9,746 research outputs found
How little we know about deficit policy effects
We use a simple model to show why previous empirical studies of budget policy effects are flawed. Due to an identification problem, those studies' findings can be shown to be consistent with policies either mattering or not. We argue that this problem is difficult and not likely to be resolved soon.Budget deficits ; Fiscal policy
Thermal barrier coating evaluation needs
A 0.025 cm (0.010 in) thick thermal barrier coating (TBC) applied to turbine airfoils in a research gas turbine engine provided component temperature reductions of up to 190 C. These impressive temperature reductions can allow increased engine operating temperatures and reduced component cooling to achieve greater engine performance without sacrificing component durability. The significant benefits of TBCs are well established in aircraft gas turbine engine applications and their use is increasing. TBCs are also under intense development for use in the Low Heat Rejection (LHR) diesel engine currently being developed and are under consideration for use in utility and marine gas turbines. However, to fully utilize the benefits of TBCs it is necessary to accurately characterize coating attributes that affect the insulation and coating durability. The purpose there is to discuss areas in which nondestructive evaluation can make significant contributions to the further development and full utilization of TBCs for aircraft gas turbine engines and low heat rejection diesel engines
Nearctic \u3ci\u3eAcleris\u3c/i\u3e: Resurrection of \u3ci\u3eA. Stadiana\u3c/i\u3e and a Revised Identity for \u3ci\u3eA. Semiannula\u3c/i\u3e (Lepidoptera: Tortricidae)
Type study showed that Acleris stadiana (Barnes & Busck), currently considered a junior synonym of A. semiannula (Robinson), is in fact a distinct taxon. Although superficially similar, these taxa differ markedly in genital structure. In males of A. semiannula, the aedeagus is short, broad, and virtually straight, whereas in those of A. stadiana, it is long, thin, and sharply bent. What was known in literature as A. semiannula proved to be A. stadiĀana. We redefine both A. semiannula and the resurrected A. stadiana
Path-integral virial estimator for reaction rate calculation based on the quantum instanton approximation
The quantum instanton approximation is a type of quantum transition state
theory that calculates the chemical reaction rate using the reactive flux
correlation function and its low order derivatives at time zero. Here we
present several path-integral estimators for the latter quantities, which
characterize the initial decay profile of the flux correlation function. As
with the internal energy or heat capacity calculation, different estimators
yield different variances (and therefore different convergence properties) in a
Monte Carlo calculation. Here we obtain a virial-type estimator by using a
coordinate scaling procedure rather than integration by parts, which allows
more computational benefits. We also consider two different methods for
treating the flux operator, i.e., local-path and global-path approaches, in
which the latter achieves a smaller variance at the cost of using second-order
potential derivatives. Numerical tests are performed for a one-dimensional
Eckart barrier and a model proton transfer reaction in a polar solvent, which
illustrates the reduced variance of the virial estimator over the corresponding
thermodynamic estimator.Comment: 23 pages, 5 figures, 1 tabl
Rough Riders: From Saddle To Battle, \u27Texans Always Move\u27Em
The regimental history, as a subgenre in American literature, has endured for well over 100 years. Eloquent writers and disciplined historians, rarely one and the same, have told the story of the men who have fought America\u27s wars. There are a few superb unit histories and many more good ones, but t...
Thermal barrier coatings for gas turbine and diesel engines
The present state of development of thin thermal barrier coatings for aircraft gas turbine engines and thick thermal barrier coatings for truck diesel engines is assessed. Although current thermal barrier coatings are flying in certain gas turbine engines, additional advances will be needed for future engines. Thick thermal barrier coatings for truck diesel engines have advanced to the point where they are being seriously considered for the next generation of engine. Since coatings for truck engines is a young field of inquiry, continued research and development efforts will be required to help bring this technology to commercialization
Giant Antiferromagnetically Coupled Moments in a Molecule-Based Magnet with Interpenetrating Lattices
The molecule-based magnet [Ru(OCMe)][Cr(CN)] contains two
weakly-coupled, interpenetrating sublattices in a body-centered cubic
structure. Although the field-dependent magnetization indicates a metamagnetic
transition from an antiferromagnet to a paramagnet, the hysteresis loop also
exhibits a substantial magnetic remanance and coercive field uncharacteristic
of a typical metamagnet. We demonstrate that this material behaves like two
giant moments with a weak antiferromagnetic coupling and a large energy barrier
between the orientations of each moment. Because the sublattice moments only
weakly depend on field in the transition region, the magnetic correlation
length can be directly estimated from the magnetization.Comment: 3 figure
The Dynamics of Abell 2125
We present 371 galaxy velocities in the field of the very rich cluster Abell
2125 (z~0.25). These were determined using optical spectroscopy collected over
several years from both the WIYN 3.5m telescope and NOAO Mayall 4m telescope.
Prior studies at a variety of wavelengths (radio, optical, and X-ray) have
indicated that A2125 is a likely cluster-cluster merger, a scenario which we
are able to test using our large velocity database. We identified 224 cluster
galaxies, which were subjected to a broad range of statistical tests using both
positional and velocity information to evaluate the cluster dynamics and
substructure. The tests confirmed the presence of substructures within the
Abell 2125 system at high significance, demonstrating that A2125 is a complex
dynamical system. Comparison of the test results with existing simulations
strengthens the merger hypothesis, and provides clues about the merger geometry
and stage. The merger model for the system can reconcile A2125's low X-ray
temperature and luminosity with its apparently high richness, and might also
explain A2125's high fraction of active galaxies identified in prior radio and
optical studies.Comment: 34 pages, including tables and 3 color figures; to appear in Ap
Level density and level-spacing distributions of random, self-adjoint, non-Hermitian matrices
We investigate the level-density and level-spacing distribution
of random matrices where is a (diagonal)
inner-product and is a random, real symmetric or complex Hermitian matrix
with independent entries drawn from a probability distribution with zero
mean and finite higher moments. Although not Hermitian, the matrix is
self-adjoint with respect to and thus has purely real eigenvalues. We find
that the level density is independent of the underlying
distribution , is solely characterized by , and therefore generalizes
Wigner's semicircle distribution . We find that the level-spacing
distributions are independent of , are dependent upon the
inner-product and whether is real or complex, and therefore generalize
the Wigner's surmise for level spacing. Our results suggest -dependent
generalizations of the well-known Gaussian Orthogonal Ensemble (GOE) and
Gaussian Unitary Ensemble (GUE) classes.Comment: 5 pages, 5 figures, revised tex
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