带反射变量微分方程的极限周期解

本文利用给定的周期序列,定义了极限周期函数的一个子集,并讨论了该子集的一些性质。然后,借助Banach压缩映像原理证明了带反射变量的一阶微分方程x′(t)+ax(t)+bx(-t)=F(t,x(t),x(-t)),b≠0,t∈R的极限周期解的存在性及唯一性,其中函数F关于t是一致极限周期的,且F关于后两个变量满足Lipschitz条件。

合成序列变换在极限周期连分式加速收敛中的应用

文章针对极限周期连分式K n=1 ∞〔an 1〕的加速收敛因子序列引入合成序列变换,得到新的因子序列,证明了新的因子序列也是加速收敛因子序列。从定性和定量的角度来看,在一定的条件下它比合成前的加速收敛因子序列具有更多优良性质;文章还针对所构造出来的加速收敛因子,给出了误差控制,这有利于估计算法的精确性。

合成序列变换对极限周期连分式的加速收敛(英文)

合成序列变换是由C .Brezinski在 1985年首先引入的 ,它在序列加速收敛方面是非常有用的。极限周期连分式是通过加速收敛因子来实现的。本文的主要目的是研究合成序列变换对极限周期连分式的加速收敛 ,得到了一些收敛和加速收敛的结果。与其同时 ,我们还对合成序列变换引入AitkenΔ2 -过程 。

极限周期连分式sum from n=1 to ∞ 〔a_n/1〕加速收敛的误差估计

极限周期连分式是一类非常重要的连分式,它在连分式分析理论中占有极其重要的地位。文章从定量角度出发,对极限周期连分式在一般加速收敛因子下的加速收敛效果进行了研究,并给出了误差表达式。

极限周期连分式修正因子的一种新求法

加速收敛在连分式理论中占有重要的地位,对连分式进行加速收敛最常用的方法是选择合适的修正因子;文章借助极限周期连分式与2-周期连分式的性质,针对极限周期连分式的修正因子给出一种新的选取方式,数值例子表明,新的修正因子使得连分式的收敛更快,精度更高。

极限周期连分式的一种较快加速收敛方法

对极限周期连分式的一类修正逼近式序列进行变换以期达到快速加速的目的,并证明新的逼近式在一定条件下具有更快的加速逼近效果.最后用数值例子验证方法的可行性和有效性.

基于多周期极限采样法的极限检测器设计

为解决极限检测器单周期数据采样精确度低的问题,提出了多周期极限采样法。利用多周期极限采样法对极限检测器进行了设计,该极限检测器对周期信号进行5个周期的数据采样,通过极限检测器的FIFO模块、最大最小值寄存器模块、数值比较模块最终得到精确的极限值。最后,利用QUARTUS技术对设计进行了验证,该方法能够准确实现偏移量为3 ns的极限检测。

极限2-周期连分式的一种新算法

加速收敛在连分式理论中占有重要的地位,对连分式进行加速收敛最常用的方法是选择合适的修正因子。如果连分式是极限k-周期的,则修正因子序列也应是k-周期的,这就使对于k≥2的周期连分式其修正因子的选取较为困难;文章借助了连分式的压缩技术,针对极限2-周期连分式推导出一种新算法,使修正因子的选取变得简单;数值例子表明新算法使连分式的收敛更快、精度更高。

利用压缩变换求极限2-周期连分式的值

加速收敛在连分式理论中占有重要的地位,对极限周期连分式进行加速收敛最常用的方法是通过选择合适的修正因子。如果b_0+(?)((a_n)/(b_n))是极限k-周期连分式,则修正因子序列也应是k-周期的,这就使得对于k≥2的周期连分式的修正因子的选取较为困难。借助连分式的压缩性质,针对极限2-周期连分式推导出一种新算法,从而避免修正因子的选取,数值例子表明新算法使得连分式的收敛更快,精度更高。

周期到达队列的高负荷极限

在周期到达的Gt/G1／s队列中，研究常规的顾客人数的高负荷极限。我们假设到达计数过程由累积随机过程构成，里积随机过程满足泛函中心极限定理和确定性累计率函数是周期函数的积分。对于确定到达率函数的三个不同刻画，研究三个不同的高负荷极限。

LIENARD方程极限环的唯一性

本文将就形如:(?)+f(x,(?))(?)+g(x)=0其中 f(x,(?))=sum from i-1 to n(f_i(x)(?)~的方程的极限环的唯一性加以讨论,并给出相关定理的叙述及证明.

稠油油藏CO_2吞吐合理吞吐轮次

冀东油田高浅北区稠油油藏高含水油井自2010年底实施CO_2吞吐控水增油以来,取得良好效果。但首轮吞吐失效后,面临吞吐增油量逐轮减少、换油率下降、吨油成本不断上升的问题。为了有效提高吞吐措施效果,在明确CO_2吞吐控水增油机理和主要注采参数优化的基础上,以高浅北区某典型底水稠油油藏为例,考虑不同构造位置、水平井轨迹差异及不同采出程度,进行CO_2吞吐合理吞吐轮次数值模拟研究。研究表明:多轮吞吐效果主要受构造位置、井轨迹及含油饱和度的影响,高部位物性好的油井实施5轮次吞吐效果较好;腰部采出程度相对较低的油井可实施4轮吞吐;采出程度相对较高的油井、边部中部位油井可实施3轮次吞吐。矿场实践证实,该方法可减少无效措施工作量,实现多轮吞吐经济效益最优化。

改进型临界比例度法用于PID参数的自整定

介绍改进型临界比例度法实现PID参数的自整定 。

双光子光学双稳系统的混沌控制

把对有限维离散化系统混沌控制的方法应用于高维微分动力系统 ,讨论了双光子光学双稳系统中的混沌控制 .通过数值计算 ,对双光子光学三稳态中的不稳定 1周期极限环和 2倍周期极限环进行了控制 ,并讨论了控制系统对噪音的依赖性问题 .计算结果表明 ,该方法对高维微分动力系统中的混沌控制是有效的 .

Limit Properties of One Dimensional Periodic Hopping Model

One dimensional periodic hopping model is useful to understand the motion of microscopic particles in thermal noise environment. In this research, by formal calculation and based on detailed balance, the explicit expressions of the limits of mean velocity and diffusion constant of this model as the number of internal mechanochemical sates tend to infinity are obtained.These results will be helpful to understand the limit of the one dimensional hopping model.At the same time, the work can be used to get more useful results in continuous form from the corresponding ones obtained by discrete models.

Numerical Simulation of Heat Exchanger＇s Length＇s Effect in a Thermoacoustic Engine

A numerical study of a standing-wave thermoacoustic engine is presented. The aim of this work is to study the effect of increasing the heat exchangers length on the acoustic power. The analysis of the flow and the prediction of the heat transfer are performed by solving the non linear unsteady Navier-Stocks equations using the finite volume method implemented in -ANSYS CFX- CFD code. The results show an increase in the limit cycle acoustic pressure and power as well as the specific work per cycle with the increase of heat exchangers length.

Degradation process assessment of prestressed concrete continuous bridges in life-cycle

To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance assessment of concrete bridges was proposed.The existing assessment methods were firstly introduced and compared.Some essential mechanics problems involved in the degradation process,such as the deterioration of materials properties,the reduction of sectional areas and the variation of overall structural performance caused by the first two problems,were investigated and solved.A computer program named CBDAS(Concrete Bridge Durability Analysis System) was written to perform the above-metioned approach.Finally,the degradation process of a prestressed concrete continuous bridge under chloride penetration was discussed.The results show that the concrete normal stress for serviceability limit state exceeds the threshold value after 60 a,but the various performance indicators at ultimate limit state are consistently in the allowable level during service life.Therefore,in the case of prestressed concrete bridges,the serviceability limit state is more possible to have durability problems in life-cycle;however,the performance indicators at ultimate limit state can satisfy the requirements.

Small-amplitude limit cycles of polynomial Linard systems

In this paper, we study the number of limit cycles appeared in Hopf bifurcations of a Lienard system with multiple parameters. As an application to some polynomial Lienard systems of the form x= y, y= -gin（x） - fn（X）y, we obtain a new lower bound of maximal number of limit cycles which appear in Hopf bifurcation for arbitrary degrees m and n.

Global Bifurcation of a Perturbed Double-Homoclinic Loop

This paper deals with a kind of fourth degree systems with perturbations. By using the method of multi-parameter perturbation theory and qualitative analysis, it is proved that the system can have six limit cycles.