4,735 research outputs found
Efficient T-CONT-agnostic Bandwidth and Wavelength Allocation for NG-PON2
Dynamic bandwidth and wavelength allocation are used to demonstrate high quality of service (QoS) in time wavelength-division multiplexedâpassive optical networks (TWDM-PONs). Both bandwidth and wavelength assignment are performed on the basis of transmission containers (T-CONTs) and therefore by means of upstream service priority traffic flows. Our medium access control (MAC) protocol therefore ensures consistency in processing alike classes of service across all optical network units (ONUs) in agreement with their QoS figures. For evaluation of the MAC protocol performance, a simulator has been implemented in OPNET featuring a 40 km, 40 Gbps TWDM-PON with four stacked wavelengths at 10 Gbps each and 256 ONUs. Simulation results have confirmed the efficiency of allocating bandwidth to each wavelength and the significant increase of network traffic flow due to adaptive polling from 9.04 to 9.74 Gbps. The benefit of T-CONT-centric allocation has also been measured with respect to packet delay and queue occupancy, achieving low packet delay across all T-CONTs. Therefore, improved NG-PON2 performance and greater efficiency are obtained in this first demonstration of T-CONTs allocated to both wavelength and time.Peer reviewe
Exact Solution of a Yang-Baxter Spin-1/2 Chain Model and Quantum Entanglement
Entanglement is believed to be crucial in macroscopic physical systems for
understanding the collective quantum phenomena such as quantum phase
transitions. We start from and solve exactly a novel Yang-Baxter spin-1/2 chain
model with inhomogeneous and anisotropic short-range interactions. For the
ground state, we show the behavior of neighboring entanglement in the parameter
space and find that the inhomogeneous coupling strengths affect entanglement in
a distinctive way from the homogeneous case, but this would not affect the
coincidence between entanglement and quantum criticality.Comment: 7 pages, 3 figure
Structural Identification of Lentinus edodes Cellulose Derivative that Inhibits Aflatoxin Production by Aspergillus flavus
Purpose: To identify the structures of cellulose-extract derivative (CED) formed by heating Lentinus edodes cellulose in water surroundings that can efficiently inhibit aflatoxin production by Aspergillus flavus.Methods: CED was purified on Sepharose CL-6B columns, and then structurally characterized using amino acid analyzer, gas chromatography, Fourier transform infrared spectroscopy, and polyacrylamide gel electrophoresis.Results: CED completely inhibited aflatoxin AFB1 production by A. flavus at concentrations â„ 100 ÎŒg/ mL. Chemical analysis indicated that CED contained 82 % carbohydrate and 18 % protein and has a molecular weight of approximately 24 kDa. Monosaccharide component analysis indicates that glucose was the predominant monosaccharide of CED. Analysis by Smith degradation and enzymatic hydrolysis indicate that there were only (1, 4)-glycosidic linkages in the CED polysaccharide chains. The protein backbone of CED contained 15 kinds of amino acid with higher levels of glutamic acid, aspartic acid, leucine and alanine.Conclusion: CED was identified as a complex of peptide and polysaccharide structures possessing ÎČ- (1, 4)-glucan backbones, and it provides a theoretical basis for developing polysaccharide preparations to control aflatoxin contamination with medical and food science applications.Keywords: Aflatoxin B1, Lentinus edodes, Aspergillus flavus, Cellulose derivative, Structure identification, Amino aci
Large-Scale Sunyaev-Zel'dovich Effect: Measuring Statistical Properties with Multifrequency Maps
We study the prospects for extracting detailed statistical properties of the
Sunyaev-Zel'dovich (SZ) effect associated with large scale structure using
upcoming multifrequency CMB experiments. The greatest obstacle to detecting the
large-angle signal is the confusion noise provided by the primary anisotropies
themselves, and to a lesser degree galactic and extragalactic foregrounds. We
employ multifrequency subtraction techniques and the latest foregrounds models
to determine the detection threshold for the Boomerang, MAP (several microK)
and Planck CMB (sub microK) experiments. Calibrating a simplified biased-tracer
model of the gas pressure off recent hydrodynamic simulations, we estimate the
SZ power spectrum, skewness and bispectrum through analytic scalings and N-body
simulations of the dark matter. We show that the Planck satellite should be
able to measure the SZ effect with sufficient precision to determine its power
spectrum and higher order correlations, e.g. the skewness and bispectrum.
Planck should also be able to detect the cross correlation between the SZ and
gravitational lensing effect in the CMB. Detection of these effects will help
determine the properties of the as yet undetected gas, including the manner in
which the gas pressure traces the dark matter.Comment: 13 ApJ pages, 11 figures; typos and figure 5 revised; submitted to
Ap
Weak Lensing by Large-Scale Structure: A Dark Matter Halo Approach
Weak gravitational lensing observations probe the spectrum and evolution of
density fluctuations and the cosmological parameters which govern them but are
currently limited to small fields and subject to selection biases. We show how
the expected signal from large-scale structure arises from the contributions
from and correlations between individual halos. We determine the convergence
power spectrum as a function of the maximum halo mass and so provide the means
to interpret results from surveys that lack high mass halos either through
selection criteria or small fields. Since shot noise from rare massive halos is
mainly responsible for the sample variance below 10', our method should aid our
ability to extract cosmological information from small fields.Comment: 4 ApJ pages, 3 figures; submitted to ApJ Letter
CMBR Weak Lensing and HI 21-cm Cross-correlation Angular Power Spectrum
Weak gravitational lensing of the CMBR manifests as a secondary anisotropy in
the temperature maps. The effect, quantified through the shear and convergence
fields imprint the underlying large scale structure (LSS), geometry and
evolution history of the Universe. It is hence perceived to be an important
observational probe of cosmology. De-lensing the CMBR temperature maps is also
crucial for detecting the gravitational wave generated B-modes. Future
observations of redshifted 21-cm radiation from the cosmological neutral
hydrogen (HI) distribution hold the potential of probing the LSS over a large
redshift range. We have investigated the correlation between post-reionization
HI signal and weak lensing convergence field. Assuming that the HI follows the
dark matter distribution, the cross-correlation angular power spectrum at a
multipole \ell is found to be proportional to the cold dark matter power
spectrum evaluated at \ell/r, where r denotes the comoving distance to the
redshift where the HI is located. The amplitude of the ross-correlation depends
on quantities specific to the HI distribution, growth of perturbations and also
the underlying cosmological model. In an ideal ituation, we found that a
statistically significant detection of the cross-correlation signal is
possible. If detected, the cross-correlation signal hold the possibility of a
joint estimation of cosmological parameters and also test various CMBR
de-lensing estimators.Comment: 14 pages, 4 figures, publishe
Model-driven design of a fast material removal electrical discharge machine
This open access article is distributed under a Creative Commons Attribution (CC-BY) 4.0 license. In order to minimize cost of machining, modern aerospace components are highly unitized to utilize functions of multi-axes CNC machining centres. However, PCD tools are preferred for machining of titanium alloys and metal matrix composites but they are hard to grind. A new fast material removal electric discharge machine suitable for small PCD workpiece machining has been developed from an innovative model consisting both high and low frequency response actuators and a dual stage non-linear control algorithm. This innovative approach has been proved successful in the single axis machine prototype and the fast material removal rate has been verified a series of tests and the outcomes were verified
Magnetic fields from reionisation
We present a complementary study to a new model for generating magnetic
fields of cosmological interest. The driving mechanism is the photoionisation
process by photons provided by the first luminous sources. Investigating the
transient regime at the onset of inhomogeneous reionisation, we show that
magnetic field amplitudes as high as Gauss can be obtained
within a source lifetime. Photons with energies above the ionisation threshold
accelerate electrons, inducing magnetic fields outside the Stroemgren spheres
which surround the ionising sources. Thanks to their mean free path, photons
with higher energies propagate further and lead to magnetic field generation
deeper in the neutral medium. We find that soft X-ray photons could contribute
to a significant premagnetisation of the intergalactic medium at a redshift of
z=15.Comment: accepted for publication in A&
A statistical investigation of the rheological properties of magnesium phosphate cement
Magnesium phosphate cement (MPC) is a promising material applied for rapid patch
repairing in civil engineering and waste immobilisation in nuclear industry. However, the
rheological properties of this new binder material which highly affects its engineering application,
is to be explored. The current work aims at investigating the rheological properties of MPC along
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with determining the optimum conditions to obtain MPC materials with desirable rheological
performances. The Response Surface Methodology (RSM) accompanied by Central Composite
Design (CCD) were adopted to establish mathematical model describing the rheological
characteristics of MPC in terms of yield stress (Pa) and plastic viscosity (Pa.s), as a function of
three independent variables namely W/S ratio, M/P ratio and Borax dosage. The analysis of
variance (ANOVA) was also conducted to assess the significance and adequacy of the regression
models attained. The results showed that the M/P ratio and Borax dosage could affect significantly
the yield stress of MPC, while W/S ratio was the significant coefficient influencing the plastic
viscosity. The numerical optimised values of the W/S ratio, M/P ratio and Borax dosage were 0.25,
8.97 and 0.17 respectively, and a MPC paste with desirable rheological characteristics (yield stress
of 0.40 Pa and plastic viscosity of 0.93 Pa.s) can be obtained. Further experiments will be carried
out to verify the predicted optimum conditions and study the interactions between the factors in
relation to the responses
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