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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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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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LTR集群移动通信系统及其测量陈白1移动台和转发器移动台的许多功能已用逻辑控制器件来完成,不必再用手动控制,所以比传统的对讲机操作方便,如:信道选择,静噪控制等等都是如此。移动台有双工和单工之分,按需要配置。一般每个移动台最多可编入20条信道。美国L... 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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