A Galerkin finite element scheme for time–space fractional diffusion equation

In this paper, a Galerkin finite element scheme to approximate the time–space fractional diffusion equation is studied. Firstly, the fractional diffusion equation is transformed into a fractional Volterra integro-differential equation. And a second-order fractional trapezoidal formula is used to approach the time fractional integral. Then a Galerkin finite element method is introduced in space direction, where the semi-discretization scheme and fully discrete scheme are given separately. The stability analysis of semi-discretization scheme is discussed in detail. Furthermore, convergence analysis of semi-discretization scheme and fully discrete scheme are given in details. Finally, two numerical examples are displayed to demonstrate the effectiveness of the proposed method.     

具有测量数据丢失的离散不确定时滞系统鲁棒Kalman滤波

研究了具有测量数据丢失的离散不确定时滞系统鲁棒Kalman滤波问题, 其中时延存在于系统状态和观测值中. 模型的不确定性通过在系统矩阵中引入随机参数扰动来表示, 测量数据丢失现象则通过一个满足Bernoulli分布且统计特性已知的随机变量来描述. 基于最小方差估计准则, 利用射影性质和递归射影公式得到一个新的滤波器设计方法, 并且保证了滤波器的维数与原系统相等. 与传统的状态增广方法相比, 当时延比较大时, 该方法可以有效降低计算量. 最后, 给出一个仿真例子说明所提方法的有效性.     

基于对数的NTC热敏电阻测温系统的设计

针对NTC热敏电阻阻值与温度(R-T)的非线性特性,为了提高测温精度,提出一种三阶对数公式法对R-T特性进行分段曲线拟合.该测温系统以三阶对数公式为基础进行了软硬件设计,实现了对船用柴油机的机油温度、冷却水温度的高精度测量.通过实验测试表明,在0～120℃温度范围内,采用该测温系统的测温误差小于±0.3℃.该测温系统已...     

A characterization of span program size and improved lower bounds for monotone span programs

We give a characterization of span program size by a combinatorial-algebraic measure. The measure we consider is a generalization of a measure on covers which has been used to prove lower bounds on formula size and has also been studied with respect to communication complexity.?In the monotone case our new methods yield lower bounds for the monotone span program complexity of explicit Boolean functions in n variables over arbitrary fields, improving the previous lower bounds on monotone span program size. Our characterization of span program size implies that any matrix with superpolynomial separation between its rank and cover number can be used to obtain superpolynomial lower bounds on monotone span program size. We also identify a property of bipartite graphs that is suficient for constructing Boolean functions with large monotone span program complexity. Received: September 30, 2000.     

误差最小的计算机插补原理

从包括的思想出发,解决了对单调光滑函数曲线构造一个带域,在此带域中所确定的绘图路径是误差最小的。另外,文中应用带域提出了一种误差最小插补法,得到递推公式,每次要计算的是进给步数,跟过去一贯采用的每走一步都要计算判别函数的传统方法比较,具有较强的优越性,最后给出计算实例。     

再访GI/M/1排队

通过构造两个向量马氏过程重新探讨了GI/M/1排队,某些新结果如忙期和闲期的 联合分布被得到了.这一方法容易推广到服务时间为无限位相型分布的GI/SPH/1排队.     

测土配方施肥与复混肥料

阐述20年来我国土壤养分变化的特点,提出用肥应坚持稳氮、磷,增钾肥、微肥、有机肥。测土配方施肥中,还应注意:土壤障碍因子、某种元素临界法与供应强度,肥料利用率等问题。对专用肥配方、复混肥的浓度、复混肥标准的一些规定从农艺角度提出一些意见。最后介绍几种常见作物的复混肥配方及施肥量、施肥方法。     

碳酸盐岩气藏岩电参数试验研究

为了提高储层参数的精度,针对某区块碳酸盐岩岩心开展试验研究,根据试验分析结果提供更为准确的测井资料解释模型.讨论在不同含水饱和度及围压条件下岩心电阻率的变化规律,并探讨围压对岩心电阻率的影响机理.     

全营养冻干方便米饭的配方设计与研究

采用线性规划法(LP),结合SPSS进行配方设计,得到冻干方便米饭的最佳配方为:主食大米650 g;配菜分别为猪肉140.195 g(20.67％)、豌豆167.740 g(24.73％)、菠菜186.946 g(27.56％)、土豆96.184 g(14.18％)、带鱼47.749 g(7.04％)、绿油菜39.465 g(5.82％).结合真空冷冻干燥技术,从营养和感官两个角度与四川得益方便米饭和贵州伊妹方便米饭进行比较,对产品进行综合评价.结果表明,方便米饭配方产品较四川得益和贵州伊妹具有一定的优势.