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A simple testing procedure has been developed in order to investigate and screen the current interruption capability of vacuum interrupter contact materials. A synthetic circuit delivering adjustable AC currents, followed by a pulsed of 21 kV peak for 2 seconds has been used. The electrical tests has been developed to reproduce the conditions close to a fault current rated at 12 kV; only the recovery...
The microstructure and properties of the contact CuCr alloy produced by electron-beam cladding have been investigated. The effect of the electron beam cladding parameters and preheating temperature of the base metal on the structure and the properties of the coatings has been determined. The bimodal structure of the cladding coating has been established. The short circuit currents tests are made on...
The copper chromium composite coatings produced by the electron beam cladding in the vacuum on the cooper substrate and electrical contacts CuCr25 produced by solid-phase sintering in a hydrogen atmosphere have been investigated. The copper chromium composite coatings produced by the electron beam cladding showed higher values of breaking capacity compared with the sintered contact material.
A self-consistent space-resolved numerical model of cathode spots in vacuum arcs is developed on the basis of the COMSOL Multiphysics software. The model is applied to cathode spots on copper-chromium (CuCr) contacts of vacuum interrupters. In the limiting case of large grains, the main effect of change in cathode material from Cu to Cr is the reduction of thermal conductivity of the cathode material,...
Copper-Chromium (CuCr) based contact material is widely used for vacuum interrupter (VI) contacts and has found worldwide acceptance in medium-voltage VIs, especially for high-current interruption. Contact material with chromium content between 25 and 50 wt. % is almost exclusively used. Conventionally, copper and chromium are uniformly distributed throughout the body of the contact. In a few cases,...
Copper-Chromium alloys are commonly used as contact materials for energy distribution. One of the major requirements is a good electrical conductivity for non-dissipative conduction of the nominal current. Since Cu and Cr are mutually nearly insoluble, CuCr alloys are two-phase composites, usually consisting of chromium particles embedded in a copper matrix. A decrease in electrical conductivity following...
The hexavalent chromium (Cr(VI)) removal by zero-valent iron (Fe0) was investigated under various groundwater geochemistry conditions though batch experiments. The results showed that the collective influences of humic acid, HCO3−, and Ca2+ on the reactivity of zero-valent iron for Cr(VI) removal were different from their individual impacts. The sole presence of humic acid did not show a significant...
In this work the Fe-Mn bimetal oxide was synthesized and was used for the removal of chromium. It was found that the effective pH for adsorption of chromium was in the range of 5.0 to 7.0, and the removal percentage of chromium reached maximum at pH 6.0. The kinetic study showed that the adsorption of chromium was well described by pseudo-second-order model. The removal efficiency of chromium increased...
We present a rigorous formulation based on the Poynting's theorem in dispersive and lossy media to calculate the quality factor, material loss, radiation loss, and radiation pattern of an optical nanobowtie antenna using the finite-difference time-domain method. The quality factor obtained from our theory, 8.73, agrees well with the experimental data. Our results show that the radiation loss and material...
Throughout the globe lot of research works are going on in order to improve the surface wear resistance of the different industrial materials. For that reason the surface coating techniques become popular. The detonation gun (d-gun) spraying is one of the most advanced thermal spray variants for depositing high quality wear resistant coatings. Of all the ceramic materials that can be D-gun sprayed,...
Synlhesis of nanocomposites in Cu-TiB2, Cu-Ni-TiB2, Cr-Ni- TiB2 systems was developed using a combination of high-energy planetary ball milling and self-propagating high-temperature synthesis (SHS). Consolidation behavior of nanocomposite powders, microstructures and mechanical properties of the bulk materials and coatings were investigated in view of developing new materials with high temperature...
Extremely fast rate of rise voltage and current pulses (rate of rise in range of few tens of nanoseconds) are of great importance in recent years. They have applications in electrostatic Discharges (ESD) and Electromagnetic interference. Also, in medical sciences, fast rate of rise voltages with rise time in range of few nanoseconds are used for study of electroporation effects in biological cells...
Heavy metals accumulate in organisms as a result of direct uptake from the surroundings across the body wall, from respiration and from food. Uptake via food is most important in terrestrial organisms and it may also be important in the aquatic environment. Dietary uptake can include heavy metals adsorbed on particulates present on the surface of leaves etc, which have not been absorbed by the plant...
In this study, a new approach is introduced for automatically detecting of visual foreign materials like peduncles, leaves and blight products in mass of Barberries. The segmentation algorithm has been developed for red-free images of barberries. Cr plane of YCbCr color space is used to detect the target area of images. Because of shining of barberry's glossy cortex during imaging, there are many...
The Vacuum interrupter is the arc extinction chamber of the vacuum circuit breaker which is widely used in the medium voltage networks for interruption of short -circuit current. In the field of vacuum switching devices, the contact material is the most important parameter determining the switching behavior. During arcing, the contacts are eroded and hence there is a change in the surface microstructure...
Oral reading fluency is essential to overall reading achievements and repeat reading has been found to be an effective strategy for oral reading fluency. Choral reading is the most authentic use of repeated readings in the EFL primary grades. However, teachers have neither sufficient time nor adequate expertise to deal with non-fluent readers. Hence, challenges with oral reading fluency and motivation...
A new adsorbent was developed from municipal sewage sludge (SS) combined with 5-20% pyrolusite of the weight of SS carbon, and using ZnCl2 as chemical activation reagent. Characterized by N2-BET methods and SEM, the result showed that the surface area of the new adsorbent was increased to 354.198 m2/g compared with that of the unmi- xed sludge activated carbon 232.526 m2/g and total pore and micropore...
In this study, research has been conducted on the formation processes and causes of problems that have arisen over the long term from materials used in knee or hip arthroplasty patients. A rare case has been viewed for a patient who had arthroplasty ten years previously. During a second knee joint revision surgery after implant failure, a biopsy of bone and soft tissue taken from around the implant...
Spinel LiMn1.8Co0.2O4 and LiMn1.2Co0.2Cr0.6O4 compounds were prepared through sol-gel method using citric acid as a chelating agent. The structural and electrochemical properties of cathode compounds were investigated by mean of X-ray diffraction, cyclic voltammetry, galvanostatic charge-discharge test and AC impedance spectra systematically. It is found that the high rate discharge capability of...
This paper presents mining the worst thermal fatigue life of solder joints on chip components used in vehicle electronics. The authors proposed an isothermal fatigue test method using real size solder joints to get the fatigue properties. The Manson-Coffin's law given by this method could improve the agreement between the simulation model and experimental results. Based upon the Manson-Coffin's law...
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