The electrodynamical properties of a volume resonator formed by a perodic structure built from the metallic threads inside a rectangular waveguide (”grid” volume resonator) is considered for travelling wave tube and backward wave oscillator operation. Peculiarities of passing of electromagnetic waves with different polarizations through such volume resonator are discussed.

A fullerene is any molecule composed entirely of carbon, in the form of a hollow sphere, ellipsoid, or tube. Spherical fullerenes are also called buckyballs, and they resemble the balls used in Association Football. Cylindrical ones are called carbon nanotubes or buckytubes. Fullerenes are similar in structure to graphite, which is composed of stacked graphene sheets of linked hexagonal rings; ...

In 1824, The London Times reported: “A wonderful instrument called the Stethoscope .. . is now in complete vogue at Paris. It is merely a hollow wooden tube, about a foot in length . .. One end is applied to the breast of the patient. The other to the ear of the physician, and according to the different sounds, harsh, hollow, soft, loud etc., he judges of the state of the disease.” It had been ...

The microsporidia are ubiquitous, obligate intracellular eukaryotic spore-forming parasites infecting a wide range of invertebrates and vertebrates, including humans. The defining structure of microsporidia is the polar tube, which forms a hollow tube through which the sporoplasm is transferred to the host cell. Research on the molecular and cellular biology of the polar tube has resulted in th...

Abstract: In this paper we extend the theory of Radio Frequency (RF) propagation as it relates to propagation within metal circular pipes. This work is motivated by a need to understand the operation of UHF Radio Frequency IDentification (RFID) systems when the tags are placed within the pipes. These circular pipes are shown to be similar to metal tube waveguides which are hollow. We derive the...

We study theoretically the propagation of elastic waves in two-dimensional composite media composed of a square array of hollow steel cylinders embedded in water using the finite-difference time-domain method. These composite media constitute a class of acoustic band gap materials with narrow pass bands in their transmission stop bands. The frequency at which the pass band occurs is tunable by ...

An innovative beam concept made from hollow FRP tube with external flanges and filled crumbed rubber concrete was investigated respect to bending shear. The performance of the rubberised-concrete-filled specimens then compared normal-concrete-filled tubes. A comparison between flanged non-flanged concrete-filled tubes also implemented. Moreover, finite element simulation conducted predict funda...

Regular boundary element method is employed for the variational formulation of Helmholtz equation that governs the waveguiding problems. Like in the Charge simulation method, in this method, the source points associated with the fundamental solutions are allocated outside the domain so that the singular integrals which occur in the standard boundary element procedure can be avoided. First, the ...

Our Moon is a potential indicator of a possible alien presence near the Earth at some time during the past 4 billion years. To ascertain the presence of alien artifacts, a survey for ruinlike formations on the Moon has been carried out as a precursor to lunar archaeology. Computer algorithms for semi-automatic, archaeological photo-reconnaissance are discussed. About 80,000 Clementine lunar orb...