Differential geometry based active fault tolerant control for aircraft

This work shows how to use a differential geometry tool to design a novel nonlinear active fault tolerant flight control system for aircraft. The proposed control scheme consists of two main subsystems: a controller, which is designed for the nominal plant, and a fault detection and diagnosis module, which provides fault estimation. A further feedback loop exploits the fault estimation to accommodate faults affecting the system. The estimate convergence and the stability of the active fault tolerant flight controller are theoretically proved. Finally, high fidelity simulations show the effectiveness of the scheme.     

Corrosion inhibition of triethanolammonium bromide mono- and dibenzoate as cationic inhibitors in an acidic medium

A weight loss technique was used to determine the corrosion inhibition efficiency of synthesized alkyl mono-and dibenzoate triethanolammonium bromide derivatives (TEAMB, TEADB) in an acidic medium (2 N HCl) at different doses (50, 100, and 200 ppm). The results showed that monoderivatives had a higher corrosion inhibition efficiency than diderivatives. The results were correlated with several factors, including the alkyl chain length of the hydrophobic chains, interfacial tension (IT), critical micelle concentration (CMC), and adsorption free energy of these inhibitors. Increasing the geometric length of the alkyl chains in the synthesized inhibitors had an increasing effect on their corrosion inhibition efficiency, whereas decreasing the CMC and IT had an increasing effect on their tendency toward corrosion inhibition. The number of hydrophobic chains attached to the inhibitor molecules had a vital influence on their efficiency as corrosion inhibitors.     

基于高斯核的SVM的参数选择

基于高斯核的支持向量机应用很广泛,高斯核参数σ的选择对分类器性能影响很大,本文提出了从核函数性质和几何距离角度来选择参数σ,并且利用高斯函数的麦克劳林展开解决了参数σ的优化选择问题。实验结果表明,该方法能较快地确定核函数参数σ,且 SVM 分类效果较好,解决了高斯核参数σ在实际应用中不易确定的问题。     

A Normalization Method of Moment Invariants for 3D Objects on Different Manifolds

3D objects can be stored in computer of different describing ways, such as point set, polyline, polygonal surface and Euclidean distance map. Moment invariants of different orders may have the different magnitude. A method for normalizing moments of 3D objects is proposed, which can set the values of moments of different orders roughly in the same range and be applied to different 3D data formats universally. Then accurate computation of moments for several objects is presented and experiments show that this kind of normalization is very useful for moment invariants in 3D objects analysis and recognition.     

Distributed control of nonlinear diffusion systems by input–output linearization

This paper addresses the distributed control by input–output linearization of a nonlinear diffusion equation that describes a particular but important class of distributed parameter systems. Both manipulated and controlled variables are assumed to be distributed in space. The control law is designed using the concept of characteristic index from geometric control by using directly the PDE model without any approximation or reduction. The main idea consists in the control design in assuming an equivalent linear diffusion equation obtained by use of the Cole–Hopf transformation. This framework helps to demonstrate the closed‐loop stability using some concepts from the powerful semigroup theory. The performance of the proposed controller is successfully tested, through simulation, by considering a nonlinear heat conduction problem concerning the control of the temperature of a steel plate modeled by a nonlinear heat equation with Dirichlet boundary conditions. Copyright © 2012 John Wiley & Sons, Ltd.     

输电塔-线体系覆冰作用非线性分析

在重冰区,高柔大跨越输电塔-线体系在覆冰、风载等作用下具有强烈的耦合特性和非线性特征。推导了绝缘子、索以及边界条件的刚度表达式,以向家坝-上海±800kV特高压直流输电线路为例,建立了输电塔、导线、绝缘子以及边界条件的简化数值分析模型。对大跨越输电塔－线体系进行了7种工况下的静力非线性分析。分析表明,在导线均匀覆冰及风荷载作用下,铁塔构件的P-△效应较小;在不均匀覆冰工况下,导线不平衡荷载对铁塔产生扭转效应,铁塔受压支座节点和最大悬臂处单元的轴向压力和弯矩具有较明显的P-△效应,应考虑荷载非线性的不利影响。     

几何过程与最优保修策略

研究了几何过程的特性,举例说明了它在最优保修策略中的应用,并对增加谈判力提出几点合理建议。     

非化学计量Li6F5团簇的几何结构和电离能

基于非化学计量Li6F5团簇的电离能的实验测量值,从第一性原理出发间接地确定了这个团簇的几何结构．首先选取若干可能的初始结构,然后在密度泛函理论框架内,使用B3LYP泛函和6—311＋G（d）基组优化所有初始结构,从而获得能量较低的同分异构体．对该团簇本文找到8个同分异构体,其中最低能量结构是一个对称性为Cs的三维构型．其计算的绝热电离能3．9eV与实验值4．1±0．1eV符合很好,表明本文找到的最低能量结构是可靠的．     

多维超几何分布的最可能成功数

超几何分布是一种重要的离散型概率分布,本文利用反证法以及比较法求出了三维超几何分布的最可能成功次数,并在此基础上,求出了多维超几何分布的最可能成功次数.     

Effect of variation in gas distribution on explosion propagation characteristics in coal mines

In order to investigate the effect of variation in the distribution of gas on explosion propagation characteristics in coal mines, experiments were carried out in two different channels with variation in gas concentration and geometry. Flame and pressure transducers were used to track the explosion front velocity. The flame speed (Sf) showed a slight downward trend while the methane concentration varied from 10% to 3% in the experimental channel. The peak overpressure (Pmax) dropped dramatically when com-pared with normal conditions. As well, the values of Pmax and Sf decreased when the methane concentration dropped from 8% to 6%. The flame speed in the channel, connected to a cylinder with a length varying from 0.5 to 2 m, was greater than that in the normal channel. The peak overpressure was also higher than that under normal conditions because of a higher flame speed and stronger pressure piling up. The values of Pmax and Sf increased with an increase in cylinder length. The research results indicate that damage caused by explosions can be reduced by decreasing the gas concentration, which should be immediately detected in roadways with large cross-sections because of the possibility of greater destruction caused by more serious explosions.