灰色离散系统的稳定性充分判据

本文利用一般离散系统的Lyapunov方程研究了灰色离散系统的稳定性问题,并给出了灰色离散系统的稳定性充分判据和应用实例。     

探讨利用3S技术对小区域生态环境变化的分析方法——以福州大学城周围环境为例

以福州大学城周边地区为例，探讨了利用“3S”技术对小区域生态环境变化进行综合分析的实用方法．利用从20世纪80年代至今的航空遥感（RS）数据，闽侯大学城周边区域乡界地图，植被覆盖的相关生态环境监测数据，基于全数字作业的遥感与地理信息系统（GIS）一体化技术提取研究区生态环境状况及其变化信息，综合运用“3S”技术，通过对遥感影像的分析，运用环境监测技术，进行大学城周边地区多年生态环境变化规律的研究．     

福建三明小湖赤枝栲群落组成结构及物种多样性分析

调查三明小湖赤枝栲自然保护区的 41个 10m× 10m样方 ,共 410 0m2 的群落面积 ,测定群落物种多样性特征 ,得到Margalef丰富度指数D1=14.5 6 14;Shannon Wiener多样性指数D2 =5 .4336 ;Simpson多样性指数D3 =0 .95 6 6 ;种间相遇几率PIE =0 .95 6 7;均匀度J =0 .7788.探讨乔木层、灌木层、及藤本的物种多样性特征值 ,其变化趋势与群落总多样性一致 .分析群落中 12个主要乔木种群的年龄结构 ,揭示群落乔木层主要建群种呈稳定型 ,表明该群落正处于相对稳定的群落演替阶段     

Ultrasonic flaw detection using EMD-based signal processing

The precise detection of flaw echoes buried in backscattefing noise caused by material microstructure is a problem of great importance in uhrasonic non-destructive testing （NDT）. In this work, empirical mode decomposition （EMD） is proposed to deal with ultrasonic signal. A time-frequency filtering method based on EMD is designed to suppress noise and enhance flaw signals. Simulated results are presented, showing that the proposed method has an excellent performance even for a very low signal-to-noise ratio （SNR）. The improvement in flaw detection was experimentally verified using stainless steel pipe sample with artificial flaws.     

Efficient analysis of dielectric radomes using multilevel fast multipole algorithm with CRWG basis

A full-wave analysis of the electromagnetic problem of a three-dimensional （3-D） antenna radiating through a 3-D dielectric radome is preserued. The problem is formulated using the Poggio-Miller-Chang-Harrington- Wu（PMCHW） approach for homogeneous dielectric objects and the electric field integral equation for conducting objects. The integral equations are discretized by the method of moment （MoM）, in which the conducting and dielectric surface/interfaces are represented by curvilinear triangular patches and the unknown equivalent electric and magnetic currents are expanded using curvilinear RWG basis functions. The resultant matrix equation is then solved by the multilevel fast multipole algorithm （MLFMA） and fast far-field approximation （FAFFA） is used to further accelerate the computation. The radiation patterns of dipole arrays in the presence of radomes are presented. The numerical results demonstrate the accuracy and versatility of this method.     

催化裂化柴油非加氢精制方法的研究进展

对催化裂化柴油非加氢精制改善其安定性的方法以及各种非加氢精制方法的原理、工艺的优缺点和技术经济分析方法等进行了综合论述。其中 ,酸碱精制、吸附精制、溶剂精制、加速老化、离子交换树脂精制等方法主要是把柴油中的不安定组分从柴油中分离出来 ,而加入稳定剂法是通过稳定剂来抑制不安定组分的反应 ,从而达到稳定柴油特别是催化裂化柴油的目的。提出了利用其中两种或几种非加氢精制方法对柴油进行精制的设想     

Effect of weld microstructure on brittle fracture initiation in the thermally-aged boiling water reactor pressure vessel head weld metal

Effects of the weld microstructure and inclusions on brittle fracture initiation are investigated in a thermally aged ferritic high-nickel weld of a reactor pressure vessel head from a decommissioned nuclear power plant.As-welded and reheated regions mainly consist of acicular and polygonal ferrite,respectively.Fractographic examination of Charpy V-notch impact toughness specimens reveals large inclusions(0.5-2.5μm)at the brittle fracture primary initiation sites.High impact energies were measured for the specimens in which brittle fracture was initiated from a small inclusion or an inclusion away from the V-notch.The density,geometry,and chemical composition of the primary initiation inclusions were investigated.A brittle fracture crack initiates as a microcrack either within the multiphase oxide inclusions or from the debonded interfaces between the uncracked inclusions and weld metal matrix.Primary fracture sites can be determined in all the specimens tested in the lower part of the transition curve at and below the 41-J reference impact toughness energy but not above the mentioned value because of the changes in the fracture mechanism and resulting changes in the fracture appearance.     

句首词(成分)对语序的影响

在了解英语句子的语序时，有一条重要的因素应加以考虑，即英语句子的重量（Ｗｅｉｇｈｔ）按通 常的习惯，不是置于句首，就是移于句末． 一般说，为了突出所要强调的内容，往往把不是主语的其它成分置于句首，即Ｒ．夸克所谓的 “主题前移”，因为主题放在句子的最前面会使读者或听者有较深刻的印象。 然而，主题前移往往会引起语序的变化，但有时又不影响语序，其原因何在？是否有某种规律可循？本立拟通过许多例句的分析与比较，对此问题作初步的探讨．     

微弱直流信号检测系统抗干扰方案的研究

作者在本文中提出了提高调制型微弱直流信号检测系统的抗干扰能力的方案，采用了选频放大器和相敏检波器的设计方案。在文中还对各部分电路的传输函数、幅频特性、元件灵敏度以及元件参数的选择等都进行了分析讨论，给出了实验波形和测试数据。