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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 Jan 01 2003
Journal Name
Ibn Al-haitham . J . For Pure & Appl Sci
Synthesis and characterization of new orttho - amino phenyl thio derivatives and their complexes
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Two ligand ortho-amino phenyl thio benzyl (L1) and 1,3 bis (ortho - amino phenyl thio ) acetone (L2) and their complexes have been prepared and characterized . The L1 ligand is lossing phenyl group on complexcation and forming 1,2 bis (ortho - amino phenyl thio ) ethane L3 and this tetrahedrally coordinated to the metal ion ( M+2 = Ni , Cu , Cd ) and octahedrally coordinated with mercury and cobalt ions , while the ligand L2 is behave as tridentate ligand forming octahedrally around chrome metal ion . Structural , diagnosis were established by i.r , Uv- visible , conductivity elemental analysis and (mass spectra , H nmr spectra for( L1 , L2 ) .

Publication Date
Mon Feb 04 2019
Journal Name
Journal Of The College Of Education For Women
Relationship phonetics and musicology at the Ikhwan Al- Safa and at al – Farabi
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Phonetics has close relevance with Musicology; in this study I decided explaining the interlinkages and harmony between Phonetics and Musicology. Linguists preceded philosophers in an attempt to link Phonetics with Musicology; the 1st serious attempt to link Phonetics with Musicology was done by Ibn Jeny (Dead 392 IC), but the real attempt is found with Farabi through his book under title Al Musiqa Al Kabeer, he defined music and link it with tune and relation between melody and tone, This is the same as pointed out by Ikhwan Al Safa who followed the doctrine of al-Farabi, their attention was with music and link it with phoneme, as they made music independent science, and they created special mathematics rules for it. Melody in music can

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Publication Date
Wed Feb 01 2023
Journal Name
Journal Of Engineering
Comparison of Groundwater Quality and Quantity between Al-Rahbah and Al-Haydariyah Regions
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This study focused on two areas in AL-Najaf city, AL-Ruhbah and Al-Haydariyah regions because of the importance and widespread use of groundwater in these areas. The two areas were compared quantitatively and qualitatively. For the quantitative approach, the GMS software was used in conjunction with the GIS software to simulate the groundwater flow behavior. The solid model for both areas was created, the geological formation was determined, and the hydraulic properties were identified using GMS software. To test the quantity of groundwater in both areas, the wells have been redistributed to a distance of 2000 m between them, and a period of 1000 days was chosen. When a discharge of 10 l/s and operation times of 4, 8, an

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Publication Date
Mon Mar 15 2021
Journal Name
Egyptian Journal Of Chemistry
Synthesis and Characterization of some Tetrazole Derivatives and Evaluation of their Biological Activity
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Publication Date
Sat Nov 04 2023
Journal Name
Russian Journal Of General Chemistry
Synthesis and Characterization of Metals Complexes with Uracil and Uracil Derivatives (A Review)
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Previous studies on the synthesis and characterization of metal chelates with uracil by elemental analysis, conductivity, IR, UV-Vis, NMR spectroscopy, and thermal analysis were covered in this review article. Reviewing these studies, we found that uracil can be coordinated through the electron pair on the N1, N3, O2, or O4 atoms. If the uracil was a mono-dentate ligand, it will be coordinated by one of the following atoms: N1, N3 or O2. But if the uracil was bi-dentate ligand, it will be coordinated by atoms N1 and O2, N3 and O2 or N3 and O4. However, when uracil forms complexes in the form of polymers, coordination occurs through the following atoms: N1 and N3 or N1 and O4.

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Publication Date
Wed Jan 01 2025
Journal Name
Medical Journal Of Babylon
Students’ Knowledge and Attitude about Hepatitis B and C Viruses in Baghdad University
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Abstract<sec> <title>Introduction:

Hepatitis B and C is a serious global public health problem that causes chronic liver disease and accelerates high risk of death from cirrhosis of the liver and liver cancer.

Objectives:

To determine the knowledge and attitude of nonmedical students at Baghdad University toward HBV and HCV infections and to find out the relationship between demographic characteristics.

Materials and Methods:

The study w

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Publication Date
Thu Jul 05 2018
Journal Name
Eurasip Journal On Wireless Communications And Networking
Positioning and guiding educational robots by using fingerprints of WiFi and RFID array
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Publication Date
Sat Mar 01 2025
Journal Name
Results In Engineering
Advancing asphalt binder performance through nanomaterial and polymer modification: Experimental and statistical insights
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Publication Date
Tue Nov 01 2022
Journal Name
Chemical Methodologies
Synthesis and Characterization of New Substituted Coumarin Derivatives and Study Their Biological Activity
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New substituted coumarins derivatives were synthesized by using nitration reaction to produce different nitro coumarin isomers which were separated from these isomers by using different solvent, and the reduction of nitro compounds was done to give corresponding amino coumarins. Temperature and reaction time of reaction were very important factors in determining the most productive nitro isotopes. A low temperature for three hours was sufficient to give a high product of a compound 6-nitro coumarin while increasing the temperature for a period of twenty-four hours that gave a high product of 8-nitro-coumarin. The synthesized compounds were confirmed by FT-IR,1 H-NMR, and13 C-NMR spectroscopy and all final compounds were tested for their ant

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Publication Date
Sat Apr 01 2023
Journal Name
Russian Journal Of General Chemistry
Synthesis and Characterization of Metals Complexes with Uracil and Uracil Derivatives (A Review)
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