Symmetric Part Preconditioning of the CG Method for Stokes Type Saddle-Point Systems

A nonsymmetric formulation of saddle-point systems is considered, and symmetric part preconditioning of the CG method is applied. Linear and superlinear convergence estimates are derived for the finite element solution of the Stokes problem and of Navier's equations of elasticity. Mesh independence of the estimates is obtained from proper Hilbert space operator background.     

Multipoint Super-Halley Type Approximation Algorithms in Banach Spaces

We use a new multipoint iteration of at least R-order three to solve a nonlinear operator equation in a Banach space. Under standard Newton-Kantorovich assumptions, we establish two Kantorovich convergence theorems using a new system of recurrence relations. We also give some explicit error bounds for this iteration.     

Null controllability for the parabolic equation with a complex principal part

The paper is devoted to a study of the null controllability for the semilinear parabolic equation with a complex principal part. For this purpose, we establish a key weighted identity for partial differential operators (with real functions α and β), by which we develop a universal approach, based on global Carleman estimate, to deduce not only the desired explicit observability estimate for the linearized complex Ginzburg-Landau equation, but also all the known controllability/observability results for the parabolic, hyperbolic, Schrödinger and plate equations that are derived via Carleman estimates.     

RIEMANN BOUNDARY VALUE PROBLEMS WITH GIVEN PRINCIPAL PART

In this article, the authors discuss the Riemann boundary value problems with given principal part. First, authors consider a special case and give a classification of the solution class Rn by the way. And then, they consider the general case. The solvable conditions for this problem and its solutions is obtained when it is solvable.     

Unitary part of a contraction

For a contraction A on a Hilbert space H, we define the index j(A) (resp., k(A)) as the smallest nonnegative integer j (resp., k) such that ker(I−Aj∗Aj) (resp., ker(I−Ak*Ak)∩ker(I−AkAk∗)) equals the subspace of H on which the unitary part of A acts. We show that if , then j(A)?n (resp., k(A)?⌈n/2⌉), and the equality holds if and only if A is of class Sn (resp., one of the three conditions is true: (1) A is of class Sn, (2) n is even and A is completely nonunitary with ‖An−2‖=1 and ‖An−1‖<1, and (3) n is even and A=U⊕A^′, where U is unitary on a one-dimensional space and A^′ is of class Sn−1).     

考虑储备期间失效的可修复备件需求模型

备件数量决定了装备维修能力和保障水平,能否科学地预测备件数量,取决于备件需求计算模型建立的准确性。在此根据备件维修性将备件分为可修复件和不可修复件,针对可修复件的备件需求问题,在考虑储备期间发生故障的前提下,利用备件可靠性框图方法,建立单可修复件、多可修复件的备件需求计算模型,解决了备件考虑储备期间故障的实际需求。结合工作环境的影响对模型中的故障率进行修正,使模型更贴近实际需求。     

微量热法研究鹿茸4个活性部位对肠道特征菌群生长代谢的影响

建立灵敏表征鹿茸中具有补益活性的4个部位对两种肠道特征菌群生长代谢影响的评价方法.采用微量热法,在不同给药条件作用下,以产热功率-时间曲线(热谱曲线)的特征参数(生长速率常数(k)、最大产热功率(Pmax)、达峰时间(tp)及有效率(E)等)为指标,对肠道主要有益菌(青春双歧杆菌)生长代谢程度进行客观地量化评价.挑选鹿茸促菌最强的活性部位,进一步考察该部位对病原微生物(金黄色葡萄球菌)生长抑制的作用规律.结果表明,鹿茸不同活性部位促进青春双歧杆菌生长代谢强弱顺序为:正丁醇乙醚氯仿乙酸乙酯.活性最强的正丁醇萃取液对病原微生物(金黄色葡萄球菌)抑制影响的研究表明,正丁醇萃取液在浓度大于200μg·mL-1时,对金葡菌生长具有抑制作用.且tp随药液浓度的增加而相应地延长;k,Pmax均随浓度的增加而相应地减小.微量热法具有灵敏准确、实时在线、重现性好等特点,可用于名贵药材——鹿茸的活性部位的筛选,也为药效物质的研究提供了一个新的研究思路和方法.     

电子元器件的淘汰对军用和航空工业的影响

电子技术的高速发展和国防与航空市场的缩小使电子部件淘汰问题日益突出。对国外军用和航空系统的电子部件淘汰问题以及研究现状进行了综述     

DS/CDMA通信中匹配滤波器的FPGA设计

匹配滤波器因具有大的时间带宽积而在扩频和CDMA通信中受到极大重视，不仅作为快速捕获和RAKE分集等传统技术的最佳方案，而且在多用户检测、智能天线、多速率甚至是软切换等方面也都能发挥其优势；对匹配滤波器捕获的基本原理进行了研究并着重讨论了其多种FPGA实现结构。     

Active control schemes for aseismic base-isolated structures

Summary  Active control schemes are used for the protection of base-isolated and seismically excited buildings. The desired control objective is to keep the whole structure arbitrarily close to its initial configuration prior to the earthquake. The proposed methods require control force application only at the base of the structure. The controllers developed may depend on information obtained from all the floors or just the first (base) floor alone. Received 13 September 2000; accepted for publication 26 June 2001 RID=" ID=" Dedicated to the memory of Professor P.D. Panagiotopoulos with our warmest prayers. RID=" ID=" The first author wishes to thank Prof. G. Leitmann and Prof. E. Papadopoulos for the numerous helpful discussions. The same author is supported in part by the Institute of Communication and Computer Systems, NTUA, under the program Archimedes 65/1017.