核间距对氢分子双电离的影响

本文利用经典三维系综模型,研究了超强线偏振激光作用下核间距对氢分子双电离的影响。结果表明,氢分子双电离率随核间距变化。随着核间距的增大,氢分子双电离率先增大,后减小,在R=4a．u．时取得最大值。     

电离平衡与沉淀反应实验的绿色化改进

对电离平衡与沉淀反应进行了绿色化改进.新型实验把试剂用量降低至常规实验用量的1/10以下,实验既取得了良好效果,又减少了有毒试剂对学生和环境可能造成的潜在危险.新型实验已经推广应用于目前的实验教学中.     

一类有连续生殖竞争系统的定性分析

本文对一类有连续生殖竞争系统的平衡问题及极限环问题进行详细讨论,所采用的方法是:用图解法讨论平衡问题,简化传统的分析法;用曲率法判别等倾线的关系,简单明了;将模型的平衡点作为动点来讨论,以求结论更富有生态意义。     

Advanced oxidation processes of decomposing dichloroacetic acid and trichloroacetic acid in water

We studied the decomposition of two haloacetic acids （HAAs）, dichloroacetic acid （DCAA） and trichloroacetic acid （TCAA）, in water by single oxidants ozone （O3） and ultraviolet radiation （UV） and the advanced oxidation processes （AOPs） constituted by the combinations of O3/UV, H2O2/UV, O3/H2O2, and O3/H2O2/UV. The concentrations of HAAs were analyzed at specified time intervals to track their decomposition. Except for O3 and UV, the four combined oxidation processes remarkably enhance the decomposition of DCAA and TCAA owing to the generated very reactive hydroxyl radicals. The fastest decomposition process is O3/H2O2/UV, closely followed by O3/UV. DCAA is much easier to decompose than＇ TCAA. The kinetics of HAA decomposition by O3/UV can be described well by a pseudo first-order reaction model under a constant initial dissolved O3 concentration and fixed UV radiation. Humic acids and HCO3 in the reaction system both decrease the decomposition rate constants for DCAA and TCAA. The amount of H2O2 accumulates in the presence of humic acids in the O3/UV process.     

氢硫酸强度的热力学分析

本文应用热学原理对氢硫酸的强度及逐级电离平衡进行了讨论,有助于无机化学教学和学生学习。     

C_2(a~3Π_u)自由基与C_2H_6反应的动力学计算

用密度泛函理论B3LYP方法,在6-311G(d,p)基组下,优化得到C2(a3Πu)+C2H6→C2H+C2H5反应各驻点(反应物、过渡态和产物)的几何构型,对其进行振动分析,并计算了它们的能量.在CCSD/6-311G(d,p)水平下单点能计算得到的反应势垒为24.47kJ/mol.采用传统过渡态理论,计算了温度范围50K～2000K的反应速率常数.实验结果表明,随着反应温度的升高,反应速率逐渐升高,反应的平均活化能也随着温度的不断升高而不断增大.     

Monte Carlo模拟在聚合反应速率常数估算中的运用

1 Introduction It is i mportant to study polymerization mechanisminpolymerization engineering. Obtaining kinetic data isthe key step for establishing polymerization mechanismand understanding elementary reactions . The kineticdata contains two groups of data ,i.e.,the rate andreaction order .The rate ,especially the rate constant ,is i mportant and to be esti mated assuming that the or-der of the reactionis known.Furthermore ,esti mationof rate constants for polymerization is an active anddif…     

超短脉冲激光烧蚀SiO2材料的库仑爆炸模型理论分析

基于动理论Vlasov-Poisson方程,建立了超短脉冲激光引起的SiO2材料表面库仑爆炸烧蚀机理的理论模型,计算了在多光子吸收与雪崩2种电离机制下材料中自由电子的非平衡态分布,并在此基础上定量分析了自洽电场导致的材料表面库仑爆炸的机理及激光参数对材料表面烧蚀的影响.结果表明,在飞秒激光作用下自由电子弛豫时间不是常数...     

球磨制备Mg-In-Zn三元固溶体的储氢性能及机理

采用“烧结-球磨”方法制备Mg0．92 In0．05 Zn0．03三元固溶体合金,减小了Mg的晶格常数.利用粉末X-射线衍射分析合金的相组成、微观结构和吸放氢过程的相转变,通过扫描电镜观察合金的微观形貌及相分布.采用体积法测定合金的等温吸放氢曲线（ PCT）和动力学曲线,确定了合金的吸放氢反应焓变、熵变及氢化反应激活能.结果表明： Mg0．92 In0．05 Zn0．03三元固溶体具有良好的活化性能和动力学性能,脱氢反应焓降低至-68．6 kJ/mol H2.     

废水处理氨氮技术研究

水中的氨多以氨离子（NH4^＋）和游离氨（NH3）的状态存在,两者保持平衡关系为NH3＋H2O→NH4^＋ ＋OH^-这一平衡关系受PH值影响,在不同PH值和水温条件下,游离氨易于水中逸出,只要采用一般的空气吹脱技术,可以达到除氨目的。     

二轴倒立摆系统的平衡控制研究

以固高GIP-200L二轴倒立摆实验系统为对象,研究了二轴倒立摆系统的平衡控制问题。首先利用拉格朗日方法建立了二轴倒立摆系统的数学模型,利用极点配置方法进行控制器设计,然后在Matlab环境下利用Simulink对倒立摆系统进行了非线性仿真研究。实验结果表明本文所设计的控制器能够达到倒立摆系统的平衡控制要求。     

Reconstruction of symmetric models composed of analytic curves and surfaces from point cloud

This paper presents a method to reconstruct symmetric geometric models from point cloud with inherent symmetric structure. Symmetry types commonly found in engineering parts, i.e., translational, reflectional and rotational symmetries are considered. The reconstruction problem is formulated as a constrained optimization, where the objective function is the sum of squared distances of points to the model, and constraints are enforced to keep geometric relationships in the model. First, the explicit representations of symmetric models are presented. Then, by using the concept ofparameterized points （where the coordinate components are represented as functions rather than constants）, the distances of points to symmetric models are deduced. With these distance functions, symmetry information, for both 2D and 3D models, is uniformly represented in the process of reconstruction. The constrained optimization problem is solved by a standard nonlinear optimization method. Owing to the explicit representation of symmetry information, the computational complexity of our method is reduced greatly. Finally, examples are given to demonstrate the application of the proposed method.     

结晶器数学模型的广义矩变换解法

结晶器数学模型由粒数衡算方程、溶质质量衡算方程、晶体生长和成核动力学方程及相应的初值与边界条件组成，为一组偏微分一常微分方程。把矩变换的定义从整数域扩展到实数域并扩展定义晶体尺寸后。矩变换能将与粒度有关的生长的结晶器模型化为一组常微分方程。对Bransom模型、ASL模型、Strong模型描述的三种结晶器模型进行变换后导出了相应的常徽分方程组，为最一般的结晶器数学模型的求解提供一种通用的方法。以分批式结晶器为例。给出了一个算例。     

高温下钼的弹性和热力学性质第一性原理计算

通常晶体熔化时弹性常数C44和(C11-C12)/2就将消失,由此提出晶体熔化的力学判据.本文采用第一性原理研究了高温下钼的弹性性质,并且得出结论:在计算温度范围内钼没有熔化并且弹性常数C11、C12、C44随着温度的升高逐渐减小.最后采用准谐德拜模型方法对钼的热力学性质进行了研究,得出了比较好的结论.     

电信收入保障中数据稽核平衡关系式的研究

在收入保障实践基础上提出了一种基于平衡关系式的数据稽核方法,对平衡关系式模型及其中的数据实体模型进行了形式化定义和业务描述,最后以某省电信收入保障项目——财务稽核系统进行了实际验证．     

Measurement of the ionization cross section of Rydberg state of benzene molecules

The frequency-tunable light, which was produced by using YAG laser to pump the dye rhodamine 590/610, was used to measure the ions number in ionization of the benzene molecules Rydberg state 5Rg|10 as a function of the light intensity. Fitting themeasured data by using the deduced equation from the method of spatial integration, the ionization cross section of single photon of molecule benzene 5Rg|10 was obtained to be 2.1×10-19,cm2 approximately.     

XN(X=F,Cl,Br,I)系列物种的理论研究

通过优化构型和计算电离能对XN(X=F,Cl,Br,I)系列化合物进行了详细深入的讨论.分别采用HF、B3LYP和MP2方法在STO-3G,3-21G,6-311 G(2df,pd)和SDB-aug-cc-PVTZ基组水平上对分子构型进行优化,通过与文献数据的比照,最后选出B3LYP/SDB-aug-cc-PVTZ计算结果与实验值符合得最好.采用外壳层格林函数方法(OVGF)和G2方法分别计算了分子的垂直电离能和绝热电离能.     

政府公用土地使用权拍卖与磋商机制研究

为使政府公有土地拍卖价格与用途达到效益均衡,提出了拍卖筛选-磋商机制。首先分析了政府土地使用权拍卖特点,阐述了拍卖价概率分布特点;其次提出了4元组拍卖-磋商模型及其流程,阐述了拍卖阶段与磋商阶段议价均衡特点;然后分析了政府与房地产商在交易后的评价估计体系,并进行了总结。     

弱电解质溶液无限稀时的摩尔电导测定

通常认为 ,弱电解质溶液无限稀时的摩尔电导Λ0 不能直接测定 ,它只能通过相关强电解质溶液无限稀时的摩尔电导及离子独立移动定律计算得出 .事实上 ,通过弱电解质溶液的电导率测定 ,不仅可以确定弱电解质的电离平衡常数 ,而且可以确定弱电解质无限稀时的摩尔电导 .与此同时 ,也发现了弱电解质溶液的浓度与其电导率之间的关系方程     

Covariate Balance in Bayesian Propensity Score Approaches for Observational Studies

Abstract

Bayesian alternatives to frequentist propensity score approaches have recently been proposed. However, few studies have investigated their covariate balancing properties. This article compares a recently developed two-step Bayesian propensity score approach to the frequentist approach with respect to covariate balance. The effects of different priors on covariate balance are evaluated and the differences between frequentist and Bayesian covariate balance are discussed. Results of the case study reveal that both the Bayesian and frequentist propensity score approaches achieve good covariate balance. The frequentist propensity score approach performs slightly better on covariate balance for stratification and weighting methods, whereas the two-step Bayesian approach offers slightly better covariate balance in the optimal full matching method. Results of a comprehensive simulation study reveal that accuracy and precision of prior information on propensity score model parameters do not greatly influence balance performance. Results of the simulation study also show that overall, the optimal full matching method provides the best covariate balance and treatment effect estimates compared to the stratification and weighting methods. A unique feature of covariate balance within Bayesian propensity score analysis is that we can obtain a distribution of balance indices in addition to the point estimates so that the variation in balance indices can be naturally captured to assist in covariate balance checking.