4G移动通信系统及其与3G系统的比较研究

首先介绍了第四代移动通信系统(4G)的定义、技术特征,探讨了4G与超3G、WiMax的关系,然后对4G和3G的体系结构、系统参数、关键技术、移动性管理和安全策略等进行了比较研究,对4G的研究和建设具有一定的参考价值。     

稠油底水油藏地质研究及水平井调整实践

我国东部油田由于受沉积环境的影响,油藏类型大部分为复杂断块油藏,物性差,非均质性强.羊三木油田三断块NgI油组是一个复杂断块稠油底水油藏,投入开发近30年,目前采出程度不足8%,开发效果一直较差.通过精细油藏描述及剩余油分布研究,搞清储层及剩余油在三维空间展布的基础上,提出三断块NgI稠油底水油藏,采取钻水平井加密与钻直井加密相结合,并配合一定的油水井措施整体挖掘油藏潜力的井网调整策略.羊H1井的钻探成功,为下一步的调整、挖潜打下了坚实基础,并对同类油藏的开发调整将具有一定的借鉴意义.     

Flow resistance in a compound gravel-bed bend

In this paper, the effect of a gravel-bed in a compound bend (similar to sinusoidal top view) of a natural river (Zayandehrud River flowing through Isfahan, Iran) has been investigated for flow resistance analysis, measuring the velocity with a micro current meter. The data were analysed and the following observations were made. In a compound bend, the law of the wall can be valid for up to 66% of the flow depth from the bed. The parabolic law is the most effective method for the determination of shear velocity. Based on the existing criteria for verifying the equilibrium boundary layer, the flow cannot be in equilibrium. The shear stress distribution and the sediment transport parameters have considerable influence on resistance to flow. Froude number and the flow depth relative to the representative gravel size have little effect on the flow resistance estimation.     

Size Distribution of Gold Nanoparticles Used by Small Angle X-ray Scattering

The size distribution of gold nanoparticles was estimated based on the scattering intensity data obtained from small angle X-ray scattering (SAXS) and compared with the result of micrographs by transmission electron microscopy. The slope of the Guinier plot was used to estimate the mean size assuming a narrow particle size distribution. When the size distribution is narrow, the mean size can be easily obtained from slope of a Guinier plot of scattering data within 10% error. Additionally, assuming a lognormal size distribution, the size distribution and the mean size can be calculated using the experimental SAXS data in the fitting analysis. The histogram method, which utilizes the coefficient matrix of scattering intensity, was also applied to the estimation of the size distribution, and this method could be useful for a rough estimate of the size distribution.     

Conductometric Study of Some Metal Halides in Glycerol + Water Mixtures

Electrolytic conductivities of potassium halides, KX (X = Cl⁻, Br⁻, I⁻) have been investigated in 10, 20, and 30 mass% glycerol + H₂O mixtures at 298.0, 308.0, and 318.0 K. The conductance data have been analyzed by the Fuoss-conductance–concentration equation in terms of the limiting molar conductance (Λ⁰), the association constant (K _A ), and the distance of closest approach of ion (R). The association constant (K _A ) tends to increase in the order: 10 mass% < 20 mass% < 30 mass% glycerol + water mixtures, while it decreases with temperature. Thermodynamic parameters ΔH ⁰, ΔG ⁰, and ΔS ⁰ are obtained and discussed. Also, Walden products (Λ⁰η) are reported. The results have been interpreted in terms of ion–solvent interactions and structural changes in the mixed solvents.     

一类带配送中心运输问题的容量扩张模型研究

运输问题一般采用表上作业法来解决，考虑一类带配送中心的运输问题，若仍采用表上作业法，会使问题复杂化，文中采用一种构造辅助网络的方法：在运输网络中将每个配送中心均拆分成2个点，连接两点形成新弧，构造出新的网络，并给每条弧赋予参数，将此类运输问题转换为最小费用流模型来解决，可以使问题模型和运算简单化．在此基础上，考虑运输网络中配送中心和边的容量扩张问题．     

The beta exponential distribution

The exponential distribution is perhaps the most widely applied statistical distribution for problems in reliability. In this note, we introduce a generalization—referred to as the beta exponential distribution—generated from the logit of a beta random variable. We provide a comprehensive treatment of the mathematical properties of the beta exponential distribution. We derive expressions for the moment generating function, characteristic function, the first four moments, variance, skewness, kurtosis, mean deviation about the mean, mean deviation about the median, Rényi entropy, Shannon entropy, the distribution of sums and ratios, and the asymptotic distribution of the extreme order statistics. We also discuss simulation issues, estimation by the methods of moments and maximum likelihood and provide an expression for the Fisher information matrix. We hope that this generalization will attract wider applicability in reliability.     

系统边际价格概率分布的实证分析

该文针对系统边际价格的概率分布模型问题，展开实证分析，验证了系统边际价格概率分布的超高斯性，并提出了适合的电价超高斯型概率分布模型。首先，该文对多个典型电力市场中的日前现货电能量市场的系统边际价格的概率分布特性进行了市场行为分析、频率分布直方图和高阶统计量等多角度的实证剖析，揭示出系统边际价格实际上并不满足传统的高斯分布假设，而是服从超高斯型概率分布的规律。在此基础上，针对各典型市场的系统边际价格的实际概率分布规律，该文提出了适用于系统边际价格的超高斯型概率密度新模型。典型电力市场的实例数据验证了该文所建模型的有效性。     

地理信息系统在供电企业中的应用

结合宁夏电力公司银南供电分公司企业内部网络,针对目前城网改造引起城区配电网结构的变化,提出了在原城网配电自动化系统的基础上构建的电力企业地理信息系统(GIS),使全公司范围内的所有GIS工作站均能方便地浏览到配电网图形、配电网实时数据和静态数据,以达到资源共享。     

发电机中性点配电变压器二次负载电阻的现场选取和校核

发电机中性点配电变压器二次负载阻值是按发电机及机端设备对地电容理论值设计的。其阻值是否合适．应在机组投产前实测参数以选取合理电阻抽头并进行校核。结合实例，提供了一套现场测试参数和配电变压器二次阻值抽头选取及校核的实用方法。