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Multi-Channel Distributed DSA Networks: Connectivity and Rendezvous Tradeoffs
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In this paper, we investigate and characterize the effects of multi-channel and rendezvous protocols on the connectivity of dynamic spectrum access networks using percolation theory. 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-channel, 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 protocols, 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 represent the multiple channels as parallel edges in a graph and build a multi-layered graph (MLG) in R2. In order to study the connectivity, we show how percolation occurs in the MLG by coupling it with a typical discrete percolation. Using a Boolean model and the MLG, we study both cases of primaries' absence and presence. For both cases, we define and characterize connectivity of the secondary network in terms of the available number of channels, deployment densities, number of simultaneous transmissions per node, and communication range. When primary users are absent, we derive the critical number of channels which maintains supercriticality 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. For each region we show the requirement and the outcome of using either type of rendezvous techniques. Moreover, we find the tradeoff between deployment-density versus rendezvous probability which results in a connected network. Our results can be used to decide on the goodness of any channel rendezvous algorithm by computing the expected resultant connectivity. They also provide a guideline for achieving connectivity using minimal resources.

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Publication Date
Wed Mar 01 2017
Journal Name
Nano Hybrids And Composites
Synthesis of ZnS QDs with Different Values of pH and White Light Generation from Fabrication of TPD: PMMA/ZnS Hybrid Devices
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Quantum dots (QDs) of zinc sulfide (ZnS) was prepared by chemical reaction with different potential of hydrogen (pH) and used to fabricate organic quantum dot hybrid junction device. The optical properties of QDs were characterized by ultraviolet-visible (UV-Vis.) and photoluminescence (PL) spectrometer. The results show that the prepared QDs were nanocrystalline with defects formation. The energy gap (Eg)calculated from PL were 3.64, 3.53 and 3.35 eV for pH=8, 10 and 12 respectively. This decreasing of energy gaps is results of the effect the pH solution increases, which in turn leads to the shifted of the PL spectrum toward red shifted, which makes the energy bands at surface states are shallow ban

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Publication Date
Sat Jun 28 2025
Journal Name
Journal Of Physical Education
Artificial intelligence is employed in studying the relationship between some physical measurements and the accuracy to the young goalkeepers in football
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Physical measurements are one of the basic factors that affect the performance of the goalkeeper, especially when confronting fixed kicks that require special skills such as the reaction and accuracy in concentration, and with technological development artificial intelligence has become an effective tool for analyzing mathematical data that is difficult to discover in traditional methods The study aims to employ techniques Artificial intelligence to study the relationship between physical measurements and the accuracy of confronting the fixed kicks of goalkeepers in football. This study will contribute to providing a deeper understanding of physical factors that affect the performance of goalkeepers, in addition to designing dedicat

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Publication Date
Sun Sep 28 2025
Journal Name
Journal Of Physical Education
Analysis of Training Load During the Special Preparation and Competition Periods Using Physiological Indicators in U19 Football Players via Smart Bracelet
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The importance of the study lies in highlighting the role of smartwatches as a modern tool for analyzing training load based on functional indicators, such as heart rate and calorie consumption. This allows coaches to monitor individual players’ responses during different training periods, helping to improve physical performance efficiency and reduce the risk of overload-induced fatigue. The study aimed to analyze calorie consumption at different heart rate levels between the special preparation and competition periods for youth football players, with the goal of determining the effect of physiological adaptation on energy efficiency. To achieve this objective, the researcher adopted the descriptive method due to its suitability f

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Publication Date
Thu Sep 30 2021
Journal Name
Journal Of Economics And Administrative Sciences
Human Resource Management and its Impact on the Level of Job Performance: An Analytical Research in the Iraqi Ministry of Interior
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        The current research aims to highlight the role of human resource management with its practices (human resource planning, selection and placement, training and development, performance evaluation, compensation, and incentives) in raising the level of individuals' performance and its dimensions (task performance, contextual performance, unproductive work behavior, and adaptive performance) by explaining the research problem, which can be limited to the low level of performance of individuals, where the researchers use the descriptive analytical approach and the SPSS program in the practical aspect of the research community represented by the general manager and his assistant

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Publication Date
Tue Sep 15 2020
Journal Name
Al-academy
Forbidden Montage and the transition Technique in one-snapshot Movies 1917 Film- A model: محمد عبد الجبار كاظم-عذراء محمد حسن
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  Starting from the term (forbidden montage) initiated by the French critic (Andre Bazin) as a method of processing the movies that depend on (mise en scene) achieved by the action of the camera and its ability to photograph and employ the depth of the field, in addition to the possibility of free movement without interruption in the filming environment in order to avoid montage as much as possible (the montage that distorts focus and distracts attention and moves away from realism, which is the most important theoretical pillar of Bazin in photography). The pursuit was behind a cinema that depicts its topics in one integrated snapshot with all its details thus approximating reality without any interference of montage. Our study sta

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Publication Date
Mon Feb 13 2023
Journal Name
Journal Of Educational And Psychological Researches
Evaluation of English Language Textbooks for Fifth and Sixth Graders Based on the American Council Criteria for Teaching Foreign Languages (ACTFL)
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Abstract

This study aims to identify the extent to which the criteria of the American Council for Teaching Foreign Languages (ACTFL) are included in the English language books for the fifth and sixth graders. To achieve the objective of the study, a content analysis card was prepared, where the classification of language proficiencies was divided into five main levels (beginner, intermediate, advanced, superior, and distinguished) of the four language skills (listening, speaking, reading, and writing), The content analysis card consisted of (89) indicators distributed at the four levels of language skills as follows: Listening (17), speaking (33), reading (15), and writing (26). The study sample consisted of Engl

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Publication Date
Sun May 23 2021
Journal Name
Egyptian Journal Of Chemistry
Thermodynamic study of adsorption of a mixture of Nolvadex and nanoparticle ferric oxide that prepared on the surface of activated charcoal
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Publication Date
Sun Dec 01 2024
Journal Name
Russian Journal Of General Chemistry
Synthesis, Characterization, and Biological Evaluation for New Derivatives Based on 2Сhloro-N-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]acetamide
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Publication Date
Fri Mar 15 2024
Journal Name
Journal Of Baghdad College Of Dentistry
Assessment of the correlation between the tensile and diametrical compression strengths of 3D-printed denture base resin reinforced with ZrO2 nanoparticles
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Background: The mechanical properties of 3D-printed denture base resins are crucial factors for determining the quality and performance of dentures inside a patient’s mouth. Tensile strength and diametral compressive strength are two properties that could play significant roles in assessing the suitability of a material. Although they measure different aspects of material behavior, a conceptual link exists between them in terms of overall material strength and resilience. Aim: This study aims to investigate the correlation between tensile strength and diametral compressive strength after incorporating 2% ZrO2 nanoparticles (NPs) by weight into 3D-printed denture base resin. Methods: A total of 40 specimens (20 dumbbell-shaped and

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Publication Date
Thu Oct 31 2019
Journal Name
Al-kindy College Medical Journal
Quality of Primary Care Center Referral Letters and Feedback Reports among Sample of PHCCs in Baghdad /Al-Rusafa Health Directorate During2015
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Background:The referral system constitutes a key element of health system. Effective referral system between different levels of health care delivery represents a cornerstone in addressing patients’ health needs.

Objectives:To assess the referral system Baghdad/ Al-Rusafa Health Directorate by evaluation the referral pattern and identify the quality of the referral letters and feedback reports.

Type of the study: This cross-sectional study .

Methodology : It was conducted in5PHCC in from 1st July 2015 - 31st December 2015 at Bagdad/Al-Rusafa health directorate. The study population (sampled population) included all ref

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