查询词典 necessary and sufficient conditions

The sufficient and necessary conditions of the nondegeneracy and struc- tural asymptotical stability for complex systems (parallel systems, series sys- tems and closed systems) are proved.

在这基础上，给出了系统在串联、并联及反馈时构成的复杂系统的非变阶条件和结构渐近稳定的充分必要条件。

Taking the active network as a research task, the input accessibility, the Coates graph of matrix and graph transmission etc are used to analyze the relation between reducibility of the coefficient matrix of the state equation and the electric separability of the network or the electric accessibility of the network for the first time, acquiring sufficient and necessary conditions that coefficient matrix of the state equation is reducible. Network Graph Theory, Matrix Theory and System Theory over F etc are used to derive the structural controllability criterion of the passive network over F for the first time. Then according to these theoretic results, the structural controllability problems of the active network over F are studied, acquiring several structural controllability conclusions of the active network.

率先将状态方程的输入可达、矩阵的Coates图、流图传输系数等概念和方法引入到对F上有源电网络的研究，研究了网络状态方程的系数矩阵的可约性与网络电气可断性或电气可达之间的关系，研究了F上有源电网络的能控性问题，获得了状态方程的系数矩阵可约的充分必要条件、F上有源电网络系统的结构能控性判据等新的结论。

The description of network delays including characteristics and effects are also covered and the uniformed mathematic models for NCSs with four different structures are derived. Furthermore, the controller basing on state prediction and compensating time delay is designed. Sufficient and necessary stability conditions for systems with different transmission policies such as perfect transmissions, delayed transmissions and time-varying transmissions are obtained as simple eigenvalue tests of certain test matrices. And in the end, effects of model error over maximum communication interval are analyzed. Numerical examples show the feasibility and efficiency of the proposed methods.

首先介绍了网络控制系统中数据包的传输情况以及基于模型结构方法的基本思想，并针对四种不同拓扑结构的控制网络分析了网络时延的性能，进而给出了统一的数学模型；然后，提出了基于状态预测的具有时延补偿功能的状态反馈控制器的设计方法，并针对完美传输、延时传输及时变传输三种数据传输策略，分别研究了控制系统的稳定性问题；最后分析了模型误差对最大通讯间隔的影响；仿真结果表明了设计及控制方法的正确性和有效性。

Analog to the discontinuous bifurcation analysis for classic elasto-plastic theory by Ottosen and Runesson et al, the sufficient and necessary conditions of weak discontinuity and strong discontinuity localization bifurcation for the strain-gradient-enhanced-damage model are obtained.

借鉴Ottosen和Runeson等的弹塑性模型不连续局部化分岔方法，对应变梯度损伤模型推导出与梯度相关的强不连续和弱不连续局部化分岔充要条件。

This Paper deals with problems of large number theorem in stochastic sense and obtains sufficient and necessary conditions,for weak law and strong law of large numbers in stochastic sense .

本文讨论随机大数定律，得到一个随机变量序列分别服从随机弱大数定律和随机强大数定律的充要条件。

Over a field of arbitrary characteristic, we construct a class of associative superalgebras of Weyl type and a class of Lie superalgebras of Weyl type from ∧(2, 2) and the polynomial algebra of the special deravation subalgebra of it. In addition, we prove that the sufficient and necessary conditions of the simplicity of the associative and the Lie superalgebras.

在任意特征域上，从∧(2，2)和它的特殊导子的子空间的多项式代数出发，构造了一类Weyl型结合超代数和一类Weyl型李超代数，进而给出并证明了它们为单的充要条件。

And the sufficient and necessary conditions are obtained and the uniqueness of T is discussed and an algorithm for solving the inverse problem is provided. The other kind of structure inverse eigenvalue problem is for unitary Hessenberg matrices with positive subdiagonal elements. That is, a unitary Hessenberg matrices with positive sub-diagonal elements can be constructed when its eigenvalues and the eigenvalues of H_(11) and H_(22) are known. Here H_(11) and H_(22) are rank-one modifications of k × k leading principal submatrix of H and of its × remain submatrix respectively. In the end, the uniqueness of H and an algorithm is obtained.

文中首先讨论了这三组特征值之间的交错关系，接着确定了该逆问题有解的充要条件，并论证了其解的唯一性问题，最后给出了相应的数值算法；本文第二个问题解决的是一类不可约的酉Hessenberg阵的逆特征值问题：即一个不可约的酉Hessenberg阵可以由它的特征值、它的前k阶秩一修正的顺序主子阵的特征值以及它的后n—k阶余子阵的秩一修正阵的特征值来确定，文中最后讨论了唯一性和相应的算法。

Our main work is as follows: the stable laser mode theory in uniform plasmas is extended to non-uniform plasma cases; the discussion of the sufficient and necessary conditions for laser self-focusing in uniform plasmas is developed to non-uniform plasma cases; a quantitative approach to judge the impact of different plasma density distribution on laser self-focusing is proposed; the evolution properties of asymmetric laser filed in non-uniform and uniform plasmas are discussed and mechanisms that symmetric channel-like plasmas can confine the laser centroid around the plasma channel axes and symmetrize initially asymmetric laser beams are proposed; the formation of solitary standing wave in moderate plasma density is studied by PIC simulations and can be explained by stimulated Raman scattering of laser beams in plasmas.

主要工作为：把均匀等离子体中激光的稳定模理论推广到横向非均匀等离子体情形；把均匀等离子体中激光自聚焦的充分和必要条件的讨论推广到横向非均匀等离子体情形；给出横向密度分布不同的等离子体影响激光自聚焦的定量判据。讨论了初始不对称的激光场在横向非均匀及均匀等离子体中的演化特性，并提出了具有对称腔道结构的等离子体箍缩激光质心和对称化初始不对称激光场的物理机制。用粒子模拟讨论了激光场在等离子体中形成孤立驻波的过程，认为前向受激拉曼散射是发生此现象的可能机制。

Applying mechanics of partitioning of matrix and special structure, we have given the sufficient and necessary conditions for the matrix if it has bisymmetric and anti-bisymmetric solutions.

对于广义双对称与广义双反对称矩阵，首先结合矩阵的结构特点，应用广义逆的相关知识，给出了有解的充要条件以及有解时解的表达式，最后在一种特定的分解条件下，考虑了它的广义双反对称最小二乘解。

The summary results are below:1. GUS expression under the driving of the BjCHI1 promoter (-1060/+17) was essentially undetectable in the young seedlings under normal growth conditions. GUS activity was first detected in the stigma of young flowers, peaked in the young siliques, and decreased when the siliques became older. No GUS expression was found in the mature siliques, seeds or root.2. The BjCHI1 promoter (-1060/+17) was inducible by NaCl, PEG, wounding and MeJA treatments. High levels of GUS expression were detected in the transgenic tobacco and Arabidopsis plants after wounding, NaCl, PEG, and MeJA treatment, indicating that the BjCHI1 promoter responses to both biotic and abiotic stresses.3. RT-PCR analysis confirmed that the expression of the BjCHI1 gene in B. juncea was inducible by PEG and NaCl.4. The transcription start site was determined by 5′-RACE, and was located at the 17th nucleotide upstream of the translation initiation codon of the BjCHI1 gene.5. A -805/+17 promoter fragment was enough to response to wounding and MeJA induction, which was proved in transgenic tobacco and Arabidopsis plants. The 397 bp region between -805 and -409 of the BjCHI1 promoter contains a cis-acting element that is essential for the wounding and MeJA inducibility.6. The -695/-620 region was necessary but not sufficient to confer MeJA-responsive expression. A T/G-box locates in -353 play an important role in the expression of the BjCHI1 gene in response to MeJA treatment. The 76 bp region is coupled with the T/G-box to confer full MeJA-inducible transcription of the BjCHI1 gene.

主要结果如下：1、利用转基因拟南芥植株分析表明，正常生长条件下，BjCHI1启动子(-1060/+17)驱动GUS基因主要在花柱中表达，幼嫩的荚也有表达，并随着果荚的成熟而减弱，成熟的果荚、种子和根没有显示GUS活性。2、BjCHI1启动子(-1060/+17)能驱动GUS基因在转基因烟草和拟南芥中响应伤害的诱导，转基因拟南芥的分析还证明BjCHI1启动子也受MeJA、NaCl和PEG的诱导，证明BjCHI1启动子是一个伤害、MeJA、NaCl和PEG等生物和非生物因素诱导启动子。3、RT-PCR进一步证明芥菜中BjCHI1基因也受NaCl和PEG的诱导表达。4、5′-RACE法鉴定了BjCHI1启动子的转录起始位点，位于翻译起始位点ATG上游第17个碱基A.5、转基因烟草和拟南芥分析证明，-805/+17的启动子片段足以响应伤害和MeJA的诱导，-805和-409之间397 bp的启动子片段含有对伤害和MeJA诱导必要的元件。6、本明烟叶片瞬时表达系统分析证明，一段76 bp的序列(-695/-620)对BjCHI1启动子响应MeJA的诱导是必要的，但不足以响应MeJA的诱导，位于-353的T/G-box也参与MeJA的诱导。76 bp的序列(-695/-620)与T/G-box协同起作用，赋予BjCHI1启动子MeJA诱导性。

Cynanchum Lingtai apricot production in the average weight 65 grams, the brightly-colored fruit, juicy rich, sweet-sour taste, sweet from the nucleolus, when the late Qing Dynasty famous Shaanxi, Gansu provinces, the Qing imperial court Tongzhi tribute for years.

灵台生产的牛心杏平均单果重65克，果实色泽鲜艳，汁多味浓，甜酸适口，离核仁甜，清末时就驰名陕、甘两省，清同治年间曾为朝廷贡品。

Chenopodium album,Solanum nigrum, and Amaranthus retroflexus were very susceptible to the herbicides. Polygonum persicaria and Abutilon theophrasti were relatively less susceptible to the herbicides, and Lycopersicon esculentum was not susceptible to it. The relationship between reduction rates of weed biomass and PPM values of weed leaves 2,4, and 6 days after treatment was established.

供试的6种杂草对该混剂的敏感性存在显著差异：红心藜Chenopodium album、龙葵Solanum nigrum和反枝苋Amaranthus retroflexus对该混剂最敏感，ED90值分别为47.65、71.67和29.17g/hm2；春蓼Polygonum persicaria和苘麻Abutilon theophrasti敏感，ED90值分别为96.91、114.20g/hm2；而番茄不敏感。