Showing papers by "Yang Gao published in 2009"

Measurement of the gamma gamma* --> pi0 transition form factor

Abstract: We study the reaction e+e- --> e+e-pi0 and measure the gamma gamma* --> pi0 transition form factor in the momentum transfer range from 4 to 40 GeV^2. The analysis is based on 442 fb^-1 of integrated luminosity collected at PEP-II with the BABAR detector at e+e- center-of-mass energies near 10.6 GeV.

Expected performance of the ATLAS experiment - detector, trigger and physics

Abstract: A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN.

LayerP2P: A New Data Scheduling Approach for Layered Streaming in Heterogeneous Networks

Abstract: Although layered streaming in heterogeneous peer-to-peer networks has drawn great interest in recent years, there's still a lack of systematical studies on its data scheduling issue. In this paper, we propose a new scheduling approach for layered video streaming, called LayerP2P. The key idea and main contributions of LayerP2P come in two-fold: 1) According to the characteristics caused by layered coding, we propose four objectives that should be achieved by data scheduling: high throughput, high layer delivery ratio, low useless packets ratio, and low subscription jitter; 2) We design a 3-stage scheduling mechanism to request absent blocks, where the min-cost flow model, probability decision mechanism and multi-window remedy mechanism are employed in Free Stage, Decision Stage and Remedy Stage, respectively. Each stage has different scheduling objective while collaborates with each other, to achieve the above four objectives. Experimental results indicate that our approach outperforms other schemes in simulation environment. Besides, LayerP2P is implemented in the PDEPS Project in China, which is expected to be the first practical layered streaming system for education in peer-to-peer networks.

Measurement of D0-D̄0 Mixing from a Time-Dependent Amplitude Analysis of D0→K+π-π0 Decays

Abstract: The authors present evidence of D{sup 0}-{bar D}{sup 0} mixing using a time-dependent amplitude analysis of the decay D{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0} in a data sample of 384 fb{sup -1} collected with the BABAR detector at the PEP-II e{sup +}e{sup -} collider at SLAC. Assuming CP conservation, they measure the mixing parameters x{prime}{sub K{pi}{pi}{sup 0}} = [2.61{sub -0.68}{sup +0.57}(stat.) {+-} 0.39(syst.)]%, y{prime}{sub K{pi}{pi}{sup 0}} = [-0.06{sub -0.64}{sup +0.55}(stat.) {+-} 0.34(syst.)]%. The confidence level for the data to be consistent with the no-mixing hypothesis is 0.1%, including systematic uncertainties. This result is inconsistent with the no-mixing hypothesis with a significance of 3.2 standard deviations. They find no evidence of CP violation in mixing.

LunarEX-a proposal to cosmic vision

Abstract: While the surface missions to the Moon of the 1970s achieved a great deal, scientifically much was also left unresolved. The recent plethora of lunar missions (flown or proposed) reflects a resurgence in interest in the Moon, not only in its own right, but also as a record of the early solar system including the formation of the Earth. Results from recent orbiter missions have shown evidence of ice or at least hydrogen within shadowed craters at the lunar poles.

3D virtual reality simulator for planetary rover operation and testing

Abstract: This paper describes a computer-simulated virtual reality environment for planetary rover operation and testing. The proposed 3D Virtual Rover Operation Simulator (VROS) consists of rover model, perception of the planetary surface, and rover-terrain contact model, which provides a simulation platform to test and validate different rover chassis design, navigation and locomotion algorithms, and to support rover operation. Lab-based experiments have been carried out and results can demonstrate various functions of VROS and its performance.

Triggering on Long-Lived Neutral Particles in the ATLAS Detector

Abstract: Neutral particles with long decay paths that decay to many-particle final states represent, from an experimental point of view, a challenge both for the trigger and for the reconstruction capabilities of the ATLAS apparatus. The Hidden Valley scenario serves as an excellent setting for the purpose of exploring the challenges to the trigger posed by long-lived particles.

The refined theory for a magnetoelastic body – II. Plane problems

Abstract: The problem of deducing two-dimensional theory from three-dimensional theory for a soft ferromagnetic elastic isotropic body is investigated. By using the general solution for the soft ferromagnetic elastic solids and Lur'e method, it is shown that the general deformation can be decomposed into two independent parts: the asymmetric deformations (plate problems) and the symmetric part (plane problems). A refined plate theory which takes into account the transverse shear deformation can now be explicitly established without employing assumptions. The exact equations and solutions for the plate with homogeneous boundary conditions are derived, and the equations can be decomposed into four governing differential equations. Moreover, the approximate equations and solutions for the plate under transverse loadings and magnetic field perturbations are derived directly from the refined plate theory. By omitting higher order terms and coupling effect, the refined plate theory can be degenerated into other well-known elastic and magnetoelastic theoretical models.

A refined theory of torsional deformation of a circular shaft

Abstract: The refined theory of torsional deformation of a circular shaft is proposed on the basis of the classical elasticity theory The refined theory provides the solutions of torsional deformation of a circular shaft without ad hoc assumptions Exact solutions, including a Saint-Venant’s solution part and a transcendental part, are obtained for a circular shaft with homogeneous boundary conditions, and the decomposed theorem is given and proved The approximate solutions are derived for a circular shaft under reverse direction surface loading by dropping terms of high order To illustrate the application of the theory developed, two examples are examined

Experimental Study of Dual Reciprocating Drilling Mechanism using Design of Experiment Approach

Abstract: Y. Gao et al. proved the feasibility of designing a woodwasp (Sirex Noctilio) inspired drill for Earth and extraterrestrial drilling and boring activities [1]. But before an optimised dual reciprocating drill design can be proposed, it is necessary to better understand the driving factors and the important parameters that influence this mechanism’s performance and, power and force requirements. Indeed the insect’s ovipositor is "optimised", through natural selection, for wood; but the dual reciprocating drill will bore into much different substrates. Here, the numerous parameters that could influence the studied mechanism’s performance are identified and the test bench to

Mixed boundary conditions for piezoelectric plates

Abstract: For plate bending and stretching problems in piezoelectric materials, the reciprocal theorem and the general solution of piezoelasticity are applied in a novel way to obtain the appropriate mixed boundary conditions accurate to all order. A decay analysis technique is used to establish necessary conditions that the prescribed data on the edge of the plate must satisfy in order that it should generate a decaying state within the plate. For the case of axisymmetric bending and stretching of a circular plate, these decaying state conditions are obtained explicitly for the first time when the mixed conditions are imposed on the plate edge. They are then used for the correct formulation of boundary conditions for the interior solution.

Theoretical studies of proton capture reactions in A ∼ 25 proton-rich nuclei

Abstract: The direct proton capture and resonance proton capture properties of stellar reactions 22Mg(p,γ)23Al and 26Si(p,γ)27P are studied by employing a mean-field potential obtained from the Skyrme-Hartree-Fock (SHF) model. Calculations with the SHF potential reproduce well the loosely-bound structure of the ground states as well as the widths of the resonant states in these nuclei. With the obtained potential we estimate the reaction rates of direct proton capture and resonance proton capture to nuclei 23Al and 27P. The effect of the 27P loosely-bound structure on the S factor of the direct proton capture is also discussed.

A refined theory of elastic thick plates for extensional deformation

Abstract: Based on elasticity theory, various two-dimensional (2D) equations and solutions for extensional deformation have been deduced systematically and directly from the three-dimensional (3D) theory of thick rectangular plates by using the Papkovich–Neuber solution and the Lur’e method without ad hoc assumptions. These equations and solutions can be used to construct a refined theory of thick plates for extensional deformation. It is shown that the displacements and stresses of the plate can be represented by the displacements and transverse normal strain of the midplane. In the case of homogeneous boundary conditions, the exact solutions for the plate are derived, and the exact equations consist of three governing differential equations: the biharmonic equation, the shear equation, and the transcendental equation. With the present theory a solution of these can satisfy all the fundamental equations of 3D elasticity. Moreover, the refined theory of thick plate for bending deformation constructed by Cheng is improved, and some physical or mathematical explanations and proof are provided to support our justification. It is important to note that the refined theory is consistent with the decomposition theorem by Gregory. In the case of nonhomogeneous boundary conditions, the approximate governing differential equations and solutions for the plate are accurate up to the second-order terms with respect to plate thickness. The correctness of the stress assumptions in the classic plane-stress problems is revised. In an example it is shown that the exact or accurate solutions may be obtained by applying the refined theory deduced herein.

Penetrometry in the solar system II

Abstract: We report on investigation and development of kinetic micro-penetrators onto airless solar system bodies. Our goal is to design a technically feasible penetrator of low mass (~2-5Kg) capable of surviving a high velocity impact and performing useful scientific measurements. We present a rational program of development beginning with generic studies and ground demonstration of impact survivability, through a technical demonstrator mission to high profile scientific missions. We aim to take advantage of existing experience from the UK defense sector, and current advances in high technology (e.g. MEMS, holey optical fibres). Key aspects discussed include the scientific case; a comparison of kinetic penetrators and landers as a platform for exploration; penetrator technology (orbiter support, attitude control, de-orbiting, impact survivability, power, communications, mass); scientific instruments (temperature, heat flow, seismic, chemical); and future mission opportunities.

The refined theory of deep rectangular beams for symmetrical deformation

Abstract: Based on elasticity theory, various one-dimensional equations for symmetrical deformation have been deduced systematically and directly from the two-dimensional theory of deep rectangular beams by using the Papkovich-Neuber solution and the Lur’e method without ad hoc assumptions, and they construct the refined theory of beams for symmetrical deformation. It is shown that the displacements and stresses of the beam can be represented by the transverse normal strain and displacement of the mid-plane. In the case of homogeneous boundary conditions, the exact solutions for the beam are derived, and the exact equations consist of two governing differential equations: the second-order equation and the transcendental equation. In the case of non-homogeneous boundary conditions, the approximate governing differential equations and solutions for the beam under normal loadings only and shear loadings only are derived directly from the refined beam theory, respectively, and the correctness of the stress assumptions in classic extension or compression problems is revised. Meanwhile, as an example, explicit expressions of analytical solutions are obtained for beams subjected to an exponentially distributed load along the length of beams.

A Bilateral Teleoperation System for Planetary Rovers

Abstract: In this paper, a bilateral teleoperation system (BTS) is proposed for planetary rover remote control and operation. This is a continuation of the work presented in on computer-simulated virtual environment, that can be used as a predictive display module in the BTS. In the proposed system, a haptic device is used by the human operators to control planetary rovers as driving a car. Dynamic model of the rover is used and a passive-based bilateral teleoperation scheme is adopted to achieve the stability of the close-loop control. Kinematic model of the rover is used to get the torque distribution algorithm and applied to calculate the corresponding torque for each wheel based on the desired linear speed and heading angle of the rover. Buffer unit is designed to address the issue of variable time-delay caused by the Internet. Lab-based experiments have been carried out using the BH2 rover. The test results demonstrate good performance of the proposed system.

The refined theory of piezoelectric thick plates

Abstract: Based on linear piezoelasticity theory, without requirement of any ad hoc assumptions concerning the deformation or the stress state, various two-dimensional equations have been deduced systematically and directly from the three-dimensional theory of thick rectangular plates by using the general solution of transversely isotropic piezoelasticity and the Lur'e method, and they construct the refined theory of plates. It is shown that the displacements and stresses of plates can be represented by the displacements and electric potential of the mid-plane. In the case of homogeneous boundary conditions, the refined plate theory is exact in the sense that a solution of the theory satisfies all the equations in the piezoelasticity theory and consists of three parts: the biharmonic part, the shear part, the transcendental part.

The refined theory of torsional deformation of transversely isotropic piezoelectric circular shaft

Abstract: The refined theory and the decomposed theorem of plates are converted into the refined theory of the torsional deformation of transversely isotropic piezoelectric circular shaft by using Bessel Function's Operator Method from equation of transversely isotropic piezoelasticity for torsional problem without ad hoc assumptions. Firstly, the problem of deducing one-dimensional theory from three-dimensional theory for transversely isotropic piezoelastic shaft is investigated. Expressions are obtained for all the displacements and stress components in term of one function on the neutral axis. Secondly, based on the refined theory of piezoelectric circular shaft, the exact equations for homogeneous boundary conditions are derived, which consist of two governing differential equations: 2-orders equation and the transcendental equation. Lastly, the approximate governing equations are accurate up to the high-order terms with respect to radius of shaft in the case of non-homogenous boundary conditions.