基于两相静止坐标系三相电压型PWM整流器控制策略的研究

本文研究了基于两相静止坐标系中的三相电压源型PWM整流器的控制方案,引入广义积分器实现三相电流在两相静止坐标系下跟踪控制。仿真结果证明了文中所提出的控制策略的有效性和可行性。     

基于两相静止坐标系三相电压型PWH整流器控制策略的研究

本文研究了基于两相静止坐标系中的三相电压源型PWM整流器的控制方案,引入广义积分器实现三相电流在两相静止坐标系下跟踪控制。仿真结果证明了文中所提出的控制策略的有效性和可行性。     

Modeling and Control of Six-Phase Symmetrical Induction Machine Under Fault Condition Due to Open Phases

This paper introduces a new fault-tolerant operation method for a symmetrical six-phase induction machine (6PIM) when one or several phases are lost. A general decoupled model of the induction machine with up to three open phases is given. This model illustrates the existence of a pulsating torque when phases are opened. Then, a new control method reducing the pulsating torque and the motor losses is proposed in order to improve the drive performances. The proposed method is compared to two other existing techniques. The simulation and experimental results obtained on a dedicated test-rig confirm the validity and the efficiency of the proposed method for a fault-tolerant symmetrical 6PIM drive.     

Computer Aided Analysis of Cell-Cycle Phase from Cytophotometric Histogram

A method for estimating, from cytophotometric data, the proportion of cells in three different phases of the cell cycle is proposed. Computation is done by means of determining seven parameters in the approximate function for the fluorescence intensity histogram. The proportion of cells in the GI, S, and G2-M phases, obtained by this method, was found to be reliable.     

La_（0．5）Sr_（0．5）CoO_3电极材料的制备与结构研究

采用化学共沉淀法合成了超细均匀的Ｌａ０．５Ｓｒ０．５ＣｏＯ３，复合氧化物粉末，并研究了合成粉末的特性和烧结体的结构特征。在１１００～１２００℃保温３ｈ烧成，可获得相对密度＞９６％的Ｌａ０．５Ｓｒ０．５ＣｏＯ３电极材料。Ｘ射线分析表明，Ｌａ０．５Ｓｒ０．５ＣｏＯ３烧结体的相组成主要为立方钙钛矿型结构，此外还有一些由氧空位造成的畸变钙钛矿型的四方相结构。     

A simple oscillator based on conservative models for generating three phase waveforms

The reliance on conservative models is a well-known step in the development of conventional oscillators in two phases. This paper demonstrates that conservative models can also serve for the development of sinewaves and other waveform generators in three phases.     

Degradation Behavior of 850 nm AlGaAs/GaAs Oxide VCSELs Suffered from Electrostatic Discharge

The effect of forward and reverse electrostatic discharge (ESD) on the electro‐optical characteristics of oxide vertical‐cavity surface‐emitting lasers is investigated using a human body model for the purpose of understanding degradation behavior. Forward ESD‐induced degradation is complicated, showing three degradation phases depending on ESD voltage, while reverse ESD‐induced degradation is relatively simple, exhibiting two phases of degradation divided by a sudden distinctive change in electro‐optical characteristics. We demonstrate that the increase in the threshold current is mainly due to the increase in leakage current, nonradiative recombination current, and optical loss. The decrease in the slope efficiency is mainly due to the increase in optical loss.     

A grammar compiler for connected speech recognition

A compiler for constructing optimized syntactic digraphs from easily written grammar specifications is described. These are written in a language called grammar specification language (GSL). The compiler has a preprocessing (macroexpansion) phase, a parse phase, graph code generation and compilation phases, and three optimization phases. Digraphs can also be linked together by a graph linker to form larger digraphs. Language complexity is analyzed in a statistics phase. It is demonstrated that the optimization phase yields graphs with even greater efficiency than previously achieved by hand. Some preliminary speech recognition results of applying these techniques to intermediate and large graphs are discussed. With the introduction of these tools it is now possible to provide a speech recognition user with the ability to define new task grammars in the field. GSL has been used by several untutored users with good results. Experience with GSL indicates that it is a viable medium for quickly and accurately defining grammars for use in connected speech recognition systems     

Allocation of resources for the Gaussian multiple access channel with practical partial cooperation

A Gaussian multiple access channel, with partial cooperation between sources, is considered. We develop an encoding scheme in which the transmission is carried out over three orthogonal time phases. The first two phases are exploited such that the two sources can practically and partially exchange their messages. In particular, each phase is terminated when each user can generate the other user’s codeword. Then, the two users can cooperatively transmit in the third phase. This formulation is used to (i) develop the achievable rate region, and (ii) numerically study the importance of each phase’s length and the allocated power to each user in the three characterized transmission phases.     

Research on structure of Cu2ZnSn(S, Se)4 thin films with high Sn-related phases

Cu2ZnSn(S, Se)4 (CZTSSe) thin films were deposited on flexible substrates by three evaporation processes at high temperature. The chemical compositions, microstructures and crystal phases of the CZTSSe thin films were respectively characterized by inductively coupled plasma optical emission spectrometer (ICP-OES), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman scattering spectrum. The results show that the single-step evaporation method at high temperature yields CZTSSe thin films with nearly pure phase and high Sn-related phases. The elemental ratios of Cu/(Zn+Sn)=1.00 and Zn/Sn=1.03 are close to the characteristics of stoichiometric CZTSSe. There is the smooth and uniform crystalline at the surface and large grain size at the cross section for the films, and no other phases exist in the film by XRD and Raman shift measurement. The films are no more with the Sn-related phase deficiency.     

Phase Correlation and Linewidth Reduction of 40 GHz Self-Pulsation in Distributed Bragg Reflector Semiconductor Lasers

In this paper, self-pulsation (SP) in a distributed Bragg reflector (DBR) semiconductor laser without a saturable absorber is experimentally and theoretically investigated. Detailed experimental characterizations of the SP DBR laser are reported in the optical and radio-frequency domains. Phase correlation between the longitudinal modes selected by the DBR mirror has been experimentally demonstrated. A theoretical model based on coupled rate equations for three modes has been developed to study the time evolution of phases and amplitudes of the modes. The carrier density modulation, resulting from the beating between adjacent longitudinal modes generates four-wave mixing (FWM) and is responsible for mutual injection locking, leading to passive mode-locking. The calculated power spectral density of the frequency noise derived from the model is in agreement with experimental results and proves that the phases of the longitudinal modes are identically correlated through the FWM process in this type of SP lasers     

Provisioning services on digital switching systems

The overall service provisioning process is functionally decomposed into three phases. The first is service negotiation, in which the customer's request is translated into machine-readable form (as a service order). The service order is the input to the second phase, assignment. If network resources are needed to satisfy the service request, the assignment process selects then from its inventory. The third phase is service activation. Attention is focused on the assignment phase, but emerging relationships among the three phases are also covered. The discussion begins with progress to date. Capabilities that have recently become available in Bellcore's operations systems using the flexible entity approach, are described. Issues and problems that arise as the switched network evolves to a greater degree of intelligence are considered, covering provisioning for ISDN, load balancing, service negotiation and assignment, customers doing their own provisioning, and physical and logical provisioning     

一种新的近场源三维参数联合估计方法

提出了一种新的近场源频率、波达方向和距离的三维参数联合估计算法.基于阵列接收数据的高阶累积量,构造了三个适当的矩阵束,它们的广义特征值的相位给出频率、到达方向和距离的估计,同时其特征值的幅度实现三维参数的自动配对.该算法的参数估计有闭式解,无需复杂的搜索过程,且其参数自动配对.由于算法使用了四阶累积量,所以适用于任意结构的加性高斯噪声环境.计算机仿真实验证实了所给算法的有效性.     

Polymorphic transformations and thermal expansion in AgCuSe<Subscript>0.5</Subscript>(S,Te)<Subscript>0.5</Subscript> crystals

The high-temperature X-ray diffraction technique is used to study AgCuSe_0.5(S,Te)_0.5 crystals. It is shown that, at room temperature, the AgCuSe_0.5S_0.5 crystal is composed of Cu_1.96S and AgCuSe phases. At a temperature of 695 K, these phases transform into a single face-centered cubic (fcc) phase. The transformation is reversible. The AgCuSe_0.5Te_0.5 composition consists of three phases, specifically, Cu₂Te, AgCuSe, and a cubic phase. At 444 K, both orthorhombic phases simultaneously transform into a diamond-like cubic phase. In this transformation, the cubic phase plays the role of a seed. From the temperature dependence of the lattice parameters, the thermal-expansion coefficients of the phases involved in both compositions are calculated for the main crystallographic directions.     

Study of wavelength shift in InGaAs/InAlGaAs QW DFB lasers based onlaser parameters from a comparison of experiment and theory

Experimental data of InGaAs/InAlGaAs quantum well distributed feedback (DFB) lasers such as spectra, under continuous and pulsed biasing, relative intensity noise and linewidth, are compared with the results of model calculations based on a transfer matrix method. Using experimental data of different lasers, a set of physical DFB laser parameters was determined. We succeeded in describing all the experimental data of different lasers by the same set. The determined parameter set was further applied to study the influence of facet properties on the wavelength shift of DFB lasers. We found a very strong dependence of the wavelength tunability on the end facet phases. The wavelength shift varies by a factor up to three between different end facet phases and coatings. This is crucial for the yield of, for example, tunable multisection DFB lasers with an envisaged large tuning range     

通用可组合的三方口令认证密钥交换协议

现有的许多三方口令认证密钥交换(3PAKE)协议都被发现是不安全的。该文基于通用可组合(UC)模型,定义了3PAKE理想函数。在两方口令认证密钥交换理想函数辅助的混合模型下,构造了一个实现3PAKE理想函数的3PAKE协议。新的协议由中间密钥生成、消息认证传输和会话密钥生成3个阶段构成。该协议是UC安全的,并且结构简单。     

激光制造中同轴粉末流动量和质量传输

激光制造同轴粉末/载流气体两相流中存在动量、质量和能量传输等物理过程,它们直接决定激光制造的质量和精度.重点报道国内外粉末流中动量和质量输运方面的综合研究结果:提出了激光同轴送粉二相流物理模型;根据气体/固体两相流理论建立了动量质量传输方程,开发了基于FLUENT的计算机模拟专用软件;建立了基于DPIV(Digital Particle Image Veloeimetry)的气体/金属粉末两相流的速度场和浓度场检测方法,开发了图像处理专用软件;完成了气体/金属粉末两相流的速度场和浓度场的数值模拟和试验检测.结果表明:理论模拟和试验检测结果基本一致.     

Temperature Dependence of Growth Mechanism for Nanoscale High T_c Superconductors

The growth mechanisms of high temperature Yttrium- and Bismuth-based-superconductors were investigated at nanoscale. We started with studying the growth relationships among the three phases of Bi-2201, Bi-2212, and Bi-2233, and then extended to another growth mechanism of Bi-2223 and the growth of yttrium-based high-temperature nanosuperconductors （nano-YBCO）. A time dependence of growth experiment was performed. In this experiment, the Bi-based superconductors grew within different sintering periods, and its three phases were determined by X-ray diffraction. And then, a time dependence of growth model was suggested to explain the experimental facts. With this model, governing equations were derived to quantitatively describe the growth and decomposition mechanisms during sintering period. The results calculated from the derived equations were well in agreement with the experimental data. We also suggested an alternative growth mechanism for the Bi-2223 phase, which was supported by an observation of transmission electron microscopy （TEM）. The nano-YBCO also grew, and their orthorhombic crystal structures were determined by the TEM. The superconducting properties of Bi-2223 were investigated by the measurements of ac magnetic susceptibility. It is expected that the derived equations will fit the alternative experimental growth mechanism of the Bi-2223 phase and the nano-YBCO growth mechanism, too.     

Er<Subscript>2</Subscript>O<Subscript>3</Subscript> for high-gain waveguide amplifiers

Following the demonstration of room-temperature luminescence, Er₂O₃ has been explored as a high-gain medium for ultra-compact waveguide amplifiers. With sputtered and annealed films, we measure three radiative lifetimes (7 ms, 0.8 ms, and 0.5 ms) and upconversion coefficients at 4.2 K. We have correlated these measurements with three crystalline phases: the thermodynamically stable bcc phase and the metastable fcc and hcp phases. The 7-ms lifetime is correlated with the fcc phase, implying the metastable crystal state has a profound influence on inhibiting upconversion interaction between neighbor Er atoms. Measurements indicate optical gain >3 dB/cm is possible.     

Logic drive circuit for 3-phase charge-coupled devices

A simple logic circuit is escribed which acts as a modulo-3 ring counter and provides three driving phases suitable to operate a 3-phase c.c.d. The circuit is driven by a clock, the rate of which corresponds to three times the desired element rate in the c.c.d. The pulsewidth of the clock determines the amount of mutual overlap between subsequent phases. An additional gating input permits stopping the counter in a predetermined state, such as would be required to switch a c.c.d. into the integration mode. The circuit contains only 12 gates, and when implemented with a t.t.l. high-speed logic component runs up to input clock rates of 50 MHz.