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.
Social graphic design is the design that realizes the role and responsibility of the designer in society, and the use of graphic design in bringing about social change, especially as it is a professional contribution that plays an important role in the behavioral development of societies, and through the above, the researcher found a logical justification for his research problem, which is summarized by the following question: (What is the concept of Social Graphic Design and its implications in the fight against drug abuse)
While the two objectives of the research were identified in defining the social graphic design and its effect on combating drug abuse, and the theoretical framework was divided into two topics, the first study dea
The other day in the Holy Quran and the four Gospels
The global oil market is one of the most important markets in the world and occupies especially for countries consuming and producing countries, and the status of understanding of the mechanism for determining prices in the market help to stand on many factors affecting oil demand and supply of oil and geopolitical factors, climate and alternative sources of energy .. etc. factors, and that the main objective of the research is to study the causes and results left behind by the oil price shocks in the world market, and the movement of these factors be through a cycle of energy that explain the strength of competition between these factors and their effects on prices, when demand increases evolution Large image leads to significan
... Show MoreBackground and objective: Viral Hepatitis Type B&C is serious public health challenge throughout the world.Hepatitis B and C viruses still remain to be the major causes of chronic hepatitis.It is estimated that around 350-400 million people in the world are chronic carriers of HBV, which represents approximately 7% of the total populationwhereas infection with HCV is found in approximately 3% of the world population, which represents 160 million people. Hepatitis B infection has a wide range of seroprevalence in the Mediterranean countries ranging from intermediate (=>2% ) to high prevalence ( =>7%). World Health Organization estimated a prevalence rate for HCV infection of about 4.6% in Eastern Mediterranean in 1999. During the eightieths
... Show MoreColour is part of human environ ment and is present almost every
where in cluding clothes.
Clours have positive and negative effects on the person's psychology.
Thus we can ask the following question: what are the clours preffered
by the Iraqi females in the university level and what is the lightness and purity
of these colours and their effect on their psychology?
In this research we included 563 Baghdad university female student for
the year 2005-2006.
The question are included anumber of qnestions that gave answers to
the research main objectives.
Forty six Iraqi women with PCOS were involved in this study . They were treated with metformin alone and with antioxidant agents (vitamin E or C).It was found that all patients who treated with metformin or with combination of metformin with antioxidant agents showed significant decrease in hirsutism score. The treatment of metformin with antioxidant agents is of great benefit in treatment of hirsutism in PCOS due to that there was no worsening effect after treatment. This may indicate that antioxidant agents may participate in alleviation of hirsutism so it can be said that oxidative stress may play an important role in developing of hirsutism in PCOS.
Chlopheniramine maleate ( CPM ) , is one of the H- receptor antagonist , widely used in allergic diseases ,like skin rash and pruritis .CPM 3%w/w was successfully loaded in 2%w/w sodium alginate (SA) as a gel base , and to be considered as a selected formula .It was found that the diffusion of CPM through the skin of albino rat was increased as the concentration of CPM increased from 2 %w/w sodium alginate , More
... Show MoreThe current research studies the innovative thinking system in the field of the interior design, and the extent of the possibility of activating its work mechanisms as a strategy for the redesigning principle according the variables of the contemporary social thinking. The research aims at revealing the nature of the thinking criteria and requirements that provide strategic values that guide the interior designer and the architect to organize the mechanism the act of designing. It also contributes in dealing with the design product through activating its ability in innovation and redesigning.
The research consists of the concept of innovation, the&nbs
... Show MoreBeen investigating a Pfyrus antigen hepatitis pattern J and Virus-positive rubella viral hepatitis antibodies pattern J. declaration followed by the percentage rate-positive patients of measles Allmana antibodies