Stochastic nonlinear stabilization — II: Inverse optimality

After considering the stabilization of a specific class of stochastic nonlinear systems in a companion paper, in this second part, we address the classical question of when is a stabilizing (in probability) controller optimal and show that for every system with a stochastic control Lyapunov function it is possible to construct a controller which is optimal with respect to a meaningful cost functional. Then we return to the problem from Part I and design an optimal backstepping controller whose cost functional includes penalty on control effort and which has an infinite gain margin.     

Co_xFe_3－xO_4纳米晶的磁性与组成关系

各种组成的Ｃｏ＿ｘＦｅ＿３－ｘＯ＿４纳米晶是通过作者改进的化学共沉淀法制备的￣［１］。考察了系列组成Ｃｏ＿ｚＦｅ＿３－ｘＯ＿４样品的穆斯堡尔效应，推算出晶体中阳离子分布与饱和磁矩同Ｃｏ（Ⅱ）含量的关系。     

Nonlinear electrical transport in K-TCNQ at low temperatures

A remarkable nonlinearity has been observed for electric transport in K-TCNQ (potassium tetracyanoquinodimethane) quasi-one-dimensional conductor. The negative differential resistance region appears afterV _m (turn over voltage), beyond which voltage goes down with increase of current. A possible mechanism is discussed in terms of dynamics of charged solitons and domain walls in one-dimensional molecular stacks of these types of crystals.     

正则化长波方程的三次样条差分模拟

本文对正则化长波方程(RLW方程)的时间、空间项分别采用三次样条公式进行离散,所得到的差分方程为三点、三层隐格式,对时间的精度为四阶,对空间的精度为二阶,每个时间步只需求解一个三对角方程组,而三次样条配置法在每个时间步中需要求解三个三对角方程组。本文对单个孤立波的演化进行了计算,参数与文[8]相同,其结果与解析解的最大绝对误差均保持在10~(-3)的量级以内,与文[8]给出的数值方法精度相当。对两、三个孤立波的相互碰撞,本文结果显示出在忽略10~(-3)量级的误差后,碰撞前后的孤立波形状保持不变,无论是一个孤立波的演化,还是两、三个孤立波相互碰撞,当将波形放大100倍后均可以发现有振荡的尾波,这说明这类振荡尾波的产生并非真实的物理现象,而是由数值误差产生的。本文认为仅从工程应用的意义上说,RLW方程具有孤立子性质的结论是可以接受的。     

特低渗透油层含油饱和度的一种校正方法

松辽盆地北部扶杨油层属特低渗透油层，即使采用油基泥浆取心或密闭取心样品，束缚水饱和度也难以测准。蒸馏法试验表明，若试验温度低，则束缚水蒸发不彻底，实测含水饱和度偏低；若试验温度高，则容易造成岩样粘土矿物晶间水脱水，实测含水饱和度偏高，影响了储量计算精度。为搞清特低渗透油层流体蒸发特征，开展了蒸发率试验，试验过程是：将岩样洗油后重新饱和水，再在与蒸馏法试验相同的试验条件下测定蒸发的水量。试验结果表明，有效孔隙度越小，蒸发率越低。由于两个试验过程的蒸发率近似相等，用蒸发率试验可以模拟蒸馏法试验，由此推导出束缚水饱和度计算公式。应用该公式对榆树林油田进行测算，校正前后原始含油饱和度相差１２％以上，储量相差２０×１０６ｔ以上。图２（郭海莉摘）     

非线性隔振理论初探

本文以线必阻尼，立方刚度非线性系统为例，对非线性隔振理论进行了初步探讨，导出了系统的无量纲运动响应和传递率，并与线性隔振系统进行了比较，着重讨论了非线性对它们的影响，获得了一些有用的结论。     

双稳态孤子

对于具有一定形式非线性的薛定谔方程，存在单孤子解的多稳态，也就是说对于相同能量，单孤子具有不同的传输常数．本文以一非线住形式Ｌｉｎｅａｒ　Ｓｍｏｏｔｈ　Ｓｔｅｐ（ＬＳＳ）函数为例，对孤子的双稳态进行理论分析，并对其双稳态的光学转换进行数值模拟．     

Issues in nonlinear stochastic grey box identification

Grey box identification refers to the practice of identifying dynamical systems in model structures exploiting partial prior information. This contribution reviews a method for stochastic grey box identification and surveys experiences and lessons of applying it to a number of industrial processes. Issues to be addressed include advantages and costs of introducing stochastics into the model, the question of what contribution must be expected from the model designer as opposed to what can be formalized in computer algorithms, and an outlook on future plans to resolve present shortcomings.     

油气两相压降数值试井模型及其典型曲线的规律

提出油气两相流动压降试井数字模型的数值解法，用此解法对均质油藏中油气两相流动试井的规律进行了研究，根据实例计算结果，分析油气两相流下典型压降试井曲线的特征，以及油、气的初始饱和度分布，两相黏度比，饱和度梯度、相对渗透率关系对试井曲线的影响和相应的作用机理，首次发现气体的存在会使油气两相试井的压力导数曲线表现出类似于单相流双重介质试井的压力导数曲线的“下凹”特征。