94,684 research outputs found
Engineering estimates for supersonic flutter of curved shell segments
Engineering estimates for supersonic flutter of curved shell panel
Space Station RT and E Utilization Study
Descriptive information on a set of 241 mission concepts was reviewed to establish preliminary Space Station outfitting needs for technology development missions. The missions studied covered the full range of in-space technology development activities envisioned for early Space Station operations and included both pressurized volume and attached payload requirements. Equipment needs were compared with outfitting plans for the life sciences and microgravity user communities, and a number of potential outfitting additions were identified. Outfitting implementation was addressed by selecting a strawman mission complement for each of seven technical themes, by organizing the missions into flight scenarios, and by assessing the associated outfitting buildup for planning impacts
STOL Simulation Requirements for Development of Integrated Flight/propulsion Control Systems
The role and use of simulation as a design tool in developing integrated systems where design criteria is largely unavailable is well known. This paper addresses additional simulation needs for the development of Integrated Flight/Propulsion Control Systems (IFPCS) which will improve the probability of properly interpreting simulation results. These needs are based on recent experience with power approach flying qualities evaluations of an advanced fighter configuration which incorporated Short Takeoff and Landing (STOL) technologies and earlier experiences with power approach flying qualities evaluations on the AFTI/F-16 program. The use of motion base platforms with axial and normal degrees of freedom will help in evaluating pilot coupling and workload in the presence of high frequency low amplitude axial accelerations produced by high bandwidth airspeed controllers in a gusty environment
A functional central limit theorem for a Markov-modulated infinite-server queue
The production of molecules in a chemical reaction network is modelled as a
Poisson process with a Markov-modulated arrival rate and an exponential decay
rate. We analyze the distributional properties of , the number of molecules,
under specific time-scaling; the background process is sped up by ,
the arrival rates are scaled by , for large. A functional central limit
theorem is derived for , which after centering and scaling, converges to an
Ornstein-Uhlenbeck process. A dichotomy depending on is observed. For
the parameters of the limiting process contain the deviation
matrix associated with the background process.Comment: 4 figure
Statistical description of turbulent transport for flux driven toroidal plasmas
A novel methodology to analyze non-Gaussian probability distribution
functions (PDFs) of intermittent turbulent transport in global full-f
gyrokinetic simulations is presented. In this work, the Auto-Regressive
Integrated Moving Average (ARIMA) model is applied to time series data of
intermittent turbulent heat transport to separate noise and oscillatory trends,
allowing for the extraction of non-Gaussian features of the PDFs. It was shown
that non-Gaussian tails of the PDFs from first principles based gyrokinetic
simulations agree with an analytical estimation based on a two fluid model.Comment: arXiv admin note: text overlap with arXiv:1008.321
High temperature properties of equiatomic FeAl with ternary additions
The aluminide intermetallic compounds are considered potential structural materials for aerospace applications. The B2 binary aluminide FeAl has a melting point in excess of 1500 K, is of simple cubic structure, exits over a wide range of composition with solubility for third elements and is potentially self-protecting in extreme environments. The B2 FeAl compound has been alloyed with 1 to 5 at % ternary additions of Si, Ti, Zr, Hf, Cr, Ni, Co, Nb, Ta, Mo, W, and Re. The alloys were prepared by blending a third elemental powder with prealloyed binary FeAl powder. Consolidation was by hot extrusion at 1250 K. Annealing studies on the extruded rods showed that the third element addition can be classified into three categories based upon the amount of homogenization and the extent of solid solutioning. Constant strain rate compression tests were performed to determine the flow stress as a function of temperature and composition. The mechanical strength behavior was dependent upon the third element homogenization classification
Superconductivity in Organic Compounds with Pseudo-Triangular Lattice
We study spin fluctuation (SF) mediated superconductivity (SC) in a
half-filled square lattice Hubbard model with the transfer matrices -t between
nearest neighbor sites and -t' between a half of next nearest neighbor sites
neighboring along only one of the directions, considering application of
this model to organic kappa-(BEDT-TTF)2X compounds. Varying the t'/t value from
0 to 1, one can interpolate between a square and an equilateral triangular
lattice, the latter giving frustration to antiferromagnetically (AF) coupled
spin systems. Within the fluctuation exchange (FLEX) approximation, we
calculate chi(q,omega), Tc and the SC order parameter for various model
parameter values and find that both AF and SC are suppressed as one approaches
the frustration geometry or |(t'/t)-1| \to 0. The SC phase, however, extends
beyond the AF phase boundary fairly close to t'/t=1 for realistic U/t values.
The order parameter is of x2-y2-type for t'/t1.Comment: 4 pages, 5 eps figures, to appear in J. Phys. Soc. Jp
From Kondo Effect to Fermi Liquid
The Kondo effect has been playing an important role in strongly correlated
electon systems. The important point is that the magnetic impurity in metals is
a typical example of the Fermi liquid. In the system the local spin is
conserved in the ground state and continuity with respect to Coulomb repulsion
is satisfied. This nature is satisfied also in the periodic systems as far
as the systems remain as the Fermi liquid. This property of the Fermi liquid is
essential to understand the cuprate high-Tc superconductors (HTSC). On the
basis of the Fermi liquid theory we develop the transport theory such as the
resistivity and the Hall coefficient in strongly correlated electron systems,
such as HTSC, organic metals and heavy Fermion systems. The significant role of
the vertex corrections for total charge- and heat-currents on the transport
phenomena is explained. By taking the effect of the current vertex corrections
into account, various typical non-Fermi-liquid-like transport phenomena in
systems with strong magnetic and/or superconducting flucutations are explained
within the Fermi liquid theory.Comment: 14 pages, an article for the special edition of JPSJ "Kondo Effect --
40 Years after the Discovery
N\'eel and Spin-Peierls ground states of two-dimensional SU(N) quantum antiferromagnets
The two-dimensional SU(N) quantum antiferromagnet, a generalization of the
quantum Heisenberg model, is investigated by quantum Monte Carlo simulations.
The ground state for is found to be of the N\'eel type with broken
SU(N) symmetry, whereas it is of the Spin-Peierls type for with broken
lattice translational invariance. No intermediate spin-liquid phase was
observed in contrast to previous numerical simulations on smaller lattices
[Santoro et al., Phys. Rev. Lett. {\bf 83} 3065 (1999)].Comment: 4 pages, 4 figure
- …