Theoretical study of spin-forbidden cooling transitions of indium hydride using ab initio methods

The feasibility of spin-forbidden cooling of the In H molecule is investigated based on ab initio quantum chemistry calculations. The potential energy curves for the X~1Σ_(0~+)~+, a~3Π_~(0~-), a~3Π_(0~+), a~3Π_1, a~3Π_2, A~1Π_1, 1~3Σ_(0~-)~+, and 1~3Σ_1~+states of In H are obtained based on multi-reference configuration interaction plus the Davidson corrections method. The calculated spectroscopic constants are in good agreement with the available experimental data. In addition, the influences of the active space and spin–orbit coupling effects on the potential energy curves and spectroscopic constants are also studied. For Re of a~3Π_(0~-), a~3Π_(0~+), a~3Π_1, and a~3Π_2 states, the error from large active space is small. The potential energy curve of the A~1Π_1state is not smooth for small active space. The spin–orbit coupling effects have great influences on the potential well depth and equilibrium internuclear distance of the A~1Π state. The Franck–Condon factors and radiative lifetimes are obtained on the basis of the transition dipole moments of the a~3Π_(0~+) → X~1Σ_(0~+)~+, a~3Π_1 → X~1Σ_(0~+)~+, and A~1Π_1 → X~1Σ_(0~+)~+ transitions. Our calculation indicates that the a~3Π_1( ν'= 0) → X~1Σ_(0~+)~+(ν = 0) transition provides a highly diagonally distributed Franck–Condon factor and a short radiative lifetime for the a3Π1 state, which can ensure rapid and efficient laser cooling of In H.The proposed laser drives a~3Π_1 → X~1Σ_(0~+)~+ transitions by using three wavelengths.     

早龄期混凝土抗裂性环形试验研究进展

早龄期混凝土极易在限制收缩条件下产生裂缝进而影响结构的安全性、耐久性和适用性,因此提供一种简单有效的方法来评估早龄期混凝土在限制收缩条件下的抗裂性,就显得非常重要.由于能够提供一定的约束刚度并易于实验室操作,限制收缩环形试验被广泛应用到混凝土在限制收缩条件下的抗裂性评估.主要从限制收缩环形试验的发展、破坏机理、影响因素三方面进行阐述.通过限制收缩环形试验进行不同目的的混凝土试验研究,推动了限制收缩环形试验的不断发展;破坏机理主要有最大拉应力理论以及基于断裂力学的断裂能机制预测混凝土的开裂;环形试验的影响因素主要有试件几何尺寸,边界条件,混凝土材料性能以及预制裂缝四个方面.最后介绍了一种椭圆环试验方法,可有效评估高约束度下混凝土的抗裂性.     

基于模糊证据推理及改进TOPSIS的多属性群决策方法

针对不同识别框架多属性群决策问题属性准则度量的不确定性、随机性,定义基于梯形模糊数表征的属性准则评价等级相似度量,求解专家决策权重的最优解。对公共识别框架备选方案属性准则采用模糊证据推理过程综合专家评价等级置信度信息;利用可严格区分属性准则评价等级的相似度量,改进TOPSIS方法中备选方案属性准则评价等级置信度距离因子,获取备选方案逼近正负理想解的贴近度。实例分析以某通信企业电信产品市场竞争力评估为例,说明基于模糊证据推理、改进TOPSIS的多属性群决策问题求解过程,从属性准则专家模糊评价等级置信度集中获取直观的待评估产品市场竞争力排序结果,验证该方法解决此类决策问题的可行性与有效性。     

露天爆破震动诱发地下洞室顶板失稳的非线性机理分析

开挖爆破是诱发工程岩体失稳的重要因素.根据露天与地下联合开采特点,将地下洞室顶板简化为水平简支梁,基于非线性理论分析方法建立了露天爆破震动扰动诱发地下洞室顶板失稳的突变理论模型,导出了其失稳判据条件和临界安全厚度,探讨了爆破震动幅值、主频、围岩特性等主要因素对地下洞室顶板临界安全厚度的影响.以甘肃厂坝铅锌矿群采空区顶板安全厚度分析为例,计算得到了露天与地下采场之间顶板的临界安全厚度.研究结果表明:露天爆破扰动诱发地下洞室顶板失稳过程具有非线性和不连续性特征,顶板临界安全厚度不仅取决于岩体工程特性,而且与爆破震动幅值、主频等多重因素有关,这与实际情况是吻合的.     

The drivers of citations in management science journals

The number of citations is becoming an increasingly popular index for measuring the impact of a scholar’s research or the quality of an academic department. One obvious question is: what are the factors that influence the number of citations that a paper receives? This study investigates the number of citations received by papers published in six well-known management science journals. It considers factors that relate to the author(s), the article itself, and the journal. The results show that the strongest factor is the journal itself; but other factors are also significant including the length of the paper, the number of references, the status of the first author’s institution, and the type of paper, especially if it is a review. Overall, this study provides some insights into the determinants of a paper’s impact that may be helpful for particular stakeholders to make important decisions.     

纳米银的神经毒理学效应

纳米银是目前商品化程度最高的纳米材料之一。由于其独特的表面等离子共振性能、优良的抗菌活性,这种纳米材料已被广泛地应用于医药卫生、工业及日常生活等多个领域。随着纳米银应用领域的不断扩展,其生物安全性也受到了越来越多的关注。由于纳米银能够通过跨越血脑屏障等途径进入生物体脑部,因此纳米银的神经毒理学效应受到广泛关注,近年来已成为该领域研究热点之一。本综述总结了纳米银的脑累积效应以及进入脑组织的途径,主要包括经鼻通过嗅神经直接入脑和穿透血脑屏障。纳米银的神经毒性效应包括受暴露动物体的神经行为学改变、脑部的组织病理学效应或神经元和神经胶质细胞的形貌变化,与神经递质水平改变内在作用机制与氧化应激和炎性反应相关。纳米银的粒径、表面涂层和银离子释放是影响纳米银神经毒性的关键因素。本文最后提出当前纳米银神经毒理学研究中存在的问题及今后的研究方向。     

3D Casson nanofluid flow over slendering surface in a suspension of gyrotactic microorganisms with Cattaneo-Christov heat flux

A mathematical model is proposed to execute the features of the non-uniform heat source or sink in the chemically reacting magnetohydrodynamic (MHD) Casson fluid across a slendering sheet in the presence of microorganisms and Cattaneo-Christov heat flux. Multiple slips (diffusion, thermal, and momentum slips) are applied in the modeling of the heat and mass transport processes. The Runge-Kutta based shooting method is used to find the solutions. Numerical simulation is carried out for various values of the physical constraints when the Casson index parameter is positive, negative, or infinite with the aid of plots. The coefficients of the skin factors, the local Nusselt number, and the Sherwood number are estimated for different parameters, and discussed for engineering interest. It is found that the gyrotactic microorganisms are greatly encouraged when the dimensionless parameters increase, especially when the Casson fluid parameter is negative. It is worth mentioning that the velocity profiles when the Casson fluid parameter is positive are higher than those when the Casson fluid parameter is negative or infinite, whereas the temperature and concentration fields show exactly opposite phenomena.     

化学试题难度影响因素的实证研究

依据高考化学试题的特点,厘清影响试题难度主要因素的要素特征,并据此编制相应的变式题进行抽样测试。统计分析数据表明各因素在试题中的不同表现形式对试题难度有着显著性影响。以“信息呈现方式”这一影响因素为例,分析并研究了同一因素的不同表现形式对试题相对难度变化的影响,为后续试题难度的建模研究奠定了基础。     

Chiral Extrapolation of Lattice Data of Λ_b→Λ_c Form Factors

An extrapolation to the physical limit for the lattice data of Λ_b →Λ_c form factors computed in the nonphysical region is made in this work through a class of fitting functions proposed by us with nonlinear dependence on m2/π derived in the chiral perturbative theory(ChPT) and the heavy quark effective theory(HQET) framework. Then the results are applied to calculate the differential and integrated Λ_b →Λ_c semileptonic decay rates. Meanwhile, a comparison between our results and those obtained through the extrapolation functions with naive linear dependenceon m2/π is made.It is shown that the difference between the extrapolated central values of these two cases is about 5%.The total uncertainties(depending on the momentum transfer q~2) in the linear case are about 5% ～10%(caused by the uncertainties of lattice data) and those in the nonlinear case are about 10% ～ 20%(caused by the uncertainties of both lattice data and input parameters in Ch PT and HQET). More accurate lattice data and parameters in ChPT and HQET are needed to reduce the uncertainties of the extrapolated results.