The variation of the breakdown voltage of a low frequency electrical pulsed discharge due to an external electrode is reported. The discharge tube consists of a thin glass tube having two internal hollow electrodes. A thin copper foil wrapped around the glass tube forms the external electrode. The internal electrodes of the discharge tube are supplied by a flyback converter. Its operating point...

Hollow section members are popular elements in steel constructions, especially when they mainly loaded by normal forces, like simply supported columns or truss members. The individual hollow can be combined bolted endplate connections. If the bolts arranged at all four sides of rectangular section, design rules for T-stub model from widely used Eurocode EN 1993–1-8 cannot applied due to missing...

With the exception of the 632.8 nm neon line all the important visible and ultraviolet cw gas laser lines belong to the spectra of ionized atoms. To achieve proper laser oscillation the excitation of the upper levels of these lines is of primary importance. High energy electrons are needed for this process. As such electrons are in high concentration in the hollow cathode discharge, it was obvi...

We introduce a new variety of flexatube, a rhomboflexatube. It is obtained from a cardboard rhombohedron by removing a pair of opposite faces (rhombi), and then subdividing the remaining four faces by pairs of diagonals. It is reversible, that is, it can be turned inside out by a series of folds, using edges and diagonals of the rhombi. To turn a rhomboflexatube inside out is quite a challengin...

The heat transfer characteristics of a downhole heat exchanger (DHE) were studied experimentally in a laboratory scale. The permeable aquifer was simulated by using a rectangular tank filled with glass beads of diameter ranging from 3 to 5 mm. The downhole heat exchanger was modeled by a Ushaped copper tube. We have simulated various configurations of DHE by changing the geometrical parameters ...

The Welding in cold formed areas is not only an open question for statically loaded sections (brittle fracture) but also for dynamically loaded structures (fatigue resistance). A lot of structures are subjected to dynamic loadings and unfortunately very little information about the influence of welding in the cold formed areas on fatigue resistance is available. In order to establish the fatigu...

Transformation of the tube-side mass transfer coefficient derived in hollow fibre membrane contactors (HFMC) of different characteristic length scales (equivalent diameter and fibre length) has been studied when operated in the low Graetz range (Gz<10). Within the low Gz range, mass transfer is generally described by the Graetz problem (Sh=3.67) which assumes that the concentration profile comp...

In this work, we propose analytical formulas for the estimation of dispersion properties and effective area fundamental mode hollow-core inhibited coupling fibers with a microstructured cladding composed by ring dielectric tubes. The are based on model which has already been successfully applied to confinement loss. takes into account effects core modes in context single-tube approximation. Eff...

Pultrusion process is one of the most effective manufacturing techniques for production of composite materials having constant cross-sectional area. Pultruded composite profiles are getting increasingly popular in construction industry as well as in wind energy due to their high strength-toweight ratio, low maintenance cost and high corrosion resistance. Recently, pultruded profiles are foresee...

Conditioning of the insert inside a hollow cathode is believed to be important to ensure reliable discharge initiation and subsequent cathode operation. The desorption of contaminates is reported from hollow cathodes as a function of heater power to quantify cathode conditioning characteristics and identify factors that might prevent the fast initiation of a discharge. In addition to conditioni...