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Gravitational wave research using pulsar timing arrays

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National Science Review 2017年第5期4卷 707-717页

作者： George Hobbs shi dai Australia Telescope National Facility CSIRO

A pulsar timing array(PTA) refers to a program of regular, high-precision timing observations of a widely distributed array of millisecond pulsars. Here we review the status of the three primary PTA projects and the joint International Pulsar Timing Array project. We discuss current results related to ultra-low-frequency gravitational wave searches and highlight opportunities for the near future.

关键词： pulsars gravitational waves radio astronomy

RESEARCH ON STABILITY OF LIQUID FILM ON HOT SOLID SURFACE IMPINGED BY SMALL DROPLETS

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Journal of Hydrodynamics 2007年第3期19卷 264-271页

作者： GUO Jia-hong dai shi-qiang Shanghai Institute of Applied-Mathematics and Mechanics Shanghai University Shanghai 200072 China

A heat and mass transfer model was proposed for the thin liquid film on the hot solid surface cooled by the impinging small droplets, with consideration of the effect of the droplet impact, surface tension, thermocapillary, evaporation/condensation, and van der Waals attraction. The nondimensional equation for predicting the evolution of the interface of the thin liquid film was derived in the presented model with the relevant boundary conditions. The stability of the thin liquid film impacted by cool small droplets is discussed.

关键词： stability liquid film hot surface droplet

Dephosphorization stability of hot metal by double slag operation in basic oxygen furnace

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Journal of Iron and Steel Research International 2017年第9期24卷 908-915页

作者： Wei Wu shi-fan dai Yue Liu Metallurgical Technology Research Department Central Iron and Steel Research InstituteBeijing 100081China Hai Yi Tong Special Material Co. Ltd.Wuhan 430082HubeiChina

Double slag process was adopted to produce low-phosphorus steel from middle-phosphorus hot *** achieve a stable dephosphorization operation,conventional process was modified as follows：the blowing time was extended by approximately 1min by reducing the oxygen supply flow rate;calcium ferrite pellets were added to adjust the slag composition and viscosity;the dumping temperature was lowered by 30-50°C by the addition of calcium ferrite pellets during the double slag process to prevent phosphorus in the slag from returning to the molten steel;and the bottom-blown gas flow was increased during the blowing *** 40 heats of comparative experiments,the rate of dephosphorization reached 91% and ranged between 87% and 95%;the phosphorus,sulfur,manganese,and oxygen contents calculated according to the compositions of molten steel and slag as well as the temperature of molten steel at the end-point of the basic oxygen furnace process were similar to the equilibrium values for the reaction between the slag and the *** free calcium oxide and metallic iron were present in the final slag,and the surface of the slag mineral phase was smooth,clear,and well developed,which showed that the slag exhibited better melting effects than that produced using the conventional slag process.A steady phosphorus capacity in the slag and stable dephosphorization effects were achieved.

关键词： Medium-phosphorus hot metal Double slag operation Dephosphorization rate Phosphorus capacity Basic oxygen furnace

The plateau of gamma-ray burst:hint for the solidification of quark matter?

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Science China(Physics,Mechanics & Astronomy) 2011年第8期54卷 1541-1545页

作者： dai shi LI LiXin XU RenXin School of Physics and State Key Laboratory of Nuclear Physics and Technology Peking University Beijing 100871 China Kavli Institute for Astronomy and Astrophysics Peking University Beijing 100871 China

The origin of the shallow decay segment in γ-ray bursts' (GRB) early light curves remains a mystery, especially those cases with a long-lived plateau followed by an abrupt falloff. In this paper, we propose to understand the origins of the long-lived plateau by considering the solidification of newborn quark stars with latent heat released as energy injection to the GRB afterglow, and we suggest that an abrupt falloff would naturally appear after the plateau due to the energy injection cutoff. We estimated the total latent heat released during the phase transition of quark stars from liquid to solid states to be on the order of ～ 1051 ergs, which is comparable to the emission energy in the shallow decay segment. We also estimated the time scale of radiating the latent heat through thermal photon emission, and found that the time scale agrees with the observations. Based on our estimation, we analyzed the process of energy injection to GRB afterglow. We will show that the steady latent heat of quark star phase transition will continuously inject into the GRB afterglow in a form similar to that of a Poynting-flux-dominated outflow and naturally produce the shallow decay phase and the abrupt falloff after the plateau. We conclude that the latent heat of quark star phase transition is an important contribution to the shallow decay radiation in some GRB afterglows, and explains the long-lived plateau followed by an abrupt falloff, if pulsar-like stars are really (solid) quark stars.

关键词： γ-rays: bursts X-rays neutronstars elementaryparticles

Research on temperature field of non-uniform heat source model in surface grinding by cup wheel

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Advances in Manufacturing 2019年第3期7卷 326-342页

作者： shi-Jie dai Xiao-Qiang Li Hui-Bo Zhang State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of TechnologyTianjin 300130People's Republic of China School of Mechanical Engineering Hebei University of TechnologyTianjin 300130People's Republic of China Hebei Key Laboratory of Robot Perception and Human-Robot Interaction Tianjin 300130People's Republic of China

To address the problems of thermal damage to a workpiece surface caused by the instantaneous high temperature during grinding and the difficulty in monitoring temperature in real time,the temperature field in the case of composite surface grinding by a cup wheel is *** order to predict the grinding temperature,considering material removal and grinding force distribution,a nonuniform heat source model with different function distributions in the circumferential and radial directions in the cylindrical coordinate system is first proposed;then,the analytical model is deduced and the numerical model of the temperature field is established based on the heat source *** validation experiments for grinding temperature field are carried out using a high-definition infrared thermal imager and an artificial *** to the temperature field based on the uniform heat source model,the results based on the non-uniform heat source model are in better agreement with the actual temperature field,and the temperature prediction error is reduced from approximately 23% to 6%.Thus,the present study provides a more accurate theoretical basis for preventing bums in cup wheel surface grinding.

关键词： Non-uniform heat source Temperature filed Surface grinding Cup wheel

NUMERICAL SIMULATION FOR 2D SHALLOW WATER EQUATIONS BY USING GODUNOV-TYPE SCHEME WITH UNSTRUCTURED MESH

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Journal of Hydrodynamics 2006年第4期18卷 475-480页

作者： PAN Cun-hong dai shi-qiang CHEN Sen-mei Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200436 China Zhejiang Institute of Hydraulics and Estuary Hangzhou 310020 China Shanghai Institute of Applied Mathematics and Mechanics Shanghai University. Shanghai 200436 China Zhejiang Institute of Hydraulics and Estuary Hangzhou 310020. China

In order to establish a well-balanced scheme, 2D shallow water equations were transformed and solved by using the Finite Volume Method （FVM） with unstructured mesh. The numerical flux from the interface between cells was computed with an exact Riemann solver, and the improved dry Riemann solver was applied to deal with the wet/dry problems. The model was verified through computing some typical examples and the tidal bore on the Qiantang River. The results show that the scheme is robust and accurate, and could be applied extensively to engineering problems.

关键词： 2D shallow water equations Finite Volume Method (FVM) unstructured mesh Godunov-type scheme Riemann solver

Blinking adaptation for synchronizing a mobile agent network

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Journal of Zhejiang University-Science C(Computers and Electronics) 2011年第8期12卷 658-666页

作者： Huan shi Hua-ping dai You-xian SUN State Key Laboratory of Industrial Control Technology Zhejiang University Hangzhou 310027 China

We investigate the issue of synchronizing a blinking coupling mobile agent network through a blinking adaptation strategy,where each agent with blinking wave emission behavior not only adjusts its blinking period according to the local property of its neighbors,but also coordinates its blinking phase with those of neighboring *** leading the agents to blink orderly with a blinking period commensurate with the characteristic time of the dynamical oscillator,the presented blinking adaptation strategy works effectively in guaranteeing the synchronous motion of the considered network when the power density is *** addition,the influence of the controlling parameter and moving velocity on network evolution is studied by assessing the convergence time.

关键词： Mobile agents Blinking adaptation Coupled-oscillator networks Synchronization

CONJUGATE FLOWS OVER A STEP IN A THREE-LAYER FLUID

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Journal of Hydrodynamics 2002年第4期14卷 15-23页

作者： Wei, Gang Le, Ja-Chun dai, shi-Qiang Inst. of Appl. Math. and Mech. Shanghai Univ. Shanghai 200072 China Sch. of Sci. P.L.A Univ. of Sci. and Eng. Nanjing 211101 China

The conjugate flows over a step with the height h_0, which might be positive or negative, was studied in a three-layer fluid and the coupled nonlinear equations were derived, with which the effects of varying height h_0 on the existence and evolution of conjugate flows were examined. It is concluded that the conjugate flow is sharply sensitive to the thickness of fluid layers and its characteristics alters remarkably due to the existence of the step. As the flow climbs up a step (h_0>0), the conjugate flow with a convex lower interface and a concave upper interface is allowed to appear, while the flow with the concave lower interface or the simultaneous concave interfaces will be depressed. As the flow goes down a step (i.e., h_0<0), on most occasions only one kind of conjugate flow could exist, which prossesses the form with the simultaneous convex interfaces and will disappear rapidly with the increase of the step depth.

关键词： conjugate flow flat solitary wave stratified flow step topography three-layer fluid

Initial value problem for a class of fourth-order nonlinear wave equations

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Applied Mathematics and Mechanics(English Edition) 2009年第3期30卷 391-401页

作者：陈国旺侯长顺 shi-qiang dai Department of Mathematics Zhengzhou University Zhengzhou 450052 P. R College of Mathematics and Physics Henan University of Technology Zhengzhou 450052 P. R. China 不详

In this paper, existence and uniqueness of the generalized global solution and the classical global solution to the initial value problem for a class of fourth-order nonlinear wave equations are studied in the fractional order Sobolev space using the contraction mapping principle and the extension theorem. The sufficient conditions for the blow up of the solution to the initial value problem are given.

关键词： fourth-order nonlinear wave equation initial value problem global solution blow up of solution