24,304 research outputs found
Delay-dependent robust stability of stochastic delay systems with Markovian switching
In recent years, stability of hybrid stochastic delay systems, one of the important issues in the study of stochastic systems, has received considerable attention. However, the existing results do not deal with the structure of the diffusion but estimate its upper bound, which induces conservatism. This paper studies delay-dependent robust stability of hybrid stochastic delay systems. A delay-dependent criterion for robust exponential stability of hybrid stochastic delay systems is presented in terms of linear matrix inequalities (LMIs), which exploits the structure of the diffusion. Numerical examples are given to verify the effectiveness and less conservativeness of the proposed method
Effective Medium Theory of Filamentous Triangular Lattice
We present an effective medium theory that includes bending as well as
stretching forces, and we use it to calculate mechanical response of a diluted
filamentous triangular lattice. In this lattice, bonds are central-force
springs, and there are bending forces between neighboring bonds on the same
filament. We investigate the diluted lattice in which each bond is present with
a probability . We find a rigidity threshold which has the same value
for all positive bending rigidity and a crossover characterizing bending-,
stretching-, and bend-stretch coupled elastic regimes controlled by the
central-force rigidity percolation point at of the
lattice when fiber bending rigidity vanishes.Comment: 15 pages, 9 figure
Neutron star matter in the quark-meson coupling model in strong magnetic fields
The effects of strong magnetic fields on neutron star matter are investigated
in the quark-meson coupling (QMC) model. The QMC model describes a nuclear
many-body system as nonoverlapping MIT bags in which quarks interact through
self-consistent exchange of scalar and vector mesons in the mean-field
approximation. The results of the QMC model are compared with those obtained in
a relativistic mean-field (RMF) model. It is found that quantitative
differences exist between the QMC and RMF models, while qualitative trends of
the magnetic field effects on the equation of state and composition of neutron
star matter are very similar.Comment: 16 pages, 4 figure
Public vs private administration of rural health insurance schemes: a comparative study in Zhejiang of China.
: Since 2003, China has experimented in some of the country's counties with the private administration of the New Cooperative Medical Scheme (NCMS), a publicly subsidized health insurance scheme for rural populations. Our study compared the effectiveness and efficiency of private vs public administration in four counties in one of China's most affluent provinces in the initial stage of the NCMS's implementation. The study was undertaken in Ningbo city of Zhejiang province. Out of 10 counties in Ningbo, two counties with private administration for the NCMS (Beilun and Ninghai) were compared with two others counties with public administration (Zhenhai and Fenghua), using the following indicators: (1) proportion of enrollees who were compensated for inpatient care; (2) average reimbursement-expense ratio per episode of inpatient care; (3) overall administration cost; (4) enrollee satisfaction. Data from 2004 to 2006 were collected from the local health authorities, hospitals and the contracted insurance companies, supplemented by a randomized household questionnaire survey covering 176 households and 479 household members. In our sample counties, private administration of the NCMS neither reduced transaction costs, nor improved the benefits of enrollees. Enrollees covered by the publicly administered NCMS were more likely to be satisfied with the insurance scheme than those covered by the privately administered NCMS. Experience in the selected counties suggests that private administration of the NCMS did not deliver the hoped-for results. We conclude that caution needs to be exercised in extending private administration of the NCMS
Microdistribution of oxygen in silicon and its effects on electronic properties
The effects of interstitial oxygen on the electrical characteristics of Czochralski-grown silicon crystals were investigated for the first time on a microscale. It was found that the generation of thermal donors is not a direct function of the oxygen concentration. It was further found that the minority carrier life-time decreases with increasing oxygen concentration, on a microscale in as-grown crystals. It was thus shown, again for the first time, that oxygen in as grown crystals is not electronically inert as generally believed. Preannealing at 1200 C commonly employed in device fabrication, was found to suppress the donor generation at 450 C and to decrease the deep level concentrations
Clearing residual planetesimals by sweeping secular resonances in transitional disks: a lone-planet scenario for the wide gaps in debris disks around Vega and Fomalhaut
Extended gaps in the debris disks of both Vega and Fomalhaut have been
observed. These structures have been attributed to tidal perturbations by
multiple super-Jupiter gas giant planets. Within the current observational
limits, however, no such massive planets have been detected. Here we propose a
less stringent `lone-planet' scenario to account for the observed structure
with a single eccentric gas giant and suggest that clearing of these wide gaps
is induced by its sweeping secular resonance. During the depletion of the disk
gas, the planet's secular resonance propagates inward and clears a wide gap
over an extended region of the disk. Although some residual intermediate-size
planetesimals may remain in the gap, their surface density is too low to either
produce super-Earths or lead to sufficiently frequent disruptive collisions to
generate any observable dusty signatures. The main advantage of this
lone-planet sweeping-secular-resonance model over the previous multiple gas
giant tidal truncation scenario is the relaxed requirement on the number of gas
giants. The observationally inferred upper mass limit can also be satisfied
provided the hypothetical planet has a significant eccentricity. A significant
fraction of solar or more massive stars bear gas giant planets with significant
eccentricities. If these planets acquired their present-day kinematic
properties prior to the depletion of their natal disks, their sweeping secular
resonance would effectively impede the retention of neighboring planets and
planetesimals over a wide range of orbital semi-major axes.Comment: 20 pages, 12 figures. Accepted for publication in Ap
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