Applied Mechanics and Materials Vols. 321-324

Abstract: Sparse signal recovery is a hot topic in the fields of optimization theory and signal processing. Two main algorithmic approaches, i.e. greedy pursuit algorithms and convex relaxation algorithms have been extensively used to solve this problem. However, these algorithms cannot guarantee to find the global optimum solution, and then they perform poorly when the sparsity level is relatively large. Based on the simulated annealing algorithm and greedy pursuit algorithms, we propose a novel algorithm on solving the sparse recovery problem. Numerical simulations show that the proposed algorithm has very good recovery performance.

Abstract: Blind source separation (BSS) which separate the unknown sources from the observed signals is a new signal processing technique. The most methods for solving this problem rely on assumptions of independence or uncorrelation of source signals at least. However, the observed signal is always interfered by signals with common frequency in the rotating machine, and difficult to be separated by the conventional BSS method. In this paper, it is proved that the source signals with common frequencies are correlative, and the separating error brought by the cross-correlation of the source signals is analyzed. A new separating method for the correlated source signals with frequency overlapping is presented and it is successfully applied to separate the monitoring signals of rotor test stand.

Abstract: In this paper, the technique of distributed arithmetic (DA) and digital down conversion (DDC) are described. Then, an efficient wideband DDC based on polyphase structure with intermediate frequency (IF) bandpass sampling is presented. An optimized distributed arithmetic is used for saving the FPGA multiplier consumption. A design example is given and the FPGA resource consumption saving is discussed also. The corresponding test results demonstrate the effectiveness of the proposed DDC design using distributed arithmetic.

Abstract: In this paper, the principles of digital beamforming (DBF) and farrow structure are presented. Sum-of-powers-of-two (SOPOT) and cut-set retiming are used for saving the FPGA multiplier consumption and improving the running speed of farrow structure. A design example is given and the FPGA resource consumption saving is discussed also. The corresponding test results demonstrate the effectiveness of the fractional delay. With the fractional delay, it’s easy to realize wideband beam steering and digital beam forming.

Abstract: The bonding quality of composite materials have a critical influence on the quality of the product in modern industry, while the current technology can only make judgments on bonding and de-bonding instead of quantitative evaluation of different de-bonding degrees. We present HHT method to extract features of echo signals used for quantitative recognition of bonding quality of thin plates. For the non-stationary characteristic of the ultrasonic echo signal, empirical mode decomposition(EMD) and ensemble empirical mode decomposition(EEMD) are put forward to decompose the signal and calculate its energy torque. The HHT method highlights the time-frequency performance of echo signals effectively. The simulated signals verify that EEMD has more excellent decomposition performance than EMD, that is, EEMD diminishes the mode mixing to some extent generated from EMD decomposition.

Abstract: Mechanical engineering is a discipline of engineering that applies the principles of physics and materials science for analysis, design, manufacturing, and maintenance of mechanical systems. In this work, the notion of matrix-valued multiresolution analysis of space is introduced. A method for constructing orthogonal matrix-valued ternary wavelet packs is developed and their properties are discussed by means of time-frequency analysis method, matrix theory and functional analysis method. Three orthogonality formulas concerning these wavelet packets are provided. Finally, new orthonormal wavelet pack bases of space are obtained by constructing a series of subspaces of orthogonal matrix-valued wavelet packets.

Abstract: This paper presents synthesis of acoustic-emission (AE) wave propagation in multi-layer materials and simulation of AE wave responses at free surface. In particular, the AE source is modelled as an arbitrary-orientation dislocation over an inclined-to-surface fault within one layer or at the layer-to-layer interface, while the materials are assumed as multi-layer media, each of which is homogeneous, isotropic and linearly elastic. With the use of the integral transformation approach, the three-dimensional wave propagation in the materials is solved in transformed or frequency-wavenumber domain. Subsequently, a closed-form solution for wave responses at free surface is found, which can then be converted in time-space domain. Numerical examples are finally provided for illustration.

Abstract: For metallurgical industry perceptual load fluctuations large, and distribution station bus power factor low, and power loss high problems, based on reactive power compensation principle of apparent power does not variable, and used SVC structure forms, has made sectional type compensation control mode, and based on power factor of closed-loop control method, has researched the dynamic reactive power compensation device, by the check of practical run, the feasibility has been proved of the control method, and it has a clear compensation effect and wide practical range and other outstanding features.

Abstract: In this paper, it describes a DSP-based TMS320F28335 high-precision temperature control systems and explains its construction and principle. ADC which is integrated within DSP processes the collect temperature and double-controller algorithm controls the PWM output, the temperature can be set faster and more accurate. Simulation obtains two controller output stability, regulation faster, and getting a good robustness.

Abstract: Recent years, traditional radiate passive power distribution will become an active power with many medium or small power sources and loads, when distributed generation by new energy (such as wind power or photovoltaic power) are connected to power grid more and more. This change of power distribution brings large harm to security of power grid. This paper proposed a micro-grid system without inverse-power-flow based on distributed generation, which center controller and load controller are deployed, and distribution powers, loads and load controllers are partitioned into different domains connected to micro-grid by controllable switch. The function of main units of micro-grid is discussed; as well as the operation strategy of micro grid based on distributed generation is studied. Finally, the experiment results show the feasibility of the proposed micro-grid system.