Sol-Gel Preparation and Spectroscopic Properties of Modified Sodium Silicate /Tartrazine Dye Nanocomposite

Silicon - Thin film nanocomposites of sodium silicate (80 SiO2 –20 Na2O)/ tartrazine dye (E102) prepared using sol gel process in acidic system. The change in the physicochemical properties...     

Clay compaction modelling by homogenization theory

The modelling of hydromechanical behavior of clayey sediments by homogenization theory is described. The rheological model of clays buried in depth requires a three-dimensional approach and laboratory experiments to quantify the model parameters. An iterative process which can be coupled to any homogenization method is used to model the porous media behavior. Hydromechanical compaction results from oedometric experiments are simulated with the proposed model.     

Simulation of the deflected cutting tool trajectory in complex surface milling

Since industry is rapidly developing, either locally or globally, manufacturers witness harder challenges due to the growing competitivity. This urges them to better consider the four factors linked to production and output: quality, quantity, cost and price, quality being of course the most important factor which constitutes their main concern. Efforts will be concentrated??in this research??on improving the quality and securing more accuracy for a machined surface in ball-end milling. Quality and precision are two essential criteria in industrial milling. However, milling errors and imperfections, due mainly to the cutting tool deflection, hinder the full achieving of these targets. Our task, all along this paper, consists in studying and realizing the simulation of the deflected cutting tool trajectory, by using the methods which are available. In a future stage, and in the frame of a deeper research, the simulation process will help to carry out the correction and the compensation of the errors resulting from the tool deflection. The corrected trajectory which is obtained by the method mirror will be sent to the machine. To achieve this goal, the next process consists??as a first step??in selecting a model of cutting forces for a ball-end mill. This allows to define??later on??the behavior of this tool, and the emergence of three methods namely the analytical model, the finite elements method, and the experimental method. It is possible to tackle the cutting forces simulation, all along the tool trajectory, while this latter is carrying out the sweeping of the part to be machined in milling and taking into consideration the cutting conditions, as well as the geography of the workpiece. A simulation of the deflected cutting tool trajectory dependent on the cutting forces has been realized.     

Heterogeneous Wireless Networks: Configuration and Vertical Handoff Management

Vertical handoff is one of the most important issues for the next generation heterogeneous wireless networks. However, in many situations, unbeneficial vertical handoffs occur across intersystem heterogeneous networks cause network performance degradation. Therefore, we propose a novel configuration architecture that can be deployed in the next generation of wireless networks. Second, we propose a predictive and adaptive Vertical Handoff Decision Scheme that optimizes the handoff initiation time as well as selection of the most optimal network. The proposed vertical handoff decision algorithm considers the technology type as well as the Signal to Interference Ratio (SIR), the Mobile Station (MS) velocity, the user preferences, the applications requirements and the terminal capabilities as the most important factors to make vertical handoff decision. In order to minimize handoff costs, the proposed decision algorithm uses the dwell timer concept. The handoff costs are analyzed in terms of unnecessary and unbeneficial handoffs rate.The simulation results show that the reduction of unnecessary handoffs proposed in our vertical handoff decision scheme reduces the handoff blocking probability, the packets loss rate and the handoff overhead     

An integrated approach to the synthesis of geometrically non-linear structures

An integrated approach to the minimum weight design of geometrically non-linear three dimensional truss structures with geometric imperfections, subject to inequality constraints on static displacements, stresses, local buckling and cross sectional areas, is investigated. The integrated structural synthesis problem involves design and response quantities as independent variables and equilibrium equations, describing the finite element model, as equality constraints. The non-linear structural analysis and the optimization are thus merged together into a single process. A computer program developed to compute the contraint values and analytical gradients is coupled with a generalized reduced gradient algorithm to solve the integrated problem. Numerical results for a geometrically non-linear shallow dome example problem are presented for various types of imperfections. Furthermore, it is found that the algorithm is capable of detecting and guarding against system as well as element elastic instability using equilibrium information only, that is, without imposing system and local buckling inequality constraints.     

Interference analysis for asynchrounous OFDM/FBMC based cognitive radio networks over Rayleigh fading channel

In the future fifth generation networked society, devices will suffer from the asynchronous multi-carrier effect which impacts the user’s quality of experience. This paper investigates the timing misalignment effect on interference level in the context of a cognitive radio (CR) network. Our study considers both multicarrier techniques orthogonal frequency division multiplexing (OFDM) and filter bank multicarrier (FBMC). The originality of our paper consists in proposing a simple but accurate analytical model to evaluate our system’s performance in terms of interference level, signal-to-interference-plus-noise ratio and bit error rate. Specifically, two case studies are considered, a single-user case (one primary user and one secondary user) and a multi-user case with exact theoretical expressions of interference level. We had also made a comparison between OFDM and FBMC techniques. The most striking observation to emerge from our results is that the asynchronous interference is inversely propositional to timing offset even for the multi-user case, and that differences in the normalized interference level between the single/multi-user cases is barely perceived for the FBMC technique, proving its efficiency. Our simulations’ results had further strengthened our confidence in the suggested model. It shows that FBMC is best suited for CR networks since it provides BER improvements compared to OFDM.

     

Live video streaming service with pay-as-you-use model on Ethereum Blockchain and InterPlanetary file system

Wireless Networks - In centralized video streaming platforms, the platform owner, rather than the content producer, controls most of the content uploaded on the centralized video...     

Effects of alkali addition on the mechanical properties and durability of concrete

Increasing the concrete alkali content from 0.6% to 1.25% of Na₂O_e of the cement mass by adding NaOH to the mixture water has harmful effects on most mechanical properties (compressive, splitting, direct tensile, and flexure strengths) of concrete made with a water-to-cement (w/c) ratio of 0.41 and limestone aggregates not susceptible to alkali-silica reaction (ASR), however not on the elasticity modulus measured under compression or direct tension. Shrinkage tests at 50% RH and 23 °C started after 7 days at 100% RH and 23 °C show that the low-alkali concrete shrinks more than the high-alkali one, despite similar water losses. Freeze-thaw tests performed on air-entrained concretes show that the two concretes resist well to freezing and thawing while showing similar air-void systems. When examined under the scanning electron microscope (SEM), the hydrates in the two concretes present similar microstructure; however, the high-alkali concrete shows a more reticular and porous microtexture, which could explain the reduction in strength.     

“<Emphasis Type="SmallCaps">disassembly plan approach based on subassembly concept</Emphasis>”

A three-dimensional numerical model is established to study the temperature and fluid flow fields in the twin-wire gas metal arc welding (GMAW) process. The high-speed photography system is used to capture the images of the weld pool during the welding. Based on simulation and experimental results, the weld pool formation, convection, and stability in twin-wire GMAW process are investigated. Both “push-pull” and outward flow patterns exist in the twin-wire GMAW weld pool, which can contribute to decreasing the height of the bulge and increasing the width of the pool. The convection in the weld pool can proceed adequately, the arc force between the leading and trailing arcs is relatively balanced, surface tension normal force is uniform along the liquid channel, and the liquid channel is capillary stable, all of those contribute to the stability of the weld bead. The simulation results are in good agreement with those in the experiment.