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一种模拟与数字兼容的无线电移动通信综合测试仪陈白随着通信业的不断发展和进步,无线电移动通信也从模拟迈向了数字、为了适应这一情况,出现了数字无线电移动通信专用测试仪器。然而,模拟无线电移动通信仍在许多地方担任主角,在相当长的一段时间内,模拟和数字两种制... 相似文献
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The technology of black coloring for stainless steel by electrochemical method was studied. The optimum bath compositions and operating conditions were obtained as follows. 40 - 50 g/L K2Cr2O7, 15 - 20 g/L MnSO4, 15 -20 g/L (NH4)2SO4, 20 -40 g/L H3BO3, 20 -30 g/L additive A, 2 g/L (NH4)6Mo7O24 ; time 9 -20 min; temperature 15 - 30 ℃ ; potential 3 V and current density 1 - 2 mA/cm^2. The effects of the compositions of the bath on the quality of black colored film were discussed. The influences of passivation process on the black coloring velocity and performances of black colored film layer were investigated. The results show that the passivation process can improve the corrosion resistance and the stability to bear color-change; (NH4)2 SO4 can control the black coloring velocity and prolong black coloring bath life remarkably; and additive A can improve the evenness and compactness of black colored film layer. The results of scanning electron microscopy and energy dispersive spectra show that the microstructure is of cylindrical lump, the filling process can decrease the crackles, and the main elements of black colored film are Fe, Cr, Mn and Ni. 相似文献
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小波分析算法研究及在齿轮与滚动轴承故障诊断中应用 总被引:2,自引:0,他引:2
分析了齿轮与滚动轴承故障振动信号的特征,利用小波变换的分解和重构算法,有效地提取出齿轮与滚动轴承故障特征信号,得到实验结果.通过比较频谱分析和小波分析的特点,有效地证明了小波分析在微弱故障信号提取中的优势. 相似文献
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以5 种梵净山茶为研究对象,基于其主要生物活性成分及抗氧化能力进行主成分分析和聚类分析并进行综合评价。结果表明,小毛峰茶的茶多酚含量、总黄酮含量和茶多糖含量相比于其余4 种梵净山茶最高,其中总黄酮含量高达(25.83±0.12)g/100 g;总游离氨基酸含量最高为金茯砖茶(1.95±0.00)g/100 g,各生物活性成分及抗氧化能力之间相关性差异显著。对各生物活性成分进行主成分分析,最终提取总黄酮为主成分,其贡献率高达97.07%,可以反映大部分信息。对5 种梵净山茶的生物活性成分进行聚类分析,将藤茶和金茯砖茶聚为一类,说明两者具有较大的相似度,苔茶为一类,明显区分于其余4 种梵净山茶;生物活性成分中茶多酚、茶多糖、维生素C 为一类,总黄酮为一类,总游离氨基酸为一类。梵净山茶的生物活性成分含量丰富以及抗氧化性强,值得进一步深入的研究。 相似文献
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基于小波包变换和小波阈值消噪的语音特征提取 总被引:1,自引:0,他引:1
为了实现强噪声背景下语音信号的特征提取,根据小波变换的多分辨率特性,以及与人耳耳蜗滤渡相一致的特性,利用小波包变换,在各语音特征频率段上,提取出包含丰富的非平稳信息的语音特征;并在小波包分解去噪的基础上,构造了模糊阈值函数,利用小波模糊阈值去噪,得到了信噪比较高的语音信号.研究结果表明,小波包变换和小波阈值去噪,较好地消除了强噪声背景下的噪声,并有效地提取出了语音信号特征. 相似文献
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1 Introduction Electroless plating tin and tin alloy is an attractive technique to produce function plating layer with prior performances of corrosion resistance and decoration[1, 2], due to the possibility of uniform deposition on complex shapes, conduct… 相似文献