非齐次边界条件时的半无界弦自由振动问题

基于达朗贝尔公式,讨论了半无界弦自由振动时的非齐次边界条件的延拓问题.结果表明:对半无界弦自由振动时的非齐次边界条件的延拓,理论上可有多种方法,尽管延拓表达式不同,但不会影响最终结果.文中最后还给出了两种相对简单的延拓方法.     

用Laplace变换法求解端点系有集中质量的弹性杆的振动问题

用Laplace变换法求解了一端为齐次边界条件,另一端系有集中质量的弹性杆的纵振动问题,推广了相关文献的结果。     

弦振动定解问题级数解的截断误差分析

基于弦振动方程在定解条件下的三种不同形式的级数解,讨论了是否忽略自变量两种条件下级数解的截断误差.其中,在考虑自变量的情况下通过对普遍截断误差进行估计,定义出类吉布斯现象,从而得到最大截断误差的估计.     

矩形薄膜受迫横振动问题的求解及可视化

膜的横振动分析在乐器膜、耳膜以及植物细胞膜中有着广泛的应用价值.相比自由振动,受迫膜振动问题的研究更符合应用实际.本文采用数学物理定解问题的傅里叶级数法与冲量定理法,对四周固定的均匀矩形薄膜振动问题进行了研究,得到了此类问题在受迫振动下的解析解,并对其振动状态进行了可视化分析.研究发现：一维弦振动解法同样可为二维有界膜振动问题提供简便的求解途径,且膜振动将呈现更加丰富的特点.本文的二维非齐次振动问题的冲量定理解法还可推广到二维有源(汇)输运问题中去.     

端面受到空气阻力的弹性杆的振动

研究了一端固定、一端受到空气阻力的弹性杆的振动.建立了受阻力端的近似边界条件.本征振动模式含有阻尼振动特有的指数衰减因子,但不具有分离变量的形式.因为边界条件不属于斯特姆-刘维型,所以关于本征函数的完备性和正交性的一般定理不适用于本问题.用拉普拉斯变换法求解了任意给定初始条件下的振动.     

用数据归纳法研究一端含有杂质的一维单原子链的局域振动

通过数值计算和数据归纳方法研究一端含有杂质的一维单原子链的局域振动,探讨其产生局域振动的条件和频率,并对其他含有杂质情况进行简要的讨论.     

两体弹性相互作用的一种等效方法

对于一端固定的无质量弹簧的振动系统(图1),通过解振动系统的运动微分方程,可以得到其振动的周期为其中m为物体的质量 k为弹簧的弹性系数 如果弹簧的另一端为自由端,即连接在另一质量为有限的物体上(图2),则通过解系统的微分方程可知,这样一个系统可以等效成图1的形式,只是这时物体的质量为两物体的折合质量,即 这是一般教科书上介绍解这类问题时的一种普遍等效方法,这种等效方法对于了解m1与m2组成的整体系统的一些性质(如系统的振动周期,频率等)是有效的.但是,如果需要考察单个物体m1(或m2)的运动,这种等效方法就变得很不方便了. 本文介绍…     

介绍一篇分析弦振动的文章

《物理教育》(日本物理教育学会志)在1985—1989年间,曾发表许多篇日本长崎大学福山丰及其合作者撰写的关于气柱和弦的共振现象的论文。在此简要介绍其中的一篇文章。将弦的一端结在电动音叉上,另一端绕过滑轮挂上重物,在音叉驱动下使弦振动,这是一般的弦振动实验。该杂志第34卷(1986)第4期上题为《电磁     

弦振动实验中阻力系数的测定

研究一端接简谐振源、另一端固定的弦在阻尼介质(空气)中的稳态振动及阻力系数的测定.结果表明在考虑了媒质阻尼的情况下,波节处的振幅将不为零.在理论上避免了无穷大振幅的出现,在实验上可通过测量波腹和波节处的振幅计算阻力系数以及在阻尼介质中的驻波波腹点和波节点的位置相对于自由空间的纯驻波状态时的波腹点和波节点的位置的偏离量.     

振动弦的“色散”实验研究

研究了有界弦横向强迫振动时弦上波速的色散现象.实验测量结果表明:由弦的张力和线密度决定的弦上的波速(T/ρ)~1/2不一定是常量,在一定的条件下,弦的波速会随着弦驻波的波长长度(弦长)改变而变化.     

关于"太阳在银河系中所受引力与到银心距离r的关系"的讨论

讨论了银道面内的引力场强分布和太阳在银河系中所受引力与到银心距离r的关系，指出引力场强g并不是与r的平方成反比，这是由于银河系的大小和形状不能忽略造成的．强调了万有引力定律的适用条件．     

On the predictability of the positions of the convergence zones in the ocean

The disagreement between the experimental and calculated positions of the first convergence zone are known from many publications. The most probable cause for such a disagreement, namely, the incorrect specification of the input data for the calculations, is considered. The lack of simultaneity between the hydrological surveys of the region and the acoustic experiments is emphasized. The experimental data obtained by the author in five ocean regions are presented. These data characterize the diurnal variability of the distance from the source to the nearest boundary of the convergence zone. The relations proposed by different researchers for calculating the sound speed from the temperature, salinity, and hydrostatic pressure are analyzed. It is shown that these relations lead to a substantial difference in the estimated depth dependence of the hydrostatic gradient of the sound speed. The position of the first convergence zone is calculated for the propagation conditions determined by vertical temperature and salinity profiles with the subsequent recalculation of these profiles into sound speed profiles by using eight different formulas known from the literature. It is shown that different formulas lead to different values of the distance to the first zone; this difference is substantially greater than that between the calculations and experiment. The necessity of improving the recalculation relations in view of the experimental data on sound propagation in natural oceanic waveguides, including the data on the actual positions of the convergence zones, is emphasized.     

On the calculation of the bremsstrahlung in the region of the plasma frequency

On the basis of the classical theory of radiation produced in incomplete Coulomb interaction, a formula is derived for the coefficient of the bremsstrahlung of fully ionized plasma. In the region of rectilinear approximation a comparison is made with the results of the quantum formula derived from the Born approximation. Furthermore, the influence of dispersion upon the emission coefficient is taken into account; some relations for the region of dispersion are given.     

Dependence of the Intensity of the Spectral Lines and the Composition of the Sample and the Plasma Parameters of the Unipolar Arc

The investigation was made of the dependence of the intensity of Tl, Ga, Mo, Mg, Mn, Sn, Bi, Ni, Zn, Pt and Au spectral lines and the plasma parameters (temperature T, electron concentration n_e, degree of 6 ionnization α) from concentration of lithium additive.     

Extracting the wavefunction of the LSP at the LHC

We consider associated production of squarks and gluinos with the lightest supersymmetric particle (LSP), or states nearly degenerate in mass with it. Though sub-dominant to pair production of color SU(3)-charged superpartners, these processes are directly sensitive to the wavefunction composition of the lightest neutralinos. Exploiting event-shape variables - including some introduced here for the first time - we are able to identify the composition of the LSP by selecting events involving a single high-pT jet recoiling against missing transverse energy. We illustrate the proposed technique on a set of benchmark cases and propose methods for applying these results in more realistic experimental environments.     

Set the controls for the heart of the Sun

In this paper we describe experiments conducted with high-power lasers that are attempting to replicate, for a very short time and in miniature, conditions found in the Sun. Experiments to date have reached conditions in the outer part of the Sun. To reach the Sun's centre requires compression of material to very much greater than solid density and heating to over ten million degrees. To achieve this, a new class of experiments and a new generation of high-power lasers are required.     

On the Question of the Source of the Apokamp

Technical Physics - The object of this work is the apokamp—a new type of plasma jet, which is formed from a bright offshoot emerging at the bending point of a channel of a high-voltage...