基于空时自适应处理的机载机控阵雷达子阵结构研究

由于实际的杂波谱随距离呈现一定的非均匀性，相应地要求ＳＴＡＰ处理器在俯仰上也应具有可控自由度．文中以６４×１２ 正侧面矩形阵为例，比较了在总的空域自由度一定的条件下，３ 种子阵结构ＳＴＡＰ的性能．研究结果表明，当空域自由度在阵面的水平和垂直方向上（与距离对应）合理分配时，ＳＴＡＰ处理器能够自适应抑制与距离有关的强杂波，使整体剩余杂波加噪声功率下降２～３ ｄＢ。

相控阵雷达干扰抑制的子阵结构

本文考虑的问题是在子阵波束形成的多功能相控阵雷达中应如何配置自适应干扰抑制,并且还考虑了旁瓣对消器和子阵级的最佳处理方法。子阵级的最佳处理从其工作性能和实际应用来看具有很显著的优点。本文主要讨论如何配置子阵的问题。

一种大规模发射阵列的稀布方法

为了提高大规模发射阵列的优化效率和降低大规模发射阵列的散热压力,提出了一种基于子阵和交替迭代的大规模发射阵列稀布阵方法。首先给出了大规模发射阵列基本子阵结构的确定原则,接着建立基于基本子阵结构的优化模型,之后交替迭代地对基本子阵结构的中心位置进行优化,在优化过程中各基本子阵结构的中心位置的移动总是使得发射阵列方向图函数的最大旁瓣最小。仿真实验表明,提出的大规模发射阵列稀布阵方法能够较快地收敛到较优的结果。

基于相对拟牛顿法的自卫式欺骗干扰抑制算法

自卫式欺骗干扰与目标信号高度相似,且二者的到达角完全相同,传统的主瓣干扰抑制算法难以对其进行抑制。针对该问题,文中在极化单输入多输出(PSIMO)雷达系统下,提出一种基于相对拟牛顿法的盲源分离算法。该算法利用干扰和目标的极化特性差异,通过构建重叠子阵结构计算出联合自相关矩阵,并采用相对拟牛顿法估计出分离矩阵,从而将目标和干扰信号分离在不同的通道上,实现干扰抑制作用。仿真实验结果表明,该算法能够有效抑制自卫式欺骗干扰,且在低信噪比(SNR)和密集干扰场景下依然具有良好的干扰抑制性能,当输入SNR为-10 dB时,输出的目标检测概率仍可以达到51.6%,拥有较强的鲁棒性。

Structure of Hamiltonian Matrix and the Shape of Eigenfunctions：Nuclear Octupole Deformation Model

The structure of a Hamiltonian matrix for a quantum chaotic system, the nuclear octupole deformation model, has been discussed in detail. The distribution of the eigenfunctions of this system expanded by the eigenstates of a quantum integrable system is studied with the help of generalized Brillouin?Wigner perturbation theory. The results show that a significant randomness in this distribution can be observed when its classical counterpart is under the strong chaotic condition. The averaged shape of the eigenfunctions fits with the Gaussian distribution only when the effects of the symmetry have been removed.

Notes on Quantitative Structure-Properties Relationships （QSPR） Part Four： Quantum Multimolecular Polyhedra, Collective Vectors, Quantum Similarity, and Quantum QSPR Fundamental Equation

The nature and origin of a fundamental quantum QSPR （QQSPR） equation are discussed. In principle, as any molecular structure can be associated to quantum mechanical density functions （DF）, a molecular set can be reconstructed as a quantum multimolecular polyhedron （QMP）, whose vertices are formed by each molecular DF. According to QQSPR theory, complicated kinds of molecular properties, like biological activity or toxicity, of molecular sets can be calculated via the quantum expectation value of an approximate Hermitian operator, which can be evaluated with the geometrical information contained in the attached QMP via quantum similarity matrices. Practical ways of solving the QQSPR problem from the point of view of QMP geometrical structure are provided. Such a development results into a powerful algorithm, which can be implemented within molecular design as an alternative to the current classical QSPR procedures.

Studies on the Second-Order Nonlinear Optical Properties of Parabolic andSemi-parabolic Quantum Wells with Applied Electric Fields

Within the framework of compact density matrix approach and iterative procedure, a detailed procedure for the calculation of the second-harmonic generation (SHG)susceptibility tensor is given in the electric-field-biased parabolic and semi-parabolic quantum wells (QWs). The simple analytical formula for the SHG susceptibility in the systems is also deduced. Numerical results on typical AlGaAs/GaAs materials show that, for the same effective width,the SHG susceptibility in semi-parabolic QW is larger than that in parabolic QW due to the self-asymmetry of the semiparabolic QW, and the applied electric field can make the SHG susceptibilities in both systems enhance remarkably.Moreover, the SHG susceptibility is also related to the parabolic confinement frequency and the relaxation rate of the systems.

Kinetics-controlled growth SnO2 nanorod arrays for superior rate performance of aligned mesocrystalline lithium-ion batteries with

A general method for facile kinetics-controlled growth of aligned arrays of mesocrystalline SnO2 nanorods on arbitrary substrates has been developed by adjusting supersaturation in a unique ternary solvent system comprising acetic acid, ethanol and water. The hydrolysis processes of Sn（IV） as well as the nucleation and growth of SnO2 crystals were carefully controlled in the mixed solvents, leading to an exclusively heterogeneous nucleation on a substrate and the subsequent growth into mesocrystalline nanorod arrays. In particular, aligned arrays of hierarchically structured, [001]-oriented mesocrystalline SnO2 nanorods with four {110} lateral facets can be readily grown on Ti foil as well as many other inert substrates such as fluoride-doped tin oxide （FTO）, Si, graphite, and polytetrafluoroethylene （Teflon）. Due to the unique combination of the mesocrystalline structure and the one-dimensional nanoarray structure, the obtained mesocrystalline SnO2 nanorod arrays grown on metallic Ti substrate exhibited an excellent rate performance with a high initial Coulombic efficiency of 65.6% and a reversible capacity of 720 mA.h/g at a charge/discharge rate of 10 C （namely, 7,820 mA/g） when used as an anode material for lithium-ion batteries.

GaN-based LEDs for light communication

Rapid improvement in the efficiency of GaN-based LEDs not only speed up its applications for general illumination, but offer the possibilities for data transmission. This review is to provide an overview of current progresses of GaN-based LEDs for light communications. The modulation bandwidth of GaN-based LEDs has been first improved by optimizing the LED epilayer structures and the modulation bandwidth of 73 MHz was achieved at the driving current density of 40 A/cm2 by changing the multi-quantum well structures. After that, in order to increase the current density tolerance, different parallel flip-chip micro-LED arrays were fabricated. With a high injected current density of ~7900 A/cm2, a maximum modulation bandwidth of ~227 MHz was obtained with optical power greater than 30 mW. Besides the increase of carrier concentrations, the radiative recombination coefficient B was also enhanced by modifying the photon surrounding environment based on some novel nanostructures such as resonant cavity, surface plasmon, and photonic crystals. The optical 3 dB modulation bandwidth of GaN-based nanostructure LEDs with Ag nanoparticles was enhanced by 2 times compared with GaN-based nanostructure LEDs without Ag nanoparticles.Our results demonstrate that using the QW-SP coupling can effectively help to enhance the carrier spontaneous emission rate and also increase the modulation bandwidth for LEDs, especially for LEDs with high intrinsic IQE. In addition, we discuss the progress of the faster color conversion stimulated by GaN-based LEDs.

Integrated ionic sieving channels from engineering ordered monolayer two-dimensional crystallite structures

Atomically thin solid-state channels enabling selective molecular transport could potentially be used in a variety of separation and energy conversion applications.The density of channels,their height,distance and edge structure are the key factors that dramatically impact the selective transport performance.However,such channels with small constrictions and atomic precision have been limited to proof-ofconcept demonstrations based on microscale two-dimensional(2D)crystal stripes.Here,we report the engineering of highly ordered,scalable monolayer graphene crystallite arrays by chemical vapor deposition(CVD)method with a modified anisotropic etching approach.The size,shape,distance and edge structure of the graphene crystallite arrays in a large area could be delicately controlled through tailoring the synthetic parameters.This array structure can act as pillars to prop up a smooth single-crystal graphene film,and the fabricated integrated angstrom-size(3.4A)channels allow water transport but exclude hydrated ions,demonstrating potential in selective ionic sieving and nanofiltration practice.

Coaxial Si/anodic titanium oxide/Si nanotube arrays for lithium-ion battery anodes

Silicon （Si） has the highest known theoretical specific capacity （3,590 mAh/g for Li1.5Si4, and 4,200 mAh/g for Li22Si4） as a lithium-ion battery anode, and has attracted extensive interest in the past few years. However, its application is limited by poor cyclability and early capacity fading due to significant volume changes during lithiation and delithiation processes. In this work, we report a coaxial silicon/anodic titanium oxide/silicon （Si-ATO--Si） nanotube array structure grown on a titanium substrate demonstrating excellent electrochemical cyclability. The ATO nanotube scaffold used for Si deposition has many desirable features, such as a rough surface for enhanced Si adhesion, and direct contact with the Ti substrate working as current collector. More importantly, our ATO scaffold provides a rather unique advantage in that Si can be loaded on both the inner and outer surfaces, and an inner pore can be retained to provide room for Si volume expansion. This coaxial structure shows a capacity above 1,500 mAh/g after 100 cycles, with less than 0.05% decay per cycle. Simulations show that this improved performance can be attributed to the lower stress induced on Si layers upon lithiation/delithiation compared with some other recently reported Si-based nanostructures.

Optical fiber sensor by cascading long period fiber grating with FBG for double parameters measurement

An optical fiber sensor for strain and temperature measurement based on long period fiber grating(LPFG) cascaded with fiber Bragg grating(FBG) structure has been proposed and realized both theoretically and experimentally. Theoretical analysis shows that two microstructures with similar sensitivities cannot be used for double parameters measurement. The LPFG is micromachined by the CO_2 laser, and the FBG is micromachined by the excimer laser. For the validation and comparison, two FBGs and one LPFG are cascaded with three transmission valleys, namely FBG1 valley at 1 536.3 nm, LPFG valley at 1 551.2 nm, and FBG2 valley at 1 577.3 nm. The temperature and strain characteristics of the proposed sensor are measured at 45—70 °C and 250—500 με, respectively. The sensitivity matrix is determined by analyzing wavelength shifts and parameter response characterization of three different dips. The proposed optical fiber sensor based on LPFG cascaded with FBG structure can be efficiently used for double parameters measurement with promising application prospect and great research reference value.

The Brillouin zones and band gaps of a two-dimensional phononic crystal with parallelogram lattice structure

We present a detailed theoretical study on the acoustic band structure of two-dimensional （2D） phononic crystal. The 2D pho- nonic crystal with parallelogram lattice structure is considered to be formed by rigid solid rods embedded in air. For the circu- lar rods, some of the extrema of the acoustic bands appear in the usual high-symmetry points and, in contrast, we find that some of them are located in other specific lines. For the case of elliptic rods, our results indicate that it is necessary to study the whole first Brillouin zone to obtain rightly the band structure and corresponding band gaps. Furthermore, we evaluate the first and second band gaps using the plane wave expansion method and find that these gaps can be tuned by adjusting the side lengths ratio R, inclined angle 0 and filling fraction F of the parallelogram lattice with circular rods. The results show that the largest value of the first band gap appears at θ=90° and F--0.7854. In contrast, the largest value of the second band gap is at θ=60° and F=0.9068. Our results indicate that the improvement of matching degree between scatterers and lattice pattern, ra- ther than the reduction of structural symmetry, is mainly responsible for the enhancement of the band gaps in the 2D phononic crystal.