任意长度数据窗幅频特性一致的正交相量滤波器设计

文中给出了一种新的相量滤波器的设计方法,该滤波器的实部和虚部函数具有一致的幅频特性和对基波信号的相位正交性,且滤波器数据窗长度的选择任意,有效地解决了短窗滤波器的设计问题,采用该方法设计的滤波器已用于高压微机继电保护装置,取得良好的运行效果。

双闭环正交相量锁相法的电网频率跟踪技术

在分析传统基于旋转坐标变换单相锁相环(single-phase locked loop,SPLL)原理的基础上,针对单相瞬时无功锁相法的正交相量模块,提出一种基于双闭环结构的正交相量的产生方法和瞬时无功锁相技术,对比分析二阶通用积分器构建正交相量的方法和基于双闭环产生正交向量方法的数学特性。通过仿真证明,基于两种不同正交向量产生方法的锁相锁频技术,基于双闭环结构的正交相量的瞬时无功锁频锁相技术能较好地解决电网电压幅值变化、电网电压相位变化、电网电压频率变化、电网电压含有谐波时对锁相的影响,该新型锁相法能够很好的跟踪电网频率,保证逆变器的稳定性。

A New Kind of k-Quantum Nonlinear Coherent States： Their Generation and PhysicalMeaning

A new kind of k-quantum nonlinear coherent states,i.e.,the k eigenstates of the k-th power~k (k≥3) of the generalized annihilation operator=1/f() of f-oscillators,are obtained and their properties are discussed.The completeness of the k states is investigated.An alternative method to construct them is proposed.It is shown that these states may form a complete Hilbert space,and all of them can be generated by a linear superposition of k Roy-type nonlinear coherent states.Physically,they can be generated by a linear superposition of the time-dependent Roy-type nonlinear coherent states at different instants.

Corporate Governance and Earnings Quality： The Experience of Listed Companies in Iran

This study examines the relationship among independent boards of directors, board size, managerial share ownership （MSO）, and earnings quality. The study of these relationships is controlled by firm size based on a sample of 114 companies listed on the Tehran Stock Exchange （TSE） for the period from 2008 to 2010. The results demonstrate that there was an insignificant positive relationship among independent boards of directors, managerial ownership, and earnings quality. Subsequent analysis shows an insignificant negative relationship between board size and earnings quality. It also provides evidence of the negative relationship between firm size as a control variable and earnings quality. This can be attributed to the fact that large firms are claimed to be politically sensitive and thus have the incentive to lessen variances in changes in their reported earnings.

Study on the Determination of Trace Ni(II) by the Catalytic Kinetic Spectrophotometric Method

A new kinetic spectrophotometric method has been developed for the determination of trace Ni （Ⅱ in natural water. The method is based on the catalytic effect of Ni （Ⅱ） on the oxidation of weak acid brilliant blue dye （RAWL） by KIO4 in acid medium. The concentration of nickel （Ⅱ） can be determined spectrophotometrically by measuring the decrease of absorbance of RAWL at λ = 626 nm using the fix-time method. The influencing factors are investigated by the orthogonal experimental design. The obtained optimum analytical conditions are： pH = 2.00, CRAWL = 5.00×10^-5 mol·L^-1, c KlO4 = 2.00× 10^-5 mol·L^-1, the reaction time t= 10min and the temperature T = 25 ℃. Under the optimum conditions, the developed method allows the measurement of Ni （Ⅱ） in a range of 0 - 40.0ngmL1. The standard deviation of eleven independent measurements of blank reaction is S = 3.08× 10^-3 and the limit of detection is 2.20ng·mL^-1. The relative standard deviations （RSDs） in six replicate determinations of 5 ngmL-1 and 8 ngmL1 Ni （Ⅱ） are 2.87% and 1.11%, respectively. Moreover, the experiments show few cations and anions can interfere with the measurement of Ni （Ⅱ）. The recovery efficiencies of this method are in a range of 97.0%-102.5% in freshwater samples. But there is a decreasing effect, which is about 0.2 times the added Ni （Ⅱ） in seawater medium. After reasonable calibration this processing method is used for the determination of Ni （Ⅱ） in seawater samples successfully. The results show this developed method has high accuracy and precision, high sensitivity, large range of linearity and high speed. The method can, therefore, be employed at room temperature.

Kinetic Adsorption of Ammonium Nitrogen by Substrate Materials for Constructed Wetlands

Constructed wetlands （CWs） are engineered systems that utilize natural systems including wetland vegetations, soils, and their associated microbial assemblages to assist in treating wastewater. The kinetic adsorption of ammonium nitrogen （NH＋-N） by CW substrate materials such as blast furnace slag （BFS）, zeolite, ceramsite, vermiculite, gravel, paddy soil, red soil, and turf, was investigated using batch experiments and kinetic adsorption isotherms. Both Freundlich and Lang- muir isotherms could adequately predict the NH＋-N adsorption process. The maximum adsorption capacities of NH＋-N, estimated from the Langmuir isotherm, ranked as： zeolite （33 333.33 mg kg^-1） 〉 turf （29274.01 mg kg^-1） 〉 BFS （5000 mg kg^-1） 〉 vermiculite （3333.33 mg kg^-1） 〉 gravel （769.23 mg kg^-1） 〉 paddy soil （588.24 mg kg^-1） 〉 red soil （555.56 mg kg^-1） 〉 ceramsite （107.53 mg kg^-1）. Some properties of the substrate materials, including bulk density, specific gravity, hydraulic conductivity, uniformity coefficient （K60）, curvature coefficient （Co）, organic matter, pH, exchangeable （or active） Cu, Fe, Zn and Mn, total Cu, and Fe, Mn, Zn, Cd, Pb and Ca, had negative correlations with NH＋-N adsorption. Other properties of the substrate materials like particle diameter values of D10, 030 and 060 （the diameters of particle sizes of a substrate material at which 10%, 30% and 60%, respectively, of the particles pass through the sieve based on the accumulative frequency）, cation exchange capacity （CEC）, exchangeable （or active） Ca and Mg, and total K and Mg had positive correlations with NH＋-N adsorption. In addition, active K and Na as well as the total Na had significant positive correlations with NH＋-N adsorption. This information would be useful for selection of suitable substrate materials for CWs.

Standard-independent I/Q imbalance estimation and compensation scheme in OFDM direct-conversion transceivers

Direct-conversion transceivers are gaining increasing attention due to their low power consumption. However, they suffer from a serious in- and quadrature-phase （I/Q） imbalance problem. The I/Q imbalance can severely limit the achievable operating signal-to-noise ratio （SNR） at the receiver and, consequently, the supported constellation sizes and data rates. In this paper, we first investigate the effects of I/Q imbalance on orthogonal frequency division multiplexing （OFDM） receivers, and then propose a new I/Q imbalance compensation scheme. In the proposed method, a new statistic, which is robust against channel distortion, is used to estimate the I/Q imbalance parameters, and then the I/Q imbalance is corrected in the frequency domain. Simulations are performed to verify the effectiveness of the proposed method for I/Q imbalance compensation. The results show that the proposed I/Q imbalance compensation method can achieve bit error rate （BER） performance close to that in the ideal case without I/Q imbalance in additive white Gaussian noise （AWGN） or multipath environments. Furthermore, because no pilot information is required, this method can be applied in various standard communication systems.

Experimental measurement of covariance matrix of two-mode entangled state

A two-mode entangled state was generated experimentally through mixing two squeezed lights from two optical parametric amplifiers on a 50/50 beam splitter.The entangled beams were measured by means of two pairs of balanced homodyne detection systems respectively.The relative phases between the local beams and the detected beams can be locked by using the optical phase modulation technique.The covariance matrix of the two-mode entangled state was obtained when the relative phase of the local beam and the detected beam in one homodyne detection system is locked and the other is scanned.This method provides a way by which one can extract the covariance matrix of any selected quadrature components of two-mode Gaussian state.