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971.
Rajat Kumar Singh Rajiv Srivastava Yatindra Nath Singh 《Optical and Quantum Electronics》2007,39(14):1153-1165
Optical packet switching provides high speed, data rate/format transparency, efficient use of bandwidth and flexibility. The
major problem in the implementation of “all-optical” switching is contention which occurs when two or more packets arrive
at the same time for the same destination. To resolve the contention, we have proposed an optical packet switch architecture
based on WDM loop buffer memory in the feedback configuration. In that architecture, the contending packets are stored in
a loop buffer module, and routed in the free time slots. The buffering duration in the recirculating loop is limited by a
circulation limit. The analysis was been done to obtain the maximum number of allowed circulations. This paper proposes improved
version of that optical packet switch architecture, to increase the number of maximum allowed circulations. The modification
is done either by adding an extra erbium doped fiber amplifier (EDFA) in the original switch or by replacing the core space
switch with arrayed waveguide grating (AWG). The performance analysis has been done by the simulations. 相似文献
972.
David Ruelle 《Communications in Mathematical Physics》2007,270(1):233-265
We analyze the dynamics of a simple but nontrivial classical Hamiltonian system of infinitely many coupled rotators. We assume
that this infinite system is driven out of thermal equilibrium either because energy is injected by an external force (Case
I), or because heat flows between two thermostats at different temperatures (Case II). We discuss several possible definitions
of the entropy production associated with a finite or infinite region, or with a partition of the system into a finite number
of pieces. We show that these definitions satisfy the expected bounds in terms of thermostat temperatures and energy flow. 相似文献
973.
We compute the asymptotics of a block Toeplitz determinant which arises in the classical dimer model for the triangular lattice when considering the monomer-monomer correlation function. The model depends on a parameter interpolating between the square lattice (t = 0) and the triangular lattice (t = 1), and we obtain the asymptotics for 0 < t ≤ 1. For 0 < t < 1 we apply the Szegö Limit Theorem for block Toeplitz determinants. The main difficulty is to evaluate the constant term in the asymptotics, which is generally given only in a rather abstract form. 相似文献
974.
Yoko Hirohara Yoshitaka OKawa Toshifumi Mihashi Tatsuo Yamaguchi Naoki Nakazawa Yasuko Tsuruga Hiroyuki Aoki Naoyuki Maeda Ichiro Uchida Takashi Fujikado 《Optical Review》2007,14(3):151-158
The purpose of this paper was to investigate the feasibility of a newly developed hyperspectral fundus imaging camera with
a liquid crystal tunable filter. The intensities of different wavelengths of light transmitted through an artery, vein, and
the area surrounding these vessels and reflected out were measured, and the differential spectral absorptions were analyzed.
Measurements were made from 16 normal eyes and from two artificial capillaries. The ratios of absorption (ROA) of arteries
to veins from 500 to 580 nm (range 1) and from 600 to 720 nm (range 2) were calculated. For all eyes, the ROArange1 was larger than ROArange2. The ROA obtained from the artificial capillary filled with blood saturated with oxygen or nitrogen was similar to that of
simulated data of oxy- and deoxyhemoglobin extinction rate. Most ROAs of human eyes were lower than those of the simulated
data and the artificial capillaries. Oxygen saturation analysis by hyperspectral fundus imaging of retinal vessels were qualitatively
in agreement with thein vitro analysis or simulated values. However, further improvements are necessary to evaluate the oxygen saturation quantitatively
in the retinal blood vessels. 相似文献
975.
Jaume Llibre Marco Antonio Teixeira Joan Torregrosa 《Mathematical Physics, Analysis and Geometry》2007,10(3):237-249
The goal of this paper is double. First, we illustrate a method for studying the bifurcation of limit cycles from the continuum
periodic orbits of a k-dimensional isochronous center contained in ℝ
n
with n ⩾ k, when we perturb it in a class of differential systems. The method is based in the averaging theory. Second, we consider a particular polynomial differential
system in the plane having a center and a non-rational first integral. Then we study the bifurcation of limit cycles from
the periodic orbits of this center when we perturb it in the class of all polynomial differential systems of a given degree.
As far as we know this is one of the first examples that this study can be made for a polynomial differential system having
a center and a non-rational first integral.
The first and third authors are partially supported by a MCYT/FEDER grant MTM2005-06098-C01, and by a CIRIT grant number 2005SGR-00550.
The second author is partially supported by a FAPESP–BRAZIL grant 10246-2. The first two authors are also supported by the
joint project CAPES–MECD grant HBP2003-0017. 相似文献
976.
Michal Demetrian 《International Journal of Theoretical Physics》2007,46(3):652-663
The vacuum decay in a de Sitter universe is studied for the class of effective inflaton potentials that curvature at the top
is less than as well as greater than a critical value determined previously. By comparing the actions of the Hawking - Moss
instanton and the Coleman - de Luccia instanton(s) the mode of vacuum decay is determined in this critical situation. 相似文献
977.
Eric Weise 《Czechoslovak Journal of Physics》2005,55(1):A27-A34
COMPASS is a fixed target experiment at CERN studying nucleon spin structure in polarised deep inelastic muon nucleon scattering and hadron spectroscopy using hadron beams. The main goal of the COMPASS spin physics program is the measurement of the helicity contribution of the gluons to the nucleon spin, ΔG. This quantity is accessible via the photon-gluon-fusion process which can be selected by open charm production or production of hadron pairs with large transverse momenta. The spin physics program of COMPASS includes also measurements with a transversely polarised target. These allow to measure the transverse structure function.COMPASS has up to now successfully finished three runs with a muon beam of 160 GeV and a longitudinally polarized6LiD target in the years 2002, 2003 and 2004. An overview of the physics addressed by the muon program, with an emphasis on the ΔG/G measurement will be presented. The status of the analysis of the highpt hadron pairs, open charm, longitudinal and transverse asymmetries will be reviewed. 相似文献
978.
Lin Wang Heqing Yang Hua Zhao Ru Yu Shi Liu Bao Bin Liu 《Applied Physics A: Materials Science & Processing》2011,102(1):61-68
The present work reports on novel four-layer thermally driven piezoresistive cantilevers implemented in one- and two-dimensional
arrays for parallel proximity scanning. There, the heater (metallic meander), the piezoresistive deflection sensor, and the
metal actuation film with significantly higher thermal expansion coefficient make up separate layers. Actuation efficiency
and cross-talk of the novel cantilever design are studied and compared with two recent designs: thin metallic film and ion-implanted
heater. The novel actuator, integrated on a 240 μm long and 3 μm thick silicon cantilever and supplied by V
dc=1 V enables deflections up to 5 μm of the AFM-tip with an actuation efficiency of about 170 nm/mW and suppressed cross-talk
between actuator and sensor. 相似文献
979.
Nanoflakes-built pyrite FeS2 microspheres were synthesized through a simple solvothermal process in mixed solvents of N, N-dimethytformamide and ethylene
glycol without using any surfactant. Both the composition of the solvents and urea were key factors for the formation of the
uniform products. It was found that the flake-like intermediate products transformed into FeS2 nanoflakes in situ in the early stage and Ostwald ripening growth mechanism would contribute to the uniformity of the final
products. Electrochemical studies revealed that the nanoflakes-built pyrite FeS2 microspheres exhibited large lithium storage capacities. This method can be easily controlled and is expected to be extendable
to the fabrication of other metal chalcogenides with controlled shape and structure. 相似文献
980.
M. A. Kudryashov A. I. Mashin A. S. Tyurin A. E. Fedosov G. Chidichimo G. De Filpo 《Technical Physics》2011,56(1):92-96
Silver/polyacrylonitrile (Ag/PAN) nanocomposites are synthesized at the stage of simultaneous acrylonitrile polymerization
and the reduction of silver ions from a mixture of silver nitrate AgNO3, acrylonitrile, and a photoinitiator. The synthesized films are transparent in the visible region and are characterized by
a uniform dispersion of silver nanoparticles in a PAN matrix without any macroscopic agglomeration. The effects of the metal
salt and photoinitiator concentrations on the size and density of metal nanoparticles in a composite are revealed. 相似文献