The influence of solid-phase concentration on the performance of electrorheological fluids in dynamic squeeze flow

The yield stress of electrorheological (ER) fluids increases by orders of magnitude when electric field is applied across them. In the absence of the field, ER fluids behave as Newtonian fluids. This paper is concerned with an experimental investigation to determine the rheological performance of ER fluids, consisting of a dielectric liquid carrier with a range of solid-phase concentration. The ER fluid was contained in a squeeze cell, which during motion subjects the fluid to both compressive and tensile loading. The results were analysed in terms of the capacity for the transmission of imposed forces across the fluid and showed a great dependence on the applied D.C voltage and the weight fraction of the dispersed solid-phase. In addition, the implications of the results to vibration control, where the ER fluid is employed in an engine mount, are discussed.     

Multilayer Transitions in Spin-3/2 Blume–Capel Model with RKKY Interaction in a Transverse Field

Using mean-field theory, we have studied the effect of quantum transverse field on the magnetic properties and multilayer transitions in the spin-3/2 Blume–Capel model with RKKY interaction. The system is formed by two magnetic multilayer materials, of different thicknesses, separated by a non magnetic spacer of thickness M. It is found that there exist critical transverse fields above which the multilayer transitions occur. This critical value decreases when increasing the thickness of the nonmagnetic spacer M. Phase diagram is established in different plane of space parameter.     

Precipitation of low molecular weight phenolic compounds of grape seeds cv. Carménère (<Emphasis Type=Italic>Vitis vinifera</Emphasis> L.) by whole saliva

Low molecular weight phenolic compounds (LMWP) contribute to astringency and bitterness, two important sensory attributes. This work aimed to study the interactions between human saliva and a group of LMWP from a grape seed extract, namely, monomers, dimers and trimers of flavan-3-ol plus gallic acid. LMWP in the sediment that was produced by mixing whole saliva with the grape seed extract were identified by high-performance liquid chromatography analysis (HPLC–DAD). Two assays to produce LMWP-salivary protein sediments were carried out. An indirect assay consisted of in vitro mixing aliquots of saliva with a constant volume of the grape seed extract followed by centrifugation and sediment analysis. In a direct assay, aliquots of the grape seed extract were mixed in-mouth with saliva, returned to a vessel and centrifuged. In each assay, polyphenol composition of the sediments varied according to the tannin/saliva vol/vol ratio although in both cases monomeric LMWP were the most abundant polyphenol components of the sediments. The study also suggested the need for a strict control of the in vitro experimental conditions used to mimic the in vivo conditions in which tannin–protein interactions do occur and produce astringency perception.     

Effect of phosphoric acid on the performance of low antimony grid of Pb‐acid cell under constant current charging and discharging

Effect of phosphoric acid on the performance of Pb‐1.7%Sb grid of lead‐acid cell is studied in 5 M H₂SO₄ by cyclic galvanostatic polarization and impedance spectroscopy. An increase in capacitance to a maximum is recorded during the initial stages of the electro‐reduction of PbO₂ into Pb(II) compounds and attributed to concurrent compositional and dimensional changes. These changes include removal of O₂ bubbles, insertion of large amounts of H₂SO₄ and H₂O. Efficiency of PbO₂ formation decreases, while its rate of self‐discharge increases with increasing the charging current and in the presence of H₃PO₄. The charge capacity increases with increasing the discharging current due to the decrease in the self‐discharge. The charge capacity is lower in the presence of H₃PO₄. On increasing the cycle number, the corrodibility of the grid increases, because more layers of the surface Pb are involved in the self‐discharge. H₃PO₄ significantly retards the effect of cycle number.     

Source localization using TDOA and FDOA measurements based on modified cuckoo search algorithm

This paper introduces a new algorithm for solving the localization problem of moving multiple disjoint sources using time difference of arrival and frequency difference of arrival. The localization of moving sources can be considered as a least-square problem. There are many algorithms used to solve this problem such as, two-step weighted least squares, constrained total least-square and practical constrained least-square. However, most of these algorithms suffer from either slow convergence or numerical instability and don’t attain Cramer–Rao lower bound. We introduce a free-gradient algorithm called cuckoo search which avoids the slow convergence problem. The cuckoo search provides a combined global and local search method. Simulation results show that the proposed algorithm achieves better performance than other algorithms and attains Cramer–Rao lower bound.     

A hydrodynamic transport model and its applications in semiconductor device simulation

In this paper, a generalized hydrodynamic model that includes four conservation equations for a general, position-dependent energy band structure and effective mass is presented. An analytical mobility model is extended to simulate two-valley semiconductor devices. A semiconductor device simulation package, DYNA, is introduced. Simulation results for both bulk materials and submicron-gate GaAs MESFETs show good agreement with experimental data and Monte Carlo device simulation results.     

Capacitance and conductance of ZnxCd1-xS/ZnTeheterojunctions

Capacitance-voltage and conductance-voltage characteristics of RF-sputtered ZnCdS films on ZnTe single crystals are studied as a function of frequency up to 1 MHz. It is found that the measured capacitance decreases with frequency while the conductance increases. A physical circuit model of the junction is proposed to explain this dependence. A relationship relating the junction capacitance to the polycrystalline film properties and the built-in voltage of the junction is derived. It shows that the junction capacitance is related to the average carrier concentration rather than the doping concentration of the polycrystalline material. From a C^-2 versus V plot an average carrier concentration in the films which is in good agreement with that obtained by Hall measurement is obtained. The lower average electron concentration in the ZnCdS film near the substrate is due to either interdiffusion of Cd from the film into substrate or due to higher density of grain boundary states in the starting deposition portion of the film     

Holographic SAR image formation by coherent summation of impulseresponse derivatives

Using the physical optics approximation, the radar image of a target can be constructed from a knowledge of the monostatic backscattered field or hologram for all frequencies and all aspects angles. The target image is the two-dimensional Fourier transform of the hologram. This is based on the same principle as conventional holography. In the near-field the image is computed by the coherent summation of back-projected range responses which are derived from complex impulse responses. Consequently, the image can be interpreted as a tomographic reconstruction. If the target is within the antenna beam at each radar position in the linear synthetic-aperture radar (SAR) geometry, then the algorithm for the coherent summation of impulse response derivatives (IRDs) can be applied. Experimental results for the near-field of a wheat field and a Peugeot 504 automobile are presented to verify the effectiveness of the method     

Enhanced fair earliest due date first scheduling strategy for multimedia applications in LTE downlink framework

Guaranteeing a certain delay threshold for delay‐sensitive applications in long term evolution (LTE) cellular communication system is a very challenging mission. By implementing an optimal scheduling strategy, this mission will be achieved. In this article, a novel scheduler is introduced in order to meet a predefined level of service quality by guaranteeing a specific delay threshold for delay‐sensitive applications in LTE cellular systems. The proposed scheduler assigns the available resource blocks (RBs) to active user equipments (UEs) tacking into consideration several attributes. The expiration date of each packet, the channel quality, the average data rate previously achieved by each UE, and the number of dropped packets for each UE compared with the average number of packets totally dropped are all considered in the proposed scheduler working mechanism. Consequently, the proposed scheduling strategy reduces the number of packets dropped for multimedia applications, and at the same time maximizes the overall throughput of the network. Simulation results are provided to study and evaluate the performance of the proposed scheduling strategy. A comparative study is presented between the proposed strategy and the most recent scheduling techniques. The obtained results prove that the proposed scheduling strategy has considerably acceptable and appreciated results compared with the results of the state‐of‐the‐art scheduling techniques.     

Synthesis and Characterizations of p-Type Kesterite Ag 2 ZnSnS 4 Thin Films Deposited by Spray Pyrolysis

The fabrication of absorber materials based on kesterite materials has attracted considerable attention in recent articles owing to their excellent optical and electrical properties. In this work, we present the synthesis of Ag2ZnSnS4 films with different thicknesses using a cost-effective spray pyrolysis method. X-ray diffraction was used to check the tetragonal phase and the highly oriented nature of the Ag2ZnSnS4 films. Optical data analysis indicates that a direct allowed transition has appeared in the Ag2ZnSnS4 thin films. The optical results reveal that the energy gap decreases from 1.5 eV to 1.23 eV via enlarging the film thickness of the Ag2ZnSnS4 thin films. Moreover, the dispersion parameters obtained via the Wemple–DiDomenico model and the nonlinear optical parameters of the Ag2ZnSnS4 samples were computed and analyzed.