12,203 research outputs found
Design optimization of transonic airfoils
Numerical optimization procedures were considered for the design of airfoils in transonic flow based on the transonic small disturbance (TSD) and Euler equations. A sequential approximation optimization technique was implemented with an accurate approximation of the wave drag based on the Nixon's coordinate straining approach. A modification of the Euler surface boundary conditions was implemented in order to efficiently compute design sensitivities without remeshing the grid. Two effective design procedures producing converged designs in approximately 10 global iterations were developed: interchanging the role of the objective function and constraint and the direct lift maximization with move limits which were fixed absolute values of the design variables
Quark-Lepton Symmetry In Five Dimensions
We construct a complete five dimensional Quark-Lepton symmetric model, with
all fields propagating in the bulk. The extra dimension forms an orbifold with the zero mode fermions corresponding to standard model
quarks localised at one fixed point. Zero modes corresponding to
left(right)-chiral leptons are localised at (near) the other fixed point. This
localisation pattern is motivated by the symmetries of the model. Shifting the
right-handed neutrinos and charged leptons slightly from the fixed point
provides a new mechanism for understanding the absence of relations of the type
or in Quark-Lepton symmetric models. Flavour changing
neutral currents resulting from Kaluza Klein gluon exchange, which typically
arise in the quark sector of split fermion models, are suppressed due to the
localisation of quarks at one point. The separation of quarks and leptons in
the compact extra dimension also acts to suppress the proton decay rate. This
permits the extra dimension to be much larger than that obtained in a previous
construct, with the bound TeV obtained.Comment: 12 pages, references added to match published versio
Monopoles and Instantons in String Theory
In recent work, several classes of solitonic solutions of string theory with
higher-membrane structure have been obtained. These solutions can be classified
according to the symmetry possessed by the solitons in the subspace of the
spacetime transverse to the membrane. Solitons with four-dimensional spherical
symmetry represent instanton solutions in string theory, while those with
three-dimensional spherical symmetry represent magnetic monopole-type
solutions. For both of these classes, we discuss bosonic as well as heterotic
solutions.Comment: 16 page
A non-associative quantum mechanics
A non-associative quantum mechanics is proposed in which the product of three
and more operators can be non-associative one. The multiplication rules of the
octonions define the multiplication rules of the corresponding operators with
quantum corrections. The self-consistency of the operator algebra is proved for
the product of three operators. Some properties of the non-associative quantum
mechanics are considered. It is proposed that some generalization of the
non-associative algebra of quantum operators can be helpful for understanding
of the algebra of field operators with a strong interaction.Comment: one typo in Eq. (23) is correcte
A Consistent Resolution of Possible Anomalies in B^0 --> phi K_S and B^+ --> eta' K^+ Decays
In the framework of R-parity violating (\rpv) supersymmetry, we try to find a
consistent explanation for both recently measured CP asymmetry in B^0 --> phi
K_S decay and the large branching ratio of B^{+/-} --> eta' K^{+/-} decay,
which are inconsistent with the Standard Model (SM) prediction. We also
investigate other charmless hadronic B --> PP and B --> VP decay modes whose
experimental data favor the SM: for instance, recently measured CP asymmetries
in B^0 --> eta^{prime} K_S and B^0 --> J / Psi K_S. We find that all the
observed data can be accommodated for certain values of \rpv couplings.Comment: 14 pages, 2 figures, Revtex, minor changes, to appear in Phys. Rev.
Let
Nuclear reactor power as applied to a space-based radar mission
The SP-100 Project was established to develop and demonstrate feasibility of a space reactor power system (SRPS) at power levels of 10's of kilowatts to a megawatt. To help determine systems requirements for the SRPS, a mission and spacecraft were examined which utilize this power system for a space-based radar to observe moving objects. Aspects of the mission and spacecraft bearing on the power system were the primary objectives of this study; performance of the radar itself was not within the scope. The study was carried out by the Systems Design Audit Team of the SP-100 Project
Bosonisation Excercise in Three Dimensions: Gauged Massive Thirring Model
Bosonisation of the massive Thirring model, with a non-minimal and
non-abelian gauging is studied in 2+1-dimensions. The static abelian model is
solved completely in the large fermion mass limit and the spectrum is obtained.
The non-abelian model is solved for a restricted class of gauge fields. In both
cases explicit expressions for bosonic currents corresponding to the fermion
currents are given.Comment: 11 pages, LaTeX, E-mail: [email protected]
Explicit kinetic heterogeneity: mechanistic models for interpretation of labeling data of heterogeneous cell populations
Estimation of division and death rates of lymphocytes in different conditions
is vital for quantitative understanding of the immune system. Deuterium, in the
form of deuterated glucose or heavy water, can be used to measure rates of
proliferation and death of lymphocytes in vivo. Inferring these rates from
labeling and delabeling curves has been subject to considerable debate with
different groups suggesting different mathematical models for that purpose. We
show that the three models that are most commonly used are in fact
mathematically identical and differ only in their interpretation of the
estimated parameters. By extending these previous models, we here propose a
more mechanistic approach for the analysis of data from deuterium labeling
experiments. We construct a model of "kinetic heterogeneity" in which the total
cell population consists of many sub-populations with different rates of cell
turnover. In this model, for a given distribution of the rates of turnover, the
predicted fraction of labeled DNA accumulated and lost can be calculated. Our
model reproduces several previously made experimental observations, such as a
negative correlation between the length of the labeling period and the rate at
which labeled DNA is lost after label cessation. We demonstrate the reliability
of the new explicit kinetic heterogeneity model by applying it to artificially
generated datasets, and illustrate its usefulness by fitting experimental data.
In contrast to previous models, the explicit kinetic heterogeneity model 1)
provides a mechanistic way of interpreting labeling data; 2) allows for a
non-exponential loss of labeled cells during delabeling, and 3) can be used to
describe data with variable labeling length
Turbulent convection: comparing the moment equations to numerical simulations
The non-local hydrodynamic moment equations for compressible convection are
compared to numerical simulations. Convective and radiative flux typically
deviate less than 20% from the 3D simulations, while mean thermodynamic
quantities are accurate to at least 2% for the cases we have investigated. The
moment equations are solved in minutes rather than days on standard
workstations. We conclude that this convection model has the potential to
considerably improve the modelling of convection zones in stellar envelopes and
cores, in particular of A and F stars.Comment: 10 pages (6 pages of text including figure captions + 4 figures),
Latex 2e with AAS Latex 5.0 macros, accepted for publication in ApJ
Confined Harmonically Interacting Spin-Polarized Fermions in a Magnetic Field: Thermodynamics
We investigate the combined influence of a magnetic field and a harmonic
interparticle interaction on the thermodynamic properties of a finite number of
spin polarized fermions in a confiment potential. This study is an extension
using our path integral approach of symmetrized density matrices for identical
particles. The thermodynamical properties are calculated for a three
dimensional model of N harmonically interacting spin polarized fermions in a
parabolic potential well in the presence of a magnetic field. The free energy
and the internal energy are obtained for a limited number of particles.
Deviations from the thermodynamical limit become negligible for about 100 or
more particles, but even for a smaller number of fermions present in the well,
scaling relations similar to those of the continuum approximation to the
density of states are already satisfied.Comment: 7 pages REVTEX and 8 postscript figures, accepted in Phys. Rev.
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