Influence of g-jitter on a laminar boundary layer type diffusion flame

A numerical study was conducted to analyze the effect of g-jitter on micro-gravity flames. A boundary layer laminar diffusion flame was used as a test case. This configuration is commonly used to study flame spread in microgravity, thus it is essential to understand the role of g-jitter in these flames. Furthermore, the role of buoyancy increases with the stream-wise coordinate permitting a systematic study of the impact of acceleration perturbations with a reduced number of experimental results. The evolution of experimental stand-off distances defined during parabolic flights compared well, in a qualitative manner, with numerical simulations, validating the aerodynamic aspects of the model. A systematic study using a sinusoidal function showed that perturbations characterized by high frequencies (>1 Hz) do not affect the flame stand-off distance. This is independent of the amplitude within the range of typical perturbations observed during parabolic flights. Perturbations occurring at lower frequencies significantly affected the flame geometry. Averaging over time through periods much longer than the perturbation cycle did not eventually reveal departure from purely zero-gravity flames. Fuel and oxidizer velocities have opposite effects on the sensitivity of the flames to gravity fluctuations. An increase in oxidizer velocity results in a sensitivity decrease. The influence of the multiple parameters of the problem can qualitatively be combined within a previously reported non-dimensional group. Nevertheless, it cannot account for the influence of frequency.     

Simulation and experimental study of the influence of a front face layer on the response of ultrasonic transmitters

Using a theoretical model, we simulate the ultrasonic pressure generated by a piezoelectric transmitter whose active element has its front face perfectly connected to a layer with parallel faces. This simulation takes into consideration the characteristic parameters of the piezoelectric ceramic, the layer and the propagation medium.Verification of the validity of the model is carried out by assessing, qualitatively and quantitatively, theoretical and experimental responses obtained with different values of layer thickness. Having correctly verified the model solely by simulation, we examine the influence of the nature of the layer on the transmitter response and give an energetics interpretation of the results. We conclude that by using a simple theoretical model, we may forecast the experimental response of a transducer which has a front face layer.     

纸质胶带胶层厚度在线测量

在纸质胶带生产过程中 ,胶层厚度及均匀性是很重要的技术指标 ,因此需要对胶层厚度进行在线测量。介绍了一种红外纸质胶带胶层厚度测量仪。它是依据胶质对一定波长的红外光具有特征吸收的原理 ,采用了能量比参考平衡技术 ,使仪器性能稳定、可靠     

激光熔覆层开裂行为的影响因素及控制方法

激光熔覆层开裂是影响覆层质量最主要的因素,特别是厚覆层。选用５ｋＷ 横流ＣＯ２ 激光器对各种不同材料和零件进行厚覆层激光熔覆,实验、检测和使用的效果说明：激光熔覆层开裂主要与激光系统参数、工艺处理条件、覆层材料、基体状况等四个方面有关。分析了熔覆层的开裂行为,并介绍了几种控制方法。     

The influence of fractality on the time evolution of the diffusion process

In the literature, the deviations from standard behaviors of the solutions of the kinetic equation and the analogous diffusion equation are put forward by investigations which are carried out in the frame of fractional mathematics and nonextensive physics. On the other hand, the physical origins of the order of derivative namely α in fractional mathematics and the entropy index q in nonextensive physics are a topic of interest in scientific media. In this study, the solutions of the diffusion equation which have been obtained in the framework of fractional mathematics and nonextensive physics are revised. The diffusion equation is solved by the cumulative diminuation/growth method which has been developed by two of the present authors and physical nature of the parameters α and q are enlightened in connection with fractality of space and the memory effect. It has been emphasized that the mathematical basis of deviations from standard behavior in the distribution functions could be established by fractional mathematics where as the physical mechanism could be revealed using the cumulative diminuation/growth method.     

The influence of changes in the framework on the diffusion in zeolites. Molecular dynamics simulations

Some less known methods are described for the analysis of trajectories of guest molecules in porous solids. Such trajectories can be calculated by Molecular Dynamics (MD) computer simulations in order to analyze the interrelations between the structure and the particle behaviour including collective phenomena. Some results obtained with these methods for diffusing methane in zeolites of type LTA are presented. An analytical potential model for LTA type zeolites is given that make extremely long runs or simulations of large lattice regions for systems with rigid lattice possible. Such runs are necessary e.g. to examine questions as the influence of extented lattice defects or the fractal behaviour of the partical trajectories.     

The influence of SiCp oxidized on the interface layer and thermal conductivity of SiCp/Al composites

In this work, oxidation of silicon carbide particles (SiCp) at elevated temperature and its influence on the interface layer and thermal conductivity of SiCp/ZL101 composites prepared using pressure infiltration process were investigated respectively. It is found that initial temperature for the oxidation of SiCp is about 850?°C, and that the oxidation increment of SiCp and the thickness of SiO₂ layer increase with the increase in pre-oxidation temperature and time, when the oxidized temperature exceeds 1100?°C, or the duration time exceeds 2?h at 1100?°C, a small amount of ablation will take place on the SiCp, as well as the oxidized layer has some loss. The formation of SiO₂ layer can provide certain interface reactions with interface layers (3.1–6.36?μm), and the higher the thickness of SiO₂ layer, the thicker the interface layer in SiCp/Al composites. However, the thickness of SiO₂ layer is more than 5.9?μm, which is not benefit for the formation of interface layer. With the increase in the thickness of interface layer, thermal conductivity declines, but is not linear.     

The influence of impurity on the critical thickness of the CeO_2 buffer layer for coated conductors

The lattice parameters, band structure, density of state and elastic constant of RE-doped CeO2 (RE=Sm, Gd, Dy), the buffer material for coated HTS conductors, are calculated using the plane-wave method with pseudopotentials based on the density functional theory (DFT) of first-principle. The rule and mechanism of the effect of rare earth impurity on the critical thickness of the CeO2 buffer layer are investigated. It is found that, in the range of the calculation, the changes of the lattice volume V and ela...     

The influence of the ideal mixing entropy on concentration profiles and diffusion paths in ternary systems

The diffusion profiles and the reaction paths in ternary solid solutions are determined by both thermodynamics and kinetics. The matrix of the diffusion coefficient can be described as the product of the Hessian matrix for the thermodynamic influences and the Onsager matrix for kinetic influences.In this paper the interest is focused on the influence of the ideal part of the Hessian matrix, i.e. the ideal mixing entropy on interdiffusion. The ideal diffusion profiles are calculated by a computer simulation and they are compared with experimental results from the literature. These comparisons reveal that in most cases the qualitative shape of the diffusion profiles and of the reaction paths can be considered as caused by the ideal mixing entropy. Surprisingly, the shape of the diffusion profiles turns out to depend on the component that was chosen as the so-called solvent of the ternary mixture. This means that the ideal reaction paths do not show the triangular symmetry expected for an ideal ternary system. Especially, reaction paths between starting positions showing the same concentration of one of the three components do not run along straight lines.     

The influence of excluded volume and excess ion polarisability on the capacitance of the electric double layer

ABSTRACT

We apply a modified Poisson–Boltzmann theory which permits ions of different sizes and excess polarisabilities to the study of these properties’ effects on the differential capacitance of the electric double layer. For a planar electrode, we find an analytical expression for the differential capacitance, which is examined in the limits of low- and high-applied potential. In the low potential limit, a reduction of the solution relative permittivity caused by the ion polarisability causes the differential capacitance to decrease above a certain concentration, relative to the Gouy–Chapman–Stern theory. A similar effect is observed for the excluded volume, but only if the ions are of different sizes. In the high potential limit, the differential capacitance decreases inversely with the square root of the applied voltage. In a mixed electrolyte, asymmetries in both ion size and excess polarisability alter the surface adsorption of species: at high potentials, smaller ions displace larger ions and less polarisable ions displace more polarisable ions. The extent of the displacement agrees favourably with experimental data. A further consequence of this displacement is the appearance of a second peak in the differential capacitance, which is enhanced by excess ion polarisability.     

The effect of oxygen vacancy on the oxide ion mobility in LaAlO3-based oxides

The electrical property of (La_1−xSr_x)_1−z(Al_1−yMg_y)O_3−δ (LSAM; x≤0.3, y≤0.15 and z≤0.1) was measured using the DC four-probe method as a function of temperature (500–1000°C) and oxygen partial pressure (1–10⁻²² atm). Among LSAMs, (La_0.9Sr_0.1)AlO_3−δ showed the highest ionic conductivity, σ_i=1.3×10⁻² S cm⁻¹ at 900°C. A simultaneous substitution at A and B sites or A site deficiency is expected to create larger oxygen vacancy and higher ionic conductivity. However, it showed a negative effect. The effect of the vacancy increase did not effect monotonously the ionic conductivity. It was found that the concentration of oxygen vacancy, [V_O], influences not only the oxide ion conductivity, σ_i, but also the mobility, μ_v, of [V_O]. These properties exhibit a maximum at around [V_O]=0.05. With the increase in [V_O], the activation energy, E_a, of the ionic conduction dropped from 1.8 to ca. 1.0 eV at [V_O]=0.05 and became almost constant at [V_O]>0.05. The dependency of the pre-exponential term, μ⁰_v, and E_a on [V_O] was analyzed and their effect on μ_v and σ_i was discussed with respect to crystal structure and defect association. It was estimated that the crystal structure mainly governs these properties. The effect of defect association could not be ignored but is considered to be a complicated correlation.     

The effect of a nitrogen-rich surface layer on the sub-surface deuterium (hydrogen) concentration distribution in titanium

Deuterium and nitrogen depth profiles in Ti with modified surfaces have been measured with Auger electron spectroscopy, secondary ion mass spectroscopy, and D(³He,p)⁴He nuclear reaction analysis. Nitrogen-rich surfaces layers of varying thicknesses were created on Ti by exposure to N₂ gas at 650°C. Deuterium loading was performed by exposure to 1 Torr of D₂ gas at 500°C. The deuterium distribution was influenced by nitrogen in the near-surface regions of all samples. Specifically, deuterium solubility was suppressed in surface regions of high (greater than 1%) nitrogen concentration. The deuterium solubility also remained low within the first few microns, well beyond the region of high nitrogen concentration. This effect is attributed to internal elastic stresses imposed by the non-deuterium absorbing nitrogen-rich layer on the Ti. These stresses prohibit the volume expansion associated with deuterium absorption. We estimate stresses on the order of 3–4 GPa are required to suppress the deuterium solubility to the values observed. The deuterium absorption kinetics were observed to depend systematically on the thickness of the nitrogen-rich layer. This is consistent with limited solubility near the surface or a surface poisoning effect influencing the overall deuterium diffusion from the gas phase into the Ti bulk.     

鞘场加速机理中质子束的特性与其初始尺寸的关系

为了研究激光鞘场中质子层的尺寸对质子束特性的影响,本文应用中国工程物理研究院 激光聚变研究中心的二维Particle-In-Cell (2D-PIC)数值模拟程序Flips2D进行了相关数值模拟研究. 研究了质子束总能量随时间的变化,得出了加速持续过程与激光脉冲持续时间的关系; 研究了质子层的宽度对加速后质子束发散角和能谱的影响;研究了质子层的厚与加速后质子束 发散角和能谱的关系;得出了质子层的初始尺寸对加速后质子特性的影响规律.     

Effects of the annealing duration of the ZnO buffer layer on structural and optical properties of ZnO rods grown by a hydrothermal process

In this study, the effects of the annealing duration of a zinc oxide (ZnO) buffer layer on structural and optical properties of ZnO rods grown by a hydrothermal process are discussed. A ZnO buffer layer was deposited on p-type Si (1 1 1) substrates by the metal organic chemical vapor deposition (MOCVD) method. After that, ZnO rods were grown on the ZnO-buffer/Si (1 1 1) substrate by a hydrothermal process. In order to determine the optimum annealing duration of the buffer layer for the growth of ZnO rods, durations ranging from 0.5 to 30 min were tried. The morphology and crystal structure of the ZnO/ZnO-buffer/Si (1 1 1) were measured by field emission scanning electron microscopy (FE-SEM) and x-ray diffraction (XRD). The optical properties were investigated by photoluminescence (PL) measurement.     

DPVBi的厚度和发光位置不同对有机电致发光器件性能的影响

通过调整发光层DPVBi的厚度和在器件中的位置,在同一实验条件下设计了不同的器件结构,制备了有机电致发光器件,在实验中可看到DPVBi的厚度不同,器件的色度发生了改变,并且发现DPVBi在器件的不同位置,器件的发光特性也是不同的。通过实验可以得知处于器件不同位置的DPVBi,其发光机理是不同的,这是由于DPVBi和Alq3的最高未占有轨道(HOMO)能级相差不多,而它们的最低占有轨道(LUMO)能级相差0.4eV,这样DPVBi的存在有利于电子的注入,同时由于rubrene和DPVBi的HOMO相差0.5eV,这样空穴和电子就在rubrene和DPVBi的界面处形成激子复合而发光。也就是说,在rubrene之后的DPVBi对空穴有了阻挡作用,使器件中的空穴和电子达到平衡。通过改变DPVBi的厚度,制备了白光器件,这组白光器件,在7～17V变化范围内器件的色坐标从(0.35,0.37)到(0.33,0.35)变化不大,接近白光等能点(0.33,0.33),是色度比较好的器件。     

超声清洗过程环境压力对声空化效应的影响*

在不同深度条件下的水下构建物超声清洗中,声空化是重要的源动力之一。为探明水下环境压力对声空化的影响,本文基于数值计算的方法,通过对超声波作用下气泡动力学的研究,讨论了环境压力对空化泡溃灭时的气泡最大半径、释放能量以及溃灭功率等因素的影响。结果表明：空化泡最大半径与环境压力在一定范围内呈近似线性关系;随着环境压力增大,空化泡释放能量和溃灭功率均显著减小,且两者在变化趋势和变化幅度上几乎一致;当环境压力大于声压幅值时,空化泡的最大半径、内部压强、内部温度与释放能量均远低于空化发生在环境压力小于声压幅值时的情形。     

(Ni0.81Fe0.19)1-xCrx作为种子层对NiFe/FeMn交换偏置的影响

采用一种新的种子层材料:(Ni081Fe019)1-xCrx,通过改变种子层中Cr原子的含量,使得在其上生长的NiFeFeMn双层膜的织构和晶粒尺寸产生极大的差异,系统研究了NiFeFeMn双层膜中FeMn晶粒尺寸和织构对交换偏置的影响.实验结果表明,在FeMn的γ相(111)织构较好的前提下,交换偏置场的大小与织构的差异没有关系;FeMn的晶粒尺寸对交换偏置场有很大影响,较小的反铁磁层晶粒对交换偏置场有利,过大的反铁磁层晶粒不利于交换偏置场.将(Ni081Fe019)05Cr05与传统的种子层材料Ta进 关键词： 交换偏置 晶粒尺寸 织构 种子层     

The formation of a diamond layer on a carbide substrate during diamond interaction with Si,WC and Co

Abstract

A diamond layer was formed on a carbide substrate in an irregular temperature field at high pressures (HP). A gradient scheme of HP cell set-up has been developed, which provides for a simultaneous impregnation of opposite planes of a diamond layer by components that differ in melting temperature. The cell temperature field has been calculated and physico-mechanical properties of the obtained composite material have been studied.     

The unexpected formation of Au-Si by the resonance neutralization of Ar during the low energy bombardment of Au nanoparticles on c-Si

Nanoscale Au layers, with irregular porosities, have been formed by the low energy Ar⁺ bombardment of Au nanoparticles that were sputter-deposited onto native oxide-covered Si surfaces. High-resolution field emission scanning electron microcopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) have been used to characterize the formation and evolution of the nanoporous layer. Under Ar⁺ bombardment, the Au nanoparticles that were initially deposited were observed to flatten and spread across the native oxide surface, without diffusing, finally coalescing at their edges to form a nanoporous film having irregular pore dimensions. XPS showed that this evolution was accompanied by the loss of Au as a result of sputtering. The formation of such porous films necessitates strong interfacial bonding to avoid the lateral diffusion of the Au nanoparticles, and their ultimate coalescence into larger nanoparticles.We demonstrated that Ar⁺ beam bombardment invariably caused the formation of Au^δ+-Si^δ− bonding, rather than the expected Au^δ−-Si^δ+ bonding, and we explain this to be due to the resonance neutralization of the Ar⁺ beam on impacting the Au layer. We also reveal that the presumed formation of AuSi_x is not quantifiable by XPS, due to the superposition of the chemical shift of the Au nanoparticles with that of the quantum size effect, during Au loss on sputtering.