The Influence of a Coupling Film on Ultra-Low-Loss Dielectric Measurement Using an Open Resonator

A Fabry-Perot open resonator excited through a coupling film and loaded with a plane-parallel dielectric plate is analyzed. The eigen equation of the field in the resonator is obtained. The quality factors of the resonator with and without a coupling film are compared. The quality factors of the resonator loaded with a plate that is in resonance and off resonance are also compared. It is shown that the difference in coupling losses between a loaded resonator and an unloaded resonator may strongly affect the accuracy in measuring ultra-low loss dielectric material. Some ways to reduce the influence of coupling loss are discussed. Our experiment results are consistent with the numerical analysis.     

Extraction of vanadium and synthesis of vanadium pentaoxide from Bayer’s sludge

Wastes generated from the Bayer’s process serve as valuable resources for aluminum, vanadium, gallium, etc. This work aims to develop a environmentally acceptable and low-cost chemical leaching-cumpurification method for the recovery of vanadium sludge of Indian alumina plant (10–12% V₂O₅) and synthesize vanadium pentaoxide. The efficiency of leaching was evaluated by various lixiviants like acidified water, H₂SO₄, soda and NaOH against variation in pulp density and temperature. Maximum extraction (96%) vanadium was achieved using acidified water leaching at above ambient temperature in 1 h with 200 g/L pulp density following diffusion control model. Finally, the vanadium rich leach liquor was purified by steps of adsorption/precipitation etc., to remove with iron and silica to get vanadium pentaoxide. A high purity product of 99% V₂O₅ was obtained by allowing the adsorption at acidic pH followed by desorption and precipitation at 90°C.     

An Efficient Algorithm for Optimizing Base Station Site Selection to Cover a Convex Square Region in Cell Planning

It is gradually more significant to optimally select base stations in the design of cellular networks, as the customers stipulate cheaper and better wireless services. From a set of prospective site locations, a subset needs to be preferred which optimizes two critical objectives: service coverage and financial cost. Discovering the optimum base station locations for a cellular radio network is considered as a mathematical optimization problem. In the context of mobile communication, an efficient algorithm for the base-station placement problem is developed in this paper. The intention is to place a given number of base-stations in a given convex region and to assign range to each of them such that every point in the region is covered by at least one base-station and the maximum range assigned is curtailed. It is basically covering a region by a given number of equal radius circles where the objective is to minimize the radius. A computational method for finding good coverings of a square with equal circles is presented. An algorithm is designed that determines the optimal locations of base stations without performing an exhaustive search. The proposal will try to minimize the number of installed towers, makes tower’s location feasible, and provides full area coverage with an intention to reduce the overlapping.     

Laser-Surface Alloying of Nimonic 80 with Silicon and Aluminum and its Oxidation Behavior

In the current study, laser-surface alloying (LSA) of Nimonic 80 (a Ni-based superalloy) was conducted using a high-power continuous wave (CW) CO₂ laser by simultaneous feeding of predetermined proportion of elemental Si and Al powders with an Ar shroud. After LSA, the microstructure of the alloyed zone was carefully analyzed and found to consist of several intermetallic phases of Ni and Si. The microhardness of the alloyed zone was significantly increased to 500?VHN compared with 250?VHN of the as-received substrate. The high-temperature oxidation resistance of the laser-surface-alloyed specimens (under isothermal conditions) was improved (at temperature ranges between 1223?K and 1423?K [950?°C and 1150?°C]) compared with as-received Nimonic. Even though LSA enhanced resistance to oxidation up to a limited period, continued exposure to extended hours (at a given temperature) led to spallation of scale. It seems that a SiO₂-rich adherent scale is responsible for enhanced protection against oxidation in the laser-surface-alloyed specimens. However, the presence of Al₂O₃ in the oxide film enhances the resistance to spallation by increasing the scale adherence at a higher temperature. The results are supported by a suitable thermodynamic calculation.     

Investigation of adsorption of lead,mercury and nickel from aqueous solutions onto carbon aerogel

Recently a new form of activated carbon has appeared: carbon aerogel (CA). Its use for the removal of inorganic (and especially metal ions) has not been studied. In the present study, the adsorption of three metal ions, Hg(II), Pb(II) and Ni(II), onto carbon aerogel has been investigated. Batch experiments were carried out to assess adsorption equilibria and kinetic behaviour of heavy metal ions by varying parameters such as agitation time, metal ions' concentration, adsorbent dose and pH. They facilitated the computation of kinetic parameters and maximum metal ion adsorption capacities. Increasing the initial solution pH (2–10) and carbon concentration (50–500 mg per 50 cm³) increases the removal of all three metal ions. A decrease of equilibrium pH with an increase of metal ion concentration led us to propose an adsorption mechanism by ion exchange between metal cations and H⁺ at the carbon aerogel surface. Carboxylic groups are especially involved in this adsorption mechanism. Langmuir and Freundlich isotherm models were used to analyse the experimental data of carbon aerogel. The thermodynamics of the metal adsorption was also investigated for the practical implementation of the adsorbent. The sorption showed significant increase with increase of temperature. Kinetics models describing the adsorption of Hg(II), Pb(II) and Ni(II) ions onto carbon aerogel have been compared. Kinetics models evaluated include the pseudo‐first order and second order model. The parameters of the adsorption rate constants have been determined and the effectiveness of each model assessed. The result obtained showed that the pseudo‐second order kinetic model correlated well with the experimental data and better than the pseudo‐first order model examined in the study. Mass transfer coefficients obtained can be useful in designing wastewater treatment systems or in the development of environmental technologies. Copyright © 2005 Society of Chemical Industry     

Diode Laser Assisted Surface Nitriding of Ti-6Al-4V: Properties of the Nitrided Surface

In the present study, a detailed investigation of mechanical and electrochemical properties of laser-surface-nitrided Ti-6Al-4V has been carried out. Laser treatment is carried out by melting the surface of Ti-6Al-4V substrate using a high power CW diode laser with nitrogen as shrouding environment. The effect of laser parameters (applied power and gas flow rate) on the properties of the nitrided surface was evaluated. The microhardness of the nitrided surface was improved to a maximum of 1175 VHN in the present set of laser processing conditions as compared to 280 VHN of as-received substrate. Surface nitriding increased the potential for pit formation (E _pit) significantly as compared to as-received Ti-6Al-4V. Immersion in Hank’s solution showed calcium phosphate deposition from the solution. The optimum process parameters for laser surface nitriding were derived.     

Special Issue on the 2nd International Conference Devices for Integrated Circuits (DevIC-2017)

Microsystem Technologies -     

Special Issue on the 3rd International Conference Microelectronics,Circuits and Systems (Micro 2016)

Microsystem Technologies -