A new iterative method for analysing nonlinear photonic-crystal structures

The article presents an efficient iterative method for analysing non-linear photonic crystals. The new approach is used for analysing a frequency converter constructed with a 2D pillar-type photonic crystal waveguide structure. The considered converter uses the non-linear properties and the compound waveguide structure. The analysis is based on the iterative resolution of two relationships between incident and reflected volume-waves. The reflection operator is expressed using Hankel functions. Numerical results have been obtained with moderate CPU time and memory requirement. Simulations obtained are in agreement with recent published results.     

Experimental study of the influence of the degree of saturation on physical and mechanical properties in Tournemire shale (France)

In addition to direct mechanical perturbations, an excavation influences rock conditions (mechanical, hydraulic and chemical properties). The internal fluids could be drastically modified and, in particular, the presence of water in the rock with regard to hydration and desiccation. The aim of the present study is to investigate the influence between the degree of saturation and the physical/mechanical properties for Tournemire shale rock. Anisotropy effects are also studied to identify hydromechanical behaviour. The different degrees of saturation are imposed by controlled suctions with continuous measurement of physical parameters such as weight and deformations. The volume variations (swelling or shrinkage behaviour) would result principally from the opening or closing of the inter-layers space. Uniaxial and triaxial compressive tests are carried out in order to attempt to establish a relationship between different mechanical parameters (elastic and failure data) and the sample saturation. The mechanical behaviour is sensitive to the saturation state of the shale with an important part of the stratification and its relative orientation to the mechanical stress.     

Potential of hydroxytyrosol-rich composition from olive mill wastewater as a natural disinfectant and its effect on seeds vigour response

Hydroxytyrosol-rich olive mill wastewater (HROMW) and hydroxytyrosol-rich composition (HRC) were prepared from olive mill wastewater using hydrolysis and post-hydrolysis purification processes. The HROMW and HRC showed powerful bactericidal and fungicidal activities against phytopathogens, and their minimal inhibition concentrations for fungi and bacteria were 7.18–57.4 mg l⁻¹ and 7.18–14.4 mg l⁻¹, respectively. After 5 min of contact time, the disinfectant properties of the HROMW and HRC added at concentrations of 1.25% (dw/v) allowed for a reduction in bacterial viability by greater than 5 log units. However, a higher concentration of 1.5–3% (dw/v) or a longer contact time of 30 min were needed to achieve values for fungal viability reduction that were higher than the 4 log units recommended by EN 1275 [EN 1275 (1997a). Chemical disinfectants and antiseptics. Basic fungicidial activity. Test method and requirements (phase 1)]. HROMW and HRC were less effective with the most ubiquitous fungi, Fusarium spp., which needed 10% dw/v. The addition of HRC at 10% (dw/v) showed that the composition was a potent exogenous enhancer of growth that stimulated the seedling vigour of tomato and muskmelon, according to the conventional agronomic parameters for seed vigour. Compared to the control, the germination percentage, shoot weight, shoot height, and root length were all significantly enhanced in the HRC-treated seed plants. HRC was found to have effective disinfectant properties against seed-borne diseases. In treated seeds, the composition had significant effects on the control of damping-off disease groups at the pre-germination stage. HRC was also equally effective in the control of root rot diseases caused by Fusarium sambucinum and Alternaria solani as well as of wilts and even bacterial seed-borne pathogens. HROMW was also found to be as effective as HRC in terms of its efficacy against the three seed-borne diseases mentioned above.     

A global electromagnetic modeling of an active microstrip structure

This article presents a new technique that uses the auxiliary sources for investigation of structures including nonlinear components. The proposed technique is implemented in the iterative method to model two transistors (MESFET and INGFET) and an MMIC amplifier. The numerical results are compared with published data and a good agreement is observed. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

The Performance of Water Floods with Horizontal and Multilateral Wells

The use of horizontal and multilateral wells in the oil industry has increased rapidly during the last two decades. The main reason for this upsurge is that horizontal and multilateral wells provide a large contact area with the reservoir, and therefore enhance the well productivity or injectivity better than conventional vertical wells. The high productivity coupled with the recent advances in drilling technology for horizontal and multilateral wells has made their application an economically viable option. In this study, the performance of nonconventional wells in water flooding projects was investigated using numerical simulation techniques. Extensive three-dimensional, fine-mesh simulation runs are performed to determine the oil recovery by nonconventional wells under different operating/reservoir conditions. Results show that the pattern used has a significant effect on the displacement performance of nonconventional wells. The study shows the various conditions under which nonconventional wells will perform better than the use of conventional vertical wells.     

Acute urine retention. Another presentation of a hydatid cyst of the kidney

We report on a case of hydatic cyst of the kidney, in a 12 year-old male, revealed by an acute urinary retention. After a brief report of the common signs of this parasitic disease, we emphasize the importance of hydaturia and acute urinary retention as another revealing sign of this disease.     

Elaboration,Stability and Enzymatic Degradation of Hydroxypropylcellulose/Polysiloxane Biocomposite Membranes

Biopolymers are promising alternatives to synthetic macromolecules for the design of composite materials complying with Green Chemistry principles. In this context, the conditions to associate hydroxypropyl-cellulose and polymethylhydrosiloxane within homogeneous membranes were studied. The stability of these membranes in water and in the presence of a cellulase enzyme were investigated by Thermogravimetric Analysis, Scanning Electron Microscopy and Fourier-Transform Infra-Red Spectroscopy. These investigations reveal that the biopolymer is still accessible to a solubilisation/degradation process without inducing the breaking down of the composite materials, opening the route to the design of novel membranes for environmental applications.     

Forecasting and maintenance problem under subcontracting constraint with transportation delay

In this paper, a forecasting production/maintenance optimization problem has been proposed with a random demand and single machine M₁ on a finite horizon. The function rate of the machine M₁ is depending on the production rate for each period of the forecasting horizon. In order to satisfy the customer, a subcontracting assures the rest of the production through machine M₂ with transportation delay. An analytic formulation of the problem has been proposed using a sequential computation of the optimal production plan for which an optimal preventive maintenance policy has been calculated based on minimal repair. Firstly, we find, the optimal production plans of principal and subcontracting machines, which minimises the total production and inventory cost for the cases without and with returned products under service level and subcontracting transportation delay. Secondly, we determine a joint effective maintenance policy with the optimal production plan, which integrates the various constraints for the production rates, the transportation delay and the returned production deadline. Numerical results are presented to highlight the application of the developed approach and sensitivity analysis shows the robustness of the model.     

Production rate control of an unreliable manufacturing cell with adjustable capacity

This article addresses the production control problem of an adjustable capacity unreliable manufacturing cell responding to a single product type demand. The manufacturing cell is composed of an unreliable machine, called the ‘central machine’. Due to availability fluctuations, the central machine may fall short of meeting the long-term demand rate. In order to quickly adjust the production capacity and thus meet the demand, a reserve machine is called upon in support if the finished product inventory level drops below a specific threshold. Such a machine involves higher production costs compared with the central one. This article aims to determine the optimal production control policy for the involved machines in order to minimise production, inventory and backlog costs over an infinite horizon. This article proposes a continuous dynamic programming formulation of the problem and adopted a numerical scheme to solve the optimality conditions equations. The optimal production policy is shown to be described by a state dependent hedging point policy (SDHPP). To determine the optimal control policy parameters, an experimental approach based on design of experiments, simulation modelling, and response surface methodology is proposed. Several sensitivity analyses have been carried out and have shown the robust behaviour of the developed policy facing expected variations of the system parameters. The results also show that the proposed SDHPP policy outperforms classical stand-by and parallel machines based control policies. The usefulness of the proposed approach is outlined for more complex situations where the system must deal with non-exponential failure and repair time distributions.