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

Cognitive radio technology is used to improve spectrum efficiency by having the cognitive radios act as secondary users to access primary frequency bands when they are not currently being used. In general conditions, cognitive secondary users are mobile nodes powered by battery and consuming power is one of the most important problem that facing cognitive networks; therefore, the power consumption is considered as a main constraint. In this paper, we study the performance of cognitive radio networks considering the sensing parameters as well as power constraint. The power constraint is integrated into the objective function named power efficiency which is a combination of the main system parameters of the cognitive network. We prove the exi

In the last two decades, networks had been changed according to the rapid changing in its requirements. The current Data Center Networks have large number of hosts (tens or thousands) with special needs of bandwidth as the cloud network and the multimedia content computing is increased. The conventional Data Center Networks (DCNs) are highlighted by the increased number of users and bandwidth requirements which in turn have many implementation limitations. The current networking devices with its control and forwarding planes coupling result in network architectures are not suitable for dynamic computing and storage needs. Software Defined networking (SDN) is introduced to change this notion of traditional networks by decoupling control and

This research aims to examine the effectiveness of a teaching strategy based on the cognitive model of Daniel in the development of achievement and the motivation of learning the school mathematics among the third intermediate grade students in the light of their study of "Systems of Linear Equations”. The research was conducted in the first semester (1439/1440AH), at Saeed Ibn Almosaieb Intermediate School, in Arar, Saudi Arabia. A quasi-experimental design has been used. In addition, a (pre & post) achievement test (20 Questions) and a (pre & post) scale of learning motivation to the school mathematics (25 Items) have been applied on two groups: a control group (31Students), and an experimental group (29 Students). The resear

The study aimed to identify the level of awareness of mental health among the students of the Universities of Palestine Technical and Jerusalem open in the city of Tulkarem from the perspective of the students and the population of the study ( 8091 ) students at the two universities , and selected intentional sample size was ( 445 ) students , and used the tool questionnaire to measure responses of subjects , and the results showed that there are differences depending on the variable sex and was in favor of females , and depending on the variable University , and was in favor of the Al-Quds Open / variable Study level for the benefit of students of second year , did not show statistical differences depending on the variables of c

The aim of the research is the knowing of the academic Scientific Journals of the colleges of University of Baghdad , through searching in the University of Baghdad website and the websites of colleges and thus studying the presentation of these journals in those website , and this is done by surfing the main pages of the websites for the colleges included in the research , and by analyzing the research made a menu for all the academic Scientific Journals for all institutes of the University of Baghdad , which simplifies the way for the researchers to publish these researches in the specific journals for their specialties .

The practice by the  administration of human resources  on effectiveness of organization  crisis as two knowledge fields , it were be until now as center for many studies, but the collect it, study of relation between them ,and The role of practices  by the  administration of human resources  on effectiveness of organization  crisis administration  were considered a new study and first according to the available and showing  studies at this field .

The problem of this research was specified by answer for the question that deal for size of consciousness at the ministry of interior for import of&nbs

This research seeks to unravel the components of the argumentative discourse in the Book ofʻRawdat al-MuhebbeenwaNozhatt al-Mushtaqeenʼ - The Garden of Lovers and the Promenade of Longing People – by Ibn Al-Qayyem Al-Jawziyah. This is because this book has a moderate discourse with a sound Islamic thought that is characterized by its sustainability, popularity, realism, and interaction with the successive developments of the new age. This reflects the intellectual maturity the composing process has reached in the philosophy of love and its educational bases in every place and time. To explore the componets, properties, and the working mechanisms of an argumentative discourse in Ibn Qayyem’s book, the present work has been conducted

Objectives of the study: The main objective of the study is to assess the prevalence of hypertension among
cardiac diseases patients and to fiend out relation ship between hypertension and cardiovascular diseases.
Methodology: A descriptive study, using interviewer and questionnaire technique was conducted on cardiac
diseases inpatients of clinic unite at Kirkuk and Azady hospitals from 17th ,June ,2012 to 1st, March , 2013.
Non – probability (purposive) sample of (148) adult patients, (81) females and (67) males with heart disease are
selected from inpatients of clinic unite at Kirkuk and Azady hospitals at kirkuk city. Questionnaire was
developed to assess the items which are related to heart disease patient's (Dise

Increasingly important public opinion polls steadily .... especially in electoral campaigns, sheds searchlight on the side of the US elections, in different time periods, and cited the words of experts and people involved in it, and reviews Find great development that took place in the polls and what could happen to this work It is important in the future. Display search for certain types of polls, dividing them on as stated by the experts in the United States... This division shows that the surveys of the most political processes and accuracy of information, and that their Money being made and companies specialized in the administration of this type of measuring public opinion ..... what is returned decision-making, for example, in conj