From the zero-field metal-insulator transition in two dimensions to the quantum Hall transition: a percolation-effective-medium theory

Effective-medium theory is applied to the percolation description of the metal-insulator transition in two dimensions with emphasis on the continuous connection between the zero-magnetic-field transition and the quantum Hall transition. In this model the system consists of puddles connected via saddle points, and there is loss of quantum coherence inside the puddles. The effective conductance of the network is calculated using appropriate integration over the distribution of conductances, leading to a determination of the magnetic field dependence of the critical density. Excellent quantitative agreement is obtained with the experimental data, which allows an estimate of the puddle physical parameters

Emission-aware Energy Storage Scheduling for a Greener Grid

Reducing our reliance on carbon-intensive energy sources is vital for reducing the carbon footprint of the electric grid. Although the grid is seeing increasing deployments of clean, renewable sources of energy, a significant portion of the grid demand is still met using traditional carbon-intensive energy sources. In this paper, we study the problem of using energy storage deployed in the grid to reduce the grid's carbon emissions. While energy storage has previously been used for grid optimizations such as peak shaving and smoothing intermittent sources, our insight is to use distributed storage to enable utilities to reduce their reliance on their less efficient and most carbon-intensive power plants and thereby reduce their overall emission footprint. We formulate the problem of emission-aware scheduling of distributed energy storage as an optimization problem, and use a robust optimization approach that is well-suited for handling the uncertainty in load predictions, especially in the presence of intermittent renewables such as solar and wind. We evaluate our approach using a state of the art neural network load forecasting technique and real load traces from a distribution grid with 1,341 homes. Our results show a reduction of >0.5 million kg in annual carbon emissions -- equivalent to a drop of 23.3% in our electric grid emissions.Comment: 11 pages, 7 figure, This paper will appear in the Proceedings of the ACM International Conference on Future Energy Systems (e-Energy 20) June 2020, Australi

Fermi resonance-algebraic model for molecular vibrational spectra

A Fermi resonance-algebraic model is proposed for molecular vibrations, where a U(2) algebra is used for describing the vibrations of each bond, and Fermi resonances between stretching and bending modes are taken into account. The model for a bent molecule XY_2 and a molecule XY_3 is successfully applied to fit the recently observed vibrational spectrum of the water molecule and arsine (AsH_3), respectively, and results are compared with those of other models. Calculations show that algebraic approaches can be used as an effective method for describing molecular vibrations with small standard deviations

Conceptual and Numerical Analysis of Active Wingtip Vortex Cancellation in Propeller-Driven Electric Aircraft

As battery and electric motor technology continues to advance rapidly, propeller-driven electric aircraft are likely to become a significant part of the aviation market in the near future. One proposed design configuration for electric aircraft involves using large, wingtip- mounted propellers to actively cancel wingtip vortices, a method called active wingtip vortex cancellation (AWVC). By reclaiming part of the kinetic energy that would otherwise be lost to tip vortex formation, drag is decreased. In addition, the induced spanwise flow and upwash from the propeller causes the spanwise lift distribution to remain more uniform at the wingtips, increasing lift. Previous wind tunnel testing of this configuration characterized a significant increase in lift and decrease in drag, particularly in low-aspect-ratio configurations. This paper builds on that research by examining several test cases with a 3D, transient, viscous, sliding mesh CFD analysis in an effort to validate numerical methods for future conceptual design studies. In addition, many practical considerations regarding the implementation of this design are analyzed. Geometry from the aforementioned wind tunnel literature was reconstructed and analyzed. CFD indicated an 18.1% increase in lift and 5.1% increase in net thrust was possible solely through the phenomenon of AWVC. Furthermore, this CFD analysis matched wind tunnel data to within approximately 1%, validating the CFD approach for the analysis of more exotic configurations involving active wingtip vortex cancellation

Photon emission by an ultra-relativistic particle channeling in a periodically bent crystal

This paper is devoted to a detailed analysis of the new type of the undulator radiation generated by an ultra-relativistic charged particle channeling along a crystal plane, which is periodically bent by a transverse acoustic wave, as well as to the conditions limiting the observation of this phenomenon. This mechanism makes feasible the generation of electromagnetic radiation, both spontaneous and stimulated, emitted in a wide range of the photon energies, from X- up to gamma-rays

Melatonin and pro-hypnotic effectiveness of the antidepressant Trazodone: A preliminary evaluation in insomniac mood-disorder patients

Objective To preliminary investigate the link between the darkness hormone melatonin (MLT) and the pro-hypnotic effectiveness of the atypical antidepressant Trazodone (TRZ) in a group of mood disorder patients suffering of insomnia. Design and methods The study's design comprised: i) the enrolment of insomniac outpatients, ii) baseline (t0) psychiatric and biochemical examinations; iii) the subsequent patients' introduction into a treatment with TRZ for 3–4 weeks, followed by post-therapy re-evaluations (t1). The MLT function was investigated by t0/t1 ELISA determinations of 6-hydroxy-MLT sulfate (6-OH-MLTs) levels in early-morning urines and HPLC analysis of morning MLT serum amount. Concomitantly, TRZ and its metabolite m-chloro-phenylpiperazine (m-CPP) were measured by HPLC in serum to monitor patients' compliance/metabolism. Results Seventeen insomniac outpatients, displaying mild symptoms of depression/anxiety resistant to antidepressants, completed TRZ therapy (dose:10–20 mg/day, bedtime). Serum TRZ levels (127 ± 57 ng ml− 1, mean ± SD) confirmed patients' compliance, while the anxiogenic metabolite m-CPP resulting almost undetectable. Moreover, the 6-OH-MLTs output was found increased at t1 vs. baseline values (t1: 58.4 ± 45.02 ng ml− 1; t0: 28.6 ± 15.8 ng ml− 1; mean ± SD, P < 0.05) in 9 patients who recovered both insomnia and depression/anxiety (P < 0.01). Unresponsive subjects showed instead no post-therapy 6-OH-MLTs variation (t1: 48.53 ± 50.70 ng ml− 1; t0: 49.80 ± 66.53 ng ml− 1). Morning MLT in serum slightly diminished at t1 without reaching the statistical significance, not allowing therefore to define the patients' outcome. Conclusions This initial investigation encourages to explore MLT networks as possible correlates of TRZ pro-hypnotic responses

Verification and Validation of a Three-Dimensional Composite Impact Model with Tabulated Input

A material model which incorporates several key capabilities which have been identified by the aerospace community as lacking in the composite impact models currently available in the commercial transient dynamic finite element code LS-DYNA has been developed. The material model utilizes experimentally based tabulated input to define the evolution of plasticity and damage as opposed to specifying discrete input parameters (such as modulus and strength. The plasticity portion of the orthotropic, three-dimensional, macroscopic composite constitutive model is based on an extension of the Tsai-Wu composite failure model into a generalized yield function with a non-associative flow rule. The capability to account for the rate and temperature dependent deformation response of composites has also been incorporated into the material model. For the damage model, a strain equivalent formulation is utilized to allow for the uncoupling of the deformation and damage analyses. In the damage model, a diagonal damage tensor is defined to account for the directionally dependent variation of damage. However, the terms in the damage matrix are semi-coupled such that the damage in a particular coordinate direction is a function of the stresses and plastic strains in all of the coordinate directions. For the failure model, a tabulated approach is utilized in which a stress or strain based invariant is defined as a function of the location of the current stress state in stress space to define the initiation of failure, which allows an arbitrarily shaped failure surface to be defined. A systematic series of validation and verification studies, at a variety of length scales ranging from single element simulations to simulations of a flat panel impact test, have been performed to fully exercise and evaluate the capabilities of the developed model

Heavy Flavour Physics at HERA - a Survey

At the HERA collider at DESY, high energy electron and positron beams interact with proton beams. A review is presented of the variety of ways in which these collisions produce final states containing charm and beauty quarks.Comment: 45 pages including 30 figures. Submitted to International Journal of Modern Physics