一种基于多分形奇异谱的噪声奇异性分析新方法

在介绍了噪声中的奇异性以及其全局奇异性的表征方法——多分形奇异谱的基础上,提出并实现了一种基于子波分解模极大的计算噪声多分形奇异谱的方法,通过对仿真信号验证,证明了该方法准确可靠。在对实测信号分析中,也发现该方法得到的多分形奇异谱比功率谱更能充分刻画噪声信号的特性。     

大坝水平位移监测数据的小波变换去噪处理

将实际观测到的一组大坝水平位移监测数据作为通常意义下的时序信号，并对其进行小波变换分析。根据噪声和有用信号的小波变换系数模极大值在不同分解尺度上的传播特点，提出了根据模极大值的传播规律来区别噪声和有用信号的方法，并给出了具体的算法和计算程序。对模拟数据和实测数据的处理结果表明，基于小波分解模极大值的去噪方法能够有效剔除土木工程变形监测数据中的噪声，识别被噪声湮没的有用信号。     

Characteristics of pulsed photo-stimulated luminescence and thermoluminescence for the identification of gamma irradiated poultry eggs

Pulsed photo-stimulated luminescence (PPSL) is a simple screening method that can be employed qualitatively at the spot for the detection of eggs treated with ionizing radiation.Due to the variations in the results during storage,the eggs of ostrich,duck,hen,and quail were irradiated to doses of 0,1,2,and 3 kGy.Most of the samples were incorrectly identified during storage after four months of irradiation.Thermoluminescence (TL) technique was also tried by using egg shells in order to confirm the irradiation treatment in eggs.TL glow curves were recorded between the temperatures 50℃to 400℃at the rate of 5°/s for all the control and irradiated samples.On the basis of integrated areas of first glow curves (TL1),the glow curve ratios (TL1/TL2) and the shapes of maxima of TL1, the irradiation treatment of all the eggs was confirmed.Furthermore,the presence of calcite and aragonite minerals that cause the TL signal in the egg shells were studied using X-ray diffraction spectrometry.     

营养因子对大杯伞胞外多糖的影响

以胞外多糖含量为指标对大杯伞产胞外多糖液体培养基组成进行了优化,结果表明,较适宜的碳源是果糖、麦芽糖、蔗糖;较适宜的氮源是NH4NO3、蛋白胨、KNO3.通过正交试验确定了产胞外多糖的最优液体培养基蔗糖2%,KNO30.3%,KH2PO40.2%,MgSO40.1%.     

基于小波分析和神经网络的井下电缆故障测距方法

针对现有的井下电缆故障测距方法存在可靠性差、精度低的问题,介绍了一种基于小波分析理论和神经网络的井下电缆故障测距方法,并比较了BP神经网络和RBF神经网络用于该方法的测距性能。该故障测距方法采用3次B样条半正交小波对暂态零序电流信号进行小波变换,得到特定频带内的暂态零序电流模极大值,并将该模极大值作为神经网络的输入信号,根据模极大值与故障点位置的映射关系实现故障定位。仿真结果表明,该故障测距方法能够较好地进行井下电缆故障测距,且RBF神经网络的测距误差及训练速度均优于BP神经网络。     

一种基于小波分析的网络流量异常检测与定位方法

根据网络流量在大时间尺度上的自相似性,以及在小时间尺度上异常流量、Lipschitz正则性与小波变换模极大值三者之间的关系,提出基于小波分析的网络流量异常检测方法.设计了采用该方法检测网络流量异常的模型,解决了方法实现过程中小波选择、模极大值曲线衰减判断、Hurst指数与Lipschitz指数求解等一些关键问题.实验表明,提出的方法能够较好的发现网络流量异常事件并定位异常发生时刻.     

双极HVDC输电线路行波故障定位

为准确定位双极HVDC输电线路故障,介绍了基于小波模极大值理论的双端D型行波故障测距方法及该方法在双极HVDC输电系统中的应用并用PSCAD和MATLAB软件仿真分析双极HVDC系统,得到故障点初始行波波头分别到达整流侧母线和逆变侧母线的时刻,从而算出故障点到达两侧母线的距离,完成故障定位。该结果表明,小波变换的模极大值能够刻画出故障行波信号的奇异点和奇异性,用小波变换提取高频暂态信号可准确找出故障极线路,识别出故障极初始电流行波的波头,实现双极HVDC输电线路高度精确的故障定位。     

模极大值均方根比在配网暂态接地故障选线中的应用研究

针对小电流接地系统单相接地故障暂态量电流特征,给出一种以零模电流模极大值均方根比值为判据的接地故障暂态选线方法。利用小波包分析和奇异性检测理论对故障线路与非故障线路零模暂态电流奇异性差异进行分析,计算选线频带内各线路零模电流的模极大值序列及模极大值的均方根值,并根据均方根比值确定故障线路。理论分析和EMTP大量仿真试验结果表明,该方法能适应工程应用中可能存在的影响因素,具有灵敏度高、自适应能力强、选线准确等特点。     

Impact of tidal-stream arrays in relation to the natural variability of sedimentary processes

Tidal Energy Converter (TEC) arrays are expected to reduce tidal current speeds locally, thus impacting sediment processes, even when positioned above bedrock, as well as having potential impacts to nearby offshore sand banks. Furthermore, the tidal dissipation at potential TEC sites can produce high suspended sediment concentrations (turbidity maxima) which are important for biological productivity. Yet few impact assessments of potential TEC sites have looked closely at sediment dynamics beyond local scouring issues. It is therefore important to understand to what extent exploitation of the tidal energy resource will affect sedimentary processes, and the scale of this impact is here assessed in relation to natural variability. At one such site in the Irish Sea that is highly attractive for the deployment of TEC arrays, we collect measurements of sediment type and bathymetry, apply a high resolution unstructured morphodynamic model, and a spectral wave model in order to quantify natural variability due to tidal and wave conditions. We then simulate the impacts of tidal-stream energy extraction using the morphodynamic model. Our results suggest that the sedimentary impacts of ‘first generation’ TEC arrays (i.e. less than 50 MW), at this site, are within the bounds of natural variability and are, therefore, not considered detrimental to the local environment. Yet we highlight potential environmental issues and demonstrate how impact assessments at other sites could be investigated.     

基于小波变换去噪的相关功耗分析攻击研究与实现

为了提高功耗分析攻击效率,减少噪声影响,研究了小波变换去噪对功耗攻击的影响以及相关功耗分析（correlation power analysis,CPA）攻击的相关系数与攻击效果的关系,提出使用平移不变量小波法与小波模极大值法对功耗曲线进行去噪预处理。该方法使用卡尔曼滤波法、小波模极大值法与平移不变量小波法对功耗曲线进行去噪预处理,再对原始数据及去噪后数据分别进行CPA。实验结果显示,与原始数据相比,使用平移不变量小波法改进的CPA相关系数比仅使用CPA提高了165%,比卡尔曼滤波法提高了31.4%,比小波模极大值法相关系数提高了26.4%,同时攻击成功所需要的功耗曲线减少了92%。实验结果表明使用平移不变量小波法改进的相关功耗分析攻击效果最好。