PWR蒸汽发生器水滴重力分离研究

用分离流动模型模拟了重力分离空间内的汽水两相流动，对重力分离空间内水滴的运动和分离效率进行了数值计算，讨论了重力分离高度和蒸汽上升速度对重力分离效率的影响以及各种尺寸水滴的跟随性     

变质量任意阶非完整系统的相对论性广义Appell型方程

本文构造了一个新型的相对论性动力学函数——广义加速度能 S~■,建立变质量系统的相对论性万有 D'Alembert 原理,由此导出任意阶非完整约束系统多种形式的相对论性广义 Appell 型方程.     

一种自由落体重力加速度测量仪的研制

本介绍一种自由落体重力加速度测量仪。利用自由落体运动规律，可得到当地的重力加速度。仪器具有结构简单、测量方便、结果准确等特点。     

The shape of a planet in hydrostatic equilibrium. An application to the Earth

Summary A new technique for computing gravitational equilibrium surfaces (considering gravitational and rotational potential) as a function of depth is presented here for a hydrostatic planet,i.e. a planet where rigidity is neglected. This work was formerly approached by Clairaut, and more recently by Lanzano; in this paper a new technique is developed that solves the problem without making use of the Clairaut differential equation. It is possible to define the gravitational potential of a planet by dividing it intoN shells, each of constant density, with a greater accuracy than in previous works; we can compute the equilibrium surface of each shell with an iterative technique,i.e. by modifying the solution by little steps until the desired accuracy is obtained. In the case of the Earth the geoid is found to be flatter than this ideal surface (this had already been observed also by means of completely different methods, for example by investigating the precession of the Earth). A possible reason for such a discrepancy is that it is too great an approximation to consider the Earth's density as being a function only of the depth.

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Riassunto Si presenta in questo lavoro una tecnica di calcolo per le superfici di equilibrio gravitazionale (considerando sia il potenziale gravitazionale che quello di rotazione) alle varie profondità per un pianeta considerato fluido, cioè privo di rigidità. Il calcolo è stato già affrontato in passato da Clairaut e poi piú recentemente da Lanzano, ma in questo lavoro si sviluppa una tecnica nuova che non risolve numericamente l'equazione differenziale di Clairaut. Si definisce il potenziale gravitazionale di un pianeta pensato con un numeroN di gusci ognuno di densità costante, con una migliore precisione che nei lavori precedenti; si esegue il calcolo delle superfici di equilibrio con una tecnica iterativa, cioè che corregge la soluzione a piccoli passi fino alla precisione desiderata. Il risultato per il caso della Terra mostra che il geoide è piú schiacciato di questa superficie ideale (questo fatto era già stato osservato anche con metodi completamente diversi, ad esempio osservando la precessione della Terra). Una possobile spiegazione per tale discrepanza è che è troppo approssimativo considerare la densità della Terra dipendente solo dalla profondità.

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Резюме Предлагается новая техника дла рачета поверхности гравитационного равновесия (рассматривая гравитационный и ротационный потениалы) в зависимости от глубины для гидростатической планеты, те. пренебрегая упругостьй планеты. Аналогичная задача рассматривалась Клэро и недавно Ландзано, но в этой статье развивается новая техника, которая позволяет решить проблему без использования дифференциального уравнения Клэро. Гравитационный потенциал планеты определяется с большей точностью, чем в предыдущих работах, разбивая планету наN оболочек с постоянными плотностями. Затем мы можем вычислить равновесную поверхность каждой оболочки, используя метод итераций. В случае Земли получается, что геоид представляет более сплющенную форму, чем идеальная поверхность (этот результат отмечался ранее с помощью других методов, например, при исследовании прецессии Земли). Возможное объяснение этого различия, повидимому, связано с тем, что плотность Земли приближенно рассматривается как функция только глубины.

     

电子在紧聚焦激光束中加速的最佳入射

通过数值模拟研究了电子在真空紧聚焦激光束中的动力学行为和能量增益。研究发现对应于两种不同的轨迹，电子可以得到纵向和横向两种电场的加速。阐明了电子的能量增益与电子的入射角和入射动量间的关系。对于给定的激光参数，给出了电子的最佳入射参数。     

A general numerical method for the solution of gravity wave problems. Part 1: 2D steep gravity waves in shallow water

In this paper, 2D steep gravity waves in shallow water are used to introduce and examine a new kind of numerical method for the solution of non-linear problems called the finite process method (FPM). On the basis of the velocity potential function and the FPM, a numerical method for 2D non-linear gravity waves in shallow water is described which can be applied to solve 3D problems, e.g. the wave resistance of a ship moving in deep or shallow water. The convergence is examined and a comparison with the results of other authors is made. The FPM can successfully avoid the use of iterative methods and therefore can overcome the disadvantages and limitations of such methods. In contrast to iterative methods, the FPM is insensitive to the selection of the initial solution and the number of unknowns. The basic idea of the FPM can be used to solve other non-linear problems. Its disadvantage is that much more CPU time is needed to obtain a sufficiently accurate result.     

Satellite infrared imagery, rawinsonde data, and gravity wave remote sensing of severe convective storms

GOES digital infrared data during the time period between two hours before the touchdown of tornado and the tornado touchdown time were used in this study. Comparison between tornado-associated clouds and non-tornado-associated clouds indicates that the difference between overshooting cloud top temperature and the tropopause temperature, or how much the cloud has penetrated above the tropopause, rather than either the absolute temperature of penetrative cloud top or the height of the top of overshooting turret is significant for the possible formation of severe storms. The penetrative overshooting cloud top collapses about 15 to 30 minutes before the touchdown of tornado. Gravity waves were detected from the severe convective storms.     

Geons and (4+1) Gravity

Gravitational-electromagnetic entities geons are singularity-free solutions of the Einstein-Maxwell equations. These structures in cylindrical symmetry are considered here through the noncompactified Kaluza-Klein theory which describes geometrically the gravitation field and its sources.     

Review: Hamiltonian Linearization of the Rest-Frame Instant Form of Tetrad Gravity in a Completely Fixed 3-Orthogonal Gauge: A Radiation Gauge for Background-Independent Gravitational Waves in a Post-Minkowskian Einstein Spacetime

In the framework of the rest-frame instant form of tetrad gravity, where the Hamiltonian is the weak ADM energy , we define a special completely fixed 3-orthogonal Hamiltonian gauge, corresponding to a choice of non-harmonic 4-coordinates, in which the independent degrees of freedom of the gravitational field are described by two pairs of canonically conjugate Dirac observables (DO) . We define a Hamiltonian linearization of the theory, i.e. gravitational waves, without introducing any background 4-metric, by retaining only the linear terms in the DO's in the super-hamiltonian constraint (the Lichnerowicz equation for the conformal factor of the 3-metric) and the quadratic terms in the DO's in . We solve all the constraints of the linearized theory: this amounts to work in a well defined post-Minkowskian Christodoulou-Klainermann space-time. The Hamilton equations imply the wave equation for the DO's , which replace the two polarizations of the TT harmonic gauge, and that linearized Einstein's equations are satisfied. Finally we study the geodesic equation, both for time-like and null geodesics, and the geodesic deviation equation.     

Induced Gravity Theory from Noether Symmetry

We discuss the functional form of the potential and the non-minimal coupling in the scalar tensor gravity (induced gravity) theories as allowed by the Noether symmetry in the spatially homogenous and isotropic spacetime background. The solution of the field equations (for k=0) are presented by using the results obtained from the Noether symmetry. It has been observed that the potential and the coupling function obtained from the Noether symmetric approach do not satisfy the continuity equation for k=± 1. Finally we present an inflationary solution that goes over to the Einstein's gravity asymptotically as t .