Simplified dispersion curves for circular cylindrical shells using shallow shell theory.

An alternative derivation of the dispersion relation for the transverse vibration of a circular cylindrical shell is presented. The use of the shallow shell theory model leads to a simpler derivation of the same result. Further, the applicability of the dispersion relation is extended to the axisymmetric mode and the high frequency beam mode.

Mechanical properties of a hollow-cylindrical-joint honeycomb

In this paper, we constructed a new honeycomb by replacing the three-edge joint of the conventional regular hexagonal honeycomb with a hollow-cylindrical joint, and developed a corresponding theory to study its mechanical properties, i.e., Young's modulus, Poisson's ratio, fracture strength and stress intensity factor. Interestingly, with respect to the conventional regular hexagonal honeycomb, its Young's modulus and fracture strength are improved by 76% and 303%, respectively; whereas, for its stress intensity factor, two possibilities exist for the maximal improvements which are dependent of its relative density, and the two improvements are 366% for low-density case and 195% for high-density case, respectively. Moreover, a minimal Poisson's ratio exists. The present structure and theory could be used to design new honeycomb materials.

Use of narrow-pore filters in He II transfer devices - new results

With the aim of finding simple methods for the fabrication of He II refilling devices, He II flow has been studied through filters made from various fine powders (oxides and metals, grain sizes in the range 0.05–2 μm) by compacting them under pressure. The results obtained for the different states of He II flow, especially in the “breakthrough” and “easy flow” range, are explained by the fountain effect, He II hydrodynamics and the choking effect. According to the results, pressedpowder filters can be classified into three groups with different flow characteristics, of which the “good transfer filters” with a behaviour neatly described by simple theory are suitable for use in He II refilling devices.

Two-dimensional solidification in a cylindrical mold with imperfect mold contact

A two-dimensional axisymmetric problem of solidification of a superheated liquid in a long cylindrical mold has been studied in this paper by employing a new embedding technique. The mold and the melt has an imperfect contact and the heat transfer coefficient has been taken as a function of space and time. Short-time exact analytical solutions for the moving boundary and temperature distributions in the liquid, solid and mold have been obtained. The numerical results indicate that with the present solution, for some parameter values, substantial solidified thickness can be obtained. The method of solution is simple and straightforward, and consists of assuming fictitious initial temperatures for some suitable fictitious extensions of the actual regions. Sufficient conditions for the commencement of the solidification have been discussed.

The sputtering temperature of a cooling cylindrical rod with an insulated core

By a standard application of Jones's method associated with the Wiener-Hopf technique an explicit solution is obtained for the temperature distribution inside a cylindrical rod with an insulated inner core when the rod is allowed to enter into a fluid of large extent with a uniform speed, and a simple integral expression is derived for the value of the sputtering temperature of the rod at the points of entry. Numerical results under certain special circumstances are also obtained and presented in the form of a table.

Breakdown voltage and V-Z characteristics of sodium vapour using coaxial cylindrical electrodes

Experimental results for breakdown voltage of sodium vapour measured for the first time using coaxial cylindrical electrodes of fixed gap distance (5 mm) and pressure (corrected to2 0 "C) in the range2 1 to 652 Pa are reported, and are founfdo l ltoow Paschen's Law. The investigations also reveal that V th-Ie characteristics are pressure dependent; the current during the breakdown and the buoifl dc-uurpre nt after a breakdoiws nei ther positive or negative. in spite of the central cylinder being always maintained at a positive potential

The sputtering temperature of a cooling cylindrical rod with an insulated core

By a standard application of Jones's method associated with the Wiener-Hopf technique an explicit solution is obtained for the temperature distribution inside a cylindrical rod with an insulated inner core when the rod is allowed to enter into a fluid of large extent with a uniform speed, and a simple integral expression is derived for the value of the sputtering temperature of the rod at the points of entry. Numerical results under certain special circumstances are also obtained and presented in the form of a table.

On an analytical-numerical procedure for the analysis of cylindrical shells with arbitrarily oriented cracks

An analytical-numerical procedure for obtaining stress intensity factor solutions for an arbitrarily oriented crack in a long, thin circular cylindrical shell is presented. The method of analysis involves obtaining a series solution to the governing shell equation in terms of Mathieu and modified Mathieu functions by the method of separation of variables and satisfying the crack surface boundary conditions numerically using collocation. The solution is then transformed from elliptic coordinates to polar coordinates with crack tip as the origin through a Taylor series expansion and membrane and bending stress intensity factors are computed. Numerical results are presented and discussed for the pressure loading case.

Alfven surface waves along cylindrical plasma columns

The properties of Alfven surface waves along a cylindrical plasma column surrounded by vacuum or by another plasma medium are discussed. Both symmetric (m=0) and asymmetric (m=+or-1) modes are found to be dispersive in nature. The interfacial symmetric modes propagate in a certain frequency window ( omega A1, omega As), where omega As is the Alfven surface wave frequency along the interface of two semi-infinite media; when nu A1> nu A2 these modes propagate as backward waves and when nu A1< nu A2 as forward waves. The asymmetric modes change from backward to forward waves at a critical wave number kTr approximately=1.59/a when nu A1< nu A2 or vice versa when nu A1> nu A2.

Characteristics of Alfven surface waves along moving cylindrical plasma columns

The dispersive and stability characteristics of Alfven surface waves (ASW) along the boundary of the moving cylindrical plasma column, surrounded by a stationary medium embedded in a parallel magnetic field is studied. The nature of the symmetric and asymmetric modes on the interface parameters is also discussed.

Alfven surface waves along a cylindrical plasma column surrounded by neutral gas

The dispersion characteristics of Alfven surface waves along a cylindrical plasma column insulated by a neutral gas are discussed. There is no qualitative change in the characteristic curves below the critical magnetic field, given by vA approximately=s, as compared to the propagation of surface waves along the plasma-plasma interface. For magnetic fields above this critical value, there exists a cut-off wave number kc, which depends upon the azimuthal wave number, the radius of the cylinder, the strength of the magnetic field above the critical value and the gas pressure, such that surface waves do not exist for kcylindrical plasma column.

Transversely isotropic infinite cylindrical shell subjected to a radial axisymmetric line load

The problem of an infinite transversely isotropic circular cylindrical shell subjected to an axisymmetric radial external line load is investigated using elasticity theory, classical shell theory and shear deformation theory. The results obtained by these methods are compared for two ratios of inner to outer shell radius and for varying degrees of anisotropy. Some typical results are given here to show the effect of anisotropy and the thickness of the shell on the distribution of stresses and displacements.

Elasticity solution for a long circular sandwich cylindrical shell subjected to axisymmetric load

An elasticity solution has been obtained for a long circular sandwich cylindrical shell subjected to axisymmetric radial ring load using Love's stress function approach. Numerical results are presented for different ratios of modulus of elasticity of the layers. The results obtained from this analysis have been compared with those obtained from sandwich shell theory due to Fulton.

Incidence factors of the tracking systems used in parabolic-cylindrical concentrators

Several orientation and tracking systems employed in parabolic-cylindrical concentrators for focusing the direct solar radiation on the absorber tubes are analyzed from the technical and economic points of view. Case one, where the incidence factor was a function of declination and hour angle, showed that the maximum variations of incident factor from morning to noon was 0.5 at zero angle of declination. Case two, where the incidence factor was a function of declination, hour angle and latitude, showed the maximum variation of the incidence factor to be 0.128, which occurred during noon at the latitude of 30 degrees, corresponding to a change of declination from 0 to 23.5 degrees. In case three, the incidence factor, a function of declination only, showed that the maximum variation of the incidence factor corresponding to the change in declination from 0 to 23.5 degree was 0.0758. It is concluded that system three is the most efficient from the technical and economic point of view.