适用于任意几何结构平面阵列的无网格DOA估计算法

由于在网格失配情况下依然具备良好的估计性能,无网格DOA估计算法近年来受到了广泛的关注与研究,其中又以基于原子范数最小化(ANM)的DOA估计算法最具代表性。随着可分离ANM(DANM)算法的提出,为ANM理论在2维DOA估计领域中的应用提供了可能。不过传统的DANM算法以及其后续的一系列改进算法都只适用于均匀矩形阵列(URA)或稀疏矩形阵列(SRA),无法适用于具有任意几何结构的平面阵列。针对上述问题,该文提出一种适用于任意几何结构平面阵列的无网格DOA估计算法,即B-DANM算法。该算法利用一类贝塞尔函数对实际平面天线阵列接收信号的协方差数据进行展开,从而获得适用于任意几何结构平面阵列的DANM算法框架,然后再通过求解半定规划问题、Toeplitz矩阵的Vandermonde分解以及估计参数配对、角度变换等过程来得到最终的DOA估计结果。仿真实验验证了,在任意几何结构平面阵列的测向系统中,B-DANM算法相比于传统的2维DOA估计算法在精度、分辨力等方面的优势。     

Mobile Oriented Future Internet (MOFI):Architectural Design and Implementations

With the recent growth in smartphone services, the “mobile” environment has become a key factor to consider in the design of the future Internet. In this paper, we propose Mobile‐Oriented Future Internet (MOFI), which is a new architecture for the future Internet for mobile‐oriented environments. The MOFI architecture is designed with three functional features: global identifier and local locator in the identifier‐locator separation, query‐first data delivery for route optimization, and distributed control of identifier‐locator mapping. The proposed architecture and functional operations are implemented and tested using the Linux platform. From the experiment results, we see that the MOFI architecture performs better than the existing identifier‐locator separation schemes, such as Proxy Mobile IP and Host Identity Protocol, in terms of data throughout, mapping control overhead, and handover delay.     

含运算放大器的一阶电路时间常数的计算

时间常数是一阶动态电路分析中的一个重要参数。而含运算放大器的一阶电路时间常数的计算又是学习中的难点。本文采用了经典法、外加电源计算和电路等效三种求解手段讨论含运算放大器的一阶电路时间常数的计算。并针对含运算放大器的一阶电路的三种基本情况,详细介绍了零电流支路开路和等电位点之间短路这两种电路等效手段的应用,展示了电路等效变换在求解此类问题时的便捷之处。     

空位缺陷金红石型TiO2电子结构和光学性质的理论研究

基于密度泛函理论(DFT)的第一性原理模守恒赝势 方法,对纯金红石型TiO₂和Ti、O两种空位缺 陷相的几何结构、能带结构、态密度(DOS)以及光学性质进行了 系统地对比研究。结果发现,含有空 位缺陷的TiO₂键长增大,原子布局值减小并出现微弱的磁性;空位缺陷导致导带变窄,导 带和价带 都向低能级方向移动,由空位原子贡献的载流子增强了体系的电导率,费米能级上移进入导 带;与 纯金红石型TiO₂的直接带隙宽度(3.0eV)相比较,Ti空位缺陷相转 变为P型半导体且直接带隙为1.816 eV,而O空位缺陷相转变为n型半导体且间接带隙为1.961eV。同时, 两种空位缺陷结构的介电峰显 著红移,折射率有明显变化,对可见光区的吸收系数均比纯TiO₂高。与O空位结构相比,Ti 空位结构的 介电常数、折射率、消光因子和对可见光的吸收强度更大,更能增强电子在低能端的光学跃 迁,具有更佳的可见光催化性能。     

基于Nios II和“北斗”一代的气象灾害预警信息接收终端设计

为了解决广大偏远山区气象灾害预警信息接收的“盲区”和供电困难的问题,提出一 种基于Nios II和“北斗”一代的气象灾害预警信息接收终端设计方案。采用Altera公司Cyc lone系列的EP1C12Q240和一体化的“北斗”一代射频单收芯片RNC2410,有效降低了终端的 成本、体积与功耗。同时利用Nios II软核处理器,通过软件设计实现终端正确接收预警信 息和报警。该方法已成功运用于山区洪灾与泥石流频发地区预警信息的接收。     

Halide Double‐Perovskite Light‐Emitting Centers Embedded in Lattice‐Matched and Coherent Crystalline Matrix

Through first‐principles calculations, it is found that two lattice‐matched halide double‐perovskites, Cs₂NaBiBr₆ and Cs₂AgBiBr₆, have a type‐I band alignment and can form highly miscible alloys in which the disordering makes the bandgaps become direct and activates the direct transition from the valence to conduction band edge, leading to a strong optical absorption and high radiative recombination rate. The bandgaps of the alloys are tunable in a wide range of 1.93–3.24 eV, while the lattice constants remain unchanged. This advantage inspires the design of a coherent crystalline matrix based on Cs₂(Na,Ag)BiBr₆ alloys, in which the Ag‐rich and narrower‐bandgap regions are embedded in the Na‐rich and wide‐bandgap region with lattice‐matched and coherent interfaces. The type‐I band alignment drives the photogenerated excitons into the narrower‐bandgap Ag‐rich regions, so the regions become light‐emitting centers with a high photoluminescence quantum yield (PLQY). The bandgaps of the Ag‐rich regions are tunable, so the color of emitted light can be adjusted, making a broadband emission possible. Such kind of coherent crystalline matrix with high‐PLQY and broadband emission can also be fabricated based on the alloys of other lattice‐matched halide double‐perovskites, demonstrating the flexibility of band structure engineering in the coherent heterostructures of various halide double‐perovskites.     

多功能一体化雷达任务调度算法研究

雷达、电子战、通信等多功能电子系统一体化是雷达的发展方向之一,资源管理与调度技术是一体化雷达的关键技术。针对基于孔径分割实现雷达、电子对抗、通信等多种功能的一体化系统的任务调度问题,对系统任务建模、调度算法设计、算法评价指标进行了探讨。在研究常规相控阵雷达调度策略的基础上,提出了采用多任务并行EDF(Earliest Deadline First)算法来实现系统的自适应调度。最后对比常规多功能雷达的自适应调度进行了仿真比较,且对仿真结果进行了定量分析,结果表明采用多任务并行EDF(MTPEDF)算法的基于孔径分割的一体化雷达系统具有一定的优越性。     

硅纳米管结构和电子性质的第一性原理研究

基于密度泛函理论的第一性原理方法,在广义梯度近似下,研究了(5,0)和(5,5)硅纳米管结构和电子性质。计算结果表明:(5,0)管硅原子相邻键长波动范围为0.068 nm,大于(5,5)管的0.006 nm;通过对(5,0)管的分波态密度进行分析发现,其3s电子和2p电子能量分布在-13～3 eV,但2p电子集中分布在能量较高的-6～3 eV,出现了明显的sp3轨道杂化。同时对(5,0)和(5,5)硅纳米管最高占据轨道和最低未占据轨道的能隙进行了分析,发现两种管导电性能与结构的手性相关,锯齿型(5,0)管能带交叠具有明显的金属性,而扶手型(5,5)管能隙为0.151 eV是半导体纳米管。     

台槽刻蚀对埋栅型静电感应晶体管特性的影响

对埋栅型SIT,为切断栅极和源极（或阴极）之间在外延过程中形成的连体,打开栅电极区,进行外延后的台面刻蚀,对台面刻蚀的深度和形状进行研究;为消除栅墙外划片边界造成的各种寄生效应,在有源区的外面挖深槽,以保证栅源击穿发生在内部、实现击穿接近理论值。对先刻蚀台面还是先刻蚀槽的问题做了实验对比,结果发现先台后槽更有利于器件特性的改善。     

Blind Source Separation of Instantaneous Mixture of Delayed Sources Using High‐Order Taylor Approximation

This paper deals with the problem of blind source separation (BSS), where observed signals are a mixture of delayed sources. In reference to a previous work, when the delay time is small such that the first‐order Taylor approximation holds, delayed observations are transformed into an instantaneous mixture of original sources and their derivatives, for which an extended second‐order blind identification (SOBI) approach is used to recover sources. Inspired by the results of this previous work, we propose to generalize its first‐order Taylor approximation to suit higher‐order approximations in the case of a large delay time based on a similar version of its extended SOBI. Compared to SOBI and its extended version for a first‐order Taylor approximation, our method is more efficient in terms of separation quality when the delay time is large. Simulation results verify the performance of our approach under different time delays and signal‐to‐noise ratio conditions, respectively.