Study on the dispersion characteristic of the plasma-loaded relativistic BWO

The dispersion characteristic of the plasma-loaded relativistic backward wave oscillator has been analyzed. The theoretical model has been established and the numerical calculations accord with the experimental results, which provides some useful suggestions on the designing of slow-wave structure of BWO.     

Comparison of two novel MRAS based strategies for identifying parameters in permanent magnet synchronous motors

Two model reference adaptive system (MRAS) estimators are developed for identifying the parameters of permanent magnet synchronous motors (PMSM) based on the Lyapunov stability theorem and the Popov stability criterion, respectively. The proposed estimators only need online measurement of currents, voltages, and rotor speed to effectively estimate stator resistance, inductance, and rotor flux-linkage simultaneously. The performance of the estimators is compared and verified through simulations and experiments, which show that the two estimators are simple, have good robustness against parameter variation, and are accurate in parameter tracking. However, the estimator based on the Popov stability criterion, which can overcome parameter variation in a practical system, is superior in terms of response speed and convergence speed since there are both proportional and integral units in the estimator, in contrast to only one integral unit in the estimator based on the Lyapunov stability theorem. In addition, the estimator based on the Popov stability criterion does not need the expertise that is required in designing a Lyapunov function.     

改进k-means 算法在电信CRM 客户分类中的应用

电信市场的竞争在于客户的竞争,为了在激烈的竞争中保持优势,必须将客户进行细分,针对不同的客户,研究出相应的营销策略．K-means算法能对大型数据集进行高效分类,但对“噪声”敏感,聚类结果不准确,本文对该算法进行改进,使其能够实现更加准确和全面的客户细分．     

一种同构、非同构布局模式构造算法

给出了一种基于完全关联图的准确构造同构、非同构布局模式的算法,并给出了其计算复杂度及适应范围.与李广强等（2003）的布局模式构造方法相比较表明,本算法能构造准确布局模式,适用范围较广,计算复杂度低,前者为O（n^3）,本文为O（n）,O（n^2）或O（n^3）.     

基于DSP平台的动态无功补偿装置的设计

本文针对电力系统巾无功补偿装置的现状,分析了无功补偿装置的原理,指出动念无功补偿是对系统参数准确洲量的基础建立的.应用了快速FFT运算原理消除谐波对测量结果的影响.同时与DSP技术结合,设计了一种带电网监测的动态无功补偿装置.采用TI公司的TMSL2407 DSP作为主控制器,该装置能对电网中各项数据进行实时监测,实现了电容器的快速、无过渡投切.同时在满足无功补偿前提下,防止误动作,可有效的避免重大事故的发生.     

Cross-sectional investigation of radiation damage of 2 MeV proton-irradiated silicon carbide

Cross-sectional investigation is an important method to study ion irradiation effects in the depth direction. In this study, 2 Me V H~+was implanted in 6 H-SiC single crystals to investigate the effects of light ion irradiation on SiC. Raman spectroscopy and scanning electronic microscopy(SEM) were carried out on crosssectional samples to reveal the in-depth damage states and dopant behavior. The most damaged region is a little shallower than that predicted by the SRIM procedure,owing to the uncertainty in SRIM simulations. Layered structures representing zones of varying damage after2 MeV H ion irradiation are clearly observed. Two bands are observed in SEM images, of which on band corresponds to the damage peak, while the other band at the end of the H ion-affected area is probably a result of H diffusion propelled by a hydrogen-rich layer during irradiation.A charge accumulation effect related with conductivity on the sample surfaces during SEM tests is observed in theH-implanted area. A model is proposed to explain these phenomena.     

Facile solvothermal synthesis of a graphene nanosheet-bismuth oxide composite and its electrochemical characteristics

This work demonstrates a novel and facile route for preparing graphene-based composites comprising of metal oxide nanoparticles and graphene. A graphene nanosheet-bismuth oxide composite as electrode materials of supercapacitors was firstly synthesized by thermally treating the graphene-bismuth composite, which was obtained through simultaneous solvothermal reduction of the colloidal dispersions of negatively charged graphene oxide sheets in N,N-dimethyl formamide (DMF) solution of bismuth cations at 180 °C. The morphology, composition, and microstructure of the composites together with pure graphite oxide, and graphene were characterized using powder X-ray diffraction (XRD), FT-IR, field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), thermogravimetry and differential thermogravimetry (TG-DTG). The electrochemical behaviors were measured by cyclic voltammogram (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS). The specific capacitance of 255 F g⁻¹ (based on composite) is obtained at a specific current of 1 A g⁻¹ as compared with 71 F g⁻¹ for pure graphene. The loaded-bismuth oxide achieves a specific capacitance as high as 757 F g⁻¹ even at 10 A g⁻¹. In addition, the graphene nanosheet-bismuth oxide composite electrode exhibits the excellent rate capability and well reversibility.     

Optimum block-adaptive learning algorithm for errorback-propagation networks

An optimum block-adaptive learning rate (OBALR) backpropagation (BP) algorithm for training feedforward neural networks with an arbitrary number of neuron layers is described. The algorithm uses block-smoothed gradient as direction for descent and no momentum term, but produces an optimum block-adaptive learning rate which is constant within each block and is updated adaptively at the beginning of each block iteration so that it is kept optimum in a sense of minimizing the approximate output mean-square error of the block. Several computer simulations were tested on learning a deterministic chaos time-series mapping. The OBALR BP algorithm not only overcame the difficulty in choosing good values of the two parameters, but also provided significant improvement on learning speed and descent capability over the standard BP algorithm     

用于PCB微切片清洗的高压开关电源

依据在低气压下由辉光放电产生等离子体的方法,开发了一种用于PCB微切片清洗的等离子体清洗机的高压开关电源。该高压开关电源采用脉宽调制集成电路TL494作为电源的核心控制电路。文章围绕TL494对高压开关电源系统的整体设计及使用作出了详细的介绍。