Reduction by CO-CO2 and cracking of iron ore sinters,part 1: kinetics

A synthetic sinter has been prepared, and compared to an industrial ore, in order to obtain a better understanding of the mechanism and circumstances of degradation by cracking, during the low-temperature reduction of hematite to magnetite, in the upper part of the blast furnace. In the present paper, some kinetic data on the reduction by CO₂ are reported. It appears that the Shrinking Core Model correctly applies in all conditions, even at low temperatures where there is significant cracking. The chemical rate constants and nucleation frequencies are derived and compared with our previous data obtained with natural isolated hematite single crystals. It is also confirmed that the reaction is first order versus carbon monoxide.     

Implementation of a Formal Security Policy Refinement Process in WBEM Architecture

Security mechanisms enforcement consists in configuring devices with the aim that they cooperate and guarantee the defined security goals. In the network context, this task is complex due to the number, the nature, and the interdependencies of the devices to consider. In previous papers, we have proposed a formal framework that focuses on network security information management refinement. The framework includes three abstraction levels: the network security objectives, the network security tactics, and the network security device configurations. The information models of each abstraction level (consistency, correctness and feasibility) are formally specified and analyzed. In this paper we present the integration of this formal refinement process in the WBEM initiative in order to provide a management infrastructure that guarantees the validity of the deployed security configurations.     

Relay node selection scheme and deep sleep period for power management in energy-harvesting wireless sensor networks

This paper presents Relay node selection scheme and Deep sleep period for power management in Energy Harvesting Wireless Sensor Networks (RD-EHWSN), a new energy-saving scheme founded on asynchronous duty cycling. RD-EHWSN reduces sensor node energy consumption and guarantees equilibrium energy use between sensor nodes in WSN with the energy harvesting capacity by adjusting these sensor nodes duty cycles more drastically and deeply by according to the estimated value of its residual energy on the basis of future-presented harvested energy, and this is done through the use of a new proposed energy threshold policy. RD-EHWSN also grips the benefit of transmitter initiated using the low power listening (LPL) technique with short preamble messages and uses a new relay node selection procedure to achieve the load balancing in WSN. We implemented RD-EHWSN by using OMNeT++/MiXiM. For evaluation, we compared it with PS-EHWSN, under multiple concurrent multihop traffic flows scenarios and scenarios in which nodes can harvest different energy harvesting rate. In all experiments, RD-EHWSN significantly outperformed the PS-EHWSN scheme; the results of simulation demonstrate that our scheme enhances the general yielding of WSN thru lessening the energy consumption and the mean latency, as well as raising the packet delivery ratio and the throughput. Moreover, RD-EHWSN improves the WSN lifetime and ensures it operates in good condition in the case where the energy harvesting rate is lower by comparing it with the PS-EHWSN scheme.     

Oil-entrapped ranitidine HCl beads heal peptic ulcers via local and systemic mechanisms

Objective: Oral gastroretentive system is one of the site-specific drug delivery system, which is designed to be retained in upper GIT for a prolonged time. Ranitidine hydrochloride (RHCl), which is used frequently in treatment of peptic ulcer, is a suitable candidate for gastroretentive delivery systems. Dependently, floating oil-entrapped alginate beads of RHCl were developed and evaluated as an approach to site-specific delivery avoiding colonic degradation and enhancing both bioavailability and the proposed local effect.

Methods: Different formulations of floating beads were suggested and randomized using 2⁴ full factorial design. Optimized formulation was subjected for in vivo studies to measure the oral bioavailability and the healing effect of induced peptic ulcers.

Results: Beads size ranged from 1.32 to 2.3?mm. All beads revealed excellent floating capabilities. Optimum formulation (F12) has entrapment efficiency of 70%, drug loading of 7% and 71% RHCl released after 6?h. SEM of F12 shows a grossly spherical structure with presence of oil droplets distributed throughout structure. AUC obtained from F12 was nonsignificantly higher than that of a commercial tablet. Signs of ulcer healing appeared clearly with F12 through appearance of granulation tissue, collagen fibers and newly formed blood vessels. Healing rate and extent obtained with a commercial tablet were less than F12. Quantitative analysis confirmed histopathological findings.

Conclusion: Floating oil-entrapped beads are a promising approach for RHCl delivery to remain in stomach for a longer time ensuring site-specific delivery and consequently, enhancing local healing effect of peptic ulcers.     

Serviceability design for geosynthetic reinforced column supported embankments

In recent years, geosynthetic reinforced column supported embankments (GRCSEs) have become an increasingly popular design solution for road and rail infrastructure constructed over soft soil sites. However, the serviceability behaviour and deformation that often govern the suitability of their design is not well understood. This is due, in part, to the difficulties in describing the arching stress development in the load transfer platform (LTP). This paper highlights the need for coupled arching stress-deformation models to describe accurately serviceability behaviour. This approach contrasts the widely adopted two-step design approach, which uses limit-equilibrium models that de-couple the arching stress-deformation relationship to describe ultimate limit state behaviour. Using an analytical example, an arching stress/deformation model and an empirical relationship (developed by others) relating base LTP settlement to surface settlement, the relationship between serviceability behaviour and soft soil parameters is highlighted and the conditions leading to progressive collapse in GRCSEs are described. The approach presented provides a means to predict serviceability behaviour, and at the same time, raises questions about the long-term performance and the manner in which acceptable performance has been achieved in the short-term in several field case studies. In particular, those constructed at, or near, a minimum embankment height.     

EEM-EHWSN: Enhanced Energy Management Scheme in Energy Harvesting Wireless Sensor Networks

Wireless Networks - Energy conservation is the main major issue in wireless sensor networks (WSNs). Indeed, recharging energy sources in WSNs is often too costly, difficult and sometimes...     

Consequences of TiO2 doping on the optical properties of porous silica layers coated on silica optical fibers

The paper deals with the investigation of optical properties of porous silica and TiOTi chains – doped porous silica layers coated on silica optical fibers. The porous layers composed of dried gels have been prepared by the sol–gel method from alkoxides. The refractive indices and optical attenuation of the layers have been determined from the measured angular distributions of the output optical power. For this purpose, a model based on geometrical optics has been developed. The interaction of the porous layers with benzene, toluene, xylene and hexane has been investigated by measuring the changes of the output optical power induced by the effect of vapors of the hydrocarbons in air. On the basis of these measurements, the porosity of the layer, partition coefficients and equilibrium adsorption constants of the hydrocarbons have been estimated. The measured decrease of the optical power for the aromatic hydrocarbons and the increase of the output power for the aliphatic hydrocarbon have been explained on the basis of the developed model.