712 research outputs found
A Secure Traitor Tracing Scheme against Key Exposure
Copyright protection is a major issue in distributing digital content. On the
other hand, improvements to usability are sought by content users. In this
paper, we propose a secure {\it traitor tracing scheme against key exposure
(TTaKE)} which contains the properties of both a traitor tracing scheme and a
forward secure public key cryptosystem. Its structure fits current digital
broadcasting systems and it may be useful in preventing traitors from making
illegal decoders and in minimizing the damage from accidental key exposure. It
can improve usability through these properties.Comment: 5 pages, IEEE International Symposium on Information Theory 2005
(ISIT 2005
Perturbations of Spacetime around a Stationary Rotating Cosmic String
We consider the metric perturbations around a stationary rotating Nambu-Goto
string in Minkowski spacetime. By solving the linearized Einstein equations, we
study the effects of azimuthal frame-dragging around the rotation axis and
linear frame-dragging along the rotation axis, the Newtonian logarithmic
potential, and the angular deficit around the string as the potential mode. We
also investigate gravitational waves propagating off the string and propagating
along the string, and show that the stationary rotating string emits
gravitational waves toward the directions specified by discrete angles from the
rotation axis. Waveforms, polarizations, and amplitudes which depend on the
direction are shown explicitly.Comment: 30 pages, 6 figures; Minor corrections, references added, published
version in Physical Review
Solitonic Gravastars in a U(1) gauge Higgs model
We numerically obtain gravastar solutions as nontopological solitons in a
system that consists of a U(1) gauge Higgs model with a complex scalar field
and Einstein gravity. The solitonic gravastar solutions are compact enough to
have a photon sphere.Comment: 9 pages, 6 figure
TetraÂchlorido[(diphenylÂphosphino)diphenylÂphosphine oxide-κO]zirconium(IV) benzene monosolvate
In the title centrosymmetric mononuclear ZrIV compound, [ZrCl4{P(O)(C6H5)2P(C6H5)2}2]·C6H6, the central ZrIV ion is coordinated by two O atoms from two symmetry-related (diphenylÂphosphino)diphenylÂphosphine ligands and four Cl atoms in a distorted octahedral geometry with the four Cl atoms in the equatorial positions. The molÂecule lies about a center of inversion and the benzene solvent molÂecule about another center of inversion. The P=O bond [1.528 (2) Å] is slightly longer than a typical P=O double bond (average 1.500 )
Strings in five-dimensional anti-de Sitter space with a symmetry
The equation of motion of an extended object in spacetime reduces to an
ordinary differential equation in the presence of symmetry. By properly
defining of the symmetry with notion of cohomogeneity, we discuss the method
for classifying all these extended objects. We carry out the classification for
the strings in the five-dimensional anti-de Sitter space by the effective use
of the local isomorphism between \SO(4,2) and \SU(2,2). We present a
general method for solving the trajectory of the Nambu-Goto string and apply to
a case obtained by the classification, thereby find a new solution which has
properties unique to odd-dimensional anti-de Sitter spaces. The geometry of the
solution is analized and found to be a timelike helicoid-like surface
Vertical-Vibration Suppressing Design of Accumulator with New Vibration-Measuring Method
A compressor was developed using R32 which was a low GWP R32 refrigerant for coping with global warming. However, there is a tendency for vibrations of a compressor to also increase because the circulation of refrigerant increases according to specification for using R32 refrigerant. Since large vibrations of a compressor causes outdoor units to generate solid propagation sound, there is a need for a technology that can reduce vibration of a compressor. However, a vibration-measuring method to analyze such vibration had not been fully developed and it was difficult to specify the cause. Accordingly, a new vibration-measuring method was developed specifically for compressors. The use of this measuring method allowed to discover that one of the unresolved problems with sound of outdoor units was the vertical vibration of the accumulator housed in the compressor. Moreover, it was found that the accumulator vibrates vertically due to the acoustic resonance inside the casing, which led to develop a new (accumulator) design with a focus on resonance. There is a type of spatial resonance inside an accumulator that has a phase difference with the antinode of sound pressure appearing at the upper and lower ends of the space. The vertical force caused by the difference in the sound pressure becomes excitation force, which then causes vertical vibration of the accumulator. Therefore, preventing this resonance from occurring can help suppress the vertical vibration. In order to prevent the generation of resonance, a plate-shaped reflection member was placed inside the accumulator, and it proved to be effective in suppressing the vertical vibration
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