapolation procedures for iteration initialization are proposed. We show that, under broad circumstances, these methods have an energy decreasing property, leading to good numerical stability. The new schemes are tested using two evolution equations commonly used in materials science: the Cahn-Hilliard equation and the phase field crystal equation. We find that our methods can increase accuracy by many orders of magnitude in comparison to the original convexity-splitting algorithm. In addition, the optimal methods require little or no iteration, making their computation cost similar to the original algorithm.
The role of convexity for solving some shortest path problems in plane without triangulation
NASA Astrophysics Data System (ADS)
An, Phan Thanh; Hai, Nguyen Ngoc; Hoai, Tran Van
2013-09-01
Solving shortest path problems inside simple polygons is a very classical problem in motion planning. To date, it has usually relied on triangulation of the polygons. The question: "Can one devise a simple O(n) time algorithm for computing the shortest path between two points in a simple polygon (with n vertices), without resorting to a (complicated) linear-time triangulation algorithm?" raised by J. S. B. Mitchell in Handbook of Computational Geometry (J. Sack and J. Urrutia, eds., Elsevier Science B.V., 2000), is still open. The aim of this paper is to show that convexity contributes to the design of efficient algorithms for solving some versions of shortest path problems (namely, computing the convex hull of a finite set of points and convex rope on rays in 2D, computing approximate shortest path between two points inside a simple polygon) without triangulation on the entire polygons. New algorithms are implemented in C and numerical examples are presented.
Phase and TV Based Convex Sets for Blind Deconvolution of Microscopic Images
NASA Astrophysics Data System (ADS)
Tofighi, Mohammad; Yorulmaz, Onur; Kose, Kivanc; Yildirim, Deniz Cansen; Cetin-Atalay, Rengul; Cetin, A. Enis
2016-02-01
In this article, two closed and convex sets for blind deconvolution problem are proposed. Most blurring functions in microscopy are symmetric with respect to the origin. Therefore, they do not modify the phase of the Fourier transform (FT) of the original image. As a result blurred image and the original image have the same FT phase. Therefore, the set of images with a prescribed FT phase can be used as a constraint set in blind deconvolution problems. Another convex set that can be used during the image reconstruction process is the epigraph set of Total Variation (TV) function. This set does not need a prescribed upper bound on the total variation of the image. The upper bound is automatically adjusted according to the current image of the restoration process. Both of these two closed and convex sets can be used as a part of any blind deconvolution algorithm. Simulation examples are presented.
Lp stability for entropy solutions of scalar conservation laws with strict convex flux
NASA Astrophysics Data System (ADS)
Adimurthi; Ghoshal, Shyam Sundar; Veerappa Gowda, G. D.
Here we consider the scalar convex conservation laws in one space dimension with strictly convex flux which is in C1. Existence, uniqueness and L1 contractivity were proved by Kružkov [14]. Using the relative entropy method, Leger showed that for a uniformly convex flux and for the shock wave solutions, the L2 norm of a perturbed solution relative to the shock wave is bounded by the L2 norm of the initial perturbation. Here we generalize the result to Lp norm for all 1⩽p<∞. Also we show that for the non-shock wave solution, Lp norm of the perturbed solution relative to the modified N-wave is bounded by the Lp norm of the initial perturbation for all 1⩽p<∞.
Digital breast tomosynthesis reconstruction using spatially weighted non-convex regularization
NASA Astrophysics Data System (ADS)
Zheng, Jiabei; Fessler, Jeffrey A.; Chan, Heang-Ping
2016-03-01
Regularization is an effective strategy for reducing noise in tomographic reconstruction. This paper proposes a spatially weighted non-convex (SWNC) regularization method for digital breast tomosynthesis (DBT) image reconstruction. With a non-convex cost function, this method can suppress noise without blurring microcalcifications (MC) and spiculations of masses. To minimize the non-convex cost function, we apply a majorize-minimize separable quadratic surrogate algorithm (MM-SQS) that is further accelerated by ordered subsets (OS). We applied the new method to a heterogeneous breast phantom and to human subject DBT data, and observed improved image quality in both situations. A quantitative study also showed that the SWNC method can significantly enhance the contrast-to-noise ratio of MCs. By properly selecting its parameters, the SWNC regularizer can preserve the appearance of the mass margins and breast parenchyma.
NASA Astrophysics Data System (ADS)
Geletu, Abebe; Klöppel, Michael; Hoffmann, Armin; Li, Pu
2015-04-01
Chance constrained optimization problems in engineering applications possess highly nonlinear process models and non-convex structures. As a result, solving a nonlinear non-convex chance constrained optimization (CCOPT) problem remains as a challenging task. The major difficulty lies in the evaluation of probability values and gradients of inequality constraints which are nonlinear functions of stochastic variables. This article proposes a novel analytic approximation to improve the tractability of smooth non-convex chance constraints. The approximation uses a smooth parametric function to define a sequence of smooth nonlinear programs (NLPs). The sequence of optimal solutions of these NLPs remains always feasible and converges to the solution set of the CCOPT problem. Furthermore, Karush-Kuhn-Tucker (KKT) points of the approximating problems converge to a subset of KKT points of the CCOPT problem. Another feature of this approach is that it can handle uncertainties with both Gaussian and/or non-Gaussian distributions.
Tsao, Doris Y.
2009-01-01
Faces are among the most informative stimuli we ever perceive: Even a split-second glimpse of a person's face tells us their identity, sex, mood, age, race, and direction of attention. The specialness of face processing is acknowledged in the artificial vision community, where contests for face recognition algorithms abound. Neurological evidence strongly implicates a dedicated machinery for face processing in the human brain, to explain the double dissociability of face and object recognition deficits. Furthermore, it has recently become clear that macaques too have specialized neural machinery for processing faces. Here we propose a unifying hypothesis, deduced from computational, neurological, fMRI, and single-unit experiments: that what makes face processing special is that it is gated by an obligatory detection process. We will clarify this idea in concrete algorithmic terms, and show how it can explain a variety of phenomena associated with face processing. PMID:18558862
Description and recognition of faces from 3D data
NASA Astrophysics Data System (ADS)
Coombes, Anne M.; Richards, Robin; Linney, Alfred D.; Bruce, Vicki; Fright, Rick
1992-12-01
A method based on differential geometry, is presented for mathematically describing the shape of the facial surface. Three-dimensional data for the face are collected by optical surface scanning. The method allows the segmentation of the face into regions of a particular `surface type,' according to the surface curvature. Eight different surface types are produced which all have perceptually meaningful interpretations. The correspondence of the surface type regions to the facial features are easily visualized, allowing a qualitative assessment of the face. A quantitative description of the face in terms of the surface type regions can be produced and the variation of the description between faces is demonstrated. A set of optical surface scans can be registered together and averages to produce an average male and average female face. Thus an assessment of how individuals vary from the average can be made as well as a general statement about the differences between male and female faces. This method will enable an investigation to be made as to how reliably faces can be individuated by their surface shape which, if feasible, may be the basis of an automatic system for recognizing faces. It also has applications in physical anthropology, for classification of the face, facial reconstructive surgery, to quantify the changes in a face altered by reconstructive surgery and growth, and in visual perception, to assess the recognizability of faces. Examples of some of these applications are presented.
Strictly ordered minimal subsets of a class of convex monotone skew-product semiflows
NASA Astrophysics Data System (ADS)
Novo, Sylvia; Obaya, Rafael
We study the topological and ergodic structure of a class of convex and monotone skew-product semiflows. We assume the existence of two strongly ordered minimal subsets K 1, K 2 and we obtain an ergodic representation of their upper Lyapunov exponents. In the case of null upper Lyapunov exponents, we obtain a lamination into minimal subsets of an intermediate region where the restriction of the semiflow is affine. In the hyperbolic case, we deduce the long-time behaviour of every trajectory ordered with K2. Some examples of skew-product semiflows generated by non-autonomous differential equations and satisfying the assumptions of monotonicity and convexity are also presented.
Attractor minimal sets for cooperative and strongly convex delay differential systems
NASA Astrophysics Data System (ADS)
Novo, Sylvia; Obaya, Rafael; Sanz, Ana M.
We study the skew-product semiflow induced by a family of convex and cooperative delay differential systems. Under some monotonicity assumptions, we obtain an ergodic representation for the upper Lyapunov exponent of a minimal subset. In addition, when eventually strong convexity at one point is assumed and there exist two completely strongly ordered minimal subsets K1≪ CK2, we show that K1 is an attractor subset which is a copy of the base. The long-time behaviour of every trajectory strongly ordered with K2 is then deduced. Some examples of application of the theory are shown.
Tuning magnetic anisotropy of amorphous CoFeB film by depositing on convex flexible substrates
NASA Astrophysics Data System (ADS)
Qiao, Xinyu; Wang, Baomin; Tang, Zhenhua; Shen, Yuan; Yang, Huali; Wang, Junling; Zhan, Qingfeng; Mao, Sining; Xu, Xiaohong; Li, Run-Wei
2016-05-01
We have investigated the magnetic properties of amorphous Co40Fe40B20 (CoFeB) thin films grown on flexible polyimide (PI) substrates, which were fixed on convex molds with different curvatures during the magnetron sputtering deposition. When the flexible substrates were changed from convex to flat state after fabrication, a uniaxial magnetic anisotropy was induced in the CoFeB film due to magnetostrictive effect. Furthermore, the anisotropy also depends on the thicknesses of the film and substrate. Our results demonstrate a convenient method to tune the anisotropy of magnetic thin films grown on flexible substrates.
A Modified BFGS Formula Using a Trust Region Model for Nonsmooth Convex Minimizations
Cui, Zengru; Yuan, Gonglin; Sheng, Zhou; Liu, Wenjie; Wang, Xiaoliang; Duan, Xiabin
2015-01-01
This paper proposes a modified BFGS formula using a trust region model for solving nonsmooth convex minimizations by using the Moreau-Yosida regularization (smoothing) approach and a new secant equation with a BFGS update formula. Our algorithm uses the function value information and gradient value information to compute the Hessian. The Hessian matrix is updated by the BFGS formula rather than using second-order information of the function, thus decreasing the workload and time involved in the computation. Under suitable conditions, the algorithm converges globally to an optimal solution. Numerical results show that this algorithm can successfully solve nonsmooth unconstrained convex problems. PMID:26501775
The Compressible Stokes Flows with No-Slip Boundary Condition on Non-Convex Polygons
NASA Astrophysics Data System (ADS)
Kweon, Jae Ryong
2016-05-01
In this paper we study the compressible Stokes equations with no-slip boundary condition on non-convex polygons and show a best regularity result that the solution can have without subtracting corner singularities. This is obtained by a suitable Helmholtz decomposition: {{{u}}={{w}}+nablaφ_R} with divw = 0 and a potential {φ_R} . Here w is the solution for the incompressible Stokes problem and {φ_R} is defined by subtracting from the solution of the Neumann problem the leading two corner singularities at non-convex vertices.
... this page: //medlineplus.gov/ency/article/002700.htm Face powder poisoning To use the sharing features on this page, please enable JavaScript. Face powder poisoning occurs when someone swallows or breathes ...
Face powder poisoning occurs when someone swallows or breathes in this substance. This article is for information ... The ingredients in face powder that can be harmful are: Baking soda Talcum powder Many other types of powder
Sugita, Yoichi
2009-02-01
Recent monkey studies provide intriguing information for an open question whether face processing is a special perceptual process and is organized as such at birth, or has its origin in a more general system that becomes specialized with experience. Before seeing any faces or face-like objects, macaque monkeys showed a preference for faces rather than nonface objects. Furthermore, they showed remarkable face processing abilities both for human and monkey faces. It was also shown that macaque newborns are able to imitate human facial gestures, indicating the ability to match their own facial movements to observed facial gestures. Taken together, it seems very likely that newborns can acquire the knowledge about the basic structure of their own face, presumably through proprioception, so that facial structure would become a familiar and attractive visual object without the experience of the face itself. PMID:19339171
... About Blog Facing Disability Jeff Shannon Donate A Spinal Cord Injury Affects the Entire Family FacingDisability was specifically created ... and insights on spinal cord injury issues Interactive Spinal Cord Injury Map Shows what areas are affected by spinal ...
49 CFR 236.745 - Face, locking.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 49 Transportation 4 2012-10-01 2012-10-01 false Face, locking. 236.745 Section 236.745 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Face, locking. The locking surface of a locking dog, tappet or cross locking of an interlocking machine....
49 CFR 236.745 - Face, locking.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 49 Transportation 4 2014-10-01 2014-10-01 false Face, locking. 236.745 Section 236.745 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Face, locking. The locking surface of a locking dog, tappet or cross locking of an interlocking machine....
49 CFR 236.745 - Face, locking.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 49 Transportation 4 2011-10-01 2011-10-01 false Face, locking. 236.745 Section 236.745 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Face, locking. The locking surface of a locking dog, tappet or cross locking of an interlocking machine....
49 CFR 236.745 - Face, locking.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 49 Transportation 4 2013-10-01 2013-10-01 false Face, locking. 236.745 Section 236.745 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Face, locking. The locking surface of a locking dog, tappet or cross locking of an interlocking machine....
Are face representations depth cue invariant?
Dehmoobadsharifabadi, Armita; Farivar, Reza
2016-06-01
The visual system can process three-dimensional depth cues defining surfaces of objects, but it is unclear whether such information contributes to complex object recognition, including face recognition. The processing of different depth cues involves both dorsal and ventral visual pathways. We investigated whether facial surfaces defined by individual depth cues resulted in meaningful face representations-representations that maintain the relationship between the population of faces as defined in a multidimensional face space. We measured face identity aftereffects for facial surfaces defined by individual depth cues (Experiments 1 and 2) and tested whether the aftereffect transfers across depth cues (Experiments 3 and 4). Facial surfaces and their morphs to the average face were defined purely by one of shading, texture, motion, or binocular disparity. We obtained identification thresholds for matched (matched identity between adapting and test stimuli), non-matched (non-matched identity between adapting and test stimuli), and no-adaptation (showing only the test stimuli) conditions for each cue and across different depth cues. We found robust face identity aftereffect in both experiments. Our results suggest that depth cues do contribute to forming meaningful face representations that are depth cue invariant. Depth cue invariance would require integration of information across different areas and different pathways for object recognition, and this in turn has important implications for cortical models of visual object recognition. PMID:27271993
Face to Face Communications in Space
NASA Technical Reports Server (NTRS)
Cohen, Malcolm M.; Davon, Bonnie P. (Technical Monitor)
1999-01-01
It has been reported that human face-to-face communications in space are compromised by facial edema, variations in the orientations of speakers and listeners, and background noises that are encountered in the shuttle and in space stations. To date, nearly all reports have been anecdotal or subjective, in the form of post-flight interviews or questionnaires; objective and quantitative data are generally lacking. Although it is acknowledged that efficient face-to-face communications are essential for astronauts to work safely and effectively, specific ways in which the space environment interferes with non-linguistic communication cues are poorly documented. Because we have only a partial understanding of how non-linguistic communication cues may change with mission duration, it is critically important to obtain objective data, and to evaluate these cues under well-controlled experimental conditions.
Dynamic region-of-interest acquisition and face tracking for intelligent surveillance system
NASA Astrophysics Data System (ADS)
Kim, Young-Ouk; Kim, Sangjin; Park, Chang-Woo; Sung, Ha-Gyeong; Paik, Joonki
2004-05-01
Recently, surveillance systems gain more attraction than simple CCTV systems, especially for complicated security environment. The major purpose of the proposed system is to monitor and track intruders. More specifically, accurate identification of each intruder is more important than simply recording what they are doing. Most existing surveillance systems simply keep recording the fixed viewing area, and some others adopt the tracking technique for wider coverage. Although panning and tilting the camera can extend the viewing area, only a few automatic zoom control techniques for acquiring the optimum ROI has been proposed. This paper describes a system for tracking multiple faces from input video sequences using facial convex hull-based facial segmentation and robust hausdorff distance. The proposed algorithm adapts skin color reference map in the YCbCr color space and hair color reference map in the RGB color space for classifying face region. Then, we obtain an initial face model with preprocessing and convex hull. For tracking, this algorithm computes displacement of the point set between frames using a robust hausdorff distance and the best possible displacement is selected. Finally, the initial face model is updated using the displacement. We provide experimental result to demonstrate the performance of the proposed tracking algorithm, which efficiently tracks rotating, and zooming faces as well as multiple faces in video sequences obtained from at CCD camera.
The analytics of the limitation of collimating ability for asymmetric bi-convex lenses
NASA Astrophysics Data System (ADS)
Shi, Yong; Shao, Zhongxing
2005-01-01
Laser diode (LD) are playing more and more important role in a number of technical areas. However, due to LD's bad beam divergence, researchers have to use sophisticate optical systems to collimate or focus LD into other appliance. It is necessary to collimate laser diode. Whereas if the object is not ideal but with a limited dimension, no matter how to correct the radius, some aberrations may always remain. That is the collimation has a limitation. In this paper, we investigate the limitation for the asymmetric bi-convex lenses by ray tracing method with the help of Femat theory. And obtain the equations which analyze the limitation of the asymmetric bi-convex lenses. By programming the equations, we calculated and the limitation as a function of LD's beam dimension, index and the two radii of curvature of the asymmetric bi-convex lenses respectively. Keeping other conditions invariably and changing LD's beam dimension from 5mm to 150mm with a step of 5mm, we find that the limitation increases approximatively linearly with the increase of the beam dimension. Basing on the results of the calculation, we analyzed and plotted the limitation as a function of index and radii of curvature of the asymmetric bi-convex lenses in detail.
Stable anisotropic plasma confinement in magnetic configurations with convex-concave field lines
NASA Astrophysics Data System (ADS)
Tsventoukh, M. M.
2014-02-01
It is shown that a combination of the convex and the concave part of a field line provides a strong stabilizing action against convective (flute-interchange) plasma instability (Tsventoukh 2011 Nucl. Fusion 51 112002). This results in internal peaking of the stable plasma pressure profile that is calculated from the collisionless kinetic stability criterion for any magnetic confinement system with combination of mirrors and cusps. Connection of the convex and concave field line parts results in a reduction of the space charge that drives the unstable E × B motion, as there is an opposite direction of the particle drift in a non-uniform field at convex and concave field lines. The pressure peaking arises at the minimum of the second adiabatic invariant J that takes place at the ‘middle’ of a tandem mirror-cusp transverse cross-section. The position of the minimum in J varies with the particle pitch angle that results in a shift of the peaking position depending on plasma anisotropy. This allows one to improve a stable peaked pressure profile at a convex-concave field by changing the plasma anisotropy over the trap cross-section. Examples of such anisotropic distribution functions are found that give an additional substantial enhancement in the maximal central pressure. Furthermore, the shape of new calculated stable profiles has a wide central plasma layer instead of a narrow peak.
A fast finite volume method for conservative space-fractional diffusion equations in convex domains
NASA Astrophysics Data System (ADS)
Jia, Jinhong; Wang, Hong
2016-04-01
We develop a fast finite volume method for variable-coefficient, conservative space-fractional diffusion equations in convex domains via a volume-penalization approach. The method has an optimal storage and an almost linear computational complexity. The method retains second-order accuracy without requiring a Richardson extrapolation. Numerical results are presented to show the utility of the method.
Comparison of Fuzzy Set and Convex Model Theories in Structural Design
NASA Astrophysics Data System (ADS)
Pantelides, Chris P.; Ganzerli, Sara
2001-05-01
A methodology for the treatment of uncertainty in the loads applied to a structural system using convex models is presented and is compared to the fuzzy set finite-element method. The analytical results for a beam, a truss and a frame structure indicate that the two methods based on convex model or fuzzy set theory are in good agreement for equivalent levels of uncertainty applied to linear structures. Convex model or fuzzy set theories have shown that the worst-case scenario response of all possible load combinations cannot be captured simply by load factorisation, as is the current design practice in building codes. Design problems including uncertainty with a large number of degrees of freedom, that are not computationally feasible using conventional methods described in building codes, can be solved easily using convex model or fuzzy set theory. These results can be used directly and efficiently in the analyses required for the optimal design of structural systems, thus enabling optimisation of complex structural systems with uncertainty.
Convexity of Energy-Like Functions: Theoretical Results and Applications to Power System Operations
Dvijotham, Krishnamurthy; Chertkov, Michael; Low, Steven
2015-01-22
Power systems are undergoing unprecedented transformations with increased adoption of renewables and distributed generation, as well as the adoption of demand response programs. All of these changes, while making the grid more responsive and potentially more efficient, pose significant challenges for power systems operators. Conventional operational paradigms are no longer sufficient as the power system may no longer have big dispatchable generators with sufficient positive and negative reserves. This increases the need for tools and algorithms that can efficiently predict safe regions of operation of the power system. In this paper, we study energy functions as a tool to design algorithms for various operational problems in power systems. These have a long history in power systems and have been primarily applied to transient stability problems. In this paper, we take a new look at power systems, focusing on an aspect that has previously received little attention: Convexity. We characterize the domain of voltage magnitudes and phases within which the energy function is convex in these variables. We show that this corresponds naturally with standard operational constraints imposed in power systems. We show that power of equations can be solved using this approach, as long as the solution lies within the convexity domain. We outline various desirable properties of solutions in the convexity domain and present simple numerical illustrations supporting our results.
BV-Regularity of the Boltzmann Equation in Non-Convex Domains
NASA Astrophysics Data System (ADS)
Guo, Y.; Kim, C.; Tonon, D.; Trescases, A.
2016-06-01
We consider the Boltzmann equation in a general non-convex domain with the diffuse boundary condition. We establish optimal BV estimates for such solutions. Our method consists of a new W 1,1-trace estimate for the diffuse boundary condition and a delicate construction of an {\\varepsilon}-tubular neighborhood of the singular set.
Higher order sensitivity of solutions to convex programming problems without strict complementarity
NASA Technical Reports Server (NTRS)
Malanowski, Kazimierz
1988-01-01
Consideration is given to a family of convex programming problems which depend on a vector parameter. It is shown that the solutions of the problems and the associated Lagrange multipliers are arbitrarily many times directionally differentiable functions of the parameter, provided that the data of the problems are sufficiently regular. The characterizations of the respective derivatives are given.
A Diagrammatic Proof That Indirect Utility Functions Are Quasi-Convex.
ERIC Educational Resources Information Center
Suen, Wing
1992-01-01
Presents a diagrammatic proof for classroom use to demonstrate the quasi-convexity of the indirect utility function. Includes a variation of the price indifference curve. Suggests an exercise in which the student is asked to show that the tangency condition is a restatement of Roy's identity. (DK)
A near-optimal heuristic for minimum weight triangulation of convex polygons
Levcopoulos, C.; Krznaric, D.
1997-06-01
A linear-time heuristic for minimum weight triangulation of convex polygons is presented. This heuristic produces a triangulation of length within a factor 1 + {epsilon} from the optimum, where {epsilon} is an arbitrarily small positive constant. This is the first sub-cubic algorithm which guarantees such an approximation factor, and it has interesting applications.
Martínez-Lizana, Eva; Carmona-Iragui, María; Alcolea, Daniel; Gómez-Choco, Manuel; Vilaplana, Eduard; Sánchez-Saudinós, María B; Clarimón, Jordi; Hernández-Guillamon, Mar; Munuera, Josep; Gelpi, Ellen; Gómez-Anson, Beatriz; de Juan-Delago, Manel; Delgado-Mederos, Raquel; Montaner, Joan; Ois, Angel; Amaro, Sergi; Blesa, Rafael; Martí-Fàbregas, Joan; Lleó, Alberto; Fortea, Juan
2015-01-01
Atraumatic convexal subarachnoid hemorrhage (cSAH) in elderly patients is a rare entity that has been associated with cerebral amyloid angiopathy (CAA) and intracerebral hematomas (ICH). To characterize this entity and to study these associations, 22 patients over 60 with cSAH were included in a multicenter ambispective cohort study. Clinical data, magnetic resonance imaging (MRI) studies, APOE genotyping, and cerebrospinal fluid (CSF) biomarkers were evaluated. Results were compared with data from healthy controls (HC), non-cSAH CAA patients (CAAo), and Alzheimer disease patients. Convexal subarachnoid hemorrhage presented with transient sensory or motor symptoms. At follow-up (median 30.7 months), 5 patients had died, 6 survivors showed functional disability (modified Rankins Scale (mRS)>2), and 12 cognitive impairment. Four patients had prior ICH and six had an ICH during follow-up. CSF-Aß40 and Aß42 levels were lower in cSAH and CAAo compared with HC. Convexal subarachnoid hemorrhage presented an APOE-ɛ2 overrepresentation and CAAo had an APOE-ɛ4 overrepresentation. On MRI, all patients fulfilled CAA-modified Boston criteria and 9 showed cortical ischemia in the surrounding cortex or the vicinity of superficial siderosis. The neuropathologic study, available in one patient, showed severe CAA and advanced Alzheimer-type pathology. Convexal subarachnoid hemorrhage in the elderly is associated with cognitive impairment and lobar ICH occurrence. Our findings support the existence of an underlying CAA pathology. PMID:25735919
Modeling IrisCode and its variants as convex polyhedral cones and its security implications.
Kong, Adams Wai-Kin
2013-03-01
IrisCode, developed by Daugman, in 1993, is the most influential iris recognition algorithm. A thorough understanding of IrisCode is essential, because over 100 million persons have been enrolled by this algorithm and many biometric personal identification and template protection methods have been developed based on IrisCode. This paper indicates that a template produced by IrisCode or its variants is a convex polyhedral cone in a hyperspace. Its central ray, being a rough representation of the original biometric signal, can be computed by a simple algorithm, which can often be implemented in one Matlab command line. The central ray is an expected ray and also an optimal ray of an objective function on a group of distributions. This algorithm is derived from geometric properties of a convex polyhedral cone but does not rely on any prior knowledge (e.g., iris images). The experimental results show that biometric templates, including iris and palmprint templates, produced by different recognition methods can be matched through the central rays in their convex polyhedral cones and that templates protected by a method extended from IrisCode can be broken into. These experimental results indicate that, without a thorough security analysis, convex polyhedral cone templates cannot be assumed secure. Additionally, the simplicity of the algorithm implies that even junior hackers without knowledge of advanced image processing and biometric databases can still break into protected templates and reveal relationships among templates produced by different recognition methods. PMID:23193454
NASA Technical Reports Server (NTRS)
Sehnal, J.; Sedy, J.; Etsion, I.; Zobens, A.
1982-01-01
Torque, face temperature, leakage, and wear of a flat face seal were compared with three coned face seals at pressures up to 2758 kPa and speeds up to 8000 rpm. Axial movement of the mating seal parts was recorded by a digital data acquisition system. The coning of the tungsten carbide primary ring ranged from .51 micro-m to 5.6 micro-m. The torque of the coned face seal balanced to 76.3% was an average 42% lower, the leakage eleven times higher, than that of the standard flat face seal. The reduction of the balance of the coned face seal to 51.3% resulted by decreasing the torque by an additional 44% and increasing leakage 12 to 230 times, depending on the seal shaft speed. No measurable wear was observed on the face of the coned seals.
First-order convex feasibility algorithms for x-ray CT
Sidky, Emil Y.; Pan Xiaochuan; Jorgensen, Jakob S.
2013-03-15
Purpose: Iterative image reconstruction (IIR) algorithms in computed tomography (CT) are based on algorithms for solving a particular optimization problem. Design of the IIR algorithm, therefore, is aided by knowledge of the solution to the optimization problem on which it is based. Often times, however, it is impractical to achieve accurate solution to the optimization of interest, which complicates design of IIR algorithms. This issue is particularly acute for CT with a limited angular-range scan, which leads to poorly conditioned system matrices and difficult to solve optimization problems. In this paper, we develop IIR algorithms which solve a certain type of optimization called convex feasibility. The convex feasibility approach can provide alternatives to unconstrained optimization approaches and at the same time allow for rapidly convergent algorithms for their solution-thereby facilitating the IIR algorithm design process. Methods: An accelerated version of the Chambolle-Pock (CP) algorithm is adapted to various convex feasibility problems of potential interest to IIR in CT. One of the proposed problems is seen to be equivalent to least-squares minimization, and two other problems provide alternatives to penalized, least-squares minimization. Results: The accelerated CP algorithms are demonstrated on a simulation of circular fan-beam CT with a limited scanning arc of 144 Degree-Sign . The CP algorithms are seen in the empirical results to converge to the solution of their respective convex feasibility problems. Conclusions: Formulation of convex feasibility problems can provide a useful alternative to unconstrained optimization when designing IIR algorithms for CT. The approach is amenable to recent methods for accelerating first-order algorithms which may be particularly useful for CT with limited angular-range scanning. The present paper demonstrates the methodology, and future work will illustrate its utility in actual CT application.
Non-convex shape models of asteroids based on photometric observations
NASA Astrophysics Data System (ADS)
Bartczak, P.; Santana-Ros, T.; Michalowski, T.
2014-07-01
We present the SAGE algorithm (Shaping Asteroids with Genetic Evolution) able to derive 3D non-convex shapes of asteroids and solving for their spin parameters using only disk-integrated photometry. A triangular mesh of 62 vertices is used as a seed during the parameters minimization, and the Catmull-Clark method (Catmull-Clark 1978) is applied to generate bodies with higher resolution. The subroutines search for the sidereal period of rotation in a given range, and the spin-axis orientation on the whole celestial sphere. A step-iterative algorithm is used to make the shape evolve under the minimization constraints between the synthetic generated photometry and the real observations. In order to generate the simulated lightcurves, we propose the virtual frames algorithm. The algorithm simulates the pictures visible on hypothetical CCD frames and, using only elementary vector operations or quadratic algebraic equations, it takes into account all phase-angle effects. Publicly available lightcurve data has been used to obtain a new non-convex model for (9) Metis, (21) Lutetia, and (433) Eros. The resulting body shapes are compared with the ones obtained using other observational techniques, such as adaptive optics and stellar occultations (Timerson et al. 2009) or the NEAR Shoemaker observations of Eros during its rendezvous (Zuber et al. 2000). We also assess the problem of the solution uniqueness for non-convex models, generating a family of shape solutions and studying the stability of the model features. Moreover, following the investigations presented in Kaasalainen & Torppa (2001) we study the discrepancy on the lightcurves between a non-convex shape model and its convex hull as a function of the phase angle. Finally, we compare the lightcurve fits obtained with other existing models for both ''classic'' and sparse-in-time photometry.
First-order convex feasibility algorithms for x-ray CT
Sidky, Emil Y.; Jørgensen, Jakob S.; Pan, Xiaochuan
2013-01-01
Purpose: Iterative image reconstruction (IIR) algorithms in computed tomography (CT) are based on algorithms for solving a particular optimization problem. Design of the IIR algorithm, therefore, is aided by knowledge of the solution to the optimization problem on which it is based. Often times, however, it is impractical to achieve accurate solution to the optimization of interest, which complicates design of IIR algorithms. This issue is particularly acute for CT with a limited angular-range scan, which leads to poorly conditioned system matrices and difficult to solve optimization problems. In this paper, we develop IIR algorithms which solve a certain type of optimization called convex feasibility. The convex feasibility approach can provide alternatives to unconstrained optimization approaches and at the same time allow for rapidly convergent algorithms for their solution—thereby facilitating the IIR algorithm design process. Methods: An accelerated version of the Chambolle−Pock (CP) algorithm is adapted to various convex feasibility problems of potential interest to IIR in CT. One of the proposed problems is seen to be equivalent to least-squares minimization, and two other problems provide alternatives to penalized, least-squares minimization. Results: The accelerated CP algorithms are demonstrated on a simulation of circular fan-beam CT with a limited scanning arc of 144°. The CP algorithms are seen in the empirical results to converge to the solution of their respective convex feasibility problems. Conclusions: Formulation of convex feasibility problems can provide a useful alternative to unconstrained optimization when designing IIR algorithms for CT. The approach is amenable to recent methods for accelerating first-order algorithms which may be particularly useful for CT with limited angular-range scanning. The present paper demonstrates the methodology, and future work will illustrate its utility in actual CT application. PMID:23464295
Beermann, Jonas; Eriksen, René L.; Holmgaard, Tobias; Pedersen, Kjeld; Bozhevolnyi, Sergey I.
2014-01-01
Plasmonic black surfaces formed by two-dimensional arrays of ultra-sharp convex metal grooves, in which the incident radiation is converted into gap surface plasmon polaritons (GSPPs) and subsequently absorbed (via adiabatic nanofocusing), are fabricated and investigated experimentally for gold, nickel, and palladium, using scanning electron microscopy, optical microscopy, and reflection spectroscopy for their characterization. Absolute reflectivity spectra obtained for all fabricated arrays demonstrate very efficient and broadband absorption of unpolarized light exceeding the level of 95%, averaged over the investigated wavelength range of 400–985 nm. The highest averaged absorption level (~97%) is achieved with 250-nm-period arrays in palladium that also has the highest melting temperature (~1552°C), promising thereby potential applications for broadband absorption, e.g., within thermophotovoltaics. For one-dimensional arrays, GSPPs are excited only with the electric field polarized perpendicular to the groove orientation, resulting in 94–96% absorption of the appropriately polarized light for the arrays in nickel and palladium while featuring practically flat surface reflectivity spectra for the orthogonal polarization. The largest ratio (~10.7) between averaged reflectivities for orthogonal polarizations is achieved with the groove arrays in palladium, pointing thereby towards applications as broadband and low-dispersion linear polarizers operating in reflection, e.g., within ultra-fast optics. PMID:25365991
NASA Astrophysics Data System (ADS)
de Castro, A.; Alegre, D.; Tabarés, F. L.
2015-08-01
Ammonia production in N2/H2 direct current glow discharge plasmas, with nitrogen concentrations from 1.5% to 33%, different wall materials (tungsten, stainless steel and aluminium as a proxy for beryllium) and surface temperatures up to 350 °C has been investigated. Ammonia yields on the exposed materials have been deduced, resulting in different values depending on the wall material, its temperature and N2 plasma content. The results indicate weak wall temperature dependence in tungsten and stainless steel. However, wall temperatures above 300 °C have a very clear influence on aluminium walls, as almost all the molecular N2 depleted from the gas phase is converted into ammonia. The amount of implanted N seems to have a direct impact on the ammonia formation yield, pointing to the competition between N implantation and N/H-N/N recombination on the walls as the key mechanism of the ammonia formation.
Still-to-video face recognition in unconstrained environments
NASA Astrophysics Data System (ADS)
Wang, Haoyu; Liu, Changsong; Ding, Xiaoqing
2015-02-01
Face images from video sequences captured in unconstrained environments usually contain several kinds of variations, e.g. pose, facial expression, illumination, image resolution and occlusion. Motion blur and compression artifacts also deteriorate recognition performance. Besides, in various practical systems such as law enforcement, video surveillance and e-passport identification, only a single still image per person is enrolled as the gallery set. Many existing methods may fail to work due to variations in face appearances and the limit of available gallery samples. In this paper, we propose a novel approach for still-to-video face recognition in unconstrained environments. By assuming that faces from still images and video frames share the same identity space, a regularized least squares regression method is utilized to tackle the multi-modality problem. Regularization terms based on heuristic assumptions are enrolled to avoid overfitting. In order to deal with the single image per person problem, we exploit face variations learned from training sets to synthesize virtual samples for gallery samples. We adopt a learning algorithm combining both affine/convex hull-based approach and regularizations to match image sets. Experimental results on a real-world dataset consisting of unconstrained video sequences demonstrate that our method outperforms the state-of-the-art methods impressively.
Learning discriminant face descriptor.
Lei, Zhen; Pietikäinen, Matti; Li, Stan Z
2014-02-01
Local feature descriptor is an important module for face recognition and those like Gabor and local binary patterns (LBP) have proven effective face descriptors. Traditionally, the form of such local descriptors is predefined in a handcrafted way. In this paper, we propose a method to learn a discriminant face descriptor (DFD) in a data-driven way. The idea is to learn the most discriminant local features that minimize the difference of the features between images of the same person and maximize that between images from different people. In particular, we propose to enhance the discriminative ability of face representation in three aspects. First, the discriminant image filters are learned. Second, the optimal neighborhood sampling strategy is soft determined. Third, the dominant patterns are statistically constructed. Discriminative learning is incorporated to extract effective and robust features. We further apply the proposed method to the heterogeneous (cross-modality) face recognition problem and learn DFD in a coupled way (coupled DFD or C-DFD) to reduce the gap between features of heterogeneous face images to improve the performance of this challenging problem. Extensive experiments on FERET, CAS-PEAL-R1, LFW, and HFB face databases validate the effectiveness of the proposed DFD learning on both homogeneous and heterogeneous face recognition problems. The DFD improves POEM and LQP by about 4.5 percent on LFW database and the C-DFD enhances the heterogeneous face recognition performance of LBP by over 25 percent. PMID:24356350
A shape-based account for holistic face processing.
Zhao, Mintao; Bülthoff, Heinrich H; Bülthoff, Isabelle
2016-04-01
Faces are processed holistically, so selective attention to 1 face part without any influence of the others often fails. In this study, 3 experiments investigated what type of facial information (shape or surface) underlies holistic face processing and whether generalization of holistic processing to nonexperienced faces requires extensive discrimination experience. Results show that facial shape information alone is sufficient to elicit the composite face effect (CFE), 1 of the most convincing demonstrations of holistic processing, whereas facial surface information is unnecessary (Experiment 1). The CFE is eliminated when faces differ only in surface but not shape information, suggesting that variation of facial shape information is necessary to observe holistic face processing (Experiment 2). Removing 3-dimensional (3D) facial shape information also eliminates the CFE, indicating the necessity of 3D shape information for holistic face processing (Experiment 3). Moreover, participants show similar holistic processing for faces with and without extensive discrimination experience (i.e., own- and other-race faces), suggesting that generalization of holistic processing to nonexperienced faces requires facial shape information, but does not necessarily require further individuation experience. These results provide compelling evidence that facial shape information underlies holistic face processing. This shape-based account not only offers a consistent explanation for previous studies of holistic face processing, but also suggests a new ground-in addition to expertise-for the generalization of holistic processing to different types of faces and to nonface objects. (PsycINFO Database Record PMID:26371495
NASA Astrophysics Data System (ADS)
Gregory, James; Danon, Ron; Greenblatt, David
2015-11-01
The time-resolved formation and structure of Görtler vortices in a pulsed convex wall jet are studied in this work. While the presence of Görtler vortices in laminar boundary layers on concave surfaces can be clearly observed, their presence in wall jets flowing over convex surfaces is difficult to discern due to transition to turbulence in the outer part of the jet. This work employed fast-response pressure-sensitive paint (PSP), which has a documented flat frequency response greater than 5 kHz, to visualize the time-resolved formation of the wall jet and the details of the Görtler vortices. The radius of curvature of the wall jet was 8 cm, and the Reynolds number (based on slot height and jet exit velocity) was varied between 5 ×102 and 4 ×104 . The characteristic spanwise wavelength of the vortices was studied as a function of jet Reynolds number. Furthermore, as the Reynolds number was increased, various secondary instabilities were observed that led to laminar-turbulent transition. Funding provided by the U.S. Fulbright Scholar Program.
Quantitative Analysis of Face Symmetry.
Tamir, Abraham
2015-06-01
The major objective of this article was to report quantitatively the degree of human face symmetry for reported images taken from the Internet. From the original image of a certain person that appears in the center of each triplet, 2 symmetric combinations were constructed that are based on the left part of the image and its mirror image (left-left) and on the right part of the image and its mirror image (right-right). By applying a computer software that enables to determine length, surface area, and perimeter of any geometric shape, the following measurements were obtained for each triplet: face perimeter and area; distance between the pupils; mouth length; its perimeter and area; nose length and face length, usually below the ears; as well as the area and perimeter of the pupils. Then, for each of the above measurements, the value C, which characterizes the degree of symmetry of the real image with respect to the combinations right-right and left-left, was calculated. C appears on the right-hand side below each image. A high value of C indicates a low symmetry, and as the value is decreasing, the symmetry is increasing. The magnitude on the left relates to the pupils and compares the difference between the area and perimeter of the 2 pupils. The major conclusion arrived at here is that the human face is asymmetric to some degree; the degree of asymmetry is reported quantitatively under each portrait. PMID:26080172
Faciotopy—A face-feature map with face-like topology in the human occipital face area
Henriksson, Linda; Mur, Marieke; Kriegeskorte, Nikolaus
2015-01-01
The occipital face area (OFA) and fusiform face area (FFA) are brain regions thought to be specialized for face perception. However, their intrinsic functional organization and status as cortical areas with well-defined boundaries remains unclear. Here we test these regions for “faciotopy”, a particular hypothesis about their intrinsic functional organisation. A faciotopic area would contain a face-feature map on the cortical surface, where cortical patches represent face features and neighbouring patches represent features that are physically neighbouring in a face. The faciotopy hypothesis is motivated by the idea that face regions might develop from a retinotopic protomap and acquire their selectivity for face features through natural visual experience. Faces have a prototypical configuration of features, are usually perceived in a canonical upright orientation, and are frequently fixated in particular locations. To test the faciotopy hypothesis, we presented images of isolated face features at fixation to subjects during functional magnetic resonance imaging. The responses in V1 were best explained by low-level image properties of the stimuli. OFA, and to a lesser degree FFA, showed evidence for faciotopic organization. When a single patch of cortex was estimated for each face feature, the cortical distances between the feature patches reflected the physical distance between the features in a face. Faciotopy would be the first example, to our knowledge, of a cortical map reflecting the topology, not of a part of the organism itself (its retina in retinotopy, its body in somatotopy), but of an external object of particular perceptual significance. PMID:26235800
Generalization of affective learning about faces to perceptually similar faces.
Verosky, Sara C; Todorov, Alexander
2010-06-01
Different individuals have different (and different-looking) significant others, friends, and foes. The objective of this study was to investigate whether these social face environments can shape individual face preferences. First, participants learned to associate faces with positive, neutral, or negative behaviors. Then, they evaluated morphs combining novel faces with the learned faces. The morphs (65% and 80% novel faces) were within the categorical boundary of the novel faces: They were perceived as those faces in a preliminary study. Moreover, a second preliminary study showed that following the learning, the morphs' categorization as similar to the learned faces was indistinguishable from the categorization of actual novel faces. Nevertheless, in the main experiment, participants evaluated morphs of "positive" faces more positively than morphs of "negative" faces. This learning generalization effect increased as a function of the similarity of the novel faces to the learned faces. The findings suggest that general learning mechanisms based on similarity can account for idiosyncratic face preferences. PMID:20483821
New determinations and simplified representations of macromolecular surfaces.
Perrot, G; Maigret, B
1990-09-01
Several new methods or improvements of older algorithms determining the different pieces of molecular surface are presented. Their improvement in time and their complexity are discussed. Only the indexes of the atoms on which the pieces are relying are, in fact, determined, since their explicit representation from these numbers varies according to the 3D capabilities of the graphic workstation (dots, grid, etc.), and this generation is not C.P.U. consuming. To have a simplified representation of the surface of macromolecules, a polyhedron with planar triangular faces is then introduced: Each concave triangular surface piece is replaced with planar triangles relying on its three atomic centers, while saddle-shaped rectangles and convex pieces are wholly ignored. A minimal data structure of the polyhedron is then proposed, which contains only topological informations, since no coordinates have been generated. If the atomic radius is then considered to be constant (independent of atomic type), the surface of a set of N points is now defined by the choice of a subset with a topology. This choice is controlled by a parameter of rugosity (the atomic radius). Contrary to Voronoi polyhedrons partition, which gives a topology for a set of N points, our approach gives a topology only for the exterior points of this set. A few applications of this very simple definition of molecular surface are then discussed: the 3D interactive manipulation of macromolecules, the steric intermolecular recognition, and the determination of local and global properties of the surface. PMID:2279010
NASA Astrophysics Data System (ADS)
Herndl, Markus; Pötsch, Erich; Kandolf, Matthias; Bohner, Andreas; Schaumberger, Andreas; Resch, Reinhard; Graiss, Wilhelm; Krautzer, Bernhard; Buchgraber, Karl
2010-05-01
During the past century the average global surface air temperature has already increased by 1°C. A doubling of atmospheric concentration of CO2 near the end of the 21st century is predicted to result in a 3°C temperature increase. The Alpine region has experienced above average warming over the last century and is considered particularly vulnerable to global change. In Austria in some regions, grassland production suffered severe droughts during the last decade leading to serious damages and even temporal shortage in feed supply. Changes in temperature and precipitation have evident consequences for grassland vegetation. Increasing atmospheric CO2 concentration is a major driver of climate change. Photosynthesis and productivity of most grassland species might be stimulated by increasing CO2 when soil nutrients and water are not limiting. On dry grassland sites increasing CO2 also reduces plant water loss, thereby increasing plant water use efficiency. When plant production is limited by seasonal cold temperatures as e.g. in the inner Alpine parts of Austria and in high altitude or high latitude grasslands, combined warming and higher CO2 might continue to enhance plant production. However, it is still unknown to what extend a further increase of temperature and CO2 will result in higher biomass yield in different grassland communities. To study the effects of global warming on future grassland communities and management, the application of a heating treatment combined with free-air controlled enhancement of CO2 (T-FACE) to open-field plant canopies at lysimeters is an innovative approach which allows studying responses of the plant-soil-systems as well as carbon- water and nutrient fluxes under expected future climate. The experiment is scheduled to run in the first phase 6 years (2011-2017) and is located at the AREC Raumberg-Gumpenstein, Upper Enns Valley, Austria (47,49; 14,10). Heater arrays and miniFACE rings are installed in 1.6 m diameter plots and expose
Extended surface parallel coating inspection method
Naulleau, Patrick P.
2006-03-21
Techniques for rapidly characterizing reflective surfaces and especially multi-layer EUV reflective surfaces of optical components involve illuminating the entire reflective surface instantaneously and detecting the image far field. The technique provides a mapping of points on the reflective surface to corresponding points on a detector, e.g., CCD. This obviates the need to scan a probe over the entire surface of the optical component. The reflective surface can be flat, convex, or concave.
Multimode Root locus for a Matrix with uncertainty using convex lowbar Hull
Hussein, Mohammed Tawfik
2009-03-05
The goal of this paper is to investigate the robust stability of the uncertain system based on the edge theorem and the Bhattacharyya and Keel algorithm. Firstly, the dynamic model for the system will be derived, then, Depending on the uncertainty, which appears in the elements of matrix A, the system will generates a set of interval matrices, secondly the procedures of the proposed algorithm to find convex hull of the system by Using the method of Andrew's Monotone Chain Algorithm will be implemented, and lastly root locus method will be utilized and applied to the exposed edges of the convex polygon and yet; the sharp and tight bounds of the eigenvalues of the proposed uncertain systems will be computed. An Electrical engineering system will be presented as practical example to validate the proposed method.
A trait-based test for habitat filtering: Convex hull volume
Cornwell, W.K.; Schwilk, D.W.; Ackerly, D.D.
2006-01-01
Community assembly theory suggests that two processes affect the distribution of trait values within communities: competition and habitat filtering. Within a local community, competition leads to ecological differentiation of coexisting species, while habitat filtering reduces the spread of trait values, reflecting shared ecological tolerances. Many statistical tests for the effects of competition exist in the literature, but measures of habitat filtering are less well-developed. Here, we present convex hull volume, a construct from computational geometry, which provides an n-dimensional measure of the volume of trait space occupied by species in a community. Combined with ecological null models, this measure offers a useful test for habitat filtering. We use convex hull volume and a null model to analyze California woody-plant trait and community data. Our results show that observed plant communities occupy less trait space than expected from random assembly, a result consistent with habitat filtering. ?? 2006 by the Ecological Society of America.
Fast multiscale Gaussian beam methods for wave equations in bounded convex domains
Bao, Gang; Lai, Jun; Qian, Jianliang
2014-03-15
Motivated by fast multiscale Gaussian wavepacket transforms and multiscale Gaussian beam methods which were originally designed for pure initial-value problems of wave equations, we develop fast multiscale Gaussian beam methods for initial boundary value problems of wave equations in bounded convex domains in the high frequency regime. To compute the wave propagation in bounded convex domains, we have to take into account reflecting multiscale Gaussian beams, which are accomplished by enforcing reflecting boundary conditions during beam propagation and carrying out suitable reflecting beam summation. To propagate multiscale beams efficiently, we prove that the ratio of the squared magnitude of beam amplitude and the beam width is roughly conserved, and accordingly we propose an effective indicator to identify significant beams. We also prove that the resulting multiscale Gaussian beam methods converge asymptotically. Numerical examples demonstrate the accuracy and efficiency of the method.
Octupolar approximation for the excluded volume of axially symmetric convex bodies
NASA Astrophysics Data System (ADS)
Piastra, Marco; Virga, Epifanio G.
2013-09-01
We propose a simply computable formula for the excluded volume of convex, axially symmetric bodies, based on the classical Brunn-Minkoski theory for convex bodies, which is briefly outlined in an Appendix written in a modern mathematical language. This formula is applied to cones and spherocones, which are regularized cones; a shape-reconstruction algorithm is able to generate the region in space inaccessible to them and to compute their excluded volume, which is found to be in good agreement with our approximate analytical formula. Finally, for spherocones with an appropriately tuned amplitude, we predict the occurrence of a relative deep minimum of the excluded volume in a configuration lying between the parallel alignment (where the excluded volume is maximum) and the antiparallel alignment (where the excluded volume is minimum).
The New Vector Fitting Approach to Multiple Convex Obstacles Modeling for UWB Propagation Channels
NASA Astrophysics Data System (ADS)
Górniak, P.; Bandurski, W.
This chapter presents the new approach to time-domain modeling of UWB channels containing multiple convex obstacles. Vector fitting (VF) algorithm (rational approximation) was used for deriving the closed form impulse response of multiple diffraction ray creeping on a cascade of convex obstacles. VF algorithm was performed with respect to new generalized variables proportional to frequency but including geometrical parameters of the obstacles also. The limits of approximation domain for vector fitting algorithm follow the range of ultra-wideband (UWB) channel parameters that can be met in practical UWB channel scenarios. Finally, the closed form impulse response of a creeping UTD ray was obtained. As the result we obtained impulse response of the channel as a function of normalized, with respect to geometrical parameters of the obstacles, time. It permits for calculation of channel responses for various objects without changing the body of a rational function. In that way the presented approach is general, simple, and effective.
NASA Astrophysics Data System (ADS)
Zhang, Xiao-Ming; Ding, Han
2008-11-01
The concept of uncertainty plays an important role in the design of practical mechanical system. The most common methods for solving uncertainty problems are to model the parameters as a random vector. A natural way to handle the randomness is to admit that a given probability density function represents the uncertainty distribution. However, the drawback of this approach is that the probability distribution is difficult to obtain. In this paper, we use the non-probabilistic convex model to deal with the uncertain parameters in which there is no need for probability density functions. Using the convex model theory, a new method to optimize the dynamic response of mechanical system with uncertain parameters is derived. Because the uncertain parameters can be selected as the optimization parameters, the present method can provide more information about the optimization results than those obtained by the deterministic optimization. The present method is implemented for a torsional vibration system. The numerical results show that the method is effective.
Estimating the chromatic numbers of Euclidean space by convex minimization methods
Gorskaya, Elena S; Mitricheva, Irina M; Protasov, Vladimir Yu; Raigorodskii, Andrei M
2009-06-30
The chromatic numbers of the Euclidean space R{sup n} with k forbidden distances are investigated (that is, the minimum numbers of colours necessary to colour all points in R{sup n} so that no two points of the same colour lie at a forbidden distance from each other). Estimates for the growth exponents of the chromatic numbers as n{yields}{infinity} are obtained. The so-called linear algebra method which has been developed is used for this. It reduces the problem of estimating the chromatic numbers to an extremal problem. To solve this latter problem a fundamentally new approach is used, which is based on the theory of convex extremal problems and convex analysis. This allows the required estimates to be found for any k. For k{<=}20 these estimates are found explicitly; they are the best possible ones in the framework of the method mentioned above. Bibliography: 18 titles.
A Genealogy of Convex Solids Via Local and Global Bifurcations of Gradient Vector Fields
NASA Astrophysics Data System (ADS)
Domokos, Gábor; Holmes, Philip; Lángi, Zsolt
2016-06-01
Three-dimensional convex bodies can be classified in terms of the number and stability types of critical points on which they can balance at rest on a horizontal plane. For typical bodies, these are non-degenerate maxima, minima, and saddle points, the numbers of which provide a primary classification. Secondary and tertiary classifications use graphs to describe orbits connecting these critical points in the gradient vector field associated with each body. In previous work, it was shown that these classifications are complete in that no class is empty. Here, we construct 1- and 2-parameter families of convex bodies connecting members of adjacent primary and secondary classes and show that transitions between them can be realized by codimension 1 saddle-node and saddle-saddle (heteroclinic) bifurcations in the gradient vector fields. Our results indicate that all combinatorially possible transitions can be realized in physical shape evolution processes, e.g., by abrasion of sedimentary particles.
Moors, Pieter; Wagemans, Johan; de-Wit, Lee
2016-01-01
The extent to which perceptually suppressed face stimuli are still processed has been extensively studied using the continuous flash suppression paradigm (CFS). Studies that rely on breaking CFS (b-CFS), in which the time it takes for an initially suppressed stimulus to become detectable is measured, have provided evidence for relatively complex processing of invisible face stimuli. In contrast, adaptation and neuroimaging studies have shown that perceptually suppressed faces are only processed for a limited set of features, such as its general shape. In this study, we asked whether perceptually suppressed face stimuli presented in their commonly experienced configuration would break suppression faster than when presented in an uncommonly experienced configuration. This study was motivated by a recent neuroimaging study showing that commonly experienced face configurations are more strongly represented in the fusiform face area. Our findings revealed that faces presented in commonly experienced configurations indeed broke suppression faster, yet this effect did not interact with face inversion suggesting that, in a b-CFS context, perceptually suppressed faces are potentially not processed by specialized (high-level) face processing mechanisms. Rather, our pattern of results is consistent with an interpretation based on the processing of more basic visual properties such as convexity. PMID:26839746
Wagemans, Johan; de-Wit, Lee
2016-01-01
The extent to which perceptually suppressed face stimuli are still processed has been extensively studied using the continuous flash suppression paradigm (CFS). Studies that rely on breaking CFS (b-CFS), in which the time it takes for an initially suppressed stimulus to become detectable is measured, have provided evidence for relatively complex processing of invisible face stimuli. In contrast, adaptation and neuroimaging studies have shown that perceptually suppressed faces are only processed for a limited set of features, such as its general shape. In this study, we asked whether perceptually suppressed face stimuli presented in their commonly experienced configuration would break suppression faster than when presented in an uncommonly experienced configuration. This study was motivated by a recent neuroimaging study showing that commonly experienced face configurations are more strongly represented in the fusiform face area. Our findings revealed that faces presented in commonly experienced configurations indeed broke suppression faster, yet this effect did not interact with face inversion suggesting that, in a b-CFS context, perceptually suppressed faces are potentially not processed by specialized (high-level) face processing mechanisms. Rather, our pattern of results is consistent with an interpretation based on the processing of more basic visual properties such as convexity. PMID:26839746
Maximally dense packings of two-dimensional convex and concave noncircular particles
NASA Astrophysics Data System (ADS)
Atkinson, Steven; Jiao, Yang; Torquato, Salvatore
2012-09-01
Dense packings of hard particles have important applications in many fields, including condensed matter physics, discrete geometry, and cell biology. In this paper, we employ a stochastic search implementation of the Torquato-Jiao adaptive-shrinking-cell (ASC) optimization scheme [Nature (London)NATUAS0028-083610.1038/nature08239 460, 876 (2009)] to find maximally dense particle packings in d-dimensional Euclidean space Rd. While the original implementation was designed to study spheres and convex polyhedra in d≥3, our implementation focuses on d=2 and extends the algorithm to include both concave polygons and certain complex convex or concave nonpolygonal particle shapes. We verify the robustness of this packing protocol by successfully reproducing the known putative optimal packings of congruent copies of regular pentagons and octagons, then employ it to suggest dense packing arrangements of congruent copies of certain families of concave crosses, convex and concave curved triangles (incorporating shapes resembling the Mercedes-Benz logo), and “moonlike” shapes. Analytical constructions are determined subsequently to obtain the densest known packings of these particle shapes. For the examples considered, we find that the densest packings of both convex and concave particles with central symmetry are achieved by their corresponding optimal Bravais lattice packings; for particles lacking central symmetry, the densest packings obtained are nonlattice periodic packings, which are consistent with recently-proposed general organizing principles for hard particles. Moreover, we find that the densest known packings of certain curved triangles are periodic with a four-particle basis, and we find that the densest known periodic packings of certain moonlike shapes possess no inherent symmetries. Our work adds to the growing evidence that particle shape can be used as a tuning parameter to achieve a diversity of packing structures.
Maximally dense packings of two-dimensional convex and concave noncircular particles.
Atkinson, Steven; Jiao, Yang; Torquato, Salvatore
2012-09-01
Dense packings of hard particles have important applications in many fields, including condensed matter physics, discrete geometry, and cell biology. In this paper, we employ a stochastic search implementation of the Torquato-Jiao adaptive-shrinking-cell (ASC) optimization scheme [Nature (London) 460, 876 (2009)] to find maximally dense particle packings in d-dimensional Euclidean space R(d). While the original implementation was designed to study spheres and convex polyhedra in d≥3, our implementation focuses on d=2 and extends the algorithm to include both concave polygons and certain complex convex or concave nonpolygonal particle shapes. We verify the robustness of this packing protocol by successfully reproducing the known putative optimal packings of congruent copies of regular pentagons and octagons, then employ it to suggest dense packing arrangements of congruent copies of certain families of concave crosses, convex and concave curved triangles (incorporating shapes resembling the Mercedes-Benz logo), and "moonlike" shapes. Analytical constructions are determined subsequently to obtain the densest known packings of these particle shapes. For the examples considered, we find that the densest packings of both convex and concave particles with central symmetry are achieved by their corresponding optimal Bravais lattice packings; for particles lacking central symmetry, the densest packings obtained are nonlattice periodic packings, which are consistent with recently-proposed general organizing principles for hard particles. Moreover, we find that the densest known packings of certain curved triangles are periodic with a four-particle basis, and we find that the densest known periodic packings of certain moonlike shapes possess no inherent symmetries. Our work adds to the growing evidence that particle shape can be used as a tuning parameter to achieve a diversity of packing structures. PMID:23030907
Surgical limitations in convexity meningiomas en-plaque: Is radical resection necessary?
Yao, Amy; Sarkiss, Christopher A; Lee, James; Zarzour, Hekmat K; Shrivastava, Raj K
2016-05-01
Meningiomas-en-plaque (MEP) comprise 2.5% of all meningiomas. While they typically arise in the sphenoid wing, convexity MEP are comparatively rare and are often confused with meningeal sarcoidosis, osteoma, tuberculoma, or fibrous dysplasia, with very little information published in the literature. We conducted a literature review on PubMed of English-only articles using a keyword search. All studies that described reports of convexity MEP were reviewed for patient demographics, presenting symptoms, radiological reports, surgical management, recurrence rates, histopathological presentation, post-operative complications, and follow-up. This resulted in 12 papers comprising 22 cases of convexity MEP. Seventeen (77%) of the 22 patients were female with an average age of 53.2years. Intitial presenting symptoms included headache in 12/20 (60%), hemiparesis in 5/20 (25%), and visual symptoms in 1/20 (5%). Of the 14 patients who underwent surgical resection, only four were reported as gross total resection. Twelve reports had associated pathology reports, with all 12 tumors graded as World Health Organization Grade I. Convexity MEP, while rare, present a challenge with regard to correct diagnosis and subsequent resection. The easier accessibility of these meningiomas predicts higher surgical success rates and incidence of total resection, though care must be taken to ensure gross total removal of tumor, dural attachments, and any overlying hyperostotic bone. Though hyperostosis is frequently observed with this variant of meningioma, it is neither exclusive nor wholly indicative of MEP. Due to its rarity in both clinical practice and the literature, further studies are warranted to identify modern imaging means to correctly diagnose this condition. PMID:26778515
Image restoration by the method of convex projections: part 2 applications and numerical results.
Sezan, M I; Stark, H
1982-01-01
The image restoration theory discussed in a previous paper by Youla and Webb [1] is applied to a simulated image and the results compared with the well-known method known as the Gerchberg-Papoulis algorithm. The results show that the method of image restoration by projection onto convex sets, by providing a convenient technique for utilizing a priori information, performs significantly better than the Gerchberg-Papoulis method. PMID:18238262
Nonlinear Stability of a SIRS Epidemic Model with Convex Incidence Rate
NASA Astrophysics Data System (ADS)
Buonomo, B.; Rionero, S.
2010-09-01
We study an epidemic model for infections with non permanent acquired immunity (SIRS). The incidence rate is assumed to be convex respect to the infective class. By using a peculiar Lyapunov function, we obtain necessary and sufficient conditions for the local nonlinear stability of equilibria. Conditions ensuring the global stability of the endemic equilibrium are also obtained. Our procedure allows to enlarge the class of incidence rates ensuring the Lyapunov nonlinear stability of the endemic equilibrium for SIRS models.
Sparse representations and convex optimization as tools for LOFAR radio interferometric imaging
NASA Astrophysics Data System (ADS)
Girard, J. N.; Garsden, H.; Starck, J. L.; Corbel, S.; Woiselle, A.; Tasse, C.; McKean, J. P.; Bobin, J.
2015-08-01
Compressed sensing theory is slowly making its way to solve more and more astronomical inverse problems. We address here the application of sparse representations, convex optimization and proximal theory to radio interferometric imaging. First, we expose the theory behind interferometric imaging, sparse representations and convex optimization, and second, we illustrate their application with numerical tests with SASIR, an implementation of the FISTA, a Forward-Backward splitting algorithm hosted in a LOFAR imager. Various tests have been conducted in Garsden et al., 2015. The main results are: i) an improved angular resolution (super resolution of a factor ≈ 2) with point sources as compared to CLEAN on the same data, ii) correct photometry measurements on a field of point sources at high dynamic range and iii) the imaging of extended sources with improved fidelity. SASIR provides better reconstructions (five time less residuals) of the extended emission as compared to CLEAN. With the advent of large radiotelescopes, there is scope for improving classical imaging methods with convex optimization methods combined with sparse representations.
Dynamical tunneling versus fast diffusion for a non-convex Hamiltonian.
Pittman, S M; Tannenbaum, E; Heller, E J
2016-08-01
This paper attempts to resolve the issue of the nature of the 0.01-0.1 cm(-1) peak splittings observed in high-resolution IR spectra of polyatomic molecules. One hypothesis is that these splittings are caused by dynamical tunneling, a quantum-mechanical phenomenon whereby energy flows between two disconnected regions of phase-space across dynamical barriers. However, a competing classical mechanism for energy flow is Arnol'd diffusion, which connects different regions of phase-space by a resonance network known as the Arnol'd web. The speed of diffusion is bounded by the Nekhoroshev theorem, which guarantees stability on exponentially long time scales if the Hamiltonian is steep. Here we consider a non-convex Hamiltonian that contains the characteristics of a molecular Hamiltonian, but does not satisfy the Nekhoroshev theorem. The diffusion along the Arnol'd web is expected to be fast for a non-convex Hamiltonian. While fast diffusion is an unlikely competitor for longtime energy flow in molecules, we show how dynamical tunneling dominates compared to fast diffusion in the nearly integrable regime for a non-convex Hamiltonian, as well as present a new kind of dynamical tunneling. PMID:27497557
Hard convex lens-shaped particles: Densest-known packings and phase behavior
NASA Astrophysics Data System (ADS)
Cinacchi, Giorgio; Torquato, Salvatore
2015-12-01
By using theoretical methods and Monte Carlo simulations, this work investigates dense ordered packings and equilibrium phase behavior (from the low-density isotropic fluid regime to the high-density crystalline solid regime) of monodisperse systems of hard convex lens-shaped particles as defined by the volume common to two intersecting congruent spheres. We show that, while the overall similarity of their shape to that of hard oblate ellipsoids is reflected in a qualitatively similar phase diagram, differences are more pronounced in the high-density crystal phase up to the densest-known packings determined here. In contrast to those non-(Bravais)-lattice two-particle basis crystals that are the densest-known packings of hard (oblate) ellipsoids, hard convex lens-shaped particles pack more densely in two types of degenerate crystalline structures: (i) non-(Bravais)-lattice two-particle basis body-centered-orthorhombic-like crystals and (ii) (Bravais) lattice monoclinic crystals. By stacking at will, regularly or irregularly, laminae of these two crystals, infinitely degenerate, generally non-periodic in the stacking direction, dense packings can be constructed that are consistent with recent organizing principles. While deferring the assessment of which of these dense ordered structures is thermodynamically stable in the high-density crystalline solid regime, the degeneracy of their densest-known packings strongly suggests that colloidal convex lens-shaped particles could be better glass formers than colloidal spheres because of the additional rotational degrees of freedom.
Hard convex lens-shaped particles: Densest-known packings and phase behavior
Cinacchi, Giorgio; Torquato, Salvatore
2015-12-14
By using theoretical methods and Monte Carlo simulations, this work investigates dense ordered packings and equilibrium phase behavior (from the low-density isotropic fluid regime to the high-density crystalline solid regime) of monodisperse systems of hard convex lens-shaped particles as defined by the volume common to two intersecting congruent spheres. We show that, while the overall similarity of their shape to that of hard oblate ellipsoids is reflected in a qualitatively similar phase diagram, differences are more pronounced in the high-density crystal phase up to the densest-known packings determined here. In contrast to those non-(Bravais)-lattice two-particle basis crystals that are the densest-known packings of hard (oblate) ellipsoids, hard convex lens-shaped particles pack more densely in two types of degenerate crystalline structures: (i) non-(Bravais)-lattice two-particle basis body-centered-orthorhombic-like crystals and (ii) (Bravais) lattice monoclinic crystals. By stacking at will, regularly or irregularly, laminae of these two crystals, infinitely degenerate, generally non-periodic in the stacking direction, dense packings can be constructed that are consistent with recent organizing principles. While deferring the assessment of which of these dense ordered structures is thermodynamically stable in the high-density crystalline solid regime, the degeneracy of their densest-known packings strongly suggests that colloidal convex lens-shaped particles could be better glass formers than colloidal spheres because of the additional rotational degrees of freedom.
On the contact treatment of non-convex particles in the granular element method
NASA Astrophysics Data System (ADS)
Lim, Keng-Wit; Krabbenhoft, Kristian; Andrade, José E.
2014-09-01
We present a new contact algorithm that endows the granular element method [1] with the ability to model non-convex particles using non-uniform rational basis splines. This significant extension allows for the representation of particle morphological features, namely, sphericity and angularity, to their fullest extent, with local contact rolling resistance and interlocking emanating directly from grain geometry. Both particle elasticity and friction at the contact level are treated implicitly and simultaneously, and the contact algorithm is cast into a mathematical programming-based contact dynamics framework. The framework provides the advantages of implicit time integrators (for e.g., stability and larger time steps) and ability to handle both rigid and highly stiff particles. By allowing for particle non-convexity, modeling flexibility is significantly enhanced, to a level that is comparable with isogeometric methods. As such, the transition from image data to particle shapes is greatly streamlined. More importantly, increased macroscopic strength in granular packings comprising of non-convex particles is fully captured. All the above capabilities are achieved under a very modest implementation effort.
Dynamical tunneling versus fast diffusion for a non-convex Hamiltonian
NASA Astrophysics Data System (ADS)
Pittman, S. M.; Tannenbaum, E.; Heller, E. J.
2016-08-01
This paper attempts to resolve the issue of the nature of the 0.01-0.1 cm-1 peak splittings observed in high-resolution IR spectra of polyatomic molecules. One hypothesis is that these splittings are caused by dynamical tunneling, a quantum-mechanical phenomenon whereby energy flows between two disconnected regions of phase-space across dynamical barriers. However, a competing classical mechanism for energy flow is Arnol'd diffusion, which connects different regions of phase-space by a resonance network known as the Arnol'd web. The speed of diffusion is bounded by the Nekhoroshev theorem, which guarantees stability on exponentially long time scales if the Hamiltonian is steep. Here we consider a non-convex Hamiltonian that contains the characteristics of a molecular Hamiltonian, but does not satisfy the Nekhoroshev theorem. The diffusion along the Arnol'd web is expected to be fast for a non-convex Hamiltonian. While fast diffusion is an unlikely competitor for longtime energy flow in molecules, we show how dynamical tunneling dominates compared to fast diffusion in the nearly integrable regime for a non-convex Hamiltonian, as well as present a new kind of dynamical tunneling.
Sommargren, Gary E.; Campbell, Eugene W.
2005-06-21
To measure a convex mirror, a reference beam and a measurement beam are both provided through a single optical fiber. A positive auxiliary lens is placed in the system to give a converging wavefront onto the convex mirror under test. A measurement is taken that includes the aberrations of the convex mirror as well as the errors due to two transmissions through the positive auxiliary lens. A second measurement provides the information to eliminate this error. A negative lens can also be measured in a similar way. Again, there are two measurement set-ups. A reference beam is provided from a first optical fiber and a measurement beam is provided from a second optical fiber. A positive auxiliary lens is placed in the system to provide a converging wavefront from the reference beam onto the negative lens under test. The measurement beam is combined with the reference wavefront and is analyzed by standard methods. This measurement includes the aberrations of the negative lens, as well as the errors due to a single transmission through the positive auxiliary lens. A second measurement provides the information to eliminate this error.
Sommargren, Gary E.; Campbell, Eugene W.
2004-03-09
To measure a convex mirror, a reference beam and a measurement beam are both provided through a single optical fiber. A positive auxiliary lens is placed in the system to give a converging wavefront onto the convex mirror under test. A measurement is taken that includes the aberrations of the convex mirror as well as the errors due to two transmissions through the positive auxiliary lens. A second, measurement provides the information to eliminate this error. A negative lens can also be measured in a similar way. Again, there are two measurement set-ups. A reference beam is provided from a first optical fiber and a measurement beam is provided from a second optical fiber. A positive auxiliary lens is placed in the system to provide a converging wavefront from the reference beam onto the negative lens under test. The measurement beam is combined with the reference wavefront and is analyzed by standard methods. This measurement includes the aberrations of the negative lens, as well as the errors due to a single transmission through the positive auxiliary lens. A second measurement provides the information to eliminate this error.
Simulation and experimental study of maskless convex corner compensation in TMAH water solution
NASA Astrophysics Data System (ADS)
Smiljanić, Milče M.; Radjenović, Branislav; Radmilović-Radjenović, Marija; Lazić, Žarko; Jović, Vesna
2014-11-01
Maskless etching with convex corner compensation in the form of a <1 0 0> oriented beam is investigated using both experiments and simulations. The maskless convex corner compensation technique is defined as a combination of masked and maskless anisotropic etching of {1 0 0} silicon in 25 wt% TMAH water solution at a temperature of 80 °C. This technique enables fabrication of three-level micromachined silicon structures with compensated convex corners at the bottom of the etched structure. All crystallographic planes that appear during etching are determined and their etch rates are used to calculate the etch rate value in an arbitrary crystallographic direction necessary for simulation by an interpolation procedure. A 3D simulation of the profile evolution of the etched structure during masked and maskless etching of silicon based on the level set method is presented. All crystallographic planes of the etched silicon structures determined in the experiment are recognized in the corresponding simulated etching profiles obtained by the level set method.
Derivative-free generation and interpolation of convex Pareto optimal IMRT plans
NASA Astrophysics Data System (ADS)
Hoffmann, Aswin L.; Siem, Alex Y. D.; den Hertog, Dick; Kaanders, Johannes H. A. M.; Huizenga, Henk
2006-12-01
In inverse treatment planning for intensity-modulated radiation therapy (IMRT), beamlet intensity levels in fluence maps of high-energy photon beams are optimized. Treatment plan evaluation criteria are used as objective functions to steer the optimization process. Fluence map optimization can be considered a multi-objective optimization problem, for which a set of Pareto optimal solutions exists: the Pareto efficient frontier (PEF). In this paper, a constrained optimization method is pursued to iteratively estimate the PEF up to some predefined error. We use the property that the PEF is convex for a convex optimization problem to construct piecewise-linear upper and lower bounds to approximate the PEF from a small initial set of Pareto optimal plans. A derivative-free Sandwich algorithm is presented in which these bounds are used with three strategies to determine the location of the next Pareto optimal solution such that the uncertainty in the estimated PEF is maximally reduced. We show that an intelligent initial solution for a new Pareto optimal plan can be obtained by interpolation of fluence maps from neighbouring Pareto optimal plans. The method has been applied to a simplified clinical test case using two convex objective functions to map the trade-off between tumour dose heterogeneity and critical organ sparing. All three strategies produce representative estimates of the PEF. The new algorithm is particularly suitable for dynamic generation of Pareto optimal plans in interactive treatment planning.
Jenkins, Rob; Burton, A. Mike
2011-01-01
Photographs are often used to establish the identity of an individual or to verify that they are who they claim to be. Yet, recent research shows that it is surprisingly difficult to match a photo to a face. Neither humans nor machines can perform this task reliably. Although human perceivers are good at matching familiar faces, performance with unfamiliar faces is strikingly poor. The situation is no better for automatic face recognition systems. In practical settings, automatic systems have been consistently disappointing. In this review, we suggest that failure to distinguish between familiar and unfamiliar face processing has led to unrealistic expectations about face identification in applied settings. We also argue that a photograph is not necessarily a reliable indicator of facial appearance, and develop our proposal that summary statistics can provide more stable face representations. In particular, we show that image averaging stabilizes facial appearance by diluting aspects of the image that vary between snapshots of the same person. We review evidence that the resulting images can outperform photographs in both behavioural experiments and computer simulations, and outline promising directions for future research. PMID:21536553
NASA Astrophysics Data System (ADS)
Otani, Yousuke; Nitta, Kouichi; Matoba, Osamu
2014-09-01
The possibility of multi-valued optical disk memory by using a convex-shaped recording mark fabricated by two-photon absorption is investigated. We fabricate a numerical model for convex-shaped recording marks and evaluate the signal characteristics in terms of the signal-to-noise ratio (SNR). The numerical results show that 6 bit data can be realized when the acceptable average SNR is 2 and a length of the mark is 4T.
NASA Technical Reports Server (NTRS)
Dellacorte, Christopher (Inventor)
1999-01-01
A radial face seal arrangement is disclosed comprising a stationary seal ring that is spring loaded against a seal seat affixed to a rotating shaft. The radial face seal arrangement further comprises an arrangement that not only allows for preloading of the stationary seal ring relative to the seal seat, but also provides for dampening yielding a dynamic seating response for the radial face seal arrangement. The overall seal system, especially regarding the selection of the material for the stationary seal ring, is designed to operate over a wide temperature range from below ambient up to 900 C.
Cotton fabrics with single-faced superhydrophobicity.
Liu, Yuyang; Xin, J H; Choi, Chang-Hwan
2012-12-18
This article reports on the fabrication of cotton fabrics with single-faced superhydrophobicity using a simple foam finishing process. Unlike most commonly reported superhydrophobic fabrics, the fabrics developed in this study exhibit asymmetric wettability on their two faces: one face showing superhydrophobic behavior (highly nonwetting or water-repellent characteristics) and the other face retaining the inherent hydrophilic nature of cotton. The superhydrophobic face exhibits a low contact angle hysteresis of θ(a)/θ(r) = 151°/144° (θ(a), advancing contact angle; θ(r), receding contact angle), which enables water drops to roll off the surface easily so as to endow the surface with well-known self-cleaning properties. The untreated hydrophilic face preserves its water-absorbing capability, resulting in 44% of the water-absorbing capacity compared to that of the original cotton samples with both sides untreated (hydrophilic). The single-faced superhydrophobic fabrics also retain moisture transmissibility that is as good as that of the original untreated cotton fabrics. They also show robust washing fastness with the chemical cross-linking process of hydrophobic fluoropolymer to fabric fibers. Fabric materials with such asymmetric or gradient wettability will be of great use in many applications such as unidirectional liquid transporting, moisture management, microfluidic systems, desalination of seawater, flow management in fuel cells, and water/oil separation. PMID:23186211
NASA Astrophysics Data System (ADS)
Almeida, Pedro; Tomas, Ricardo; Rosas, Filipe; Duarte, Joao; Terrinha, Pedro
2015-04-01
Different modes of strain accommodation affecting a deformable hanging-wall in a flat-ramp-flat thrust system were previously addressed through several (sandbox) analog modeling studies, focusing on the influence of different variables, such as: a) thrust ramp dip angle and friction (Bonini et al, 2000); b) prescribed thickness of the hanging-wall (Koy and Maillot, 2007); and c) sin-thrust erosion (compensating for topographic thrust edification, e.g. Persson and Sokoutis, 2002). In the present work we reproduce the same experimental procedure to investigate the influence of two different parameters on hanging-wall deformation: 1) the geometry of the thrusting surface; and 2) the absence of a velocity discontinuity (VD) that is always present in previous similar analogue modeling studies. Considering the first variable we use two end member ramp geometries, flat-ramp-flat and convex-concave, to understand the control exerted by the abrupt ramp edges in the hanging-wall stress-strain distribution, comparing the obtain results with the situation in which such edge singularities are absent (convex-concave thrust ramp). Considering the second investigated parameter, our motivation was the recognition that the VD found in the different analogue modeling settings simply does not exist in nature, despite the fact that it has a major influence on strain accommodation in the deformable hanging-wall. We thus eliminate such apparatus artifact from our models and compare the obtained results with the previous ones. Our preliminary results suggest that both investigated variables play a non-negligible role on the structural style characterizing the hanging-wall deformation of convergent tectonic settings were such thrust-ramp systems were recognized. Acknowledgments This work was sponsored by the Fundação para a Ciência e a Tecnologia (FCT) through project MODELINK EXPL/GEO-GEO/0714/2013. Pedro Almeida wants to thank to FCT for the Ph.D. grant (SFRH/BD/52556/2014) under the
NASA Technical Reports Server (NTRS)
1981-01-01
Mask to protect the physically impaired from injuries to the face and head has been developed by Langley Research Center. It is made of composite materials, usually graphite or boron fibers woven into a matrix. Weighs less than three ounces.
NASA Astrophysics Data System (ADS)
Sauncy, Toni
2008-10-01
In keeping with its commitment to help students transform themselves into contributing members of the professional physics community, the Society of Physics Students National Council began efforts aimed at addressing issued of diversity in physics several years ago. One of the projects stemming from these discussions is the adoption of a 2008 theme ``The Future Faces of Physics.'' With this theme, the council aims to raise visibility and focus on issues of student diversity in physics. The initiative included the distribution of ``Future Faces of Physics Kits'' to any chapter hosting zone meetings. A highlight of the kit is the Future Faces of Physics Jeopardy set, which consists of buzzers, a score board, instructions, and a game board. The Future Faces of Physics game is a vehicle for generating discussion and raising awareness. The diversity session is hosted by the SPS Zone 13 and Zone 16 leadership.
Performance of the coned-face end seal with regard to energy conservation
NASA Technical Reports Server (NTRS)
Sehnal, J.; Sedy, J.; Zobens, A.; Etsion, I.
1982-01-01
The effects of face coning on seal performance are evaluated with particular regard to the energy saving potential of convex conedface end seals as indicated by torque reduction. Experiments were conducted using a conventional carbon flat-face pusher-type seal, a coned-face pusher-type seal, coned-face bellows-type seal, and a modified coned-face pusher-type seal intended for dynamically unstable operation, with shaft rotation at up to 8000 rpm, pressures of up to 2758 kPa, and a petroleum-based turbine oil as lubricant. Torque at the seal interface is found to be reduced by 42% when the standard flat-face seal is replaced by a coned seal, although the leakage of the cone-face seal was 11 times greater. Reduction of seal balance from 76.1 to 51.3% resulted in an additional 44% reduction in torque, although at the expense of excessive leakage, but did not produce unstable operation. Face temperatures were reduced by 33-56 C and wear was also reduced greatly on the cone face seals. Seal performance is noted to be in agreement with analytical calculations.
Temporal Networks of Face-to-Face Human Interactions
NASA Astrophysics Data System (ADS)
Barrat, Alain; Cattuto, Ciro
The ever increasing adoption of mobile technologies and ubiquitous services allows to sense human behavior at unprecedented levels of details and scale. Wearable sensors are opening up a new window on human mobility and proximity at the finest resolution of face-to-face proximity. As a consequence, empirical data describing social and behavioral networks are acquiring a longitudinal dimension that brings forth new challenges for analysis and modeling. Here we review recent work on the representation and analysis of temporal networks of face-to-face human proximity, based on large-scale datasets collected in the context of the SocioPatterns collaboration. We show that the raw behavioral data can be studied at various levels of coarse-graining, which turn out to be complementary to one another, with each level exposing different features of the underlying system. We briefly review a generative model of temporal contact networks that reproduces some statistical observables. Then, we shift our focus from surface statistical features to dynamical processes on empirical temporal networks. We discuss how simple dynamical processes can be used as probes to expose important features of the interaction patterns, such as burstiness and causal constraints. We show that simulating dynamical processes on empirical temporal networks can unveil differences between datasets that would otherwise look statistically similar. Moreover, we argue that, due to the temporal heterogeneity of human dynamics, in order to investigate the temporal properties of spreading processes it may be necessary to abandon the notion of wall-clock time in favour of an intrinsic notion of time for each individual node, defined in terms of its activity level. We conclude highlighting several open research questions raised by the nature of the data at hand.
Kircher, T T; Senior, C; Phillips, M L; Rabe-Hesketh, S; Benson, P J; Bullmore, E T; Brammer, M; Simmons, A; Bartels, M; David, A S
2001-01-01
We report two studies of facial self-perception using individually tailored, standardized facial photographs of a group of volunteers and their partners. A computerized morphing procedure was used to merge each target face with an unknown control face. In the first set of experiments, a discrimination task revealed a delayed response time for the more extensively morphed self-face stimuli. In a second set of experiments, functional magnetic resonance imaging (fMRI) was used to measure brain activation while subjects viewed morphed versions of either their own or their partner's face, alternating in blocks with presentation of an unknown face. When subjects viewed themselves (minus activation for viewing an unknown face), increased blood oxygenation was detected in right limbic (hippocampal formation, insula, anterior cingulate), left prefrontal cortex and superior temporal cortex. In the partner (versus unknown) experiment, only the right insula was activated. We suggest that a neural network involving the right hemisphere in conjunction with left-sided associative and executive regions underlies the process of visual self-recognition. Together, this combination produces the unique experience of self-awareness. PMID:11062324
Is Face Distinctiveness Gender Based?
ERIC Educational Resources Information Center
Baudouin, Jean-Yves; Gallay, Mathieu
2006-01-01
Two experiments were carried out to study the role of gender category in evaluations of face distinctiveness. In Experiment 1, participants had to evaluate the distinctiveness and the femininity-masculinity of real or artificial composite faces. The composite faces were created by blending either faces of the same gender (sexed composite faces,…
Successful Decoding of Famous Faces in the Fusiform Face Area
Axelrod, Vadim; Yovel, Galit
2015-01-01
What are the neural mechanisms of face recognition? It is believed that the network of face-selective areas, which spans the occipital, temporal, and frontal cortices, is important in face recognition. A number of previous studies indeed reported that face identity could be discriminated based on patterns of multivoxel activity in the fusiform face area and the anterior temporal lobe. However, given the difficulty in localizing the face-selective area in the anterior temporal lobe, its role in face recognition is still unknown. Furthermore, previous studies limited their analysis to occipito-temporal regions without testing identity decoding in more anterior face-selective regions, such as the amygdala and prefrontal cortex. In the current high-resolution functional Magnetic Resonance Imaging study, we systematically examined the decoding of the identity of famous faces in the temporo-frontal network of face-selective and adjacent non-face-selective regions. A special focus has been put on the face-area in the anterior temporal lobe, which was reliably localized using an optimized scanning protocol. We found that face-identity could be discriminated above chance level only in the fusiform face area. Our results corroborate the role of the fusiform face area in face recognition. Future studies are needed to further explore the role of the more recently discovered anterior face-selective areas in face recognition. PMID:25714434
Attention to Faces Modulates Early Face Processing during Low but not High Face Discriminability
Sreenivasan, Kartik K.; Goldstein, Jonathan M.; Lustig, Audrey G.; Rivas, Luis R.; Jha, Amishi P.
2010-01-01
In the present study, we investigated if attention to faces results in sensory gain modulation. Participants were cued to attend to faces or scenes in superimposed face-scene images while face discriminability was parametrically manipulated across images. The face-sensitive N170 event-related potential component was used as a measure of early face processing. Attention to faces modulated N170 amplitude, but only when faces were not highly discriminable. Additionally, directing attention to faces modulated later processing (~230–300 msec) for all discriminability levels. These results demonstrate that attention to faces can modulate perceptual processing of faces at multiple stages of processing, including early sensory levels. Critically, the early attentional benefit is present only when the “face signal” (i.e., the perceptual quality of the face) in the environment is suboptimal. PMID:19429962
How Well Do Computer-Generated Faces Tap Face Expertise?
Crookes, Kate; Ewing, Louise; Gildenhuys, Ju-dith; Kloth, Nadine; Hayward, William G.; Oxner, Matt; Pond, Stephen; Rhodes, Gillian
2015-01-01
The use of computer-generated (CG) stimuli in face processing research is proliferating due to the ease with which faces can be generated, standardised and manipulated. However there has been surprisingly little research into whether CG faces are processed in the same way as photographs of real faces. The present study assessed how well CG faces tap face identity expertise by investigating whether two indicators of face expertise are reduced for CG faces when compared to face photographs. These indicators were accuracy for identification of own-race faces and the other-race effect (ORE)–the well-established finding that own-race faces are recognised more accurately than other-race faces. In Experiment 1 Caucasian and Asian participants completed a recognition memory task for own- and other-race real and CG faces. Overall accuracy for own-race faces was dramatically reduced for CG compared to real faces and the ORE was significantly and substantially attenuated for CG faces. Experiment 2 investigated perceptual discrimination for own- and other-race real and CG faces with Caucasian and Asian participants. Here again, accuracy for own-race faces was significantly reduced for CG compared to real faces. However the ORE was not affected by format. Together these results signal that CG faces of the type tested here do not fully tap face expertise. Technological advancement may, in the future, produce CG faces that are equivalent to real photographs. Until then caution is advised when interpreting results obtained using CG faces. PMID:26535910
The CONVEX Liner Add-On to the DIAMOND-FORTUNE event
Heuze, F.E.; Swift, R.P.; Hill, L.R.; Barrett, W.H.
1993-11-15
This report describes the execution of the CONVEX Liner Add-On to the DIAMOND FORTUNE low-yield cavity test of the Defense Nuclear Agency. CONVEX stands for COntained Nuclear Vessel EXperiment. It concerns the design of underground chambers where repeated low-yield nuclear explosions could be conducted. The approach proposed by the first author in the early 1980`s was to engineer a steel-lined rock cavern where the steel liner would be prestressed against the rock by tendons and/or bolts. These would daylight in tunnels surrounding the main cavity. From there, they could be initially tensioned and retensioned, if needed, after each test. The CONVEX Liner Add-On to DIAMOND FORTUNE consisted of anchoring a 1.4-m square, 2.5-cm thick steel plate to the wall of the cavity, using a 5-cm diameter center bolt, and four 2.5-cm diameter comer bolts. The bolts daylighted in a drift surrounding the gallery, and separated from it by a 9-m thick rock pillar. The liner plate, the bolts, and the rock pillar were equipped with 23 gages to describe the thermal and mechanical response of the system during pretensioning, during the dynamic loading phase, and post-test. Particular emphasis was given to obtaining the response both upon loading and during the rebound of the system, in order to determine whether the plate ever separated from the rock. So, the main operational objectives of this project were to acquire response data of the system under nuclear loading and to ascertain the status of contact between the steel plate and the rock, as shown by toadstool data and bolt tension data. The instrumentation and data acquisition system performed extremely well. Data were recorded during the dynamic phase; plate temperature was monitored for several hours after the test; and the remaining tension was obtained for several bolts more than three months after the test, upon re-entry in the runaround drift.
Image restoration by the method of convex projections: part 1 theory.
Youla, D C; Webb, H
1982-01-01
A projection operator onto a closed convex set in Hilbert space is one of the few examples of a nonlinear map that can be defined in simple abstract terms. Moreover, it minimizes distance and is nonexpansive, and therefore shares two of the more important properties of ordinary linear orthogonal projections onto closed linear manifolds. In this paper, we exploit the properties of these operators to develop several iterative algorithms for image restoration from partial data which permit any number of nonlinear constraints of a certain type to be subsumed automatically. Their common conceptual basis is as follows. Every known property of an original image f is envisaged as restricting it to lie in a well-defined closed convex set. Thus, m such properties place f in the intersection E(0) = E(i) of the corresponding closed convex sets E(1),E(2),...EE(m). Given only the projection operators PE(i) onto the individual E(i)'s, i = 1 --> m, we restore f by recursive means. Clearly, in this approach, the realization of the P(i)'s in a Hilbert space setting is one of the major synthesis problems. Section I describes the geometrical significance of the three main theorems in considerable detail, and most of the underlying ideas are illustrated with the aid of simple diagrams. Section II presents rules for the numerical implementation of 11 specific projection operators which are found to occur frequently in many signal-processing applications, and the Appendix contains proofs of all the major results. PMID:18238261
Ambikapathi, ArulMurugan; Chan, Tsung-Han; Lin, Chia-Hsiang; Yang, Fei-Shih; Chi, Chong-Yung; Wang, Yue
2016-04-01
Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is a powerful imaging modality to study the pharmacokinetics in a suspected cancer/tumor tissue. The pharmacokinetic (PK) analysis of prostate cancer includes the estimation of time activity curves (TACs), and thereby, the corresponding kinetic parameters (KPs), and plays a pivotal role in diagnosis and prognosis of prostate cancer. In this paper, we endeavor to develop a blind source separation algorithm, namely convex-optimization-based KPs estimation (COKE) algorithm for PK analysis based on compartmental modeling of DCE-MRI data, for effective prostate tumor detection and its quantification. The COKE algorithm first identifies the best three representative pixels in the DCE-MRI data, corresponding to the plasma, fast-flow, and slow-flow TACs, respectively. The estimation accuracy of the flux rate constants (FRCs) of the fast-flow and slow-flow TACs directly affects the estimation accuracy of the KPs that provide the cancer and normal tissue distribution maps in the prostate region. The COKE algorithm wisely exploits the matrix structure (Toeplitz, lower triangular, and exponential decay) of the original nonconvex FRCs estimation problem, and reformulates it into two convex optimization problems that can reliably estimate the FRCs. After estimation of the FRCs, the KPs can be effectively estimated by solving a pixel-wise constrained curve-fitting (convex) problem. Simulation results demonstrate the efficacy of the proposed COKE algorithm. The COKE algorithm is also evaluated with DCE-MRI data of four different patients with prostate cancer and the obtained results are consistent with clinical observations. PMID:26292336
Dissipative issue of high-order shock capturing schemes with non-convex equations of state
NASA Astrophysics Data System (ADS)
Heuzé, Olivier; Jaouen, Stéphane; Jourdren, Hervé
2009-02-01
It is well known that, closed with a non-convex equation of state (EOS), the Riemann problem for the Euler equations allows non-standard waves, such as split shocks, sonic isentropic compressions or rarefaction shocks, to occur. Loss of convexity then leads to non-uniqueness of entropic or Lax solutions, which can only be resolved via the Liu-Oleinik criterion (equivalent to the existence of viscous profiles for all admissible shock waves). This suggests that in order to capture the physical solution, a numerical scheme must provide an appropriate level of dissipation. A legitimate question then concerns the ability of high-order shock capturing schemes to naturally select such a solution. To investigate this question and evaluate modern as well as future high-order numerical schemes, there is therefore a crucial need for well-documented benchmarks. A thermodynamically consistent C∞ non-convex EOS that can be easily introduced in Eulerian as well as Lagrangian hydrocodes for test purposes is here proposed, along with a reference solution for an initial value problem exhibiting a complex composite wave pattern (the Bizarrium test problem). Two standard Lagrangian numerical approaches, both based on a finite volume method, are then reviewed (vNR and Godunov-type schemes) and evaluated on this Riemann problem. In particular, a complete description of several state-of-the-art high-order Godunov-type schemes applicable to general EOSs is provided. We show that this particular test problem reveals quite severe when working on high-order schemes, and recommend it as a benchmark for devising new limiters and/or next-generation highly accurate schemes.
Convexity of Ruin Probability and Optimal Dividend Strategies for a General Lévy Process
Yin, Chuancun; Yuen, Kam Chuen; Shen, Ying
2015-01-01
We consider the optimal dividends problem for a company whose cash reserves follow a general Lévy process with certain positive jumps and arbitrary negative jumps. The objective is to find a policy which maximizes the expected discounted dividends until the time of ruin. Under appropriate conditions, we use some recent results in the theory of potential analysis of subordinators to obtain the convexity properties of probability of ruin. We present conditions under which the optimal dividend strategy, among all admissible ones, takes the form of a barrier strategy. PMID:26351655
NASA Astrophysics Data System (ADS)
An, Yulian; Kim, Chan-Gyun; Shi, Junping
2016-02-01
A p-Laplacian nonlinear elliptic equation with positive and p-superlinear nonlinearity and Dirichlet boundary condition is considered. We first prove the existence of two positive solutions when the spatial domain is symmetric or strictly convex by using a priori estimates and topological degree theory. For the ball domain in RN with N ≥ 4 and the case that 1 < p < 2, we prove that the equation has exactly two positive solutions when a parameter is less than a critical value. Bifurcation theory and linearization techniques are used in the proof of the second result.
Block clustering based on difference of convex functions (DC) programming and DC algorithms.
Le, Hoai Minh; Le Thi, Hoai An; Dinh, Tao Pham; Huynh, Van Ngai
2013-10-01
We investigate difference of convex functions (DC) programming and the DC algorithm (DCA) to solve the block clustering problem in the continuous framework, which traditionally requires solving a hard combinatorial optimization problem. DC reformulation techniques and exact penalty in DC programming are developed to build an appropriate equivalent DC program of the block clustering problem. They lead to an elegant and explicit DCA scheme for the resulting DC program. Computational experiments show the robustness and efficiency of the proposed algorithm and its superiority over standard algorithms such as two-mode K-means, two-mode fuzzy clustering, and block classification EM. PMID:23777526
The discrete one-sided Lipschitz condition for convex scalar conservation laws
NASA Technical Reports Server (NTRS)
Brenier, Yann; Osher, Stanley
1986-01-01
Physical solutions to convex scalar conservation laws satisfy a one-sided Lipschitz condition (OSLC) that enforces both the entropy condition and their variation boundedness. Consistency with this condition is therefore desirable for a numerical scheme and was proved for both the Godunov and the Lax-Friedrichs scheme--also, in a weakened version, for the Roe scheme, all of them being only first order accurate. A new, fully second order scheme is introduced here, which is consistent with the OSLC. The modified equation is considered and shows interesting features. Another second order scheme is then considered and numerical results are discussed.
Matrix coefficient identification in an elliptic equation with the convex energy functional method
NASA Astrophysics Data System (ADS)
Hinze, Michael; Nhan Tam Quyen, Tran
2016-08-01
In this paper we study the inverse problem of identifying the diffusion matrix in an elliptic PDE from measurements. The convex energy functional method with Tikhonov regularization is applied to tackle this problem. For the discretization we use the variational discretization concept, where the PDE is discretized with piecewise linear, continuous finite elements. We show the convergence of approximations. Using a suitable source condition, we prove an error bound for discrete solutions. For the numerical solution we propose a gradient-projection algorithm and prove the strong convergence of its iterates to a solution of the identification problem. Finally, we present a numerical experiment which illustrates our theoretical results.
Log-Log Convexity of Type-Token Growth in Zipf's Systems
NASA Astrophysics Data System (ADS)
Font-Clos, Francesc; Corral, Álvaro
2015-06-01
It is traditionally assumed that Zipf's law implies the power-law growth of the number of different elements with the total number of elements in a system—the so-called Heaps' law. We show that a careful definition of Zipf's law leads to the violation of Heaps' law in random systems, with growth curves that have a convex shape in log-log scale. These curves fulfill universal data collapse that only depends on the value of Zipf's exponent. We observe that real books behave very much in the same way as random systems, despite the presence of burstiness in word occurrence. We advance an explanation for this unexpected correspondence.
An imaging spectrometer with a convex crystal for pulsed x rays in plasma experiments
NASA Astrophysics Data System (ADS)
Yanagidaira, Takeshi; Shimoda, Katsuji; Ono, Yasushi; Hirano, Katsumi
2000-01-01
An imaging spectrometer with a convex rubidium acid phthalate (RbAP) crystal is designed and examined. Using the ray tracing technique based on the kinematical theory of diffraction, resolution power, dispersion, linearity, spatial resolution and dynamic range of the monochromatic image are discussed. Broadening by a rocking curve is also taken into account. Performance of the spectrometer is successfully examined using the so-called hot spots as the soft x-ray source which are generated in the pinched plasma by the plasma focus facility with an additional gas puff.
Metric-Adjusted Skew Information: Convexity and Restricted Forms of Superadditivity
NASA Astrophysics Data System (ADS)
Cai, Liang; Hansen, Frank
2010-07-01
We give a truly elementary proof of the convexity of metric-adjusted skew information following an idea of Effros. We extend earlier results of weak forms of superadditivity to general metric-adjusted skew information. Recently, Luo and Zhang introduced the notion of semi-quantum states on a bipartite system and proved superadditivity of the Wigner-Yanase-Dyson skew informations for such states. We extend this result to the general metric-adjusted skew information. We finally show that a recently introduced extension to parameter values 1 < p ≤ 2 of the WYD-information is a special case of (unbounded) metric-adjusted skew information.
Convex Non-Negative Matrix Factorization for Brain Tumor Delimitation from MRSI Data
Ortega-Martorell, Sandra; Lisboa, Paulo J. G.; Vellido, Alfredo; Simões, Rui V.; Pumarola, Martí; Julià-Sapé, Margarida; Arús, Carles
2012-01-01
Background Pattern Recognition techniques can provide invaluable insights in the field of neuro-oncology. This is because the clinical analysis of brain tumors requires the use of non-invasive methods that generate complex data in electronic format. Magnetic Resonance (MR), in the modalities of spectroscopy (MRS) and spectroscopic imaging (MRSI), has been widely applied to this purpose. The heterogeneity of the tissue in the brain volumes analyzed by MR remains a challenge in terms of pathological area delimitation. Methodology/Principal Findings A pre-clinical study was carried out using seven brain tumor-bearing mice. Imaging and spectroscopy information was acquired from the brain tissue. A methodology is proposed to extract tissue type-specific sources from these signals by applying Convex Non-negative Matrix Factorization (Convex-NMF). Its suitability for the delimitation of pathological brain area from MRSI is experimentally confirmed by comparing the images obtained with its application to selected target regions, and to the gold standard of registered histopathology data. The former showed good accuracy for the solid tumor region (proliferation index (PI)>30%). The latter yielded (i) high sensitivity and specificity in most cases, (ii) acquisition conditions for safe thresholds in tumor and non-tumor regions (PI>30% for solid tumoral region; ≤5% for non-tumor), and (iii) fairly good results when borderline pixels were considered. Conclusions/Significance The unsupervised nature of Convex-NMF, which does not use prior information regarding the tumor area for its delimitation, places this approach one step ahead of classical label-requiring supervised methods for discrimination between tissue types, minimizing the negative effect of using mislabeled voxels. Convex-NMF also relaxes the non-negativity constraints on the observed data, which allows for a natural representation of the MRSI signal. This should help radiologists to accurately tackle one of the
High-frequency electromagnetic scarring in three-dimensional axisymmetric convex cavities
Warne, Larry K.; Jorgenson, Roy E.
2016-04-13
Here, this article examines the localization of high-frequency electromagnetic fields in three-dimensional axisymmetric cavities along periodic paths between opposing sides of the cavity. When these orbits lead to unstable localized modes, they are known as scars. This article treats the case where the opposing sides, or mirrors, are convex. Particular attention is focused on the normalization through the electromagnetic energy theorem. Both projections of the field along the scarred orbit as well as field point statistics are examined. Statistical comparisons are made with a numerical calculation of the scars run with an axisymmetric simulation.
Computer aided surface representation
Barnhill, R E
1987-11-01
The aims of this research are the creation of new surface forms and the determination of geometric and physical properties of surfaces. The full sweep from constructive mathematics through the implementation of algorithms and the interactive computer graphics display of surfaces is utilized. Both three-dimensional and multi- dimensional surfaces are considered. Particular emphasis is given to the scientific computing solution of Department of Energy problems. The methods that we have developed and that we are proposing to develop allow applications such as: Producing smooth contour maps from measured data, such as weather maps. Modeling the heat distribution inside a furnace from sample measurements. Terrain modeling based on satellite pictures. The investigation of new surface forms includes the topics of triangular interpolants, multivariate interpolation, surfaces defined on surfaces and monotone and/or convex surfaces. The geometric and physical properties considered include contours, the intersection of surfaces, curvatures as a interrogation tool, and numerical integration.
Voicing on Virtual and Face to Face Discussion
ERIC Educational Resources Information Center
Yamat, Hamidah
2013-01-01
This paper presents and discusses findings of a study conducted on pre-service teachers' experiences in virtual and face to face discussions. Technology has brought learning nowadays beyond the classroom context or time zone. The learning context and process no longer rely solely on face to face communications in the presence of a teacher.…
Bayesian Face Recognition and Perceptual Narrowing in Face-Space
ERIC Educational Resources Information Center
Balas, Benjamin
2012-01-01
During the first year of life, infants' face recognition abilities are subject to "perceptual narrowing", the end result of which is that observers lose the ability to distinguish previously discriminable faces (e.g. other-race faces) from one another. Perceptual narrowing has been reported for faces of different species and different races, in…
Neural synchronization during face-to-face communication.
Jiang, Jing; Dai, Bohan; Peng, Danling; Zhu, Chaozhe; Liu, Li; Lu, Chunming
2012-11-01
Although the human brain may have evolutionarily adapted to face-to-face communication, other modes of communication, e.g., telephone and e-mail, increasingly dominate our modern daily life. This study examined the neural difference between face-to-face communication and other types of communication by simultaneously measuring two brains using a hyperscanning approach. The results showed a significant increase in the neural synchronization in the left inferior frontal cortex during a face-to-face dialog between partners but none during a back-to-back dialog, a face-to-face monologue, or a back-to-back monologue. Moreover, the neural synchronization between partners during the face-to-face dialog resulted primarily from the direct interactions between the partners, including multimodal sensory information integration and turn-taking behavior. The communicating behavior during the face-to-face dialog could be predicted accurately based on the neural synchronization level. These results suggest that face-to-face communication, particularly dialog, has special neural features that other types of communication do not have and that the neural synchronization between partners may underlie successful face-to-face communication. PMID:23136442
Pedagogical Characteristics of Online and Face-to-Face Classes
ERIC Educational Resources Information Center
Wuensch, Karl; Aziz, Shahnaz; Ozan, Erol; Kishore, Masao; Tabrizi, M. H. Nassehzadeh
2008-01-01
Currently, many students have had experience with both face-to-face and online classes. We asked such students at 46 different universities in the United States to evaluate the pedagogical characteristics of their most recently completed face-to-face class and their most recently completed online class. The results show that students rate online…
Neural correlates of face detection.
Xu, Xiaokun; Biederman, Irving
2014-06-01
Although face detection likely played an essential adaptive role in our evolutionary past and in contemporary social interactions, there have been few rigorous studies investigating its neural correlates. MJH, a prosopagnosic with bilateral lesions to the ventral temporal-occipital cortices encompassing the posterior face areas (fusiform and occipital face areas), expresses no subjective difficulty in face detection, suggesting that these posterior face areas do not mediate face detection exclusively. Despite his normal contrast sensitivity and visual acuity in foveal vision, the present study nevertheless revealed significant face detection deficits in MJH. Compared with controls, MJH showed a lower tolerance to noise in the phase spectrum for faces (vs. cars), reflected in his higher detection threshold for faces. MJH's lesions in bilateral occipito-temporal cortices thus appear to have produced a deficit not only in face individuation, but also in face detection. PMID:23365211
Dimpled/grooved face on a fuel injection nozzle body for flame stabilization and related method
Uhm, Jong Ho; Johnson, Thomas Edward; Kim, Kwanwoo; Zuo, Baifang
2013-08-20
A fuel injection head for a fuel nozzle used in a gas turbine combustor includes a substantially hollow body formed with an upstream end face, a downstream end face and a peripheral wall extending therebetween. A plurality of pre-mix tubes or passages extend axially through the hollow body with inlets at the upstream end face and outlets at the downstream end face. An exterior surface of the downstream end face is formed with three-dimensional surface features that increase a total surface area of the exterior surface as compared to a substantially flat, planar downstream end face.
NASA Astrophysics Data System (ADS)
Qiu, Zhiping; Wang, Xiaojun
2006-06-01
Two non-probabilistic, set-theoretical methods for determining the maximum and minimum impulsive responses of structures to uncertain-but-bounded impulses are presented. They are, respectively, based on the theories of interval mathematics and convex models. The uncertain-but-bounded impulses are assumed to be a convex set, hyper-rectangle or ellipsoid. For the two non-probabilistic methods, less prior information is required about the uncertain nature of impulses than the probabilistic model. Comparisons between the interval analysis method and the convex model, which are developed as an anti-optimization problem of finding the least favorable impulsive response and the most favorable impulsive response, are made through mathematical analyses and numerical calculations. The results of this study indicate that under the condition of the interval vector being determined from an ellipsoid containing the uncertain impulses, the width of the impulsive responses predicted by the interval analysis method is larger than that by the convex model; under the condition of the ellipsoid being determined from an interval vector containing the uncertain impulses, the width of the interval impulsive responses obtained by the interval analysis method is smaller than that by the convex model.
Pose estimation and frontal face detection for face recognition
NASA Astrophysics Data System (ADS)
Lim, Eng Thiam; Wang, Jiangang; Xie, Wei; Ronda, Venkarteswarlu
2005-05-01
This paper proposes a pose estimation and frontal face detection algorithm for face recognition. Considering it's application in a real-world environment, the algorithm has to be robust yet computationally efficient. The main contribution of this paper is the efficient face localization, scale and pose estimation using color models. Simulation results showed very low computational load when compare to other face detection algorithm. The second contribution is the introduction of low dimensional statistical face geometrical model. Compared to other statistical face model the proposed method models the face geometry efficiently. The algorithm is demonstrated on a real-time system. The simulation results indicate that the proposed algorithm is computationally efficient.
Simpson, Elizabeth A; Buchin, Zachary; Werner, Katie; Worrell, Rey; Jakobsen, Krisztina V
2014-11-01
We tested the specificity of human face search efficiency by examining whether there is a broad window of detection for various face-like stimuli-human and animal faces-or whether own-species faces receive greater attentional allocation. We assessed the strength of the own-species face detection bias by testing whether human faces are located more efficiently than other animal faces, when presented among various other species' faces, in heterogeneous 16-, 36-, and 64-item arrays. Across all array sizes, we found that, controlling for distractor type, human faces were located faster and more accurately than primate and mammal faces, and that, controlling for target type, searches were faster when distractors were human faces compared to animal faces, revealing more efficient processing of human faces regardless of their role as targets or distractors (Experiment 1). Critically, these effects remained when searches were for specific species' faces (human, chimpanzee, otter), ruling out a category-level explanation (Experiment 2). Together, these results suggest that human faces may be processed more efficiently than animal faces, both when task-relevant (targets) and task-irrelevant (distractors), even in direct competition with other faces. These results suggest that there is not a broad window of detection for all face-like patterns but that human adults process own-species' faces more efficiently than other species' faces. Such own-species search efficiencies may arise through experience with own-species faces throughout development or may be privileged early in development, due to the evolutionary importance of conspecifics' faces. PMID:25113852
Face recognition system and method using face pattern words and face pattern bytes
Zheng, Yufeng
2014-12-23
The present invention provides a novel system and method for identifying individuals and for face recognition utilizing facial features for face identification. The system and method of the invention comprise creating facial features or face patterns called face pattern words and face pattern bytes for face identification. The invention also provides for pattern recognitions for identification other than face recognition. The invention further provides a means for identifying individuals based on visible and/or thermal images of those individuals by utilizing computer software implemented by instructions on a computer or computer system and a computer readable medium containing instructions on a computer system for face recognition and identification.
Problems Facing Rural Schools.
ERIC Educational Resources Information Center
Stewart, C. E.; And Others
Problems facing rural Scottish schools range from short term consideration of daily operation to long term consideration of organizational alternatives. Addressed specifically, such problems include consideration of: (1) liaison between a secondary school and its feeder primary schools; (2) preservice teacher training for work in small, isolated…
NASA Astrophysics Data System (ADS)
Srinivasan, Aparna
2012-01-01
Restoration techniques are applied to degraded face samples. The techniques considered are those of Wiener Filtering, Lucy Richardson deconvolution, Blind deconvolution and Constrained least squares filtering (CLSF). Images degraded by low blur, high blur and low blur with noise are experimented with and the results are expounded.
NASA Astrophysics Data System (ADS)
Srinivasan, Aparna
2011-12-01
Restoration techniques are applied to degraded face samples. The techniques considered are those of Wiener Filtering, Lucy Richardson deconvolution, Blind deconvolution and Constrained least squares filtering (CLSF). Images degraded by low blur, high blur and low blur with noise are experimented with and the results are expounded.
Challenges Facing Special Education.
ERIC Educational Resources Information Center
Meyen, Edward L., Ed.; And Others
This book presents 17 selected papers from recent issues of the journal, "Focus on Exceptional Children," concerning current and emerging challenges facing the field of special education. The book is organized in two parts. Part 1, "Contemporary Challenges," includes the following articles: "Transitions in Early Childhood Special Education: Issues…
ERIC Educational Resources Information Center
1999
This document contains four symposium papers on work force issues facing human resource development (HRD). "Contributing Factors to the Success of Women and People of Color in Leadership Roles: A Message to HRD Professionals" (Jean R. McFarland, Gary Leske, Caroline S. V. Turner) reports the results of a survey in which nonwhite males, nonwhite…
NASA Technical Reports Server (NTRS)
Cason, W. E. I.; Baucom, R. M.; Evans, R. C.
1982-01-01
Lightweight face mask originally developed to protect epileptic patients during seizures could have many other medical and nonmedical applications such as muscular distrophy patients, football linesmen and riot-control police. Masks are extremely lightweight, the lightest of the configurations weighing only 136 grams.
ERIC Educational Resources Information Center
Stevens, Lori
2008-01-01
Visitors to the campus of Orland High School (OHS) will never question that they have stepped into a world of the masses: kids, activity, personalities, busyness, and playfulness--a veritable cloud of mild bedlam. The wall of ceramic faces that greets a visitor in the school office is another reminder of the organized chaos that the teachers…
ERIC Educational Resources Information Center
1995
These four papers are from a symposium facilitated by Eugene Andette on work force issues facing human resources development (HRD) at the 1995 Academy of Human Resource Development conference. "Meaning Construction and Personal Transformation: Alternative Dimensions of Job Loss" (Terri A. Deems) reports a study conducted to explore the ways…
TACOMA FACES SCHOOL SEGREGATION.
ERIC Educational Resources Information Center
HALEY, FRED T.
THE CHAIRMAN OF THE TACOMA, WASHINGTON, BOARD OF EDUCATION PRESENTS HIS VIEWS ON THE PROBLEMS TO BE FACED BY THE CITY OF TACOMA IN THE AREA OF DE FACTO SEGREGATION. TACOMA'S POPULATION FROM 1950 TO 1960 INCREASED 3 PERCENT. VIRTUALLY THE ENTIRE INCREASE WAS NONWHITE. IT IS HELD THAT THE MAGNITUDE OF THE EXPLOSIVE GROWTH OF THE NEGRO POPULATION IS…
ERIC Educational Resources Information Center
Zilliox, Joseph T.; Lowery, Shannon G.
1997-01-01
Describes an extended investigation of polygons and polyhedra which was conducted in response to a challenge posed in Focus, a newsletter from the Mathematical Association of America (MAA). Students were challenged to construct a polyhedron with faces that measure more than 13 inches to a side. Outlines the process, including the questions posed…
ERIC Educational Resources Information Center
Tennant, Roy
2007-01-01
In this article, the author talks about how to face the not knowing and offers a strategy to fill the gap of not knowing. In coping with constant change, he describes a strategy for library staff that might help in the absence of certainty. This includes: (a) guarding the data with one's life; (b) build not for longevity, but obsolescence; (c)…
A STRICTLY CONTRACTIVE PEACEMAN–RACHFORD SPLITTING METHOD FOR CONVEX PROGRAMMING
BINGSHENG, HE; LIU, HAN; WANG, ZHAORAN; YUAN, XIAOMING
2014-01-01
In this paper, we focus on the application of the Peaceman–Rachford splitting method (PRSM) to a convex minimization model with linear constraints and a separable objective function. Compared to the Douglas–Rachford splitting method (DRSM), another splitting method from which the alternating direction method of multipliers originates, PRSM requires more restrictive assumptions to ensure its convergence, while it is always faster whenever it is convergent. We first illustrate that the reason for this difference is that the iterative sequence generated by DRSM is strictly contractive, while that generated by PRSM is only contractive with respect to the solution set of the model. With only the convexity assumption on the objective function of the model under consideration, the convergence of PRSM is not guaranteed. But for this case, we show that the first t iterations of PRSM still enable us to find an approximate solution with an accuracy of O(1/t). A worst-case O(1/t) convergence rate of PRSM in the ergodic sense is thus established under mild assumptions. After that, we suggest attaching an underdetermined relaxation factor with PRSM to guarantee the strict contraction of its iterative sequence and thus propose a strictly contractive PRSM. A worst-case O(1/t) convergence rate of this strictly contractive PRSM in a nonergodic sense is established. We show the numerical efficiency of the strictly contractive PRSM by some applications in statistical learning and image processing. PMID:25620862
SiO2 nanofluid planar jet impingement cooling on a convex heated plate
NASA Astrophysics Data System (ADS)
Asghari Lafmajani, Neda; Ebrahimi Bidhendi, Mahsa; Ashjaee, Mehdi
2016-02-01
The main objective of this paper is to investigate the heat transfer coefficient of a planar jet of SiO2 nanofluid that impinges vertically on the middle of a convex heated plate for cooling purposes. The planar jet issues from a rectangular slot nozzle. The convex aluminum plate has a thickness, width and length of 0.2, 40 and 130 mm, respectively, and is bent with a radius of 200 mm. A constant heat-flux condition is employed. 7 nm SiO2 particles are added to water to prepare the nanofluid with 0.1, 1 and 2 % (ml SiO2/ml H2O) concentrations. The tests are also performed at different Reynolds numbers from 1803 to 2782. Results indicate that adding the SiO2 nanoparticles can effectively increase both local and average heat transfer coefficients up to 39.37 and 32.78 %, respectively. These positive effects often are more pronounced with increasing Reynolds numbers. This enhancement increases with ascending the concentration of nanofluid, especially from 0.1 to 1 %.
Simulation of stochastic systems via polynomial chaos expansions and convex optimization
NASA Astrophysics Data System (ADS)
Fagiano, Lorenzo; Khammash, Mustafa
2012-09-01
Polynomial chaos expansions represent a powerful tool to simulate stochastic models of dynamical systems. Yet, deriving the expansion's coefficients for complex systems might require a significant and nontrivial manipulation of the model, or the computation of large numbers of simulation runs, rendering the approach too time consuming and impracticable for applications with more than a handful of random variables. We introduce a computationally tractable technique for computing the coefficients of polynomial chaos expansions. The approach exploits a regularization technique with a particular choice of weighting matrices, which allows to take into account the specific features of polynomial chaos expansions. The method, completely based on convex optimization, can be applied to problems with a large number of random variables and uses a modest number of Monte Carlo simulations, while avoiding model manipulations. Additional information on the stochastic process, when available, can be also incorporated in the approach by means of convex constraints. We show the effectiveness of the proposed technique in three applications in diverse fields, including the analysis of a nonlinear electric circuit, a chaotic model of organizational behavior, and finally a chemical oscillator.
A new volume conservation enforcement method for PLIC reconstruction in general convex grids
NASA Astrophysics Data System (ADS)
López, J.; Hernández, J.; Gómez, P.; Faura, F.
2016-07-01
A comprehensive study is made of methods for resolving the volume conservation enforcement problem in the PLIC reconstruction of an interface in general 3D convex grids. Different procedures to bracket the solution when solving the problem using previous standard methods are analyzed in detail. A new interpolation bracketing procedure and an improved analytical method to find the interface plane constant are proposed. These techniques are combined in a new method to enforce volume conservation, which does not require the sequential polyhedra truncation operations typically used in standard methods. The new methods have been implemented into existing geometrical routines described in López and Hernández [15], which are further improved by using more efficient formulae to compute areas and volumes of general convex 2 and 3D polytopes. Different tests using regular and irregular cell geometries are carried out to demonstrate the robustness and substantial improvement in computational efficiency of the proposed techniques, which increase the computation speed of the mentioned routines by up to 3 times for the 3D problems considered in this work.
2D x-ray imaging spectroscopic diagnostics using convex bent crystal
NASA Astrophysics Data System (ADS)
Papp, Daniel; Presura, Radu; Wallace, Matt; Largent, Billy; Haque, Showera; Arias, Angel; Khanal, Vijay; Ivanov, Vladimir
2013-10-01
A new 2-dimensional time-integrated x-ray spectroscopic diagnostics technique was developed to create multi-monochromatic images of high-energy density Al plasmas. 2-dimensional is an advanced spectroscopic tool, providing a way to determine the spatial dependence of plasma temperature and density (Te and ne) in hot plasmas. The new technique uses the strong source broadening of convex cylindrically bent KAP crystal spectrometers, which contains spatial information along the dispersive direction. The perpendicular direction is imaged using a slit. The spatial resolution of the method is improved by the deconvolution of the source broadened line profiles from the lineshapes (recorded by the convex crystal spectrometer) with lineshapes of minimum instrumental broadening. The latter spectra were recorded with a concave cylindrically bent KAP crystal spectrometer, based on the Johann geometry. Spectroscopic model of the plasma x-ray emission was developed using the PrismSPECT code. The identification of suitable spectral features allows deriving Te and ne from line intensities. We applied this model to get temperature and density distribution maps for wire array z-pinch plasmas. Work supported by the DOE/NNSA under grant DE-NA0001834 and Cooperative Agreement DE-FC52-06NA27616.
Development of testing convex hyperbolic mirror using Hindle method based on stitching technology
NASA Astrophysics Data System (ADS)
Jiang, Zi-bo; Li, Xin-nan; Ji, Bo
2012-09-01
The test method of Large-diameter convex secondary mirror in development process is the key to making large telescope technology. Classical means HINDLE to test using of non - aberration points needs a spherical reflecting mirror which larger than the secondary mirror several times. This new Hindle test method based on stitching technology can significantly reduce their standard mirror's size, drop the difficulty of processing and cut down the costs. In This paper, the Hindle testing basic principles which base on stitching technology is introduced firstly, then principle of stitching and least square method. Following the parameters of inside and outside standard mirrors are derived. Then translation and rotation transformation algorithm of different sub-aperture interferometer array data is given. Finally the preliminary results of the radial stitching experiments are given. The results showed that the relative error is RMS = 6.1%, PV = 5.11%. With improving and perfection, this method can be used in the E-ELT, CFGT convex secondary mirror telescope test.
Enhancements on the Convex Programming Based Powered Descent Guidance Algorithm for Mars Landing
NASA Technical Reports Server (NTRS)
Acikmese, Behcet; Blackmore, Lars; Scharf, Daniel P.; Wolf, Aron
2008-01-01
In this paper, we present enhancements on the powered descent guidance algorithm developed for Mars pinpoint landing. The guidance algorithm solves the powered descent minimum fuel trajectory optimization problem via a direct numerical method. Our main contribution is to formulate the trajectory optimization problem, which has nonconvex control constraints, as a finite dimensional convex optimization problem, specifically as a finite dimensional second order cone programming (SOCP) problem. SOCP is a subclass of convex programming, and there are efficient SOCP solvers with deterministic convergence properties. Hence, the resulting guidance algorithm can potentially be implemented onboard a spacecraft for real-time applications. Particularly, this paper discusses the algorithmic improvements obtained by: (i) Using an efficient approach to choose the optimal time-of-flight; (ii) Using a computationally inexpensive way to detect the feasibility/ infeasibility of the problem due to the thrust-to-weight constraint; (iii) Incorporating the rotation rate of the planet into the problem formulation; (iv) Developing additional constraints on the position and velocity to guarantee no-subsurface flight between the time samples of the temporal discretization; (v) Developing a fuel-limited targeting algorithm; (vi) Initial result on developing an onboard table lookup method to obtain almost fuel optimal solutions in real-time.
NASA Astrophysics Data System (ADS)
Sumin, M. I.
2014-01-01
A parametric convex programming problem with an operator equality constraint and a finite set of functional inequality constraints is considered in a Hilbert space. The instability of this problem and, as a consequence, the instability of the classical Lagrange principle for it is closely related to its regularity and the subdifferentiability properties of the value function in the optimization problem. A sequential Lagrange principle in nondifferential form is proved for the indicated convex programming problem. The principle is stable with respect to errors in the initial data and covers the normal, regular, and abnormal cases of the problem and the case where the classical Lagrange principle does not hold. It is shown that the classical Lagrange principle in this problem can be naturally treated as a limiting variant of its stable sequential counterpart. The possibility of using the stable sequential Lagrange principle for directly solving unstable optimal control problems and inverse problems is discussed. For two illustrative problems of these kinds, the corresponding stable Lagrange principles are formulated in sequential form.
Convex Decompositions of Thermal Equilibrium for Non-interacting Non-relativistic Particles
NASA Astrophysics Data System (ADS)
Chenu, Aurelia; Branczyk, Agata; Sipe, John
2016-05-01
We provide convex decompositions of thermal equilibrium for non-interacting non-relativistic particles in terms of localized wave packets. These quantum representations offer a new tool and provide insights that can help relate to the classical picture. Considering that thermal states are ubiquitous in a wide diversity of fields, studying different convex decompositions of the canonical ensemble is an interesting problem by itself. The usual classical and quantum pictures of thermal equilibrium of N non-interacting, non-relativistic particles in a box of volume V are quite different. The picture in classical statistical mechanics is about (localized) particles with a range of positions and velocities; in quantum statistical mechanics, one considers the particles (bosons or fermions) associated with energy eigenstates that are delocalized through the whole box. Here we provide a representation of thermal equilibrium in quantum statistical mechanics involving wave packets with a localized coordinate representation and an expectation value of velocity. In addition to derive a formalism that may help simplify particular calculations, our results can be expected to provide insights into the transition from quantum to classical features of the fully quantum thermal state.
Arnold diffusion for smooth convex systems of two and a half degrees of freedom
NASA Astrophysics Data System (ADS)
Kaloshin, V.; Zhang, K.
2015-08-01
In the present note we announce a proof of a strong form of Arnold diffusion for smooth convex Hamiltonian systems. Let { T}2 be a 2-dimensional torus and B2 be the unit ball around the origin in { R}2 . Fix ρ > 0. Our main result says that for a ‘generic’ time-periodic perturbation of an integrable system of two degrees of freedom H_0(p)+\\varepsilon H_1(θ,p,t),\\quad θ\\in { T}^2, p\\in B^2, t\\in { T}={ R}/{ Z} , with a strictly convex H0, there exists a ρ-dense orbit (θε, pε, t)(t) in { T}2 × B2 × { T} , namely, a ρ-neighborhood of the orbit contains { T}2 × B2 × { T} . Our proof is a combination of geometric and variational methods. The fundamental elements of the construction are the usage of crumpled normally hyperbolic invariant cylinders from [9], flower and simple normally hyperbolic invariant manifolds from [36] as well as their kissing property at a strong double resonance. This allows us to build a ‘connected’ net of three-dimensional normally hyperbolic invariant manifolds. To construct diffusing orbits along this net we employ a version of the Mather variational method [41] equipped with weak KAM theory [28], proposed by Bernard in [7].
An Intriguing Convex Break in the EGRET SED of Mrk 421
NASA Technical Reports Server (NTRS)
Nandikotkur, Giridhar; Jahoda, Keith M.; Georganopoulos, M.; Hartman, R. C.; Mukherjee, R.; Thompson, D. J.; Swank, Jean H.
2007-01-01
Based upon analysis of the entire EGRET data from Mrk 421, it is found that the time-averaged spectra are inconsistent with the predictions of current theoretical models that have had success in describing simultaneous X-ray/TeV observations, and suggest additional components in the GeV band, as well as complex time variability. Current theoretical pictures explain the GeV emission as comptonization of the synchrotron photons in the jet, and predict hard spectra that should join smoothly with the TeV emission. Our analysis shows that the situation is more complex. The spectrum ranges from hard to soft during individual epochs, and shows a convext break in the aggregated data. We also present the mission-averaged EGRET spectrum for PKS 2155-304, which shows a similar (but not as pronounced) convex curvature. We discuss a series of possible explanations for the 10(exp 22) - 10(exp 23) HZ declining part of the EGRET nu F(sub nu), spectrum for Mrk 421, and suggest that it is synchrotron emission from the high energy tail of the electron population that produces the X-rays during the highest X-ray states. Such multi-MeV photons are produced by electrons accelerated close to the limit of diffusive shock acceleration. Simultaneous GLAST and X-ray observations of high X-ray states will address the issue of the convex curvature in the future.
An interface reconstruction method based on an analytical formula for 3D arbitrary convex cells
NASA Astrophysics Data System (ADS)
Diot, Steven; François, Marianne M.
2016-01-01
In this paper, we are interested in an interface reconstruction method for 3D arbitrary convex cells that could be used in multi-material flow simulations for instance. We assume that the interface is represented by a plane whose normal vector is known and we focus on the volume-matching step that consists in finding the plane constant so that it splits the cell according to a given volume fraction. We follow the same approach as in the recent authors' publication for 2D arbitrary convex cells in planar and axisymmetrical geometries, namely we derive an analytical formula for the volume of the specific prismatoids obtained when decomposing the cell using the planes that are parallel to the interface and passing through all the cell nodes. This formula is used to bracket the interface plane constant such that the volume-matching problem is rewritten in a single prismatoid in which the same formula is used to find the final solution. The proposed method is tested against an important number of reproducible configurations and shown to be at least five times faster.
An assessment of acoustic contrast between long and short vowels using convex hulls.
Haynes, Erin F; Taylor, Michael
2014-08-01
An alternative to the spectral overlap assessment metric (SOAM), first introduced by Wassink [(2006). J. Acoust. Soc. Am. 119(4), 2334-2350], is introduced. The SOAM quantifies the intra- and inter-language differences between long-short vowel pairs through a comparison of spectral (F1, F2) and temporal properties modeled with best fit ellipses (F1 × F2 space) and ellipsoids (F1 × F2 × duration). However, the SOAM ellipses and ellipsoids rely on a Gaussian distribution of vowel data and a dense dataset, neither of which can be assumed in endangered languages or languages with limited available data. The method presented in this paper, called the Vowel Overlap Assessment with Convex Hulls (VOACH) method, improves upon the earlier metric through the use of best-fit convex shapes. The VOACH method reduces the incorporation of "empty" data into calculations of vowel space. Both methods are applied to Numu (Oregon Northern Paiute), an endangered language of the western United States. Calculations from the VOACH method suggest that Numu is a primary quantity language, a result that is well aligned with impressionistic analyses of spectral and durational data from the language and with observations by field researchers. PMID:25096122
Airborne gravimetry data sparse reconstruction via L1-norm convex quadratic programming
NASA Astrophysics Data System (ADS)
Yang, Ya-Peng; Wu, Mei-Ping; Tang, Gang
2015-06-01
In practice, airborne gravimetry is a sub-Nyquist sampling method because of the restrictions imposed by national boundaries, financial cost, and database size. In this study, we analyze the sparsity of airborne gravimetry data by using the discrete Fourier transform and propose a reconstruction method based on the theory of compressed sensing for large-scale gravity anomaly data. Consequently, the reconstruction of the gravity anomaly data is transformed to a L1-norm convex quadratic programming problem. We combine the preconditioned conjugate gradient algorithm (PCG) and the improved interior-point method (IPM) to solve the convex quadratic programming problem. Furthermore, a flight test was carried out with the homegrown strapdown airborne gravimeter SGA-WZ. Subsequently, we reconstructed the gravity anomaly data of the flight test, and then, we compared the proposed method with the linear interpolation method, which is commonly used in airborne gravimetry. The test results show that the PCG-IPM algorithm can be used to reconstruct large-scale gravity anomaly data with higher accuracy and more effectiveness than the linear interpolation method.
NASA Astrophysics Data System (ADS)
Ballandras, S.; Gavignet, E.; Bigler, E.
1995-09-01
A theoretical model has been implemented to study surface transverse waves propagating on piezoelectric plates of finite thickness with thin metal strip gratings on both sides. Calculations have been performed for AT-cuts of quartz of thickness varying from 140 to 120 μm. The spatial period of the gratings was fixed to 20 μm (acoustic wavelength equal to 40 μm). The dispersion curve relating the angular frequency to the wavenumber presents more than one stopband as found in the usual analyses on semi-infinite substrates. These multiple high-frequency stopbands allow to design and realize high stability resonators or highly sensitive sensors for gravimetry, accelerometer applications, etc. Un modèle théorique a été mis en œuvre pour l'étude des propriétés des ondes de surface transverses se propageant sur des plaques piézoélectriques d'épaisseur finie avec des réseaux de fines bandes métalliques déposés sur chaque face. Les calculs ont été effectués pour des plaques de quartz voisines de la coupe AT et d'épaisseur variant de 140 à 120 μm. La périodicité des réseaux en regard a été fixée à 20 μm (longueur d'onde acoustique 40 μm). La courbe de dispersion reliant la pulsation au nombre d'ondes présente plusieurs bandes d'arrêt incluant celle habituellement mise en évidence pour un substrat semi-infini. L'existence de ces multiples bandes d'arrêt haute fréquence ouvre de nouvelles perspectives pour la réalisation de résonateurs ultrastables ou de capteurs de très grande sensibilité gravimétrique, accélérométrique, etc.
The Caledonian face test: A new test of face discrimination.
Logan, Andrew J; Wilkinson, Frances; Wilson, Hugh R; Gordon, Gael E; Loffler, Gunter
2016-02-01
This study aimed to develop a clinical test of face perception which is applicable to a wide range of patients and can capture normal variability. The Caledonian face test utilises synthetic faces which combine simplicity with sufficient realism to permit individual identification. Face discrimination thresholds (i.e. minimum difference between faces required for accurate discrimination) were determined in an "odd-one-out" task. The difference between faces was controlled by an adaptive QUEST procedure. A broad range of face discrimination sensitivity was determined from a group (N=52) of young adults (mean 5.75%; SD 1.18; range 3.33-8.84%). The test is fast (3-4min), repeatable (test-re-test r(2)=0.795) and demonstrates a significant inversion effect. The potential to identify impairments of face discrimination was evaluated by testing LM who reported a lifelong difficulty with face perception. While LM's impairment for two established face tests was close to the criterion for significance (Z-scores of -2.20 and -2.27) for the Caledonian face test, her Z-score was -7.26, implying a more than threefold higher sensitivity. The new face test provides a quantifiable and repeatable assessment of face discrimination ability. The enhanced sensitivity suggests that the Caledonian face test may be capable of detecting more subtle impairments of face perception than available tests. PMID:26607479
Parvizi, A; Van den Broek, W; Koch, C T
2016-04-18
The transport of intensity equation (TIE) is widely applied for recovering wave fronts from an intensity measurement and a measurement of its variation along the direction of propagation. In order to get around the problem of non-uniqueness and ill-conditionedness of the solution of the TIE in the very common case of unspecified boundary conditions or noisy data, additional constraints to the solution are necessary. Although from a numerical optimization point of view, convex constraint as imposed to by total variation minimization is preferable, we will show that in many cases non-convex constraints are necessary to overcome the low-frequency artifacts so typical for convex constraints. We will provide simulated and experimental examples that demonstrate the superiority of solutions to the TIE obtained by our recently introduced gradient flipping algorithm over a total variation constrained solution. PMID:27137272
NASA Technical Reports Server (NTRS)
Olariu, S.; Schwing, J.; Zhang, J.
1991-01-01
A bus system that can change dynamically to suit computational needs is referred to as reconfigurable. We present a fast adaptive convex hull algorithm on a two-dimensional processor array with a reconfigurable bus system (2-D PARBS, for short). Specifically, we show that computing the convex hull of a planar set of n points taken O(log n/log m) time on a 2-D PARBS of size mn x n with 3 less than or equal to m less than or equal to n. Our result implies that the convex hull of n points in the plane can be computed in O(1) time in a 2-D PARBS of size n(exp 1.5) x n.
NASA Astrophysics Data System (ADS)
Chen, Shibing; Wang, Xu-Jia
2016-01-01
In this paper we prove the strict c-convexity and the C 1, α regularity for potential functions in optimal transportation under condition (A3w). These results were obtained by Caffarelli [1,3,4] for the cost c (x, y) =| x - y | 2, by Liu [11], Loeper [15], Trudinger and Wang [20] for costs satisfying the condition (A3). For costs satisfying the condition (A3w), the results have also been proved by Figalli, Kim, and McCann [6], assuming that the initial and target domains are uniformly c-convex, see also [21]; and by Guillen and Kitagawa [8], assuming the cost function satisfies A3w in larger domains. In this paper we prove the strict c-convexity and the C 1, α regularity assuming either the support of source density is compactly contained in a larger domain where the cost function satisfies A3w, or the dimension 2 ≤ n ≤ 4.
Nursing student experiences with face-to-face learning.
Gruendemann, Barbara J
2011-12-01
Face-to-face learning has been the mainstay of nursing student learning. Despite moves to online learning, face-to-face learning persists. This study focuses on how nursing students experience face-to-face learning and why it not only survives, but thrives. This study was anchored in a hermeneutic phenomenological approach, with Gadamerian concepts and van Manen's lifeworlds as frameworks to understand students' experiences of face-to-face learning. Patterns and themes were extracted from audiore-corded face-to-face interviews. Participants confirmed that face-to-face learning continues to be valued as a strong methodology in nursing education. Their experiences focused on humanism, the importance of "presence," physical proximity, classroom as "the real thing," immediacy of feedback, and learning and knowing by human connections and interaction. The study findings were a rich source for understanding how nursing students process learning experiences. Increased understanding of the meaning and essence of face-to-face learning is essential as we decide how nursing content will be taught. PMID:21956259
Tessier, P
1989-01-01
The "facial mask" is composed of all of the tissues lying on top of the skeleton: periosteum, deep adipose tissue, superficial musculo-aponeurotic tissue and skin. The periosteum is the intermediate zone between the skeleton, responsible for the shape of the face, and the more superficial tissues which complete the shapes and, most importantly, represent the mobile part of the face and consequently the site of facial expression. The secret of an effective "mask-lift" depends on complete subperiosteal dissection of the malar bones, zygomatic arches and orbital margins. This dissection can be performed via a coronal approach, but it is easier to start the subperiosteal dissection via a short vestibular incision. Subperiosteal dissection via a coronal incision is not only useful to lift the facial mask; it is also useful for remodelling the orbital margins and to obtain bone grafts from the parietal area in order to reinforce the glabella, check bones and nasogenial folds. PMID:2473674
NASA Technical Reports Server (NTRS)
Baumgardner, Darrel; Kok, Greg; Anderson, Bruce
2004-01-01
Droplet Measurement Technologies (DMT), under funding from NASA, participated in the CRYSTAL/FACE field campaign in July, 2002 with measurements of cirrus cloud hydrometeors in the size range from 0.5 to 1600 microns. The measurements were made with the DMT Cloud, Aerosol and Precipitation Spectrometer (CAPS) that was flown on NASA's WB57F. With the exception of the first research flight when the data system failed two hours into the mission, the measurement system performed almost flawlessly during the thirteen flights. The measurements from the CAPS have been essential for interpretation of cirrus cloud properties and their impact on climate. The CAPS data set has been used extensively by the CRYSTAL/FACE investigators and as of the date of this report, have been included in five published research articles, 10 conference presentations and six other journal articles currently in preparation.
Goold, Jessica E.; Meng, Ming
2016-01-01
Faces spontaneously capture attention. However, which special attributes of a face underlie this effect is unclear. To address this question, we investigate how gist information, specific visual properties and differing amounts of experience with faces affect the time required to detect a face. Three visual search experiments were conducted investigating the rapidness of human observers to detect Mooney face images. Mooney images are two-toned, ambiguous images. They were used in order to have stimuli that maintain gist information but limit low-level image properties. Results from the experiments show: (1) Although upright Mooney faces were searched inefficiently, they were detected more rapidly than inverted Mooney face targets, demonstrating the important role of gist information in guiding attention toward a face. (2) Several specific Mooney face identities were searched efficiently while others were not, suggesting the involvement of specific visual properties in face detection. (3) By providing participants with unambiguous gray-scale versions of the Mooney face targets prior to the visual search task, the targets were detected significantly more efficiently, suggesting that prior experience with Mooney faces improves the ability to extract gist information for rapid face detection. However, a week of training with Mooney face categorization did not lead to even more efficient visual search of Mooney face targets. In summary, these results reveal that specific local image properties cannot account for how faces capture attention. On the other hand, gist information alone cannot account for how faces capture attention either. Prior experience facilitates the effect of gist on visual search of faces; making faces a special object category for guiding attention. PMID:26903941
Zhao, Mintao; Bülthoff, Heinrich H.; Bülthoff, Isabelle
2016-01-01
Holistic processing—the tendency to perceive objects as indecomposable wholes—has long been viewed as a process specific to faces or objects of expertise. Although current theories differ in what causes holistic processing, they share a fundamental constraint for its generalization: Nonface objects cannot elicit facelike holistic processing in the absence of expertise. Contrary to this prevailing view, here we show that line patterns with salient Gestalt information (i.e., connectedness, closure, and continuity between parts) can be processed as holistically as faces without any training. Moreover, weakening the saliency of Gestalt information in these patterns reduced holistic processing of them, which indicates that Gestalt information plays a crucial role in holistic processing. Therefore, holistic processing can be achieved not only via a top-down route based on expertise, but also via a bottom-up route relying merely on object-based information. The finding that facelike holistic processing can extend beyond the domains of faces and objects of expertise poses a challenge to current dominant theories. PMID:26674129
Iterative closest normal point for 3D face recognition.
Mohammadzade, Hoda; Hatzinakos, Dimitrios
2013-02-01
The common approach for 3D face recognition is to register a probe face to each of the gallery faces and then calculate the sum of the distances between their points. This approach is computationally expensive and sensitive to facial expression variation. In this paper, we introduce the iterative closest normal point method for finding the corresponding points between a generic reference face and every input face. The proposed correspondence finding method samples a set of points for each face, denoted as the closest normal points. These points are effectively aligned across all faces, enabling effective application of discriminant analysis methods for 3D face recognition. As a result, the expression variation problem is addressed by minimizing the within-class variability of the face samples while maximizing the between-class variability. As an important conclusion, we show that the surface normal vectors of the face at the sampled points contain more discriminatory information than the coordinates of the points. We have performed comprehensive experiments on the Face Recognition Grand Challenge database, which is presently the largest available 3D face database. We have achieved verification rates of 99.6 and 99.2 percent at a false acceptance rate of 0.1 percent for the all versus all and ROC III experiments, respectively, which, to the best of our knowledge, have seven and four times less error rates, respectively, compared to the best existing methods on this database. PMID:22585097
Face-space: A unifying concept in face recognition research.
Valentine, Tim; Lewis, Michael B; Hills, Peter J
2016-10-01
The concept of a multidimensional psychological space, in which faces can be represented according to their perceived properties, is fundamental to the modern theorist in face processing. Yet the idea was not clearly expressed until 1991. The background that led to the development of face-space is explained, and its continuing influence on theories of face processing is discussed. Research that has explored the properties of the face-space and sought to understand caricature, including facial adaptation paradigms, is reviewed. Face-space as a theoretical framework for understanding the effect of ethnicity and the development of face recognition is evaluated. Finally, two applications of face-space in the forensic setting are discussed. From initially being presented as a model to explain distinctiveness, inversion, and the effect of ethnicity, face-space has become a central pillar in many aspects of face processing. It is currently being developed to help us understand adaptation effects with faces. While being in principle a simple concept, face-space has shaped, and continues to shape, our understanding of face perception. PMID:25427883
Age-Dependent Face Detection and Face Categorization Performance
Carbon, Claus-Christian; Grüter, Martina; Grüter, Thomas
2013-01-01
Empirical studies on the development of face processing skills with age show inconsistent patterns concerning qualitative vs. quantitative changes over time or the age range for peak cognitive performance. In the present study, we tested the proficiency in face detection and face categorization with a large sample of participants (N = 312; age range: 2-88 yrs). As test objects, we used so-called Mooney faces, two-tone (black and white) images of faces lacking critical information of a local, featural and relational nature, reflecting difficult real world face processing conditions. We found that performance in the assessment of gender and age from Mooney faces increases up to about age 15, and decreases from 65 years on. The implications of these findings are discussed in the light of classic and recent findings from face development literature. PMID:24116236
9. WEST FACE OF OLD THEODOLITE BUILDING; WEST FACE OF ...
9. WEST FACE OF OLD THEODOLITE BUILDING; WEST FACE OF EAST PHOTO TOWER IN BACKGROUND - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 East, Napa & Alden Roads, Lompoc, Santa Barbara County, CA
Designing convex repulsive pair potentials that favor assembly of kagome and snub square lattices
NASA Astrophysics Data System (ADS)
Piñeros, William D.; Baldea, Michael; Truskett, Thomas M.
2016-08-01
Building on a recently introduced inverse strategy, isotropic and convex repulsive pair potentials were designed that favor assembly of particles into kagome and equilateral snub square lattices. The former interactions were obtained by a numerical solution of a variational problem that maximizes the range of density for which the ground state of the potential is the kagome lattice. Similar optimizations targeting the snub square lattice were also carried out, employing a constraint that required a minimum chemical potential advantage of the target over select competing structures. This constraint helped to discover isotropic interactions that meaningfully favored the snub square lattice as the ground state structure despite the asymmetric spatial distribution of particles in its coordination shells and the presence of tightly competing structures. Consistent with earlier published results [W. Piñeros et al., J. Chem. Phys. 144, 084502 (2016)], enforcement of greater chemical potential advantages for the target lattice in the interaction optimization led to assemblies with enhanced thermal stability.
Implementation of a Point Algorithm for Real-Time Convex Optimization
NASA Technical Reports Server (NTRS)
Acikmese, Behcet; Motaghedi, Shui; Carson, John
2007-01-01
The primal-dual interior-point algorithm implemented in G-OPT is a relatively new and efficient way of solving convex optimization problems. Given a prescribed level of accuracy, the convergence to the optimal solution is guaranteed in a predetermined, finite number of iterations. G-OPT Version 1.0 is a flight software implementation written in C. Onboard application of the software enables autonomous, real-time guidance and control that explicitly incorporates mission constraints such as control authority (e.g. maximum thrust limits), hazard avoidance, and fuel limitations. This software can be used in planetary landing missions (Mars pinpoint landing and lunar landing), as well as in proximity operations around small celestial bodies (moons, asteroids, and comets). It also can be used in any spacecraft mission for thrust allocation in six-degrees-of-freedom control.
Forward-looking recognition based on convex hull invariants of oil depot region
NASA Astrophysics Data System (ADS)
He, Fangfang; Sun, Jiyin; Han, Bing; Xia, Jing
2007-11-01
Forward-looking navigation system is a fire-new technique for terminal guidance of intending precision-guided weapons and research on oil depot recognition of forward-looking imaging is an essential task for this control and guide system. As conventional matching methods could not overcome perspective transmutation, a new method to identify the forward-looking area of oil depot was advanced in this paper. First, constructed three statistics of regions based on convex hull, which were invariant to affine transform. Then, number of inside oilcans could easily be achieved by adding a decision step. Finally the area of oil depot could be located according to the comparison between the computed number and the foreknowable number under a given threshold. Experiments applied to optical images in different areas show that the proposed method is accurate and has wider application in identifying such small objects as oilcans, and it realizes automatically recognizing area of oil depot from forward-looking imaging.
Yatabe, Kohei; Oikawa, Yasuhiro
2016-06-10
The windowed Fourier filtering (WFF), defined as a thresholding operation in the windowed Fourier transform (WFT) domain, is a successful method for denoising a phase map and analyzing a fringe pattern. However, it has some shortcomings, such as extremely high redundancy, which results in high computational cost, and difficulty in selecting an appropriate window size. In this paper, an extension of WFF for denoising a wrapped-phase map is proposed. It is formulated as a convex optimization problem using Gabor frames instead of WFT. Two Gabor frames with differently sized windows are used simultaneously so that the above-mentioned issues are resolved. In addition, a differential operator is combined with a Gabor frame in order to preserve discontinuity of the underlying phase map better. Some numerical experiments demonstrate that the proposed method is able to reconstruct a wrapped-phase map, even for a severely contaminated situation. PMID:27409020
A Convex Formulation for Magnetic Particle Imaging X-Space Reconstruction
Konkle, Justin J.; Goodwill, Patrick W.; Hensley, Daniel W.; Orendorff, Ryan D.; Lustig, Michael; Conolly, Steven M.
2015-01-01
Magnetic Particle Imaging (mpi) is an emerging imaging modality with exceptional promise for clinical applications in rapid angiography, cell therapy tracking, cancer imaging, and inflammation imaging. Recent publications have demonstrated quantitative mpi across rat sized fields of view with x-space reconstruction methods. Critical to any medical imaging technology is the reliability and accuracy of image reconstruction. Because the average value of the mpi signal is lost during direct-feedthrough signal filtering, mpi reconstruction algorithms must recover this zero-frequency value. Prior x-space mpi recovery techniques were limited to 1d approaches which could introduce artifacts when reconstructing a 3d image. In this paper, we formulate x-space reconstruction as a 3d convex optimization problem and apply robust a priori knowledge of image smoothness and non-negativity to reduce non-physical banding and haze artifacts. We conclude with a discussion of the powerful extensibility of the presented formulation for future applications. PMID:26495839
Posterior convex release and interbody fusion for thoracic scoliosis: technical note.
Mac-Thiong, Jean-Marc; Asghar, Jahangir; Parent, Stefan; Shufflebarger, Harry L; Samdani, Amer; Labelle, Hubert
2016-09-01
Anterior release and fusion is sometimes required in pediatric patients with thoracic scoliosis. Typically, a formal anterior approach is performed through open thoracotomy or video-assisted thoracoscopic surgery. The authors recently developed a technique for anterior release and fusion in thoracic scoliosis referred to as "posterior convex release and interbody fusion" (PCRIF). This technique is performed via the posterior-only approach typically used for posterior instrumentation and fusion and thus avoids a formal anterior approach. In this article the authors describe the technique and its use in 9 patients-to prevent a crankshaft phenomenon in 3 patients and to optimize the correction in 6 patients with a severe thoracic curve showing poor reducibility. After Ponte osteotomies at the levels requiring anterior release and fusion, intervertebral discs are approached from the convex side of the scoliosis. The annulus on the convex side of the scoliosis is incised from the lateral border of the pedicle to the lateral annulus while visualizing and protecting the pleura and spinal cord. The annulus in contact with the pleura and the anterior longitudinal ligament are removed before completing the discectomies and preparing the endplates. The PCRIF was performed at 3 levels in 4 patients and at 4 levels in 5 patients. Mean correction of the main thoracic curve, blood loss, and length of stay were 74.9%, 1290 ml, and 7.6 days, respectively. No neurological deficit, implant failure, or pseudarthrosis was observed at the last follow-up. Two patients had pleural effusion postoperatively, with 1 of them requiring placement of a chest tube. One patient had pulmonary edema secondary to fluid overload, while another patient underwent reoperation for a deep wound infection 3 weeks after the initial surgery. The technique is primarily indicated in skeletally immature patients with open triradiate cartilage and/or severe scoliosis. It can be particularly useful if there is
NASA Astrophysics Data System (ADS)
Demetriou, I. C.
2002-09-01
Methods are presented for least squares data smoothing by using the signs of divided differences of the smoothed values. Professor M.J.D. Powell initiated the subject in the early 1980s and since then, theory, algorithms and FORTRAN software make it applicable to several disciplines in various ways. Let us consider n data measurements of a univariate function which have been altered by random errors. Then it is usual for the divided differences of the measurements to show sign alterations, which are probably due to data errors. We make the least sum of squares change to the measurements, by requiring the sequence of divided differences of order m to have at most q sign changes for some prescribed integer q. The positions of the sign changes are integer variables of the optimization calculation, which implies a combinatorial problem whose solution can require about O(nq) quadratic programming calculations in n variables and n-m constraints. Suitable methods have been developed for the following cases. It has been found that a dynamic programming procedure can calculate the global minimum for the important cases of piecewise monotonicity m=1,q[greater-or-equal, slanted]1 and piecewise convexity/concavity m=2,q[greater-or-equal, slanted]1 of the smoothed values. The complexity of the procedure in the case of m=1 is O(n2+qn log2 n) computer operations, while it is reduced to only O(n) when q=0 (monotonicity) and q=1 (increasing/decreasing monotonicity). The case m=2,q[greater-or-equal, slanted]1 requires O(qn2) computer operations and n2 quadratic programming calculations, which is reduced to one and n-2 quadratic programming calculations when m=2,q=0, i.e. convexity, and m=2,q=1, i.e. convexity/concavity, respectively. Unfortunately, the technique that receives this efficiency cannot generalize for the highly nonlinear case m[greater-or-equal, slanted]3,q[greater-or-equal, slanted]2. However, the case m[greater-or-equal, slanted]3,q=0 is solved by a special strictly
NASA Technical Reports Server (NTRS)
Cullimore, B.
1994-01-01
, capillary devices, user defined fluids, gravity and acceleration body forces on a fluid, and variable volumes. SINDA'85/FLUINT offers the following numerical solution techniques. The Finite difference formulation of the explicit method is the Forward-difference explicit approximation. The formulation of the implicit method is the Crank-Nicolson approximation. The program allows simulation of non-uniform heating and facilitates modeling thin-walled heat exchangers. The ability to model non-equilibrium behavior within two-phase volumes is included. Recent improvements to the program were made in modeling real evaporator-pumps and other capillary-assist evaporators. SINDA'85/FLUINT is available by license for a period of ten (10) years to approved licensees. The licensed program product includes the source code and one copy of the supporting documentation. Additional copies of the documentation may be purchased separately at any time. SINDA'85/FLUINT is written in FORTRAN 77. Version 2.3 has been implemented on Cray series computers running UNICOS, CONVEX computers running CONVEX OS, and DEC RISC computers running ULTRIX. Binaries are included with the Cray version only. The Cray version of SINDA'85/FLUINT also contains SINGE, an additional graphics program developed at Johnson Space Flight Center. Both source and executable code are provided for SINGE. Users wishing to create their own SINGE executable will also need the NASA Device Independent Graphics Library (NASADIG, previously known as SMDDIG; UNIX version, MSC-22001). The Cray and CONVEX versions of SINDA'85/FLUINT are available on 9-track 1600 BPI UNIX tar format magnetic tapes. The CONVEX version is also available on a .25 inch streaming magnetic tape cartridge in UNIX tar format. The DEC RISC ULTRIX version is available on a TK50 magnetic tape cartridge in UNIX tar format. SINDA was developed in 1971, and first had fluid capability added in 1975. SINDA'85/FLUINT version 2.3 was released in 1990.
Detection of Hopf bifurcations in chemical reaction networks using convex coordinates
NASA Astrophysics Data System (ADS)
Errami, Hassan; Eiswirth, Markus; Grigoriev, Dima; Seiler, Werner M.; Sturm, Thomas; Weber, Andreas
2015-06-01
We present efficient algorithmic methods to detect Hopf bifurcation fixed points in chemical reaction networks with symbolic rate constants, thereby yielding information about the oscillatory behavior of the networks. Our methods use the representations of the systems on convex coordinates that arise from stoichiometric network analysis. One of our methods then reduces the problem of determining the existence of Hopf bifurcation fixed points to a first-order formula over the ordered field of the reals that can be solved using computational logic packages. The second method uses ideas from tropical geometry to formulate a more efficient method that is incomplete in theory but worked very well for the examples that we have attempted; we have shown it to be able to handle systems involving more than 20 species.
Reduced Complexity HMM Filtering With Stochastic Dominance Bounds: A Convex Optimization Approach
NASA Astrophysics Data System (ADS)
Krishnamurthy, Vikram; Rojas, Cristian R.
2014-12-01
This paper uses stochastic dominance principles to construct upper and lower sample path bounds for Hidden Markov Model (HMM) filters. Given a HMM, by using convex optimization methods for nuclear norm minimization with copositive constraints, we construct low rank stochastic marices so that the optimal filters using these matrices provably lower and upper bound (with respect to a partially ordered set) the true filtered distribution at each time instant. Since these matrices are low rank (say R), the computational cost of evaluating the filtering bounds is O(XR) instead of O(X2). A Monte-Carlo importance sampling filter is presented that exploits these upper and lower bounds to estimate the optimal posterior. Finally, using the Dobrushin coefficient, explicit bounds are given on the variational norm between the true posterior and the upper and lower bounds.
A novel geometric approach to binary classification based on scaled convex hulls.
Liu, Zhenbing; Liu, J G; Pan, Chao; Wang, Guoyou
2009-07-01
Geometric methods are very intuitive and provide a theoretical foundation to many optimization problems in the fields of pattern recognition and machine learning. In this brief, the notion of scaled convex hull (SCH) is defined and a set of theoretical results are exploited to support it. These results allow the existing nearest point algorithms to be directly applied to solve both the separable and nonseparable classification problems successfully and efficiently. Then, the popular S-K algorithm has been presented to solve the nonseparable problems in the context of the SCH framework. The theoretical analysis and some experiments show that the proposed method may achieve better performance than the state-of-the-art methods in terms of the number of kernel evaluations and the execution time. PMID:19482572
Comment on some results of Erdahl and the convex structure of reduced density matrices
NASA Astrophysics Data System (ADS)
Chen, Jianxin; Ji, Zhengfeng; Ruskai, Mary Beth; Zeng, Bei; Zhou, Duan-Lu
2012-07-01
In [J. Math. Phys. 13, 1608-1621 (1972)], Erdahl, 10.1063/1.1665885 considered the convex structure of the set of N-representable 2-body reduced density matrices in the case of fermions. Some of these results have a straightforward extension to the m-body setting and to the more general quantum marginal problem. We describe these extensions, but cannot resolve a problem in the proof of Erdahl's claim that every extreme point is exposed in finite dimensions. Nevertheless, we can show that when 2m ⩾ N every extreme point of the set of N-representable m-body reduced density matrices has a unique pre-image in both the symmetric and anti-symmetric setting. Moreover, this extends to the quantum marginal setting for a pair of complementary m-body and (N - m)-body reduced density matrices.
On convexity of H-infinity Riccati solutions and its applications
NASA Technical Reports Server (NTRS)
Li, X. P.; Chang, B. C.
1993-01-01
The celebrated two-Riccati-equation solution to a standard H-infinity control problem can be used to characterize all possible stabilizing optimal or suboptimal H-infinity controllers if the optimal H-infinity norm or gamma, an upper bound of a suboptimal H-infinity norm, is given. In this note, some properties of these H-infinity Riccati solutions are revealed. Among them, the most prominent one is that the spectral radius of the product of these two Riccati solutions is a continuous, nonincreasing, convex function of gamma on the domain of interest. Based on these properties, a quadratically convergent algorithm is developed to compute the optimal H-infinity norm.
Wang, Li; Gao, Yaozong; Shi, Feng; Liao, Shu; Li, Gang; Chen, Ken Chung; Shen, Steve G. F.; Yan, Jin; Lee, Philip K. M.; Chow, Ben; Liu, Nancy X.; Xia, James J.; Shen, Dinggang
2014-04-15
Purpose: Cone-beam computed tomography (CBCT) is an increasingly utilized imaging modality for the diagnosis and treatment planning of the patients with craniomaxillofacial (CMF) deformities. Accurate segmentation of CBCT image is an essential step to generate three-dimensional (3D) models for the diagnosis and treatment planning of the patients with CMF deformities. However, due to the poor image quality, including very low signal-to-noise ratio and the widespread image artifacts such as noise, beam hardening, and inhomogeneity, it is challenging to segment the CBCT images. In this paper, the authors present a new automatic segmentation method to address these problems. Methods: To segment CBCT images, the authors propose a new method for fully automated CBCT segmentation by using patch-based sparse representation to (1) segment bony structures from the soft tissues and (2) further separate the mandible from the maxilla. Specifically, a region-specific registration strategy is first proposed to warp all the atlases to the current testing subject and then a sparse-based label propagation strategy is employed to estimate a patient-specific atlas from all aligned atlases. Finally, the patient-specific atlas is integrated into amaximum a posteriori probability-based convex segmentation framework for accurate segmentation. Results: The proposed method has been evaluated on a dataset with 15 CBCT images. The effectiveness of the proposed region-specific registration strategy and patient-specific atlas has been validated by comparing with the traditional registration strategy and population-based atlas. The experimental results show that the proposed method achieves the best segmentation accuracy by comparison with other state-of-the-art segmentation methods. Conclusions: The authors have proposed a new CBCT segmentation method by using patch-based sparse representation and convex optimization, which can achieve considerably accurate segmentation results in CBCT
Wang, Li; Chen, Ken Chung; Gao, Yaozong; Shi, Feng; Liao, Shu; Li, Gang; Shen, Steve G. F.; Yan, Jin; Lee, Philip K. M.; Chow, Ben; Liu, Nancy X.; Xia, James J.; Shen, Dinggang
2014-01-01
Purpose: Cone-beam computed tomography (CBCT) is an increasingly utilized imaging modality for the diagnosis and treatment planning of the patients with craniomaxillofacial (CMF) deformities. Accurate segmentation of CBCT image is an essential step to generate three-dimensional (3D) models for the diagnosis and treatment planning of the patients with CMF deformities. However, due to the poor image quality, including very low signal-to-noise ratio and the widespread image artifacts such as noise, beam hardening, and inhomogeneity, it is challenging to segment the CBCT images. In this paper, the authors present a new automatic segmentation method to address these problems. Methods: To segment CBCT images, the authors propose a new method for fully automated CBCT segmentation by using patch-based sparse representation to (1) segment bony structures from the soft tissues and (2) further separate the mandible from the maxilla. Specifically, a region-specific registration strategy is first proposed to warp all the atlases to the current testing subject and then a sparse-based label propagation strategy is employed to estimate a patient-specific atlas from all aligned atlases. Finally, the patient-specific atlas is integrated into a maximum a posteriori probability-based convex segmentation framework for accurate segmentation. Results: The proposed method has been evaluated on a dataset with 15 CBCT images. The effectiveness of the proposed region-specific registration strategy and patient-specific atlas has been validated by comparing with the traditional registration strategy and population-based atlas. The experimental results show that the proposed method achieves the best segmentation accuracy by comparison with other state-of-the-art segmentation methods. Conclusions: The authors have proposed a new CBCT segmentation method by using patch-based sparse representation and convex optimization, which can achieve considerably accurate segmentation results in CBCT
Nonsmooth Neural Network for Convex Time-Dependent Constraint Satisfaction Problems.
Di Marco, Mauro; Forti, Mauro; Nistri, Paolo; Pancioni, Luca
2016-02-01
This paper introduces a nonsmooth (NS) neural network that is able to operate in a time-dependent (TD) context and is potentially useful for solving some classes of NS-TD problems. The proposed network is named nonsmooth time-dependent network (NTN) and is an extension to a TD setting of a previous NS neural network for programming problems. Suppose C(t), t ≥ 0, is a nonempty TD convex feasibility set defined by TD inequality constraints. The constraints are in general NS (nondifferentiable) functions of the state variables and time. NTN is described by the subdifferential with respect to the state variables of an NS-TD barrier function and a vector field corresponding to the unconstrained dynamics. This paper shows that for suitable values of the penalty parameter, the NTN dynamics displays two main phases. In the first phase, any solution of NTN not starting in C(0) at t=0 is able to reach the moving set C(·) in finite time th , whereas in the second phase, the solution tracks the moving set, i.e., it stays within C(t) for all subsequent times t ≥ t(h). NTN is thus able to find an exact feasible solution in finite time and also to provide an exact feasible solution for subsequent times. This new and peculiar dynamics displayed by NTN is potentially useful for addressing some significant TD signal processing tasks. As an illustration, this paper discusses a number of examples where NTN is applied to the solution of NS-TD convex feasibility problems. PMID:25769174
NASA Technical Reports Server (NTRS)
Furuhama, K.; Moffat, R. J.; Johnston, J. P.; Kays, W. M.
1985-01-01
Turbine-blade cooling is an important issue for high-efficiency turbine engines, and discrete-hole injection is widely used as a cooling method. In the present study, detailed measurements were made of the heat transfer and hydrodynamics of a film-cooled flow on a convex wall, both for full and partial coverage. Two important parameters were altered: the blowing ratio, m, and the number of rows of injection holes. Three values of m were tested: m = 0.2, 0.4, and 0.6. In the blown region, m = 0.4 results in the lowest Stanton numbers of the three blowing ratios tested. This indicates that the value of m = 0.4 is near optimum on the convex wall from the point of view of cooling effect by injection. In the recovery region, Stanton numbers gradually approach the no injection values. Although the heat-transfer behavior during recovery from injection looks relatively complicated, the behavior of Stanton number can be explained in terms of two mechanisms: recovery from the thermal effect of injection and recovery from the turbulence augmentation. This interpretation of the data is supported by the hydrodynamic and temperture-profile measurements. For partial blowing cases, the data follow the full-coverage values inside the blown region. In the unblown region, both in the curved and in the flat plate, the effect of the number of blown rows is clearly seen. Hydrodynamic boundary-layer profiles were measured with the aid of a triple hot-water probe. Three mean-velocity components and six turbulence quantities were simultaneously measured, and inside the blown region strong three-dimensionality was observed.
Face-to-Face Interference in Typical and Atypical Development
ERIC Educational Resources Information Center
Riby, Deborah M.; Doherty-Sneddon, Gwyneth; Whittle, Lisa
2012-01-01
Visual communication cues facilitate interpersonal communication. It is important that we look at faces to retrieve and subsequently process such cues. It is also important that we sometimes look away from faces as they increase cognitive load that may interfere with online processing. Indeed, when typically developing individuals hold face gaze…
Challenges facing production grids
Pordes, Ruth; /Fermilab
2007-06-01
Today's global communities of users expect quality of service from distributed Grid systems equivalent to that their local data centers. This must be coupled to ubiquitous access to the ensemble of processing and storage resources across multiple Grid infrastructures. We are still facing significant challenges in meeting these expectations, especially in the underlying security, a sustainable and successful economic model, and smoothing the boundaries between administrative and technical domains. Using the Open Science Grid as an example, I examine the status and challenges of Grids operating in production today.
NASA Astrophysics Data System (ADS)
Assi, Gustavo R. S.; Srinil, Narakorn; Freire, Cesar M.; Korkischko, Ivan
2014-01-01
Experiments have been conducted to investigate the two-degree-of-freedom vortex-induced vibration (VIV) response of a rigid section of a curved circular cylinder with low mass-damping ratio. Two curved configurations, a concave and a convex, were tested regarding the direction of the flow, in addition to a straight cylinder that served as reference. Amplitude and frequency responses are presented versus reduced velocity for a Reynolds number range between 750 and 15 000. Results for the curved cylinders with concave and convex configurations revealed significantly lower vibration amplitudes when compared to the typical VIV response of a straight cylinder. However, the concave cylinder showed relatively higher amplitudes than the convex cylinder which were sustained beyond the typical synchronisation region. We believe this distinct behaviour between the convex and the concave configurations is related to the wake interference taking place in the lower half of the curvature due to perturbations generated in the horizontal section when it is positioned upstream. Particle-image velocimetry (PIV) measurements of the separated flow along the cylinder highlight the effect of curvature on vortex formation and excitation revealing a complex fluid-structure interaction mechanism.
Face the Fats Quiz II Do you know your fats by heart? Ready to make informed choices about the foods you ... to fried chicken, test your knowledge about the fats in some familiar foods. Welcome to Face the ...
De la Torre, Fernando; Chu, Wen-Sheng; Xiong, Xuehan; Vicente, Francisco; Ding, Xiaoyu; Cohn, Jeffrey
2016-01-01
Within the last 20 years, there has been an increasing interest in the computer vision community in automated facial image analysis algorithms. This has been driven by applications in animation, market research, autonomous-driving, surveillance, and facial editing among others. To date, there exist several commercial packages for specific facial image analysis tasks such as facial expression recognition, facial attribute analysis or face tracking. However, free and easy-to-use software that incorporates all these functionalities is unavailable. This paper presents IntraFace (IF), a publicly-available software package for automated facial feature tracking, head pose estimation, facial attribute recognition, and facial expression analysis from video. In addition, IFincludes a newly develop technique for unsupervised synchrony detection to discover correlated facial behavior between two or more persons, a relatively unexplored problem in facial image analysis. In tests, IF achieved state-of-the-art results for emotion expression and action unit detection in three databases, FERA, CK+ and RU-FACS; measured audience reaction to a talk given by one of the authors; and discovered synchrony for smiling in videos of parent-infant interaction. IF is free of charge for academic use at http://www.humansensing.cs.cmu.edu/intraface/.
Cognitive mechanisms of face processing.
Ellis, A W
1992-01-29
Evidence from natural and induced errors of face recognition, from the effects of different cues on resolving errors, and from the latencies to make different decisions about seen faces, all suggest that familiar face recognition involves a fixed, invariant sequence of stages. To recognize a familiar face, a perceptual description of a seen face must first activate a long-standing representation of the appearance of the face of the familiar person. 'Semantic' knowledge about such things as the person's occupation and personality are accessed next, followed, in the final stage, by the name. Certain factors affect the ease of familiar face recognition. Faces seen in the recent past are recognized more readily (repetition priming), as are distinctive faces, and faces preceded by those of related individuals (associative priming). Our knowledge of these phenomena is reviewed for the light it can shed upon the mechanisms of face recognition. Four aspects of face recognition--graded similarity effects and part-to-whole completion in repetition priming, prototype extraction with simultaneous retention of information about individual exemplars, and distinctiveness effects in classification and identification--are proposed as being compatible with distributed memory accounts of cognitive representations. PMID:1348131
A novel thermal face recognition approach using face pattern words
NASA Astrophysics Data System (ADS)
Zheng, Yufeng
2010-04-01
A reliable thermal face recognition system can enhance the national security applications such as prevention against terrorism, surveillance, monitoring and tracking, especially at nighttime. The system can be applied at airports, customs or high-alert facilities (e.g., nuclear power plant) for 24 hours a day. In this paper, we propose a novel face recognition approach utilizing thermal (long wave infrared) face images that can automatically identify a subject at both daytime and nighttime. With a properly acquired thermal image (as a query image) in monitoring zone, the following processes will be employed: normalization and denoising, face detection, face alignment, face masking, Gabor wavelet transform, face pattern words (FPWs) creation, face identification by similarity measure (Hamming distance). If eyeglasses are present on a subject's face, an eyeglasses mask will be automatically extracted from the querying face image, and then masked with all comparing FPWs (no more transforms). A high identification rate (97.44% with Top-1 match) has been achieved upon our preliminary face dataset (of 39 subjects) from the proposed approach regardless operating time and glasses-wearing condition.e
FaceID: A face detection and recognition system
Shah, M.B.; Rao, N.S.V.; Olman, V.; Uberbacher, E.C.; Mann, R.C.
1996-12-31
A face detection system that automatically locates faces in gray-level images is described. Also described is a system which matches a given face image with faces in a database. Face detection in an Image is performed by template matching using templates derived from a selected set of normalized faces. Instead of using original gray level images, vertical gradient images were calculated and used to make the system more robust against variations in lighting conditions and skin color. Faces of different sizes are detected by processing the image at several scales. Further, a coarse-to-fine strategy is used to speed up the processing, and a combination of whole face and face component templates are used to ensure low false detection rates. The input to the face recognition system is a normalized vertical gradient image of a face, which is compared against a database using a set of pretrained feedforward neural networks with a winner-take-all fuser. The training is performed by using an adaptation of the backpropagation algorithm. This system has been developed and tested using images from the FERET database and a set of images obtained from Rowley, et al and Sung and Poggio.
Own-race and own-age biases facilitate visual awareness of faces under interocular suppression
Stein, Timo; End, Albert; Sterzer, Philipp
2014-01-01
The detection of a face in a visual scene is the first stage in the face processing hierarchy. Although all subsequent, more elaborate face processing depends on the initial detection of a face, surprisingly little is known about the perceptual mechanisms underlying face detection. Recent evidence suggests that relatively hard-wired face detection mechanisms are broadly tuned to all face-like visual patterns as long as they respect the typical spatial configuration of the eyes above the mouth. Here, we qualify this notion by showing that face detection mechanisms are also sensitive to face shape and facial surface reflectance properties. We used continuous flash suppression (CFS) to render faces invisible at the beginning of a trial and measured the time upright and inverted faces needed to break into awareness. Young Caucasian adult observers were presented with faces from their own race or from another race (race experiment) and with faces from their own age group or from another age group (age experiment). Faces matching the observers’ own race and age group were detected more quickly. Moreover, the advantage of upright over inverted faces in overcoming CFS, i.e., the face inversion effect (FIE), was larger for own-race and own-age faces. These results demonstrate that differences in face shape and surface reflectance influence access to awareness and configural face processing at the initial detection stage. Although we did not collect data from observers of another race or age group, these findings are a first indication that face detection mechanisms are shaped by visual experience with faces from one’s own social group. Such experience-based fine-tuning of face detection mechanisms may equip in-group faces with a competitive advantage for access to conscious awareness. PMID:25136308
Own-race and own-age biases facilitate visual awareness of faces under interocular suppression.
Stein, Timo; End, Albert; Sterzer, Philipp
2014-01-01
The detection of a face in a visual scene is the first stage in the face processing hierarchy. Although all subsequent, more elaborate face processing depends on the initial detection of a face, surprisingly little is known about the perceptual mechanisms underlying face detection. Recent evidence suggests that relatively hard-wired face detection mechanisms are broadly tuned to all face-like visual patterns as long as they respect the typical spatial configuration of the eyes above the mouth. Here, we qualify this notion by showing that face detection mechanisms are also sensitive to face shape and facial surface reflectance properties. We used continuous flash suppression (CFS) to render faces invisible at the beginning of a trial and measured the time upright and inverted faces needed to break into awareness. Young Caucasian adult observers were presented with faces from their own race or from another race (race experiment) and with faces from their own age group or from another age group (age experiment). Faces matching the observers' own race and age group were detected more quickly. Moreover, the advantage of upright over inverted faces in overcoming CFS, i.e., the face inversion effect (FIE), was larger for own-race and own-age faces. These results demonstrate that differences in face shape and surface reflectance influence access to awareness and configural face processing at the initial detection stage. Although we did not collect data from observers of another race or age group, these findings are a first indication that face detection mechanisms are shaped by visual experience with faces from one's own social group. Such experience-based fine-tuning of face detection mechanisms may equip in-group faces with a competitive advantage for access to conscious awareness. PMID:25136308
Electrostatic Potential of Specific Mineral Faces
Zarzycki, Piotr P.; Chatman, Shawn ME; Preocanin, Tajana; Rosso, Kevin M.
2011-07-05
Reaction rates of environmental processes occurring at hydrated mineral surfaces are primarily controlled by the electrostatic potential that develops at the interface. This potential depends on the structure of exposed crystal faces, as well as the pH and the type of ions and their interactions with these faces. Despite its importance, experimental methods for determining fundamental electrostatic properties of specific crystal faces such as the point of zero charge are few. Here we show that this information may be obtained from simple, cyclic potentiometric titration using a well characterized single-crystal electrode exposing the face of interest. The method exploits the presence of a hysteresis loop in the titration measurements that allows extraction of key electrostatic descriptors using the Maxwell construction. The approach is demonstrated for hematite (α-Fe_{2}O_{3}) (001), and a thermodynamic proof is provided for the resulting estimate of its point of zero charge. Insight gained from this method will aid in predicting the fate of migrating contaminants, mineral growth/dissolution processes, mineral-microbiological interactions, and in testing surface complexation theories.
Face lift postoperative recovery.
Mottura, A Aldo
2002-01-01
The purpose of this paper is to describe what I have studied and experienced, mainly regarding the control and prediction of the postoperative edema; how to achieve an agreeable recovery and give positive support to the patient, who in turn will receive pleasant sensations that neutralize the negative consequences of the surgery.After the skin is lifted, the drainage flow to the flaps is reversed abruptly toward the medial part of the face, where the flap bases are located. The thickness and extension of the flap determines the magnitude of the post-op edema, which is also augmented by medial surgeries (blepharo, rhino) whose trauma obstruct their natural drainage, increasing the congestion and edema. To study the lymphatic drainage, the day before an extended face lift (FL) a woman was infiltrated in the cheek skin with lynfofast (solution of tecmesio) and the absorption was observed by gamma camera. Seven days after the FL she underwent the same study; we observed no absorption by the lymphatic, concluding that a week after surgery, the lymphatic network was still damaged. To study the venous return during surgery, a fine catheter was introduced into the external jugular vein up to the mandibular border to measure the peripheral pressure. Following platysma plication the pressure rose, and again after a simple bandage, but with an elastic bandage it increased even further, diminishing considerably when it was released. Hence, platysma plication and the elastic bandage on the neck augment the venous congestion of the face. There are diseases that produce and can prolong the surgical edema: cardiac, hepatic, and renal insufficiencies, hypothyroidism, malnutrition, etc. According to these factors, the post-op edema can be predicted, the surgeon can choose between a wide dissection or a medial surgery, depending on the social or employment compromises the patient has, or the patient must accept a prolonged recovery if a complex surgery is necessary. Operative
Reanimating the paralyzed face
2013-01-01
Facial animation is an essential part of human communication and one of the main means of expressing emotions, indexing our physiologic state and providing nonverbal cues. The loss of this important human quality due to facial paralysis can be devastating and is often associated with depression, social isolation and poor quality of life. Interruption of the neuromuscular pathway from the facial motor cortex to the facial muscles is the common causative factor in facial paralysis resulting from various etiologies. Restoring tone, symmetry and movement to the paralyzed face requires timely nerve grafting intervention in cases of reversible paralysis and the transfer of functional muscle units in irreversible paralysis. We review recent advances in these techniques. PMID:24273650
Energy conservation using face detection
NASA Astrophysics Data System (ADS)
Deotale, Nilesh T.; Kalbande, Dhananjay R.; Mishra, Akassh A.
2011-10-01
Computerized Face Detection, is concerned with the difficult task of converting a video signal of a person to written text. It has several applications like face recognition, simultaneous multiple face processing, biometrics, security, video surveillance, human computer interface, image database management, digital cameras use face detection for autofocus, selecting regions of interest in photo slideshows that use a pan-and-scale and The Present Paper deals with energy conservation using face detection. Automating the process to a computer requires the use of various image processing techniques. There are various methods that can be used for Face Detection such as Contour tracking methods, Template matching, Controlled background, Model based, Motion based and color based. Basically, the video of the subject are converted into images are further selected manually for processing. However, several factors like poor illumination, movement of face, viewpoint-dependent Physical appearance, Acquisition geometry, Imaging conditions, Compression artifacts makes Face detection difficult. This paper reports an algorithm for conservation of energy using face detection for various devices. The present paper suggests Energy Conservation can be done by Detecting the Face and reducing the brightness of complete image and then adjusting the brightness of the particular area of an image where the face is located using histogram equalization.
Self-face enhances processing of immediately preceding invisible faces.
Pannese, Alessia; Hirsch, Joy
2011-02-01
The self-face is thought to be an especially salient stimulus. Behavioral evidence suggests that self-face processing advantage is associated with enhanced processing of temporally adjacent subliminal stimuli. However, the neural basis of this self-related processing modulation has not been investigated. We studied self-face induced signal amplification through masked priming and repetition suppression (fMRI adaptation). Subjects performed a gender-categorization task on self- and non-self target faces preceded by subliminal (17 ms) prime faces. The relationship between prime and target was varied between task-incongruent (when prime and target belonged to a different gender) and task-congruent (when prime and target belonged to the same gender) pairs. We found that, in the presence of the visible self-face (but not of other non-self faces), a bilateral fronto-parietal network exhibited repetition suppression to subliminal prime faces belonging to the same gender (task-congruent) as the target, consistent with the notion that, in the presence of the self-face, subliminal stimuli access high-level processing systems. These results are in agreement with the notion of self-specific top-down amplification of subliminal task-relevant information, and suggest that the self-face, through its high salience, is particularly efficacious in focusing attention. PMID:21168427
NASA Astrophysics Data System (ADS)
Fowler, Hayley; Kendon, Elizabeth; Blenkinsop, Stephen; Chan, Steven; Ferro, Christopher; Roberts, Nigel; Stephenson, David; Jones, Richard; Sessford, Pat
2013-04-01
During the last decade, widespread major flood events in the UK and across the rest of Europe have focussed attention on perceived increases in rainfall intensities. Whilst Regional Climate Models (RCMs) are able to simulate the magnitude and spatial pattern of observed daily extreme rainfall events more reliably than Global Circulation Models (GCMs), they still underestimate extreme rainfall in relation to observations. Particularly during the summer a large proportion of the precipitation comes from convective storms that are typically too small to be explicitly represented by climate models. Instead, convection parameterisation schemes are necessary to represent the larger-scale effect of unresolved convective cells. Given the deficiencies in the simulation of extreme rainfall by climate models, even in the current generation of high-resolution RCMs, the CONVEX project (CONVective EXtremes) argues that an integrated approach is needed that brings together observations, basic understanding and models. This should go hand in hand with a change from a focus on traditional validation exercises (comparing modelled and observed extremes) to an understanding and quantification of the causes of model deficiencies in the simulation of extreme rainfall processes on different spatial and temporal scales. It is particularly true for localised intense summer convection. CONVEX therefore aims to contribute to the goals of enabling society to respond to global climate change and predicting the regional and local impacts of environmental change. In addition to an improved understanding of the spatial-temporal characteristics of extreme rainfall processes (principally in the UK) the project is also assessing the influence of model parameterisations and resolution on the simulation of extreme rainfall events and processes. This includes the running of new RCM simulations undertaken by the UK Meteorological Office at 50km and 12km resolutions (parameterised convection) and
NASA Astrophysics Data System (ADS)
Blenkinsop, Stephen; Fowler, Hayley; Kendon, Elizabeth; Chan, Steven; Ferro, Chris; Roberts, Nigel; Sessford, Pat
2014-05-01
During the last decade, widespread major flood events in the UK and across Europe have focussed attention on perceived increases in rainfall intensities. Whilst Regional Climate Models (RCMs) are able to simulate the magnitude and spatial pattern of observed daily extreme rainfall events more reliably than Global Circulation Models (GCMs), they still underestimate extreme rainfall in relation to observations and do not capture the properties of sub-daily events that may lead to flooding in urban areas. In the UK and Europe, particularly during the summer, a large proportion of precipitation comes from convective storms that are typically too small to be explicitly represented by climate models. Instead, convection parameterisation schemes are necessary to represent the larger-scale effect of unresolved convective cells. The CONVEX project (CONVective EXtremes) argues that an integrated approach is needed to provide improvements in estimates of change in extreme rainfall, particularly for summer convective events. As usable predictions require the synthesis of observations, understanding of atmospheric processes and models, a change in focus from traditional validation exercises (comparing modelled and observed extremes) to an understanding and quantification of the causes for model deficiencies in the simulation of extreme rainfall processes on different spatial and temporal scales is needed. By adopting this new focus CONVEX aims to contribute to the goals of enabling society to respond to global climate change and predicting the regional and local impacts of environmental change on timescales from days to decades. In addition to an improved understanding of the spatial-temporal characteristics of extreme rainfall processes (principally in the UK) the project is also assessing the influence of model parameterisations and resolution on the simulation of extreme rainfall events and processes. Under the project the UK Meteorological Office has run new RCM simulations
NASA Technical Reports Server (NTRS)
Slater, David C.; Morgan, Jeffrey S.; Timothy, J. Gethyn
1989-01-01
The presently performance-evaluated format, in which a high-gain curved-channel microchannel plate (M2MCP) has a spherical concave input face and a plane output face, allows the input face of the MCP (1) to match such curved focal surfaces as that of a Rowland-circle spectrometer mounting, while (2) having a high-resolution plane readout array in proximity focus with the output face. This MCP has been evaluated in a discrete-anode multicathode microchannel array detector system. The saturated modal gain was found to be inversely proportional to the length/diameter ratio of the channels and directly proportional to the applied MCP voltage.
Non-convex model of the binary asteroid (809) Lundia and its density estimation
NASA Astrophysics Data System (ADS)
Kryszczynska, A.; Bartczak, P.; Polinska, M.; Colas, F.
2014-07-01
Introduction: (809) Lundia was classified as a V-type asteroid in the Flora family (Florczak et.al. 2002). The binary nature of (809) Lundia was discovered in September 2005 based on photometric observations. The first modeling of the Lundia synchronous binary system was based on 22 lightcurves obtained at Borowiec and Pic du Midi Observatories during two oppositions in 2005/2006 and 2006/2007. Two methods of modeling --- modified Roche ellipsoids and kinematic --- gave similar parameters for the system (Kryszczynska et al. 2009). The poles of the orbit in ecliptic coordinates were: longitude 118° and latitude 28° in the modified Roche model and 120°, 18°, respectively, in the kinematic model. The orbital period obtained from the lightcurve analysis as well as from modeling was 15.418 h. The obtained bulk density of both components was 1.64 or 1.71 g/ccm. Observations: We observed (809) Lundia in the 2008, 2009/2010, 2011, and 2012 oppositions at the Borowiec, Pic du Midi, Prompt, and Rozhen Observatories. As predicted, the visible eclipses/occultation events were observed only in 2011. Currently, our dataset consists of 45 individual lightcurves and they were all used in the new modeling. Method: We used new method of modeling based on a genetic algorithm that is able to create a non-convex asteroid shape model, rotational period, and spin-axis orientation of a single or binary asteroid, using only photometric observations. The details of the method are presented in the poster by Bartczak et al., at this conference. Results: The new non-convex model of (809) Lundia is presented in the figure. The parameters of the system in the ecliptic coordinates are: longitude 122°, latitude 22°, and sidereal period 15.41574 h. They are very similar to the values obtained before. However, assuming an equivalent diameter of a single body of 9.1 km from the Spitzer observations (Marchis et al. 2012) and the volume of the two modeled bodies, the separation of the components
libCreme: An optimization library for evaluating convex-roof entanglement measures
NASA Astrophysics Data System (ADS)
Röthlisberger, Beat; Lehmann, Jörg; Loss, Daniel
2012-01-01
We present the software library libCreme which we have previously used to successfully calculate convex-roof entanglement measures of mixed quantum states appearing in realistic physical systems. Evaluating the amount of entanglement in such states is in general a non-trivial task requiring to solve a highly non-linear complex optimization problem. The algorithms provided here are able to achieve to do this for a large and important class of entanglement measures. The library is mostly written in the MATLAB programming language, but is fully compatible to the free and open-source OCTAVE platform. Some inefficient subroutines are written in C/C++ for better performance. This manuscript discusses the most important theoretical concepts and workings of the algorithms, focusing on the actual implementation and usage within the library. Detailed examples in the end should make it easy for the user to apply libCreme to specific problems. Program summaryProgram title:libCreme Catalogue identifier: AEKD_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEKD_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU GPL version 3 No. of lines in distributed program, including test data, etc.: 4323 No. of bytes in distributed program, including test data, etc.: 70 542 Distribution format: tar.gz Programming language: Matlab/Octave and C/C++ Computer: All systems running Matlab or Octave Operating system: All systems running Matlab or Octave Classification: 4.9, 4.15 Nature of problem: Evaluate convex-roof entanglement measures. This involves solving a non-linear (unitary) optimization problem. Solution method: Two algorithms are provided: A conjugate-gradient method using a differential-geometric approach and a quasi-Newton method together with a mapping to Euclidean space. Running time: Typically seconds to minutes for a density matrix of a few low-dimensional systems and a decent implementation of the
The Face that Launched a Thousand Slips
NASA Technical Reports Server (NTRS)
Moore, J. M.; Howard, A. D.; Schenk, P.; Thomas, P. C.
2013-01-01
formative processes been active in the recent past? 5) Finally, is the surface accreting or eroding? The smooth character of the leading edge hemisphere of Helene and the dominance of mass wasting suggest that the surface is composed of fine-grained debris, probably dominated by dust-size to small gravel particles. The Lagrangian points of saturnian satellites are locations where planetesimals might have accreted to form co-orbital satellites such as and they may capture ejecta from their master moon. Published models suggest that Helene is a site of net accretion, but we find no extant explanation for the dominance of fine grain sizes for the surface (and probable subsurface) composition of Helene and the other Lagrangian satellites. Observation of the mass wasting tracks on Helene suggests the presence of well-defined streams of debris with low bordering levees that may be depositional features or remnants of the dissected higher surface. Some flows in grazing illumination appear to have a convex cross-section. This mass-flow morphology might be consistent with the occurrence of large-scale flow events, but which might have occurred through rapid emplacement or slow glacier-like creep. On the other hand, small craters appear to have been "softened" by creep-like processes, indicating ongoing mass wasting.
Wired for Her Face? Male Attentional Bias for Female Faces
Okazaki, Yuka; Abrahamyan, Arman; Stevens, Catherine J.
2009-01-01
Under conditions of inattention or deficits in orienting attention, special classes of stimuli (e.g. faces, bodies) are more likely to be perceived than other stimuli. This suggests that biologically salient visual stimuli automatically recruit attention, even when they are task-irrelevant or ignored. Here we report results from a behavioral experiment with female and male subjects and two magnetoencephalography (MEG) experiments with male subjects only, in which we investigated attentional capture with face and hand stimuli. In both the behavioral and MEG experiments, subjects were required to count the number of gender-specific targets from either face or hand categories within a block of stimuli. In the behavioral experiment, we found that male subjects were significantly more accurate in response to female than male face target blocks. There was no corresponding effect found in response to hand target blocks. Female subjects did not show a gender-based difference in response to face or hand target blocks. MEG results indicated that the male subjects’ responses to face stimuli in primary visual cortex (V1) and the face-selective part of the fusiform gyrus (FG) were reduced when male face stimuli were not relevant to the task, whereas female faces maintained a strong response in these areas in both task-relevant and task-irrelevant conditions. These results suggest that within the male brain, female face stimuli are more resilient to suppression than male faces, once attention is drawn to the part of the visual field where the face appears. PMID:19809873
Scaling of Convex Hull Volume to Body Mass in Modern Primates, Non-Primate Mammals and Birds
Brassey, Charlotte A.; Sellers, William I.
2014-01-01
The volumetric method of ‘convex hulling’ has recently been put forward as a mass prediction technique for fossil vertebrates. Convex hulling involves the calculation of minimum convex hull volumes (volCH) from the complete mounted skeletons of modern museum specimens, which are subsequently regressed against body mass (Mb) to derive predictive equations for extinct species. The convex hulling technique has recently been applied to estimate body mass in giant sauropods and fossil ratites, however the biomechanical signal contained within volCH has remained unclear. Specifically, when volCH scaling departs from isometry in a group of vertebrates, how might this be interpreted? Here we derive predictive equations for primates, non-primate mammals and birds and compare the scaling behaviour of Mb to volCH between groups. We find predictive equations to be characterised by extremely high correlation coefficients (r2 = 0.97–0.99) and low mean percentage prediction error (11–20%). Results suggest non-primate mammals scale body mass to volCH isometrically (b = 0.92, 95%CI = 0.85–1.00, p = 0.08). Birds scale body mass to volCH with negative allometry (b = 0.81, 95%CI = 0.70–0.91, p = 0.011) and apparent density (volCH/Mb) therefore decreases with mass (r2 = 0.36, p<0.05). In contrast, primates scale body mass to volCH with positive allometry (b = 1.07, 95%CI = 1.01–1.12, p = 0.05) and apparent density therefore increases with size (r2 = 0.46, p = 0.025). We interpret such departures from isometry in the context of the ‘missing mass’ of soft tissues that are excluded from the convex hulling process. We conclude that the convex hulling technique can be justifiably applied to the fossil record when a large proportion of the skeleton is preserved. However we emphasise the need for future studies to quantify interspecific variation in the distribution of soft tissues such as muscle, integument and body fat
Face-n-Food: Gender Differences in Tuning to Faces
Pavlova, Marina A.; Scheffler, Klaus; Sokolov, Alexander N.
2015-01-01
Faces represent valuable signals for social cognition and non-verbal communication. A wealth of research indicates that women tend to excel in recognition of facial expressions. However, it remains unclear whether females are better tuned to faces. We presented healthy adult females and males with a set of newly created food-plate images resembling faces (slightly bordering on the Giuseppe Arcimboldo style). In a spontaneous recognition task, participants were shown a set of images in a predetermined order from the least to most resembling a face. Females not only more readily recognized the images as a face (they reported resembling a face on images, on which males still did not), but gave on overall more face responses. The findings are discussed in the light of gender differences in deficient face perception. As most neuropsychiatric, neurodevelopmental and psychosomatic disorders characterized by social brain abnormalities are sex specific, the task may serve as a valuable tool for uncovering impairments in visual face processing. PMID:26154177
Many-faced cells and many-edged faces in 3D Poisson-Voronoi tessellations
NASA Astrophysics Data System (ADS)
Hilhorst, H. J.; Lazar, E. A.
2014-10-01
Motivated by recent new Monte Carlo data we investigate a heuristic asymptotic theory that applies to n-faced 3D Poisson-Voronoi cells in the limit of large n. We show how this theory may be extended to n-edged cell faces. It predicts the leading order large-n behavior of the average volume and surface area of the n-faced cell, and of the average area and perimeter of the n-edged face. Such a face is shown to be surrounded by a toroidal region of volume n/λ (with λ the seed density) that is void of seeds. Two neighboring cells sharing an n-edged face are found to have their seeds at a typical distance that scales as n-1/6 and whose probability law we determine. We present a new data set of 4 × 109 Monte Carlo generated 3D Poisson-Voronoi cells, larger than any before. Full compatibility is found between the Monte Carlo data and the theory. Deviations from the asymptotic predictions are explained in terms of subleading corrections whose powers in n we estimate from the data.
Design and fabrication of concave-convex lens for head mounted virtual reality 3D glasses
NASA Astrophysics Data System (ADS)
Deng, Zhaoyang; Cheng, Dewen; Hu, Yuan; Huang, Yifan; Wang, Yongtian
2015-08-01
As a kind of light-weighted and convenient tool to achieve stereoscopic vision, virtual reality glasses are gaining more popularity nowadays. For these glasses, molded plastic lenses are often adopted to handle both the imaging property and the cost of massive production. However, the as-built performance of the glass depends on both the optical design and the injection molding process, and maintaining the profile of the lens during injection molding process presents particular challenges. In this paper, optical design is combined with processing simulation analysis to obtain a design result suitable for injection molding. Based on the design and analysis results, different experiments are done using high-quality equipment to optimize the process parameters of injection molding. Finally, a single concave-convex lens is designed with a field-of-view of 90° for the virtual reality 3D glasses. The as-built profile error of the glass lens is controlled within 5μm, which indicates that the designed shape of the lens is fairly realized and the designed optical performance can thus be achieved.
NASA Technical Reports Server (NTRS)
Simon, T. W.; Moffat, R. J.; Johnston, J. P.; Kays, W. M.
1982-01-01
Measurements were made of the heat transfer rate through turbulent and transitional boundary layers on an isothermal, convexly curved wall and downstream flat plate. The effect of convex curvature on the fully turbulent boundary layer was a reduction of the local Stanton numbers 20% to 50% below those predicted for a flat wall under the same circumstances. The recovery of the heat transfer rates on the downstream flat wall was extremely slow. After 60 cm of recovery length, the Stanton number was still typically 15% to 20% below the flat wall predicted value. Various effects important in the modeling of curved flows were studied separately. These are: the effect of initial boundary layer thickness, the effect of freestream velocity, the effect of freestream acceleration, the effect of unheated starting length, and the effect of the maturity of the boundary layer. An existing curvature prediction model was tested against this broad heat transfer data base to determine where it could appropriately be used for heat transfer predictions.
Plasma confinement by magnetic field with convex-concave field lines
NASA Astrophysics Data System (ADS)
Tsventoukh, Mikhail M.; Krashevskaya, Galina V.; Prishvitsyn, Alexander S.
2015-06-01
It has been found that plasma confinement by the magnetic field of alternating-sign curvature with convex-concave field lines results in a strong stabilizing action against convective (flute-interchange) perturbations. For simple combinations of axisymmetric mirrors and cusps the calculations according to the kinetic stability criterion give strongly, centrally peaked stable plasma pressure profiles instead of shallow ones. For the experimental research of this effect, a compact magnetic confinement device has been modified by adding of the external current coil to fulfil the field-line curvature requirements. The critical convectively-stable plasma pressure profiles calculation in this experimental geometry and the probe measurements of the spatial plasma distribution in the new magnetic configuration of alternating-sign curvature have been performed. The experimental results give some support for a conclusion that there is an increase in the ion saturation current at the region near the minimum of the specific volume min ∫dl/B. This region corresponds to the average minimum in the second adiabatic invariant, and the kinetic description predicts the stable pressure profile peaking here due to reduction of charge separation by particle drift in alternating-sign curvature.
Designing convex repulsive pair potentials that favor assembly of kagome and snub square lattices.
Piñeros, William D; Baldea, Michael; Truskett, Thomas M
2016-08-01
Building on a recently introduced inverse strategy, isotropic and convex repulsive pair potentials were designed that favor assembly of particles into kagome and equilateral snub square lattices. The former interactions were obtained by a numerical solution of a variational problem that maximizes the range of density for which the ground state of the potential is the kagome lattice. Similar optimizations targeting the snub square lattice were also carried out, employing a constraint that required a minimum chemical potential advantage of the target over select competing structures. This constraint helped to discover isotropic interactions that meaningfully favored the snub square lattice as the ground state structure despite the asymmetric spatial distribution of particles in its coordination shells and the presence of tightly competing structures. Consistent with earlier published results [W. Piñeros et al., J. Chem. Phys. 144, 084502 (2016)], enforcement of greater chemical potential advantages for the target lattice in the interaction optimization led to assemblies with enhanced thermal stability. PMID:27497576
The Optimal Solution of a Non-Convex State-Dependent LQR Problem and Its Applications
Xu, Xudan; Zhu, J. Jim; Zhang, Ping
2014-01-01
This paper studies a Non-convex State-dependent Linear Quadratic Regulator (NSLQR) problem, in which the control penalty weighting matrix in the performance index is state-dependent. A necessary and sufficient condition for the optimal solution is established with a rigorous proof by Euler-Lagrange Equation. It is found that the optimal solution of the NSLQR problem can be obtained by solving a Pseudo-Differential-Riccati-Equation (PDRE) simultaneously with the closed-loop system equation. A Comparison Theorem for the PDRE is given to facilitate solution methods for the PDRE. A linear time-variant system is employed as an example in simulation to verify the proposed optimal solution. As a non-trivial application, a goal pursuit process in psychology is modeled as a NSLQR problem and two typical goal pursuit behaviors found in human and animals are reproduced using different control weighting . It is found that these two behaviors save control energy and cause less stress over Conventional Control Behavior typified by the LQR control with a constant control weighting , in situations where only the goal discrepancy at the terminal time is of concern, such as in Marathon races and target hitting missions. PMID:24747417
Convex optimization of MRI exposure for mitigation of RF-heating from active medical implants
NASA Astrophysics Data System (ADS)
Córcoles, Juan; Zastrow, Earl; Kuster, Niels
2015-09-01
Local RF-heating of elongated medical implants during magnetic resonance imaging (MRI) may pose a significant health risk to patients. The actual patient risk depends on various parameters including RF magnetic field strength and frequency, MR coil design, patient’s anatomy, posture, and imaging position, implant location, RF coupling efficiency of the implant, and the bio-physiological responses associated with the induced local heating. We present three constrained convex optimization strategies that incorporate the implant’s RF-heating characteristics, for the reduction of local heating of medical implants during MRI. The study emphasizes the complementary performances of the different formulations. The analysis demonstrates that RF-induced heating of elongated metallic medical implants can be carefully controlled and balanced against MRI quality. A reduction of heating of up to 25 dB can be achieved at the cost of reduced uniformity in the magnitude of the B1+ field of less than 5%. The current formulations incorporate a priori knowledge of clinically-specific parameters, which is assumed to be available. Before these techniques can be applied practically in the broader clinical context, further investigations are needed to determine whether reduced access to a priori knowledge regarding, e.g. the patient’s anatomy, implant routing, RF-transmitter, and RF-implant coupling, can be accepted within reasonable levels of uncertainty.
L2CXCV: A Fortran 77 package for least squares convex/concave data smoothing
NASA Astrophysics Data System (ADS)
Demetriou, I. C.
2006-04-01
Fortran 77 software is given for least squares smoothing to data values contaminated by random errors subject to one sign change in the second divided differences of the smoothed values, where the location of the sign change is also unknown of the optimization problem. A highly useful description of the constraints is that they follow from the assumption of initially increasing and subsequently decreasing rates of change, or vice versa, of the process considered. The underlying algorithm partitions the data into two disjoint sets of adjacent data and calculates the required fit by solving a strictly convex quadratic programming problem for each set. The piecewise linear interpolant to the fit is convex on the first set and concave on the other one. The partition into suitable sets is achieved by a finite iterative algorithm, which is made quite efficient because of the interactions of the quadratic programming problems on consecutive data. The algorithm obtains the solution by employing no more quadratic programming calculations over subranges of data than twice the number of the divided differences constraints. The quadratic programming technique makes use of active sets and takes advantage of a B-spline representation of the smoothed values that allows some efficient updating procedures. The entire code required to implement the method is 2920 Fortran lines. The package has been tested on a variety of data sets and it has performed very efficiently, terminating in an overall number of active set changes over subranges of data that is only proportional to the number of data. The results suggest that the package can be used for very large numbers of data values. Some examples with output are provided to help new users and exhibit certain features of the software. Important applications of the smoothing technique may be found in calculating a sigmoid approximation, which is a common topic in various contexts in applications in disciplines like physics, economics