基于光子晶体光纤交叉敏感分离的磁场温度传感研究

提出了一种基于定向耦合效应和表面等离子共振效应的交叉敏感分离的磁场温度传感结构.在光子晶体光纤的一个特定空气孔中填充磁流体,利用磁流体的磁光效应和定向耦合效应形成磁场传感通道;在垂直方向的另一空气孔的内壁镀金纳米薄膜并填充甲苯液体,利用甲苯的温敏效应和表面等离子共振效应形成温度传感通道.对应输出谱出现两个损耗峰,测量损耗峰位置可以间接测出磁场强度和温度变化.通过理论计算()和结构优化,在90—270 Oe1 Oe=10~3/(4π) A/m范围内,磁场强度的灵敏度最高可达1.16 nm/Oe;在25—60?C范围内,温度的灵敏度可达-9.07 nm/?C.虽然填充的两种液体的折射率都受环境温度的影响,但通过建立灵敏度系数矩阵,可以消除磁场强度与温度的交叉敏感,实现磁场温度双参量的高灵敏度检测.     

Al原子在Pb基底上的沉积过程研究

利用分子动力学方法模拟了Al原子在Pb基底上的沉积过程. 对Al原子在Pb基底(001)面上沉积的形态与Pb原子在Al(001)基底上沉积的形态做了比较. 由于界面间势垒的不同, 两个体系界面间的形态有明显的差异. 分析了基底温度、基底晶面指向、沉积原子的入射动能对界面间原子混合的影响. 模拟结果显示: 随着基底温度升高, 基底原子的可移动性大大增加, 与沉积原子发生较大程度的混合; 入射能的改变对界面间原子的混合影响很小; 基底表面取不同的晶格指向时, 基底与沉积原子间的混合行为也有明显的不同. 利用径向分布函数分析了沉积原子的入射能对薄膜中原子排列有序性的影响. 较高入射能对应更有序的薄膜结构; 由径向分布函数的结构可以推测Al原子在Pb(001)基底表面沉积时界面间可能有金属间化合物生成. 关键词： Pb/Al体系 沉积过程 分子动力学 入射能     

Structural and optical investigation of nonpolar α-plane GaN grown by metalben organic chemical vapour deposition on r-plane sapphire by neutron irradiation

Nonpolar (1120) α-plane GaN films are grown by metal-organic chemical vapour deposition (MOCVD) on r-plane (1102) sapphire. The samples are irradiated with neutrons under a dose of 1 × 10¹⁵ cm^-2. The surface morphology, the crystal defects and the optical properties of the samples before and after irradiation are analysed using atomic force microscopy (AFM), high resolution X-ray diffraction (HRXRD) and photoluminescence (PL). The AFM result shows deteriorated sample surface after the irradiation. Careful fitting of the XRD rocking curve is carried out to obtain the Lorentzian weight fraction. Broadening due to Lorentzian type is more obvious in the as-grown sample compared with that of the irradiated sample, indicating that more point defects appear in the irradiated sample. The variations of line width and intensity of the PL band edge emission peak are consistent with the XRD results. The activation energy decreases from 82.5 meV to 29.9 meV after irradiation by neutron.     

各向异性作用下合金定向凝固界面稳定性的渐近分析

采用渐近分析方法对考虑了界面能各向异性的单相二元合金平界面定向凝固过程进行了线性稳定性分析，得到了特定条件下的零级、一级渐近解，并通过对长波段渐近解的讨论得出了适用于整个波段的色散关系.分析表明零级渐近解等效于成分过冷理论，而一级渐近解则与M-S稳定性理论一致.在稳定状态控制参数(抽拉速度和温度梯度)的选择图中，界面能各向异性增大了不稳定区域，且在高速和高温度梯度时的影响更强.     

宽截止窄带高反射滤光膜设计

窄带高反射滤光膜在光通讯、光学探测仪器等领域有着重要应用.探讨了"基片|H(LH)m1aL(HL)m2βCr,M|空气"膜系结构的窄带高反射滤光膜系,讨论了金属Cr层厚度,以及两种不同的匹配膜系对滤光膜特性的影响,计算了Cr层内部的电场分布.结果表明,较厚的金属层可实现更宽的截止带宽,匹配层的加入有效地实现了宽截止带的深截止,使中心波长处导纳为较大值的匹配膜系可以更好地实现滤光膜宽截止、窄带高反射特性;匹配膜层使中心波长处Cr层内部的电场强度趋于零,有效地降低了整个膜系的吸收,提高了反射率.     

Fabrication of urchin-like NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> microspheres assembled by using SDS as soft template for anode materials of Lithium-ion batteries

In this paper, the urchin-like NiCo₂O₄ microspheres assembled by using sodium dodecyl sulfate (SDS) as soft template are successfully fabricated by a facile procedure including microemulsion-solvothermal reaction and subsequent calcination at 400 °C for 4 h. The structure and morphology of synthesized NiCo₂O₄ particles are investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It has been clearly revealed that the prepared three-dimensional urchin-like NiCo₂O₄ microspheres are constituted by one-dimension nanowires. As it is applied to anode for lithium-ion batteries (LIBs), the initial coulombic efficiency is up to 75.7%, and the specific reversible capacity retains up to 1034.2 mAh/g even after 40 cycles at a current density of 100 mA/g. Furthermore, as the current density gradually increases to 800 mA/g, it still delivers the reversible capacity of 895.4 mAh/g. The high reversible specific capacity, perfect cyclability, and rate performance are attributed to the unique urchin-like NiCo₂O₄ microspheres, which can alleviate the volume expansion and shorten the diffusion path of ions and electrons during lithiation/delithiation process. The self-standing urchin-like NiCo₂O₄ microspheres may be a very promising candidate in place of the commercial graphite-based anode materials for high-performance LIBs.     

Characterization of Zn<Subscript>2</Subscript>SnO<Subscript>4</Subscript> Thin Films Prepared by RF Magnetron Sputtering

Zn₂SnO₄ (ZTO) is a stable semiconductor in ZnO–SnO₂ system and important transparent conducting oxide (TCO) predominantly used in optoelectronic devices. ZTO thin films were prepared by RF magnetron sputtering using Zn₂SnO₄ ceramic target in this paper. The effects of annealing temperatures and oxygen contents on characterization of ZTO thin films were studied. The results show that ZTO thin films prepared by RF magnetron sputtering are amorphous with an optical band gap of 3.22 eV. After annealing at 650°C in Ar atmosphere for 40 min, ZTO films possess a spinel structure with an optical band gap of 3.62 eV. The atomic force microscope (AFM) data of morphology reveals that the surface roughness of films is about 2 nm. The results of energy dispersive spectrometer (EDS) show that the concentration ratio of Zn to Sn is in the range from 1.44 to 1.57. The results of Hall-effect-measurement system reveal that the resistivity of films varies from 102 to 10–1 Ωcm, carrier concentration is about 10¹⁷ cm^–3, and mobility ranges from 10⁰ to 10¹ cm² v^–1 s^–1.     

Quantum Associative Neural Network with Nonlinear Search Algorithm

Based on analysis on properties of quantum linear superposition, to overcome the complexity of existing quantum associative memory which was proposed by Ventura, a new storage method for multiply patterns is proposed in this paper by constructing the quantum array with the binary decision diagrams. Also, the adoption of the nonlinear search algorithm increases the pattern recalling speed of this model which has multiply patterns to O( log₂^{2n -t} ) = O( n - t )O( {log_{2}}^{2^{n -t}} ) = O( n - t ) time complexity, where n is the number of quantum bit and t is the quantum information of the t quantum bit. Results of case analysis show that the associative neural network model proposed in this paper based on quantum learning is much better and optimized than other researchers’ counterparts both in terms of avoiding the additional qubits or extraordinary initial operators, storing pattern and improving the recalling speed.     

Design and analysis of coplanar waveguide optical modulator using finite element method

An analysis is given on the finite element method (FEM) for calculating the various parameters of optical modulators and a computer program is written to solve the finite element equation. Based on this method, a Mach-Zehnder type electro-optic modulator with coplanar waveguide (CPW) electrode is designed and fabricated. When compared with the Fourier series method, small differences on the 3-dB bandwidth, characteristic impedance and half-wave voltage, etc. are obtained.     

Depolarization in reentrant spin glasses: a comparison between neutron and muon probes

In the amorphous ( Fe_1-x Mn_x)₇₅ P₁₆ B_6 Al_3 alloys, muon and neutron depolarization data, combined with the results of small angle neutron scattering, magnetization and Mössbauer spectroscopy, probe the existence of three distinct magnetic transitions at T_C, T_K and T_F (T_F < _K < _C).