New Upper Bounds for Ramsey Numbers

AbstractThe Ramsey numberR(G1,G2) is the smallest integerpsuch that for any graphGonpvertices eitherGcontainsG1orGcontainsG2, whereGdenotes the complement ofG. LetR(m,n)=R(Km,Kn). Some new upper bound formulas are obtained forR(G1,G2andR(m,n), and we derive some new upper bounds for Ramsey numbers here

Network Optimization for DHT-based Applications

International audienceP2P platforms have been criticized because of the heavy strain that some P2P services can inflict on costly inter-domain links of network operators. It is therefore necessary to develop network optimization schemes for controlling the load generated by P2P platforms on an operator network. Previous focus on network optimization has been mostly on centralized tracker-based systems. However, in recent years multiple DHT-based P2P networks are widely deployed due to their scalability and fault tolerance, and these networks have even been considered as platforms for commercial services..Thereby, finding network optimization for DHT-based P2P applications has potentially large practical impacts. In this paper, we present THash, a simple scheme to implement an effective distributed network optimization for DHT systems. THash is based on standard DHT put/get semantics and utilizes a triple hash method to guide the DHT clients sharing resources with peers in proper domains. We have implemented THash in a major P2P application (PPLive) by using the standard ALTO/P4P protocol as the network information source. We conducted realistic experiments over the network and observed that compared with Native DHT, THash only generated 45.5\% and 35.7\% of inter-PID and inter-AS traffic, and at the same time shortened the average downloading time by 13.8\% to 22.1\%

Charged bottomonium-like structures Zb(10610)Z_b(10610) and Zb(10650)Z_b(10650)

The observation of two charged bottomonium-like structures $Z_b(10610)$ and $Z_b(10650)$ has stimulated extensive studies of the properties of $Z_b(10610)$ and $Z_b(10650)$. In this talk, we briefly introduce the research status of $Z_b(10610)$ and $Z_b(10650)$ combined with our theoretical progress.Comment: 6 pages, 1 table, 5 figures. Plenary talk given at the international conference The Fifth Asia-Pacific Conference on Few-Body Systems in Physics 2011 (APFB2011), Seoul, Republic of Korea, 22-26 August 201

Image-based 3D Scene Reconstruction and Rescue Simulation Framework for Railway Accidents

Although the railway transport is regarded as a relatively safe transportation tool, many railway accidents have still happened worldwide. In this research, an image-based 3D scene reconstruction framework was proposed to help railway accident emergency rescues. Based on the improved constrained non-linear least square optimization, the framework can automatically model the accident scene with only one panorama in a short time. We embedded the self-developed global terrain module into the commercial visualization and physics engine, which makes the commercial engine can be used to render the static scene at anywhere and simulate the dynamic rescue process respectively. In addition, a Head Mounted Device (HMD) was integrated into this framework to allow users to verify their rescue plan and review previous railway accidents in an immersive environment

Spin-Peierls transition in an anisotropic two-dimensional XY model

The two-dimensional Jordan-Wigner transformation is used to investigate the zero temperature spin-Peierls transition for an anisotropic two-dimensional XY model in adiabatic limit. The phase diagram between the dimerized (D) state and uniform (U) state is shown in the parameter space of dimensionless interchain coupling $h$ $(=J_{\perp}/J)$ and spin-lattice coupling $\eta$. It is found that the spin-lattice coupling $\eta$ must exceed some critical value $\eta_c$ in order to reach the D phase for any finite $h$. The dependence of $\eta_c$ on $h$ is given by $-1/\ln h$ for $h\to 0$ and the transition between U and D phase is of first-order for at least $h>10^{-3}$.Comment: 2 eps figures, considerable revisions were mad

Characteristics of damaged asphalt mixtures in tension and compression

This paper addresses the measurement and modelling of the damaged properties of asphalt mixtures including the fracture, healing and viscoplastic deformation of the asphalt mixtures in both tensile and compressive loading as being affected by their composition and conditioning with ageing and exposure to temperature and moisture. An energy-based mechanics is applied to obtain the material fundamental properties such as surface energies, bond energies, anisotropy, yield functions and plastic potential functions that are valid for actual asphalt mixtures, viscoelastic crack growth criteria under both tensile and compressive loading, a simple mechanics-based method of determining the fatigue endurance limit, and the measurement and prediction of healing in restoring the damage done by fracture. Healing is anti-fracture and cracking is the net result of the interplay of these two complimentary mechanisms. Because fracture in asphalt mixtures is not the growth of a single crack but the simultaneous growth of multiple cracks that start out as air voids, this fact leads to the use of the growth of damage density to characterise fracture in an asphalt mixture. It was discovered that the form of Paris’ law applies to the growth of damage density of asphalt mixtures in both tensile and compressive loadings. The importance of this fact lies in many developments from this discovery, e.g. compressive monotonic loading of cylindrical test samples permits a direct determination of the Paris’ Law coefficient and exponent. In all cases, measured material properties are presented as they vary with mixture composition and with conditioning such as moisture and ageing, both in the lab and in the field. The measurements of these properties are made simply, quickly and accurately by the use of mechanics so that an entire characterisation of the properties of an asphalt mixture in tension and compression can be completed in the space of one day. The net effect is to reduce the efforts expended in the lab and the systematic error due to the assumptions made by the existing models and simultaneously to increase the efficiency and cost-effectiveness of materials testing and raise the reliability of the design of mixtures, pavement structures and specifications and the prediction of the life cycles in as-built pavements

Possible Interpretations of DsJ+(2632)D_{sJ}^+(2632) If It Really Exists

We analyze various possible interpretations of the narrow state $D_{sJ}^+(2632)$ observed by SELEX Collaboration recently, which lies above threshold and has abnormal decay pattern. These interpretations include: (1) several versions of tetraquarks; (2) conventional $c\bar s$ meson such as the first radial excitation of $D_s(2112)$ with abnormally large SU(3) symmetry breaking; (3) conventional $c\bar s$ meson with abnormally large $\eta_1$ coupling; (4) heavy hybrid meson. We discuss the physical implications of each interpretation. For example, if the existence of $D_{sJ}^+(2632)$ is confirmed as the first radial excitation of $D_s(2112)$ by other experiments, it will be helpful to look for (1) its SU(3) flavor partners $D_{J}^{0,+}(2530)$; (2) its B-meson analogues $B_{J}^{0,+}(5840), B_{sJ}^+(5940)$; (3) S-wave two pion decay modes

Direct Measurements of the Branching Fractions for D0→K−e+νeD^0 \to K^-e^+\nu_e and D0→π−e+νeD^0 \to \pi^-e^+\nu_e and Determinations of the Form Factors f+K(0)f_{+}^{K}(0) and f+π(0)f^{\pi}_{+}(0)

The absolute branching fractions for the decays $D^0 \to K^-e ^+\nu_e$ and $D^0 \to \pi^-e^+\nu_e$ are determined using $7584\pm 198 \pm 341$ singly tagged $\bar D^0$ sample from the data collected around 3.773 GeV with the BES-II detector at the BEPC. In the system recoiling against the singly tagged $\bar D^0$ meson, $104.0\pm 10.9$ events for $D^0 \to K^-e ^+\nu_e$ and $9.0 \pm 3.6$ events for $D^0 \to \pi^-e^+\nu_e$ decays are observed. Those yield the absolute branching fractions to be $BF(D^0 \to K^-e^+\nu_e)=(3.82 \pm 0.40\pm 0.27)$ and $BF(D^0 \to \pi^-e^+\nu_e)=(0.33 \pm 0.13\pm 0.03)$. The vector form factors are determined to be $|f^K_+(0)| = 0.78 \pm 0.04 \pm 0.03$ and $|f^{\pi}_+(0)| = 0.73 \pm 0.14 \pm 0.06$. The ratio of the two form factors is measured to be $|f^{\pi}_+(0)/f^K_+(0)|= 0.93 \pm 0.19 \pm 0.07$.Comment: 6 pages, 5 figure