电磁量计随爆轰波运动惯性性质的二维数值模拟

 利用二维非线性有限元动力分析程序，对金属电磁测速量计在爆轰波质速测量中随爆轰波运动的惯性性质进行了二维数值模拟。  

Stabilization and Consistency for Subtracted and Unsubtracted QCD Sum Rules for 0^＋＋ Scalar Glueball

Based on a semi-classical expansion for quantum chromodynamics in the instanton liquid background, the correlation function of the 0^＋＋ scalar glueball current is calculated. Besides the pure classical and quantum contributions, the contributions arising from the interactions between the classical instanton fields and quantum gluon ones come into play. It turns out that the latter contributions have a great role not only in making the stabilization of the subtracted and unsubtracted Laplace-transformed QCD sum rules for 0^＋＋ scalar glueball, but also in bring back the consistency between the two related sum rules, or equivalently between the QCD asymptotic expression and low energy theorem. The result for the scalar glueball mass is predicted to be mG= 1.35 GeV.  

圆头钢弹对PBX-9404炸药撞击起爆的数值模拟

 在二维有限元动力分析程序DYNA2D中加入了两种反应速率模型，对圆头钢弹撞击PBX-940 4炸药的冲击起爆行为进行了数值模拟研究。  

Event generators for η/η' rare decays into π+π-l+l- and e+e-μ+μ-

Study of the rare and forbidden decays of η/η' offers a sensitive probe to test fundamental symmetries of quantum chromodynamics and search for new physics beyond the Standard Model. To study the rare decays of η/η' to π⁺π^-e⁺e^-, π⁺π^-μ⁺μ^- and e⁺e^-μ⁺μ^- at the BESⅢ detector, we developed several event generators based on the vector meson dominant model with finite-width corrections and the pseudoscalar mesons mixing theory. The various distributions from event generators are in good agreement with the theoretical predictions, which indicates that the event generators work very well after implemention in the BESⅢ Monte Carlo simulation package. In the BESⅢ physics analysis, the performance of the event generators will be improved in accordance with the distributions of different variables of η/η' from data and the improvement on the theoretical calculations.  

Proximity effects in topological insulator heterostructures

Topological insulators （Tls） are bulk insulators that possess robust helical conducting states along their interfaces with conventional insulators. A tremendous research effort has recently been devoted to TI-based heterostructures, in which con- ventional proximity effects give rise to a series of exotic physical phenomena. This paper reviews our recent studies on the potential existence of topological proximity effects at the interface between a topological insulator and a normal insu- lator or other topologically trivial systems. Using first-principles approaches, we have realized the tunability of the vertical location of the topological helical state via intriguing dual-proximity effects. To further elucidate the control parameters of this effect, we have used the graphene-based heterostructures as prototypical systems to reveal a more complete phase diagram. On the application side of the topological helical states, we have presented a catalysis example, where the topo- logical helical state plays an essential role in facilitating surface reactions by serving as an effective electron bath, These discoveries lay the foundation for accurate manipulation of the real space properties of the topological helical state in TI- based heterostructures and pave the way for realization of the salient functionality of topological insulators in future device applications.  

PBX-9502炸药爆轰反应速率模型研究

 利用高能炸药爆轰反应的拉格朗日分析方法，得到了一个形式简单的PBX-9502炸药的爆轰反应速率方程。运用该速率方程，计算了PBX-9502炸药爆轰波反应区的纵向结构，并与三项式点火增长模型的计算结果及实验结果进行比较。结果表明：该爆轰反应速率方程能很好地模拟PBX-9502炸药爆轰波反应区的纵向结构。  

Surface tension effects on the behaviour of a rising bubble driven by buoyancy force

In the inviscid and incompressible fluid flow regime, surface tension effects on the behaviour of an initially spherical buoyancy-driven bubble rising in an infinite and initially stationary liquid are investigated numerically by a volume of fluid (VOF) method. The ratio of the gas density to the liquid density is 0.001, which is close to the case of an air bubble rising in water. It is found by numerical experiment that there exist four critical Weber numbers We1, We2, We3 and We4, which distinguish five different kinds of bubble behaviours. It is also found that when 1 ≤ We < We2, the bubble will finally reach a steady shape, and in this case after it rises acceleratedly for a moment, it will rise with an almost constant speed, and the lower the Weber number is, the higher the speed is. When We > We2, the bubble will not reach a steady shape, and in this case it will not rise with a constant speed. The mechanism of the above phenomena has been analysed theoretically and numerically.  

Numerical investigation of the deformation mechanism of a bubble or a drop rising or falling in another fluid

A numerical method for simulating the motion and deformation of an axisymmetric bubble or drop rising or falling in another infinite and initially stationary fluid is developed based on the volume of fluid （VOF） method in the frame of two incompressible and immiscible viscous fluids under the action of gravity, taking into consideration of surface tension effects. A comparison of the numerical results by this method with those by other works indicates the validity of the method. In the frame of inviseid and incompressible fluids without taking into consideration of surface tension effects, the mechanisms of the generation of the liquid jet and the transition from spherical shape to toroidal shape during the bubble or drop deformation, the increase of the ring diameter of the toroidal bubble or drop and the decrease of its cross-section area during its motion, and the effects of the density ratio of the two fluids on the deformation of the bubble or drop are analysed both theoretically and numerically.  

Tribological properties of diamond-like carbon films deposited bv pulsed laser arc deposition

A novel method, pulsed laser arc deposition combining the advantages of pulsed laser deposition and cathode vacuum arc techniques, was used to deposit the diamond-like carbon （DLC） nanofilms with different thicknesses. Spectroscopic ellipsometer, Auger electron spectroscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy, scanning electron microscopy and multi-functional friction and wear tester were employed to investigate the physical and tribological properties of the deposited films. The results show that the deposited films are amorphous and the sp2, sp3 and C-O bonds at the top surface of the films are identified. The Raman peak intensity and surface roughness increase with increasing film thickness. Friction coefficients are about 0.1, 0.15, 0.18, when the film thicknesses are in the range of 17-21 nm, 30-57 nm, 67-123 nm, respectively. This is attributed to the united effects of substrate and surface roughness. The wear mechanism of DLC films is mainly abrasive wear when film thickness is in the range of 17-41 nm, while it transforms to abrasive and adhesive wear, when the film thickness lies between 72 and 123 nm.  

Finite-Width Correction to Form Factors of γγ^＊→ π^0 Transition

Instead of the usual zero-width approximation for one resonance, we use the finite-width approximation for the two low resonances, i.e. the ρ- ω mesons, to investigate the light-cone local QCD sum rules for the form factor of the transition γγ^＊→ π^0 ,According to the method of the analytic continuation by duality, the weight function, the polynomial of a low order N, is added to the dispersion integral to annihilate the integrand in the region where both resonance saturation and the QCD asymptotic expression are least reliable. The resultant form factor in the cases for the zero- and finite-widths are almost the same, both agree well with the experimental measurements. A comparison with the result from the Laplacian transformed light-cone sum rules and a brief discussion are given.