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Connectivity and rendezvous in distributed DSA networks
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In this paper, we use concepts and results from percolation theory to investigate and characterize the effects of multi-channels on the connectivity of Dynamic Spectrum Access networks. In particular, we focus on the scenario where the secondary nodes have plenty of vacant channels to choose from-a phenomenon which we define as channel abundance. To cope with the existence of multi-channels, we use two types of rendezvous protocols: naive ones which do not guarantee a common channel and advanced ones which do. We show that, with more channel abundance, even with the use of either type of rendezvous protocol, it becomes difficult for two nodes to agree on a common channel, thereby potentially remaining invisible to each other. We model this invisibility as a Poisson thinning process and show that invisibility is even more pronounced with channel abundance. Following the disk graph model, we define and characterize connectivity of the secondary network in terms of the available number of channels, deployment densities, number of transceivers per node, and communication range. When primary users are absent, we derive the critical number of channels which maintains super-criticality of the secondary network. When primary users are present, we characterize and analyze the connectivity for all the regions: channel abundance, optimal, and channel deprivation. Our results can be used to decide on the goodness of any channel rendezvous algorithm by computing the expected resultant connectivity.

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Publication Date
Wed Jul 02 2008
Journal Name
Iraqi Journal Of Science
Petrology, geochemistry and tectonic environment of the Shalair Metamorphhic Rock Group and Kater Rash Volcanic Group, Shalair Valley area, Northeastern Iraq
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Publication Date
Sun Dec 25 2022
Journal Name
International Journal Of Drug Delivery Technology
Green Synthesis of Silver Nanoparticles via Black and Green Tea and Study its Toxicity on few Vital Organs of Female Mice
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This study included synthesizing silver nanoparticles (AgNPs) in a green method using AgNO3 solution with glucose exposed to microwave radiation. The prepared NPs were also characterized using ultraviolet and visible (UV-vis) spectroscopy and scanning electron microscopy (SEM). The UV/vis spectroscopy confirmed the production of AgNPs, while SEM analysis showed that the typical spherical AgNPs were 30 nm and 50 nm in size for the NPs prepared using black tea (B) and green tea (G) as reducing agent, respectively. The changes in some of the biochemical parameters related to the liver and kidneys have been analyzed to evaluate the probable toxic effects of AgNPs. 40 adult male mice were included in this study. To assess the probable he

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Publication Date
Mon Feb 13 2023
Journal Name
Journal Of Educational And Psychological Researches
The Repercussions of the Corona Pandemic (Covid 19) and its Impact on the Educational and Psychological Function of the Omani Family:
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Abstract

This study aims to identify the repercussions of the Corona pandemic (Covid 19) and its impact on the educational and psychological functions of the Omani family from the point of view of a number of fathers and mothers. Drive for a group of fathers and mothers, some of whom work in the government sector and others are mothers enrolled in graduate studies programs at the university, their ages range between (30-50 years) totally (28) mothers and fathers: 22 mothers and 6 fathers. The results showed that the repercussions of the transformation of e-learning, home quarantine, social distancing, and the challenges associated with them were among the most frequent responses that posed a real challenge to the

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Publication Date
Wed Oct 02 2019
Journal Name
Biochem. Cell. Arch.
NEW MIXED LIGAND OF DITHIOCARBAMATE AND 8- HYDROXYQUINOLINE WITH SOME COMPLEXES OF SCHIFF BASE LIGAND : SYNTHESIS, SPECTRAL ANALYSIS AND BIOLOGICAL ACTIVITY
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The preparation, spectroscopic characterisation of complexes derived from the mixed ligands with CdII, ZnII and CoII metal ions with Schiff base, Dithiocarbamates (DTCs) and 8-Hydroxyquinoline are reported. The compounds that prepared have been defined via; chloride content, F.T-IR, UV-Vis 1H-NMR spectroscopy and C.H.N.S, as well as conductance and magnetic susceptibility.All data which collected from such methods specified complexes with 6 coordinates in solution and solid states. The biologicalactivity that is related to all the prepared compounds which were screened for their antimicrobial activitiesagainst (G+ and (G- )). The data that collected from biological activity indicate that complexes will have extra activity against such teste

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Publication Date
Fri Jun 28 2024
Journal Name
Curr Pharm Des
Synthesis, Characterization, and Antimicrobial Evaluation of Schiff base-mixed Ligand Complexes with Divalent Metal Ions Derived from Amoxicillin and Vanillin/Nicotinamide
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Publication Date
Wed Mar 01 2023
Journal Name
Civil Engineering And Architecture
The 20 Minutes Neighborhood between Planning and Reality: Analytical Study of Al-Jumhuriya District (District 838 and Part of District 840)
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Publication Date
Wed Oct 23 2024
Journal Name
Polymers
Improving the Mechanical, Thermoelectric Insulations, and Wettability Properties of Acrylic Polymers: Effect of Silica or Cement Nanoparticles Loading and Plasma Treatment
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The acrylic polymer composites in this study are made up of various weight ratios of cement or silica nanoparticles (1, 3, 5, and 10 wt%) using the casting method. The effects of doping ratio/type on mechanical, dielectric, thermal, and hydrophobic properties were investigated. Acrylic polymer composites containing 5 wt% cement or silica nanoparticles had the lowest abrasion wear rates and the highest shore-D hardness and impact strength. The increase in the inclusion of cement or silica nanoparticles enhanced surface roughness, water contact angle (WCA), and thermal insulation. Acrylic/cement composites demonstrated higher mechanical, electrical, and thermal insulation properties than acrylic/silica composites because of their lowe

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Publication Date
Mon May 22 2017
Journal Name
Ibn Al-haitham Journal For Pure And Applied Sciences
Univariate and Simplex Optimization for the Spectrophotometric Determination of Cimetidine and Erythromycin ethylsuccinate Drugs Using Bromothymol Blue Via Ion-Pair Formation
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    The ion-pair formation method has been applied for the spectrophotometric determination of Cimetidine and Erythromycin ethylsuccinate, in bulk samples and in dosage form. The methods are accurate, simple, rapid, inexpensive and sensitive depending on the extraction of the formed ion-pair with brompthymol blue (BTB) as a chromogenic reagent in chloroform, use phthalate buffer of pH 5.5 and 4.0 for Cimetidine and Erythromycin ethylsuccinate respectively.  The formed complexes show absorbance maxima at 427.5 nm and 414.5 nm for Cimetidine and Erythromycin ethylsuccinate respectively against reagent blank. The calibration graphs are linear in the ranges of 0.5-15 µg.mL-1 with detection limit of 0.222 µg.mL-1 for

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Publication Date
Wed Sep 14 2016
Journal Name
Journal Of Baghdad College Of Dentistry
Evaluation of Mechanical and Histological Significance of Nano Hydroxyapatite and Nano Zirconium Oxide Coating On the Osseointegration of CP Ti Implants
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Background: Dental implant considers a unique treatment option for the replacement of missing dentition. The new trend of implants is looking for materials which accelerate bone formation in bone implant interface and enhance osseointegration to provide immediate loading directly after placement and decrease the time period which is disturbs patients and uncomfortable. The aim of the study was to evaluate the effect of nano zirconium oxide (ZrO2) and nano hydroxyapatite (Hap) mixture coating of screw shaped commercially pure titanium (cpTi) implants on bond strength at the bone implant interface with torque removal test and histological analysis in comparison with non coated implants. Materials and methods: Forty screws were machined from c

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Publication Date
Mon Apr 24 2017
Journal Name
Ibn Al-haitham Journal For Pure And Applied Sciences
Effect of Annealing Temperatures on the Structural and Optical Properties of ZnO and ZnO:Al Thin Films Prepared By Thermal Evaporation Technique
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 We studied the changing of structural and optical properties of pure and Aluminum-doped ZnO thin films prepared by thermal evaporation technique on glass substrates at thickness (800±50)nm with changing of annealing temperatures ( 200,250,300 )℃ for one hour. The investigation of (XRD) indicates that the pure and doped ZnO thin films were polycrystalline of a hexagonal wurtzite structure with preferred orientation along (002) plane. The grain size was decreased with doping before annealing, but after annealing the grain size is increasing with the increase of annealing temperature for pure film whereas for the doped films with ratios 1 %, 2 % we found that the grain size is larger than that before annealing. The grain size

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