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.
Background: Background: Helicobacter pylori is an important gastrointestinal bacteria related to the development of superficial atrophic gastritis, peptic ulcer and gastric cancer. Human leukocyte antigens (HLA) may play an important roles in host immune responses to H pylori antigens.
Aim of the study: to investigate the association between HLA-DRB1 genotypes and superficial gastritis with H. pylori infection in an Iraqi patients.
Patients and methods: Sixty patients with superficial gastritis and 100 individuals with apparently normal results after endoscopic examination were recruited from Al-Kindy Teaching Hospital - G
... Show MoreThe research problem boils question is there in Riyadh organizational climate that enables them to do their work properly and whether there are differences between the government and private Riyadh depending on the organizational climate has sought Find measure: 1 regulatory climate for kindergarten 2. The difference between government and private Riyadh depending on the organizational climate. Limited research on the (200) parameter of the Riyadh government and private parameters for the year (20,142,015) In order to achieve the research objectives the researchers built a regulatory climate in accordance with the scientific steps to build a psychological scales measure After the formulation of climate regulation paragraphs of the (30) p
... Show MoreThe current study included a detail morphological study of all parts of the two species of the genus Tropaeolum L. (Tropaeolumceae) cultivated in different gardens, the roots, stems, leaves, flowers and fruit were studied in detail, also the pollen grains were studied, and there are photographs for all that parts were putted. A specimens of that taxa were studied in some Iraqi herbaria. The study found that there are many characters were used in differentiation of two species under study.
The field experiment was conducted with the aim of developing and testing an automatic sprayer for agricultural spray experiments and studying the effect of spray pressure, spray speed and spray height on the spraying process. The effects of the major spraying factors (pressure, speed, and height) on the spraying performance of the automatic sprayer were studied. This study included several traits: First - the drop sizes - Second - the penetration of the spray into the vegetation cover - Third, the spray wasted. The results showed: - First: - Increase in coverage percentage when using the first speed, 2 km / h, which amounted to 26.85%. An increment in the spraying penetration of the vegetation cover was observed at the second speed
... Show MorePDBNRSIA Asst, International Journal of Research in Social Sciences and Humanities, 2018
The present paper respects 'inversion' as a habit of arranging the language of modern English and Arabic poetry . Inversion is a significant phenomenon generally in modern literature and particularly in poetry that it treats poetic text as it is a violator to the ordinary text. The paper displays the common patterns and functions of inversion which are spotted in modern English and Arabic poetry in order to show aspects of similarities and differences in both languages. It concludes that inversion is most commonly used in English and Arabic poetry in which it may both satisfy the demands of sound correspondence and emphasis. English and Arabic poetic languages vary in extant to their manipulation of inverted styles as they show changeable f
... Show MoreThe anatomical features of Agave americana L. leaf have been described, transverse sections of the leaf have been examined, the epidermis is single-layered on both surfaces, the stomata are sunken and mesophyll is (2-3) layers of parenchyma cells, vascular bundles are collateral type. The pollen of A. americana was studied. The observation was made with L.M. (Light microscope) and S.E.M. (Scanning electron microscope) to determine the significance of pollen features as taxonomic characters. The pollen was monades, homopolar, monosulcate, and with large size, subprolate in shape from P/E ratio (Polar axis/ Equatorial diameter) and furrow length and width, exine thickness and ornamentation.
In this study the prevalence of acute, sub-acute and chronic toxoplasmosis were monitored in a group of Iraqi pregnant women according to the anti-T.gondii antibodies (IgG and IgM), as well as the levels of both progesterone and estrogen hormones were measured using mini-VIDAS®technique. This study demonstrated that there was high prevalence of chronic toxoplasmosis (31.70%) when it compared with acute and sub-acute type, results also showed that the acute toxoplasmosis always related with low concentration of both progesterone and estrogen which were (5.35 ± 7.15 ng/ml) and (70.66 ± 51.08 pg/ml) respectively