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1.
金属材料声发射信号特征提取方法   总被引:2,自引:0,他引:2  
试图通过对声发射信号的检测实现对水轮机转轮叶片金属疲劳裂纹的在线监测。利用美国PAC公司SAMOS声发射检测系统采集到声发射的各种参数:针对大型水轮机现场环境的情况,选用了四种声发射信号。通过BP神经网络和模式识别结合的方法,设计特征提取器来提取金属材料疲劳声发射特征信号。比较神经网络输人参数对输出结果的灵敏度,选择出一些对分类识别最有效的特征参数:并采用可分离性判据进一步验证其正确性。最后,在13个声发射特征参数中,质心频率、计数、持续时间、上升时间、平均信号电平等五个参数的特征最为显著,可以用于识别现场环境下的声发射信号。  相似文献
2.
基于蚁群算法岩体可爆性分级的投影寻踪回归方法   总被引:1,自引:0,他引:1  
在分析影响岩体可爆性因素的基础上,选择岩体坚固性系数、声阻抗、炸药消耗量、平均裂隙距作为岩体可爆性分级评判指标,建立岩体可爆性分级的投影寻踪综合评价模型,利用蚁群算法优化其投影方向,根据投影特征指标值对岩体可爆性进行分级评价,并将其应用于某地下岩体可爆性分级。评价结果表明,该评价模型可以避免主观因素对权重确定的影响,评价结果客观准确,为岩体可爆性综合判别提供了一种新的方法。  相似文献
3.
本文详细介绍了共沉淀制取ITO粉末的工艺技术以及简化的新工艺新技术,同时介绍了有发展前途的涂敷用的ITO粉末制取工艺。  相似文献
4.
利用冬天的低温条件,考察了15℃、20℃、25℃与7~9℃对PAC-MBR的影响.试验结果表明,膜污染速率随着温度的下降而呈现加剧趋势.15℃与7~9℃对T脚(膜内外传递压力)之差随膜污染的增加而逐渐减少,而20℃和25℃与7~9℃对TMP之差的趋势均随着运行时间而增加;加温后的PAC-MBR的上清液COD明显高于7~9℃下的上清液COD,但是经过膜过滤后,出水COD(化学需氧量)相差无几.20℃和25℃的上清液氨氮明显低于7~9℃,而出水则无明显规律.温度对MBR中微生物,特别是后生动物的种类和数量的影响并不显著.  相似文献
5.
The cubic MnCo2O4 was prepared by calcining MnCO3-2CoCO3?1.5H2O above 600 °C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, and vibrating sample magnetometer. The result showed that high-crystallized MnCo2O4 with cubic structure [space group Fd-3m(227)] was obtained when the precursor was calcined above 600 °C in air for 6 h. Magnetic characterization indicated that cubic MnCo2O4 behaved weak magnetic behavior at room temperature. The thermal process of the precursor in air experienced three steps, which are: first, the dehydration of 1.5 water molecules, then the decomposition of MnCO3-2CoCO3 into cubic MnO2 and cubic Co3O4, and at last the reaction of MnO2 with Co3O4 into cubic MnCo2O4. Based on the KAS equation, the values of the activation energies associated with the thermal process of MnCO3-2CoCO3?1.5H2O were determined.  相似文献
6.
Co0.5Mn0.5La x Fe2?x O4 precursor was synthesized by solid-state reaction at low temperatures using CoSO4 ?7H2O, MnSO4 ?H2O, FeSO4 ?7H2O, La(NO 3)3 ?6H2O, and Na2 CO 3 ?10H2O as raw materials. Co0.5Mn0.5La x Fe2?x O4 was obtained by calcining carbonates precursor in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, X-ray powder diffraction, scanning electron microscopy, and vibrating sample magnetometer. A high-crystallized Co0.5Mn0.5La x Fe 2?x O4 with a cubic structure was obtained when the precursor was calcined at 700 °C in air for 2 h. The specific saturation magnetizations and coercivity of Co0.5Mn0.5La x Fe2?x O4 depend on the calcination temperature and composition. The thermal transformation of Co0.5Mn0.5CO3–Fe2O3?0.967H2O from 700 °C in air presented two steps. The values of the activation energies associated with the thermal transformation of Mn0.5Co0.5CO3–Fe2O3?0.967H2O were determined based on the Kissinger–Akahira–Sunose (KAS) equation  相似文献
7.
Cu0.5Zn0.5Fe2O4 precursor was synthesized by solid-state reaction at low heat using CuSO4?5H2O, ZnSO4?7H2O, FeSO4?7H2O, and Na2CO3?10H2O as raw materials. The spinel Cu0.5Zn0.5Fe2O4 was obtained via calcining precursor above 600 °C. The precursor and its calcined products were characterized by thermogravimetry and differential thermal analyses (TG/DTA), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), and vibrating sample magnetometer (VSM). The result showed that highly crystallization Cu0.5Zn0.5Fe2O4 was obtained when the precursor was calcined at 600 °C for 2 h. Magnetic characterization indicated that calcined products above 600 °C behaved with strong magnetic properties. The kinetics of the thermal decomposition of the precursor was studied using the TG technique. Based on the KAS equation, the values of the activation energy for the thermal decomposition of the precursor were determined.  相似文献
8.
Cu0.5Mg0.5Fe2O4 precursor was synthesized by solid-state reaction at low heat using CuSO4?5H2O, MgSO4?6H2O, FeSO4?7H2O, and Na2C2O4 as raw materials. The spinel Cu0.5Mg0.5Fe2O4 was obtained via calcining precursor above 300?°C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry (TG/DSC), Fourier transform FT-IR, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), and vibrating sample magnetometer (VSM). The result showed that Cu0.5Mg0.5Fe2O4 obtained at 600?°C had a saturation magnetization of 36.8?emu?g?1. The thermal process of Cu0.5Mg0.5Fe2O4 precursor experienced two steps, which involved the dehydration of the five and a half crystal water molecules at first, and then decomposition of Cu0.5Mg0.5Fe2(C2O4)3 into crystalline Cu0.5Mg0.5Fe2O4 in air. Based on the Kissinger equation, the values of the activation energy associated with the thermal process of the precursor were determined to be 85 and 152?kJ?mol?1 for the first and second thermal process steps, respectively.  相似文献
9.
张家宙 《影像技术》2013,25(2):30-32
目的:探讨宝石能谱CT扫描下肢静脉成像技术的可行性。材料与方法:回顾性选取本院2012年12月至2013年1月进行的下肢静脉GSI扫描检查的患者36例,36例患者均在肘静脉注射对比剂后延时150s行下肢静脉扫描,造影剂浓度370mg/ml,注射速率4ml/s,总剂量100-120ml。扫描采用轴扫,扫描条件:120kV,mA为自动选择,旋转时间0.5秒;准直64x0.625mm;螺距1.375∶1。重建层厚0.625mm,层距0.625mm。扫描过程中保持患者下肢静止不动,扫描范围自下而上从踝至髂总分叉上2cm处。扫描后将图像载入AW4.6工作站。利用能谱分析浏览器(GSI Viewer),进行常规VR(混合能量)重建和单能量容积重建法(GSI VR),配合多层面重建法(MPR)和最大密度投影法以(MIP)对下肢静脉及其分支进行重建,评价下肢静脉GSI扫描不同重建方法对下肢静脉成像的效果,所有图像由两位高年资的医生进行评估。结论:能谱扫描GSI单能重建的方法较混合能量重建方法能大大提高下肢静脉成像的成功率和较高的静脉成像满意度,同时大大降低了患者的辐射剂量,具有很好的临床应用价值。  相似文献
10.
本文报道了"碱融-酸浸"法对工业生产SiC的副产品石墨废料的提纯研究,通过研究焙烧温度、焙烧时间、酸浸浓度、酸浸时间等因素对提纯效果的影响,确定了该类石墨提纯工艺的最佳条件:实验中NaOH与石墨质量比为2∶1,焙烧温度为650℃,焙烧时间为60min;室温下酸浸过程的HCl浓度为10%,酸浸时间为180min,此条件下提纯后的石墨其固定碳含量提升到98%以上。  相似文献
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