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We study the decays of J / ψ and ψ ( 3686 ) to the final states Σ ( 1385 ) 0 Σ ¯ ( 1385 ) 0 and Ξ 0 Ξ ¯ 0 based on a single baryon tag method using data samples of ( 1310.6 ± 7.0 ) × 10 6 J / ψ and ( 447.9 ± 2.9 ) × 10 6 ψ ( 3686 ) events collected with the BESIII detector at the BEPCII collider. The decays to Σ ( 1385 ) 0 Σ ¯ ( 1385 ) 0 are observed for the first time. The measured branching fractions of J / ψ and ψ ( 3686 ) to Ξ 0 Ξ ¯ 0 are in good agreement with, and much more precise than, the previously published results. The angular parameters for these decays are also measured for the first time. The measured angular decay parameter for J / ψ → Σ ( 1385 ) 0 Σ ¯ ( 1385 ) 0 , α = − 0.64 ± 0.03 ± 0.10 , is found to be negative, different to the other decay processes in this measurement. In addition, the “12% rule” and isospin symmetry in the decays of J / ψ and ψ ( 3686 ) to Ξ Ξ ¯ and Σ ( 1385 ) Σ ¯ ( 1385 ) are tested.

The deformation and breakup process of a liquid drop in supersonic flow is numerically studied with a coupled Level Set and Volume of Fluid method as the interface tracking approach. The Navier–Stokes equations in the liquid phase are solved by an incompressible flow solver using a finite volume method, and the governing equations in the gas phase are solved by a compressible flow solver using a finite difference method. Proper boundary conditions are specified at the interface for both liquid and gas flow solvers in order to correctly capture the interaction between the liquid and gas flows. It is demonstrated that the simulation cost can be significantly reduced by reducing liquid/gas density ratio while keeping the same Weber number and Ohnesorge number. Drop breakup at different Weber numbers is simulated. Bag breakup, bag stamen breakup, and multimode breakup modes are reproduced by the present two-phase flow solver. The physical mechanism for drop breakup in supersonic flow is investigated, and Rayleigh–Taylor instability is found to determine the breakup morphology for the studied Weber number range.

The paper proposed a two-phase flow Large Eddy Simulation (LES) algorithm for atomization in supersonic gas flow. A coupled Level Set and Volume of Fluid (VOF) interface tracking method is used. The supersonic gas flow is solved using a compressible flow solver, and the liquid phase is solved using an incompressible flow solver. Appropriate boundary conditions are specified on the interface for both solvers to correctly capture the interaction between the gas and liquid. The water jet primary breakup in a supersonic air crossflow is well predicted, with the shock waves ahead of the liquid column and drops/ligaments properly captured. Two kinds of vortices respectively relating to surface breakup and column breakup are observed. Surface waves on the windward side of the liquid jet are numerically reproduced, and the wavelength is well correlated to an effective Weber number which is determined by the gas flow behind the shock. As gas flow goes across the strong shock wave ahead of liquid column, the disintegrating aerodynamic force is weakened. Rayleigh–Taylor instability is found to be responsible for the development of surface waves which causes column breakup. It is demonstrated that LES can produce almost the same breakup morphology as an under-resolved DNS.

This paper extends the double cantilever beam (DCB) model to functionally graded materials (FGMs) based on two-dimensional theory of elasticity. A theoretical approach is proposed to determine strain energy release rate of a crack in a layered FGM with exponential gradient perpendicular to the crack plane. Elasticity solutions of a functionally graded cantilever subjected to a concentrated force and a bending moment are derived for thickness-wise varying Young’s modulus. Using the derived elasticity solutions, the energy release rate and stress intensity factor for an edge crack and a central crack parallel to the surface are obtained. Numerical results are given to show the influence of gradient index on fracture parameters.

The spark ignition process in the scramjet combustor fueled by hydrogen equipped with multi-cavities at Mach 4 flight condition was observed by high speed photography and Schlieren system, at the inflow conditions of Ma = 1.92 with stagnation state T 0 = 846 K, P 0 = 0.7 MPa. The spark kernel, the flame spreading process and shock structures in the combustor with different ignition and injection setups were well captured. The experiments revealed that flame kernel occurs near the igniter, and grows to form flame in the cavity. The initial flame spreads along the cavity shear layer and ignites the fuel distributed downstream very quickly. Along with the pressure downstream climbing up, the pre-combustion shock trains and the flame region move against the stream and the whole fuel jet is ignited and stabilized in a ‘jet surrounding mode’. The expand angle of the upper wall and the disturbance caused by the upstream cavity have an obvious effect on the fuel diffusion and convection procedure into the cavity and further affect the ignition. Hydrogen fuel injected into the cavity directly could improve the ignition performance greatly at the experimental status.

Four hundred fifty 52-wk-old Lang-shan breeding hens (dual-purpose type, an indigenous poultry breed of China) were randomly divided into 9 treatments with 5 replicates each treatment. They were fed corn-soybean diets with 0, 0.30, and 0.60 mg of Se/kg from Se yeast and 3.2, 4.0, and 5.4 g of dl-Met/kg, respectively. After incubation, 250 chickens each treatment were randomly divided into 5 replicates and fed the same diet. At 21 d old, 10 male chicks in each treatment were slaughtered. There results were as follows. (1) The Se content significantly increased with the increase of Se yeast supplementation (P < 0.01). (2) The carbonyl content of the myofibrillar protein significantly decreased with the increase of Met supplementation (P < 0.01) and the carbonyl content of the 0 mg of Se/kg treatment was higher than the 0.3 mg of Se/kg treatment (P < 0.01). (3) Selenium supplementation at 0.30 and 0.60 mg/kg significantly decreased malondialdehyde content compared with that of 0 mg of Se/kg (P < 0.01) and 4.0 and 5.4 g of Met/kg supplementation significantly decreased malondialdehyde content compared with that of 3.2 g of Met/kg (P < 0.01). (4) Supplementation of Met at 5.4 g/kg significantly increased International Commission on Illumination a* value compared with 3.2 and 4.0 g of Met/kg (P < 0.01). Supplementation of Se at 0.6 mg/kg significantly increased a* value compared 0 and 0.3 mg of Se/kg (P < 0.01) and 0 mg of Se/kg significantly increased b* value compared with 0.30 and 0.60 mg of Se/kg (P < 0.01). (5) Selenium supplemented at 0.30 and 0.60 mg/kg decreased drip loss compared with 0 mg of Se/kg and 4.0 and 5.4 g of Met/kg decreased drip loss compared with 3.2 g of Met/kg, respectively. The conclusion was drawn that Met and Se yeast supplementation of the maternal diets could improve color, water-holding capacity, and oxidative stability of male offspring meat to an extent.

The thermo-mechanical aspects of adiabatic shear band (ASB) formation are studied for two commercial alloys: Mg AM50 and Ti6Al4V. Tests are carried out on shear compression specimens (SCS). The evolution of the temperature in the deforming gauge section is monitored in real time, using an array of high speed infrared detectors synchronized with a Kolsky apparatus (split Hopkinson pressure bar). The evolution of the gage temperature is found to comprise 3 basic stages, in agreement with Marchand and Duffy’s simultaneous observations of mechanical data and gauge deformation patterns (1988). The onset and full formation stages of ASB are identified by combining the collected thermal and mechanical data. Full development of the ASB is identified as the point at which the measured and calculated temperature curves intersect and diverge thereon. At that stage, the homogeneous strain assumption used in calculating the maximum temperature rise is no longer valid.

Knowing that Fe is sensitive to swift heavy ion irradiations whereas Au and Al are not, the behavior of nanometric metallic multilayer systems, like [Fe(3 nm)/Au(x)]y and [Fe(3 nm)/Al(x)]y with x ranging between 1 and 10 nm, were studied within the inelastic thermal spike model. In addition to the usual cylindrical geometry of energy dissipation perpendicular to the ion projectile direction, the heat transport along the ion path was implemented in the electronic and atomic sub-systems. The simulations were performed using three different values of linear energy transfer corresponding to 3 MeV/u of 208Pb, 132Xe and 84Kr ions. For the Fe/Au system, evidence of appearance of a molten phase was found in the entire Au layer, provided the Au thickness is less than 7 nm and 3 nm for Pb and Xe ions, respectively. For the Fe/Al(x) system irradiated with Pb ions, the Al layers with a thickness less than 4 nm melt along the entire ion track. Surprisingly, the Fe layer does not melt if the Al thickness is larger than 2 nm, although the deposited energy surpasses the electronic stopping power threshold of track formation in Fe. For Kr ions melting does not occur in any of the multilayer systems.

We report the investigation of temperature and excitation power dependence in photoluminescence spectroscopy measured in Mg-doped GaN epitaxial layers grown on sapphire by metalorganic chemical vapor deposition. The objective is to examine the effects of rapid-thermal annealing on Mg-related emissions. It is observed that the peak position of the 2.7–2.8 eV emission line is a function of the device temperature and annealing conditions. The phenomenon is attributed to Coulomb-potential fluctuations in the conduction and valence band edge and impurity levels due to the Mg-related complex dissociation. The blue shift of the 2.7–2.8 eV emission line with increasing excitation power provides clear evidence that a donor–acceptor recombination process underlies the observed emission spectrum. In addition, quenching of minor peaks at 3.2 and 3.3 eV are observed and their possible origin is discussed.

The residual stresses in a 20vol% SiCp/6061Al composite which had been aged and low-temperature-treated were determined by X-ray diffraction and finite-element calculation. The results of experiment and calculation indicate that the residual stress state can be adjusted by low-temperature treatment and subsequent reheating to ambient temperature. By a proper choice of temperature in the low-temperature treatment, the average residual stresses can be reduced to zero. (C) 1997 Elsevier Science Limited.

SiC coatings prepared by chemical vapor deposition and from polycarbosilane (PCS) solution; also, SiO2 and Al2O3 coatings by Sol-Gel method were investigated in detail, to improve the oxidation resistance of carbon fibers as important reinforcement in advanced composites. A beta-SiC coating was obtained on carbon fibers by pyrolysis of CH3SiCl3 and H-2 at 1373-1573 K. The coating thickness could be controlled according to the requirements in practice. A uniform and fine SiC coating was also obtained by immersion and pyrolysis of PCS solutions with PCS contents of 5-15 wt%, and was composed of a mixture of SiC, SiO2, and free carbon after pyrolysis in argon. Fine and dense SiO2 and Al2O3 coatings could be obtained from silica and alumina sols, respectively, under exact control of process parameters. All coatings had good effects on the oxidation resistance of carbon fibers in the sequential order of CVD SiC, PCS-SiC, SiO2, and Al2O3. A composite coating of CVD SiC and a mixing coating of SiO2 and Al2O3 was suggested to decrease defects like pores and microcracks in individual coatings to obtain the best oxidation protection for carbon fibers.

One way of overcoming the shortcomings of carbon fibres is to coat them with SiC. In this work, carbon fibres were coated with a polycarbosilane solution and then pyrolysed continuously at high temperature to obtain the SiC coating. Effects of the coating process on the structure of the coating and the properties of the coated fibres were studied in detail. The results show that the solution coating process is a simple and applicable technique. The uniform and continuous coating improved the oxidation resistance and strength of the carbon fibres, as well as their wettability with aluminium. The coating also controlled the harmful reaction at the interface of aluminium matrix composites and improved composite strength.

Investigations have indicated that at low temperature aluminum- lithium alloys display improved toughness and an improved strength-toughness relationship. The yield strength, ultimate tensile strength, elongation and the fracture toughness increase with decreasing temperatures. Several mechanisms have been proposed to explain this most striking feature. Webster claimed that low melting point impurities, such as sodium and potassium, are responsible for the improvement of mechanical properties in Al-Li alloys at low temperatures. However, Venkateswara Rao et al. indicated that the increased delamination at low temperatures can increase the degree of in-plane crack deflection, resulting in toughening of the alloys. On the basis of their own results, Xu and coworker pointed out that the improvement of tensile and fatigue properties at liquid nitrogen temperatures is also presumably attributable to the delamination. Therefore, the mechanisms responsible for the variation in mechanical properties with temperature are not currently well-understood. In order to elucidate the real situation, single crystals of a binary aluminum-lithium alloy were adopted in the present study. This paper is devoted to the description of the behavior of the load-displacement curves and the associated slip traces on the sample surfaces.

We have observed many stimulated emission lines near 910 nm, 1030 nm and 690 nm, when diatomic sodium molecules are pumped by a pulsed laser at 354.7 nm. A mechanism of cascade emission, which may be responsible for laser action in the 910 nm and 690 nm region, is proposed and discussed.