Productivity of coalbed methane wells in southern of Qinshui Basin

Based on regional CBM geological characteristics and drainage data of three typical Coalbed Methane(CBM)wells in the southern Qinshui Basin,history matching,productivity prediction and factor analysis of gas production control are conducted by using COMET3 reservoir modeling software.The results show that in the next 20 years,the cumulative and average daily gas production of the QN01 well are expected to be 800×104 m3 and 1141.1 m3/d,for the QN02 well 878×104 m3 and 1202.7 m3/d and97.5×104 m3 and 133.55 m3/d for the QN03 well.Gas content and reservoir pressure are the key factors controlling gas production in the area; coal thickness,permeability and porosity are less important; the Langmuir volume,Langmuir pressure and adsorption time have relatively small effect.In the process of CBM recovery,the material source and driving force are the key features affecting gas productivity,while the permeation process is relatively important and the desorption process has some impact on gas recovery.     

广西下巴铅锌矿床镉元素的富集规律研究

利用电子探针和等离子质谱(ICP-MS)分析手段,对下巴铅锌矿床中镉元素的分布特征进行分析研究,并探讨镉元素在矿床中的赋存方式。结果表明,该矿床铅锌矿化系列中的镉含量超过了其作为伴生有用组分的最低工业品位,矿床中镉元素主要赋存于闪锌矿中,与闪锌矿含量成正比关系。矿区范围内镉元素由南至北呈现出高—高—低的分布规律,在东西方向上,呈现出低—高—低的分布规律。研究结果认为海底热液与热卤水共同参与了下巴铅锌矿成矿作用,矿床成因类型可归为海底热液和热卤水混合型。     

A Hammerstein-type equalizer for concatenated fiber-wireless uplink

In optical fiber-based wireless access schemes, the radio signal is transmitted through fiber without frequency conversion radio-over-fiber (ROF). Although the fiber has adequate bandwidth, nonlinear distortion due to electrical to optical (E/O) conversion is a concern. In the uplink, the dynamic multipath wireless channel is followed by this static memoryless ROF link; this forms a Wiener system. In this paper, we propose a Hammerstein type decision feedback equalizer (HDFE) for the fiber-wireless uplink to combat the nonlinear distortion and the wireless channel dispersion. The proposed equalizer is less complex because it handles static and dynamic distortions separately. The nonlinear distortion is compensated first, reducing the power of cross modulation products significantly. Analytical results show that the lower bound of the mean squared error depends on the optical and wireless channel noise. The bit error rate (BER) performance of the HDFE for the nonlinear channel approaches the performance of a decision feedback equalizer (DFE) in a linear channel when the nonlinearity is adequately compensated.     

Broadband TDMA over the indoor radio channel

Prior work has focused on the negative aspects of time-dispersive channels and associated intersymbol interference. The authors show that the inherent diversity introduced by such dispersion is advantageous in reducing the performance-limiting effects of flat fading. This is demonstrated for an indoor QPSK radio link employing a decision-feedback equaliser     

Two-dimensional scattering from a multilayered periodic structure of arbitrary shapes

A numerical approach is presented to analyze the two-dimensional scattering properties from a multilayered periodic dielectric structure of an arbitrary number of arbitrarily shaped unit cells. The approach is enhanced by the periodic moment method, the lattice sums technique, and the Poisson summation formula. The matrix element's evaluation accounts for the overall coupling between layers. The choosing of lattice parameters allows designs for a wide range of applications, including the electromagnetic bandgap filtering of an E-polarized wave, which is simulated and reported here.     

Sum of arbitrarily correlated Gamma variates and performance of wireless communication systems over Nakagami-m fading channels

The probability density function (PDF) and the moment generating function (MGF) of a sum of squares of arbitrarily correlated, non-identically distributed Nakagami-m random variates, with non-identical and non-integer fading orders are derived. The authors proposed a simple method to determine a good truncation of the PDFs infinite sum and the associated truncation error. The derived results can be used to analyse a number of performance measures of diversity combining techniques in wireless communication systems over Nakagami-m fading channels.     

Rational function based predistorter for traveling wave tube amplifiers

A new scheme for the compensation of traveling wave tube amplifier nonlinearities is proposed and analyzed in this paper. The approach is based on rational function models of the amplifier AM-AM and AM-PM conversions. Amplitude and phase predistortion are performed separately. The phase predistortion is a function of the output of the amplitude predistortion part of the predistorter, instead of the input signal amplitude of the predistorter. Computer simulations reveal an improved performance compared to published techniques and suggest that with the proposed technique the transmit power amplifier can operate far into its nonlinear region. The transfer characteristics of the cascade of the amplifier and the proposed predistorter match the optimum transfer characteristics of a saturating device.     

A QRD-RLS-Based Predistortion Scheme for High-Power Amplifier Linearization

A digital baseband predistortion (PD) scheme for high-power amplifier (HPA) linearization is proposed and analyzed in this brief. The proposed approach utilizes the QR-decomposition-based recursive least squares (QRD-RLS) algorithm to estimate the memoryless complex polynomial coefficients that characterize the HPA. The inverse polynomial model coefficients corresponding to the PD are similarly extracted using QRD-RLS. The performance of the proposed PD scheme is analyzed via simulations and compared with previously published techniques. Results show that the QRD-RLS-based solution offers improved performance over its comparatives     

Iterative semiblind multiuser receivers for a space-time block-coded MC-CDMA uplink system

Iterative multiuser detection and space-time coding are two promising techniques to improve the capacity and performance of coded multiuser systems in wireless channels. In this paper, we present iterative multiuser detection schemes for a space-time block-coded multicarrier code-division multiple-access system with multiple transmit and receive antennas. We consider a more general case of an uplink system in the presence of both intra- and intercell interferences. We propose two types of iterative semiblind space-time receivers for such an uplink environment. The first is based on the minimum mean-square error criterion and the second is a hybrid scheme based on a combination of parallel interference cancellation and linear multiuser detection. These iterative receivers are derived, using a subspace approach, which utilizes known users' information for the computation of log-likelihood ratios (LLRs) while blindly suppressing the unknown interference. The LLRs are refined successively during the iterative process by using the extrinsic information available through decoding of all known users. A turbo code is used for channel coding. Simulation results in a frequency-selective Rayleigh-fading environment are presented to verify the performance of the proposed schemes.