Calculation of Mass Concrete Temperature Containing Cooling Water Pipe Based on Substructure and Iteration Algorithm

Mathematical physics equations are often utilized to describe physical phenomena in various fields of science and engineering.One such equation is the Fourier equation,which is a commonly used and effective method for evaluating the effectiveness of temperature control measures for mass concrete.One important measure for temperature control in mass concrete is the use of cooling water pipes.However,the mismatch of grids between large-scale concrete models and small-scale cooling pipe models can result in a significant waste of calculation time when using the finite element method.Moreover,the temperature of the water in the cooling pipe needs to be iteratively calculated during the thermal transfer process.The substructure method can effectively solve this problem,and it has been validated by scholars.The Abaqus/Python secondary development technology provides engineers with enough flexibility to combine the substructure method with an iteration algorithm,which enables the creation of a parametric modeling calculation for cooling water pipes.This paper proposes such a method,which involves iterating the water pipe boundary and establishing the water pipe unit substructure to numerically simulate the concrete temperature field that contains a cooling water pipe.To verify the feasibility and accuracy of the proposed method,two classic numerical examples were analyzed.The results showed that this method has good applicability in cooling pipe calculations.When the value of the iteration parameterαis 0.4,the boundary temperature of the cooling water pipes can meet the accuracy requirements after 4∼5 iterations,effectively improving the computational efficiency.Overall,this approach provides a useful tool for engineers to analyze the temperature control measures accurately and efficiently for mass concrete,such as cooling water pipes,using Abaqus/Python secondary development.

Identification of Lubricating Oil Additives Using XGBoost and Ant Colony Optimization Algorithms

To address the problem of identifying multiple types of additives in lubricating oil,a method based on midinfrared spectral band selection using the eXtreme Gradient Boosting(XGBoost)algorithm combined with the ant colony optimization(ACO)algorithm is proposed.The XGBoost algorithm was used to train and test three additives,T534(alkyl diphenylamine),T308(isooctyl acid thiophospholipid octadecylamine),and T306(trimethylphenol phosphate),separately,in order to screen for the optimal combination of spectral bands for each additive.The ACO algorithm was used to optimize the parameters of the XGBoost algorithm to improve the identification accuracy.During this process,the support vector machine(SVM)and hybrid bat algorithms(HBA)were included as a comparison,generating four models:ACO-XGBoost,ACO-SVM,HBA-XGboost,and HBA-SVM.The results showed that all four models could identify the three additives efficiently,with the ACO-XGBoost model achieving 100%recognition of all three additives.In addition,the generalizability of the ACO-XGBoost model was further demonstrated by predicting a lubricating oil containing the three additives prepared in our laboratory and a collected sample of commercial oil currently in use。

二阶Radon-Fourier变换与遗传算法结合的快速相参积累算法

针对匀加速运动的高速目标,可以用二阶Radon-Fourier变换(Second-order Radon-Fourier Transform,SRFT)完成对回波信号的相参积累。SRFT算法的原理是通过“速度-加速度”联合搜索来实现目标的运动参数估计,其计算量较大,不满足实时检测的需求。针对这个问题,提出一种基于遗传算法(Genetic Algorithm,GA)的快速实现方法。首先对运动参数集进行编码,设置初始群体;然后通过遗传算法对群体更新迭代,使其能够自发快速地逼近全局最优解,减少不必要的搜索路径;最终快速实现待检测目标的相参积累。仿真结果表明,在保证检测性能的前提下,算法计算量得到有效改善,运算次数减少大约一个量级。

基于Fourier拟合的光伏跟踪系统设计

[目的]为提高光伏支架的发电效率,以基于Fourier拟合算法的视日运动轨迹光伏跟踪器为研究设计对象。[方法]借助MATLAB分析了传统视日运动轨迹算法的跟踪精度情况,更进一步地在此基础上提出了精度更优的8阶傅里叶拟合视日运动轨迹跟踪算法,并结合GNSS定位技术,得出太阳实时运行轨迹。系统设计以STM32单片机作为微处理器,采用6轴加速度传感器,通过重力矢量在其轴上的投影确定光伏跟踪支架的实时倾斜度,以此二者建立跟踪支架三维运行模型,通过分析太阳光线在支架上的余弦效应即可得到电机需要运行的动作角。同时为解决晨昏时刻光伏组件间的阴影遮挡问题,系统增加逆跟踪算法。并考虑到大规模机组的应用,提出主从电机同步控制策略。[结果]傅-2里叶拟合算法拥有更高的跟踪精度,精度可达到10数量级,高于传统算法一个数量级。同时采用逆跟踪技术可节约24.3%光伏阵列用地面积,大幅提高了土地利用率。[结论]本研究采用更为精准的视日运动轨迹跟踪模型,较好地解决了太阳辐射利用的余弦效应,提升了电站的发电效率,实现了安全高效绿色能源体系的建设,促进了我国“双碳”目标的推进与达成。

IMPROVED FOURIER ALGORITHM FOR CORRECTING POWER SYSTEM FREQUENCY DEVIATION

On the basis of high precision requirement for input signals in the power system protection and control system,this paper,only for the influence of power system frequency deviation on extracting fundamental harmonic,studies the amplitude error of Fourier algorithm,presents a method of correcting frequency deviation,and further derives the formulas of improved Fourier algorithm.The simulation results verified the effectiveness of the algorithm,it not only can greatly weaken the influence of frequency deviation,but also increase the precision of the power system protection and control.As a result the study in this paper has practical application value.

Fast Fourier single-pixel imaging based on Sierra–Lite dithering algorithm

The single-pixel imaging(SPI) technique is able to capture two-dimensional(2 D) images without conventional array sensors by using a photodiode. As a novel scheme, Fourier single-pixel imaging(FSI) has been proven capable of reconstructing high-quality images. Due to the fact that the Fourier basis patterns(also known as grayscale sinusoidal patterns)cannot be well displayed on the digital micromirror device(DMD), a fast FSI system is proposed to solve this problem by binarizing Fourier pattern through a dithering algorithm. However, the traditional dithering algorithm leads to low quality as the extra noise is inevitably induced in the reconstructed images. In this paper, we report a better dithering algorithm to binarize Fourier pattern, which utilizes the Sierra–Lite kernel function by a serpentine scanning method. Numerical simulation and experiment demonstrate that the proposed algorithm is able to achieve higher quality under different sampling ratios.

Anti-aliasing nonstationary signals detecion algorithm based on interpolation in the frequency domain using the short time Fourier transform

To eliminate the aliasing that appeared during the measurement of multi-components nonstationary signals, a novel kind of anti-aliasing algorithm based on the short time Fourier transform （STFT） is brought forward. First the physical essence of aliasing that occurs is analyzed; second the interpolation algorithm model is setup based on the Hamming window; then the fast implementation of the algorithm using the Newton iteration method is given. Using the numerical simulation the feasibility of algorithm is validated. Finally, the electrical circuit experiment shows the practicality of the algorithm in the electrical engineering.

Adaptive split-step Fourier method for simulating ultrashort laser pulse propagation in photonic crystal fibres

In this paper, the generalized nonlinear Schrodinger equation （GNLSE） is solved by an adaptive split-step Fourier method （ASSFM）. It is found that ASSFM must be used to solve GNLSE to ensure precision when the soliton selffrequency shift is remarkable and the photonic crystal fibre （PCF） parameters vary with the frequency considerably. The precision of numerical simulation by using ASSFM is higher than that by using split-step Fourier method in the process of laser pulse propagation in PCFs due to the fact that the variation of fibre parameters with the peak frequency in the pulse spectrum can be taken into account fully.

Fourier hologram method using Gerchberg-Saxton algorithm for parallel femtosecond laser processing

In order to improve femtosecond laser throughput,a parallel processing system consisting of liquid crystal on silicon(LCOS)device as spatial light modulator is put forward.A method is described for displaying Fourier hologram on LCOS,and a high uniformity of several diffraction peaks in the computer reconstruction is achieved.Application of this method to the parallel femtosecond laser processing is also demonstrated,and two intersecting rings and three tangent rings are fabricated respectively by one time in the photoresist.

A Biproportional Construction Algorithm for Correctly Calculating Fourier Series of Aperiodic Non-Sinusoidal Signal

The Fourier series (FS) applies to a periodic non-sinusoidal function satisfying the Dirichlet conditions, whereas the being-processed function in practical applications is usually an aperiodic non-sinusoidal signal. When is aperiodic, its calculated FS is not correct, which is still a challenging problem. To overcome the problem, we derive a direct calculation algorithm, a constant iteration algorithm, and an optimal iteration algorithm. The direct calculation algorithm correctly calculates its Fourier coefficients (FCs) when is periodic and satisfies the Dirichlet conditions. Both the constant iteration algorithm and the optimal iteration algorithm provide an idea of determining the states of . From the idea, we obtain an algorithm for determining the states of based on the optimal iteration algorithm. In the algorithm, the variable iteration step is introduced; thus, we present an algorithm for determining the states of based on the variable iteration step. The presented algorithm accurately determines the states of . On the basis of these algorithms, we build a biproportional construction theory. The theory consists of a first and a second proportional construction theory. The former correctly calculates the FCs of at the present sampling time

融合CNN和ViT的声信号轴承故障诊断方法

针对轴承故障诊断任务数据量少、故障信号非平稳等特点,提出一种短时傅里叶变换、卷积神经网络和视觉转换器相结合的轴承故障诊断方法。首先,利用短时傅里叶变换将原始声信号转换为包含时序信息和频率信息的时频图像。其次,将时频图像作为卷积神经网络的输入,用于隐式提取图像的深层特征,其输出作为视觉转换器的输入。视觉转换器用于提取信号的时间序列信息。并在输出层利用Softmax函数实现故障模式的识别。试验结果表明,该方法对于轴承故障诊断准确率较高。为了更好解释和优化提出的轴承故障诊断方法,利用t-分布领域嵌入算法对分类特征进行了可视化展示。

基于空间变换技术的脉冲激光声信号检测

针对目前脉冲激光声信号检测方法极易受到环境噪声的影响,导致检测精确度不理想的问题。提出基于空间变换技术的脉冲激光声信号检测方法。首先,采用小波阈值法去除脉冲激光声信号中的噪声;其次,利用球傅里叶空间变换技术对声信号中的声源展开定位,获取声信号的准确位置;最后,分别提取声信号中的比值特征、比重特征、频率特征三种参数,在此基础上通过SVM算法对其展开分类识别,以此实现脉冲激光声信号的有效检测。实验结果表明,所提方法的声信号检测精度超过96%。

基于傅里叶级数展开的码垛机器人轨迹规划

为解决码垛机器人工作中因频繁启停而产生的冲击过大与常规多项式曲线规划效率低下等问题,课题组以SP-120系列码垛机器人为研究对象,采用改进D-H参数法建立机器人的D-H坐标系,进行正、逆运动学求解分析。利用基于傅里叶级数展开的轨迹规划方法进行了起始点至目标点的点对点连续轨迹规划,并利用MATLAB软件进行仿真分析。仿真结果表明:基于傅里叶级数展开所得各关节角位移、角速度和角加速度曲线连续、平稳,且工作空间运行轨迹平滑,解决了码垛工况下冲击过大问题;与五次多项式插值算法相比,得到了更大的峰值角速度和一段恒定的峰值角加速度,解决了常规多项式曲线规划效率低下问题。

非规则再生骨料建模及再生骨料混凝土数值模拟

传统再生骨料混凝土(RAC)模型多采用基本几何形状来代表再生骨料(RA)结构,这与实际情况差异较大。本文结合数字图像技术和傅里叶描述法构建了真实的二维骨料数据库,并提出了基于骨料叠加法随机生成RA的新方法。基于外接矩形框/内切圆的粗判定和基于重叠框的精细判定提出了一种新的适用于傅里叶重构骨料的快速投放算法,实现了不同RA取代率和RA残余砂浆含量的RAC细观结构的构建。基于内聚力模型根据随机生成的RAC的细观结构建立了数值模型,研究了RA取代率和RA残余砂浆含量对RAC单轴抗拉性能的影响。结果表明,RAC的抗拉强度和弹性模量随着RA取代率和RA残余砂浆含量的增加而降低,但峰值应变变化不大。该RA模型更符合实际,且附着砂浆的含量和分布可自主调整。

基于Fourier-Mellin算法的干涉图像配准

提出了采用Fourier-Mellin算法对大孔径静态干涉成像光谱仪的原始干涉图像进行配准的方法,用于校正由于推扫平台系统姿态不稳所造成的失真。采用Fourier-Mellin算法和相位相关算法求取干涉图像的旋转角度和缩放及平移参数,并通过多帧未校正的图像和校正后的图像分别拼接成大面积地域图像来验证算法。实验结果表明,通过人眼判断,可以实现对图像的配准,配准精度达到1 pixel,基本满足将LASIS原始干涉图校正为不失真图像的要求。

用于正弦波频率估计的修正I-Rife算法

对正弦波信号的频率估计是雷达领域常见的问题。当真实频率接近量化频点时,I-Rife算法的频移因子的计算会产生较大误差,为提高频率估计的精度,本文通过分析Rife及I-Rife算法的性能及误差产生的原因,利用频谱细化的方法,提出了一种修正I-Rife算法,即用峰值频点左右各0.5点处的频谱幅值来替代频谱峰值点的幅值和次大值频点处的幅值进行插值计算,对频率偏移值进行更为准确的估计,在计算量与I-Rife算法几乎相同的情况下,有效地提高了频率的估计精度。仿真结果表明,改进后的I-Rife算法整体性能优于I-Rife算法,且估计的均方根误差更接近于克拉美-罗下界。

复指数Fourier神经元网络隐神经元衍生算法

以平方可积空间上的复指数Fourier级数作为激励函数构造了新型Fourier神经元网络,并推导出采用加号逆表示的网络权值直接确定公式,克服了传统BP神经网络收敛速度慢、易陷于局部极小点、迭代学习易发生振荡等缺陷。并在此基础上构造了隐神经元衍生算法,克服了传统BP神经网络难以确定最优网络拓扑结构的缺点。理论分析及仿真实验表明,该复指数Fourier神经元网络能够一步计算网络最优权值且能自适应调整网络结构,对随机加性噪声具有抑制作用,并能高精度逼近非连续函数。

忆阻Fourier神经网络在图像复原中的应用

将传统Fourier神经网络与忆阻器相结合,用忆阻器做突触,构建新型的忆阻Fourier神经网络.推导忆导变化与权值更新的关系,提出忆阻突触权值更新规则,构建单输入忆阻Fourier神经网络,提出忆阻BP算法对模糊二值图像和灰度进行处理.Matlab仿真实验表明该算法可以有效实现图像复原,提高图像清晰度.忆阻Fourier神经网络有望用于解决复杂的图像处理问题.

基于半波Fourier算法的故障选相控制系统的设计

为了快速、准确地预测故障电流零点,设计了故障选相控制系统。基于故障选相原理,以数字信号处理器(DSP)TMS320F2812为核心,通过丰富其外设,进行控制系统硬件的设计;基于相电流突变量原理和改进半波Fourier算法,进行了故障起始时刻的判断和波形恢复,并完成了控制系统的软件设计。对故障选相控制系统的稳定性和零点预测准确度进行了测试。测试结果表明,控制器的预测结果准确、可靠,零点的预测时间<12ms,零点预测误差的3σ(σ为标准差)范围为[-0.6,0.6]ms,满足国际大电网会议(CIGRE)对选相投切控制系统准确度的要求。

SVM与Fourier算法在电网短期负荷预测中的应用

将Fourier(傅立叶)算法与SVM(支持向量机)共同引入电网短期负荷预测。对于波动性较大的负荷,Fourier算法用于滤除高次谐波分量。SVM用于对滤除了高次分量的数据进行统计学习,它首先筛选与预测点相关的历史数据构成训练样本,再将预测的平滑性和误差损失函数相结合构成问题的目标函数进行求解。编制了相应的软件,对某实际电网进行了短期负荷预测,取得了理想的结果。