时间序列分析方法及人民币汇率预测的应用研究

在简要介绍时间序列模型的基础上,使用人民币／美元的日汇率值进行实证研究,建立相应的ARIMA模型和EGARCH模型并进行预测和评价。研究结果表明,EGARCH模型的预测结果较ARIMA模型理想,适合描述人民币／美元汇率的变动趋势。     

Test Studies on Performances of TGP Total Gradation Concrete

The Three Gorges Project （TGP） is the largest water conservancy and hydropower complex in the world, with a concrete consumption of 28 million m^3 in total. For such a significant world-attracting project, first rate quality concrete is needed. Various mechanical and deformation performances of hydraulic mass concrete are determined conventionally by the wet screening method to make small specimens and the test results of the small standard specimens are taken to represent the properties of the mass concrete. However, the quantity of the coarse aggregate after wet screening would be reduced by 30% or so and the gel materials would increase by 20% or so, thus causing significant differences between the properties of the small concrete specimen and that of the total gradation concrete. To well understand the performances of the total gradation concrete of TGP dam, test studies have been performed on the total gradation concrete, including compressive strength, split tensile strength, elastic modulus, ultimate tension, dry shrinkage, self volume defomation, creep, seepage prevention, and so on, and comparison made with the small standard specimens to find out the relationship between them, which have provided scientific gound for the design, operation and safety verification of the TGP dam.     

着舰导引中的H∞飞行/推力控制系统研究

运用基于线性矩阵不等式的H∞控制理论,提出了保持由地速构成的迎角αd恒定的H∞飞行／推力综合控制增广模型,使飞机接近舰尾处于雷达导引系统关闭的关键时刻,仍具有优良的姿态保持及抑制气流扰动性能,改变了传统设计由导引系统纠正气流扰动而引起的轨迹偏离;还从工程应用角度出发,提出了H∞控制器的降阶方法,并进行了实时仿真验证。     

基于网格密度和距离信息特征的聚类算法

真实数据集通常密度分布不均,多数基于网格和密度的聚类算法采用的单调性搜索方法难以形成有效聚类．为此,文中提出了基于网格密度和距离信息特征的聚类算法（GDD）．该算法将数据空间划分成网格单元,并构建基于簇中心距离信息的跃迁函数,通过考察局域范围内网格单元的密度跃迁比,并比对计算出的当前网格单元的跃迁函数值,以决定是否继续扩展和增长聚类簇规模．具体的跃迁函数在真实和模拟集上的实验结果表明：GDD算法能够发现任意形状的簇,对噪音数据不敏感,且具有线性于网格数目的时间复杂性,适合对大规模真实数据集的聚类．     

超临界锅炉用不锈钢热处理工艺与组织分析

在分析10Cr18Ni9NbCu3BN奥氏体不锈钢显微组织的基础上,计算预测钢中未溶碳氮化物和高温铁素体δ相的含量和材料的强度,并分析热处理工艺的合理性.研究结果表明,高温铁素体δ相的计算值与试验结果相符;材料强度的计算值与试验结果相近;固溶处理温度可降低到1 100 ℃;软化处理温度可降低到1 150 ℃.对奥氏体不锈钢热处理工艺、组织和强度进行的计算分析将为企业生产提供重要的理论依据.