H6 Non-isolated Full Bridge Grid-connected PV Inverters With Low Leakage Currents

为满足非隔离光伏并网发电系统对共模漏电流的限制，提出一种六开关逆变器拓朴（H6拓扑）。所提出的H6拓扑在功率传输模态时，进网电流半个工频周期流过3支开关管，而另半个工频周期流过2支开关管，故相对于H5拓扑，降低了通态损耗，有利于热应力均衡，且仍满足续流阶段光伏电池输出端与电网脱离的要求。详细分析拓扑的工作原理，并推论给出H6非隔离光伏并网逆变器的其它3种拓扑结构；比较分析了H5拓扑、Heric拓扑和H6拓扑的损耗和成本。通过1kW通用样机平台对比验证了上述3种拓扑的效率和共模特性。实验结果表明，H6拓扑的变换效率高于H5拓扑、但略低于Heric拓扑，共模特性优于Heric拓扑、但略劣于H5拓扑。

Preparation and characterization of high photoactive TiO_2 catalyst using the UV irradiation-induced sol-gel method

High photoactive TiO2 catalyst was prepared using the sol-gel method through UV irradiation during the formation stage of nuclei. The surface morphology and microstructure of the prepared catalyst were characterized using scanning electron microscopy （SEM）, X-ray diffraction patterns （XRD）, and Fourier transform infrared spectroscopy （FF-IR）. The photoactivity was evaluated by the degradation of methylene blue. The results show that the photocatalysis of the prepared catalyst is higher than that of conventional heat-treated particles. The higher photoactivity is a combined result of favorable microstructure, appropriate hydroxyl groups, and active sites of Ti^3＋ ions on the surface of TiO2. It is concluded that the ultraviolet irradiation-induced sol-gel method is an effective method to enhance the photocatalysis of TiO2.

Fabrication, annealing, and electrocatalytic properties of platinum nanoparticles supported on self-organized TiO_2 nanotubes

The platinum nanoparticles supported on self-organized TiO2 nanotubes （Pt-TiO2/Ti） were prepared using electrochemical anodic oxidation followed by cathodic reduction. The structure and chemical nature of the Pt-TiO2/Ti electrocatalyst were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. Both XRD and SEM results indicate the presence of platinum on nanotubular TiO2. The stability of the Pt deposits was also investigated in 0.5 mol/L H2SO4 solution by cyclic voltammetry. The electrocatalytic activity of the Pt-TiO2/Ti catalyst exhibits enhancement effect during electro-oxidation of methanol when annealed to anatase. Successive cyclic voltam- mograms of methanol oxidation on the Pt-TiO2/Ti electrocatalyst shows unique electrocatalytic characteristics when compared to methanol oxidation on the bulk Pt catalyst. This is because of further quick oxidation of adsorbed CO by Pt （111） facets of Pt particles on self-organized TiO2 nanotubes when the formation of an electroactive film onto the working catalyst surface occurs.

Preparation and crystalline phase of a TiO_2 porous film by anodic oxidation

Anatase titanium dioxide is an active photocatalyst, but it is difficult to immobilize on the substrate. A crystalline TiO2 porous film was prepared directly on the surface of pure titanium by anodic oxidation in this work. Constant voltage and constant current anodic oxidation were adopted with sulphuric acid used as the electrolyte, pure titanium as the anode and copper as the cathode. The morphology and structure of the porous film on the substrate were analyzed with the aid of Field Emission Scanning Electron Microscopy （FESEM） and X-ray Diffraction （XRD）. The effects of the parameters of anodic oxidation （such as voltage, the concentration of sulphuric acid, anodization time and current density） on the aperture and the crystalline phase of the TiO2 porous film were systematically investigated. The results indicate that the increase of current density facilitates the augment of the aperture and the generation of anatase and mille. In addition, the forming mechanism of anatase and mille TiO2 porous films was discussed.

RESEARCH ON THE BISTATIC FORWARD-LOOKING SAR IMAGING

The bistatic Synthetic Aperture Radar (SAR) systems with separate transmitter and receiver antennas provide a new potential to imaging in the forward-looking geometry. Analysis of the Doppler property in this paper indicates the feasibility of Bistatic Forward-Looking (BFL) SAR imaging. Considering the different Doppler property determined by the two platforms in BFL SAR, a new 2-D point target spectrum is derived in our study. Based on the spectrum, an imaging method is chosen for the configuration, and the point target simulation validates the analysis.

MULTI-INVARIANCE ESPRIT-LIKE ALGORITHMS FOR COHERENT DOA ESTIMATION

Estimation of Signal Parameters via Rotational Invariance Technique(ESPRIT) algorithm can estimate Direction-Of-Arrival(DOA) of coherent signal,but its performance can not reach full satisfaction.We reconstruct the received signal to form data model with multi-invariance property,and multi-invariance ESPRIT algorithm for coherent DOA estimation is proposed in this paper.The proposed algorithm can resolve the DOAs of coherent signals and performs better in DOA estimation than that of ESPRIT-like algorithm.Meanwhile,it identifies more DOAs than ESPRIT-like algorithm.The simulation results demonstrate its validity.

POWER REFLECTION AND TRANSMISSION IN BEAM STRUCTURES CONTAINING A SEMI-INFINITE CRACK

Wave reflection and transmission in a beam containing a semi-infinite crack are studied analytically based on Timoshenko beam theory., Two kinds of crack surface conditions： non-contact （open） and fully contact （closed） cracks, are considered respectively for an isotropic beam. The analytical solution of reflection and transmission coefficients for a semi-infinite crack is obtained. The power reflection and transmission ratios depend on both the frequency and the position of the crack. Numerical results show the conservation of power transport. The transmitted energy among various wave modes is also investigated. A finite element method is used to verify the validity of the analytical results.

Solution precision of concrete temperature fields with finite difference method

With the finite difference method to calculate the temperature distribution in mass concrete structures, the solution precision will increase with a smaller step size, at the cost of computational time. In view of the basic characteristics of the finite difference method, a simple yet powerful improvement is introduced. By multiplying the adiabatic temperature function with a correction factor, the precision of the solution can be assured without an increase in the computation time. In addition, the correction rules for three types of commonly used concrete hydration formulas are investigated.

Texture Analysis and Characteristic Identification About Plaque Tissues of IVUS

Intravascular ultrasound can provide clear real-time cross-sectional images,including lumen and plaque.In practice,to identify the plaques tissues in different pathological changes is very important.However,the grayscale differences of them are not so apparent.In this paper a new textural characteristic space vector was formed by the combination of Co-occurrence Matrix and fraction methods.The vector was projected to the new characteristic space after multiplied by a projective matrix which can best classify those plaques according to the Fisher linear discriminant.Then the classification was completed in the new vector space.Experimental results found that the veracity of this classification could reach up to 88%,which would be an accessorial tool for doctors to identify each plaque.

Optimal Placement of Active Members in Truss Adaptive Structures

The mathematical model of optimal placement of active members in truss adaptive structures is essentially a nonlinear multi-objective optimization problem with mixed variables. It is usually much difficult and costly to be solved. In this paper, the optimal location of active members is treated in terms of （0, 1） discrete variables. Structural member sizes, control gains, and （0, 1） placement variables are treated simultaneously as design variables. Then, a succinct and reasonable compromise scalar model, which is transformed from original multi-objective optimization, is established, in which the （0, 1） discrete variables are converted into an equality constraint. Secondly, by penalty function approach, the subsequent scalar mixed variable compromise model can be formulated equivalently as a sequence of continuous variable problems. Thirdly, for each continuous problem in the sequence, by choosing intermediate design variables and temporary critical constraints, the approximation concept is carried out to generate a sequence of explicit approximate problems which enhance the quality of the approximate design problems. Considering the proposed method, a FORTRAN program OPAMTAS2.0 for optimal placement of active members in truss adaptive structures is developed, which is used by the constrained variable metric method with the watchdog technique （CVMW method）. Finally, a typical 18 bar truss adaptive structure as test numerical examples is presented to illustrate that the design methodology set forth is simple, feasible, efficient and stable. The established scalar mixed variable compromise model that can avoid the ill-conditioned possibility caused by the different orders of magnitude of various objective functions in optimization process, therefore, it enables the optimization algorithm to have a good stability. On the other hand, the proposed novel optimization technique can make both discrete and continuous variables be optimized simultaneously.

Reaction zone characterization of counter-flow diffusion flame with diluted and preheated reactants

Reaction zone characteristics were studied using hydroxy radical planar laser-induced fluorescence （OH-PLIF） technique for a counter-flow preheated （CH4＋N2）/（Air＋N2） diluted diffusion flames. The effects of preheat temperature and dilute ratio on the reaction zone characteristics were investigated by demonstrating the OH intensity distribution and reaction zone thickness from OH-PLIF images. Under the experimental conditions of constant cold flow velocity, the results show that the OH intensity and reaction zone thickness decrease with the increase of dilute ratio at constant preheat temperature and increase with preheat temperature at fixed dilute ratio. The OH maximum intensity shifts towards the ＂lean＂ side of counter flow at constant preheat temperature, and it shifts towards the fuel side with the increase of dilute ratio of fuel stream and towards the oxidizer side with the increase of dilute ratio of oxidizer stream respectively. The feasibility of OH as a reaction zone marker in this diluted combustion is verified further. The variation of diffusion and chemical reaction rate of reactants due to preheat and dilution contributes to the reaction zone characteristics simultaneously. The effect of strain on the flame reaction zone should be included in the future work.

BLIND SIGNAL SEPARATION OF LINEAR MIXTURE USING TRILINEAR DECOMPOSITION

This paper introduces a new source separation technique exploiting the time coherence of the source signals. The proposed approach relies only on stationary second order statistics. Blind Signal Separation (BSS) method using trilinear decomposition is proposed in this paper. Simulation results reveal that our proposed algorithm has the better blind signal separation performance than joint diagonalization method. Our proposed algorithm does not require whitening processing. Moreover, our proposed algorithm works well in the underdetermined condition, where the number of sources exceeds than the number of sensors.

PARALLEL ADAPTIVELY MODIFIED CHARACTERISTIC BASIS FUNCTION METHOD BASED ON STATIC LOAD BALANCE

Characteristic Basis Function Method (CBFM) is a novel approach for analyzing the ElectroMagnetic (EM) scattering from electrically large objects. Based on dividing the studied object into small blocks, the CBFM is suitable for parallel computing. In this paper, a static load balance parallel method is presented by combining Message Passing Interface (MPI) with Adaptively Modified CBFM (AMCBFM). In this method, the object geometry is partitioned into distinct blocks, and the serial number of blocks is sent to related nodes according to a certain rule. Every node only needs to calculate the information on local blocks. The obtained results confirm the accuracy and efficiency of the proposed method in speeding up solving large electrical scale problems.

Environment-Friendly Determination of Low Concentration Azobenzene β-Cyclodextrin-Modified Electrode

Objective To study environment-friendly determination of azobenzene in trace amounts using β-cyclodextrin （β-CD）-modified Au electrode. Methods β-CD-modified Au electrode was fabricated with a two-step approach, and then a gold electrode modified with β-CD was used to detect azobenzene by employing Osteryoung square wave voltammetry. Results The modified electrode could detect azobenzene, showing a good linearity between the electrochemical current and concentration. Conclusion Although the electrochemical current is related with concentration, the detection limit is around 1 .0 ×10^-10 mol/L. This study may provide a new environment-friendly approach for monitoring water quality.

PARTIALLY BLIND EXTRACTION OF CONTINUOUS CHAOTIC SIGNALS FROM A LINEAR MIXTURE

In this paper, we address the problem of blind extraction and separation of a continuous chaotic signal from a linear mixture consisting of some chaotic signal and/or random signals. The problem of blind extraction is firstly formulated as a problem of the synchronization-based parameter estimation. Then an efficient least square based parameter estimation method is introduced to determine the desired extracting vector. The proposed blind signal extraction scheme is applicable to blind separation of chaotic signals by formulating the separation problem as the extraction of each chaotic source. Numerical simulation shows that the proposed approach can blindly extract and separate the desired chaotic signals and it is also robust to measurement noise.

A NOVEL NULLING ALGORITHM IN THE SUBARRAY OF A LARGE ARRAY

Forming nulls in the radiation pattern of an antenna is to suppress the interference from certain di- rections or to cancel desired signals. This letter presents an effective method based on the Gram-Schmidt or- thogonal algorithm for forming nulls in the subarray of a large array. The theory and realizing methods are discussed, and the corresponding formulas are derived in details. The simulation results are given to demon- strate the feasibility, the availability and the quick-convergence of the presented method.

HIGH-PERFORMANCE SIMPLE-ENCODING GENERATOR-BASED SYSTEMATIC IRREGULAR LDPC CODES AND RESULTED PRODUCT CODES

Low-Density Parity-Check (LDPC) code is one of the most exciting topics among the coding theory community.It is of great importance in both theory and practical communications over noisy channels.The most advantage of LDPC codes is their relatively lower decoding complexity compared with turbo codes,while the disadvantage is its higher encoding complexity.In this paper,a new ap- proach is first proposed to construct high performance irregular systematic LDPC codes based on sparse generator matrix,which can significantly reduce the encoding complexity under the same de- coding complexity as that of regular or irregular LDPC codes defined by traditional sparse parity-check matrix.Then,the proposed generator-based systematic irregular LDPC codes are adopted as con- stituent block codes in rows and columns to design a new kind of product codes family,which also can be interpreted as irregular LDPC codes characterized by graph and thus decoded iteratively.Finally, the performance of the generator-based LDPC codes and the resultant product codes is investigated over an Additive White Gaussian Noise (AWGN) and also compared with the conventional LDPC codes under the same conditions of decoding complexity and channel noise.

MULTI-BLOCK CHAINING-BASED AUTHENTICATION MODE

A fast authentication mode based on Multi-Block Chaining (MBC) is put forward; and its security is proved. The MBC mode is for new generation block cipher algorithms. Its speed is about 13% faster than that of the authentication modes in common use (for example, cipher block chaining-message authentication code mode). The dependence test results meet the requirement. The MBC mode is complete; its degree of ava-lanche effect is about 0.9993; its degree of strict avalanche criterion is 0.992 or so. The frequency test results indicate that the output generated by the MBC mode has uniformity. The binary matrix rank test results imply that it is linear independent among disjoint sub-matrices of the output. Maurer’s universal statistical test results show that the output could be significantly compressed without loss of information. Run test, spectral test, non-overlapping template matching test, overlapping template matching test, Lempel-Ziv compression test, linear complexity test, serial test, approximate entropy test, cumulative sums test, random excursions test and random excursions variant test results fulfill the requirements of all. Therefore the MBC mode has good pseudo-randomness. Thus the security of MBC mode is verified by the way of statistical evaluation.