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.
enjoyed the process of the development of higher education institutions attention of most countries of the world and to reconsider its objectives and programs and administrative and organizational structures, and it was the most important development of the application of Quality Assurance and Accreditation Standards (QAAS) tools, as the aim of these tools to the application of advanced with a far-reaching impact on all of the disciplines in the organization methods education that contribute, and plays a performance audit an important role in verifying the extent to which carried out these institutions activities or programs effectively and efficiently, economic, There are a number of objectives for the search of the most important attem
... Show MoreThe purpose of this paper is to build a simulation model by using HEC-RAS software to simulate the reality of water movement in the main river of Basra City (South of Iraq) which is known as Siraji-Khoura River. The main objective of the simulation is to detect areas where the water cycle is interrupted in some stations of the river stream, as this river has become an outlet for the disposal of sewage, leading to pollution and causing weakness in some sections of the river & obstructing the water cycle that takes place between this river and Shatt al – Arab river. A field survey data of the river and its banks were adopted to derive the grades, longitudinal and cross sections of the river, these data included three-dimensional coordinates
... Show MoreThis study is prospective in nature, It consider
110 patients with vertigo who were assessed
between April and December 2010 at E.N.T out
patient department of otolarygiology, in Al
Diwania teaching hospital, in Diwania city,
Iraq. The study is designed to assess the
incidence of vestibular and non vestibular
vertigo and their association with
tinnitus,hearing loss,migraine in Young adult
and elderly.All patients were assessed by
questionary method and by pure tone
Audiometry.
Results: the incidence of vestibular vertigo was
69.1% while non vestibular vertigo is 30.9 %,
vestibular vertigo was inversely related to the
age while non vestibular vertigo directly related
to the age
The percen
Unstable angina pectoris often leads to acute myocardial infarction. Since uric acid is thought to be risk factor for cardiovascular disease and considered a major antioxidant in human blood .The level of uric acid and lipid peroxidation in the sera of patients with unstable angina and myocardial infarction were measured and compared to the healthy individuals. Twenty-nine patients with unstable angina and twenty-nine patients with myocardial infarction were studied and compared to twenty-five healthy individuals. Uric acid was measured by using Human Kit. Malondialdelyde (MDA) a lipid peroxidation marker, was measured by thiobarbituric acid method .Significant elevation of uric acid and MDA were observed in the sera of pati
... Show MoreA simple, economical and selective method employing ion pair dispersive liquid−liquid microextraction (DLLME) coupled with spectrophotometric determination of carbamazepine (CBZ) in pharmaceutical preparations and biological samples was developed. The method is based on reduction of Mo(VI) to Mo(V) using a combination of ammonium thiocyanate and ascorbic acid in acidic medium to form a red binary Mo(V) thiocyanate complex. After addition of CBZ to the complex, extraction of the formed CBZ−Mo(V)−(SCN)6 was performed using a mixture of methylene chloride and methanol. Then, the measurement of target complex was performed at the wavelength of 470 nm. The important extraction parameters affecting the efficiency of DLLME were studied and o
... Show MorePurpose: the purpose of study is estimate the Risk premium, Interest rate, Inflation and FDI in the through of Coronavirus in the MENA countries. Theoretical framework: The theoretical framework included the study of the main variables, which are risk premium, interest rate, inflation, and foreign direct investment during the Corona virus pandemic. Design/methodology/approach: Concentrating on “COVID-19”, as an effective factor on the Foreign direct investment (FDI), I employ data of “MENA (Middle East and Northern Africa)” countries from 2000 to 2021 to investigate the impact of COVID-19, financial and macroeconomic indicators on FDI relying on the analytic research approach of Static panel data regression, includ
... Show MoreObjective: The current study aimed identifying the impact of rehabilitative exercises combined with ultrasonic waves on reducing pain in people with carpal tunnel compression and determining how these activities affect range of motion of the upper limb for those suffering from carpal tunnel compression. Research methodology: With pre- and post-tests, the researchers employed the experimental method in the form of two equal groups, the experimental and the control. The scientific community and sample are among the priorities that fall on the researcher, so The scientific community is determined by those suffering from carpal tunnel compression, numbering (14) patients. (12) Patients were approved and two were excluded from the resear
... Show MoreThis work is devoted to the modeling of streamer discharge, propagation in liquid dielectrics (water) gap using the bubble theory. This of the electrical discharge (streamer) propagating within a dielectric liquid subjected to a divergent electric field, using finite element method (in two dimensions). Solution of Laplace's equation governs the voltage and electric field distributions within the configuration, the electrode configuration a point (pin) - plane configuration, the plasma channels were followed, step to step. The results show that, the electrical discharge (streamer) indicates the breakdown voltage required for a 3mm atmospheric pressure dielectric liquid gap as 13 kV. Also, the electric potential and field distributions sho
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