Tables of the Inverse Laplace Transform of the Function [... formula ...]

The inverse transform, g(t) = ?^?1(e^?sβ), 0 < β < 1, is a stable law that arises in a number of different applications in chemical physics, polymer physics, solid-state physics, and applied mathematics. Because of its important applications, a number of investigators have suggested approximations to g(t). However, there have so far been no accurately calculated values available for checking or other purposes. We present here tables, accurate to six figures, of g(t) for a number of values of β between 0.25 and 0.999. In addition, since g(t), regarded as a function of β, is uni-modal with a peak occurring at t = t_max we both tabulate and graph t_max and 1/g(t_max) as a function of β, as well as giving polynomial approximations to 1/g(t_max).     

Spectral Representation for a Class of Non-Gaussian Processes

A new model is developed for non-Gaussian processes. The model is based on the spectral representation theorem for weakly stationary processes, can match the second moment properties and several higher order moments of any non-Gaussian process, and consists of a superposition of harmonics with uncorrelated but dependent random amplitudes. The calibration of the model to a target non-Gaussian process may require iterations. The It? formula is used to calculate higher-order moments of the proposed model. These moments can be used to tune the model such that it matches some of the higher-order moments of a target non-Gaussian process in addition to its second-moment properties. The proposed model is useful for both Monte Carlo simulation and analytical studies on the response of linear and nonlinear systems to non-Gaussian noise. Examples are presented to illustrate the use of the proposed model.     

Anaerobic Treatment of High Sulfate Wastewater with Oxygenation to Control Sulfide Toxicity

In this study, oxidation-reduction potential (ORP) was employed to regulate oxygen dosing for online sulfide toxicity control during anaerobic treatment of high sulfate wastewater. The experiment was conducted in an upflow anaerobic filter, which was operated at a constant influent total organic carbon of 6,740 mg/L [equivalent to a chemical oxygen demand (COD) of 18,000 mg/L], but with different influent sulfates of 1,000, 3,000, and 6,000 mg/L. The reactor was initially run at natural ORP (the system’s ORP without oxygenation) of about ?290 to ?300?mV and then was followed by oxygenation to raise ORP by +25?mV above the natural level for each influent sulfate level. At 6,000 mg/L sulfate under the natural ORP, methanogenesis was severely inhibited due to sulfide toxicity, and the anaerobic process was almost totally upset. Upon oxygenation by raising ORP to ?265?mV, the dissolved sulfide was quickly reduced to 12.2 mg S/L with a concomitant improvement in methane yield by 45.9%. If oxygen was not totally used up by sulfide oxidation, the excess oxygen was consumed by facultative bacteria which had been found to stabilize about 13.5% of the influent COD. Both sulfide oxidation and facultative activity acted as a shield to protect the anaerobes from an excessive oxygen exposure. This study showed that direct oxygenation of the recirculated biogas was effective to oxidize sulfide, and the use of ORP to regulate the oxygen dosing was practical and reliable during anaerobic treatment of high sulfate wastewater.     

长江科学院长江泥沙若干问题研究与实践

简要介绍了近50年来,长江河道水流泥沙运动、河道演变、河道整治及水利枢纽泥沙问题研究情况与所取得的进展,提出了需要继续深入研究的若干重大问题,包括长江水土资源综合利用、干支流水库群联合运用对水沙及江湖演变的影响与对策、长江中下游河道和湖泊及长江口治理研究等。     

Spinodal decomposition of binary mixtures with composition-dependent heat conductivities

Spinodal decomposition of a very viscous binary mixture is simulated, assuming that the fluid is bounded by two walls that are instantaneously quenched below the critical temperature. As usual, the mixture phase separates by forming dendritic structures whose size grows with time. While in conventional spinodal decomposition the morphology of the mixture is isotropic, here we show that, when the two components of the mixture have different heat conductivities, the configuration of the mixture may become anisotropic, depending on whether heat propagates slower or faster than mass. Specifically, for large heat conductivity differences, when the Lewis number is small, dendrites tend to align parallel to the isothermal lines; when it is large, dendrites progressively align perpendicular to the isothermal lines. This behavior can be explained observing that the morphology of the mixture is the result of two competing effects: on one hand, the mixture phase separates as soon as its temperature reaches its critical value and therefore it tends to follow the isothermal lines; on the other hand, the system tend to maximize heat transport, and therefore dendrites tend to span between the two quenched walls, i.e. perpendicular to the isothermal lines. This explanation is confirmed showing that when the imposed temperature difference between the side walls (and therefore the heat flux at equilibrium as well) is increased, dendrites tend to align across the walls more and more.     

On the synthesis and crystallization process of nanocrystalline PZT powders obtained by a hybrid sol–gel alkoxides route

Sol–gel synthesis has been a very successful and efficient route for obtaining high quality ferroelectric materials. Particularly, the alkoxides based route has proven its advantages due to the better homogeneity and easier controlled gelation rate. In this work, butoxides and propoxides are used to obtain nanocrystalline PZT powders in order to determine the influence of each B-site precursor on crystallization. Along with this, we study the involved chemical reactions (reactants and intermediates) and the crystallization process by using several spectroscopic techniques (Raman, FT-IR and XRD) as well as thermogravimetric (TGA) and calorimetric (DTA) analysis. The evolution of the initial gel solution and the amorphous powder into the final perovskite PZT phase is traced. According to our results, the propoxy route tends to be the more suitable for good PZT crystallization under our experimental conditions.     

污染型类高斯噪声中信号的Robust-SA检测

采用了Ｒｏｂｂｉｎｓ－Ｍｏｒｒｏ随机逼近算法，得到了Ｒｏｂｕｓｔ－ＳＡ检测器。它的主要特点是具有Ｍ－检测器的优点，且便于实时处理和计算机编程。理论分析与仿真例子都表明：此检测器具有良好的顽健性，能很好的检测信号。     

Heteroepitaxial growth of Zn1−xCdxSe on cleavage-induced GaAs (110) surface in ultra high vacuum

Zn_1−xCd_xSe epitaxial growth by molecular beam epitaxy (MBE) on the GaAs (110) surface cleaved in ultra high vacuum (UHV) was investigated. The growth mode of Zn_1−x Cd_xSe on GaAs (110) was not a simple Stranski–Krastanow type. At initial growth stage, growth mode was two-dimensional type. However, as the growth proceeds three-dimensional island growth and two-dimensional growth modes compete. As a result, two kinds of structures were spontaneously formed on the surface, pyramidal-shaped islands and ridge structures aligned to the [1 0] direction. Anisotropic in-plane strain relaxation on (110) is suggested as the formation mechanism of such structures.     

Growth rate reduction in self-limiting growth of doped GaAs by molecular layer epitaxy

Self-limiting growth of GaAs with doping by molecular layer epitaxy (MLE) has been studied using the intermittent supply of TEG, AsH₃, and a dopant precursor, Te(C₂H₅)₂ (diethyl-tellurium: DETe) for n-type growth on GaAs (0 0 1). The self-limiting monolayer growth is applicable at 265°C, however, the growth rate per cycle of doping decreased and saturated at about 0.4 monolayer with increasing doping concentration. To clarify the mechanism of growth with doping and to solve the problem of the growth rate reduction, a doping cycle followed by several cycles of undoped growth was performed. The growth rate reduction in the TEG–AsH₃ system is due to the electrical characteristics of the growing surface, namely, the exchange reaction of TEG is reduced with increasing doping concentration.