热轧除鳞系统节能方案

针对热轧除鳞系统普遍存在的能源浪费严重的问题,设计了基于预测模型的变频节能方案,通过板坯位置预测、除鳞时间预测、除鳞水量预测和除鳞泵转速控制,合理利用轧制间歇时间使水泵电机变频降速,模拟计算结果表明,可使除鳞电耗降低23.57%。     

Two low-permittivity melilite ceramics in the SrO-MO-GeO2 (M = Mg,Zn) system and their temperature stability through compositional modifications

Two melilite ceramics Sr₂AGe₂O₇ (A = Mg, Zn) with low permittivity were prepared by a solid-state reaction method. The crystal structure and microstructure of the ceramics were characterized by X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and scanning electron microscopy. Both ceramics crystallized in a single melilite structure with a tetragonal space group P-42m (113) and exhibited homogeneous microstructures. Optimum microwave dielectric properties with relative permittivity (ε_r) of 8.56, quality factor (Q × f) of 28,800 GHz, and temperature coefficient of resonance frequency (τ_f) of −70.5 ppm/°C were obtained in Sr₂MgGe₂O₇ sintered at 1330 °C. Sr₂ZnGe₂O₇ possessed ε_r of 8.81, Q × f of 35,700 GHz, and τ_f of −84.4 ppm/°C when sintered at 1290 °C. Thermal stability of resonance frequency was accessible when the negative τ_f values of Sr₂AGe₂O₇ were adjusted after the formation of composite ceramics with CaTiO₃.     

25CrNi2MoV钢的微动磨损性能

采用微动摩擦磨损试验机在干摩擦条件下对新型高速重载传动轴用25CrNi2MoV钢进行微动磨损试验,研究了不同载荷(50~200N)和频率(15~30Hz)下该钢的微动磨损性能。结果表明:在频率为20Hz条件下,当载荷由50N增至200N时,25CrNi2MoV钢的平均摩擦因数由0.766减至0.661,磨损体积由19.65×10^-3 mm^3增至75.83×10^-3 mm^3;在载荷为30N条件下,当频率由15Hz增至30Hz时,平均摩擦因数由0.790增至0.905,磨损体积由11.43×10^-3 mm^3增至23.88×10^-3 mm^3;在不同试验参数下,25CrNi2MoV钢磨损表面均出现了氧化和犁沟现象,磨损机制包含氧化磨损和磨粒磨损;在频率为20Hz条件下,载荷为50,100N时,25CrNi2MoV钢的磨损机制以黏着磨损为主,载荷为150,200N时,主要磨损机制为疲劳磨损;在载荷为30N条件下,频率为15~25Hz时,磨损机制以磨粒磨损为主,当频率增至30Hz时,磨损机制以疲劳磨损为主。     

Physicochemical characteristics,antioxidant capacity and thermodynamic properties of purple-fleshed potatos dried by radio frequency energy

Abstract

The impacts of using radio frequency (RF) energy to dry purple-fleshed potatoes were investigated and compared to infrared radiation (IR) and microwave (MW) drying techniques. The gelatinization rate, color, flavor, morphological, and structural characteristics, thermodynamic properties, as well as antioxidant capacity were examined. The results indicated that the drying time of RF (70?min) and MW (21?min) were shorter than IR (105?min). The gelatinization ratio of MW, RF, and IR were 94.4?±?2.0, 88.3?±?1.4, and 64.5?±?1.1%, respectively. The degree of crystallization of purple-fleshed potato powder decreased with all three drying methods. RF-dried potatoes were able to retain higher polyphenols (loss rate: 4.3%), total anthocyanin (3.7%), and total flavonoid content (35.1%), whereas IR showed the lowest retention. The content of polyphenols also decreased significantly. Furthermore, after RF heating, the scavenging of free radicals was higher compared to MW and IR.     

脉冲电流对6016-T4铝合金板材力学性能的影响

为研究在电流辅助成形时脉冲电流的电流密度、占空比和脉冲频率3个因素对6016-T4铝合金板材力学性能的影响规律,设计了3因素5水平的正交实验。实验表明,对6016-T4铝合金力学性能影响的主次因素是:电流密度>占空比>脉冲频率。在此基础上,选用主次2个因素,即电流密度和脉冲频率,使用控制变量法进行进一步的实验研究。实验结果表明,电流密度对6016-T4铝合金力学性能影响较大,改变电流密度的同时带来了明显的焦耳热效应,该效应对材料有明显的软化作用,降低了材料的流动应力,但是,同时也降低了铝合金板的伸长率,这是因为过大的电流密度加剧了试样的主应变演化,进而促进了试样的断裂。而脉冲频率的变化对6016-T4铝合金板材的力学性能影响很小,这也印证了正交实验的结论。     

基于深度网络迁移学习的致痫区脑电识别* .txt

摘要：致痫区脑电识别能够为癫痫外科手术提供重要的参考价值。提出了一种基于深度网络迁移学习的致痫区脑电识别算法。首先利用连续小波变换（CWT）对脑电信号进行时频分析，获得脑电信号时频图；然后迁移学习AlexNet网络模型，调整网络结构使之适应于致痫区脑电识别，将模型第7层全连接层输出作为脑电信号时频图的特征表示，最后利用支持向量机（SVM）、BP神经网络、长短期记忆网络（LSTM）、基于稀疏表达分类算法（SRC）、线性判别分析（LDA）等分类算法进行特征分类。基于开源脑电数据集采用十折交叉验证的方法对算法进行了验证,比较6种分类器的效果，得到SVM算法的平均特异性为8881%，灵敏度为8807%，准确率为8844%，证明了该方法识别致痫区脑电信号的有效性。 .txt     

基于人工神经网络的柴油机失火故障诊断

车载诊断系统在诊断失火故障时,采用基于曲轴段角加速度和阈值规则相结合的方法,该方法在内燃机高速轻载运行时诊断单缸完全失火工况存在一定的局限性。通过对比分析失火和正常工况下曲轴瞬时转速的幅频和相频特征,提取不同谐次的幅值和相位信息,结合人工神经网络作为故障模式识别工具,得到了一种改善方法。通过台架实验,对此改善方法进行了单缸完全失火、两缸完全失火和单缸一定程度失火的故障诊断测试。结果表明,在实验条件下该方法可以有效识别不同的失火模式,并可在单缸失火模式下实现失火程度判别。同时,该方法通过少量工况数据训练神经网络,即可实现一定转速范围内的失火诊断,可行性强,可用于发动机失火故障在线诊断。     

Allocation and sizing of battery energy storage system for primary frequency control based on bio-inspired methods: A case study

This paper presents a new procedure for optimal allocation and optimal sizing of a battery energy storage system (BESS) for primary frequency support in an isolated power system. For the BESS allocation, a transmission bus system with larger frequency decline is recognized and the BESS sizing is performed by a constrained optimization strategy based on a new modified metaheuristic, called Developed Harris Hawks Optimization (DHHO). The simulation results of the suggested DHHO are compared with Bat Optimization Algorithm (BOA) and Genetic Algorithm (GA) from the literature to show the method efficiency. The final results showed higher precision with lower required iterations for the suggested DHHO method. Also, the proposed DHHO gives lower investment costs for BESS with lower power and energy requirement toward the other compared methods.     

钢轨交流闪光焊接过程过梁爆破特征分析

以高速摄影技术作为主要研究手段，研究钢轨交流闪光焊接过程过梁爆破特征，并结合热成像系统采集焊接过程温度场，以此为数据基础定量分析了钢轨交流闪光焊接过梁爆破特征. 结果表明,钢轨交流脉动闪光焊接工艺模式下，加速闪光阶段具有几个阶段中最高的闪光频次46.93次/s，脉动闪光阶段具有最低的闪光频次11.07次/s；连续闪光阶段闪光烈度为0.009 2 mm/次，是几个阶段中最强的，脉动阶段的闪光烈度最弱，为0.003 8 mm/次；从闪光加热因子来看，脉动阶段最高，符合了该阶段积累热量的主要目的；加速闪光阶段最低，是由于该阶段为了制造保护气氛产生的气化过梁带走了较多的热量；从闪光均匀度看，闪光最不均匀的阶段是闪平阶段，最均匀的阶段是脉动阶段，这恰恰说明了两待焊端面的微观平行情况在闪平阶段最差、脉动阶段最佳.     

掺铒单模光纤飞秒脉冲激光器和放大器

为了获得一种被动锁模掺铒光纤振荡器及功率放大器，数值模拟出超短脉冲在光纤中的传输和演化过程，并基于此搭建了一种被动锁模掺铒光纤飞秒振荡器及功率放大器。实验获得了中心波长1560 nm、重复频率100 MHz、输出功率30 mW、脉冲宽度85 fs超短脉冲。通过采用PPLN晶体进行倍频，进一步获得了输出功率5 mW，中心波长780 nm的飞秒脉冲。该光纤激光器为全保偏光纤结构，具有体积小巧、可靠性高、稳定性好的特点。