Alloy broadening effect on optical properties of InGaAs grown by MOCVD with TMAs precursor

We investigate the MOCVD growth characteristic of the In_0.47Ga_0.53As layers lattice matched to InP using TMAs as an alternative source of arsine. Improvement of the InGaAs quality was studied by means of PL lines, the origin of photoluminescence (PL), atomic force microscopy. Low temperature PL spectra exhibit a broad this broadening was analyzed using quantitative models for the linewidth of band exciton based on compositional fluctuations within the crystal volume. This statistical fluctuation of the composition affects not only the PL line width but also structural properties of the InGaAs epilayer. Furthermore, by increasing V/III ratio, a degradation of the InGaAs optical and structural quality was observed.     

Analysis of Thermal Effects on Electrical Characterization of AlGaN/GaN/Si FAT-HEMTs

In this paper we report on the characteristics of Schottky contact behavior of AlGaN/GaN High Electron Mobility Transistors (HEMTs) on a Si Substrate. A variety of electrical techniques such as capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) measurements have been used to characterize the diode. The behavior of the ideality factor n, the effective barrier height Φ_b, and the series resistance R_S is studied with temperature. C-V measurements successively sweeping up and down the voltage from 0 V to 12 V(absolute value) have demonstrated a hysteresis phenomenon which is more pronounced when the temperature increases. This parasitic effect can be attributed to the presence of traps activated in the Schottky diode. The related deep levels defects which are responsible for parasitic effects, were characterized and extracted by the Deep Level Transient Spectroscopy (DLTS) technique that has been used in previous studies. The identification of these traps showed a correlation between DLTS and C-V measurements.     

Optimal Placement of Near Ground VHF/UHF Radio Communication Network as a Multi Objective Problem

Wireless Personal Communications - Ultra high frequency (UHF) and very high frequency (VHF) bands are widely used with near ground applications especially for communication purposes. However, due...     

Phenolic constituents,antioxidant and antimicrobial activities of rosy garlic (Allium roseum var. odoratissimum)

The methanol extracts of leaves, flowers, stalks and bulbs of the North African endemic Allium roseum var. odoratissimum were analyzed for their phenolic profiles and screened for their antioxidant and antibacterial activities. Colourimetric analysis revealed that the highest levels of total phenols content (TPC) and total flavonoids content (TFC) were found in the flowers and leaves. The use of HPLC-PDA-MS allowed the identification of kaempferol 3,7-di-O-rhamnoside, kaempferol-3-Glucuronide, kaempferol-3-O-glucoside, kaempferol-3-O-beta-d-glucoside-7-O-alpha-l-rhamnoside, luteoline and apigenine, while four components remained unidentified. The flowers and leaves were found to possess the highest antioxidant activity with the exception in metal chelating ability. Antibacterial assay showed that Enterococcus feacium was the most susceptible bacterial strain and the stalk extract had the most effect in the inactivation of Staphylococcus aureus, Enterococcus feacium, Bacillus subtilis and Escherichia coli. Conclusively, this study allows a clear chemical differentiation between A. roseum var. odoratissimum and the other Allium species.     

Thermal effect on the dynamic behavior of nanobeam resonator assuming size-dependent higher-order strain gradient theory

Microsystem Technologies - The temperature change and size scale dependent effects on the dynamical behaviors of the Carbon nanotube (CNT)-based nano-resonator are investigated in this work. The...     

Implementation and Evaluation of Opportunistic Routing Protocols for Wireless and New Generation Communication Networks

Wireless Personal Communications - Current wireless networks are based on unicast routing protocol derived from wired networks. The purpose of this paper is to implement and to evaluate...     

Studies of dielectric relaxation in natural fibres reinforced unsaturated polyester

Dielectric properties on natural fibres reinforced unsaturated polyester were investigated. Dielectric spectra were measured in the frequency range from 10⁻¹ Hz to 10⁶ Hz and temperature interval from 40 °C to 150 °C. For the composite, three relaxation processes were identified. The first one is the α mode relaxation associated with the glass transition of the unsaturated polyester resin matrix. The second relaxation process associated with conductivity occurs as a result of the carriers charges diffusion noted for high temperature above glass transition and low frequencies. As for the third process, it is the interfacial or Maxwell–Wagner–Sillars (MWS) relaxation that is attributable to the accumulation of charges at the natural fibres/polyester resin interfaces. The third relaxation (MWS) was analysed using the Havriliak–Negami model and its intensity was calculated in order to probe the interfacial region between fibres and matrix. This analysis was accomplished by a thorough study of the fibres/matrix interfacial adhesion aspect, by using a differential scanning calorimeter (DSC) and a scanning electron microscope (SEM) observation.     

Monitoring the Coefficient of Variation Using a Variable Sampling Interval Control Chart

The coefficient of variation (CV) is a quality characteristic that has several applications in applied statistics and is receiving increasing attention in quality control. Few papers have proposed control charts that monitor this normalized measure of dispersion. In this paper, an adaptive Shewhart control chart implementing a variable sampling interval (VSI) strategy is proposed to monitor the CV. Tables are provided for the statistical properties of the VSI CV chart, and a comparison is performed with a Fixed Sampling Rate Shewhart chart for the CV. An example illustrates the use of these charts on real data gathered from a casting process. Copyright © 2012 John Wiley & Sons, Ltd.     

Inhibition of Carbon Steel Corrosion in Neutral Calcareous Synthetic Water by Eruca sativa Extract

Protection of Metals and Physical Chemistry of Surfaces - Here, by various electrochemical and analytical techniques, we have examined whether Eruca sativa aqueous extract can inhibit the corrosion...     

Adaptive control strategy‐based reference model for spacecraft motion trajectory

In aerospace field, the economic realization of a spacecraft is one of the main objectives that should be accomplished by conceiving the optimal propulsion system and the best control algorithms. This paper focuses on the development of a viable adaptive control approach (ACA) for spacecraft motion trajectory (SMT). The proposed strategy involves the nonlinear mathematical model of SMT expressed in the central field, which is linearized by the Taylor expansion, and the second Lyapunov method to offer a high rate and unfailing performance in the functioning. The adaptive control system is composed of the cascade of adaptation loop and feedback control loop. When the spacecraft deviates from its reference trajectory model, the ACA acts on the control system to correct this deviation and follow the optimal reference trajectory. Therefore, when the states of the adjustable model are different from its reference values, then the error signal is provided as an input to the adaptation law, which contains the adaptation algorithm. The output will be the state variable feedback control matrix, which will be used to calculate the new control law vector. The efficiencies of the linearization procedure and the control approach are theoretically investigated through some realistic simulations and tests under MATLAB. The steady‐state errors of control between the reference model and the adjustable model of SMT converge to zero. Copyright © 2014 John Wiley & Sons, Ltd.