基于小波包变换和伪魏格纳分布的轴承故障诊断

将小波包变换理论和伪魏格纳分布应用于齿轮箱故障诊断中,结合实例对轴承的振动信号进行分析,结果表明:小波包变换能有效地提取各频段的高频成分,通过对提取的信号做伪魏格纳分布,结果能形象、直观地反映出轴承故障的时-频信息,而且对故障信息具有较强的判别能力。     

A novel signal feature extraction technology based on empirical wavelet transform and reverse dispersion entropy

Feature extraction is an important part of signal processing, which is significant for signal detection, classification, and recognition. The nonlinear dynamic analysis method can extract the nonlinear characteristics of signals and is widely used in different fields. Reverse dispersion entropy (RDE) proposed by us recently, as a nonlinear dynamic analysis method, has the advantages of fast computing speed and strong anti-noise ability, which is more suitable for measuring the complexity of signal than traditional permutation entropy (PE) and dispersion entropy (DE). Empirical wavelet transform (EWT), based on the theory of wavelet analysis, can decompose a complex non-stationary signal into a number of empirical wavelet functions (EWFs) with compact support set spectrum, which has better decomposition performance than empirical mode decomposition (EMD) and its improved algorithms. Considering the advantages of RDE and EWT, on the one hand, we introduce EWT into the field of underwater acoustic signal processing and fault diagnosis to improve the signal decomposition accuracy; on the other hand, we use RDE as the features of EWFs to improve the signal separability and stability. Finally, we propose a novel signal feature extraction technology based on EWT and RDE in this paper. Experimental results show that the proposed feature extraction technology can effectively extract the complexity features of actual signals. Moreover, it also has higher distinguishing ability for different types of signals than five latest feature extraction technologies.     

基于B样条小波的异常数据辨识

为解决靶场测量数据中系统误差引起的大量连续奇异数据的辨识难题,同时针对传统和目前国内外较先进的异常值识别方法的不足,提出了基于B样条小波的异常数据辨识。首先描述了异常值,然后分析了小波异常值识别原理和物理意义,构造了用于异常数据辨识的B样条小波分析方法。通过对不同情况仿真数据的计算分析,证明了该方法科学、合理,实现了测量数据异常值的辨识和重构。     

A branch‐and‐price algorithm for a targeting problem

In this paper, we consider a new weapon‐target allocation problem with the objective of minimizing the overall firing cost. The problem is formulated as a nonlinear integer programming model, but it can be transformed into a linear integer programming model. We present a branch‐and‐price algorithm for the problem employing the disaggregated formulation, which has exponentially many columns denoting the feasible allocations of weapon systems to each target. A greedy‐style heuristic is used to get some initial columns to start the column generation. A branching strategy compatible with the pricing problem is also proposed. Computational results using randomly generated data show this approach is promising for the targeting problem. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

Integrated capacity,demand, and production planning with subcontracting and overtime options

Models for integrated production and demand planning decisions can serve to improve a producer's ability to effectively match demand requirements with production capabilities. In contexts with price‐sensitive demands, economies of scale in production, and multiple capacity options, such integrated planning problems can quickly become complex. To address these complexities, this paper provides profit‐maximizing production planning models for determining optimal demand and internal production capacity levels under price‐sensitive deterministic demands, with subcontracting and overtime options. The models determine a producer's optimal price, production, inventory, subcontracting, overtime, and internal capacity levels, while accounting for production economies of scale and capacity costs through concave cost functions. We use polyhedral properties and dynamic programming techniques to provide polynomial‐time solution approaches for obtaining an optimal solution for this class of problems when the internal capacity level is time‐invariant. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

Modeling and analyzing multiple station baggage screening security system performance

In the aftermath of the tragic events of 11 September 2001, numerous changes have been made to aviation security policy and operations throughout the nation's airports. The allocation and utilization of checked baggage screening devices is a critical component in aviation security systems. This paper formulates problems that model multiple sets of flights originating from multiple stations (e.g., airports, terminals), where the objective is to optimize a baggage screening performance measure subject to a finite amount of resources. These measures include uncovered flight segments (UFS) and uncovered passenger segments (UPS). Three types of multiple station security problems are identified and their computational complexity is established. The problems are illustrated on two examples that use data extracted from the Official Airline Guide. The examples indicate that the problems can provide widely varying solutions based on the type of performance measure used and the restrictions imposed by the security device allocations. Moreover, the examples suggest that the allocations based on the UFS measure also provide reasonable solutions with respect to the UPS measure; however, the reverse may not be the case. This suggests that the UFS measure may provide more robust screening device allocations. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2005.     

基于分数傅立叶变换的图像隐藏技术

提出一种利用分数傅立叶变换实现图像隐藏的新方法。将多个不同图像的信息分别经不同阶的分数傅立叶变换后,记录在同一谱平面上,实现了图像的第一重隐藏。通过相位编码后,对谱平面进行另一次分数傅立叶变换,实现图像的第二重隐藏。在解密时,需要特定的分数阶及正确的解码相位才能再现不同的初始图像。提出的新方法用不同的分数阶实现多幅图频谱叠加的互不干扰,用相位编码使得两次的分数傅立叶变换互不干扰,随机设置多重密钥,且每重密钥都极其重要,使得破译的难度提高,因此图像加密的结果更加安全。     

基于整数小波变换的多光谱遥感图像压缩技术

在分析多光谱图像小波变换后系数特点的基础上,提出了一种基于整数小波变换的3维集合分裂嵌入块编码(3D SPECK)压缩方法。该方法将小波变换压缩技术中的零树编码推广到多光谱图像压缩中,采用整数小波变换去除空间冗余,对单波段图像,采用2D SPECK编码,对多波段图像,谱域上构成的小波矢量采用离散余弦变换(DCT)进行变换,对变换后的系数进行3D SPECK编码。实验结果表明,该方法硬件实现简单,编码解码时间快,对内存要求低。     

小波变换在电力系统谐波检测中的应用

将小波变换方法应用于电力系统谐波检测中,用仿真算例说明该方法具有一定的有效性和可行性;用不同的小波函数进行了基频分量提取,给出了误差比较结果,初步分析了小波变换用于谐波检测时产生误差的主要原因.     

基于LabVIEW的齿轮箱故障诊断

着重介绍了齿轮箱故障诊断系统的实现过程和设计思想,及通过虚拟仪器开发软件LabVIEW、小波变换和神经网络技术,来实现齿轮箱故障诊断系统的核心内容,最后通过实例验证了此设计的可行性。