Fabrication and characterization of a planar interleaved micro-transformer with magnetic core

This paper presents the design, the fabrication and the characterization of a planar interleaved micro-transformer with an Yttrium Iron Garnet (YIG) core. The design of this micro-transformer and the manufacturing steps are presented. HFSS software is used for the conception and the simulation of the interleaved magnetic micro-transformer. It is composed of two identical windings. A bottom magnetic core is used to improve the integrated transformer performances. To form the windings, we have used a surface micromachining process. We have also used a negative photoresist (SU-8) as an insulating layer and as support for the fabrication of a bridge to connect the central end of the coils to the ground shield. The micro-transformer have been characterized with impedance meter up to 100 MHz, and completed to 1 GHz using vector network analyzer.     

Selection of timed token protocol parameters to guarantee messagedeadlines

Networks that use the timed token protocol (such as the 100 Mbit/s FDDI network) are well suited for real-time applications because they guarantee, to each node, an average bandwidth and a bounded access time to the communication network. This guarantee is necessary but not sufficient for the timely delivery of deadline-constrained messages; protocol parameters must be carefully selected to ensure that these messages meet their deadlines. This paper addresses the issue of selecting the protocol parameters TTRT (target token rotation time) and the synchronous capacities assigned to each node. The objective is to guarantee that each synchronous message is transmitted before its deadline. An upper bound is derived on the worst case achievable utilization (WCAU) of any parameter selection scheme. The WCAU of a scheme is defined as the maximum utilization U such that the scheme guarantees all synchronous messages as long as their utilization is less than U. An algorithm for selecting the above parameters is proposed, The algorithm is shown to have a WCAU that is very close to the upper bound     

Concentration fields in the solidification processing of metal matrix composites

A numerical investigation of the solidification of a binary alloy (Al-1.0 wt.% Cu) around cylindrical fibers with different fiber layouts and thermophysical properties was undertaken to gain insight into the processing of fiber-reinforced metal matrix composites. The focus of this study was on solute transport and redistribution during the solidification process, and the resulting concentration fields in the solidified alloy matrix. Change of phase in the alloy was formulated using a modified version of the temperature-transforming method for the energy equation. A source term that accounts for the solute rejection at the interface was incorporated into the solute concentration equation to model solute redistribution at the interface. Detailed results were obtained from the numerical simulations of low-(alumina) and high-(copper) conductivity fibers in inline and staggered configurations. Effects of the fiber pitch (longitudinal spacing) and transverse spacing were investigated. Higher concentrations of solute were seen to accumulate around copper fibers than for alumina fibers. With an initial, uniform concentration of 1.0 wt.% Cu in the melt, the maximum-recorded solute concentration in the domain for alumina fibers was 1.26% while that for copper fibers was 3.11%. For inline fibers, increasing the fiber pitch beyond a critical value did not change the overall shape of the local solute distribution around the fibers: the critical pitch for alumina fibers was found to be roughly 2.5 fiber diameters while that for copper was 2 fiber diameters.     

A.c. conductivity and dielectric study of LiNiPO4 synthesized by solid-state method

LiNiPO₄ compound was prepared by the conventional solid-state reaction. The sample was characterized by X-ray powder diffraction, infrared, Raman analysis spectroscopy and electrical impedance spectroscopy. The compound crystallizes in the orthorhombic system, space group Pnma with a = 10·0252(7) Å, b = 5·8569(5) Å and c = 4·6758(4) Å. Vibrational analysis was used to identify the presence of \( \mathrm{PO}_4^{3- } \) – group in this compound. The complex impedance has been measured in the temperature and frequency ranges 654–716 K and 242 Hz–5 MHz, respectively. The Z′ and Z″ vs frequency plots are well-fitted to an equivalent circuit consisting of series of combination of grains and grain boundary elements. Dielectric data were analysed using complex electrical modulus M* for the sample at various temperatures. The modulus plots are characterized by the presence of two peaks thermally activated. The frequency dependence of the conductivity is interpreted in terms of equation: \( {\sigma_{\mathrm{a}.\mathrm{c}.}}\left( \omega \right)=\left[ {{{{{\sigma_{\mathrm{g}}}}} \left/ {{\left( {1+{\tau^2}{\omega^2}} \right)}} \right.}+\left( {{{{{\sigma_{\infty }}{\tau^2}{\omega^2}}} \left/ {{1+{\tau^2}{\omega^2}}} \right.}} \right)+A{\omega^{\mathrm{n}}}} \right] \) . The near values of activation energies obtained from the analysis of M″, conductivity data and equivalent circuit confirms that the transport is through ion hopping mechanism dominated by the motion of Li⁺ in the structure of the investigated material.     

Batch study of liquid-phase adsorption of methylene blue using cedar sawdust and crushed brick

This paper presents a study on the batch adsorption of basic dye, methylene blue, from aqueous solution (40 mg L(-1)) onto cedar sawdust and crushed brick in order to explore their potential use as low-cost adsorbents for wastewater dye removal. Adsorption isotherms were determined at 20 degrees C and the experimental data obtained were modelled with the Langmuir, Freundlich, Elovich and Temkin isotherm equations. Adsorption kinetic data determined at a temperature of 20 degrees C were modelled using the pseudo-first and pseudo-second-order kinetic equations, liquid-film mass transfer and intra-particle diffusion models. By considering the experimental results and adsorption models applied in this study, it can be concluded that equilibrium data were represented well by a Langmuir isotherm equation with maximum adsorption capacities of 142.36 and 96.61 mg g(-1) for cedar sawdust and crushed brick, respectively. The second-order model best describes adsorption kinetic data. Analysis of adsorption kinetic results indicated that both film- and particle-diffusion are effective adsorption mechanisms. The Influence of temperature and pH of the solution on adsorption process were also studied. The extent of the dye removal decreased with increasing the solution temperature and optimum pH value for dye adsorption was observed at pH 7 for both adsorbents. The results indicate that cedar sawdust and crushed brick can be attractive options for dye removal from dilute industrial effluents.     

A formal approach to AADL model-based software engineering

International Journal on Software Tools for Technology Transfer - Formal methods have become a recommended practice in safety-critical software engineering. To be formally verified, a system should...     

Kinetic and equilibrium study for the sorption of cadmium(II) ions from aqueous phase by eucalyptus bark

The efficiency of eucalyptus bark as a low cost sorbent for removing cadmium ions from aqueous solution has been investigated in batch mode. The equilibrium data could be well described by the Langmuir isotherm but a worse fit was obtained by the Freundlich model. The five linearized forms of the Langmuir equation as well as the non-linear curve fitting analysis method were discussed. Results show that the non-linear method may be a better way to obtain the Langmuir parameters. Maximum cadmium uptake obtained at a temperature of 20 degrees C was 14.53mgg(-1). The influence of temperature on the sorption isotherms of cadmium has been also studied. The monolayer sorption capacity increased from 14.53 to 16.47 when the temperature was raised from 20 to 50 degrees C. The DeltaG degrees values were negative, which indicates that the sorption was spontaneous in nature. The effect of experimental parameters such as contact time, cadmium initial concentration, sorbent dose, temperature, solution initial pH, agitation speed, and ionic strength on the sorption kinetics of cadmium was investigated. Pseudo-second-order model was evaluated using the six linear forms as well as the non-linear curve fitting analysis method. Modeling of kinetic results shows that sorption process is best described by the pseudo-second-order model using the non-linear method. The pseudo-second-order model parameters were function of the initial concentration, the sorbent dose, the solution pH, the agitation speed, the temperature, and the ionic strength.     

Modeling of adsorption isotherms of phenol and chlorophenols onto granular activated carbon. Part II. Models with more than two parameters

The adsorption equilibrium isotherms of five phenolic compounds, phenol, 2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol, from aqueous solutions onto granular activated carbon were studied and modeled. In order to determine the best-fit isotherm, the experimental equilibrium data were analyzed using thirteen adsorption isotherm models with more than two-parameter; nine three-parameter equations - the Redlich-Peterson, Sips, Langmuir-Freundlich, Fritz-Schlunder, Radke-Prasnitz (three models), Tóth, and Jossens isotherms - three four-parameter equation - the Weber-van Vliet, Fritz-Schlunder, and Baudu isotherms - and one five-parameter equation - the Fritz-Schlunder isotherm. The results reveal that the adsorption isotherm models fitted the experimental data in the order: Baudu (four-parameter)>Langmuir-Freundlich (three-parameter)>Sips (three-parameter)>Fritz-Schlunder (five-parameter)>Tóth (three-parameter)>Fritz-Schlunder (four-parameter)>Redlich-Peterson (three-parameter). The influence of solution pH on the adsorption isotherms of 4-CP was investigated. It was shown that the solution pH has not an effect on the adsorption isotherms for pH相似文献   

Study on QoS Management for Video Streaming in Vehicular Ad Hoc Network (VANET)

Wireless Personal Communications - Vehicular Ad Hoc Network (VANET) is a particular type of MANET providing various wireless communications such as infrastructure communications and inter-vehicle...