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  • STRUCTURAL MECHANICS  (7)
  • Surface physics, nanoscale physics, low-dimensional systems  (4)
  • 1
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    Scattering theory of chiral Majorana fermion interferometry (2012)
    American Physical Society (APS)
    Details
    Publication Date: 2012-03-29
    Description: Author(s): Jian Li, Geneviève Fleury, and Markus Büttiker Using scattering theory, we investigate interferometers composed of chiral Majorana fermion modes coupled to normal metal leads. We advance an approach in which also the basis states in the normal leads are written in terms of Majorana modes. Thus, each pair of electron-hole states is associated wit... [Phys. Rev. B 85, 125440] Published Wed Mar 28, 2012
    Keywords: Surface physics, nanoscale physics, low-dimensional systems
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
    Published by American Physical Society (APS)
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  • 2
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    Scanning gate microscopy of quantum contacts under parallel magnetic field: Beating patterns between spin-split transmission peaks or channel openings (2015)
    American Physical Society (APS)
    Details
    Publication Date: 2015-03-12
    Description: Author(s): Andrii Kleshchonok, Geneviève Fleury, Jean-Louis Pichard, and Gabriel Lemarié We study the conductance g of an electron interferometer created in a two-dimensional electron gas between a nanostructured contact and the depletion region induced by the charged tip of a scanning gate microscope. Using noninteracting models, we study the beating pattern of interference fringes exh... [Phys. Rev. B 91, 125416] Published Wed Mar 11, 2015
    Keywords: Surface physics, nanoscale physics, low-dimensional systems
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
    Published by American Physical Society (APS)
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  • 3
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    Nanowire-based thermoelectric ratchet in the hopping regime (2016)
    American Physical Society (APS)
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    Publication Date: 2016-04-05
    Description: Author(s): Riccardo Bosisio, Geneviève Fleury, Jean-Louis Pichard, and Cosimo Gorini We study a thermoelectric ratchet consisting of an array of disordered nanowires arranged in parallel on top of an insulating substrate and contacted asymmetrically to two electrodes. Transport is investigated in the Mott hopping regime, when localized electrons can propagate through the nanowires v… [Phys. Rev. B 93, 165404] Published Mon Apr 04, 2016
    Keywords: Surface physics, nanoscale physics, low-dimensional systems
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
    Published by American Physical Society (APS)
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  • 4
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    Graphene $n−p$ junctions in the quantum Hall regime: Numerical study of incoherent scattering effects (2018)
    American Physical Society (APS)
    Details
    Publication Date: 2018-05-31
    Description: Author(s): Qianfan Ma, François D. Parmentier, Preden Roulleau, and Geneviève Fleury We investigate electronic transport through a graphene n-p junction in the quantum Hall effect regime at high perpendicular magnetic field, when the filling factors in the n -doped and p -doped regions are fixed to 2 and − 2 , respectively. We compute numerically the conductance G , the noise Q , and the ... [Phys. Rev. B 97, 205445] Published Wed May 30, 2018
    Keywords: Surface physics, nanoscale physics, low-dimensional systems
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
    Published by American Physical Society (APS)
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  • 5
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    Sensitivity and optimization of composite structures using MSC/NASTRAN (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Design sensitivity analysis for composites will soon be available in MSC/NASTRAN. The design variables for composites can be lamina thicknesses, orientation angles, material properties or a combination of all three. With the increasing use of composites in aerospace and automotive industries, this general capability can be used in its own right for carrying out sensitivity analysis of complicated real-life structures. As part of a research effort, the sensitivity analysis was coupled with a general purpose optimizer. This preliminary version of the optimizer is capable of dealing with minimum weight structural design with a rather general design variable linking capability at the element level or system level. Only sizing type of design variables (i.e., lamina thicknesses) can be handled by the optimizer. Test cases were run and validated by comparison with independent finite element packages. The linking of design sensitivity capability for composites in MSC/NASTRAN with an optimizer would give designers a powerful automated tool to carry out practical opitmization design of real-life complicated composite structures.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Sensitivity Analysis in Engineering; p 147-166
    Format: application/pdf
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  • 6
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    ACCESS 3. Approximation concepts code for efficient structural synthesis: User's guide (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A user's guide is presented for ACCESS-3, a research oriented program which combines dual methods and a collection of approximation concepts to achieve excellent efficiency in structural synthesis. The finite element method is used for structural analysis and dual algorithms of mathematical programming are applied in the design optimization procedure. This program retains all of the ACCESS-2 capabilities and the data preparation formats are fully compatible. Four distinct optimizer options were added: interior point penalty function method (NEWSUMT); second order primal projection method (PRIMAL2); second order Newton-type dual method (DUAL2); and first order gradient projection-type dual method (DUAL1). A pure discrete and mixed continuous-discrete design variable capability, and zero order approximation of the stress constraints are also included.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-159260
    Format: application/pdf
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  • 7
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    Discrete-continuous variable structural synthesis using dual methods (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Approximation concepts and dual methods are extended to solve structural synthesis problems involving a mix of discrete and continuous sizing type of design variables. Pure discrete and pure continuous variable problems can be handled as special cases. The basic mathematical programming statement of the structural synthesis problem is converted into a sequence of explicit approximate primal problems of separable form. These problems are solved by constructing continuous explicit dual functions, which are maximized subject to simple nonnegativity constraints on the dual variables. A newly devised gradient projection type of algorithm called DUAL 1, which includes special features for handling dual function gradient discontinuities that arise from the discrete primal variables, is used to find the solution of each dual problem. Computational implementation is accomplished by incorporating the DUAL 1 algorithm into the ACCESS 3 program as a new optimizer option. The power of the method set forth is demonstrated by presenting numerical results for several example problems, including a pure discrete variable treatment of a metallic swept wing and a mixed discrete-continuous variable solution for a thin delta wing with fiber composite skins.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 18; Dec. 198
    Format: text
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  • 8
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    Dual methods and approximation concepts in structural synthesis (1980)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Approximation concepts and dual method algorithms are combined to create a method for minimum weight design of structural systems. Approximation concepts convert the basic mathematical programming statement of the structural synthesis problem into a sequence of explicit primal problems of separable form. These problems are solved by constructing explicit dual functions, which are maximized subject to nonnegativity constraints on the dual variables. It is shown that the joining together of approximation concepts and dual methods can be viewed as a generalized optimality criteria approach. The dual method is successfully extended to deal with pure discrete and mixed continuous-discrete design variable problems. The power of the method presented is illustrated with numerical results for example problems, including a metallic swept wing and a thin delta wing with fiber composite skins.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-3226
    Format: application/pdf
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  • 9
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    ACCESS computer program for the synthesis of large structural systems (1982)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The structural-synthesis computer code ACCESS-3, originally limited to the optimization of relatively simple problems involving truss, membrane, and shear panel elements, has been restructured to make it applicable to structures with a larger number of degrees-of-freedom, design variables, and constraints. The modifications made allow the use of six degrees-of-freedom per node and permit the out-of-core solution of large matrix equations encountered at the analysis stage. Also, finite elements which permit pure bending as well as combined bending and membrane (axial) behavior have been added to satisfy the need for a more comprehensive set of elements. Like its predecessor, the new version of the program combines the approximation concepts with primal or dual formulations to provide an efficient optimization tool.
    Keywords: STRUCTURAL MECHANICS
    Type: International Symposium on Optimum Structural Design and ONR Naval Structural Mechanics Symposium; Oct 19, 1981 - Oct 22, 1981; Tucson, AZ
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  • 10
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    First and second order convex approximation strategies in structural optimization (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: In this paper, various methods based on convex approximation schemes are discussed that have demonstrated strong potential for efficient solution of structural optimization problems. First, the convex linearization method (Conlin) is briefly described, as well as one of its recent generalizations, the method of moving asymptotes (MMA). Both Conlin and MMA can be interpreted as first-order convex approximation methods that attempt to estimate the curvature of the problem functions on the basis of semiempirical rules. Attention is next directed toward methods that use diagonal second derivatives in order to provide a sound basis for building up high-quality explicit approximations of the behavior constraints. In particular, it is shown how second-order information can be effectively used without demanding a prohibitive computational cost. Various first-order and second-order approaches are compared by applying them to simple problems that have a closed form solution.
    Keywords: STRUCTURAL MECHANICS
    Type: Structural Optimization (ISSN 0934-4373); 1; 3-10
    Format: text
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