基于音频内容的混合域脆弱水印算法

提出一种用于内容认证的脆弱音频水印算法.与以往的脆弱音频水印算法相比,不采用二值图像作为脆弱水印,而是基于音频内容,利用奇异值分解生成脆弱水印.水印嵌入在离散小波变换和离散余弦变换构成的混合域.仿真实验表明,该算法具有很好的不可感知性,并且对有损压缩、添加噪声、重量化等操作具有很强的敏感性,同时能够对替换等恶意篡改做出报警并确定篡改位置.     

格区间值Fuzzy集的分解定理(Ⅰ)

对格区间值Fuzzy集作了进一步的研究,分别给出了[λ1,λ2]、(λ1,λ2]、[λ1,λ2)、(λ1,λ2)上的下截集、上截集、下重截集和上重截集的新的定义及一种新的闭区间与格区间值Fuzzy集的运算,并给出了与此相应的四条重要的分解定理.     

Application of an improved EEMD method in bearing fault diagnosis of induction motors北大核心CSCD

[Objective]In order to overcome the disadvantages of the traditional ensemble empirical mode decomposition (EEMD) method in selecting parameters (integration time and white noise amplitude coefficient) based on experience, and reduce the cost of calculation time, a fast ensemble empirical mode decomposition (FEEMD) method is used to extract the characteristic frequency. [Method]By changing the distribution density of the added white noise, different signal envelopes can be obtained. Furthermore, we can identify the optimal envelope by finding the optimal search window width of the moving mean filter, thereby avoiding the defect of EEMD selecting parameters by experience. At the same time, after the abnormal component in the signal is decomposed, the residual component can be decomposed by EMD to further save the calculation time cost. Finally, the method is combined with Hilbert envelope demodulation technology and applied to the fault characteristic frequency diagnosis of the bearing inner ring of an asynchronous motor. [Results]As the results show, compared with the traditional EEMD method, FEEMD can extract the fault frequency more efficiently. [Conclusion]FEEMD overcomes the disadvantages of the traditional EEMD method in selecting parameters based on experience and shortens the calculation time. As such, it can be effectively applied in bearing fault frequency extraction experiments. © The Author(s) 2022.     

Comparison of road freight transport trends in Europe. Coupling and decoupling factors from an Input–Output structural decomposition analysis

Decoupling road freight transport from economic growth has been acknowledged by the European Union as a key means to improving sustainability. It is therefore important to identify both the coupling and decoupling drivers of road freight transport demand in order to determine possible factors that may contribute to reduce road transport in the future without curbing economic development. This research proposes an Input–Output (IO) structural decomposition analysis (SDA) to explain road freight transport in terms of a set of key factors that have strongly influenced road freight demand in recent decades in European countries—such as economic growth, economic structure and the evolution of road transport intensity (including improvements in both supply and transport systems). This methodological approach allows us to quantify and compare their contribution in different European countries to either increase or decrease road freight transport demand. The empirical basis for this analysis is a dataset of nine European countries which have IO tables and road transport data available from 2000 to 2007, comprising data on domestic production, imports and exports as well as tonne-kms for 11 types of commodity classes. The results show that, as a whole, aggregate road transport demand has grown—driven mainly by economic activity—but this growth has been strongly curbed in some countries by changes in road freight transport intensity and moderately by the dematerialization of the economy. International transport has been also proven to be a key factor driving road freight transport volumes. Moreover, the increased penetration of foreign operators in national haulage markets appears to have reinforced the final decoupling levels observed in some cases.     

THEORY AND APPLICATION OF M-BAND WAVELET TRANSFORM

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Model and a solution algorithm for the dynamic resource allocation problem for large-scale transportation network evacuation

Allocating movable resources dynamically enables evacuation management agencies to improve evacuation system performance in both the spatial and temporal dimensions. This study proposes a mixed integer linear program (MILP) model to address the dynamic resource allocation problem for transportation evacuation planning on large-scale networks. The proposed model is built on the earliest arrival flow formulation that significantly reduces problem size. A set of binary variables, specifically, the beginning and the ending time of resource allocation at a location, enable a strong formulation with tight constraints. A solution algorithm is developed to solve for an optimal solution on large-scale network applications by adopting Benders decomposition. In this algorithm, the MILP model is decomposed into two sub-problems. The first sub-problem, called the restricted master problem, identifies a feasible dynamic resource allocation plan. The second sub-problem, called the auxiliary problem, models dynamic traffic assignment in the evacuation network given a resource allocation plan. A numerical study is performed on the Dallas–Fort Worth network. The results show that the Benders decomposition algorithm can solve an optimal solution efficiently on a large-scale network.     

到球面上的四维非齐次双调和映射连续性

对到球面上的四维非齐次双调和映射,本文根据球面的几何结构和四维Lorentz空间的特殊性,得到了在Lorentz空间的估计式,从而得到其弱解的连续性结果.     

Scattering of surface water waves involving semi-infinite floating elastic plates on water of finite depth

Two problems of scattering of surface water waves involving a semi-infinite elastic plate and a pair of semi-infinite elastic plates,separated by a gap of finite width,floating horizontally on water of finite depth,are investigated in the present work for a two-dimensional time-harmonic case.Within the frame of linear water wave theory,the solutions of the two boundary value problems under consideration have been represented in the forms of eigenfunction expansions.Approximate values of the reflection and transmission coefficients are obtained by solving an over-determined system of linear algebraic equations in each problem.In both the problems,the method of least squares as well as the singular value decomposition have been employed and tables of numerical values of the reflection and transmission coefficients are presented for specific choices of the parameters for modelling the elastic plates.Our main aim is to check the energy balance relation in each problem which plays a very important role in the present approach of solutions of mixed boundary value problems involving Laplace equations.The main advantage of the present approach of solutions is that the results for the values of reflection and transmission coefficients obtained by using both the methods are found to satisfy the energy-balance relations associated with the respective scattering problems under consideration.The absolute values of the reflection and transmission coefficients are presented graphically against different values of the wave numbers.     

车辆悬挂弹簧故障检测的能量传递特性比较法

利用弹簧刚度对悬挂传递函数的频移特性,提出一种车辆悬挂弹簧故障动态检测的新方法.对悬挂弹簧安装处的车体和构架垂向振动加速度信号分别进行7层谐波小波包分解,计算了8个低尺度的能量,在同一尺度上,将车体和构架的加速度能量相除得到悬挂的尺度能量传递特性,提出相邻时段对应悬挂尺度能量传递特性的比较方法,进行悬挂弹簧的故障检测.检测结果表明:当悬挂弹簧刚度蜕变时,其传递特性向高尺度变化,与检测机理分析得出的传递特性向低频率变化的分析结论一致,同时能够检测刚度蜕变10％的悬挂故障,因此,该方法可靠性高,具有一定的工程适应性.     

产业转移背景下西部运输需求的完全分解模型

研究西部综合运输系统需求驱动因素,将产业转移因素考虑在内,对原有包含三大因素的完全分解模型进行改进,构建包含经济总量、运输需求强度、产业转移和产业结构整体变动等四大因素的完全分解模型,根据2002—2015年统计数据对西部地区综合运输系统需求进行实例计算.研究结果表明,经济总量增长是西部综合运输系统需求增长的主要原因,随着经济增速放缓,产业转移促进政策的出台,运输需求强度变化和产业转移的影响逐渐显著.在产业转移背景下,西部地区应该根据产业转移发展态势,有针对性地做好综合运输系统布局,创造更好的条件承接产业转移.