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Search Results: 1 - 10 of 424006 matches for " M. Shi "
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P2P Traffic Optimization Based on Dynamic Network Information Aware  [PDF]
M. L. Lu, Z. Zhang, Y. Shi
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2017, DOI: 10.4236/ijcns.2017.105B009
Peer-to-Peer (P2P) service may damage the interests of Internet Service Provider (ISP) because P2P traffic usually takes a lot of network link bandwidth and even overwhelms some network links. Aimed at the problem, mainstream solutions are usually optimizing P2P traffic through the interaction between applications and underlying network. However, current solutions still have two aspects of defects: one is that the interacted underlying network status information is immutable and can’t reflect the real-time dynamic changes because it is usually configured by ISP. The other is that some solutions may cause excessive traffic localization, which may greatly influence other services in the local network. In order to improve the above two defects and provide P2P users with better service experience, we propose an enhanced application layer traffic optimization scheme, in which more valuable network status information of underlying network is dynamically calculated and provided to P2P application. Extensive simulations demonstrate that our P2P traffic optimization scheme is superior to other solutions in terms of available bandwidth, resource transmission delay and user service experience.
Mechanical memory for photons with orbital angular momentum
H. Shi,M. Bhattacharya
Physics , 2013, DOI: 10.1088/0953-4075/46/15/151001
Abstract: We propose to use an acoustic surface wave as a memory for a photon carrying orbital angular momentum. We clarify the physical mechanism that enables the transfer of information, derive the angular momentum selection rule that must be obeyed in the process, and show how to optimize the optoacoustic coupling. We theoretically demonstrate that high fidelities can be achieved, using realistic parameters, for the transfer of a coherent optical Laguerre-Gaussian state, associated with large angular momentum, to a mechanical shear mode. Our results add a significant possibility to the ongoing efforts towards the implementation of quantum information processing using photonic orbital angular momentum.
Coupling a small torsional oscillator to large optical angular momentum
H. Shi,M. Bhattacharya
Physics , 2013, DOI: 10.1080/09500340.2013.778341
Abstract: We propose a new configuration for realizing torsional optomechanics: an optically trapped windmill-shaped dielectric interacting with Laguerre-Gaussian cavity modes containing both angular and radial nodes. In contrast to existing schemes, our method can couple mechanical oscillators smaller than the optical beam waist to the in-principle unlimited orbital angular momentum that can be carried by a single photon, and thus generate substantial optomechanical interactions. Combining the advantages of small mass, large coupling, and low clamping losses, our work conceptually opens the way for the observation of quantum effects in torsional optomechanics.
Wood Particle-Recycled Glass Fiber Hybrid Composites  [PDF]
Kayode E. Oluwabunmi, Lee M. Smith, Sheldon Q. Shi
Open Journal of Composite Materials (OJCM) , 2017, DOI: 10.4236/ojcm.2017.75018
Abstract: This study was done with the aim of assessing the feasibility of mechanically recycled glass fiber particleboards made from (loblolly pine and longleaf pine) wood particles with epoxy as binder. The modulus of rupture (MOR) and modulus of elasticity (MOE) were evaluated as indicators of mechanical performance. The water absorption rate and thickness swelling rate were also analyzed to investigate the physical performance of the board. An increase of over 80% in MOE values was obtained for the boards with 10 wt%glass fiber inclusion. For the MOR values, there was an increase of over 84.4% in both densities and glass fiber inclusions of all the board densities. However, there was a decrease in MOE when 30 wt% glass fibers were?incorporated into boards with density of 500?kg/m3?and 700?kg/m3. A r-squared value of 0.869 supported the obtained resultthat the correlation between water absorption rate and thickness swelling rate was a function of the density of the composites.
Computing travel time when the exact address is unknown: a comparison of point and polygon ZIP code approximation methods
Ethan M Berke, Xun Shi
International Journal of Health Geographics , 2009, DOI: 10.1186/1476-072x-8-23
Abstract: Using simulated data from New Hampshire and Arizona, we estimated travel times to nearest cancer centers by using: 1) geometric centroid of ZIP code polygons as origins, 2) population centroids as origin, 3) service area rings around each cancer center, assigning subjects to rings by assuming they are evenly distributed within their ZIP code, 4) service area rings around each center, assuming the subjects follow the population distribution within the ZIP code. We used travel times based on street addresses as true values to validate estimates. Population-based methods have smaller errors than geometry-based methods. Within categories (geometry or population), centroid and service area methods have similar errors. Errors are smaller in urban areas than in rural areas.Population-based methods are superior to the geometry-based methods, with the population centroid method appearing to be the best choice for estimating travel time. Estimates in rural areas are less reliable.Spatial accessibility is an important factor in assessing overall access to healthcare, and road-network-based travel time has become a popular way to measure this component of accessibility. As geographic information systems (GIS) become increasingly available, public health practitioners and researchers now have easy-to-use tools to calculate travel times that once were technically and computationally beyond the reach of most, especially for large datasets. A challenge remains, however, in how to estimate subjects' travel times when the exact address is not available. Due to confidentiality and/or data quality reasons, point location information of subjects is often aggregated to larger areal units. The ZIP code is often the finest granularity of geography available to health researchers, and studies of healthcare accessibility or distance are commonly based on travel times estimated from a subject's ZIP code to a known destination. While ZIP codes are actually collection of postal delivery routes
Leptonic Domains in the Early Universe and Their Implications
Xiangdong Shi,George M. Fuller
Physics , 1999, DOI: 10.1103/PhysRevLett.83.3120
Abstract: We extend a treatment of the causal structure of space-time to active-sterile neutrino transformation-based schemes for lepton number generation in the early universe. We find that these causality considerations necessarily lead to the creation of spatial domains of lepton number with opposite signs. Lepton number gradients at the domain boundaries can open a new channel for MSW resonant production of sterile neutrinos. The enhanced sterile neutrino production via this new channel allows considerable tightening of Big Bang Nucleosynthesis constraints on active-sterile neutrino mixing, including the proposed $\nu_\mu \to \nu_s$ solution for the Super Kamiokande atmospheric $\nu_\mu$ deficit, and the four-neutrino schemes proposed to simultaneously fit current neutrino experimental results.
A New Dark Matter Candidate: Non-thermal Sterile Neutrinos
Xiangdong Shi,George M. Fuller
Physics , 1998, DOI: 10.1103/PhysRevLett.82.2832
Abstract: We propose a new and unique dark matter candidate: $\sim 100$ eV to $\sim 10$ keV sterile neutrinos produced via lepton number-driven resonant MSW (Mikheyev-Smirnov-Wolfenstein) conversion of active neutrinos. The requisite lepton number asymmetries in any of the active neutrino flavors range from 10$^{-3}$ to 10$^{-1}$ of the photon number - well within primordial nucleosynthesis bounds. The unique feature here is that the adiabaticity condition of the resonance strongly favors the production of lower energy sterile neutrinos. The resulting non-thermal (cold) energy spectrum can cause these sterile neutrinos to revert to non-relativistic kinematics at an early epoch, so that free-streaming lengths at or below the dwarf galaxy scale are possible. Therefore, the main problem associated with light neutrino dark matter candidates can be circumvented in our model.
Big Bang Nucleosynthesis and Active-Sterile Neutrino Mixing: Evidence for Maximal Mu Neutrino <-> Tau Neutrino Mixing in Super Kamiokande?
Xiangdong Shi,George M. Fuller
Physics , 1998, DOI: 10.1103/PhysRevD.59.063006
Abstract: We discuss Big Bang Nucleosynthesis constraints on maximal $\nu_\mu\leftrightarrow\nu_s$ mixing. Vacuum $\nu_\mu\leftrightarrow\nu_s$ oscillation has been proposed as one possible explanation of the Super Kamiokande atmospheric neutrino data. Based on the most recent primordial abundance measurements, we find that the effective number of neutrino species for Big Bang Nucleosynthesis (BBN) is $N_\nu\la 3.3$. Assuming that all three active neutrinos are light (with masses $\ll 1$ MeV), we examine BBN constraints on $\nu_\mu\leftrightarrow\nu_s$ mixing in two scenarios: (1) a negligible lepton asymmetry (the standard picture); (2) the presence of a large lepton asymmetry which has resulted from an amplification by $\nu_\tau\leftrightarrow\nu_{s'}$ mixing ($\nu_{s'}$ being $\nu_s$ or another sterile neutrino species). The latter scenario has been proposed recently to reconcile the BBN constraints and large-angle $\nu_\mu\leftrightarrow\nu_s$ mixing. We find that the large-angle $\nu_\mu\leftrightarrow\nu_s$ mixing in the first scenario, which would yield $N_\nu\approx 4$, is ruled out as an explanation of the Super Kamiokande data. It is conceivably possible for the $\nu_\mu\leftrightarrow\nu_s$ solution to evade BBN bounds in the second scenario, but only if 200 eV$^2\la m^2_{\nu_\tau}-m^2_{\nu_{s'}}\la 10^4$ eV$^2$ is satisfied, and if $\nu_\tau$ decays non-radiatively with a lifetime $\la 10^3$ years. This mass-squared difference implies 15 eV$\la m_{\nu_\tau}\la 100$ eV if $\nu_{s'}$ is much lighter than $\nu_\tau$. We conclude that maximal (or near maximal) $\nu_\mu\leftrightarrow\nu_\tau$ mixing is a more likely explanation of the Super Kamiokande data.
Anomalous training effect of perpendicular exchange bias in Pt/Co/Pt/IrMn multilayers
Z. Shi,S. M. Zhou
Physics , 2008, DOI: 10.1063/1.3039059
Abstract: A new characteristic is observed in the training effect of perpendicular exchange bias. For Pt/Co/Pt/IrMn multilayers with perpendicular magnetic anisotropy, the magnetization reversal process is accompanied by pinned domain wall motion and the asymmetry of hysteresis loop is always equal to zero during subsequent measurements. It is interesting to find that the exchange field decreases greatly as a function of the cycling number while the coercivity almost does not change. It is clearly demonstrated that the training effect of perpendicular exchange bias strongly depends on the magnetization reversal mechanism of the ferromagnetic layer.
Supermassive Objects as Gamma-Ray Bursters
George M. Fuller,Xiangdong Shi
Physics , 1997, DOI: 10.1086/311477
Abstract: We propose that the gravitational collapse of supermassive objects ($ M\ga 10^4 M_\odot$), either as relativistic star clusters or as single supermassive stars (which may result from stellar mergers in dense star clusters), could be a cosmological source of $\gamma$-ray bursts. These events could provide the seeds of the supermassive black holes observed at the center of many galaxies. Collapsing supermassive objects will release a fraction of their huge gravitational binding energy as thermal neutrino pairs. We show that the accompanying neutrino/antineutrino annihilation-induced heating could drive electron/positron ``fireball'' formation, relativistic expansion, and associated $\gamma$-ray emission. The major advantage of this model is its energetics: supermassive object collapses are far more energetic than solar mass-scale compact object mergers; therefore, the conversion of gravitational energy to fireball kinetic energy in the supermassive object scenario need not be highly efficient, nor is it necessary to invoke directional beaming. The major weakness of this model is difficulty in avoiding a baryon loading problem for one dimensional collapse scenarios.
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