金属膜层对光纤表面等离子传感器的影响研究

采用SG-12SA作为镀膜设备, 研究了当金膜厚度相同的情况下, 光纤表面等离子体波传感器在有粘结层和无粘结层时的光谱特性; 当粘结层厚度相同时, 光纤表面等离子体波传感器对应不同金膜厚度的光谱特性。结果表明：对镀有同样金膜厚度的光纤表面等离子体波传感器, 纤芯与金膜之间有粘结层相对于无粘结层, 共振波长出现红移, 且共振深度减小; 对镀有同样粘结层厚度的光纤表面等离子体波传感器, 随着金膜厚度的增加, 共振波长亦逐渐发生红移。这些研究成果为以后研制性能优良的光纤传感器提供了参考, 同时为在直径为微米级的三维圆柱面上镀膜提供一定的指导意义。     

高频电磁波的透入深度

高频电磁波与导波介质的作用,涉及光纤通信、宇航通信等领域,这里将根据场论就高频电磁波（包含光频）的透入深度进行论述。这里的导波介质空间可视为没有自由电荷和传导电流的空间,根据麦克斯韦电磁场方程×Ｈ＝Ｄｔ×Ｅ＝Ｂｔ·Ｄ＝０·Ｂ＝０对于频...     

中国电信业的改革与竞争

１．竞争提高效率长期以来,中国电信业的基本特征是公用电信网的建设和业务运营服务由邮电部独家经营,邮电部既是电信业的经营者,又是电信业的政府管制机构。伴随着改革开放和国际电信业务开放的步伐,我国电信领域已出现了一些人所共知的变化。中国与ＷＴＯ谈判的主要焦点问题之一就是何时开放电信市场,即使不立即开放,按《全球基础电信协定》的规定,要加盟世界贸易组织就必须作出开放本国电信市场的安排。中国电信网络技术水平和设备的先进性已经超过了不少发达国家,但运行效率、运行质量和经济效益却相差甚远。中国电信市场一旦开…     

用Franz-Keldysh效应研究GaAs表面硫化学钝化

硫钝化是一种比较有效的钝化ＧａＡｓ表面的方法．本文使用Ｎａ２Ｓ、Ｓ２Ｃｌ２和ＣＨ３ＣＳＮＨ２三种化学试剂对表面本征层重掺杂层（ｓｉｎ＋）结构的ＧａＡｓ样品进行了钝化,利用光调制反射谱观察到许多个ＦｒａｎｚＫｅｌｄｙｓｈ振荡,测量出本征层的电场强度,研究了ＧａＡｓ表面硫钝化前后费米能级的变化,并且比较了各种钝化方法的钝化效果．     

基于新型广义位移的箱形梁扭转单元及应用

为了改进变截面连续箱梁桥的扭转分析理论,将截面总扭转角分解为自由翘曲扭转角和约束剪切扭转角,选取自由翘曲转角扭率作为广义位移,提出一个2节点8自由度的扭转梁段单元。从约束扭转控制微分方程出发,推导单元刚度矩阵及等效节点荷载列阵。引入应力增大系数,以反映约束扭转对初等梁应力的增大效应。数值算例验证了本文梁段单元的可靠性。最后对一个三跨变截面连续箱梁桥进行分析,结果表明,双力矩影响线与弯矩影响线较为类似,按双力矩影响线进行最不利荷载加载时最大应力值偏小;应力增大系数在集中荷载作用截面出现极值,均发生在腹板与顶板交点处;利用偏载放大系数来考虑扭转附加效应时,不宜考虑弯曲正应力较小及翘曲正应力出现极值的梁段区域。     

A pure spin-current injector of semiconductor quantum dots with Andreev reflection and Rashba spin-orbit coupling

We propose a four-terminal device consisting of two parallel quantum dots with Rashba spin-orbit interaction (RSOI), coupled to two side superconductor leads and two common ferromagnetic leads, respectively. The two ferromagnetic leads and two quantum dots form a ring threaded by Aharonov-Bohm (AB) flux. This device possesses normal quasiparticle transmission between the two ferromagnetic leads, and normal and crossed Andreev reflections providing conductive holes. For the appropriate spin polarization of the ferromagnetic leads, RSOI and AB flux, the pure spin-up (or spin-down) current without net charge current in the right lead, which is due to the equal numbers of electrons and holes with the same spin-polarization moving along the same direction, can be obtained by adjusting the gate voltage, which may be used in practice as a pure spin-current injector.     

无线传感器网络中面向紧急信息可靠传输协议

在无线传感器网络的监测领域,紧急信息的可靠传输成为关键问题。该文研究了面向紧急信息可靠传输的特点,提出一种适用于无线传感器网络的紧急信息可靠传输协议。该协议采用全新的拥塞控制方式,将缓冲区队列长度与队列长度变化率相结合,并引入状态机对节点的拥塞程度进行评估。节点在本地计算其拥塞度,并以此对其工作状态进行划分,进而采用不同的速率、带宽调整策略。仿真结果表明,该协议保证了紧急信息的可靠传输。     

基于5G+MEC的电站行业专网部署方案研究

随着5G正式商用以及新基建对5G应用的大力推进,5G正快速融入工业、能源、医疗等各行各业,成为推动实体经济数字化、网络化、智能化转型升级的关键驱动。主要研究5G专网在发电站领域的部署方案,探讨如何将5G技术应用于电站生产、运维各环节,助力智慧电站建设。     

基于偏振控制的Sagnac环负系数微波光子滤波器

为了克服正抽头系数低通滤波的限制,满足光载无线通信(ROF)、无线通信等系统对带通滤波器的需要,提出了一种新的负系数带通微波光子滤波器结构。系统采用了一种偏振敏感的电吸收调制器,其横向电场(TE)和横向磁场(TM)方向上具有不同的调制系数,在小信号调制下仍为线性调制。通过旋转偏振控制单元的波片,改变其快轴与TE方向的夹角,可以得到任意偏振态的转换。当偏振控制单元由两个旋光方向相反的法拉第旋光片和一个1/2波片组合时实现了负系数滤波,和一个1/4波片组合时得到了正系数滤波。     

Load adaptive start-up scheme for synchronous boost DC-DC converter

This paper presents a load adaptive soft-start scheme through which the inductor current of the synchronous boost DC-DC converter can trace the load current at the start-up stage. This scheme effectively eliminates the inrush-current and over-shoot voltage and improves the load capability of the converter. According to the output voltage, the start-up process is divided into three phases and at each phase the inductor current is limited to match the load. In the pre-charge phase, a step-increasing constant current gives a smooth rise of the output voltage which avoids inrush current and ensures the converter successfully starts up at different load situations. An additional ring oscillator operation phase enables the converter to start up as low as 1.4 V. When the converter enters into the system loop soft-start phase, an output voltage and inductor current detection methods make the transition of the phases smooth and the inductor current and output voltage rise steadily. Effective protection circuits such as short-circuit protection, current limit circuit and over-temperature protection circuit are designed to guarantee the safety and reliability of the chip during the start-up process. The proposed start-up circuit is implemented in a synchronous boost DC-DC converter based on TSMC 0.35μm CMOS process with an input voltage range 1.4-4.2 V, and a steady output voltage 5 V, and the switching frequency is 1 MHz. Simulation results show that inrush current and overshoot voltage are suppressed with a load range from 0-2.1 A, and inductor current is as low as 259 mA when the output shorts to the ground.