In fusion arc welding the final weld shape is influenced by welding parameters, mode of metal transfer, number of welding wires used and their arrangement in the contact tube, type of material to be welded, type of shielding medium and similar. In some articles, descriptions of investigations on the influence of the kind of material and the type of shielding medium used on the weld shape and si...

A detection system suitable for the contmuous and simultaneous measurement of gas-phase chlonne and hydrogen chlonde m the low parts per b&on (10’) by volume (ppbv) range 1s described Both gases are trapped through the walls of a microporous polypropylene tube mto an appropriate flowmg recipient buffer. The buffer then flows through two electrochenncal detectors placed m series downstream from ...

We report the synthesis of aligned arrays of millimeter long carbon nanotubes (CNTs), from benzene and ferrocene as the molecular precursor and catalyst respectively, by a one-step chemical vapor deposition technique. The length of the grown CNTs depends on the reaction temperature and increases from ~85 µm to ~1.4 mm when the synthesis temperature is raised from 650 to 1100 °C, while the tube ...

An experimental investigation for helical triple concentric tube heat exchanger has been carried out with different flow arrangements i.e. N-H-C (normal fluid inside hot at middle cold in outer annulus) and C-H-N (cold fluid in inner pipe hot in middle normal fluid in outer annulus) with parallel and counter flow types. The temperature distribution of fluids w.r.t. length of the heat exchanger ...

The microscopic electric polarization in terms of the dipole-dipole polarizability and its second hyperpolarizability of aligned films and ropes of carbon nanotubes has been studied theoretically by a point-dipole interaction model. The results show clearly the influence of intertube interactions on the microscopic polarization demonstrating the sensitivity of the electronic structure of carbon...

We propose, based on recent experimental results, a polyyne ring nucleus (PRN) growth model for the synthesis of single-layer nanotubes (SLN’s). The PRN model assumes that (i) the critical nuclei are the planar carbon polyyne rings that are observed to be most stable for sizes in the range C 10 to C40; (ii) ComC n clusters (possibly charged) play the role of a catalyst by serving to add C 2 or ...

A novel atomic emission spectrometry comprising laser ablation as a sampling source and hollow cathode plasma for the excitation of ablated sample atoms is proposed. In this arrangement, a conventional Grimm-type discharge lamp is employed, but the polarity of the power supply is reversed so that the cylindrical hollow tube acts as a cathode and the glow discharge plasma is produced within this...

A two-stage pulse tube refrigerator (PTR) is the simplest version of a multistage pulse tube refrigerator. A two-stage Gifford-McMahon (GM) has been used for nearly all of the cryopumps. The phasor analysis of the Gifford-McMahan (GM)-type pulse tube refrrigerator (PTR) have not explained detail in the earlier study. In the present work, a detailed mass flow, enthalpy & phasor analysis for a tw...

Three-dimensional CFD simulations are carried out to investigate heat transfer and fluid flow characteristics of a four-row plain fin-and-tube heat exchanger using the Commercial Computational Fluid Dynamics Code ANSYS CFX 12.0. Heat transfer and pressure drop characteristics of the heat exchanger are investigated for Reynolds numbers ranging from 400 to 2000. Fluid flow and heat transfer are s...