31,578 research outputs found
Normalizing Weak Boson Pair Production at the Large Hadron Collider
The production of two weak bosons at the Large Hadron Collider will be one of
the most important sources of SM backgrounds for final states with multiple
leptons. In this paper we consider several quantities that can help normalize
the production of weak boson pairs. Ratios of inclusive cross-sections for
production of two weak bosons and Drell-Yan are investigated and the
corresponding theoretical errors are evaluated. The possibility of predicting
the jet veto survival probability of VV production from Drell-Yan data is also
considered. Overall, the theoretical errors on all quantities remain less than
5-20%. The dependence of these quantities on the center of mass energy of the
proton-proton collision is also studied.Comment: 11 pages; added references, minor text revisions, version to appear
in Phys. Rev.
The coexistence of superconductivity and ferromagnetism in nano-scale metallic grains
A nano-scale metallic grain in which the single-particle dynamics are chaotic
is described by the so-called universal Hamiltonian. This Hamiltonian includes
a superconducting pairing term and a ferromagnetic exchange term that compete
with each other: pairing correlations favor minimal ground-state spin, while
the exchange interaction favors maximal spin polarization. Of particular
interest is the fluctuation-dominated regime where the bulk pairing gap is
comparable to or smaller than the single-particle mean level spacing and the
Bardeen-Cooper-Schrieffer theory of superconductivity breaks down.
Superconductivity and ferromagnetism can coexist in this regime. We identify
signatures of the competition between superconductivity and ferromagnetism in a
number of quantities: ground-state spin, conductance fluctuations when the
grain is weakly coupled to external leads and the thermodynamic properties of
the grain, such as heat capacity and spin susceptibility.Comment: 13 pages, 13 figures, Proceedings of the Conference on the Frontiers
of Quantum and Mesoscopic Thermodynamics (FQMT11
Comparison of Powertrain System Configurations for Electric Passenger Vehicles
Copyright © 2015 SAE International. Electric vehicles (EV) are considered a practical alternative to conventional and hybrid electric passenger vehicles, with higher overall powertrain efficiencies by omitting the internal combustion engine. As a consequence of lower energy density in the battery energy storage as compared to fossil fuels powered vehicles, EVs have limited driving range, leading to a range phobia and limited consumer acceptance. Particularly for larger luxury EVs, electric motors with a single reduction gear typically do not achieve the diverse range of function needs that are present in multi-speed conventional vehicles, most notably acceleration performance and top speed requirements. Subsequently, multi-speed EV powertrains have been suggested for these applications. Through the utilization of multiple gear ratios a more diverse range of functional needs can be realized without increasing the practical size of the electric motor. The major limitation of multi-speed EV powertrains is that the increased transmission complexity introduces additional losses to the vehicle. Through a number of simulations this paper studies the integration of multispeed transmission with EV platforms. Particularly, it investigates the performance improvements of both B and E class vehicle platforms realized through utilization of two and three speed transmissions. Also the potential application of hybrid energy storage systems (i.e. batteries combined with super-capacitors) is studied. Results demonstrate that there can be significant benefits attained for both small and large passenger vehicles through the application of multi-speed transmissions. However, optimization of these ratios must be considered in the analysis
Nodeless superconductivity in IrPtTe with strong spin-orbital coupling
The thermal conductivity of superconductor IrPtTe
( = 0.05) single crystal with strong spin-orbital coupling was measured down
to 50 mK. The residual linear term is negligible in zero magnetic
field. In low magnetic field, shows a slow field dependence. These
results demonstrate that the superconducting gap of IrPtTe is
nodeless, and the pairing symmetry is likely conventional s-wave, despite the
existence of strong spin-orbital coupling and a quantum critical point.Comment: 5 pages, 4 figure
Accelerated linearized alternating direction method of multipliers with Nesterov extrapolation
The alternating direction method of multipliers (ADMMs) has found widespread
use in solving separable convex optimization problems. In this paper, by
employing Nesterov extrapolation technique, we propose two families of
accelerated linearized ADMMsfor addressing two-block linearly constrained
separable convex optimization problems where each block of the objective
function exhibits a `nonsmooth' plus `smooth' composite structure. Our proposed
accelerated linearized ADMMs extend two classical Nesterov acceleration methods
designed for unconstrained composite optimization problems to linearly
constrained problems. These methods are capable of achieving non-ergodic
convergence rates of O(1/k^2) provided that one block of the objective function
exhibits strong convexity and the gradients of smooth terms are Lipschitz
continuous. We show that the proposed methods can reduce to accelerated
linearized augmented Lagrangian methods (ALMs) with non-ergodic O(1/k2 )
convergence rates for solving one-block linearly constrained convex
optimization problems. Furthermore, we explore hybrid versions of the proposed
linearized accelerated ADMMs, which also demonstrate non-ergodic convergence
rates of O(1/k2) under the same assumption. We also investigate inexact
versions of the proposed methods. Under mild assumptions regarding error
sequences, these methods still maintain O(1/k2) non-ergodic convergence rates.
By choosing different extrapolation parameters, we explore the relationship
between the proposed methods and existing accelerated methods
Defrost Efficiency Analysis of PMMA Rear Window
Copyright © 2016 SAE International. As a potential material for lightweight vehicle, polymethyl methacrylate (PMMA) has proven to perform well in optical behavior and weather resistance. However, the application in automotive glazing has seldom been studied. This paper investigates the defrost performance of PMMA rear window using both numerical and experimental methods. The finite element analysis (FEA) results were found to be in good agreement with the experimental data. Based on the validated finite element model, we further optimized the defrost efficiency by changing the arrangement of heating lines. The results demonstrated the frost layer on the vision-related region of PMMA rear window can melt within 30 minutes, which meets the requirement of defrost efficiency
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