17,991 research outputs found
Energy and Momentum of a Class of Rotating Gravitational Waves
We calculate energy and momentum for a class of cylindrical rotating
gravitational waves using Einstein and Papapetrou's prescriptions. It is shown
that the results obtained are reduced to the special case of the cylindrical
gravitational waves already available in the literature.Comment: 11 pages, no figure, Late
A concept for improving the dimensional stability of filamentary composites in one direction
Investigation of filamentary composites having high strength and stiffness and a zero thermal coefficient of expansion in one direction shows that advanced filament materials, such as boron, have substantial advantages over conventional filamentary composites. Various other results are discussed, including guidelines and analysis methods for further evaluation
Testing filamentary composites
NOL ring split-dee tensile test has the advantages that the specimen is readily fabricated by winding and the test is performed in a conventional testing machine without special fixtures. Strain gages cannot be mounted, however, and substantial bending moments are introduced
Design and evaluation of three-phase fibrous composite structures
Study reveals composite combination evaluations for boron binder reinforcements for unidirectly reinforced boron/epoxy, glass binder reinforcements for unidirectionally reinforced boron/epoxy, and glass binder reinforcements for unidrectionally reinforced glass/epoxy
Unidirectional composite stiffening
Simple structural elements are explored with configurations selected to best utilize composite materials. Combination of the biaxial properties of beryllium or an isotropic composite with the uniaxial properties of one directional filamentary reinforcement is studied
Influence of constituent properties upon the structural efficiency of fibrous composite shell
Application of fibrous composites to aerospace structures subject to compressive load
Evaluations of filament-reinforced composites for aerospace structural applications
Elastic constant, tensile, and compressive strength analysis for structural efficiency study of filament reinforced sandwich cylindrical shel
X-ray Light Curves and Accretion Disk Structure of EX Hydrae
We present X-ray light curves for the cataclysmic variable EX Hydrae obtained
with the Chandra High Energy Transmission Grating Spectrometer and the Extreme
Ultraviolet Explorer Deep Survey photometer. We confirm earlier results on the
shape and amplitude of the binary light curve and discuss a new feature: the
phase of the minimum in the binary light curve, associated with absorption by
the bulge on the accretion disk, increases with wavelength. We discuss several
scenarios that could account for this trend and conclude that, most likely, the
ionization state of the bulge gas is not constant, but rather decreases with
binary phase. We also conclude that photoionization of the bulge by radiation
originating from the white dwarf is not the main source of ionization, but that
it is heated by shocks originating from the interaction between the inflowing
material from the companion and the accretion disk. The findings in this paper
provide a strong test for accretion disk models in close binary systems.Comment: 19 pages, 4 figures, accepted for publication in the Ap
Energy and momentum of cylindrical gravitational waves. II
Recently Nathan Rosen and the present author obtained the energy and momentum
densities of cylindrical gravitational waves in Einstein's prescription and
found them to be finite and reasonable. In the present paper we calculate the
same in prescriptions of Tolman as well as Landau and Lifshitz and discuss the
results.Comment: 8 pages, LaTex, To appear in Pramana- J. Physic
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