混凝土箱梁相似模型结构噪声对比分析*

为探讨混凝土箱梁噪声的时变特性,以京沪高铁32 m混凝土简支箱梁为原型,制作了1:10的缩尺模型,通过模态试验的方法验证箱梁模型与原型的相似关系,通过声学试验验证箱梁声学计算模型的正确性。然后,建立了箱梁缩尺模型与原型两种计算模型,利用有限元和边界元法求出两种模型的瞬态结构噪声。研究发现,箱梁缩尺模型与箱梁原型的材料参数满足一定关系,模型试验的方法能够验证箱梁模型与箱梁原型之间符合相似关系,箱梁模型的振动噪声测试结果能真实反映原型振动噪声水平。两种模型的结构噪声在时域内声压级及对应场点的声压存在一定相似关系。该研究可为箱梁缩尺模型结构噪声反演至箱梁原型提供依据,所采用的方法和得到的结果对桥梁结构振动与声辐射实验研究具有参考作用。     

基于计数法测量激光多普勒测速仪的测速精度

为了测量所设计的激光多普勒测速仪(LDV)的测量精度,用均匀转动的斩波片代替高精度的转台作为标准的速度源,并基于单片机AT89S52,采用光计数的方法测量斩波片上某一固定位置的切向运动速度,LDV的测量结果与之相比较。实验结果表明,LDV测速的相对精度不超过8‰,稳定性较好。     

决定介质折射率因素的经典计算

就介质折射率的物理意义首先从理论上作了说明,然后从经典概念出发对介质折射率的表达式作了推导,指出了决定介质折射率的因素,即组成介质的原子结构、原子种类、每一个原子周围电子分布的情况及辐射的频率。通过理论计算和实验数值的对比表明,所推导出的结论及相关的计算方式是正确的,对介质折射率的研究和在特殊领域对折射率有一定要求的材料的制备具有一定的指导意义。     

限制性集合矩阵的计数公式

In this paper, we consider the counting problem of matrix of set (Aij)k×n which satisfies k∪i=1 n∪j=1 Aij={a1,a2,…,am} and other conditions, and obtain some computational formulas which extend all the results in [1].     

Matone's Relation ofN =2 Super Yang-Mills and Spectrum of Toda Chain

InN=2 super Yang-Mills theory, the Matone's relation relates instanton corrections of the prepotential to instanton corrections of scalar field condensation <
Trφ²>. This relation has been proved to hold for Omega deformed theories too, using localization method. In this paper, we first give a case study supporting the relation, which does not rely on the localization technique. Especially, we show that the magnetic expansion also satisfies a relation of Matone's type. Then we discuss implication of the relation for the spectrum of periodic Toda chain, in the context of recently proposed Nekrasov-Shatashvili scheme.     

基于数字图像处理技术的树脂眼镜镜片缺陷检测研究

通过设计的镜片自动检测光学硬件系统,给出了树脂镜片精细杂质图像处理措施,将图像差分法应用于镜片图像边缘的去除;同时解决了镜片检测灰尘影响的问题;另外运用改进型的归一法解决杂质计数问题,为自动化分级分拣系统的研发提供重要的数据支持,为镜片缺陷检测系统的后续分级分拣的数字控制模块提供了可操作性。该检测系统检测精度为0.03 mm、速度为1片/s,检测误差控制在5%。     

掺铒光纤激光器自混合理论与微振动位移测量

利用线形掺铒光纤激光器搭建了一种新型光纤传感测量系统来测量微振动位移.采用条纹计数法分析自混合干涉信号,实验显示扬声器的振幅与驱动电压成很好的线性关系.该实验装置结构简单、成本低.实验结果表明,用该传感系统来进行振动位移测量,信号稳定,方法简单、迅速.     

A true random number generator based on the photon arrival time registered in a coincidence window between two single-photon counting modules

True random number generators are essential components for communications to be confidentially secured. In this paper a new method is proposed to generate random sequences of numbers based on the difference of the arrival times of photons detected in a coincidence window between two single-photon counting modules.     

Sulphur-Bridged BAl5S5+ with 17 Counting Electrons: A Regular Planar Pentacoordinate Boron System

At present, most of the reported planar pentacoordinate clusters are similar to the isoelectronic substitution of CAl₅⁺, with 18 counting electrons. Meanwhile, the regular planar pentacoordinate boron systems are rarely reported. Hereby, a sulphur-bridged BAl₅S₅⁺ system with a five-pointed star configuration and 17 counting electrons is identified at the global energy minimum through the particle-swarm optimization method, based on the previous recognition on bridged sulphur as the peripheral tactics to the stable planar tetracoordinate carbon and boron. Its outstanding stability has been demonstrated by thermodynamic analysis at 900 K, electronic properties and chemical bonding analysis. This study provides adequately theoretical basis and referable data for its experimental capture and testing.