基于ADM1模型的沼气生产过程的模型参数选择和辨识

国际水协IWA提出的ADM1模型可以较好地描述厌氧发酵过程,但其大量的模型参数使其在实际应用中存在困难。针对ADM1模型,在分析了各可变参数的可辨识性和灵敏度后,确定六种参数对于整个动态过程影响较大。因此,可以对这六种参数进行辨识,从而得到一个较好的ADM1模型。以此为基础,针对ADM1具体实施条件进行了仿真建模,利用标准仿真软件STOAT生成数据,通过求解一个非线性最优化问题得到参数的最优估计值,进而通过辨识后的模型进行仿真比较,验证了本文的结论。     

Use Hausdorff metric to analyze convergence of parameter estimation in system identification

For a linear time-invariant system model, this paper analyzes the convergence of parameter estimations as the length of the input–output data tends to infinity through the prediction error method. It is known that the sequence of the criterion functions converges uniformly in the parameter with probability one as the data length tends to infinity. The parameter estimation is represented by a set in general, instead of by a single point, on which the criterion function takes its minimum. Thus a mathematical feature of the convergence problem of parameter estimation is in that we are needed, from the convergence of a sequence of functions, to infer the convergence of the sequence of their sets of minimizing arguments. The Hausdorff metric is suggested to measure the distance between sets and then is used to discuss the convergence problem here. According to the Hausdorff metric, the convergence of parameter estimation is not guaranteed in general. A condition guaranteeing such convergence is given.     

Rheological properties of polystyrene and poly(methyl methacrylate) blends

Rheological properties of the polystyrene (PS) and poly(methyl methacrylate) (PMMA) blends were studied by Advanced Rheometric Expansion System (ARES). Storage modulus and loss modulus of the PS and PMMA blends were measured, and the interfacial tension of the PS and PMMA blends were obtained with various emulsion models by using the storage modulus and loss modulus of the blends. The value of interfacial tension estimated from the Palierne emulsion model was found to be 2.0 mN/m. Also, the interfacial tension between PS and PMMA was calculated by a theoretical model. The values of interfacial tension of the PS and PMMA blends obtained by the experiment and theoretical model were found to be in good agreement.     

低温快烧强化瓷的研究

本文扼要地介绍了低温快烧强化瓷的坯釉配方、所用主要原料、工艺参数及瓷质的主要性能，并得出了相关结论。     

Adaptive parameter identification of linear SISO systems with unknown time-delay

An adaptive online parameter identification is proposed for linear single-input-single-output (SISO) time-delay systems to simultaneously estimate the unknown time-delay and other parameters. After representing the system as a parameterized form, a novel adaptive law is developed, which is driven by appropriate parameter estimation error information. Consequently, the identification error convergence can be proved under the conventional persistent excitation (PE) condition, which can be online tested in this paper. A finite-time (FT) identification scheme is further studied by incorporating the sliding mode scheme into the adaptation to achieve FT error convergence. The previously imposed constraint on the system relative degree is removed and the derivatives of the input and output are not required. Comparative simulation examples are provided to demonstrate the validity and efficacy of the proposed algorithms.     

流加式聚合反应生产过程的动态模型及其参数估计

流加式聚合反应生产过程相当复杂,其模型化同时涉及聚合反应动力学、传热、相变原理以及热量、质量动态平衡定律等。本文为一类流加式聚合反应生产过程建立了动态数学模型,并基于某化工厂聚醚釜的实际运行数据估计了其中的各种参数。从而为开发此类过程的控制和优化方案提供了基础。     

Axial dispersion in single pellet-string columns with non-porous packing

Using the chromatographic technique (carrier-gas: nitrogen; tracer-gases: H₂, He, Ar, C₂H₆) the axial dispersion in single pellet-string columns (SPSC) packed with non-porous spherical and cylindrical particles was studied. Dispersion due to extra column effects was eliminated via convolution of column responses for two column lengths. For spherical pellets the pellet/column diameter ratios (d_p/d_c) were in the range 0.57-0.79; for cylindrical pellets d_p/d_c=0.52-0.69 with pellet height/diameter ratios H/D=0.78-1.5. With different tracer-gases and the same packing and column sizes analogous dependencies of Bodenstein numbers, Bo (Peclet number, Pe, with pellet size, d_p, as characteristic dimension), versus the product of Reynolds and Schmidt numbers, ReSc, were obtained. For spherical column packing the Bo-ReSc curves depend also on the d_p/d_c ratio; for cylindrical pellets the sphericity (which depends on H/D ratio) plays an additional role. Empirical interpolation equations for both shapes of pellets were set up.The obtained information on axial dispersion significantly increases the confidence of pore-diffusion characteristic when the chromatographic method with SPSC packed with porous pellets is applied.     

EXPERIMENTAL INVESTIGATION OF KINETIC AND TRANSPORT PARAMETERS IN A WALL－COOLED FIXED－BED REACTOR

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Precise parameter estimation for chemical batch reactions in heterogeneous medium

A sequential experimental strategy for precise parameter estimation has been used in the case of liquid-liquid dispersions in batch-stirred tank reactors where slow chemical reactions take place. The mathematical model for a batch reaction in a stirred tank reactor is formulated as a system of non-linear differential equations standing for the mass balance of each component. Physical kinetic parameters and chemical kinetic parameters which arise from this model are estimated simultaneously. The estimation problem is posed as a weighted least squares problem and solved by using a standard Levenberg-Marquardt algorithm. In this work, we intend to show how it is possible to develop efficient experimental design strategies that lead to an accurate estimation of the parameters involved in phenomenological models and most particularly in kinetic models. Three design criteria for designing the experiments have been employed in order to increase the precision on the parameter estimates of the model. A standard non-linear sequential quadratic programming method ensures the determination of the operating conditions which define the experimental design. The well-known alkaline hydrolysis of esters in aqueous phase has been treated as a numerical application example.