生物膜动力学的研究现状与展望

生物膜法作为一种高效的废水处理工艺已获得到了广泛的工程应用.生物膜的形成、结构 及其动力学特性对废水处理效果至关重要.本文综述了生物膜的形成过程及其动力学模型的 研究进展,阐述了最近十几年来实验研究中的新发现和新方法,最后展望了将来的研究方向.      

Global Pressure of One-Dimensional Polydisperse Granular Gases Driven by Gaussian White Noise

We study the global pressure of a one-dimensional polydisperse granular gases system for the first time, in which the size distribution of particles has the fractal characteristic and the inhomogeneity is described by a fractal dimension D. The particles are driven by Gaussian white noise and subject to inelastic mutual collisions. We define the global pressure P of the system as the impulse transferred across a surface in a unit of time, which has two contributions, one from the translational motion of particles and the other from the collisions. Explicit expression for the global pressure in the steady state is derived. By molecular dynamics simulations, we investigate how the inelasticity of collisions and the inhomogeneity of the particles influence the global pressure. The simulation results indicate that the restitution coefficient e and the fractal dimension D have significant effect on the pressure.     

Synthesis of Aminoazobenzene‐Containing Diblock Copolymer and Photoinduced Deformation Behavior of its Micelle‐Like Aggregates

A precursor polymer PEO‐b‐PEMA that contains anilino moieties is synthesized from EPAEMA by ATRP by using a PEOBr macroinitiator and CuBr/HMTETA catalyst system. The aminoazobenzene‐containing block copolymer PEO‐b‐PCN is obtained by the azo‐coupling reaction between PEO‐b‐PEMA and the diazonium salt of 4‐aminobenzonitrile. Results show that PEO‐b‐PCN has a narrow molecular weight distribution and the repeat unit numbers of the hydrophilic and hydrophobic blocks are 122 and 200, respectively. PEO‐b‐PCN can form uniform spherical aggregates by gradually adding water into its THF solution. Upon irradiation with a linearly polarized Ar⁺ laser beam, the spherical aggregates can be significantly elongated in the polarization direction of the light.

     

Representation of discrete sequences with N-dimensional iterated function systems in tensor form

Iterated Function System (IFS) models have been used to represent discrete sequences where the attractor of the IFS is self-affine or piecewise self-affine in R ² or R ³ (R is the set of real numbers). In this paper, the piecewise hidden-variable fractal model is extended from R ³ to R ⁿ (n is an integer greater than 3), which is called the multi-dimensional piecewise hidden variable fractal model. This new model uses a “mapping partial derivative” and a constrained inverse algorithm to identify the model parameters. The model values depend continuously on all the hidden variables. Therefore the result is very general. Moreover, the piecewise hidden-variable fractal model in tensor form is more terse than in the usual matrix form.     

污泥活性炭的结构特征及表面分形分析

以城市污水厂污泥为主要原料添加适量添加剂, 采用ZnCl₂化学活化法制备的污泥活性炭, 借助XRD, BET法, FT-IR, SEM等现代分析测试方法结合液相吸附法, 表征结构特征和分析表面分形维数. 结果表明: 在适宜的活化温度、活化时间、ZnCl₂浓度、原料粒度等工艺条件下, 加入少量添加剂制备的污泥活性炭, 最可几孔径分布在4.16 nm左右,平均孔容0.4484～0.5122 mL•g^－1, 比表面积为634.8～748 m²•g^－1, IR峰中出现C—OH, C—H, N＝O, C＝C功能组, 孔结构是具有平行壁的狭缝状介孔结构. 由液相吸附法得到的污泥活性炭分维近似为2, 属于低分维二维表面.     

Fractal structure and fractal dimension determination at nanometer scale

Three-dimensional fractures of different fractal dimensions have been constructed with successive random addition algorithm, the applicability of various dimension determination methods at nanometer scale has been studied. As to the metallic fractures, owing to the limited number of slit islands in a slit plane or limited datum number at nanometer scale, it is difficult to use the area-perimeter method or power spectrum method to determine the fractal dimension. Simulation indicates that box-counting method can be used to determine the fractal dimension at nanometer scale. The dimensions of fractures of valve steel 5Cr21Mn9Ni4N have been determined with STM. Results confirmed that fractal dimension varies with direction at nanometer scale. Our study revealed that, as to theoretical profiles, the dependence of frsctal dimension with direction is simply owing to the limited data set number, i.e. the effect of boundaries. However, the dependence of fractal dimension with direction at nanometer scale in real metallic fractures is correlated to the intrinsic characteristics of the materials in addition to the effect of boundaries. The relationship of fractal dimensions with the mechanical properties of materials at macrometer scale also exists at nanometer scale. Project supported by the National Natural Science Foundation of China (Grant Nos. 59771050 and 59872004) and the Foundation Fund of Ministry of Metallurgical Industry.     

The Fractal Characteristic of Particles in Granular Material Flows and Its Effect on Effective Thermal Conductivity

According to the fact that many pulverized particles possess fractal characteristic, a fractal model for studying fine particles in granular material flows is first proposed. An expression of particles' fractal distribution is derived to describe the relationship between the particle fractal dimensions and particle velocity distribution function. In accordance with this model, the theoretical particle effective thermal conductivity is derived. The analytical results show that for the small Biot-Fourier number, the effective thermal conductivity increases with the square root of the granular temperature. For very large Biot-Fourier number, the effective thermal conductivity linearly increases with the granular temperature. Numerically calculated results show that the thermal conductivity increases with the particle size fractal dimensions and decreases with the particle surface fractal dimensions.     

粒径均匀散体导热系数的分形描述

本文以分形理论为工具,采用填充率、散体颗粒直径等宏观易等测参数较准确地描述了颗粒散体的几何结构;运用导热与逾渗的类比,建立了均匀散体导热系数的逾渗模型,模型的预测值与实验测量结果基本一致。     

紫外光照射对LB膜光致荧光特性的影响

采用稳态和时间分辨荧光光谱技术,研究了非偏振紫外光照射对氐盐有机分子LB交替多层膜光致荧光特性的影响。紫外光照射可以使有机分子的聚集体部分分解甚至破坏分子的结构,导致光致荧光强度明显减弱