58,986 research outputs found
dimensional Dirac equation with non Hermitian interaction
We study dimensional Dirac equation with non Hermitian interactions,
but real energies. In particular, we analyze the pseudoscalar and scalar
interactions in detail, illustrating our observations with some examples. We
also show that the relevant hidden symmetry of the Dirac equation with such an
interaction is pseudo supersymmetry.Comment: 9 page
Integrated atomistic process and device simulation of decananometre MOSFETs
In this paper we present a methodology for the integrated atomistic process and device simulation of decananometre MOSFETs. The atomistic process simulations were carried out using the kinetic Monte Carlo process simulator DADOS, which is now integrated into the Synopsys 3D process and device simulation suite Taurus. The device simulations were performed using the Glasgow 3D statistical atomistic simulator, which incorporates density gradient quantum corrections. The overall methodology is illustrated in the atomistic process and device simulation of a well behaved 35 nm physical gate length MOSFET reported by Toshiba
Influence of finite volume and magnetic field effects on the QCD phase diagram
The Polyakov linear sigma model (PLSM) is used to investigate the respective
influence of a finite volume and a magnetic field on the quark-hadron phase
boundary in the plane of baryon chemical potential () vs. temperature
() of the QCD phase diagram. The calculated results indicate sizable shifts
of the quark-hadron phase boundary to lower values of
for increasing magnetic field strength, and an opposite shift to higher values
of for decreasing system volume. Such shifts could
have important implications for extraction of the thermodynamic properties of
the QCD phase diagram from heavy ion data
Electron transport in an open mesoscopic metallic ring
We study electron transport in a normal-metal ring modeled by the tight
binding lattice Hamiltonian, coupled to two electron reservoirs. First,
Buttiker's model of incorporating inelastic scattering, hence decoherence and
dissipation, has been extended by connecting each site of the open ring to
one-dimensional leads for uniform dephasing in the ring threaded by magnetic
flux. We show with this extension conductance remains symmetric under flux
reversal, and Aharonov-Bohm oscillations with changing magnetic flux reduce to
zero as a function of the decoherence parameter, thus indicating dephasing in
the ring. This extension enables us to find local chemical potential profiles
of the ring sites with changing magnetic flux and the decoherence parameter
analogously to the four probe measurement. The local electrochemical potential
oscillates in the ring sites because of quantum-interference effects. It
predicts that measured four-point resistance also fluctuates and even can be
negative. Then we point out the role of the closed ring's electronic
eigenstates in the persistent current around Fano antiresonances of an
asymmetric open ring for both ideal leads and tunnel barriers. Determining the
real eigenvalues of the non-Hermitian effective Hamiltonian of the ring, we
show that there exist discrete bound states in the continuum of scattering
states for the asymmetric ring even in the absence of magnetic flux. Our
approach involves quantum Langevin equations and non-equilibrium Green's
functions.Comment: 19 pages, 6 figure
Work Fluctuations and Stochastic Resonance
We study Brownian particle motion in a double-well potential driven by an ac
force. This system exhibits the phenomenon of stochastic resonance.
Distribution of work done on the system over a drive period in the time
asymptotic regime have been calculated. We show that fluctuations in the input
energy or work done dominate the mean value. The mean value of work done over a
period as a function of noise strength can also be used to characterise
stochastic resonance in the system. We also discuss the validity of steady
state fluctuation theorems in this particular system.Comment: 5 page
Full-scale thrust reverser testing in an altitude facility
A two-dimensional convergent-divergent exhaust nozzle designed and fabricated by Pratt and Whitney Aircraft was installed on a PW1128 turbofan engine and tested during thrust reverser operation in an altitude facility at NASA Lewis Research Center. A unique collection system was used to capture the thrust reverser exhaust gas and transport it to the primary exhaust collector. Tests were conducted at three flight conditions with varying amounts of thrust reverse at each condition. Some reverser exhaust gas spillage by the collection system was encountered but engine performance was unaffected at all flight conditions tested. Based on the results of this test program, the feasibility of altitude testing of advanced multi-function exhaust nozzle systems has been demonstrated
Is the CPT-norm always positive?
We give an explicit example of an exactly solvable PT-symmetric Hamiltonian
with the unbroken PT symmetry which has one eigenfunction with the zero
PT-norm. The set of its eigenfunctions is not complete in corresponding Hilbert
space and it is non-diagonalizable. In the case of a regular Sturm-Liouville
problem any diagonalizable PT-symmetric Hamiltonian with the unbroken PT
symmetry has a complete set of positive CPT-normalazable eigenfunctions. For
non-diagonalizable
Hamiltonians a complete set of CPT-normalazable functions is possible but the
functions belonging to the root subspace corresponding to multiple zeros of the
characteristic determinant are not eigenfunctions of the Hamiltonian anymore
NEGF simulations of a junctionless Si gate-all-around nanowire transistor with discrete dopants
We have carried out 3D Non-Equilibrium Green Function simulations of ajunctionlessgate-all-around n-type silicon nanowiretransistor of 4.2 Ă 4.2 nm2 cross-section. We model the dopants in a fully atomistic way. The dopant distributions are randomly generated following an average doping concentration of 1020 cmâ3. Elastic and inelastic phonon scattering is considered in our simulation. Considering the dopants in adiscrete way is the first step in the simulation of random dopant variability in junctionlesstransistors in a fully quantum mechanical way. Our results show that, for devices with an âunluckyâ dopants configuration, where there is a starvation of donors under the gate, the threshold voltage can increase by a few hundred mV relative to devices with a more homogeneous distribution of dopants. For the first time we have used a quantum transport model with dissipation to evaluate the change in threshold voltage and subthreshold slope due to the discrete random donors in the channel of ajunctionlessnanowire nMOS transistor. These calculations require a robust convergence scheme between the quantum transport equation and the Poisson equation in order to achieve convergence in the dopant-induced resonance regime
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Conceptualising the impact of information asymmetry on through-life cost: case study of machine tools sector
Information asymmetry (IA) in terms of contextual variety and importance is one of the most challenging aspects of through-life costing in product-service systems (PSS). IA is an imbalance in the information, data and knowledge shared among the parties involved in a contractual agreement. In manufacturing systems under PSS, interaction and effective communication among several parties who are involved in a contractual agreement, rely on the continuity and accuracy of information and context. In such systems, contextual variety exhibits complexity and uncertainty in through-life costing and subsequently in PSS cost assessment. Although the economic aspect of PSS has been studied previously, the impact of IA on through-life cost and for different PSS solutions has not been detailed. Considering manufacturing value chains, this paper introduces a new concept of PSS-hierarchy to perform through-life costing in the presence of IA for various PSS solutions. Moreover, this paper proposes a generic life-cycle model for different PSS solutions to assess the total cost of ownership (TCO). The proposed model has been developed to support decisions on contract design in manufacturing systems. This study considers the manufacturer, service provider and customer perspectives to develop the TCO model using a machine tool manufacturing case study
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