基于二维空间的语音分形处理算法

提出了一种二维空间的语音分形增强算法。算法对已加窗、模块化的语音数据进行二维傅里叶变换。以分形维数构成自适应滤波器,降低噪声,增强语音,得到清晰的信号。研究表明,分形算法可以弥补传统线性分析方法的不足,二维自适应滤波前后语音的包络形状较好地保持了原始语音信号的特征,算法减小了由于非平稳噪声的影响,并有效抑制了音乐噪声。     

单片集成0.8μm栅长GaAs基InGaP/AlGaAs/InGaAs增强/耗尽型赝配高电子迁移率晶体管

优化了GaAs基InGaP/AlGaAs/InGaAs赝配高电子迁移率晶体管(PHEMT)的外延结构,有利于获得增强型PHEMT的正向阈值电压.采用光学接触式光刻方式,实现了单片集成0.8μm栅长GaAs基InGaP/AlGaAs/InGaAs增强/耗尽型PHEMT.直流和高频测试结果显示:增强型(耗尽型)PHEMT的阈值电压、非本征跨导、最大饱和漏电流密度、电流增益截止频率、最高振荡频率分别为0.1V(-0.5V),330mS/mm(260mS/mm),245mA/mm(255mA/mm),14.9GHz(14.5GHz)和18GHz(20GHz).利用单片集成增强/耗尽型PHEMT实现了直接耦合场效应晶体管逻辑反相器,电源电压为1V,输入0.15V电压时,输出电压为0.98V;输入0.3V电压时,输出电压为0.18V.     

时域卷积的区域线积分算法

本文用曲线积分对卷积积分作了图示解析,使积分区间的确定变得很直观、简便。对于复杂激励信号或数据表的数值卷积运算,也相应给出了图示算法。     

社区经理业务通知系统能设计与实现

目前，大多数固网运营商都有网上业务受理系统以及电话业务受理系统，希望通过这些形式方便用户，减轻营业厅压力。但是根据调查发现，具有上网条件、知道能够上网办理业务并且愿意上网办理业务的用户微乎其微。而电话受理这种方式，虽然比较简单，但目前仍然不被广大用户所认知，也就是说没有形成品牌效应，还没有发挥其应有的作用。     

功率增益截止频率为183GHz的In0.53Ga0.47As/In0.52Al0.48As HEMTs

通过合理的外延层材料结构设计和改进的器件制备工艺,制备出功率增益截止频率(fmax)为183GHz的晶格匹配InP基In0.53Ga0.47As-In0.52Al0.48As HEMT.该fmax为国内HEMT器件最高值.还报道了器件的结构、制备工艺以及器件的直流和高频特性.     

The research on suspended ZnO nanowire field-effect transistor

This paper reports that a novel type of suspended ZnO nanowire field-effect transistors (FETs) were successfully fabricated using a photolithography process, and their electrical properties were characterized by I--V measurements. Single-crystalline ZnO nanowires were synthesized by a hydrothermal method, they were used as a suspended ZnO nanowire channel of back-gate field-effect transistors (FET). The fabricated suspended nanowire FETs showed a p-channel depletion mode, exhibited high on--off current ratio of ～10⁵. When V_DS=2.5 V, the peak transconductances of the suspended FETs were 0.396 μS, the oxide capacitance was found to be 1.547 fF, the pinch-off voltage V_TH was about 0.6 V, the electron mobility was on average 50.17 cm²/Vs. The resistivity of the ZnO nanowire channel was estimated to be 0.96× 10²Ω cm at V_GS = 0 V. These characteristics revealed that the suspended nanowire FET fabricated by the photolithography process had excellent performance. Better contacts between the ZnO nanowire and metal electrodes could be improved through annealing and metal deposition using a focused ion beam.     

截止频率为218GHz的超高速晶格匹配In0.53Ga0.47As/In0.52Al0.48As高电子迁移率晶体管

报道了截止频率为218GHz的晶格匹配的In0.53Ga0.47As/In0.52Al0.48As高电子迁移率晶体管.这是迄今为止国内报道的截止频率最高的高电子迁移率晶体管.器件直流特性也很优异:跨导为980mS/mm,最大电流密度为870mA/mm.文中的材料结构和所有器件制备工艺均为本研究小组自主研制开发.     

Device research on GaAs-based InAlAs/InGaAs metamorphic high electron mobility transistors grown by metal organic chemical vapour deposition

This paper applies a novel quad-layer resist and e-beam lithography technique to fabricate a GaAs-based InAlAs/InGaAs metamorphic high electron mobility transistor (HEMT) grown by metal organic chemical vapour deposition (MOCVD). The gate length of the metamorphic HEMT was 150~nm, the maximum current density was 330~mA/mm, the maximum transconductance was 470~mS/mm, the threshold voltage was -0.6~V, and the maximum current gain cut-off frequency and maximum oscillation frequency were 102~GHz and 450~GHz, respectively. This is the first report on tri-termination devices whose frequency value is above 400~GHz in China. The excellent frequency performances promise the possibility of metamorphic HEMTs grown by MOCVD for millimetre-wave applications, and more outstanding device performances would be obtained after optimizing the material structure, the elaborate T-gate and other device processes further.     

一种InGaAs/InP复合沟道高电子迁移率晶体管模拟的新方法

采用一种新方法对InGaAs/InP复合沟道高电子迁移率晶体管进行了模拟.该方法通过流体力学模型和密度梯度模型的联合求解,得到了沟道内的电子密度分布.与一些传统方法相比,该方法收敛性更好,速度更快,且同样适用于其他类型高电子迁移率晶体管器件的模拟.利用仿真对InGaAs/InP复合沟道高电子迁移率晶体管进行了深入研究.     

基于单边自相关线性预测的语音去噪声算法

提出了一种在自相关域上，以相关函数值为参数，利用单边自相关序列的线性预测误差去除语音中加性噪声的方法。该方法首先对含噪语音进行单边自相关处理，以语音信号的单边自相关序列替代语音信号序列，进而对该序列进行线性预测分析后，获得线性预测分析系数，并求得线性预测误差。根据误差能量与信号能量的比例关系，确定减因子u，从含噪语音中根据减因子u的大小减去预测误差，即可抑制噪声误差能量。实验表明；上述方法在低信噪比时，仍能较好地保留语音信号的频谱结构，使音质不至于下降。