Homotopy analysis method for heat radiation equations

Here, the homotopy analysis method (HAM), one of the newest analytical methods which is powerful and easy-to-use, is applied to solve heat transfer problems with high nonlinearity order. Also, the results are compared with the perturbation and numerical Runge–Kutta methods and homotopy perturbation method (HPM). Here, homotopy analysis method is used to solve an unsteady nonlinear convective–radiative equation containing two small parameters of ?₁ and ?₂. The homotopy analysis method contains the auxiliary parameter h¯, which provides us with a simple way to adjust and control the convergence region of solution series.     

Perturbation LDA: Learning the difference between the class empirical mean and its expectation

Fisher's linear discriminant analysis (LDA) is popular for dimension reduction and extraction of discriminant features in many pattern recognition applications, especially biometric learning. In deriving the Fisher's LDA formulation, there is an assumption that the class empirical mean is equal to its expectation. However, this assumption may not be valid in practice. In this paper, from the “perturbation” perspective, we develop a new algorithm, called perturbation LDA (P-LDA), in which perturbation random vectors are introduced to learn the effect of the difference between the class empirical mean and its expectation in Fisher criterion. This perturbation learning in Fisher criterion would yield new forms of within-class and between-class covariance matrices integrated with some perturbation factors. Moreover, a method is proposed for estimation of the covariance matrices of perturbation random vectors for practical implementation. The proposed P-LDA is evaluated on both synthetic data sets and real face image data sets. Experimental results show that P-LDA outperforms the popular Fisher's LDA-based algorithms in the undersampled case.     

N型金属氧化物晶体 Poisson 方程的解

提出了任意形状、无量纲ｎ型晶体的Ｐｏｉｓｓｏｎ方程：ｄ２ψｄｙ２＋η－１ｙｄψｄｙ＝１－Ｒｅ－ψ（η＝１～３,０≤Ｒ≤１）,并用微扰理论对其进行了求解．     

基于STK/X的远程导引变轨方案修正

远程导引多脉冲式变轨方案一般基于二体模型进行设计,设计结果存在摄动模型误差.当飞行时间较长时,由摄动模型误差带来的交会误差会达到上百公里甚至上千公里的量级,从而在实际摄动条件下难以实现追踪航天器和目标航天器的交会.采用L-BFGS-B优化算法,对初始的设计结果进行修正,以达到消除摄动模型误差的目的.优化过程中需要的真实摄动模型下的轨道预报,使用STK/X技术通过调用STK/Astrogator模块进行仿真得到.算例表明,初始设计的多脉冲式变轨方案经过修正后,能够在实际摄动条件下实现追踪航天器和目标航天器的交会.     

风速、入射角对海面谐振散射的影响

根据微扰法研究波散射,在谐振散射模型基础上导出布拉格散射系数,并分析海表面波对散射系数的影响.考虑海表面斜度的变化,对谐振散射系数进行修正,得出修正后的散射系数,发现散射系数的修正值受海面高度起伏均方根的影响,计算得出海面高度起伏均方根与风速的关系.在30 m深度海域进行试验,入射波角度分别为35°、45°和55°情况...     

Identification of higher-dimensional ill-conditioned systems using extensions of virtual transfer function between inputs

A new formulation is proposed to directly extend the virtual transfer function between inputs (VTFBI) approach to ill-conditioned systems with dimensions higher than 2 × 2. The method requires only a single correlated component and is applicable to moderately large systems of up to around six outputs. To cater for systems with even higher dimensions, an indirect approach is further introduced based on subsystem decomposition in which the design for each subsystem achieves D-optimality in the presence of active output variance constraints. New measures of sensitivity to measurement inaccuracy and parameter changes are also introduced. A detailed case study shows that both direct and indirect extensions of the VTFBI technique outperform competing ones in terms of accuracy in the estimation of singular values, robustness towards the effect of noise as well as effectiveness for application in model based control. An additional advantage of the proposed approaches is that their performance does not depend significantly on the specific design choices made within these methods.     

Mathematical model for calculation of thickness of flame sprayed coating of aluminium on S235JR steel

Abstract

In the present work, the method of response surfaces was employed for the purpose of drawing up a mathematical model for the calculation (forecasting) of the thickness of a flame sprayed coating of powdered aluminium on S235JR steel. Experimental work was conducted according to a full central composite design at three levels. The thickness of the coatings made with combinations of input parameters of the procedure according to the experiment plan mentioned was measured in line with the ISO 2064 standard. A mathematical model was derived describing the dependence of the experimentally obtained thickness values on the input parameters of the procedure. The possibility of analysing the influence of the parameters upon the thickness for a certain combination of input parameters has been presented with the use of perturbation plots.     

Perturbation analysis of fuzzy linear systems

This paper deals with the perturbation analysis of fuzzy linear systems. Three cases of perturbation are considered: (a) the right hand side is perturbed while the coefficient matrix remains unchanged; (b) the coefficient matrix is perturbed while the right hand side remains unchanged, and (c) both the coefficient matrix and the right hand side are perturbed. For all of the three cases, the respective relative error bounds for solutions of fuzzy linear system are derived. The results are illustrated by numerical examples.     

Comparative study of variable size perturbation and observation maximum power point trackers for PV systems

Perturbation and observation (P&O) maximum power point tracking (MPPT) algorithms are common in photovoltaic (PV) systems due to its ease of implementation. However, operation with fixed size perturbations results in a trade-off between speed of response and maximum power yield in the steady-state. This paper discusses the use of Fuzzy logic and non-switching zone schemes for implementing variable size perturbations for improved transient and steady-state responses. The potential performance of four different P&O algorithms is investigated by means of simulations. Experimental results are then used to verify how the computational burden of each algorithm and the processing speed of a digital signal processor (DSP) affect the performance of each method in a prototype. The best performance is achieved with a new strategy called non-switching zones in the V_PV × I_PV plane. The power electronics converter operates with duty cycle (D) equal to 0 or 1, depending on which non-MPP region the system operates, pushing the operating point the fastest way possible towards the MPP region, for improved transient response. At the MPP region, a reduced Fuzzy P&O MPPT algorithm optimized for small variations around the MPP is used for reduced oscillations and increased power yield in the steady-state.     

Effect of asymmetric actuator and detector position on Coriolis flowmeter and measured phase shift

Coriolis flowmeters (CFM) are forced to vibrate by a periodic excitation usually applied midpipe through an electromagnetic actuator. From hands-on experience with industrial CFMs it appears, that the electromagnetic actuator has to be located as symmetric as possible. For CFM design and trouble-shooting it is of relevance to know how and if imperfections, related to the excitation location, influence the dynamic behavior of the vibrating fluid-conveying pipes employed in CFMs. A simple model of an imperfectly excited, simply supported, straight, single pipe CFM is investigated using a multiple time scaling perturbation analysis. The result is a simple analytical expression for the approximated phase shift, which offers a direct insight into how the location of the actuator influences the phase shift. It appears, that asymmetrical forcing combined with fluctuating pipe damping could be a factor contributing to lack of zero shift stability observed with some industrial CFMs. Tests of the approximated solution against results obtained by pure numerical analysis using Galerkin expansion show very good agreement. The effect of asymmetric detector positions is also investigated. Any asymmetry in the detectors position, e.g. due to manufacturing variations or improper handling of the CFM, induces a phase shift that leads to changes of the meter’s sensitivity, and could therefore result into erroneous measurements of the mass flow. This phase shift depends on the mass flow and does not contribute to a lacking zero-point stability. The validity of the hypotheses, which are assumed to be basically similar for more complicated geometries, e.g. bended and/or dual pipe CFMs, with or without multiple actuators, is suggested to be tested using laboratory experiments with purpose built non-ideal CFMs.