Design of low power single-stage bias current control technique- based DVGA for LTE receivers

Analog Integrated Circuits and Signal Processing - In this study, a novel single-stage Digital Variable Gain Amplifier architecture (DVGA) was presented for Long Time Evolution (LTE) receivers. The...     

SOS: Self‐organized secure framework for VANET

While authentication is a necessary requirement to provide security in vehicular ad hoc networks, user's personal information such as identity and location must be kept private. The reliance on road side units or centralized trusted authority nodes to provide security services is critical because both are vulnerable, thus cannot be accessed by all users, which mean security absence. In this paper, we introduce a self‐organized secure framework, deployed in vehicular ad hoc networks. The proposed framework solution is designed not only to provide an effective, integrated security and privacy‐preserving mechanism but also to retain the availability of all security services even if there are no road side units at all and/or the trusted authority node is compromised. A decentralized tier‐based security framework that depends on both trusted authority and some fully trusted nodes cooperated to distribute security services is presented. Our approach combines the useful features of both Shamir secret sharing with a trust‐based technique to ensure continuity of achieving all security services. Mathematical analysis of security issues that the proposed framework achieves as well as the availability of offering security services is provided. Proposed framework examination was done to show the performance in terms of storage, computation complexity, and communication overhead as well as its resilience against various types of attacks. Comparisons with different types of security schemes showed that the protocol developed gave better results in most comparison parameters while being unique ensuring continuity of security services delivery.     

Estimation of Crack Closure Stresses for In Situ Toughened Silicon Nitride with 8 wt% Scandia

An 8-wt%-scandia silicon nitride with an elongated grain structure was fabricated. The material exhibited high fracture toughness (∼ 7 MPa · m^1/2) and a rising R -curve as measured by the indentation strength technique. The "toughening" exponent m was found to be m ∼ 0.1. The high fracture toughness and R -curve behavior was attributed mainly to bridging of the crack faces by the elongated grains. The crack closure (bridging) stress distribution in the wake region of the crack tip was estimated as afunction of crack size from the R -curve data, with an arbitrarily assumed distribution function.     

Vacuum Drying of Common Date Pulp Cubes

Drying ability of date (Phoenix dactylifera L.) pulp cubes from three Algerian common varieties (Mech-Degla, Degla-Beida, and Frezza) were investigated. Drying process was carried out under partial vacuum (200 mbar) at 60, 80, and 100°C. Compared to the Newton model, the Henderson and Pabis model better described drying kinetic of Mech-Degla and Frezza pulps at 60 and 80°C with a mean relative error (MRE) not higher than 6.07%. The same model fits experimental data at 60°C for Degla-Beida (R² = 0.988; MRE = 6.07) as well as at 100°C for only Mech-Degla (R² > 0.98, MRE = 8.61%).     

The role of polyaniline salts in the removal of direct blue 78 from aqueous solution: A kinetic study

Three polyaniline salts (PANI–H₂SO₄, PANI–H₃PO₄, and PANI–HNO₃) have been synthesized by chemical oxidative polymerization of aniline. They have been tested as adsorbents for the removal of the textile dye direct blue 78 (DB78) from aqueous solution. The interaction followed pseudo-second-order kinetics whether the rate of interaction was measured from the depletion of dye concentration in solution or the increase in the amount of dye adsorbed on the PANI surface. The removal rate was a function of the activity of the polymer as well as the reaction parameters of the polymer/dye system. The activity of the PANI depended on the polymerization conditions. These conditions involve the concentration of aniline, ammonium peroxydisulfate as oxidant, and sodium dodecylsulfate (SDS), the type of dopant acid (H₂SO₄, H₃PO₄, HNO₃), and the polymerization time. Higher removal rate was observed at oxidant/aniline mole ratio equals 1. The rate of removal was in the order PANI–H₃PO₄ > PANI–H₂SO₄ > PANI–HNO₃. The rate decreased with increasing the concentration of DB78 and pH. It increased with increasing the load of PANI. Pseudo-second-order kinetics, external surface adsorption, and intraparticle diffusion models were concurrently operating in the removal of DB78 with PANI.     

Soil Penetration Modeling in Microtunneling Projects

As the need for utility service line replacement or repairs with minimum disruption to the surface have increased, so has the demand for trenchless excavation methods, in particular, microtunneling. Microtunneling is a trenchless technique that is used to install new pipelines. Microtunneling can be applied in gravity and pressure lines, permanent ducts for cables, and crossings under rails or roads. When bidding a microtunneling project, the main concern of microtunneling contractors is predicting the underground behavior of the machine. In other words, the productivity of microtunneling is the key to profit in microtunneling projects. Contractors generally predict approximate productivity based on experience, which risks cost estimation accuracy for microtunneling projects. Contractors lack a productivity model that helps them to predict driving time. This paper is a part of a series of papers covering the productivity of microtunneling projects. This paper focuses on predicting the penetration time of the microtunneling machine.     

Hybrid nanostructure of polypyrrole and porous silicon prepared by galvanostatic technique

Nanostructured porous silicon (PS) layer is prepared in a lightly doped p-type substrate (with pores < 5 nm) and used as a working electrode to deposit conducting polypyrrole (PPy) by the electrochemical oxidative polymerization technique in an organic liquid phase. Three distinguishable stages of PPy deposition are observed and recorded under constant applied current: nucleation of polymer at the pore bottom, unidirectional growth of PPy inside the pores, and polymerization outside the PS surface. The hybrid nanostrucutre of PS/PPy shows a significant improvement of electrical conductivity as opposed to the unmodified PS layer. The improved conductivity is observed in spite of the formation of insulating layer of silicon oxides as detected by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) measurements. Systematic study of fabrication and characterization of this organic-inorganic heterosystem, quantification of the PPy in the PS matrix, and the mechanism of filling the nanopores with polymer are presented and thoroughly discussed.     

Deficit in prepulse inhibition in mice caused by dietary n-3 fatty acid deficiency.

Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) may be biosynthesized from a precursor α-linolenic acid (LNA) or obtained preformed in the diet. Dams were fed four diets with different levels of the various n-3 fatty acids during pregnancy and lactation, and their offspring were weaned to the same diets: “n-3 Deficient,” containing (as % total fatty acids) 0.07% of LNA; “Low LNA” (0.4%); “High LNA” (4.8%); and a “DHA + EPA” diet, containing 0.4% of LNA, 2% DHA, and 2% EPA. Sensorimotor gating was measured by prepulse inhibition (PPI) of the acoustic startle response in C57Bl6 mice. The n-3 Deficient and Low LNA diets caused a substantial deficit in PPI compared to the DHA + EPA diet, whereas the High LNA diet induced a less pronounced, but significant reduction of PPI. These are the first data that demonstrate a deficit in sensorimotor gating in rodents caused by an inadequate amount of the n-3 fatty acids in the diet. Our results differentiate the effects of a High LNA diet from one with added EPA and DHA even though the difference in brain DHA content is only 12% between these dietary groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Identification of a friction model at tool/chip/workpiece interfaces in dry machining of AISI4142 treated steels

The characterization of frictional phenomena at the tool–chip–workpiece interface remains an issue. This paper aims to identify a friction model able to describe the friction coefficient at this interface during the dry cutting of a AISI4142 treated steel with TiN coated carbide tools. A new tribometer has been designed in order to reach relevant values of pressures, temperatures and sliding velocities. This set-up is based on a modified pin-on-ring system. Additionally a numerical model simulating the frictional test has been associated in order to identify local phenomena around the spherical pin, from the standard macroscopic data provided by the experimental system. A range of cutting speeds and pressures has been investigated. It has been shown that the friction coefficient is mainly dependant on the sliding velocity, whereas the pressure has a secondary importance. Moreover a new key parameter has been revealed, i.e. the average local sliding velocity at the contact. Finally a new friction model has been identified based on this local sliding velocity.     

Thermal regime, groundwater flow and petroleum occurrences in the Cap Bon region, northeastern Tunisia

The Cap Bon region of northeastern Tunisia is part of a young continental margin that presents a thick column of sediments deposited mainly during Cretaceous and Miocene extended tectonic episodes. This sedimentary package is characterised by broad synclines alternating with NE–SW trending anticlines, and is affected by numerous NE–SW, NW–SE and E–W striking faults. Oligo-Miocene sandstones constitute the most important potential reservoir rocks in the region.The distribution of subsurface temperatures in the Cap Bon basin reflects local groundwater circulation patterns and correlates with the location of known oil and gas fields. The results of geothermal studies could therefore prove useful in the search for new hydrocarbon resources in the region. Subsurface temperatures were measured in deep oil exploration and shallow water wells. Local geothermal gradients range from 25 to 35 °C/km, showing higher values in the Korbous and Zennia areas, which correspond to zones of groundwater discharge and convergence in the Oligo-Miocene aquifer system, respectively.Analysis of thermo-hydraulic and geochemical data relative to the thermal springs in the Korbous region along the Mediterranean coast has made a useful contribution to geothermal prospecting for potential deep reservoirs. Positive geothermal gradient anomalies correspond to areas of ascending thermal waters (i.e. discharge areas), whereas negative anomalies indicate areas of infiltrating colder meteoric waters (i.e. recharge areas). The zones of convergence of upward-moving water and groundwater may be associated with petroleum occurrences.