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31.
This paper mainly studies the problem of designing a hybrid state feedback D-admissible controller for a class of linear and nonlinear singular systems. Based on the relationship between singular discrete systems and singular delta operator systems, several necessary and sufficient conditions for a linear singular delta operator system to be D-admissible (i.e. regular, causal and all finite poles lie in a prescribed circular region) with different representations are derived. Then, the existence conditions and explicit expressions of a desirable D-admissible controller are given by means of matrix inequalities and strict linear matrix inequalities, respectively. We further extend the obtained results to singular delta operator systems with Lipschitz nonlinear perturbations, and the design methods of hybrid controller are presented for the nonlinear case as well. Finally, numerical examples as well as simulations are provided to illustrate the effectiveness of the theoretical outcomes obtained in the paper. 相似文献
32.
George W. C. Hung 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(2):211-235
The measurement of sorption and diffusion behavior of liquid ethanol and water solvent mixtures in polyurethane membrane were made simultaneously by thermogravimetry. The individual amounts of sorbed water and ethanol in the polymer membrane were estimated by thermogravimetry and differentiated by mass spectrometry. In addition, from a single dynamic thermogravimetric experiment the activation energy for solvent molecules desorbing from the polymer membrane was also determined. The thermodynamic activity of ethanol vapor in equilibrium with the ethanol-water-polyurethane system was determined by gas-liquid chromatography. The clustering functions, the mean numbers of solvent molecules in the clusters, and those associating with polymer sites were evaluated by applying simplified mathematical derivatives using the experimentally determined values of activity and volume fraction of solvent molecules. It was found that at lower ethanol concentration the tendency for ethanol molecules to cluster together is high. At higher ethanol activity, ethanol-polymer site interactions predominantly occurred. Similar results were observed for ethanol-water molecules. However, water molecules in this particular system did not exhibit a self-associating tendency nor interact with the polymer sites. It was concluded that the Zimm-Lundberg clustering theory can be adequately applied to the interpretation of sorption and diffusion behavior of liquid ethanol-water mixtures in the polymer membrane. 相似文献
33.
Four infinite complexes X 1 [Ni(NCS) 2 (4,4'-oda) 2 ], X 2 [Co(NCS) 2 (4,4'-oda) 2 ] and X 2 [M(N 3 )(4,4'-oda) 2 ]NO 3 [M=Cd II ( 3 ) or Co II ( 4 )] were obtained by reactions 4,4'-oxydianiline (4,4'-oda) with Ni(SCN) 2 , Co(SCN) 2 , Cd(N 3 ) 2 and Co(N 3 ) 2 , respectively which have been structurally established by single-crystal X-ray diffraction. Complex 1 contains one-dimensional double-stranded chains comprising 24-membered Ni 2 (4,4'-oda) 2 macrocycles, each formed by two 4,4'-oda ligands and two octahedral Ni II centers. Complex 2 exhibits two-dimensional non-interpenetrating networks consisting of large 48-membered macrocycles each formed by four 4,4'-oda ligands and four octahedral Co II centers. The crystal structures of 3 and 4 are isomorphous and both contain one-dimensional double-stranded chains comprising 24-membered M 2 (4,4'-oda) 2 macrocycles, which are interlinked by w -1,3-azide groups to generate cationic two-dimensional sheets. These sheets are further connected by hydrogen bonds between the amine groups and nitrate ions to furnish three-dimensional networks. Crystal data: complex 1 crystallizes in the monoclinic space group P 2 1 / c with a =11.990(4) Å, b =9.413(4) Å, c =12.827(4) Å, g =116.32(2), V =1297.6(8) Å 3 and Z =2; complex 2 crystallizes in the orthorhombic space group Pbca with a =9.583(2) Å, b =12.738(3) Å, c =21.039(4) Å, V =2568.2(9) Å 3 and Z =4; complex 3 crystallizes in the monoclinic space group C 2/ c with a =23.036(5) Å, b =5.920(1) Å, c =17.800(4) Å, g = 92.67(3), V =2424.8(9) Å 3 and Z =4; complex 4 crystallizes in the monoclinic space group C 2/ c with a = 22.861(5) Å, b =5.812(1) Å, c =17.720(4) Å, g =93.00(3), V =2351.2(8) Å 3 and Z =4. 相似文献
34.
Living polymers are formed by reversible association of primary units (unimers). Generally the chain statistical weight involves
a factor σ < 1 suppressing short chains in comparison with free unimers. Living polymerization is a sharp thermodynamic transition
for σ ≪ 1 which is typically the case. We show that this sharpness has an important effect on the kinetics of living polymerization
(one-dimensional association). The kinetic model involves i) the unimer activation step (a transition to an assembly-competent
state); ii) the scission/recombination processes providing growth of polymer chains and relaxation of their length distribution.
Analyzing the polymerization with no chains but unimers at t = 0 , with initial concentration of unimers M ≳ M
* (M* is the critical polymerization concentration), we determine the time evolution of the chain length distribution and find
that: 1) for M
* ≪ M ≪ M
*/σ the kinetics is characterized by 5 distinct time stages demarcated by 4 characteristic times t1, t2, t3 and t*; 2) there are transient regimes (t
1 ≲ t ≲ t
3) when the molecular-weight distribution is strongly non-exponential; 3) the chain scissions are negligible at times shorter
than t2. The chain growth is auto-accelerated for t
1 ≲ t ≲ t
2 : the cut-off chain length (= polymerization degree 〈n〉w
N
1 ∝ t
2 in this regime. 4) For t
2 < t < t
3 the length distribution is characterized by essentially 2 non-linear modes; the shorter cut-off length N1 is decreasing with time in this regime, while the length scale N2 of the second mode is increasing. (5) The terminal relaxation time of the polymer length distribution, t*, shows a sharp maximum in the vicinity of M*; the effective exponent
is as high as ∼ σ-1/3 just above M*. 相似文献
35.
在极化连续模型框架下比较了线性响应与两种不同态特定方法计算的溶液中Alexa Fluor 350(AF350)分子激发能和光谱移动值的差异. AF350的第一激发态S0→S1电子跃迁属于π→π*跃迁, 主要对应于最高占据分子轨道(HOMO)到最低空轨道(LUMO)的跃迁. 该分子激发态偶极矩大于基态偶极矩, 激发态时溶质溶剂相互作用比基态时更强, 随着溶剂极性增大, 会发生光谱红移的现象. 与实验值相比, 线性响应和两种态特定方法均高估了激发能, 其中以IBSF(Improta-Barone-Scalmani-Frisch)方法得到的激发能最小, 矫正的基态反应场方法(cGSRF)得到的激发能最大. 对于光谱移动值, 3种方法与实验值相比都偏小, 线性响应方法(LR)计算出的误差最大, 而IBSF方法得到的结果与实验值最吻合, 是预测溶液中AF350分子激发能和光谱移动值最准确的方法. 对比了Marcus传统理论和基于约束平衡的非平衡溶剂化理论的结果, 发现后者得到的激发能和光谱移动值更接近于实验值. 相似文献
36.
高速激光通信中接收机与光斑中心很难处于精对准状态,导致水下光通信链路难以稳定建立.首先采用蒙特卡洛仿真统计法分析激光光子在海水中传输的接收光强分布规律,再通过实验对接收端的光斑图像进行采样分析,利用曲线拟合得到接收器位置与接收光强的关系.仿真与实验结果表明:光束经过25 m的水下传输,接收光强分布仍近似为高斯分布.采用非线性估计算法(扩展卡尔曼滤波)与基本状态控制反馈理论,根据接收光强度估计接收器当前位置与最大光强处的距离,通过反馈算法实现接收端与光斑中心的主动跟踪对准.算法仿真结果显示,接收端对准误差在2 mm以下,稳定后接收效率超过98%. 相似文献
37.
38.
39.
从新马克思主义的相对自主性到回归国家学派的潜在自主性、镶嵌自主性构成了国家自主性理论的研究谱系和学术图景。国家利益、官僚组织和国家能力是理解国家自主性内涵的三个核心概念。回归国家学派确立的国家中心主义研究范式是对社会中心论的一种纠正和补充,但其概念界定的模糊性与研究方法的局限性成为国家自主性理论的缺陷和不足之处。 相似文献
40.
银杏叶化学组分群动态FTIR指纹图谱研究 总被引:1,自引:0,他引:1
比较了相同产地不同月份与相同月份不同产地银杏叶的FTIR图谱,研究了银杏叶化学组分群随气候、季节、地域等的差异而呈现出的动态分布规律。结果表明,从4月份到10月份,银杏叶内化学组分群呈现动态分布与变化,其变化在6月16日,9月1日,10月4日3个时段。5月份所采集的不同产地银杏叶的化学组分群分布基本一致。这在银杏叶药材种植质量管理规范(GAP)基地的建设、确保银杏叶原料的稳定性以及其后各类相关指纹图谱的研究及制定等方面具有重要意义。 相似文献