Gravity at sea--A memoir of a marine geophysicist

A history of studies on the gravity measurements at sea in Japan is reviewed with an emphasis on the contribution of the author. The first successful measurements at sea were made in 1923 by Vening Meinesz in the Netherlands using the pendulum apparatus installed in a submarine. However, the gravity measurements using a submarine are not convenient because the access to a submarine is limited. Professor Chuji Tsuboi made a number of unsuccessful attempts at developing a gravity meter that can be operated on a normal surface ship by reducing the noise by minimizing the motion of the gravity meter through a mechanical design. I have chosen a new approach toward the measurements of gravity on a surface ship by simplifying the mechanical part using a string gravity meter that was installed directly on a vertical gyroscope in combination with the numerical and/or electronic reduction of noises. With this gravity meter TSSG (Tokyo Surface Ship Gravity Meter), we firstly succeeded in measuring gravity at sea onboard a surface ship in July 1961 and the measurements have been extended to the northwestern Pacific and beyond. The results reveal the fine structures of gravity field in and around trenches that provide important clues as to a number of geodynamic issues including the nature of the trench-trench interaction and the interaction of trenches with seamounts.     

摆线性质的物理分析方法

通过一道高考物理试题引出对摆线性质的讨论,以物理学中的纯滚动为模型从物理学的角度导出了摆线的性质.     

对称分布的相位型互补衍射屏的夫琅禾费衍射

为了验证巴比涅原理在相位型互补衍射屏的应用,建立了相位型互补衍射屏的数学模型,由理论分析得出了二者复振幅透过率的表达式,与用傅里叶光学方法得出其在频谱面上光强分布的表达式相同.由计算机模拟得到抛物柱面相位型互补衍射屏的夫琅禾费衍射光强的分布规律,与理论分析一致,得出分布规律为偶函数的相位型互补衍射屏的衍射符合巴比涅原理.     

辐照用紧凑连续波电子加速器的物理设计

为适应工业电子加速器需求增多的现状,提出了一种新型的结构紧凑的连续波电子加速器,运行频率为180MHz。依靠置于加速腔外的多个偏转磁铁,使电子束多次穿越加速腔,从而得到持续的加速。设计过程中,用CST软件对谐振加速腔进行了优化,用Parmela软件模拟了束流的粒子动力学。粒子纵向稳定度和横向聚焦也通过模拟进行了分析和验证。结果显示:此种新型加速器能得到9MeV,100kW的稳定电子束流。     

非常偏振光在单轴晶体表面的全反射分析

利用透射波函数和由菲涅尔公式求解反射相位差并对其求导的方法,分析了非常偏振光在单轴晶体表面发生的全反射现象,求解出晶体光轴在入射面内时,非常偏振光从各向同性介质入射到晶体和从晶体出射到各向同性介质两种情况的隐失波穿透深度和Goos-Hnchen位移的一般表达式。通过计算机模拟给出了单轴晶体为方解石和水晶情况时的穿透深度和Goos-Hnchen位移图像。结果表明,对于不同的晶体,光轴的取向对穿透深度和Goos-Hnchen位移的影响是明显不同的,若选取合适的晶体、光轴取向和入射角,可以得到较大的隐失波穿透深度和Goos-Hnchen位移。     

依赖于强度耦合的多光子相互作用过程的纠缠交换

利用全量子理论,建立了由多个"原子-腔场相互作用"构成的联合物理模型,研究了依赖于强度耦合的多光子相互作用过程,结果表明:如果适当控制原子穿越腔场的速度,就可实现量子纠缠信息在原子与腔场之间的交换传递,而且在某些条件下,信息能够完全转换,另外,利用计算纠缠度的方法所得结果与其完全一致。     

基于MATLAB下对单摆实验中大摆角问题的讨论

借助MATLAB计算软件,研究无阻尼状态下单摆的大摆角运动,给出了任意摆角下单摆运动周期的精确解。同时利用MATLAB函数库中的ode45函数,求解出大摆角下的单摆的运动方程及其运动规律,为单摆实验中大摆角问题的讲解提供了较好的教学辅助手段。     

适应创新教育的“3＋1”大学物理实验教学模式的探索与实践

分析了我校大学物理实验教学现状和民族院校学生特点,提出了针对不同层次、不同专业学生的＂3＋1＂大学物理实验教学模式,在实验教学中注重创新教育,培养学生科学实践能力和科技创新精神。     

Fundamental times,lengths and physical constants: Some unknown contributions by Ettore Majorana

We review the introduction in physics of the concepts of an elementary space length and of a fundamental time scale, analyzing some related unknown contributions by Ettore Majorana. In particular, we discuss the quasi‐Coulombian scattering in presence of a finite length scale, as well as the introduction of an intrinsic (universal) time delay in the expressions for the retarded electromagnetic potentials. Finally, we also review a special model considered by Majorana in order to deduce the value of the elementary charge, in such a way anticipating key ideas later introduced in quantum electrodynamics.     

Applying time domain physical optics to acoustic wave backscattering problem

The interest in transient analysis of acoustic waves has been growing in recent years, due to the advance of wide-band sonars. In this paper, a transient analysis method for acoustic backscattering signals is proposed based on the time domain physical optics (TDPO). TDPO is formulated via a theoretical inverse Fourier transform of the conventional physical optics formula used in the frequency domain wave scattering analyses. A hidden surface removal algorithm using an adaptive triangular beam method and a virtual surface concept are adopted to explain shadow effects and multiple reflections among elements, respectively. Numerical analyses are carried out for two kinds of underwater targets: a submarine pressure hull and an idealized submarine, in order to validate the proposed method. The result of the submarine pressure hull shows good agreements between the proposed method and conventional physical optics based on inverse fast Fourier transform. Additionally, the result of the idealized submarine shows that the proposed method is efficient for finding highlights including their contribution to the whole backscattering signal.