Sensitive magnetic field sensor using 2D magnetic photonic crystal slab waveguide based on BIG/GGG structure

A kind of magnetic field sensor (MFS) using a two-dimensional (2D) magnetic photonic crystal (MPC) slab waveguide as the sensing structure is proposed and investigated numerically. The slab structure is based on bismuth iron garnet (BIG), a well-known magnetic material with effective magnetooptical (MO) properties, sandwiched with gadolinium gallium garnet (GGG) as substrate. The complete photonic bandgap (PBG) of the 2D MPC is simulated and optimized for realization of polarization-independent waveguides. The simulation results show that the width and position of the complete PBG depend on the thickness of the BIG slab and the radius of the air holes used in the design. By reducing the lightwave propagation losses and enhancing the mode conversion ratio, increased sensitivity is obtained. Based on the Faraday effect, a good linear relationship is observed between the normalized output light intensity and the magnetic field strength as the gyrotropy parameter g is varied from 0.13 to 0.19, a g-range used as the sensor dynamic range. The remarkable enhancement in sensing performance due to the MO effect makes the designed device suitable for magnetic field sensing. The results are discussed to provide a basis for investigation of 2D MPC slab waveguides based on the same structure, which are of particular interest for development of highly sensitive MFSs.     

A constraint consensus memetic algorithm for solving constrained optimization problems

Constraint handling is an important aspect of evolutionary constrained optimization. Currently, the mechanism used for constraint handling with evolutionary algorithms mainly assists the selection process, but not the actual search process. In this article, first a genetic algorithm is combined with a class of search methods, known as constraint consensus methods, that assist infeasible individuals to move towards the feasible region. This approach is also integrated with a memetic algorithm. The proposed algorithm is tested and analysed by solving two sets of standard benchmark problems, and the results are compared with other state-of-the-art algorithms. The comparisons show that the proposed algorithm outperforms other similar algorithms. The algorithm has also been applied to solve a practical economic load dispatch problem, where it also shows superior performance over other algorithms.     

Removal of cyanide in aqueous solution by oxidation with hydrogen peroxide in presence of copper-impregnated activated carbon

This work is devoted to the removal of free cyanide from aqueous solution by oxidation with hydrogen peroxide H₂O₂ catalyzed by copper-impregnated activated carbon. Effects of initial molar ratio [H₂O₂]₀/[CN⁻]₀, copper-impregnated activated carbon amount, pH and the temperature on cyanide removal have been investigated.The presence of copper-impregnated activated carbon has increased the reaction rate showing thus a catalytic activity. The rate of cyanides removal increases with the raise of the initial molar ratio [H₂O₂]₀/[CN⁻]0 and decreases with the increase in the pH from 8 to 12. The increase in the copper-impregnated activated carbon amount from 1.5 to 10 g/L in reaction solution has a beneficial effect. Beyond this value, the impact of activated carbon amount is not anymore significant. The temperature does not have a significant effect between 20 and 35 °C. The four successive times re-use of catalyst shows a good stability. The kinetics of cyanide removal has been found to be of pseudo-second-order with respect to cyanide and the rate constants have been determined. This process seems very interesting because the rate of cyanides removal is very fast, the reaction does not use soluble metal catalyst and it consumes only hydrogen peroxide as chemical product.     

Hydrogen and water vapor adsorption on and reaction with uranium

By combining modulated molecular beam scattering, temperature programmed desorption, and atomic force microscopy experiments, the fundamental properties of the interaction of hydrogen and water vapor with uranium at room temperature and above have been investigated. The initial sticking probability, hydride formation probabilities and desorption kinetics for dihydrogen and water vapor on clean uranium have been measured. In addition, saturation coverages for hydrogen and water vapor are determined for an initially clean uranium surface. Atomic force microscopy revealed site-specific initiation of hydride formation for slightly oxidized uranium at grain boundaries. The areal (and hence time) dependence of the hydride formation probability was also observed. The clean uranium surface is passivated significantly by oxidation and carburization. The sticking probabilities for dihydrogen and water vapor are one to two orders of magnitude smaller on oxidized and carbided surfaces. The carbided surface is efficiently produced by reaction of C₆₀ with uranium surfaces between 600 and 800 K.     

Conception d’une solution de sélection de passerelles Internet dans les réseaux ad hoc

In the past few years, Internet has raised increasing interest in various areas including research, education, and business. The number of people accessing the Internet at work or at home has increased considerably, just like the number of services offered (email, e-commerce, search engines, e-learning, e-government, etc.). Ad hoc networks were generally viewed as stand-alone networks, where communications are only supported between nodes in the network such as in military and rescue operations. The lack of connectivity to the wired infrastructure enables simple management and deployment, but limits the applicability of ad hoc networks to today’s scenarios, which require connectivity outside the ad hoc network and particularly to the Internet. However, to reach this goal, a number of problems need to be resolved because of the dynamic nature of such environment. In this article, we describe a new solution for dynamic gateway selection based on quality of service (QoS) criteria. The underlying architecture is based on a pro-active routing protocol.     

Resolution enhanced ESPRIT

The authors present a variant of ESPRIT, known as the resolution enhanced (RE)-ESPRIT, that lowers resolution thresholds by incorporating left weighting of the signal eigenvectors to provide sector focusing. They discuss the advantages of this new left weighted ESPRIT. A compact expression for the asymptotic covariance matrix of the estimates is presented. Analytical and simulation results are included to show the resolution improvement of ESPRIT     

Groundwater recharge and pollution in Wadi El‐natrun,Egypt

The isotopic compositions of deuterium, oxygen‐18, tritium and nitrogen‐15 were determined for some groundwater samples from Wadi El‐Natrun area. The distribution pattern of the environmental isotopes could be explained by the differences in the degree of mixing between three major sources of recharge to the Wadi El‐Natrun aquifer: River Nile water, paleowater and drainage water from Nubarya reclamation project. The analysis of ¹⁵N‐nitrate indicates a mixing process     

Optothermal properties of fibres

Studies of the mechanical and optical properties of undrawn polypropylene fibres by annealing and drawing were performed. The optical properties and strain produced in polypropylene fibres at different conditions were measured interferometrically at room temperature. It was found that as the draw ratio of the fibre increased, its birefringence, Δn_a, increased at a constant rate, and then nearly levelled off. The refractive index, n ^∥, and polarizability, p ^∥, increased with different draw ratios; but for fibres annealed at 70 and 100°C, there were no acceptable variations. For fibres annealed at 130°C, n ^∥ and p ^∥ increased compared to those fibres annealed at 70 and 100°C. An empirical formula has been suggested to explain the relationship between the cross-sectional area of polypropylene fibres with the draw ratio, and the constants of this formula have been determined. The effect of annealing on the refractive index profile of undrawn polypropylene fibres, before and after thermal treatment, was studied. The strain optical coefficient and the Poisson's ratio were calculated over different draw ratios. The results obtained clarify the effect of annealing time and temperature with different draw ratios on the optical behaviour of polypropylene fibres. Microinterferograms are given for illustration.     

Optical-fibre network system for air-pollution monitoring over a wide area by optical absorption method

A low-loss optical-fibre network system for monitoring air pollution and species concentrations in various environments utilising the differential absorption method is proposed and discussed as a sensitive and economical as well as nonhazardous method. Its feasibility and advantages are also described on the basis of the present state of the art of the relevant technology.     

Effects of sand and process water pH on toluene diluted heavy oil in water emulsions in turbulent flow

The presence of sand in heavy oil production is known to enhance oil recovery. Sand can also be detrimental depending on the properties of the sand–water interface. In this process, the water soluble material interacts with both sand and oil droplets and affects emulsion stability. The formation and stability of heavy oil‐in‐water emulsions during turbulent flow using batch process stirred‐tank mixing of oil, sand, and water were investigated at three pH. Size distributions were measured by laser diffraction. High‐speed video photomicrography was used to observe the process during mixing. Results showed that the presence of sand enhanced formation of stable, fine emulsion at basic pH 8.5. When the pH of the water was reduced below 6.5 both sand and droplets surface properties changed, the emulsions became less stable and coalescence was apparent. The sand grains acted as coalescers at low pH and enhanced breakage at high pH. © Her Majesty the Queen in Right of Canada, as represented by the Minister of Natural Resources, 2008 AIChE J, 2009