小波分解法在钨极氩弧焊熔池面形重建中的应用

为了解决傅里叶变换轮廓术重建熔池三维面形遇到的频谱混叠困难,研究了二维小波变换原理,采用图像二维小波分解的方法对熔池图像进行多尺度分解,重构熔池的背景图像,滤除频域中的零频成分,解决了零频与基频的混叠问题。利用小波分解法结合傅里叶变换轮廓术较好地实现了基频信息的提取与熔池的表面重构,提高了傅里叶变换轮廓术的测量范围。

基于局部均值分解的信号非线性趋势项剔除方法及应用

本文提出了一种基于样条插值的局部均值分解(LMD)法剔除趋势项的途径,并研究了其在发动机瞬时转速信号处理中的应用。通过与常用的最小二乘法(LSM)和小波分解法(WM)进行比较,表明了基于样条插值的局部均值分解法在去除信号中趋势项的问题上,具有剔除与真实信号频谱重叠的趋势项的优势。这对提高发动机瞬时转速信号预处理精度具有重要意义。

考虑固液耦合的充液管道系统振动能量流研究

对固液耦合振动研究内容、研究现状,能量流研究方法以及固液耦合振动能量流研究进展进行了较为全面的论述,并对今后开展充液管道系统固液耦合振动研究、声传播及噪声控制的研究进行了展望.

呼兰河流域上游天然径流变化趋势及突变特征分析

鉴于呼兰河流域径流研究较少的问题,根据呼兰河流域上游铁力水文站1953~2014年天然径流资料,采用Db3小波分解法、Mann-Kendall法和R/S分析法分别研究了流域上游年径流量、月最小径流量的趋势性、突变性和持续性特征,并从气候变化和人类活动两方面定性讨论了径流发生变化的原因。结果表明,铁力气象站年降水量、铁力水文站年径流量变化特征一致,均呈不显著减少变化,未来将持续减少,突变点位于1965年;铁力水文站最小月径流量、铁力气象站春季月均最低气温变化特征一致,均呈不显著增加变化,未来将继续增加;降水变化是径流变化主因之一;春季月均最低气温升高会增加冰雪融水,加之各类水利工程建设的综合作用导致流域径流发生变化。研究成果可对合理开发利用呼兰河流域水资源起到一定积极作用。

高承台桩基无偏心竖向激励低应变测试方法研究

为了弥补传统低应变检测方法在识别带高承台的桩基完整性及桩长信息等方面的缺陷,提出了一种新型无偏心竖向激励方式以及一种桩身轴向多点速度响应行波分解法。进一步地,通过二维及三维有限元模型验证了该方法在识别带高承台的桩基完整性及桩长信息等方面的可行性。最后,对所提出的方法开展了如桩身尺寸、承台尺寸、传感器设置等一系列影响因素的参数分析研究。结果表明,通过本方法对原始的复杂速度响应进行数据处理后可以得到一桩底反射区清晰可辨的响应曲线,消除了上部结构复杂振动特性及环境高频噪声的影响,从而有效地预测了未知的桩长。该研究解决了现有无损检测方法局限性,对实际工程中带高承台桩基的完整性判断及桩长预测有一定的参考意义。

传感器安装偏差对功率流测试误差的影响分析

为分析传感器安装偏差对功率流测试误差的影响,将安装偏差分解为位置偏差和角度偏差两个部分,并分别基于互功率谱法和波分解法建立传感器安装偏差与功率流测试误差之间的数学模型。仿真分析结果表明:所建立的互功率谱法和波分解法功率流测试误差模型完全一致;位置偏差对功率流的影响由两个传感器位置偏差之差决定,角度偏差对功率流测试误差的影响与频率无关,但始终使得功率流向更小的方向变化,而总误差为两种安装偏差各自产生误差之积。

Exact Solutions of the Harry-Dym Equation

The aim of this paper is to generate exact travelling wave solutions of the Harry-Dym equation through the methods of Adomian decomposition, He＇s variational iteration, direct integration, and power series. We show that the two later methods are more successful than the two former to obtain more solutions of the equation.

All Single Traveling Wave Solutions to （3＋1）-Dimensional Nizhnok-Novikov-Veselov Equation

Using elementary integral method, a complete classification of all possible exact traveling wave solutions to （3＋1）-dimensional Nizhnok-Novikov-Veselov equation is given. Some solutions are new.

Geometric Mean Decomposition Based Hybrid Precoding for Millimeter-Wave Massive MIMO

Hybrid precoding can reduce the number of required radio frequency(RF)chains in millimeter-Wave(mmWave) massive MIMO systems. However, existing hybrid precoding based on singular value decomposition(SVD) requires the complicated bit allocation to match the different signal-to-noise-ratios(SNRs) of different sub-channels. In this paper,we propose a geometric mean decomposition(GMD)-based hybrid precoding to avoid the complicated bit allocation. Specifically,we seek a pair of analog and digital precoders sufficiently close to the unconstrained fully digital GMD precoder. To achieve this, we fix the analog precoder to design the digital precoder, and vice versa. The analog precoder is designed based on the orthogonal matching pursuit(OMP) algorithm, while GMD is used to obtain the digital precoder. Simulations show that the proposed GMD-based hybrid precoding achieves better performance than the conventional SVD-based hybrid precoding with only a slight increase in complexity.

ANALYSIS OF WAVEGUIDE PROBLEMS USING A RELAXED ITERATIVE DOMAIN DECOMPOSITION METHOD COMBINED WITH MULTIFRONTAL ALGORITHM

In this paper, an absorbing Fictitious Boundary Condition (FBC) is presented to generate an iterative Domain Decomposition Method (DDM) for analyzing waveguide problems.The relaxed algorithm is introduced to improve the iterative convergence. And the matrix equations are solved using the multifrontal algorithm. The resulting CPU time is greatly reduced.Finally, a number of numerical examples are given to illustrate its accuracy and efficiency.

Vibration-based feature extraction of determining dynamic characteristic for engine block low vibration design

In order to maintain vibration performances within the limits of the design, a vibration-based feature extraction method for dynamic characteristic using empirical mode decomposition （EMD） and wavelet analysis was proposed. The proposed method was verified experimentally and numerically by implementing the scheme on engine block. In the implementation process, the following steps were identified to be important： 1） EMD technique in order to solve the feature extraction of vibration signals; 2） Vibration measurement for the purpose of confirming the structural weak regions of engine block in experiment; 3） Finite element modeling for the purpose of determining dynamic characteristic in time region and frequency region to affirm the comparability of response character corresponding to improvement schemes; 4） Adopting a feature index oflMF for structural improvement based on EMD and wavelet analysis. The obtained results show that IMF of signal is more sensitive to response character corresponding to improvement schemes. Finally, examination of the results confirms that the proposed vibration-based feature extraction method is very robust, and focuses on the relative merits of modification and full-scale structural optimization of engine, together with the creation of new low-vibration designs.

Wind speed forecasting based on wavelet decomposition and wavelet neural networks optimized by the Cuckoo search algorithm

Wind speed forecasting is of great importance for wind farm management and plays an important role in grid integration. Wind speed is volatile in nature and therefore it is difficult to predict with a single model. In this study, three hybrid multi-step wind speed forecasting models are developed and compared — with each other and with earlier proposed wind speed forecasting models. The three models are based on wavelet decomposition(WD), the Cuckoo search(CS) optimization algorithm, and a wavelet neural network(WNN). They are referred to as CS-WD-ANN(artificial neural network), CS-WNN, and CS-WD-WNN, respectively. Wind speed data from two wind farms located in Shandong, eastern China, are used in this study. The simulation result indicates that CS-WD-WNN outperforms the other two models, with minimum statistical errors. Comparison with earlier models shows that CS-WD-WNN still performs best, with the smallest statistical errors. The employment of the CS optimization algorithm in the models shows improvement compared with the earlier models.

Solitary Wave and Periodic Wave Solutions for the Relativistic Toda Lattices

In this work, an adaptation of the tanh/tan-method that is discussed usually in the nonlinear partial differential equations is presented to solve nonlinear polynomial differential-difference equations. As a concrete example,several solitary wave and periodic wave solutions for the chain which is related to the relativistic Toda lattice are derived.Some systems of the differential-difference equations that can be solved using our approach are listed and a discussion is given in conclusion.

Homogenous Balance Method and Exact Analytical Solutions for Whitham-Broer-Kaup Equations in Shallow Water

Based on the homogenous balance method and with the help of mathematica, the Backlund transformation and the transfer heat equation are derived. Analyzing the heat-transfer equation, the multiple soliton solutions and other exact analytical solution for Whitham-Broer-Kaup equations(WBK) are derived. These solutions contain Fan's, Xie's and Yan's results and other new types of analytical solutions, such as rational function solutions and periodic solutions. The method can also be applied to solve more nonlinear differential equations.

A blind watermarking algorithm based on DWT and SVD

This paper presents a new digital image blind watermarking algorithm based on combination of discrete wavelet transform （DWT） and singular value decomposition （SVD）. First of all, we make wavelet decomposition for the original image and divide the acquired low frequency sub-band into blocks. Then we make singular value decomposition for each block and embed the watermark information in the largest singular value by quantitative method. The watermark can be extracted without the original image. The experimental results show that the algorithm has a good imperceptibility and robustness.

Solitary Wave Solutions of Discrete Complex Ginzburg-Landau Equation by Modified Adomian Decomposition Method

In this paper, exact and numerical solutions are calculated for discrete complex Ginzburg-Landau equation with initial condition by considering the modified Adomian decomposition method （mADM）, which is an efficient method and does not need linearization, weak nonlinearity assumptions or perturbation theory. The numerical solutions are also compared with their corresponding analytical solutions. It is shown that a very good approximation is achieved with the analytical solutions. Finally, the modulational instability is investigated and the corresponding condition is given.

Analytical Results of Eigenstates and Eigenenergies for Three Kinds of Models Describing N-mode Multiphoton Process

We obtain. the exact analytical results of all the eigenvalues and eigenstates for three kinds of models describing N-mode multiphoton process without using the assumption of the Bethe ansatz. The exact analytical results of all the eigenstates and eigenvalues are in terms of a parameter lambda for three kinds of models describing N-mode multiphoton process. The parameter is shown to be determined by the roots of a polynomial and is solvable analytically or numerically. Moreover, these three kinds of models can be processed with the same procedure.

Perturbative Painlevé Analysis of General KdV System and Its Exact Soliton Solutions

Using the standard Painlevé analysis and the perturbative method, the Painlevé test for the logarithmic branch is investigated. Nine arbitrary functions are obtained and the Baecklund transformation of the logarithmic branch is given. Using the new type Baecklund transformation, many exact solutions are obtained.

Analysis of Infrared Divergence in OZI-Forbidden Decays of Orthoquarkonia

It is interesting to investigate the OZI-forbidden decays of orthoquarkoknium, J/ψ→γπ^0（γη,γη′）, J/ψ→π^＋π^-（π^0π^0）. At first glance, there is infrared divergence in the above processes. In this work, to clear the mist we use the factorization method with the light cone wavefunction of the final state light meson. We prove straightforwardly that the infrared divergence can be eliminated completely.

Exciting Forces for a Wave Energy Device Consisting of a Pair of Coaxial Cylinders in Water of Finite Depth

Two coaxial vertical cylinders-one is a riding hollow cylinder and the other a solid cylinder of greater radius at some distance above an impermeable horizontal bottom,were considered.This problem of diffraction by these two cylinders,which were considered as idealization of a buoy and a circular plate,can be considered as a wave energy device.The wave energy that is created and transferred by this device can be appropriately used in many applications in lieu of conventional energy.Method of separation of variables was used to obtain the analytical expressions for the diffracted potentials in four clearly identified regions.By applying the appropriate matching conditions along the three virtual boundaries between the regions,a system of linear equations was obtained,which was solved for the unknown coefficients.The potentials allowed us to obtain the exciting forces acting on both cylinders.Sets of exciting forces were obtained for different radii of the cylinders and for different gaps between the cylinders.It was observed that changes in radius and the gap had significant effect on the forces.It was found that mostly the exciting forces were significant only at lower frequencies.The exciting forces almost vanished at higher frequencies.The problem was also investigated for the base case of no plate arrangement,i.e.,the case having only the floating cylinder tethered to the sea-bed.Comparison of forces for both arrangements was carried out.In order to take care of the radiation of the cylinders due to surge motion,the corresponding added mass and the damping coefficients for both cylinders were also computed.All the results were depicted graphically and compared with available results.