28,936 research outputs found
Methodology for sensitivity analysis, approximate analysis, and design optimization in CFD for multidisciplinary applications
In this study involving advanced fluid flow codes, an incremental iterative formulation (also known as the delta or correction form) together with the well-known spatially-split approximate factorization algorithm, is presented for solving the very large sparse systems of linear equations which are associated with aerodynamic sensitivity analysis. For smaller 2D problems, a direct method can be applied to solve these linear equations in either the standard or the incremental form, in which case the two are equivalent. Iterative methods are needed for larger 2D and future 3D applications, however, because direct methods require much more computer memory than is currently available. Iterative methods for solving these equations in the standard form are generally unsatisfactory due to an ill-conditioning of the coefficient matrix; this problem can be overcome when these equations are cast in the incremental form. These and other benefits are discussed. The methodology is successfully implemented and tested in 2D using an upwind, cell-centered, finite volume formulation applied to the thin-layer Navier-Stokes equations. Results are presented for two sample airfoil problems: (1) subsonic low Reynolds number laminar flow; and (2) transonic high Reynolds number turbulent flow
Complementarity of Semileptonic to and Decays in the Standard Model with Fourth Generation
The decays are
analyzed in the Standard Model extended to fourth generation of quarks (SM4).
The decay rate, forward-backward asymmetry, lepton polarization asymmetries and
the helicity fractions of the final state meson are obtained
using the form factors calculated in the light cone sum rules (LCSR) approach.
We have utilized the constraints on different fourth generation parameters
obtained from the experimental information on , and decays and from
the electroweak precision data to explore their impact on the decay. We find that the values of above mentioned
physical observables deviate deviate significantly from their minimal SM
predications. We also identify a number of correlations between various
observables in and decays. Therefore a combined analysis of these two
decays will compliment each other in the searches of SM4 effects in flavor
physics.Comment: 28 pages, 12 figure
Methodology for sensitivity analysis, approximate analysis, and design optimization in CFD for multidisciplinary applications
Fundamental equations of aerodynamic sensitivity analysis and approximate analysis for the two dimensional thin layer Navier-Stokes equations are reviewed, and special boundary condition considerations necessary to apply these equations to isolated lifting airfoils on 'C' and 'O' meshes are discussed in detail. An efficient strategy which is based on the finite element method and an elastic membrane representation of the computational domain is successfully tested, which circumvents the costly 'brute force' method of obtaining grid sensitivity derivatives, and is also useful in mesh regeneration. The issue of turbulence modeling is addressed in a preliminary study. Aerodynamic shape sensitivity derivatives are efficiently calculated, and their accuracy is validated on two viscous test problems, including: (1) internal flow through a double throat nozzle, and (2) external flow over a NACA 4-digit airfoil. An automated aerodynamic design optimization strategy is outlined which includes the use of a design optimization program, an aerodynamic flow analysis code, an aerodynamic sensitivity and approximate analysis code, and a mesh regeneration and grid sensitivity analysis code. Application of the optimization methodology to the two test problems in each case resulted in a new design having a significantly improved performance in the aerodynamic response of interest
Anyonic interferometry without anyons: How a flux qubit can read out a topological qubit
Proposals to measure non-Abelian anyons in a superconductor by quantum
interference of vortices suffer from the predominantly classical dynamics of
the normal core of an Abrikosov vortex. We show how to avoid this obstruction
using coreless Josephson vortices, for which the quantum dynamics has been
demonstrated experimentally. The interferometer is a flux qubit in a Josephson
junction circuit, which can nondestructively read out a topological qubit
stored in a pair of anyons --- even though the Josephson vortices themselves
are not anyons. The flux qubit does not couple to intra-vortex excitations,
thereby removing the dominant restriction on the operating temperature of
anyonic interferometry in superconductors.Comment: 7 pages, 3 figures; Added an Appendix on parity-protected
single-qubit rotations; problem with Figure 3 correcte
Geodesic scattering by surface deformations of a topological insulator
We consider the classical ballistic dynamics of massless electrons on the
conducting surface of a three-dimensional topological insulator, influenced by
random variations of the surface height. By solving the geodesic equation and
the Boltzmann equation in the limit of shallow deformations, we obtain the
scattering cross section and the conductivity {\sigma}, for arbitrary
anisotropic dispersion relation. At large surface electron densities n this
geodesic scattering mechanism (with {\sigma} propto sqrt{n}) is more effective
at limiting the surface conductivity than electrostatic potential scattering.Comment: 9 pages, 5 figure
Detection of Minimum-Ionizing Particles and Nuclear Counter Effect with Pure BGO and BSO Crystals with Photodiode Read-out
Long BGO (Bismuth Germanate) and BSO (Bismuth Silicate) crystals coupled with
silicon photodiodes have been used to detect minimum-ionizing particles(MIP).
With a low noise amplifier customized for this purpose, the crystals can detect
MIPs with an excellent signal-to-noise ratio. The NCE(Nuclear Counter Effect}
is also clearly observed and measured. Effect of full and partial wrapping of a
reflector around the crystal on light collection is also studied.Comment: 18 pages, including 5 figures; LaTeX and EP
Suppressing decoherence and improving entanglement by quantum-jump-based feedback control in two-level systems
We study the quantum-jump-based feedback control on the entanglement shared
between two qubits with one of them subject to decoherence, while the other
qubit is under the control. This situation is very relevant to a quantum system
consisting of nuclear and electron spins in solid states. The possibility to
prolong the coherence time of the dissipative qubit is also explored. Numerical
simulations show that the quantum-jump-based feedback control can improve the
entanglement between the qubits and prolong the coherence time for the qubit
subject directly to decoherence
A characterization of positive linear maps and criteria of entanglement for quantum states
Let and be (finite or infinite dimensional) complex Hilbert spaces. A
characterization of positive completely bounded normal linear maps from
into is given, which particularly gives a
characterization of positive elementary operators including all positive linear
maps between matrix algebras. This characterization is then applied give a
representation of quantum channels (operations) between infinite-dimensional
systems. A necessary and sufficient criterion of separability is give which
shows that a state on is separable if and only if
for all positive finite rank elementary operators
. Examples of NCP and indecomposable positive linear maps are given and
are used to recognize some entangled states that cannot be recognized by the
PPT criterion and the realignment criterion.Comment: 20 page
Necessary and sufficient conditions for local creation of quantum discord
We show that a local channel cannot create quantum discord (QD) for zero QD
states of size if and only if either it is a completely decohering
channel or it is a nontrivial isotropic channel. For the qubit case this
propertiy is additionally characteristic to the completely decohering channel
or the commutativity-preserving unital channel. In particular, the exact forms
of the completely decohering channel and the commutativity-preserving unital
qubit channel are proposed. Consequently, our results confirm and improve the
conjecture proposed by X. Hu et al. for the case of and improve the
result proposed by A. Streltsov et al. for the qubit case. Furthermore, it is
shown that a local channel nullifies QD in any state if and only if it is a
completely decohering channel. Based on our results, some protocols of quantum
information processing issues associated with QD, especially for the qubit
case, would be experimentally accessible.Comment: 8 page
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