Preparation and photoluminescence of surface N-doped ZnO nanocrystal

ZnO nanoparticles doped with nitrogen on surface were prepared by calcinating pure ZnO nanoparticles at 550 and 600 °C in NH₃ atmosphere. Uniform N-doped ZnO nanocrystal was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and XPS. A Strong violet photoluminescence (PL) at 400nm was observed at room temperature when excited with 300 nm light, and the emission peak increases with the increase of nitrogen atoms concentration. The violet PL originated from the electron transition from shallow donor levels of oxygen vacancies and doping nitrogen atoms to the top of valence band level.     

纳米复合永磁材料的研究进展

纳米复合永磁材料兼具硬磁性相的高矫顽力和软磁性相的高饱和磁化强度,磁性能优异。本文综述了纳米复合永磁材料的磁性相晶粒间的交换耦合作用、矫顽力机制、微磁学模拟等理论方面的研究进展,同时论述了成分、添加元素、制备工艺对材料微观结构和磁性能的影响,着重介绍了最有应用价值的快淬法磁粉制备工艺。     

H∞ filtering for a class of discrete-time singular Markovian jump systems with time-varying delays

The problem of _H∞$H_{\infty }$ filtering for a class of discrete-time singular Markovian jump systems with time-varying delays is investigated in this paper. The transition probabilities under consideration are time-varying, i.e., Markovian chain is nonhomogeneous. By using the Lyapunov functional approach and reciprocally convex technique, a less conservative delay-dependent bounded real lemma is developed in terms of linear matrix inequalities. Moreover, a sufficient condition for the existence of the desired filter which guarantees the stochastic admissibility and the _H∞$H_{\infty }$ performance index of the resulting filtering error system is presented. Numerical examples are employed to show the usefulness of the proposed results.     

袋装生活垃圾破碎设备缠绕问题研究

我国城市袋装垃圾处理尚处在研发阶段,垃圾破碎设备的条件性破袋破碎、分选、防缠绕、刀具避让等问题是急需解决的关键技术.从垃圾缠绕物受力的角度分析造成缠绕的原因,确定形成缠绕的必要条件,导出数学表达式,分析垃圾破碎设备主要参数对缠绕的影响并提出防缠绕的一些方法与措施.     

Pipelined robust M-estimate adaptive second-order Volterra filter against impulsive noise

The main limits on adaptive Volterra filters are their computational complexity in practical implementation and significant performance degradation under the impulsive noise environment. In this paper, a low-complexity pipelined robust M-estimate second-order Volterra (PRMSOV) filter is proposed to reduce the computational burdens of the Volterra filter and enhance the robustness against impulsive noise. The PRMSOV filter consists of a number of extended second-order Volterra (SOV) modules without feedback input cascaded in a chained form. To apply to the modular architecture, the modified normalized least mean M-estimate (NLMM) algorithms are derived to suppress the effect of impulsive noise on the nonlinear and linear combiner subsections, respectively. Since the SOV-NLMM modules in the PRMSOV can operate simultaneously in a pipelined parallelism fashion, they can give a significant improvement of computational efficiency and robustness against impulsive noise. The stability and convergence on nonlinear and linear combiner subsections are also analyzed with the contaminated Gaussian (CG) noise model. Simulations on nonlinear system identification and speech prediction show the proposed PRMSOV filter has better performance than the conventional SOV filter and joint process pipelined SOV (JPPSOV) filter under impulsive noise environment. The initial convergence, steady-state error, robustness and computational complexity are also better than the SOV and JPPSOV filters.     

Thermoelectric performance of polycrystalline Sn1-xCuxSe (x = 0–0.03) prepared by high pressure method

P-type Sn_1-xCu_xSe (x = 0–0.03) polycrystal was prepared through melting synthesis and high pressure (6.0 GPa) sintering (HPS) method. The composition and microstructure of the samples was analyzed, and the thermoelectric transport properties were investigated in the temperature range of 303 K–823 K. The results indicate that the electrical conductivity increases as Cu content increases. An observable improvement is found for the Seebeck coefficient when x is 0.01. In addition, the total thermal conductivities (κ_tot) of all samples decrease with rising temperature, and reach its minimum values at 773 K. As a result, the maximum power factor (PF) and ZT_max value are 378 μW m⁻¹ K⁻² and 0.79 for Sn_0.97Cu_0.03Se at 823 K, respectively.     

高放废液煅烧工艺的研究现状

高放废液安全有效的处理与处置是世界各国关注的重要课题。常采用煅烧技术对高放废液进行预处理，达到实现减少高放废物的产生量、降低高放废物处置的风险的目的。本文主要以常见的几种预处理煅烧工艺技术（罐式煅烧法、喷雾煅烧法、流化床煅烧法和回转煅烧法等）为研究对象，分别从煅烧机理、研究现状及优缺点等多个方面进行较系统的分析探讨。     

Solution of the point reactor kinetics equations with temperature feedback by the ITS2 method

The ITS2 method is used to solve the point-reactor kinetics equations in the integral formulation with arbitrary number of delayed neutron groups and Newtonian temperature feedback. The method is based on low-order Taylor series expansions of neutron density and reactivity functions and uses variable time steps to control the numerical instabilities resulting from the stiff nature of the governing equations. Time steps are determined through an analytic criterion relating their magnitudes to the maximum admissible truncation error in the neutron-density expansion series. Temperature feedback is included in the reactivity as a function of the neutron density for different input types, including step change with adiabatic temperature feedback and compensated ramp functions. An iterative procedure is applied to determine the time steps while simultaneously updating the reactivity function. Numerical results show the ITS2 method is highly accurate for solving point reactor dynamics problems with temperature feedback.     

无砾石微孔管地下渗滤中试系统的实验研究

在无砾石微孔管中试系统中,设置了土壤、植物、管径三个参变量进行正交实验,对系统中各个单体产生的不同处理效果进行分析,并研究了降雨量、温度、进水水质对污染物去除率的影响。结果表明：大管径和砂壤土处理效果较好,系统中氮的去除率随进水浓度和气温变化较大。     

Application of Taguchi approach to optimize the sol–gel process of the quaternary Cu2ZnSnS4 with good optical properties

Present research deals with the optimal deposition parameters configuration for the synthesis of Cu₂ZnSnS₄ (CZTS) thin films using the sol–gel method associated to spin coating on ordinary glass substrates without sulfurization. The Taguchi design with a L9 (3⁴) orthogonal array, a signal-to-noise (S/N) ratio and an analysis of variance (ANOVA) are used to optimize the performance characteristic (optical band gap) of CZTS thin films. Four deposition parameters called factors namely the annealing temperature, the annealing time, the ratios Cu/(Zn + Sn) and Zn/Sn were chosen. To conduct the tests using the Taguchi method, three levels were chosen for each factor. The effects of the deposition parameters on structural and optical properties are studied. The determination of the most significant factors of the deposition process on optical properties of as-prepared films is also done. The results showed that the significant parameters are Zn/Sn ratio and the annealing temperature by applying the Taguchi method.