基于LASSO-WOA-LSSVM的海洋管线外腐蚀速率预测

目的 构建海洋管线外腐蚀速率预测模型,提高海底油气管线外腐蚀速率预测的准确性.方法 建立基于套索(LASSO)回归和鲸鱼优化算法(WOA)的最小二乘支持向量机(LSSVM)腐蚀速率预测模型,采用LASSO回归方法对指标进行筛选,提取海洋管线腐蚀的主要影响因素.应用最小二乘支持向量机算法建立海洋管线外腐蚀速率预测模型,并使用鲸鱼优化算法对模型参数进行优化,避免了参数取值对模型回归性能的影响.以海洋挂片实验为例,通过MATLAB进行模拟仿真,分析验证模型预测结果,并将预测结果与其他模型进行对比分析.结果 LASSO回归算法筛选得到影响腐蚀速率的主要因素为:温度、溶解氧含量、pH值.采用WOA-LSSVM模型所预测的结果与实际值较为吻合,其平均相对误差为2.23％,均方根误差(RMSE)为0.3248,决定系数R2达到0.9708,均优于其他两种模型.结论 基于LASSO回归和鲸鱼优化算法的最小二乘支持向量机预测模型具有更优的泛化能力和预测精度,为海底管道腐蚀研究工作提供了新思路,也为海洋油气输送系统的结构安全与风险防范提供了参考.     

基于模拟退火耦合粒子群算法优化BP神经网络的机床主轴热误差补偿研究

为了降低机床主轴运行产生的热误差,建立混合算法优化BP神经网络预测模型,通过实验验证预测精度。分析模拟退火算法和粒子群算法的不足,采用模拟退火算法耦合粒子群算法,给出混合算法寻优步骤。引用BP神经网络结构,构造机床主轴热误差预测模型,采用混合算法优化BP神经网络预测模型。采用实验验证主轴热误差预测精度,并与优化前进行比较和分析。结果显示:采用混合算法优化后的BP神经网络预测模型,其Y轴方向产生的最大误差值从7.3μm降低到2.3μm;而Z轴方向产生的最大误差值从7.5μm降低到2.6μm。同时,机床主轴整体误差波动幅度较小。采用混合算法优化BP神经网络预测模型,用于机床主轴热误差在线补偿,提高了加工精度。     

MEA优化BP神经网络的电主轴热误差分析研究

针对磨齿机在磨削加工时,电主轴存在热致误差等问题,提出一种基于思维进化算法(MEA)优化BP神经网络建立磨齿机电主轴热误差预测模型的方法。通过测量磨齿机电主轴在加工过程中的温升与位移情况,利用思维进化算法优化BP神经网络算法在MATLAB软件中建立预测模型,并与未经过算法优化的BP神经网络建立的模型进行了对比。在电主轴X向热误差预测实验中,未经过算法优化的BP模型最低补偿率为84.85%,而经过思维进化算法优化BP模型最低补偿率为95.29%。结果表明:经过思维进化算法优化BP神经网络建立的热误差模型,在拟合和预测精度上要优于未经过算法优化的BP神经网络热误差模型。     

多工况下数控机床主轴热误差建模

单一工况条件下数控机床主轴热误差模型无法准确预测其它工况下的热误差。通过研究分析支持向量机回归的算法和参数的关系,提出一种经过遗传算法(GA)在多工况条件下优化的支持向量机(SVM)的建模方法。以一台数控车床为研究对象,进行热误差测量实验,利用电涡流位移传感器和温度传感器同步测量机床主轴两个方向热误差和温度变化数值,获取两种工况的建模数据。运用遗传算法对SVM的惩罚函数、核函数参数和不敏感损失函数进行多工况条件下的优化选择,建立机床主轴热误差补偿模型。通过热误差建模实验验证,该方法在工况一的残差为0.838μm,工况二的残差为0.653μm,在保持较高预测精度的同时,能在两种工况下进行有效的热误差预测,使热误差补偿更适合实际加工环境。     

基于SSA-BP的电主轴热误差优化建模

为解决某加工中心电主轴的热误差补偿问题，建立预测精度高、鲁棒性强的热误差补偿模型。搭建实验台，利用美国雄狮回转误差分析仪采集电主轴的温度场和热误差数据。介绍麻雀搜索算法(SSA)原理、具体优化流程。采用SSA优化BP神经网络的权值和阈值，建立SSA-BP神经网络预测模型。与之前建立的BP神经网络预测模型相比，优化后预测效果更优，为电主轴热误差建模提供新的思路。     

支持向量回归在Zr-2合金晶粒尺寸预测中的应用

根据Zr-2合金的晶粒尺寸在不同热工艺参数(变形温度、变形程度、变形速率)下的12组实测数据,应用基于粒子群算法寻找最优参数的支持向量回归方法,建立了合金晶粒尺寸的预测模型.通过与模糊神经网络模型的结果进行比较,结果表明:基于相同的试验样本,支持向量回归预测模型的平均绝对误差和平均绝对百分误差都比模糊神经网络预测模型的小,而复相关系数大.这说明,支持向量回归预测模型预测精度比模糊神经网络模型要高,是简单而精确的建模方法,可用于优化热加工参数.     

自蔓延高温合成多孔NiTi合金孔隙的SVR预测

根据自蔓延高温合成法(SHS)制备多孔NiTi合金孔隙试验所获得的实测数据集,应用基于粒子群算法(PSO)寻优的支持向量回归(SVR)方法,建立不同反应参数(温度,粒度和压坯密度)下合成的多孔NiTi合金孔隙的SVR预测模型,并与基于误差反向传播神经网络(BPNN)回归模型的预测结果进行比较。结果表明：在相同的训练与测试样本集下所获的SVR预测结果的平均绝对百分误差(MAPE)比BPNN预测模型的要小,其预测精度更高,预测效果更好;SVR-LOOCV预测的MAPE也比BPNN略小,且其预测结果的相关系数达到了0.999。因此,该方法是一种预测SHS法制备多孔NiTi合金孔隙的有效方法,可为SHS合成多孔NiTi提供理论指导     

基于支持向量回归机的精密数控平台热误差建模与补偿研究

为了提高数控机床的加工精度,文章以精密四轴数控平台为研究对象,采用PT100、激光干涉仪等仪器对X、Z轴的温度、定位误差进行测量与分析,研究精密四轴数控平台定位误差与温度之间的变化规律。运用支持向量回归机建立X、Z轴的热误差模型,利用网格搜索法对支持向量回归机热误差模型进行参数寻优,确定惩罚参数c和核函数参数g的最优参数值。在热平衡状态下,根据BP神经网络、支持向量回归机热误差模型分别计算出X、Z轴定位误差的预测值与测量值对比曲线,对比曲线和数据分析表明支持向量回归机的预测精度较高,其X、Z轴拟合偏差带宽均不超过0.6μm。依据支持向量回归机热误差模型的预测数据进行补偿实验,数控平台X轴的定位误差降低了89.55%,Z轴定位误差降低了85.67%。实验结果证明支持向量回归机建模方法具有较高的预测精度、泛化能力、补偿精度和鲁棒性。     

面向电主轴热误差预测建模分析的改进IGWO-LSTM算法

针对电主轴复杂运行工况下的热误差建模问题,提出一种基于改进灰狼优化算法(IGWO)的LSTM神经网络参数预测模型IGWO-LSTM。通过对灰狼算法收敛因子a计算方法进行优化来提高算法寻优性能;通过IGWO算法的适应度函数与LSTM隐含层节点数组成的IGWO-LSTM闭环系统对电主轴热误差预测模型进行训练和预测,避免陷入局部最优,同时提升模型预测精度。为了验证该算法性能,将它与改进前的算法进行对比,通过求取平均绝对误差、平均绝对百分比误差以及均方根误差对这两种神经网络进行评价,结果显示：文中算法的3种指标均优于改进前的LSTM模型,具有更好的热误差预测准确性和全局搜索能力。     

机床热误差非线性组合预测模型研究

在精密及超精密加工过程中,数控机床热误差是影响加工精度的一项重要误差源,最经济和有效地减少热误差的方法是热误差补偿技术。针对热误差补偿预测模型的预测精度问题,提出一种非线性组合预测模型。该预测模型利用灰色关联度方法对单项预测模型进行筛选,对筛选出的单项预测模型基于不同优化准则进行线性组合,通过广义回归神经网络对该线性组合模型进行非线性组合,得到非线性组合预测模型。误差预测结果表明:对比典型的BP神经网络预测模型,非线性组合预测模型的预测精度更高,最大误差由4.78μm减小到0.7μm。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。