时滞种群模型的正周期解对所有正解的吸引性

建立了对数种群模型Ｎ′（ｔ）＝Ｎ（ｔ）｛ｒ（ｔ）－ａ１（ｔ）ｌｎ［Ｎ（ｔ）］－ａ２（ｔ）ｌｎ［Ｎ（ｔ－τ（ｔ））］｝的周期正解的存在性，并得到了正周期解对所有正解的吸引性．     

A geometric theory forL 2-stability of the inverse problem in a one-dimensional elliptic equation from anH 1-observation

This study provides a stability theory for the nonlinear least-squares formulation of estimating the diffusion coefficient in a two-point boundary-value problem from an error-corrupted observation of the state variable. It is based on analysing the projection of the observation on the nonconvex attainable set.This research was started while G. Chavent visited the Technical University of Graz. Support through the Steiermaerkische Landesregierung is gratefully acknowledged.     

On a recursive method for the estimation of unknown parameters of partially observed chaotic systems

We investigate a recently proposed method for on-line parameter estimation and synchronization in chaotic systems. This novel technique has been shown effective to estimate a single unknown parameter of a primary chaotic system with known functional form that is only partially observed through a scalar time series. It works by periodically updating the parameter of interest in a secondary system, with the same functional form as the primary one but no explicit coupling between their dynamic variables, in order to minimize a suitably defined cost function. In this paper, we review the basics of the method, and investigate its robustness and new extensions. In particular, we study the performance of the novel technique in the presence of noise (either observational, i.e., an additive contamination of the observed time series, or dynamical, i.e., a random perturbation of the system dynamics) and when there is a mismatch between the primary and secondary systems. Numerical results, including comparisons with other techniques, are presented. Finally, we investigate the extension of the original method to perform the estimation of two unknown parameters and illustrate its effectiveness by means of computer simulations.     

一类过程摄动系统的无阻塞鲁棒性

使用参数Dioid模块网络法,把含大量摄动参数的在普通极大代数意义下非线性状态空间模型在参数Dioid意义下线性化,在此基础上研究一类过程摄动系统的无阻塞鲁棒性.给出了有限缓冲串行生产系统在没有缓冲器下无阻塞的充要条件和充分条件.     

金属表面在反射方向产生光学二次谐波的研究(Ⅰ)

用Rudnick和Stern引入的唯象参数“a”和“b”来描述表面电流,本文推导了金属表面在反射方向产生的光学二次谐波的表达式.由此证明了:从谐波信号随入射光偏振态的变化可以直接得到关于参数“a”的信息.和过去的实验相比,这种方法能更加精确、可靠地测定“a”的数值.     

Structural optimization with parameter-transfer finite element

A mathematical method to solve structural problems, using parameter-transfer finite elements (P-TFE) was recently proposed by the authors [1] [2] [3]. The proposed transfer finite element approach is able to create a mathematical model of a structure, taking into account directly the whole behaviour of the structure under dynamic, aerodynamic, and thermal actions, and not by assembling, in a separate fashion, the stiffness and the mass matrix on one side and the external load vector as performed by the classical finite element procedure.The purpose of this paper is to apply the above methodology to optimization problems, in particular to obtain the minimum structural weight for a beam, under primary constraints on buckling load or natural frequencies.The use of P-TFE in the field of structural optimization overcomes most difficulties of the usual techniques of solution and the element is particularly useful in the evaluation of the sensitivity matrix.The formulation of the optimization problem based on P-TFE is presented and some applications are studied. The numerical results obtained are compared with other existing methodologies and briefly discussed.

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Sommario Gli autori hanno già proposto un metodo per studiare problemi strutturali [1] [2] [3], introducendo una nuova metodologia di discretizzazione, basata sull'impiego di elementi finiti di trasferimento, funzioni esplicite di un parametro, indicati come P-TFE. Tali elementi sono in grado di rappresentare, in similitudine alla funzione di trasferimento, il comportamento completo dell'elemento strutturale in esame, soggetto ad azioni dinamiche, aerodinamiche e termiche; sono parimenti in grado di produrre, in similitudine al metodo degli elementi finiti, un modello matematico discreto di un continuo.Scopo del presente lavoro è di applicare detta metodologia a problemi di ottimizzazione, in particolare alla ricerca del minimo peso per una trave che mantenga inalterate le sue caratteristiche di carico critico o le frequenze naturali di vibrazione.Vengono quindi presentati alcuni risultati numerici dei casi esaminati e confrontati con quelli ottenuti da altri autori con l'impiego di altre metodologie.

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List of Symbols {B} _m vector of the generalized state variables - {C} _m vector of integration constants - [I] unit matrix - EI bending stiffness - A cross-sectional area - u adimensional thickness - l beam length - M,M bending moment - [N] _m shape function ofm-th order - [N*] shape function atx ₀ - P axial load - [R] _i transfer matrix of thei-th element - T,T shear force - w transverse displacement - x adimensional independent variable - x ₀ value ofx at the left of the element - {Y} vector of state variables - {Y*} imposed condition atx ₀ - _0m Kronecker delta with the first pedix always set equal to zero - normalized eigenfrequency - normalized buckling load - mass density     

特征线法在求解非线性液相吸附色谱模型中的应用

本文应用特征线法求解非线性液相吸附色谱分离过程模型，论述了特征线法的原理和步骤，讨论了时间步长和空间步长对模型数值解的影响，并用色谱分离甘露醇和山梨醇以及分离蔗糖和还原糖的实验进行验证，用特征线法计算的理论流出曲线与实验流出线吻合较好。本文还分折了模型中各个参数的灵敏度，结果表明：吸附等温方程Q＝Ci*／（ai＋biCi*）中参数ai比参数bi以及总传质系数ki有更高的灵敏度。     

中国正常人体内元素含量的检测研究

开展正常人体内元素含量的检测研究具有重要生物学意义，不仅可充实我国正常成年人脏器组织元素含量值的基础医学数据，为研究人体内微量元素与健康的关系提供科学依据、也为辐射防护领域内放射性核素的剂量估算提供重要参数。本文从以下五个方面进行了论述：（）体内元素含量检测研究的目的、意义及其概况；（2）元素含量检测的重要性及其历史沿革；（3）元素的检测方法及质量控制；（4）人体内脏器组织元素含量的数值；（5）与国外资料相比较。本文着重介绍了我国100例正常成年人20个脏器组织（包括胃、小肠、大肠、心、肝、脾、肺、肾、…     

新型醋酸乙烯酯／二乙烯苯共聚物的研究（Ⅱ）──醇解物的制备、结构及其性能

新型醋酸乙烯酯／二乙烯苯共聚物的研究（Ⅱ）──醇解物的制备、结构及其性能吴向东，郭贤权，何炳林（南开大学高分子化学研究所，天津，３０００７１）关键词皂化反应，醇解物，芳香族氨基酸，孔结构参数，吸附性能氨基酸失衡是指肝性脑病患者血液中芳香族氨基酸的浓度...     

碳纤维微电极研究(Ⅺ)——利用温度效应测定电极反应的热力学和动力学参数

研究了温度对碳纤维微电极上伏安曲线的影响及温度与电极电位的关系,测定了电极反应的热力学参数.由电流与温度的关系测定了去极剂的扩散活化能E_(al)和D_o,利用微电极具有高速传质的特性,测定了常规电极上为可逆反应的电极反应标准速率常数(?),并通过(?)与温度的关系测定了电极反应的活化能.