CO2与HCN,NH3,H2O分子络合物的从头计算研究

用ab initio能量梯度法(3-21G基组)分别优化CO_2与HCN、NH_3、H_2O_3个分子络合物的平衡几何构型。结果表明HCN、NH_3和H_2O中的N或O原子与CO_2中的C原子之间形成较弱的范德华键,三者的范德华键键长分别为0.2865、0.2775、0.2543nm,稳定化能分别为14.8、27.0、31.2kJ·mol~(-1),3个分子络合物的构型都呈T型,对3个分子络合物的稳定化能的能量分解研究表明它们的形成主要靠静电作用能。     

信用组合风险度量研究

我国商业银行在信用组合风险管理方面还比较薄弱，虽然国外已有一些较为成熟的信用组合风险管理模型，但是很难在中国直接应用。另一方面，早期的信用组合风险往往只是单独考虑个别资产的风险，没有考虑资产之间的违约相关性，造成风险度量的偏差。本文在考虑了违约相关性的基础上，基于Logit回归分析，利用微模拟的方法，提出了一个符合中国商业银行资产特点的信用组合风险度量模型。     

Propagation of Multidimensional Ion-Acoustic Waves in Multicomponent Plasmas with Negative Ions

We made an attempt to study the propagation of multidimensional ion-acoustic waves in multicomponent plasmas that include negative ions by deriving a Kodomtsev-Petviashvili (K-P) equation. The negative ions, as expected, introduce the precursor on the propagation because of which the need arises to derive a modified K-P equation with higher order non-linearity. We have examined a number of solitons like waves and supported the results by numerical simulation. The results reveal the existence of compressive and rarefactive solitary waves which are comparable with those of one-dimensional solitary waves in plasmas with negative ions except that multidimensional propagation of ion-acoustic waves is more involved than unidirectional propagation.     

Frequency response of W-band pulsed impatts operating over extended ambient temperature

Frequency response of W-band Publsed IMPATT diodes operating over varying ambient temperature has been discussed in details. A method has been suggested to compensate the chirp fluctuation with the ambient temperature. Also discussed quantiatively the control of chirp bandwidth by bias current ramping.     

Locally best rotation-invariant rank tests for modal location

For a general class of unipolar, rotationally symmetric distributions on the multi-dimensional unit spherical surface, a characterization of locally best rotation-invariant test statistics is exploited in the construction of locally best rotation-invariant rank tests for modal location. Allied statistical distributional problems are appraised, and in the light of these assessments, asymptotic relative efficiency of a class of rotation-invariant rank tests (with respect to some of their parametric counterparts) is studied. Finite sample permutational distributional perspectives are also appraised.     

Morphology and cation local structure in a blend of copper-neutralized carboxy-terminated polybutadiene and poly(styrene-co-4-vinylpyridine)

Carboxy-terminated polybutadiene neutralized with Cu²⁺ (CuPBD) and its blend with poly(styrene-co-4-vinylpyridine) (SVP) were examined by differential scanning calorimetry (DSC), transmission electron microscopy (TEM), small-angle x-ray scattering (SAXS), and extended x-ray absorption fine structure (EXAFS) spectroscopy. The DSC results indicate that in the blend substantial mixing occurs in the CuPBD-rich phase, although complete miscibility is not achieved, and the SVP-rich phase remains relatively pure. The TEM micrographs indicate that the morphology, while irregular, is reasonably described as bicontinuous, with a domain size of order 100 nm. The SAXS patterns show that the ionic aggregates present in CuPBD are destroyed upon blending, which is interpreted as being due to steric hindrances between ionic groups coordinated to vinylpyridine nitrogens. The EXAFS radial structure function of the blend exhibits a marked decrease in the Cu-Cu peak in comparison with CuPBD, indicating a change in local structure upon blending. The results indicate that some of the SVP is miscible with CuPBD owing to complexation between the pendant pyridine groups and the Cu²⁺ ions, which disrupts the ionic aggregates. However, the two materials are not fully miscible, leading to a rather coarse two-phase morphology.     

Oxidative behavior and relative reactivities of some unsaturated compounds towards hexachloroiridate(IV) in perchloric acid medium

The kinetics of the oxidation of styrene, cinnamic acid, and some of their substituted derivatives by hexachloroiridate(IV) in dimethyl formamide–water mixtures and in the presence of perchloric acid have been investigated. The reactions appear to proceed via the formation of an unstable intermediate 1:1 complex between iridium(IV) and the substrate, followed by the decomposition of the complex in the rate‐determining step. Correlation with σ yielded ρ values of ?4.0 and ?3.5 which suggests the formation of a cationic intermediate in the rate‐determining step of the reaction. Subsequent cleavage of the carbon–carbon bond yielded the product aldehydes. Thermodynamic and activation parameters associated with the equilibrium and the rate‐determining steps were also evaluated. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 411–417, 2002     

Recursiveness of zero structures for system matrices of interconnected linear systems via module theoretic tools

The importance of the zeros of multivariable linear systems is well-known in terms of measure obstructions to the controllability and the observability. In this paper, a recursive decomposition of interconnected systems is outlined by taking into account the sequential structure of the connections. The paper extends the coordinate, module-theoretic studies from the elementary algebraic systems theory to include the case of such linear interconnected systems which need not to be controllable or observable. Also, the properties of controllability and observability, the decoupling zeros and the signal bloking issues are characterized.     

(4-溴甲基双环[4.4.1]-1,3,5,7,9-十一碳五烯基-3-)甲醇环氧化反应机理的理论研究

采用量子化学的密度泛函理论(DFT),在B3LYP/6 31G*水平上研究了(4 溴甲基双环[4. 4. 1] 1, 3, 5,7, 9 十一碳五烯基3 )甲醇环氧化反应机理,在对反应物和产物几何结构优化的基础上,搜索优化了反应的过渡态结构,通过振动分析和内禀反应坐标(IRC)跟踪方法对过渡态及其所处的反应路径进行了确认,并用电荷密度拓扑分析方法考察了反应过程中旧键断裂和新键形成的细节.计算结果表明,该反应中的消除反应和成环反应是协同进行的,溴化氢消除反应中的氢来自与O( 22 )相连的羟基氢,反应的活化势垒为139. 2kJ/mol,反应放热25. 1kJ/mol.     

Preparation and thermal characterization of the glass transition temperatures of sulfonated polystyrene-metal ionomers

The glass transition temperatures and heat capacity changes in the transition region are reported for six sulfonated linear polystyrenes in the hydrogen form, H-SPS, in the 3.4–20.1 mol % sulfonation range and 76 metal SPS ionomers in the 3.4–12.8 mol % range. The metals are those which interact predominantly ionically and include +1, +2, and +3 ions of the alkali metal, alkaline earth, and rare earth (lanthanide) series. The results show the effect of H₂O or coordinating ligands on glass transition temperatures (T_g) and the importance of eliminating it to obtaining reproducible values for T_g and ΔC_p. The T_g values of dry M-SPS ionomers depend only on the sulfonation level despite wide variation in metal ion charge and size. The variation of ΔC_p with sulfonation level is interpreted as showing that at high levels a few unsulfonated styrene units adjacent to sulfonated ones are constrained, presumably by clustering, from participation in the polystyrene-like cooperative rearrangements in the transition region.