Christian Frankerl  Felix Nippert  Marc Patrick Hoffmann  Christian Brandl  Hans-Jürgen Lugauer  Roland Zeisel  Axel Hoffmann  Matthew John Davies 《physica status solidi b》2020,257(12):2000242

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Nora Schmitt  Steffen Weimann  Christian V. Morfonios  Malte Rntgen  Matthias Heinrich  Peter Schmelcher  Alexander Szameit 《Laser u0026amp; Photonics Reviews》2020,14(4)

The concept of local symmetry has been shown to be a powerful tool in predicting and designing complex transport phenomena in stationary scattering off aperiodic media, in terms of symmetry‐adapted nonlocal currents. For time‐evolving wavepackets, the spatiotemporal correlations caused by local symmetries are more challenging to reveal. A recent formalism‐based nonlocal continuity equation shows how local symmetries are encoded into the dynamics of light propagation in discrete waveguide arrays governed by a Schrödinger equation. However, the experimental demonstration is elusive so far. Representative examples of locally symmetric, globally symmetric, and fully nonsymmetric configurations are fabricated in fs laser‐written photonic arrays and their dynamics are probed. The approach allows to distinguish all three types of structures.  相似文献   

    

Tobias A. Mller  Christian H. Weiß 《商业与工业应用随机模型》2020,36(4):641-659

This article proposes the generalized discrete autoregressive moving‐average (GDARMA) model as a parsimonious and universally applicable approach for stationary univariate or multivariate time series. The GDARMA model can be applied to any type of quantitative time series. It allows to compute moment properties in a unique way, and it exhibits the autocorrelation structure of the traditional ARMA model. This great flexibility is obtained by using data‐specific variation operators, which is illustrated for the most common types of time series data, such as counts, integers, reals, and compositional data. The practical potential of the GDARMA approach is demonstrated by considering a time series of integers regarding votes for a change of the interest rate, and a time series of compositional data regarding television market shares.  相似文献   

    

Christian Constanda  Dale Doty 《复变函数与椭圆型方程》2020,65(1):40-56

ABSTRACT

Numerical approximations of the solution of a boundary value problem when an exact solution is not available can be constructed by means of a variety of methods. In this paper, we present a technique that is based on the integral representation of the solution of an elliptic problem and the properties of the associated layer potentials. The procedure is illustrated in application to the mathematical model of bending of plates with transverse shear deformation in a finite domain, in the presence of Dirichlet, Neumann, and Robin conditions prescribed on the boundary.  相似文献   

    

Christian Laurence  Sergui Mansour  Daniela Vuluga  Julien Legros 《Journal of Physical Organic Chemistry》2020,33(9):e4067

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Christian Kuppe  Kristina R. Rusimova  Lukas Ohnoutek  Dimitar Slavov  Ventsislav K. Valev 《Advanced Optical Materials》2020,8(1)

Recent advances in nonlinear optics, hot electrons for renewable energy (e.g., solar cells and water‐splitting), acousto‐optics, nanometalworking, nanorobotics, steam generation, and photothermal cancer therapy are reviewed here. In all these areas, one of the key enabling properties is the ability of metallic nanoparticles to harvest and control light at the subwavelength scale by supporting coherent electronic oscillations, called localized surface plasmon resonances (LSPRs). Various physical properties and potential areas of application emerge depending on the decay mechanism of the LSPR and, especially, depending on the considered timescale. The field of plasmonics has mainly been associated with manipulating electromagnetic near‐fields at the nanoscale, where absorption is an obstacle. However, plasmonic absorption leads to a stream of temperature‐related phenomena that have only recently attracted significant attention. The goal of this review is to highlight exciting new areas of research (such as nanorobotics, nanometalworking, or acousto‐optical techniques) and to survey the most recent progress in more established areas (such as hot electrons, photothermal therapy, and plasmonic steam generation). To set each research area in context, the text is organized around the thermal cycle of the nanoparticles.  相似文献   

    

Christian Lauer  Wolfgang Paul 《Macromolecular theory and simulations》2023,32(5):2200075

This study presents a numerical investigation of the dimerization of polyglutamine homo-peptides of varying length. It employs the PRIME20 intermediate resolution protein model and studies it with a flat-histogram type Monte Carlo simulation that gives access to the thermodynamic equilibrium of this model over the complete control parameter range (for the simulations this is temperature). For densities comparable to typical in vitro experimental conditions, this study finds that the aggregation and folding of the polyglutamine chains occur concurrently. However, as a function of chain length the sequence of establishment of intra- and intermolecular hydrogen bonding contacts changes. Chains longer than about N = 24 polyglutamine repeat units fold first and then aggregate. This agrees well with the experimental finding that, beyond N = 24 the single polyglutamine chain is the critical nucleus for the aggregation of amyloid fibrils. A finite size scaling of the ordering temperatures reveals that for this chain length (and longer chains) folding occurs at physiological (respectively larger) temperatures, whereas shorter chains are disordered at physiological conditions.  相似文献   

    

Daniel Hilger  Jana Sasse  Christian Hopmann  Marek Behr  Norbert Hosters 《PAMM》2023,23(1):e202200069

We present the data-driven standardized non-intrusive reduced-order modeling strategy, sniROM, applied in context of plastics profile extrusion. After a brief introduction to the process and the governing physics, we give a short overview of the methodology. The ROM is then used to predict temperature distribution within a plastics profile inside the calibration/cooling unit of the extrusion process. The simulation based model predictions are compared with sensor data captured by an infrared camera. Finally, we give an outlook on how both ROM and measurement data can be used to enable a digital shadow of industrial processes.  相似文献   

    

Marvin C. Feike  Christian Mundt 《PAMM》2023,23(1):e202200048

The hyperbolic wave equation of heat conduction with respect to Christov's formulation is utilized with the Streamline- Upwind-Petrov-Galerkin method in space and the Θ, Houbolt, linear acceleration, Wilson-Θ and Newmark methods in time. The derivation of this equation and its matrix formulation are shown. A 2D transient finite element simulation of a generic asperity with an infinite line heat source in an interface, either as a heat flux density q̇ or temperature distribution T, is performed for Math = [0.5; 1.0]. A sensitivity study is presented for the mentioned numerical schemes. The temperature jump in the solution is interpreted as an indicator for a thermal shock.  相似文献   

    

Philip Schreiber  Christian Mittelstedt 《PAMM》2023,22(1):e202200113

The local stability of thin-walled fibre-reinforced plastic composite beams can be reduced to individual laminates using discrete plate theory. These individual plates receive a supporting effect from their surrounding structure, which is modelled with rotational restraints. In the present investigation, this buckling problem is described by a closed-form solution. The energy-based method works with the Rayleigh quotient and the principle of the stationary value of the elastic potential energy. For the analysis of unsymmetrically laminated plates, the classical laminated plate theory (CLPT) considers both the plate deflection and the in-plane displacements. The first-order shear deformation theory (FSDT) and third-order shear deformation theory (TSDT) additionally describe the cross-sectional rotations and thus take transverse shear deformations into account. In addition to the direct consideration of the bending-extension couplings, these have also been investigated using the reduced bending stiffness (RBS) method. The investigation shows the influence of bending-extension coupling on the stability of compressively loaded unsymmetrically laminated plates. Moreover, it is found that the transverse shear stiffness reduces the critical load at relatively high plate thicknesses. The closed-form analytical solution and the RBS method show good agreement with finite element analyses. The presented closed-form analytical methods provide explicit solutions for the critical compressive load of unsymmetric laminates under different boundary conditions. Due to the explicit solution, this method is significantly more computationally efficient than numerical, semi-analytical or exact methods. The present methods are characterised by a simple applicability as well as a very high computational efficiency and are very suitable for preliminary design as well as optimisation of laminated structures.  相似文献