对自感现象中灯泡亮度的研究

本文通过对演示自感现象实验中灯泡亮度的问题讨论 ,对自感现象进行电路分析 ,加深了对自感现象的认识     

Slip-shakedown analysis of a system of circular beams in frictional contact

In automotive components, the cumulative microslip phenomenon is often observed for engine assemblies. This phenomenon results in an accumulation of the relative slips in a preferred tangential direction on the contact interface of two solids under cyclic loadings. A significant relative displacement may occur and leads to the assembly failure. In particular, a global rotation of the bearing shell may result from this mechanism of cumulated slips in conrod big end systems. To discuss this rotation problem, a model of two circular beams in frictional contact and submitted to a periodical rotating load is considered here. The aim is to give some simplified estimates of the critical rotation load based on a slip-shakedown analysis. The discussion holds for Tresca friction and can be extended to Coulomb friction under the assumption of small coupling. The static and kinematic slip-shakedown approaches are discussed. The obtained analytical results are shown to be in agreement with the finite element computations.     

ErYb:氟氧化物玻璃陶瓷的上转换发光特征饱和现象的综合分析

研究了Er3+和Yb3+双掺的氟氧化物玻璃陶瓷在966 nm激光激发下的上转换发光的饱和现象。详细的分析发现了它存在一种能量扩展导致的“特征饱和现象”,也就是说上转换发光强度I随激光功率P而改变的双对数曲线的斜率随着激光光斑的增大而明显增大至正常的多光子关系。还发现布居耗空所导致的“典型饱和现象”也有较大的影响,它导致了logI-logP曲线会随着激光功率的增加而逐渐弯曲,而激光功率的减小会导致“典型饱和现象”也减小甚至完全消失。     

关于否定毛细永动机的一种思考方案——对一个物理问题的回顾与再思考

从一个物理问题的回顾与再思考出发,提出了否定毛细永动机的一种思考方案。     

随机哈密尔顿系统的周期变差解和近不变环面解

本文研究具有随机扰动的哈密顿系统的重现现象,尤其是轨道随机周期变差解和近不变环面解.具体来说,对线性薛定谔方程,我们完整阐述了随机周期变差解何时存在;对随机扰动的近可积哈密顿系统,我们证明了近不变环面的存在性与驱动噪声对应的哈密顿函数的对合性相关.     

大钟拍声的调整实验

阐明大钟拍声的发生原理,并用大钟振动拍的理论模型说明拍的特性,从而控制清晰度。在实验钟上附着质量,根据附着质量位置的不同,能够改变其非对称程度,进一步调整拍频,同时用有限元分析的结果和等效圆环理论计算的结果对比。引入等效圆环理论,通过建立一个理论上带有附加质量的轴对称圆环模型,达到具有和大钟相同的振动特性。根据模型,得到在大钟特定位置附加的质量,以同时调整所需拍的清晰度和周期。在大钟多个位置进行实验,并进行有限元分析,验证了该理论的有效性。     

二甲基亚砜-水混合溶液的等效介电常数特异性研究

在2.45 GHz下利用微扰谐振腔法测量二甲基亚砜(DMSO)-水(H₂O)混合溶液的等效介电常数过程中, 发现混合溶液等效介电常数虚部大于其中任一组分的介电常数虚部的特异现象. 分析表明, 这种特异性现象的发生主要是由于DMSO与H₂O混合后溶液的高频摩擦项大于混合前引起的. 因此, 经典混合物介电常数公式需要进行适当修正才能较好地适用于这类特异性问题计算.     

Dielectric,impedance and modulus spectroscopy of Ta-based layered perovskite

PbBi₂Ta₂O₉ ceramic samples were fabricated by high-temperature mixed oxide method. X-ray diffraction determines the structure as orthorhombic. The scanning electron microscopy confirms the formation of densely packed grains in the sample. The dielectric measurements, complex impedance and complex modulus study were carried out in a frequency range of 1?kHz–1?MHz and a temperature rangeof 25–500°C. The conduction mechanism of the material is discussed in details using variable range hoping, nearest neighbor hopping relaxation model and dc activation energy at two different temperature regimes. From the J-E characteristics studies, the occurrence of non-linear curves endorses the non-Ohmic nature of the material.     

Reflection, transmission and circular dichroism in axially excited slab of a copper thin film helicoidal bianisotropic medium

The reflectance, transmittance and circular dichrosim in a chiral sculptured copper thin film slab of 1000-1600 nm thickness in near infra-red and visible regions based on the relative permittivity of copper in the bulk state and volumetric fraction of copper inclusion of 0.2 are obtained. At higher volumetric fraction of metallic inclusions the reflection (due to low circular Bragg phenomenon) and transmission coefficients (due to increased absorption) are too small, while for thicker slabs numerical instabilities (overflow/underflow) occur in the computation. Therefore it is recommended that the chiral sculptured thin film slab to be considered as a half space.