Single-electron coherence: Finite temperature versus pure dephasing

We analyze a coherent injection of single electrons on top of the Fermi sea in two situations, at finite-temperature and in the presence of pure dephasing. Both finite-temperature and pure dephasing change the property of the injected quantum states from pure to mixed. However, we show that the temperature-induced mixedness does not alter the coherence properties of these single-electron states. In particular two such mixed states exhibit perfect antibunching while colliding at an electronic wave splitter. This is in striking difference with the dephasing-induced mixedness which suppresses antibunching. On the contrary, a single-particle shot noise is suppressed at finite temperatures but is not affected by pure dephasing. This work therefore extends the investigation of the coherence properties of single-electron states to the case of mixed states and clarifies the difference between different types of mixedness.     

Novel stability criteria for fuzzy Hopfield neural networks based on an improved homogeneous matrix polynomials technique

The global stability problem of Takagi-Sugeno(T-S) fuzzy Hopfield neural networks(FHNNs) with time delays is investigated.Novel LMI-based stability criteria are obtained by using Lyapunov functional theory to guarantee the asymptotic stability of the FHNNs with less conservatism.Firstly,using both Finsler’s lemma and an improved homogeneous matrix polynomial technique,and applying an affine parameter-dependent Lyapunov-Krasovskii functional,we obtain the convergent LMI-based stability criteria.Algebraic properties of the fuzzy membership functions in the unit simplex are considered in the process of stability analysis via the homogeneous matrix polynomials technique.Secondly,to further reduce the conservatism,a new right-hand-side slack variables introducing technique is also proposed in terms of LMIs,which is suitable to the homogeneous matrix polynomials setting.Finally,two illustrative examples are given to show the efficiency of the proposed approaches.     

Enhanced luminescence of Tb by efficient energy transfer from Ce in Sr2B5O9Cl host

Ce³⁺ and Tb³⁺ co-doped Sr₂B₅O₉Cl phosphors with intense green emission were prepared by the conventional high-temperature solid-state reaction technique. A broad band centered at about 315 nm was found in phosphor Sr₂B₅O₉Cl: Ce³⁺, Tb³⁺ excitation spectrum, which was attributed to the 4f-5d transition of Ce³⁺. The typical sharp line emissions ranging from 450 to 650 nm were originated from the ⁵D₄ → ⁷F_J (J = 6, 5, 4, 3) transitions of Tb³⁺ ions. The photoluminescence (PL) intensity of green emission from Tb³⁺ was enhanced remarkably by co-doping Ce³⁺ in the Tb³⁺ solely doped Sr₂B₅O₉Cl phosphor because of the dipole-dipole mechanism resonant energy transfer from Ce³⁺ to Tb³⁺ ions. The energy transfer process was investigated in detail. In light of the energy transfer principles, the optimal composition of phosphor with the maximum green light output was established to be Sr_1.64Ce_0.08Tb_0.1Li_0.18B₅O₉Cl by the appropriate adjustment of dopant concentrations. The PL intensity of Tb³⁺ in the phosphor was enhanced about 40 times than that of the Tb³⁺ single doped phosphor under the excitation of their optimal excitation wavelengths.     

H基于模糊观测器参数摄动的耦合时空混沌H跟踪控制

由于子系统的时空耦合作用及参数的摄动性，实现参数摄动的耦合时空混沌的跟踪控制非常困难。然而模型未知的耦合时空混沌的每个子系统可由一系列模糊逻辑模型逼近，每个模糊逻辑模型代表子系统在特定运行点的局部线性化模型，同时考虑子系统状态的不可测性，采用模糊观测器来估计子系统的状态。基于模糊模型及状态观测器，计及混沌参数的摄动性，提出一种模糊跟踪控制方案，实现了参数摄动的耦合时空混沌的鲁棒跟踪控制，并将模糊跟踪控制表征为线性矩阵不等式问题，用线性矩阵不等式的凸优化方法求解控制器参数，确保系统的全局渐近稳定性。仿真验证了方案的有效性。     

ICP等离子体鞘层附近区域发光光谱特性分析

为了独立控制鞘层附近区域离子密度和离子能最分布,采用光发射谱(OES)测量技术,对不同射频功率、放电气压和基底偏压下感应耦合等离子体鞘层附近区域辉光特性进行了研究.原子谱线和离子谱线特性分析表明,在鞘层附近区域感应耦合等离子体具有较高的离子密度和较低的电子温度.改变放电气压和射频功率,对得到的光谱特性分析表明,鞘层附近区域离子密度随射频功率的增大而线性增大,在低压下随气压的升高而增大.低激发电位原子谱线强度增加迅速,高激发电位原子谱线强度增加缓慢,而离子谱线强度增加很不明显.改变基底直流偏压,对得到的发射光谱强度变化分析表明,谱线强度随基底正偏压的增加而增大.随着基底负偏压的加入,谱线强度先减小而后增大;直流偏压为-30 V时,光谱强度最弱.快速离子和电子是引起Ar激发和电离过程的主要能量来源.     

Novel stability and stabilization criteria for Takagi-Sugeno fuzzy time-delay systems

We study the problems of stability and stabilization for Takagi-Sugeno(T-S) fuzzy time-delay systems.First,by constructing a less-redundant Lyapunov-Krasovskii function and introducing a useful inequality,an innovative stability criterion is obtained,which gives a significant improvement on the performance.Compared with the exiting references,our result can use fewer unknown variables and get better results.Furthermore,based on the derived stability criteria,a new stabilization condition is developed,in which the controller gain and the maximum allowable delay bound can be obtained simultaneously.The conditions are all derived in the form of linear matrix inequality,which are easy to verify.Finally,numerical examples are given to show the effectiveness of the proposed methods.     

Comparison of single and multiple scattering approaches for the simulation of limb-emission observations in the mid-IR

The validity of single scattering radiative transfer calculations for simulation of limb-emission measurements of clouds in the mid-infrared spectral region was investigated by comparison with a multiple scattering model. For in limb direction optically thin clouds, like polar stratospheric clouds, errors of the single scattering scheme range below 3%. For optically thick clouds deviations are below 3% in case of low single scattering albedo (ω₀=0.24) increasing up to 10-30% for ω₀=0.84. Clouds which are optically thick in limb, but thin in nadir direction, can cause limb radiances which are by a factor of 1.7 higher than the blackbody radiance at cloud altitude.     

High-performance optics for thermal microscopy

We have developed a thermal microscope which has an InSb detector and optics optimized for the camera. Using this system, we evaluated maximum resolution of a 30×/numerical aperture 0.71 lens made of silicon and germanium, and achieved the cutoff frequency of around 300 line pairs/mm, which is almost a diffraction-limited performance. The thermal microscope is installed on the THEMOS-1000, a product of Hamamatsu Photonics, for thermal emission analysis.     

带有锥形孔的复合变幅杆设计及动态分析

在超声振动拉丝加工过程中,为了实现线材的顺利拉拔,需要应用带有锥形孔的复合变幅杆。为此,本文基于等效四端网络与传输矩阵法,建立了带锥形孔圆锥变幅杆的传输矩阵,推导出带锥形孔圆锥过渡复合变幅杆的频率方程的一般公式。根据推导出的频率方程,应用区间搜索法和牛顿迭代法获取了准确的数值解,实现了该复合变幅杆的纵向振动。之后,应用有限元软件Ansys对设计出的复合变幅杆分别进行模态分析和动力学特性分析,获得了各段不同长度下复合变幅杆谐振频率、放大系数以及最大应力值的变化规律。最后,对制造出的复合变幅杆进行阻抗与振动性能测试,结果表明其频率准确,且振幅比较稳定。