Knowledge Processing Method of Fault Diagnosis Expert Systems for Letter Sorting Equipment

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A Very Fast Method for the DC Analysis of Diode–Transistor Circuits

The paper offers a universal method for finding a unique or multiple DC operating points of nonlinear circuits. The developed method is based on the theory known as a linear complementarity problem (LCP) and the homotopy concept. It is a combination of Lemke’s method for solving LCP and some variant of the homotopy method. To express the problem of finding DC operating points in terms of LCP, an appropriate piecewise–linear approximation of diode characteristic is proposed. Although the method does not guarantee finding all the DC operating points, usually it finds them. The method is very fast and remarkably efficient. Numerical examples, including practical BJT and CMOS circuits having a unique or multiple DC operating points are given.     

Luminescence Properties of Cobalt-Doped ZnO Films Prepared by Sol–Gel Method

Pure ZnO and Co-doped ZnO films have been deposited on coverslip substrates by sol–gel spin coating. The morphological, structural, and optical properties of the films were investigated. The microstructure of the ZnO films became increasingly fine and the crystalline size decreased with Co doping. Analysis of x-ray diffraction (XRD) and Raman spectra reveals that Co²⁺ ions are substituted for Zn²⁺ ions in the ZnO lattice without changing its wurtzite structure. Co doping induces a decrease of the band-gap energy and fluorescence quenching of the emission bands. The spectra related to transitions within the tetrahedral Co²⁺ ions in the ZnO host crystal were observed in absorption and luminescence spectra. Photoluminescence (PL) spectra under different excitation energies and PL excitation spectra for the visible emissions suggest that the orange–red emission and green emission could be related to interstitial zinc (Zn_i) shallow donors and oxygen vacancy (V _O) deep donors, respectively. The red emission of Co-doped ZnO film could be assigned to the radiative transitions within the tetrahedral Co²⁺ ions in the ZnO host crystal after band-to-band excitation. A consistent explanation for the pure and Co-doped ZnO films is that the red emission under the excitation energy below the band gap is probably associated with extended Zn_i states.     

Dielectric and Optical Properties of CdS–Polymer Nanocomposites Prepared by the Successive Ionic Layer Adsorption and Reaction (SILAR) Method

The successive ionic layer adsorption and reaction (SILAR) method has been used to grow epitaxial CdS–polymer nanostructures as thin films with different surface morphology and particle size. The main purpose of the study was to investigate the dielectric properties and a.c. electrical conductivity (σ _a.c.), by a.c. impedance spectroscopy between 1 kHz and 1 MHz, at room temperature, of CdS–polymer nanocomposites produced by use of 2, 6, and 10 cycles of SILAR. The surface morphology and optical absorption of the samples were characterized by scanning electron microscopy (SEM) and UV–visible spectroscopy, respectively. Determination of the energy gaps of CdS–polymer nanocomposites prepared by use of different numbers of cycles of SILAR reveals that the band gap decreases with increasing number of cycles (J. Cryst. Growth 305, 175–180, 2007). This behavior is because of the growth of nanoparticles in the matrix materials, and can be explained by changes in the amount of confinement as a consequence of particle size variation. SEM images also confirm that different numbers of cycles lead to different morphology. Frequency-dependent dielectric properties and a.c. electrical conductivity of the samples prepared by use of different numbers of cycles of SILAR were investigated, and comparative studies on some electrophysical properties of the samples are reported. Experimental results show that values of the dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tanδ), the real (M′) and imaginary (M″) parts of electric modulus, and σ _a.c. are highly dependent on the frequency and the number of cycles. It can be concluded that changing the frequency and the number of cycles substantially alters both the dielectric properties and a.c. electrical conductivity of the samples.     

Enhanced of Blue and Green Emission by Ce–ZnO Thin Films Prepared by Sol–Gel Technique

Semiconductors - In this work, pure and cerium-doped ZnO thin films were synthesized on glass and silicon substrates via sol-gel spin-coating technique. Cerium (Ce) was incorporated with different...     

A Worst-Case Robust Combination Method of Beam-Forming and Orthogonal Space–Time Block Coding

In this paper, a new robust multi-input multi-output system is proposed in a perturbed wireless channel which is to model imperfect channel information at the source side when beam-forming and orthogonal space–time block coding is utilized. The channel perturbation is bounded by a predefined variation based on worst-case robust design. Beam-forming is used to improve the performance of the system expressed by the upper bound of pairwise error probability of symbols. In this paper firstly, the maximum value of pairwise error probability is obtained in a closed form when channel perturbation is kept below a threshold. Then the beam-forming matrix is designed to minimize the pairwise error probability subject to a predefined maximum transmitting power. This approach provides near optimal results due to using the upper bound of pairwise error probability. It shows good performance based on the symbol error rate criterion compared with other existing methods of the multiple input multiple output system.     

Microwave properties and applications of Y–Ba–Cu–O thin films grown on various substrates

Microwave properties of YBa₂Cu₃O_7-δ (YBCO) films grown on (100) LaAlO₃ (LAO), (110) NdGaO₃ (NGO) and (001) SrLaAlO₄ (SLAO) substrates were studied in the form of a microstrip ring resonator at temperatures above 20 K. The YBCO resonator on a SLAO substrate showed microwave properties better than or comparable to other YBCO resonators on LAO substrates. For the YBCO resonators on LAO and SLAO substrates, both Q_U and f₀ appeared to decrease as the temperature was raised. Meanwhile the resonator on a NGO substrate showed different behaviors with Q_U showing a peak at ∼70 K, which are attributed to the unique temperature dependence of the loss tangent of the NGO substrate. An X-band oscillator with a YBCO ring resonator coupled to the circuit was prepared and its properties were investigated at low temperatures. The frequency of the oscillator signal appeared to change from 7.925 GHz at 30 K to 7.878 GHz at 77 K, which was mostly attributed to the change in f₀ of the YBCO ring resonator. The signal power appeared to be more than 4.5 mW at 30 K and 2.1 mW at 77 K, respectively. At 55 K, the frequency of the oscillator signal was 7.917 GHz with the 3 dB-linewidth of 450 Hz.     

Effect of Eosin Y Dye on Electrical Properties of ZnO Film Synthesized by Sol–Gel Technique

This paper presents preparation of zinc oxide (ZnO) nanoparticles by the sol–gel technique. ZnO films were prepared by the doctor-blade method, and the resulting films were sensitized with eosin Y (EY) by immersing them in a solution of EY dye in ethanol. The prepared samples were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transmission infrared spectroscopy, and ultraviolet (UV)–visible spectroscopy. The monodispersed ZnO nanocrystals possess a wurtzite hexagonal structure with diameter of ～7 nm to 17 nm as observed by XRD and TEM analyses. The absorption spectrum of EY-dye-sensitized ZnO (ZnO/EY) film is slightly broadened, with a red-shift in the peak position compared with the absorbance spectrum of the dye in ethanol. Measurements of electrical parameters such as dark conductivity and photoconductivity were carried out at different temperatures. Transient photoconductivity was also studied at different temperatures to investigate the photoconduction mechanism. The photosensitivity of the ZnO/EY film is higher than that of the ZnO film. Hall measurements show n-type behavior for both samples. The visible absorption spectrum and high photosensitivity of the ZnO/EY films support their potential use as photoanode materials in dye-sensitized solar cells and optoelectronic devices.     

Generation of mm- and Sub mm-wave Bessel Beams Using DOE’s Designed by BOR-FDTD Method and MGA

A new way for generating Bessel beams at mm and sub mm-wavelengths is presented in this paper, in which diffractive optical elements (DOE’s) are designed for converting incident Gaussian beams into Bessel beams. In order to reduce the computational burden and therefore improve the design efficiency, two measures are adopted in our design. One is a body-of-revolution finite-difference time-domain (BOR-FDTD) method that uses a two-dimensional (2-D) solution space instead of a full 3-D space and thereby saves tremendous computational resources, and that is utilized to calculate the fields diffracted by the DOE’s. The other is a microgenetic algorithm (MGA) that has been proved to be more effective than the conventional GA, and that is employed for accelerative optimization. The utility of the present design tool, which combines a MGA with a BOR-FDTD method, is demonstrated by three examples. Numerical simulation results indicate that the designed DOE’s can not only flexibly generate zero- or higher- order Bessel beams when compared with axicons, but also have higher diffraction efficiencies when compared with amplitude holograms. An erratum to this article can be found at     

Model Development for Current–Voltage and Transconductance Characteristics of Normally-off AlN/GaN MOSHEMT

In this paper, an AlN/GaN-based MOSHEMT is proposed, in accordance to this, a charge control model has been developed analytically and simulated with MATLAB to predict the characteristics of threshold voltage, drain currents and transconductance. The physics based models for 2DEG density, threshold voltage and quantum capacitance in the channel has been put forward. By using these developed models, the drain current for both linear and saturation models is derived. The predicted threshold voltage with the variation of barrier thickness has been plotted. A positive threshold voltage can be obtained by decreasing the barrier thickness which builds up the foundation for enhancement mode MOSHEMT devices. The predicted I_d–V_gs, I_d–V_ds and transconductance characteristics show an excellent agreement with the experimental results and hence validate the model.     

Robust Fault Estimation and Accommodation for a Class of T–S Fuzzy Systems with Local Nonlinear Models

This paper focuses on the problems of fault estimation and accommodation for a class of T–S fuzzy systems with local nonlinear models and having an external disturbance and sensor and actuator faults, simultaneously. A fuzzy robust fault estimation observer is designed to estimate the system state and sensor and actuator faults. Compared with existing results, the observer not only is robust to the disturbance but also has a wider application range and more freedom for design. To compensate for the effect of faults and to stabilize the closed-loop system, an observer-based fault-tolerant controller is proposed. The separate design of the observer and controller avoids coupling between them. Finally, a simulation is conducted to demonstrate the effectiveness of the proposed method.     

Photodegradation of phenol and benzoic acid by sol–gel-synthesized alkali metal-doped ZnO

The effect of three alkali metal dopants on the photocatalytic properties of zinc oxide (ZnO) was investigated. Crystallized powders of ZnO doped with 10% lithium, sodium and potassium synthesized by a sol–gel process with zinc acetate and oxalic acid precursors were characterized by X-ray diffraction, scanning electron microscopy, UV–Vis diffuse reflectance and nitrogen adsorption isotherms. Photocatalytic activity under ultraviolet irradiation of undoped and doped ZnO powders was tested by degradation of phenol and benzoic acid, chosen as model organic pollutants. Doping ZnO with lithium, sodium and potassium increases the crystallinity of powders and reduces band gap energy. Comparison of photocatalytic activity of undoped and doped ZnO powders demonstrates that doping with sodium and lithium increases the efficiency of degradation of both phenol and benzoic acid.     

Structure and Magnetic Properties of the FeCo–C Films Reduced by Carbohydrates

Semiconductors - The structural and magnetic properties of FeCo–C films produced by electroless plating with different carbohydrates as reducing agents have been investigated. The surface...     

A New Learning Algorithm for the Fusion of Adaptive Audio–Visual Features for the Retrieval and Classification of Movie Clips

This paper presents a new learning algorithm for audiovisual fusion and demonstrates its application to video classification for film database. The proposed system utilized perceptual features for content characterization of movie clips. These features are extracted from different modalities and fused through a machine learning process. More specifically, in order to capture the spatio-temporal information, an adaptive video indexing is adopted to extract visual feature, and the statistical model based on Laplacian mixture are utilized to extract audio feature. These features are fused at the late fusion stage and input to a support vector machine (SVM) to learn semantic concepts from a given video database. Based on our experimental results, the proposed system implementing the SVM-based fusion technique achieves high classification accuracy when applied to a large volume database containing Hollywood movies.     

Stabilization of Discrete-time Fuzzy Systems Via Delta Operators and its Application to Truck–Trailer Model

This paper addresses the problem of robust \(L_2{-}L_\infty \) control in delta domain for a class of Takagi–Sugeno (TS) fuzzy systems with interval time-varying delays and disturbance input. In particular, the system under study involves state time delay, uncertainties and fast sampling period \(\mathcal {T}\). The main aim of this work was to design a \(L_2{-}L_\infty \) controller such that the proposed TS fuzzy system is robustly asymptotically stable with a \(L_2{-}L_\infty \) prescribed performance level \(\gamma >0\). Based on the proper Lyapunov–Krasovskii functional (LKF) involving lower and upper bound of time delay and free-weighting technique, a new set of delay-dependent sufficient conditions in terms of linear matrix inequalities (LMIs) are established for obtaining the required result. The result reveals that the asymptotic stability is achieved quickly when the sampling frequency is high. Finally, a numerical example based on the truck–trailer model is given to demonstrate the effectiveness and potential of the proposed design technique.     

Diffusion Growth Model of Doping—impurity Longitudinal Profile in Grown Material by MOCVD and Chloride VPE

The program process of the longitudinal impurity profile introduced in the quantum well(QW)laser and microwave electronic materials in analysed,based on the growth system by metalorganic chemical vapor deposition(MOCVD)and microwave electronic materials and chloride vapor phase epitaxy(VPE).The quantitative solution of the final longitudinal direction impurity distribution using the mathematical physics model of impurity carrier-gas transport drift and rediffusion in growth process was carried out.A technology for giving a reference to grown imputity profile of abrupt doping and uniform longitudinal direction based on the theory is presented.     

Effect of Heat Treatment on the Thermoelectric Properties of Bismuth–Antimony–Telluride Prepared by Mechanical Deformation and Mechanical Alloying

In this work, p-type 20%Bi₂Te₃–80%Sb₂Te₃ bulk thermoelectric (TE) materials were prepared by mechanical deformation (MD) of pre-melted ingot and by mechanical alloying (MA) of elemental Bi, Sb, and Te granules followed by cold-pressing. The dependence on annealing time of changes of microstructure and TE properties of the prepared samples, including Seebeck coefficient, electrical resistivity, thermal conductivity, and figure-of-merit, was investigated. For both samples, saturation of the Seebeck coefficient and electrical resistivity were observed after annealing for 1 h at 380°C. It is suggested that energy stored in samples prepared by both MA and MD facilitated their recrystallization within short annealing times. The 20%Bi₂Te₃–80%Sb₂Te₃ sample prepared by MA followed by heat treatment had higher a Seebeck coefficient and electrical resistivity than specimens fabricated by MD. Maximum figures-of-merit of 3.00 × 10^?3/K and 2.85 × 10^?3/K were achieved for samples prepared by MA and MD, respectively.     

A Wavelength Tunable DBR Laser Integrated with an Electro-Absorption Modulator by a Combined Method of SAG and QWI

We report a wavelength tunable electro-absorption modulated DBR laser based on a combined method of SAG and QWI.The threshold current is 37mA and the output power at 100mA gain current is 3.5mW.When coupled to a single-mode fiber with a coupling efficiency of 15%,more than a 20dB extinction ratio is observed over the change of EAM bias from 0 to -2V.The 4.4nm continuous wavelength tuning range covers 6 channels on a 100GHz grid for WDM telecommunications.