A Sensitive Triple-Band Rectifier for Energy Harvesting Applications

(c) 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.[EN] This paper presents a novel sensitive triple-band power rectifier for RF energy harvesting systems. The proposed rectifier can simultaneously harvest RF energy from GSM-900, GSM-1800, and Wi-Fi-2450 bands at relatively low and medium ambient power densities. Previously, a few multi-band rectennas have been reached a stable conversion efficiency overall frequency bands of interest because of the nonlinearity and the distinct input impedance of the rectifying circuit at these frequencies. The originality of this paper is on the improved impedance matching technique that enhances the efficiency and performance of the rectifier. The proposed high-efficiency triple-band rectifier consists of three parallel branches. Each branch comprises an input matching circuit designed to provide maximum RF power transferred to rectifying diodes, a single voltage doubler using Schottky diode HSMS-2852, and a DC-pass filter to smooth the DC output voltage. A prototype of the proposed rectifier circuit is fabricated and tested to verify its performance against the simulation results. With an optimum load resistance of 3.8 k at -10 dBm input power level, the measured RF to DC conversion efficiency achieves 33.7%, 21.8%, and 20% at 0.9, 1.8 and 2.45 GHz respectively. The efficiency is above 46.5 % overall bands of interest under 0 dBm input powerThis work was supported in part by the EMMAG Program, 2014, funded by the European Commission.Tafekirt, H.; Pelegri-Sebastia, J.; Bouajaj, A.; Reda, BM. (2020). A Sensitive Triple-Band Rectifier for Energy Harvesting Applications. IEEE Access. 8:73659-73664. https://doi.org/10.1109/ACCESS.2020.2986797S7365973664

The distribution of power in post‐ Gadafi Libya: A 'Sociology of Power' analysis

El presente trabajo aborda la situación en la Libia post Gadafi. Tras el comienzo de las Primaveras Árabes surgieron una serie de actores con el objetivo común de derrocar al régimen. La caída y muerte de Gadafi, supuso el inicio de una nueva etapa marcada por la aparición de milicias que frustraron la transición democrática, y acentuaron la lucha por los recursos de poder, siendo el petróleo el más importante. El objetivo principal de este artículo radica en analizar cómo y por qué se produjo la diversificación del poder que ha tenido a Libia envuelta en una situación de caos por más de seis añosThis paper deals with the situation in Libya post Gadafi. After the Arab Spring different actors appeared with a common goal: to overthrow the regime. The death of Gadafi was a new stage characterized by the appearance of militias that frustrated the democratic transition and accentuated the struggle for power resources, with oil being the most important. The main objective of the investigation is to analyze how and why the diversification of the power took place, being Libya literally in shambles since the

Comparison of energy transfer between Terbium and Ytterbium ions in glass and glass ceramic: Application in photovoltaic

The structural and optical properties of thin layers based on 70%SiO 2 –30%HfO 2 doped with different concentra- tion of rare earth ions (terbium and ytterbium) have been studied with a view to integrating them in a photovoltaic cell as a spectral conversion layer in order to improve its efficiency, by using down-conversion process. These thin films were synthesized by using sol gel technique and deposited on the pure silica substrate by dip-coating method. The DC layer can be placed on the front side of a solar cell and can enhance the current by converting ultraviolet (UV) photons into a large number of visible photons. In present study two series of samples are compared, the first series corresponds to samples treated at 900 °C (glass- S) while the second series concerns samples treated at 1000 °C (glass-ceramic- SC). These series are based on 70SiO 2 –30HfO 2 activated by different molar concentrations of rare earths [Tb + Yb]/[Si + Hf] = 7%, 9%, 12%, 15%, 17%, 19% and 21%. Photoluminescence results of reference samples (without Yb 3 + ) showed an emission from 5 D 4 to 7 F J ( J = 3, 4, 5, 6) level characteristic transitions of Tb 3 + , with a maximum peak in the green centered at 543.5 nm cor- responding to the 5 D 4 →7 F 5 transition. For the co-doped samples a clear NIR PL emission around 980 nm was detected, due to the 2 F 5/2 →2 F 7/2 transition of Yb 3 + ions. From luminescence decay curves of Tb 3 + maximum emission peak ( 7 F 5 →5 D 4 transition at 543.5 nm) we have identified the energy transfer efficiency. The quantum efficiency increases by increasing the total [Tb + Yb] concentration. The most significant yield was achieved with [Tb + Yb] = 19%, the maximum quantum transfer efficiency obtained was 190% for glass-ceramic samples and 161% for glassy one

Evaluation of the cost of cervical cancer at the National Institute of Oncology, Rabat

Introduction: The Cervical Cancer (CC) is one of the heavy and costly diseases for the population and the health system. We want to know through this study, the first in Morocco, the annual cost of the treatment of this disease at the National Institute of Oncology (NIO) in Rabat, we also want to explore the possibility of flat-rate management of this disease in order to standardize medical practices and improve reimbursement by health insurance funds. Methods: 550 patients were treated for their cervical cancer in the Rabat's NIO. Data of all of medical and surgical services offered to patients were collected from the NIO registry. The cost of care was assessed using the method of micro-costing. We will focus to the total direct cost of all the services lavished to patients in NIO. Results: The global cost was about US$1,429,673 with an average estimated at US$ 2,599 ± US$ 839. Radiotherapy accounts for 55% of total costs, followed by brachytherapy (27%) and surgery (7%). This three services plus chemotherapy influence the overall cost of care (p <0.001). Other services (radiology, laboratory tests and consultations) represent only 10%. The overall cost is influenced by the stage of the disease, this cost decreased significantly evolving in the stage of CC (p <0.001). Conclusion: The standardization of medical practices is essential to the equity and efficiency in access to care. The flat-rate or lump sum by stage of disease is possible and interesting for standardizing medical practices and improving the services of the health insurance plan.Pan African Medical Journal 2016; 2

A Review on Antibacterial Activity of Nanoparticles

The increasing resistance of bacteria to antibiotic agents is a main global public health problem. The use of nanoparticles is one of the promising ways to overcome microbial resistance to antimicrobial agents. Metal nanoparticles are increasingly used to target bacterial strains. Advances in nanotechnology, in particular the ability to synthesize nanoparticles of specific size and shape, are likely to lead to the development of new antibacterial agents. The antibacterial activities of nanoparticles are largely influenced by their sizes and large surface area/mass ratio. The antibacterial mechanisms of nanoparticles are poorly understood, but the currently accepted mechanisms include oxidative stress induction, metal ion release, and non-oxidative mechanisms. In this review, we have focused on the antibacterial activity of nanoparticles and their main mechanisms of action against bacteria. We also discuss the recent therapeutic strategies to control bacterial virulence and biofilm formation by targeting quorum sensing in bacteria without impeding bacterial growth. On the other hand, we reviewed five widely used databases of nanoparticles, aiming to provide the nanoscience community with valuable information about the specific content and function of these databases

Silver doping of silica-hafnia waveguides containing Tb3+/Yb3+ rare earths for downconversion in PV solar cells

The aim of this paper is to study the possibility to obtain an efficient downconverting waveguide which combines the quantum cutting properties of Tb3+/Yb3+ codoped materials with the optical sensitizing effects provided by silver doping. The preparation of 70SiO(2)-30HfO(2) glass and glass-ceramic waveguides by sol-gel route, followed by Ag doping by immersion in molten salt bath is reported. The films were subsequently annealed in air to induce the migration and/or aggregation of the metal ions. Results of compositional and optical characterization are given, providing evidence for the successful introduction of Ag in the films, while the photoluminescence emission is strongly dependent on the annealing conditions. These films could find potential applications as downshifting layers to increase the efficiency of PV solar cells. (C) 2016 Elsevier B.V. All rights reserved

Tb3+/Yb3+ codoped silica-hafnia glass and glass-ceramic waveguides to improve the efficiency of photovoltaic solar cells

In this paper we present the investigation of the energy transfer efficiency between Tb3+ and Yb3+ ions in silica-hafnia waveguides. Cooperative energy transfer between these two ions allows to cut one 488 nm photon in two 980 nm photons and could have important applications in improving the performance of photovoltaic solar cells. Previous works revealed that for a given concentration of donors (Tb3+, increasing the number of acceptors (Yb3+) located near to the Tb3+ ion can increase the Tb-Yb transfer probability. However, when increasing the density of active ions, some detrimental effects due to cross-relaxation mechanisms become relevant. On the basis of this observation the sample doping was chosen keeping constant the molar ratio [Yb]/[Tb] = 4 and the total rare earths contents were [Tb + Yb]/[Si + Hf] = 5%, 7%, 9%. The choice of the matrix is another crucial point to obtain an efficient down conversion processes with rare earth ions. To this respect a 70SiO(2)-30HfO(2) waveguide composition was chosen. The comparison between the glass and the glass-ceramic structures demonstrated that the latter is more efficient since it combines the good optical properties of glasses with the optimal spectroscopic properties of crystals activated by luminescent species. A maximum transfer efficiency of 55% was found for the highest rare earth doping concentration

SLOPE STABILITY ANALYSIS USING GIS

An analysis of slope stability using Geographic Information System (GIS) is presented in this paper. The methodology is based on the calculation of the safety factor in 2D and 3D using ArcGis. Hovland's Method in 3D and 2D were used in the stability analysis of the slope located at the 34 kilometer point (K.P.34) on the highway in the North of Morocco connecting Tangier to Ksar Sghir. Results shows that the safety factors obtained in 3D are always higher than those obtained in 2D and the slope becomes unstable when the water table level is less than 1 m

Site distribution and thermalization effects in europium-doped silica glasses

For the no-phonon transition 5D0 → 7F0 of Eu3+ in glasses, obtained by sol-gel route, emission and absorption at low temperature are not resonant. This effect is interpreted by a redistribution of the excitation energy among the different environment for the Eu3+ ion. A simple model is used to interpret the temperature evolution of the emission spectra. A good agreement is obtained with experimental results. The experimental emission spectra are simulated using the Boltzmann law and the experimental excitation spectra. The mechanism of redistribution is a phonon-assisted energy transfer process. This is confirmed by temperature dependance of decays and time resolved emission measurements

Optical spectroscopy of Eu3+ ion as a tool for the study of dehydration process in silica gels

The structural modification induced by dehydration in optical silica gel has been studied using the spectroscopy of Eu3+ ion. The samples, doped with molar ratio Eu/Si = 0.01:1, were heated for 48 hours at different temperatures from 60 °C to 200 °C. Information on the dinamical properties of the local environment of the Eu3+ were obtained both by fluorescence and excitation measurements at T=11 K. The analysis of the 5D0 → 7F0 transition appears of particular relevance in this study, because the transition is between J=0 states and does not present internal structure. Its inhomogeneous linewidth gives a measure of the energy distribution of the different Eu3+ sites. Site selection spectroscopy was performed by exciting into the 5D1 state. Three different sets of sites were found. The phonon sidebands of the 5D0 ← F0 and 5D1 ← 7F0 transitions were observed in the excitation spectra