Modeling of Solute-Solvent Interactions Using an External Electric Field—From Tautomeric Equilibrium in Nonpolar Solvents to the Dissociation of Alkali Metal Halides

An implicit account of the solvent effect can be carried out using traditional static quantum chemistry calculations by applying an external electric field to the studied molecular system. This approach allows one to distinguish between the effects of the macroscopic reaction field of the solvent and specific solute–solvent interactions. In this study, we report on the dependence of the simulation results on the use of the polarizable continuum approximation and on the importance of the solvent effect in nonpolar solvents. The latter was demonstrated using experimental data on tautomeric equilibria between the pyridone and hydroxypyridine forms of 2,6-di-tert-butyl-4-hydroxy-pyridine in cyclohexane and chloroform.     

1,3,5-Triaza-7-Phosphaadamantane (PTA) as a 31P NMR Probe for Organometallic Transition Metal Complexes in Solution

Due to the rigid structure of 1,3,5-triaza-7-phosphaadamantane (PTA), its ³¹P chemical shift solely depends on non-covalent interactions in which the molecule is involved. The maximum range of change caused by the most common of these, hydrogen bonding, is only 6 ppm, because the active site is one of the PTA nitrogen atoms. In contrast, when the PTA phosphorus atom is coordinated to a metal, the range of change exceeds 100 ppm. This feature can be used to support or reject specific structural models of organometallic transition metal complexes in solution by comparing the experimental and Density Functional Theory (DFT) calculated values of this ³¹P chemical shift. This approach has been tested on a variety of the metals of groups 8–12 and molecular structures. General recommendations for appropriate basis sets are reported.     

水性颜料体系无树脂色浆的制备与应用

中性墨水属于热力学上不稳定的颜料悬浮体系,选择低黏度、高稳定性的色浆是保证墨水体系分散稳定性的重要手段之一。基于此,以颜料炭黑和酞菁蓝为着色剂,配合超分散剂(EK43)与协同增效剂(BM10),制备了两款适用于中性墨水体系的无树脂色浆。首次从色浆粒径与体系分散稳定性角度出发,确定了EK43、BM10用量以及最佳研磨时间,并对其理化性能、稳定性与书写性能进行分析测试。结果表明:在黑色浆中添加质量分数10.0%的EK43、2.5%的BM10,研磨时间为90 min;在蓝色浆中添加质量分数8.0%的EK43、2.0%的BM10,研磨时间为120 min时,两种色浆的粒径与分散稳定性均达到最佳。所制备的无树脂色浆颜料固含量高、黏度较低、储存稳定性好、着色力强,以其调配的中性墨水书写性能良好,且具有较好的离心稳定性和耐热稳定性。     

阳极结构调整对稀土电解槽的影响

以目前使用的6 k A稀土电解槽为研究对象,采用实验验证与数值模拟计算相结合的方式对采用不同阳极结构的稀土电解槽进行了全面分析讨论。使用斜角切割阳极片可以在维持电解槽槽电压、氧化物利用率、产品合格率等技术指标不变的情况下,克服传统正交切割阳极片在使用过程中随着阳极片反应消耗造成电流效率降低及缩短石墨坩埚使用寿命的现象。其可作为稀土电解槽工艺改造的一个发展方向。     

放射性废物微波处理装置有效输出功率的测定

以微波为热源处理放射性废物的相关技术和装备的研究,在国外已经达到较高水平,在我国的相关研究较少。微波加热即物料在微波场中吸收消耗微波能量,并转化为热能用于物料温度升高。对于物料的处理效果主要与微波的有效输出功率有关。参考Schillman法测定了包括放射性废物微波处理装置的微波炉的有效输出功率,且经验证测定结果准确。微波有效输出功率的确定将对放射性废物微波处理工艺的研究打下基础。     

Rime- and glaze-ice accretion due to freezing rain falling vertically on a horizontal thermally insulated overhead line conductor

A theory of atmospheric icing due to freezing rain on an overhead line conductor (OHLC) is developed. The rain falls vertically on a horizontal OHLC that is thermally insulated. It is assumed that the collection efficiency of the accretion surface is unity and that this surface is in thermodynamic equilibrium with the environment.

For air temperature T_A 0°C and raindrop temperature T_D 0°C, the freezing rain accretes as rime ice, provided that the temperature of the ice surface T_l < 0°C. The evolution equation governing the mass transfer at the accretion surface is solved analytically, yielding the shape of the rime-ice surface. Equations governing the thermal state of the rime-ice deposit are also given. These determine the onset of wet growth or glaze accretion at the upper stagnation line during suitable environmental conditions.

For environmental conditions producing an ice surface at temperature T_l = 0°gC, the freezing accretes as glaze. Equations governing the heat and mass transfer at the surface determine the shape of the glaze surface and the downward viscous motion of the unfrozen water. For T_D < 0°C, glaze evolution equations are developed for T_A 0°C and T_A 0°C. Analytical solutions of these equations are obtained. In particular, when T_D < −T_A < 0°C, the evolution equation predicts a novel limiting growth that is triangular in shape. Further study of the mass and heat transfer conditions, in the neighborhood of this final stage of glaze accretion, shows that it is maintained in thermodynamic equilibrium with its warm air environment.     

含噪双稳杜芬振子矩方程的分岔与随机共振

研究了含噪声的双稳杜芬振子矩方程的分岔与随机共振的关系，并根据它们的关系, 从另 一个角度揭示了随机共振发生的机制. 首先在It?方程的基础上，导出了双稳杜芬振子在白噪声和弱周期信号作用下的矩方程，其次以噪声强度 为分岔参数分析了矩方程的分岔特性，再次分析了矩方程的分岔与双稳杜芬振子随机共振 之间的关系，最后根据该对应关系从另一种观点提出了双稳杜芬振子随机共振的机制，该 机制是由于以噪声强度为分岔参数的矩方程发生了分岔，而分岔使得原系统响应均值的能量分布发生了转移，使能 量向频率等于输入信号频率的分量处集中，使得弱信号得到了放大，随机共振发生了.     

THREE-DIMENSIONAL ANALYSIS OF A MAGNETOELECTROELASTIC HALF-SPACE UNDER AXISYMMETRIC TEMPERATURE LOADING 1)

考虑力-电-磁-热等多场耦合作用, 基于线性理论给出了磁-电-弹性半空间在表面轴对称温度载荷作用下的热-磁-电-弹性分析, 并得到了问题的解析解. 利用Hankel 积分变换法求解了磁-电-弹性材料中的热传导及控制方程, 讨论了在磁-电-弹性半空间在边界表面上作用局部热载荷时的混合边值问题, 利用积分变换和积分方程技术, 通过在边界表面上施加应力自由及磁-电开路条件, 推导得到了磁-电-弹性半空间中位移、电势及磁势的积分形式的表达式. 获得了磁-电-弹性半空间中温度场的解析表达式并且给出了应力, 电位移和磁通量的解析解. 数值计算结果表明温度载荷对磁-电-弹性场的分布有显著影响. 当温度载荷作用的圆域半径增大时, 最大正应力发生的位置会远离半无限大体的边界; 反之当温度载荷作用的圆域半径减小时, 最大应力发生的位置会靠近半无限大体的边界. 电场和磁场在温度载荷作用的圆域内在边界表面附近有明显的强化, 而磁-电-弹性场强化区域的强化程度跟温度载荷的大小和作用区域大小相关. 本研究的相关结果对智能材料和结构在热载荷作用下的设计和制造具有指导意义.     

Critical Reynolds number in plasma flows on a stabilized plasmatron section

A technique for determining the criterion of transition from the laminar to the turbulent flow regime on a stabilized plasmatron channel section is proposed. The technique uses experimental data and the methods of numerical simulation of plasma flows. A criterial generalization of the experimental data which for the first time makes it possible to establish the boundary of transition from the laminar to the turbulent flow regime on a stabilized plasmatron channel section is proposed. The experimental results are in good agreement with the theoretical dependences derived in the study. A curve (analog of the neutral curve) separating the domains of existence of laminar and turbulent plasma flows in a cylindrical channel is constructed in the space of the plasmatron working parameters.Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, 2004, pp. 49–61. Original Russian Text Copyright © 2004 by Sinkevich and Chikunov.     

An Overview on Non-Ideal Vibrations

We analyze the dynamical coupling between energy sources and structural response that must not be ignored in real engineering problems, since real motors have limited output power.