A new method for the derivation of exact vibration-rotational kinetic energy operator in internal coordinates

An efficient angular momentum method is presented and used to derive analytic expressions for the vibration-rotational kinetic energy operator of polyatomic molecules.The vibration-rotational kinetic energy operator is expressed in terms of the total angular momentum operator J,the angular momentum operator J and the momentum operator p conjugate to Z in the molecule-fixed frame Not only the method of derivation is simpler than that in the previous work,but also the expressions ot the kinetic energy operators arc more compact.Particularly,the operator is easily applied to different vibrational or rovibrational problems of the polyatomic molecules by variations of matrix elements Gn of a mass-dependent constant symmetric matrix     

Normal coordinate treatment of actinide(IV)-hexabromides

Molecular force field studies of hexabromo-thorates(IV) and-uranates(IV) have been carried out using four different force field models. Weighted least square adjustment has been used to fit the observed frequencies. Mean amplitudes of vibration have also been calculated at 0°K and 298°K. The trends of force constants and mean amplitudes have also been discussed.

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Normal-Koordinaten Berechnungen an Actiniden(IV)-hexabromiden

Zusammenfassung Es wurden für die Rechnungen an Hexabromo-thoraten(IV) und-uranaten(IV) vier verschiedene Modelle herangezogen. Die beobachteten Frequenzen wurden mittels gewichteter Kleinster-Fehlerquadrat-Methode angepaßt. Die Trends bei den Kraftkonstanten und den mittleren Amplituden der einzelnen Verbindungen werden diskutiert.

     

Partial molal volumes of ions in organic solvents from ultrasonic vibration potential and density measurements. III. Dimethylsulfoxide

The partial molal volumes of Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Cl^–, Br^–, I^–, and NO ₃ ^- in DMSO at 25°C have been determined from ultrasonic vibration potential data and density data for solutions of uni-univalent electrolytes. Hepler's semiemprirical equation has been used to split ionic partial molal volumes into geometric and electrostrictive contributions. The results obtained in this work confirm the conclusion of our previous studies, namely, that the contribution of electrostriction is essentially determined by the properties of that layer of atoms, 0.3 to 0.4 nm thick, in contact with the ion and by the degree of steric hindrance of the poles of the dipole of the solvent molecule. On the other hand, the geometric contribution depends on the size of the solvent molecule and also on the arrangement of the solvent molecules about the ions. It is shown that the geometric contribution to the partial molal volume of ions is largely increased when ions cannot come close enough to the poles of the solvent-molecule dipole, owing to steric hindrance.     

Internal dynamics of the LaI3 molecule. II. Thermal average structure of the molecule and mean square vibration amplitudes

The structural parameters of the effective r _g configuration of the LaI₃ molecule were calculated using the DFT/B3LYP method. The difference between the calculated values of r _e (La-I) and r _g (La-I) is mostly due to the anharmonicity of the ν₁ and ν₂ vibrations and does not exceed the error in determining the distance r _g (La-I) in the electron diffraction experiment. Inclusion of the anharmonicity of the ν₂ and ν₄ deformation vibrations in calculations leads to decreased amplitudes l(I…I) and shrinking effect δ(I…I) compared to the respective values obtained in the harmonic approximation. The LaI₃ molecule proved to be more rigid than predicted by B3LYP calculations.     

次级源和误差传感器布放对带弹性障板的充液直管声振复合有源控制的影响*

针对充液管路系统噪声有源控制问题,研究了次级源和误差传感器布放对带弹性障板的充液直管管路系统有源消声与有源消振复合控制效果的影响。基于声固耦合方法建立了带弹性障板的充液直管管路系统的有限元模型,在声激励下对比了次级声源布放对系统有源消声性能的影响,并在组合激励下分析了次级力源、次级声源和误差传感器布放对系统复合有源控制的影响。结果表明,非对称分布的次级声源容易激起管壁振动,进而带动障板振动,导致有源消声效果不佳;采用对称分布的次级声源可使低频段的降噪量提高10 dB以上。复合有源控制可进一步提升全频段的控制效果。通过增加振动误差传感器数量,可使绝大多数频点的降噪量提高1~20 dB不等。此外,在管壁上布放的两圈次级力源的间距小于管壁振动波长的1/4,且都不位于管壁振动节点附近时控制效果更好。     

振动噪声等高图的电驱动桥噪声预测及优化*

在项目开发前期通过优化电驱动桥扭矩特性的设计,可以规避噪声大问题。根据电驱动桥台架在对应扭矩下的振动噪声特性,提出了一套稳定高效的测试流程和分析方法。首先设计了一套完整的试验流程,制定了精准的数据分析方法。然后绘制出能够全面反映电驱动桥振动噪声特性的等高图。最后利用电驱动桥台架的振动噪声等高图,准确评估电驱动桥加速工况下振动噪声风险,为主机厂和电驱动桥零部件企业提供电驱动桥扭矩特性设计前期指导。利用该方法成功识别到某电驱动桥匀速及加速工况下电机及齿轮的啸叫问题。通过优化电驱动桥扭矩特性设计,电机48阶噪声峰值降低了8.5dB(A),确认该方法准确可靠,具备推广应用价值。     

随机振动数值仿真中基础激励的自动反馈识别

利用ANSYS的APDL(ANSYS Parametric Design Language)语言的强大功能,结合工程实际问题,实现了随机振动试验数值仿真计算中基础输入功率谱的自动反馈识别．反馈过程中使用多个表格来存储基础输入谱,突破了基础输入谱只能用50个以内的数据点来描述的限制,故可以一次性完成基础输入谱的反馈识别,大大提高计算效率与精度．     

Stability and vibration of a helical rod constrained by a cylinder

The stability and vibration of an elastic rod with a circular cross section under the constraint of a cylinder is discussed. The differential equations of dynamics of the constrained rod are established with Euler’s angles as variables describing the attitude of the cross section. The existence conditions of helical equilibrium under constraint are discussed as a special configuration of the rod. The stability of the helical equilibrium is discussed in the realms of statics and dynamics, respectively. Necessary conditions for the stability of helical rod are derived in space domain and time domain, and the difference and relationship between Lyapunov’s and Euler’s stability concepts are discussed. The free frequency of flexural vibration of the helical rod with cylinder constraint is obtained in analytical form. The project supported by the National Natural Science Foundation of China (10472067). The English text was polished by Yunming Chen.     

A2B模型阻尼受迫振动方程组的通解

导出了A2B模型阻尼受迫振动方程组的通解,并讨论其算例和图像.     

碱金属氟化物对掺Yb3+氟磷酸盐玻璃析晶稳定性和光谱性质的影响

研究了碱金属氟化物对掺Yb3 氟磷玻璃的光谱性质和析晶稳定性能的影响.运用倒易法计算了Yb3 的发射截面.结果显示,LiF的引入对吸收和发射截面的提高作用较大并出现最佳引入量极值,其次为KF.碱金属氟化物的引入可提高二元体系的析晶稳定性能,使玻璃网络结构得到改善;拉曼光谱显示二元体系中引入YbF<,3>后玻璃网络结构得到增强,而在引入碱金属氟化物的三元体系中掺杂YbF<,3>后破坏了网络完整性,降低系统析晶稳定性能.