区分家人与客人的门铃

区分家人与客人的门铃张晓东该门铃能够用不同声响区分出叫门者是家人还是客人。当客人来访按一般习惯按下门口的按钮开关时，它便发出带有余音的“叮咚＂双音声；当家人归来按事先约定连续快速地按开关３、４次时，门铃即发出清脆悦耳的鸟鸣声。整个门铃制作成本不超过１...     

维生素B12模型分子侧链钴-氮键稳定性研究

维生素B12(VB12)模型分子[单腈六甲基-N-(3-咪唑基)丙酰胺钴啉酯高氯酸盐4b-4f],在甲醇溶液中用酸性缓冲溶液处理生成5b-5f.通过测定不同pH的缓冲溶液中的UV-Vis谱,计算了Co-N键的平衡常数,侧链氮原子与中心钴离子配位键的强弱次序为4d＞4f＞4c＞4e＞4b.     

关于HADAMARD不等式的注记

本文主要研究一类Ｆ－矩阵的性质，这类矩阵包含对称半正定矩阵，完全非负矩阵，τ矩阵和Ｍ－矩阵为其子类。我们不仅对Ｆ－矩阵改进了Ｈｄａｍａｒｄ不等式，而且证明对此类矩阵Ｈａｄａｍａｒｄ不等式成立等式的充要条件是它的每条对角线，除主对角线外，都含有零元。     

微波探测器TX982及其应用(上)

本文介绍的TX982型微波探测器也叫雷达探测模块、人体探测器,TX982内部包含了微波发射、接收及信号放大、识别等电路,能够以非接触形式探测出周围一定范围内的运动人体或物体,并转换成高电平信号输出;它具有探测灵敏度高、作用范围大、可靠性能好、安装使用简便等优点,是设计和     

远距离、稳频型无线编码遥控组件

本文介绍的无线编码遥控组件由固定式远距离稳频发射器T94W4及宽带接收模块T2068CK组成。其操纵通道有4位(最多可扩展为16位),发射器内部采用高品质专用声表面波谐振器SAW稳定频率,通过地址和数据加密方式传递遥控信号,在开阔地有效控制距离达800m,可广泛应用于高性能、严要求的各种固定式远距离遥控或防盗报警     

Fabrication of 80-nm T-gate high indium In0.7Ga0.3As/In0.6Ga0.4As composite channels mHEMT on GaAs substrate with simple technological process

An 80-nm gate length metamorphic high electron mobility transistor (mHEMT) on a GaAs substrate with high indium composite compound-channels In_0.7Ga_0.3As/In_0.6Ga_0.4As and an optimized grade buffer scheme is presented. High 2-DEG Hall mobility values of 10200 cm²/(V· s) and a sheet density of 3.5 × 10¹² cm^-2 at 300 K have been achieved. The device's T-shaped gate was made by utilizing a simple three layers electron beam resist, instead of employing a passivation layer for the T-share gate, which is beneficial to decreasing parasitic capacitance and parasitic resistance of the gate and simplifying the device manufacturing process. The ohmic contact resistance R_c is 0.2 Ω ·mm when using the same metal system with the gate (Pt/Ti/Pt/Au), which reduces the manufacturing cycle of the device. The mHEMT device demonstrates excellent DC and RF characteristics. The peak extrinsic transconductance of 1.1 S/mm and the maximum drain current density of 0.86 A/mm are obtained. The unity current gain cut-off frequency (f_T) and the maximum oscillation frequency (f_max) are 246 and 301 GHz, respectively.