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Multi-Channel Distributed DSA Networks: Connectivity and Rendezvous Tradeoffs
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In this paper, we investigate and characterize the effects of multi-channel and rendezvous protocols on the connectivity of dynamic spectrum access networks using percolation theory. 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-channel, 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 protocols, 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 represent the multiple channels as parallel edges in a graph and build a multi-layered graph (MLG) in R2. In order to study the connectivity, we show how percolation occurs in the MLG by coupling it with a typical discrete percolation. Using a Boolean model and the MLG, we study both cases of primaries' absence and presence. For both cases, we define and characterize connectivity of the secondary network in terms of the available number of channels, deployment densities, number of simultaneous transmissions per node, and communication range. When primary users are absent, we derive the critical number of channels which maintains supercriticality 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. For each region we show the requirement and the outcome of using either type of rendezvous techniques. Moreover, we find the tradeoff between deployment-density versus rendezvous probability which results in a connected network. Our results can be used to decide on the goodness of any channel rendezvous algorithm by computing the expected resultant connectivity. They also provide a guideline for achieving connectivity using minimal resources.

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Publication Date
Wed Apr 22 2026
Journal Name
Environmental Earth Sciences
Transboundary hydrogeology and controlling factors of euphrates water chemistry: Insights from hydrochemistry, stable isotopes, and residence times in Syria and Western Iraq
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Arid and semi-arid climates are critical for water security in sustainable river systems. The Euphrates River in western Iraq has been increasingly stressed by both geogenic and anthropogenic factors. This study analyzed hydro-geochemical processes, recharge dynamics, and groundwater flow modeling in western Iraq. Additionally, stable isotope tracing (δ¹⁸O, Cl⁻) integrated with hydro-chemical parameters was used to assess water quality and river-aquifer connectivity in both Syria and western Iraq. A total of 144 groundwater samples were collected annually across 12 stations in western Iraq. Surface water and groundwater data were collected from previous studies at 13 stations in Syria. Results revealed slightly alkaline freshwater con

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Publication Date
Sun Mar 06 2016
Journal Name
Baghdad Science Journal
Comparison Between Conventional and Microwave Methods For Extraction Pectin and Degree of Esterification from Orange (Citrus sinesis) and Grapefruit (Citrus paradisi) Peels
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In this study Microwave and conventional methods have been used to extract and estimate pectin and its degree of esterification from dried grapefruit and orange peels. Acidified solution water with nitric acid in pH (1.5) was used. In conventional method, different temperature degrees for extraction pectin from grape fruit and orange(85 ,90 , 95 and 100?C) for 1 h were used The results showed grapefruit peels contained 12.82, 17.05, 18.47, 15.89% respectively, while the corresponding values were 5.96, 6.74, 7.41 and 8.00 %, respectively in orange peels. In microwave method, times were 90, 100, 110 and 120 seconds. Grapefruit peels contain 13.86, 16.57, 18.69, and 17.87%, respectively, while the corresponding values were of 6.53, 6.68, 7.2

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Publication Date
Tue Nov 25 2025
Journal Name
Inorganic Chemistry Communications
Synthesis, spectroscopic and single-crystal analysis, and DFT studies of N₂O₂ diamine coordination complexes: solvent-driven geometry switching and NLO properties
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The design of coordination compounds with solvent-responsive optical properties remains a central challenge in molecular photonics. Here, we describe the synthesis and full characterisation of a symmetrical tetradentate diamine ligand, 3,3′-((1,2-phenylenebis(azanediyl))- bis(methanylylidene))bis(pentane-2,4-dione) (H₂L), and its neutral square-planar complexes [M(L)] (M(II) = Co, Ni, Cu). The Cu(II) complex crystallised as [Cu(L)]⋅0.5 (pyrazine), adopting a nearly square-planar geometry (τ₄ = 0.06) in the solid state, as confirmed by single-crystal X-ray diffraction. In DMSO solution, UV–Vis spectra revealed reversible axial coordination of two solvent molecules, driving a transformation to a distorted octahedral geometry. Struc

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Publication Date
Tue Feb 14 2017
Journal Name
مجلة كلية التربية للعلوم الصرفة ابن الهيثم
synthesis and characterization of New Bidentate schiff base Ligand Type(NO)Donor Atoms Derived from isatin and 3-Amino benzoic acid and Its complexes with Co(||),Cu(||),Cd(||)and Hg(||)Ions
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synthesis and characterization of New Bidentate schiff base Ligand Type(NO)Donor Atoms Derived from isatin and 3-Amino benzoic acid and Its complexes with Co(||),Cu(||),Cd(||)and Hg(||)Ions

Publication Date
Sun Sep 01 2024
Journal Name
Heliyon
Synthesis and characterization of some Metal ions complexes with mixed ligand of azo dye and Metformin and evaluation of its effectiveness on the growth of some pathogenic bacteria clinically isolated and study of its Toxicity on normal and cancerous Hepatocytes
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Publication Date
Sun Sep 01 2024
Journal Name
Heliyon
Synthesis and characterization of some Metal ions complexes with mixed ligand of azo dye and Metformin and evaluation of its effectiveness on the growth of some pathogenic bacteria clinically isolated and study of its Toxicity on normal and cancerous Hepatocytes
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Four metal compounds mixed ligand of azo dye ligand (L) and metformin.(Met) were produced at aquatic ethanol for (1:1:1) (M:L:Met). The prepared compounds were identified by utilizing atomic absorption flame, FT.IR and UV–Vis spectrum manners as well as conductivity mensuration. These compounds was assayed of the gained datum the octahedral geometry was proposed into whole prepared complexes.Also in this research was studied represented examining the antibacterial and antifungal impact of the azo dye ligand (L), metformin.(Met) and (Co,Ni, Cu and Cd complexes) on four types of pathogenic, clinically isolated bacteria that are resistant to antibiotic, like Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneu

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Publication Date
Mon Jan 01 2024
Journal Name
Heliyon
Synthesis and Characterization of Some Metal Ions Complexes with Mixed Ligand of Azo Dye and Metformin and Evaluation of its Effectiveness on the Growth of Some Pathogenic Bacteria Clinically Isolated and Study of its Toxicity on Normal and Cancerous Hepatocytes
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Publication Date
Tue May 09 2017
Journal Name
Iraqi Journal Of Market Research And Consumer Protection
TIME MANAGEMENT AND WORK PRESSURE AND THEIR RELATIONSHIP TO ADMINISTRATIVE LEADERSHIP/ A CASE STUDY AT THE HIGHER INSTITUTE FOR ADMINISTRATIVE DEVELOPMENT OF SECURITY AND ADMINISRATIVE: TIME MANAGEMENT AND WORK PRESSURE AND THEIR RELATIONSHIP TO ADMINISTRATIVE LEADERSHIP/ A CASE STUDY AT THE HIGHER INSTITUTE FOR ADMINISTRATIVE DEVELOPMENT OF SECURITY AND ADMINISRATIVE
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The research aims to determine the strength of the relationship between time management and work pressure and administrative leadership, where he was taken a sample of (47) of the administrative leadership at the Higher Institute of security and administrative development in the Ministry of Interior was used questionnaire as a key tool in collecting data and information and analyzed the answers to the sample surveyed by using Statistical program (spss) in the arithmetic mean of the calculation and test (t) and the correlation coefficient, the research found the most important results: the existence of significant moral positive relationship between both time management and work pressure and administrative leadership, the leadership of th

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Publication Date
Sat Feb 02 2019
Journal Name
Journal Of The College Of Education For Women
The Balance and unbalance in alliance relations The Saudi Arabia and United State Relation as model: The Balance and unbalance in alliance relations The Saudi Arabia and United State Relation as model
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Abstract:
Saudi Arabia and United States long relation could present an important
subject to understand alliance kind in international relations types. We trying
in this study to diagnose and analyze the Saudi Arabia and United States
model to find balance and unbalance statues and its influence on the
directions of Saudi Arabia foreign policy positions.
We divided the study in two parts, each part have many sections. The
first part deal with the historian emergence of Saudi Arabia state and its
development in three stages including its foreign relations with regions and
international powers. While the second part was dedicated in analyzing and
understanding the mechanism and active facts that drawing the Sa

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Publication Date
Sun Jan 01 2012
Journal Name
Diyala Agricultural Sciences Journal (dasj)
(OLIGO-X) the effect of salinity of irrigation water and magnetisation and soaking Alalascorbek acid and extracted sea Your protected agriculture. DALIA in germination and growth of seedlings seeds of hybrid option
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