2,715 research outputs found
Quiet engine program flight engine design study
The results are presented of a preliminary flight engine design study based on the Quiet Engine Program high-bypass, low-noise turbofan engines. Engine configurations, weight, noise characteristics, and performance over a range of flight conditions typical of a subsonic transport aircraft were considered. High and low tip speed engines in various acoustically treated nacelle configurations were included
The Bravyi-Kitaev transformation for quantum computation of electronic structure
Quantum simulation is an important application of future quantum computers
with applications in quantum chemistry, condensed matter, and beyond. Quantum
simulation of fermionic systems presents a specific challenge. The
Jordan-Wigner transformation allows for representation of a fermionic operator
by O(n) qubit operations. Here we develop an alternative method of simulating
fermions with qubits, first proposed by Bravyi and Kitaev [S. B. Bravyi, A.Yu.
Kitaev, Annals of Physics 298, 210-226 (2002)], that reduces the simulation
cost to O(log n) qubit operations for one fermionic operation. We apply this
new Bravyi-Kitaev transformation to the task of simulating quantum chemical
Hamiltonians, and give a detailed example for the simplest possible case of
molecular hydrogen in a minimal basis. We show that the quantum circuit for
simulating a single Trotter time-step of the Bravyi-Kitaev derived Hamiltonian
for H2 requires fewer gate applications than the equivalent circuit derived
from the Jordan-Wigner transformation. Since the scaling of the Bravyi-Kitaev
method is asymptotically better than the Jordan-Wigner method, this result for
molecular hydrogen in a minimal basis demonstrates the superior efficiency of
the Bravyi-Kitaev method for all quantum computations of electronic structure
Joint industry planning platforms for coal export supply chains
Improving the performance and reducing the costs associated with export logistics chains is critical to the competitiveness of export coal mines. The fundamental practices associated with the use of export logistics chains made up of mine, trucking, rail and port operations are being challenged by the advent of third party operators on rail systems and the use of the Internet. Whilst individual mines can improve their processes to drive down their mining costs, they face major challenges in their endeavour to improve the performance of export logistics chains and reduce the significant logistics costs of moving coal from the mine to export ships, via the shared infrastructure of rail systems and ports. There is an increasing realisation that global competition is not only between mines but between coal export regions that are defined by their rail system and ports infrastructure. The development and use of a joint industry planning platform for the export logistics chains of the Western Australian Grain Industry has demonstrated that an industry facing significant restructuring and increased competitiveness can achieve major throughput and cost reduction gains when stakeholders in export logistics chains share key planning information using the Internet and state of the art planning tools. Joint industry planning platforms for export logistics chains are being considered or are at initial stages of development for a number of Australasian coal export logistics chains. This paper reviews the development of a joint industry platform for the W A Grain industry and reports on the state of development of similar planning platforms for the export logistics chains of the Illawarra, Hunter Valley, SE Queensland, Blackwater / Moura. Goonyella and Mt Isa / Townsville export coal regions. This paper addresses the key components of joint industry planning platforms, the key information that should be shared, the use of the internet and information servers, and the contractual Structures required to enable stakeholders of an export logistics chain,w ho are competitors or potential competitors, to work together to improve the competitiveness of a coal export region
Pole structure of the Hamiltonian -function for a singular potential
We study the pole structure of the -function associated to the
Hamiltonian of a quantum mechanical particle living in the half-line
, subject to the singular potential . We show that
admits nontrivial self-adjoint extensions (SAE) in a given range of values
of the parameter . The -functions of these operators present poles
which depend on and, in general, do not coincide with half an integer (they
can even be irrational). The corresponding residues depend on the SAE
considered.Comment: 12 pages, 1 figure, RevTeX. References added. Version to appear in
Jour. Phys. A: Math. Ge
Vanishing Viscosity Limits and Boundary Layers for Circularly Symmetric 2D Flows
We continue the work of Lopes Filho, Mazzucato and Nussenzveig Lopes [LMN],
on the vanishing viscosity limit of circularly symmetric viscous flow in a disk
with rotating boundary, shown there to converge to the inviscid limit in
-norm as long as the prescribed angular velocity of the
boundary has bounded total variation. Here we establish convergence in stronger
and -Sobolev spaces, allow for more singular angular velocities
, and address the issue of analyzing the behavior of the boundary
layer. This includes an analysis of concentration of vorticity in the vanishing
viscosity limit. We also consider such flows on an annulus, whose two boundary
components rotate independently.
[LMN] Lopes Filho, M. C., Mazzucato, A. L. and Nussenzveig Lopes, H. J.,
Vanishing viscosity limit for incompressible flow inside a rotating circle,
preprint 2006
Some Observations of Wake Behavior in Laminar and Turbulence Free Stream Flow
Visual observations of the sphere wake have been obtained using the flash photolysis technique. Free stream turbulence of 7 and 10% was found to progressively reduce the size of the wake but no turbulence was found in the attached shear layer nor was the position of the separation point affected. A separation bubble was identified as predicted by Son and Hanratty (1969). Evidence is presented to show that drag reduction in turbulent free streams is not due to turbulence in the attached boundary layer but to enhanced momentum transfer in the wake
Maternal experiences of caring for an infant with neurological impairment after neonatal encephalopathy in Uganda: a qualitative study
Purpose: The study investigated maternal experiences of caring for a child affected by neurological impairment after neonatal encephalopathy (NE) (“birth asphyxia”) in Uganda. Methods: Between September 2011 and October 2012 small group and one-on-one in-depths interviews were conducted with mothers recruited to the ABAaNA study examining outcomes from NE in Mulago hospital, Kampala. Data were analysed thematically with the aid of Nvivo 8 software. Findings: Mothers reported caring for an infant with impairment was often complicated by substantial social, emotional and financial difficulties and stigma. High levels of emotional distress, feelings of social isolation and fearfulness about the future were described. Maternal health-seeking ability was exacerbated by high transport costs, lack of paternal support and poor availability of rehabilitation and counselling services. Meeting and sharing experiences with similarly affected mothers was associated with more positive maternal caring experiences. Conclusion: Mothering a child with neurological impairment after NE is emotionally, physically and financially challenging but this may be partly mitigated by good social support and opportunities to share caring experiences with similarly affected mothers. A facilitated, participatory, community-based approach to rehabilitation training may have important impacts on maximising participation and improving the quality of life of affected mothers and infants.
Implications for Rehabilitation
Caring for an infant with neurological impairment after NE in Uganda has substantial emotional, social and financial impacts on families and is associated with high levels of emotional stress, feelings of isolation and stigma amongst mothers.
Improved social support and the opportunity to share experiences with other similarly affected mothers are associated with a more positive maternal caring experience. High transport costs, lack of paternal support and poor availability of counselling and support services were barriers to maternal healthcare seeking.
Studies examining the feasibility, acceptability and impact of early intervention programmes are warranted to maximise participation and improve the quality of life for affected mothers and their infants
The trace of the heat kernel on a compact hyperbolic 3-orbifold
The heat coefficients related to the Laplace-Beltrami operator defined on the
hyperbolic compact manifold H^3/\Ga are evaluated in the case in which the
discrete group \Ga contains elliptic and hyperbolic elements. It is shown
that while hyperbolic elements give only exponentially vanishing corrections to
the trace of the heat kernel, elliptic elements modify all coefficients of the
asymptotic expansion, but the Weyl term, which remains unchanged. Some physical
consequences are briefly discussed in the examples.Comment: 11 page
Strong ellipticity and spectral properties of chiral bag boundary conditions
We prove strong ellipticity of chiral bag boundary conditions on even
dimensional manifolds. From a knowledge of the heat kernel in an infinite
cylinder, some basic properties of the zeta function are analyzed on
cylindrical product manifolds of arbitrary even dimension.Comment: 16 pages, LaTeX, References adde
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