Détermination des perturbations induites aux extrémités d’une ligne blindée soumise à une excitation ponctuelle de courant

This article allows the determination of the induced perturbations at the ends of the coaxial line in wide frequency band enough. The perturbation source is a current direct point injection into the cable screen in any position. For this, we have applied the theory of the state variables, with foundation of the quasi-TEM approximation, in order to simulate the coaxial line above a ground level that has a finished conductivity. This allows us to supply the current and voltage expressions at the ends of the line as their analytic forms for any conditions of charge. Next, the elaborate objective is to verify experimentally on concrete applications if the test obtained results confirm the theoretical expectations supplied by calculation code finalizing.     

A scalable interest-oriented peer-to-peer pub/sub network

There has been a big challenge in structured peer-to-peer overlay network research area. Generally, a structured overlay network involves nodes evenly or based on their resource availabilities, and gathers nodes?? resources to achieve some bigger tasks. The challenge here is to gather resources based on nodes?? interests, and only interested nodes are involved in a certain task. Toward this challenge, we propose a new scheme to a peer-to-peer publish/subscribe network. Publish/subscribe represents a new paradigm for distributed content delivery. It provides an alternative to address-based communication due to its ability to decouple communication between the source and the destination. We propose a Bloom filter based mapping scheme to map IDs to nodes?? interests in addition to new interest proximity metric to forward events and to build nodes?? routing tables. We also propose a new approach called ??shared interest approach?? for network discovery. To evaluate the algorithms proposed in this work, we conducted simulations in both static and dynamic settings, and found a low false positive rate. We also discuss about a well-known application called Twitter, and show how our scheme would work in a real environment.     

Towards an immortal operating system in virtual environments

Many OS crashes are caused by bugs in kernel extensions or device drivers while the OS itself may have been tested rigorously. To make an OS immortal we must resurrect the OS from these crashes. We present a novel OS-hypervisor infrastructure that allows automated and transparent OS crash diagnosis and recovery in a virtual environment. This infrastructure eliminates the need for reboots or checkpoint-restart mechanisms, which require preserving the states of critical applications before the crash happens and also require extensive modifications to those applications. At the core of our approach is a small hidden OS-repair-image that is dynamically created from the healthy running OS instance. When an OS crashes, the hypervisor dynamically loads this repair-image to perform diagnosis and repair. One way of repair we have experimented with, is to quarantine the offending process and resume the running of the fixed OS automatically without a reboot. Experimental evaluations demonstrated that it takes less than 3 s to recover from an OS crash. This approach can significantly reduce the downtime and maintenance costs in data centers, and is the first design and implementation of an OS-hypervisor combo capable of automatically resurrecting a crashed commercial server-OS. In addition to online diagnosis and recovery, this infrastructure can also be used for offline diagnosis and can be incorporated into the technical support tools of the OS vendor. Additionally, we have used parts of this infrastructure to speed-up the diagnosis of AIX OS-crashes for the IBM technical support teams.     

Gamma irradiation-induced modifications in the structural,thermal, and optical properties of polyvinyl alcohol-polyethylene glycol/cobalt oxide nanocomposite films

Cobalt oxide nanoparticles (NPs) are highly consistent dispersed into the blend polymers rather than other NPs. Also, the ability of polyvinyl alcohol-polyethylene glycol (PVA-PEG) to form homogenous blend attained it essential characteristics that allow it to be suitable candidate for numerous industrial applications. Thus in the present work, Co₃O₄ nano-oxide, was synthesized by the sol-gel procedure and PVA-PEG/Co₃O₄ nanocomposite NCP films were synthesized by the casting technique. Samples from the synthesized NCP were exposed to γ doses between 20 and 230 kGy. The induced alterations in the synthesized NCP due to gamma irradiation have been illustrated using X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential thermal analysis (DTA), Fourier transform infrared (FTIR), and UV spectroscopes. Further, Color divergence between the blank and the irradiated films has been estimated. Gamma doses between 60 and 230 kGy lead to the prevalence of intermolecular crosslinking, which enhances the disordered phase. This is reflected in a rise in the degradation temperature values from 225°C to 236°C indicating an improvement in the thermostability of the NCP samples. Moreover, the γ-radiation induces defects that split the ordered portion, reducing T_m from 238°C to 229°C. In addition, the band gap decreases from 5.24 to 4.61 eV with increasing the γ doses to 230 kGy, signifying disorder character. Finally, the NCP samples showed a color change by γ radiation, as ΔE raised with increasing dose. The resultant improvements in the optical properties of the NCP samples allow it to be used in optoelectronic and dosimetric applications.     

Expressions approchées aux basses et aux hautes fréquences des tensions induites de mode commun aux extrémités d’une ligne blindée soumise à une injection ponctuelle de courant

With reference to a preceding paper, this paper allows, in a first step, to determine, at low and high frequencies, approached expressions of the induced common mode voltages at the extremities of a shielded line influenced by a punctual current injection along the shield. These expressions are established for the case of a helicoidal screen with four different schemes of earth connections at the extremities. In a second step, the correction function, i.e. the ratio between the exact and approached solution, and the limit of validity of this latter at high frequencies are addressed.     

On IEC 61850 communication networks in smart grids system: Methodology of implementation and performances analysis on an experimental platform

The increasing installation of distributed energy resources during the last years has led to a fundamental change in the power system structure. As a consequence, utility operators are faced with new challenges in grid planning and control. The consideration of smart grids show promising results in increasing the hosting capacity for distributed and renewable resources. Standardized automation, control, and communication systems are important keys to realize such intelligent methods. This paper focuses on a deployment methodology of IEC 61850 on an experimental platform for smart grid system. We were interested in evaluating the performance of the GOOSE communication. A standard-based communication approach for distributed energy resources is introduced and implemented. It uses the IEC 61850 interoperability approach as well as the GOOSE communication for distributed automation. The implementation methodology is provided to handle the hierarchical architecture of distributed control applications. In order to show the advantages of the proposed methodology, a combined analytical and experimental approach is demonstrated for evaluation of GOOSE communication performances.     

Optical and structural properties of polyvinyl alcohol loaded with different concentrations of lignosulfonate

Polyvinyl alcohol/lignosulfonate (PVA/LS) composite films have been prepared using casting technique. The effect of lignosulfonate concentrations (0.001, 0.005, 0.01, 0.05, 0.1 and 0.5 wt %) on the optical and structural properties of polyvinyl alcohol (PVA) has been investigated using UV–vis spectroscopy and X‐ray diffraction. The results indicate that, the addition of LS led to a more compact structure of PVA, which resulted in an increase in its refractive index and amorphous phase. This was associated with a reduction in the optical energy gap that could be attributed to the increase in disorder structural of the composites. Moreover, the transmittance of PVA/LS composite film decreased with the increase of LS doping concentrations onto the PVA matrix. The results reflect the proper dispersion of LS in the PVA matrix that causes a strong intermolecular interaction between LS and PVA suggesting strong hydrogen bond formation between the hydroxyl group in PVA chains and the outer site groups of LS. Further, the transmission of the samples in the wavelength range of 370–780 nm, as well as any color changes, was studied. The color intensity ΔE, which is the color difference between the pure PVA sample and those with different LS concentration, increases with increasing the LS content and was accompanied by an increase in the yellow and red color components. J. VINYL ADDIT. TECHNOL., 25:85–90, 2019. © 2018 Society of Plastics Engineers     

Alumina supported cobalt–palladium catalysts for the reduction of NO by methane in stationary sources

In order to improve a “Three Function Catalysts Model”, the present paper deals with alumina based catalysts containing cobalt and palladium for the NO reduction by methane.

The deNO_x temperature window was estimated by adsorption and subsequent desorption of NO in lean conditions. Two NO_x desorption peaks were detected for both catalysts. For Pd(0.63)Co(0.58)/Al₂O₃, the two desorption peaks appeared at 205 and 423 °C, whereas for Pd(0.14)Co(0.57)/Al₂O₃, the maxima desorption temperature peaks were at 205 and 487 °C. In addition, NO oxidation was also studied to evaluate the catalyst first function. It was found that, the oxidation begins on Co–Pd/Al₂O₃ around 250 °C. On Pd(0.63)Co(0.58)/Al₂O₃, 8% of deNO_x were found in the range of the second NO_x desorption peak temperature (410 °C). During TPSR, C_xH_yO_z species such as formaldehyde were detected. These oxygenate species are the reactive intermediate for deNO_x by methane.     

A study on the optimum insulation thicknesses of building walls with respect to different zones in Morocco

Morocco has very limited indigenous energy resources; consequently, with the increase in energy consumption over the last years, studies focusing on energy saving as well as usage of sustainable energy resources have accelerated. However, in Morocco the buildings have an important part in the energy consumption; therefore, the most logical solution is energy saving by using thermal insulation. For this purpose, in this study, six cities, namely Agadir, Tangier, Fez, Ifran, Marrakech and Errachidia are selected to represent the six zones of Morocco. Using the life-cycle cost analysis method, the optimum insulation thicknesses as well as energy savings and payback periods for electricity tariff and three different types of insulation material have been determined.