图像压缩中的顺序组合最优匹配小波

小波变换是图像压缩中的一个重要工具。二维图像在进行压缩变换时,因变换后系数需要进行截短,以及小波与图像可能不是最优匹配,因此使得重构后的图像能量损失较大。为了减少重构后图像能量损失,本文提出了顺序组合最优匹配小波构造方法;通过Woman图像,构造该图像的顺序组合最优匹配小波,并用该小波对其图像进行处理,最后与其他一些方法进行比较处理结果。     

k‐version of finite element method in gas dynamics: higher‐order global differentiability numerical solutions

In this paper, we consider and examine alternate finite element computational strategies for time‐dependent Navier–Stokes equations describing high‐speed compressible flows with shocks in a viscous and conducting medium, with the ultimate objective of establishing the desired features of a general mathematical and computational framework for such initial value problems (IVP) in which: (a) the numerically computed solutions are in agreement with the physics of evolution described by the governing differential equations (GDEs) i.e. the IVP, (b) the solutions are admissible in the non‐discretized form of the GDEs in the pointwise sense (i.e. anywhere and everywhere) in the entire space–time domain, and hence in the integrated sense as well, (c) the numerical approximations progressively approach the same global differentiability in space and time as the theoretical solutions, (d) it is possible to time march the solutions (this is essential for efficiency as well as ensuring desired accuracy of the computed solution for the current increment of time, i.e. to minimize the error build up in the time marching process), (e) the computational process is unconditionally stable and non‐degenerate regardless of the choice of discretization, nature of approximations and their global differentiability and the dimensionless parameters influencing the physics of the process, (f) there are no issues of stability, CFL number limitations and (g) the mathematical and computational methodology is independent of the nature of the space–time differential operators. We consider one‐dimensional compressible flow in a viscous and conducting medium with shocks as model problems to illustrate various features of the general mathematical and computational framework used here and to demonstrate that the proposed framework is general and is applicable to all IVP. The Riemann shock tube with a single diaphragm serves as a model problem. The specific details presented in the paper discuss: (1) Choice of the form of the GDEs, i.e. strong form or weak form. (2) Various choices of variables. The paper establishes and considers density, velocity and temperature as variables of choice. (3) Details of the space–time least squares (LS) integral forms (meritorious over all others in all aspects) are presented and choice of approximation spaces are discussed. (4) In all numerical studies we consider a viscous and conducting medium with ideal gas law, however results are also presented for non‐conducting medium. Extension of this work to real gas models will be presented in a separate paper. It is worth noting that when the medium is viscous and conducting, the solutions of gas dynamics equations are analytic. (5) It is also significant to note that upwinding methods based on addition of artificial diffusion such as SUPG, SUPG/DC, SUPG/DC/LS and their many variations are neither needed nor used in this present work. (6) Numerical studies are aimed at resolving the localized details of the shock structure, i.e. shock relations, shock width, shock speed, etc. as well as the over all global behaviour of the solution in the entire space–time domain. (7) Numerical studies are presented for Riemann shock tube for high Mach number flows with special emphasis also on time accuracy of the evolution which is ensured by requiring that the approximations for each increment of time satisfy non‐discretized form of the GDEs in the pointwise sense, and hence in the integrated sense as well. (8) Comparisons are made with published results as well as theoretical solutions (when possible). It is established that space–time least squares processes are the only processes that yield variationally consistent space–time integral forms, and hence unconditionally non‐degenerate space–time computational processes, which when considered in higher‐order scalar product spaces provide the desired mathematical framework in which progressively higher‐order global differentiability solutions in space and time yield the same characteristics as the theoretical solutions of the IVP in all aspects. Copyright © 2006 John Wiley & Sons, Ltd.     

Estimating the Change Point of the Process Fraction Non‐conforming with a Monotonic Change Disturbance in SPC

Knowing when a process has changed would simplify the search for and identification of the special cause. In this paper, we propose a maximum‐likelihood estimator for the change point of the process fraction non‐conforming without requiring knowledge of the exact change type a priori. Instead, we assume the type of change present belongs to a family of monotonic changes. We compare the proposed change‐point estimator to the maximum‐likelihood estimator for the process change point derived under a simple step change assumption. We do this for a number of monotonic change types and following a signal from a binomial cumulative sum (CUSUM) control chart. We conclude that it is better to use the proposed change point estimator when the type of change present is only known to be monotonic. The results show that the proposed estimator provides process engineers with an accurate and useful estimate of the time of the process change regardless of the type of monotonic change that may be present. Copyright © 2006 John Wiley & Sons, Ltd.     

DIRECT ADAPTIVE CONTROL FOR NONLINEAR MATRIX SECOND‐ORDER SYSTEMS WITH TIME‐VARYING AND SIGN‐INDEFINITE DAMPING AND STIFFNESS OPERATORS

A direct adaptive control framework for a class of nonlinear matrix second‐order systems with time‐varying and sign‐indefinite damping and stiffness operators is developed. The proposed framework guarantees global asymptotic stability of the closed‐loop system states associated with the plant dynamics without requiring any knowledge of the system nonlinearities other than the assumption that they are continuous and bounded. The proposed adaptive control approach is used to design adaptive controllers for suppressing thermoacoustic oscillations in combustion chambers.     

UNKNOWN INPUTS OBSERVERS DESIGN FOR DELAY SYSTEMS

This paper concerns the design of functional, reduced and full order observers for linear time delay systems with unknown inputs. A new method generalizing those existing in the literature is presented for systems with unknown inputs, these unknown inputs are present in both the state and the measurement equations. Conditions for the existence of these observers are given and sufficient conditions for the stability independent of delays are derived using linear matrix‐inequality (LMI) formulation. The independent of internal delay and independent of delay cases are also presented. A numerical example is presented to illustrate our approach.     

Behavioral modeling of power amplifiers for wireless applications

In this paper, an improved empirical behavioral model for radio‐frequency power amplifiers (RF‐PAs) is presented. The model was implemented in a commercial nonlinear microwave simulator. It belongs to the category of bandpass PA models, which exhibits memory effects due to the low frequency dependence of bias and temperature. Additionally, it facilitates accurate and efficient system level simulations of RF‐PA large‐signal behaviors such as self‐bias, AM‐AM, AM‐PM, gain expansion effects, and intermodulation distortion (IMD) sweet‐spots. The model was validated using measurement data obtained from a commercial CDMA PA at 1.88 GHz. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

关于提高变频器调频速度的研究

本文介绍了作者的一项专利技术。对于需要比较快速、比较频繁地调整变频器频率应用场合,目前的通用变频器就很难满足这个需要,尤其是在大惯性负载上使用变频器时,须将升、降频（特别是降频）速度设置的比较慢,以适应由于惯性造成的电机转速的滞后。本专利技术克服上述传统变频器目前存在的缺陷,在传统变频器上增加比较简单并业已成熟的换相技术,为变频器的制造提供了一种新的附加技术。     

11/2维倒谱在滚动轴承故障诊断中的应用

从三阶累积量的概念出发,提出了1(1/2)维倒谱的概念,并从理论上推导出其能抑制噪声、提高信噪比.将其应用于实际的滚动轴承故障特征提取中,分析表明,与其他一般的信号处理方法相比1(1/2)维倒谱能有效地从复杂的信号成分中提取出特征信号来,且计算量小、精度高.     

Experimental and MD simulation of 3-dodecyloxypropanamine and 3-tetradecyloxypropylamine adsorbed onto quartz (1 0 1) surface

In this paper, two surfactants, 3-dodecyloxypropanamine (DOPA) and 3-tetradecyloxypropylamine (TOPA), were synthesized and used as collectors in the quartz micro-flotation in the laboratory. Micro-flotation tests, FT-IR, XPS measurements, and ab initio Molecular Dynamics (MD) simulations were conducted to research DOPA, TOPA, and dodecylamine (DDA)'s adsorption mechanisms onto quartz (1 0 1) surfaces. The results of micro-flotation show that the adsorption of DOPA and TOPA onto quartz surface is more robust than that of DDA. The zeta-potential result shows that the DOPA/TOPA was adsorbed on quartz through electrostatic attraction. Then, MD simulation adsorption models were built to compare the computational properties of the three surfactants, such as the radial distribution function, and the interaction energies between the collectors and the quartz cleavage surface. The interaction energies of surfactants (RNH₃⁺ or RNH₂) on the quartz surface explained why the pH range of DOPA/TOPA is wider than that of DDA. XPS analyses and MD simulations confirmed that DOPA bonded with the (1 0 1) surface of quartz through three types of hydrogen bonds between the NH₂ of DOPA and the O atom of quartz. The hydrogen bonds of type A and type C were the most likely type and more potent than those of type B.