A comprehensive experimental and improved kinetic modeling study on the pyrolysis and oxidation of propyne

To improve our understanding of the combustion characteristics of propyne, new experimental data for ignition delay times (IDTs), pyrolysis speciation profiles and flame speed measurements are presented in this study. IDTs for propyne ignition were obtained at equivalence ratios of 0.5, 1.0, and 2.0 in ‘air’ at pressures of 10 and 30 bar, over a wide range of temperatures (690–1460 K) using a rapid compression machine and a high-pressure shock tube. Moreover, experiments were performed in a single-pulse shock tube to study propyne pyrolysis at 2 bar pressure and in the temperature range 1000–1600 K. In addition, laminar flame speeds of propyne were studied at an unburned gas temperature of 373 K and at 1 and 2 bar for a range of equivalence ratios. A detailed chemical kinetic model is provided to describe the pyrolytic and combustion characteristics of propyne across this wide-ranging set of experimental data. This new mechanism shows significant improvements in the predictions for the IDTs, fuel pyrolysis and flame speeds for propyne compared to AramcoMech3.0. The improvement in fuel reactivity predictions in the new mechanism is due to the inclusion of the propyne + H?₂ reaction system along with ?H radical addition to the triple bonds of propyne and subsequent reactions.     

气体团簇离子束两步能量修形法的平坦化效应

本文提出采用气体团簇离子束的两步能量修形法来改善4H-SiC(1000)晶片表面形貌.先用15 keV的高能Ar团簇离子进行整体修形,再用5 keV的低能团簇离子优化表面.结果表明,在相同的团簇离子剂量下,与单一15 keV的高能团簇处理相比,两步法修形后的表面具有更低的均方根粗糙度,两者分别为1.05 nm和0.78 nm.本文还以原子级平坦表面为研究对象,揭示了载能团簇引起的半球形离子损伤(弧坑)与团簇能量的关系,及两步能量修形法在弧坑修复中的优势.在原子力显微镜表征的基础上,引入了二维功率谱密度函数,以直观全面地给出材料的表面形貌特征及其随波长(频率)的分布.结果表明,经任何能量的团簇离子轰击的表面,在0.05—0.20μm波长范围内,团簇轰击都能有效地降低粗糙度,而在0.02—0.05μm范围内,则出现了粗化效应,这是由于形成了半球形离子损伤,但第二步更低能量的团簇离子处理可以削弱这种粗化效应.     

Finite-element calculation of the influence of interdiffusion on eigenstates in a GaAs/Al x Ga1-x As single-quantum-well structure

The influence of interdiffusion on eigenstates in an interdiffusion-induced GaAs/Al_xGa_1-xAs single-quantum-well structure is analysed numerically by the finite element method. In this approach, the confinement potential profile of the interdiffused quantum well structure is nonlinear and is modelled by an error function and, in particular, the nature of the effective mass of an electron is considered. The results show that the number of eigenstates and energy levels varies with the extent of the interdiffusion. Numerical results for the quasi-bound states in the quantum well structure with an applied electric field are also presented.     

High spatial resolution in vivo 2D (1)H magnetic resonance spectroscopic imaging of human muscles with a band-selective technique.

This report demonstrates a 2D (1)H magnetic resonance spectroscopic imaging (MRSI) technique that can address some technical difficulties often encountered in MRS studies of human muscles. A preliminary application of this whole-slice technique in human skeletal muscles demonstrates clearly noticeable differences in (1)H metabolite spectra between different human muscles. This observation illustrates the importance of multi-voxel and high spatial resolution in a heterogeneous environment. This technique is robust, can be easily implemented on a commercial MR scanner, and should prove useful for investigators in both basic and clinical (1)H MRS studies.     

The Hirota bilinear method for the coupled Burgers equation and the high-order Boussinesq–Burgers equation

This paper studies the coupled Burgers equation and the high-order Boussinesq–Burgers equation. The Hirota bilinear method is applied to show that the two equations are completely integrable. Multiple-kink (soliton) solutions and multiple-singular-kink (soliton) solutions are derived for the two equations.