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.
Administrative leaders conserned to understand the challenges which are faced their organizations and try to assimilate and adapt with the extent that achieves to it efficiency and effective- ess, and standing face to face to faceing any challenge.that threaten it’s existence thro- ugh using modern inputs reached to that level of these challenges and applied the study on a sample deliberate random from teaching hospitals of the Directorate General for Health Baghdad Karkh, and the Directorate General for Health Baghdad Rusafa and the City of Medicine , The importance of t
... Show MoreThe technical development has significant effects on the mediator Alcinmatugrave, and TV originated mainly based on technical, with the development and the continuation of these technologies and the enormous impact on the level of the television picture, initially dramas in recent times approaching in the aesthetic composition of the film thanks to the employment of modern digital technologies, Montag was not only one of the cinematic elements that went into television thanks to technical developments analogue and digital, and which added the possibility of large processors in the picture, high-definition digital cameras that have led to dispense often for artificial lighting intensive imaging light available, as these cameras have helpe
... Show MoreThe present study was designed to synthesize a number of new Ceftriaxone derivatives by its involvement with a series of different amines, through the chemical derivatization of its 2-aminothiazolyl- group into an amide with chloroacetyl chloride, which on further conjugation with these selected amines will produce compounds with pharmacological effects that may extend the antimicrobial activity of the parent compound depending on the nature of these moieties.
Ceftriaxone was first equipped with a spacer arm (linker) by the action of chloroacetyl chloride in aqueous medium and then further reacted with seven different aliphatic and aromatic amines which resulted in the production of the aimed final target products. The syntheses
... Show MoreTheatrical production mechanisms were determined according to the extents of the theatrical performance, the directing plan, and the ideas that the theatrical performance seeks to convey to the audience. Accordingly, theatrical production mechanisms differ between one theatrical performance and another according to the requirements of each of them and the surrounding circumstances that accompany the production of theatrical performance, and in order to search for production mechanisms and their repercussions on the show. Theatrical The current research was divided into four chapters, namely (Chapter One - Methodology), which identified the research problem in the following question: What are the production mechanisms and their implicatio
... Show MoreThe useful of remote sensing techniques in Environmental Engineering and another science is to save time, Coast and efforts, also to collect more accurate information under monitoring mechanism. In this research a number of statistical models were used for determining the best relationships between each water quality parameter and the mean reflectance values generated for different channels of radiometer operate simulated to the thematic Mappar satellite image. Among these models are the regression models which enable us to as certain and utilize a relation between a variable of interest. Called a dependent variable; and one or more independent variables
The poetic text, being an artistic product, is achieved during the moment of inspiration. However, this inspiration does not come from a vacuum. Rather, it needs a good environment capable of pushing the poetic text to the surface after its formation in the poet's mind, with the images and ideas it contains, expressed in his own language and style. Distinguished, and we must not overlook that language is not just words and meanings, but rather those feelings and emotions that are the essence of creativity (()), including musical, sentimental and imaginative aspects with colors of suggestion and symbols (()), because the poetic language is distinguished from others in that it (Symbols for psychological states are the substance of thought)
... Show MoreThe aim of the research is to identify the losses resulting from the terrorist operations and then find a proposed accounting treatment for the losses resulting from the terrorist operations and to indicate their impact on disclosure in the financial statements by reviewing the international standards and local rules and the unified accounting system and not dealing with these losses, Of the financial statements and therefore adversely affect the accounting disclosure as well as the weak commitment of economic units to apply the requirements of accounting measurement and disclosure of losses of terrorist operations in a manner consistent with local and international standards to achieve the Reliability in the financial statement.
This paper focuses on the concept of cognition and its clarification in the light of Islamic epistemology. Knowledge passes through two essential parts: conception and assent. Conception explains simple knowledge, while assent explains knowledge involving a judgment. The paper proceeded with the identification of the problem of relationship blurring between cognition and knowledge. The external and inner senses have explained the relationship between the stages of knowledge and cognition. The external senses receive stimuli and form primary conceptions. These conceptions transfer to the first part of the inner senses, which is common sense; it collects the sensations and transmits them to pictorial power. Secondary conceptions are f
... Show MoreIn this study, polymeric ultrafiltration (UF) membranes were prepared by phase inversion method to obtain both antibacterial and organic antifouling properties. The membranes were cast from a solution of polyvinylidene fluoride (PVDF) and formative silver (Ag) nanoparticles were successfully immobilized on a polymer. This was done using a solvent N, N-dimethylformamide (DMF) which is a solvent for the PVDF polymer meanwhile it is a reducing agent for silver ion. The effect of silver nanoparticles additives on the performance of polymeric ultrafiltration membrane was verified. Chemical composition and morphology of the surfaces of the membranes were characterized by Fourier transform infrared spectroscopy
... Show MoreThe dental amalgam of radioactive materials in the restoration of teeth because of its readily adaptable to existing materials in the oral cavity in addition to mechanical properties such as hardness mechanical resistance Alndgat and others in this study were prepared Almlagm used Guy dental restoration of silver alloy tin plus some elements to improve the characteristicsmechanical such as copper, zinc or indium in addition to mercury