9,895 research outputs found
Asymptotic analysis and spectrum of three anyons
The spectrum of anyons confined in harmonic oscillator potential shows both
linear and nonlinear dependence on the statistical parameter. While the
existence of exact linear solutions have been shown analytically, the nonlinear
dependence has been arrived at by numerical and/or perturbative methods. We
develop a method which shows the possibility of nonlinearly interpolating
spectrum. To be specific we analyse the eigenvalue equation in various
asymptotic regions for the three anyon problem.Comment: 28 pages, LaTeX, 2 Figure
Brownian Motion on a Sphere: Distribution of Solid Angles
We study the diffusion of Brownian particles on the surface of a sphere and
compute the distribution of solid angles enclosed by the diffusing particles.
This function describes the distribution of geometric phases in two state
quantum systems (or polarised light) undergoing random evolution. Our results
are also relevant to recent experiments which observe the Brownian motion of
molecules on curved surfaces like micelles and biological membranes. Our
theoretical analysis agrees well with the results of computer experiments.Comment: 11 pages, two figures, Fig2 in Colour,references update
Queueing analysis of a canonical model of real-time multiprocessors
A logical classification of multiprocessor structures from the point of view of control applications is presented. A computation of the response time distribution for a canonical model of a real time multiprocessor is presented. The multiprocessor is approximated by a blocking model. Two separate models are derived: one created from the system's point of view, and the other from the point of view of an incoming task
Characterization of real-time computers
A real-time system consists of a computer controller and controlled processes. Despite the synergistic relationship between these two components, they have been traditionally designed and analyzed independently of and separately from each other; namely, computer controllers by computer scientists/engineers and controlled processes by control scientists. As a remedy for this problem, in this report real-time computers are characterized by performance measures based on computer controller response time that are: (1) congruent to the real-time applications, (2) able to offer an objective comparison of rival computer systems, and (3) experimentally measurable/determinable. These measures, unlike others, provide the real-time computer controller with a natural link to controlled processes. In order to demonstrate their utility and power, these measures are first determined for example controlled processes on the basis of control performance functionals. They are then used for two important real-time multiprocessor design applications - the number-power tradeoff and fault-masking and synchronization
Structural, optical and nanomechanical properties of (1 1 1) oriented nanocrystalline ZnTe thin films
Structural, optical and nanomechanical properties of nanocrystalline Zinc Telluride (ZnTe) films
of thickness upto 10 microns deposited at room temperature on borosilicate glass substrates are reported.
X-ray diffraction patterns reveal that the films were preferentially oriented along the (1 1 1) direction.
The maximum refractive index of the films was 2.74 at a wavelength of 2000 nm. The optical band gap
showed strong thickness dependence. The average film hardness and Young’s modulus obtained from loaddisplacement
curves and analyzed by Oliver-Pharr method were 4 and 70 GPa respectively. Hardness of
(1 1 1) oriented ZnTe thin films exhibited almost 5 times higher value than bulk. The studies show clearly
that the hardness increases with decreasing indentation size, for indents between 30 and 300 nm in depth
indicating the existence of indentation size effect. The coefficient of friction for these films as obtained from
the nanoscratch test was ∼0.4.Financial support
in the form of fellowships to MSRNK and SK from the
ACRHEM project of DRDO is acknowledged
Jet stability, dynamics and energy transport
Relativistic jets carry energy and particles from compact to very large
scales compared with their initial radius. This is possible due to their
remarkable collimation despite their intrinsic unstable nature. In this
contribution, I review the state-of-the-art of our knowledge on instabilities
growing in those jets and several stabilising mechanisms that may give an
answer to the question of the stability of jets. In particular, during the last
years we have learned that the limit imposed by the speed of light sets a
maximum amplitude to the instabilities, contrary to the case of classical jets.
On top of this stabilising mechanism, the fast growth of unstable modes with
small wavelengths prevents the total disruption and entrainment of jets. I also
review several non-linear processes that can have an effect on the collimation
of extragalactic and microquasar jets. Within those, I remark possible causes
for the decollimation and decelleration of FRI jets, as opposed to the
collimated FRII's. Finally, I give a summary of the main reasons why jets can
propagate through such long distances.Comment: For the proceedings of High Energy Phenomena in Relativistic Outflows
III (HEPRO III, IJMPD, accepted). 12 page
Synchronization and fault-masking in redundant real-time systems
A real time computer may fail because of massive component failures or not responding quickly enough to satisfy real time requirements. An increase in redundancy - a conventional means of improving reliability - can improve the former but can - in some cases - degrade the latter considerably due to the overhead associated with redundancy management, namely the time delay resulting from synchronization and voting/interactive consistency techniques. The implications of synchronization and voting/interactive consistency algorithms in N-modular clusters on reliability are considered. All these studies were carried out in the context of real time applications. As a demonstrative example, we have analyzed results from experiments conducted at the NASA Airlab on the Software Implemented Fault Tolerance (SIFT) computer. This analysis has indeed indicated that in most real time applications, it is better to employ hardware synchronization instead of software synchronization and not allow reconfiguration
Does Corporate Performance Improve After Mergers?
We examine the post-acquisition operating performance of merged firms using a sample of the 50 largest mergers between U.S. public industrial firms completed in the period 1979 to 1983. The results indicate that merged firms have significant improvement in asset productivity relative to their industries after the merger, leading to higher post-merger operating cash flow returns. Sample firms maintain their capital expenditure and R&D rates relative to their industries after the merger, indicating that merged firms do not reduce their long-term investments. There is a strong positive relation between postmerger increases in operating cash flows and abnormal stock returns at merger announcements, indicating that expectations of economic improvements underlie the equity revaluations of the merging firms.
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