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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 13 2024
Journal Name
Journal Of Robotics
Hierarchical Stabilization and Tracking Control of a Flexible-Joint Bipedal Robot Based on Anti-Windup and Adaptive Approximation Control
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Bipedal robotic mechanisms are unstable due to the unilateral contact passive joint between the sole and the ground. Hierarchical control layers are crucial for creating walking patterns, stabilizing locomotion, and ensuring correct angular trajectories for bipedal joints due to the system’s various degrees of freedom. This work provides a hierarchical control scheme for a bipedal robot that focuses on balance (stabilization) and low-level tracking control while considering flexible joints. The stabilization control method uses the Newton–Euler formulation to establish a mathematical relationship between the zero-moment point (ZMP) and the center of mass (COM), resulting in highly nonlinear and coupled dynamic equations. Adaptiv

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Publication Date
Wed Sep 01 2010
Journal Name
Materials & Design
Influence of glass addition and sintering temperature on the structure, mechanical properties and dielectric strength of high-voltage insulators
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Publication Date
Thu Jul 16 2020
Journal Name
Polymer Bulletin
Fabrication and evaluation of structural, thermal, mechanical and optical behavior of epoxy–TEOS/MWCNTs composites for solar cell covering
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Publication Date
Mon Oct 22 2018
Journal Name
Journal Of Economics And Administrative Sciences
Measuring and analyzing the relationship between the volatility of US stock market indices and the volatility of oil prices
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The volatility of the financial markets and the oil market plays a major role in influencing macroeconomic activity, as well as the high interaction between the both markets and the remarkable sensitivity to their each other fluctuations which cause the undesirable impact on other economic sectors as an expected result due the mentioned interaction.

The study aimed to analyze the relationship between the volatility of the major US market indices represented by the DJIA index, S & P500, due to their comprehensiveness of the financial market, as they summarize the performance of the entire US market which is the largest economy in the world, as well as the difference in the calculation mechanism, and oi

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Publication Date
Fri Apr 04 2025
Journal Name
Al-rafidain Journal Of Medical Sciences ( Issn 2789-3219 )
Role of Kisspeptin-1 and Growth Differentiation Factor-15 in Iraqi Patients with Metastatic and Non-metastatic Colorectal Cancer
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Abstract Background: Colorectal cancer (CRC) is a leading cause of cancer mortality worldwide. Identifying novel biomarkers is critical for improving diagnosis, prognosis, and treatment strategies. This study investigates the serum levels of kisspeptin-1 (KISS1), its receptor (KISS1R), growth differentiation factor 15 (GDF15), and carcinoembryonic antigen (CEA) in Iraqi CRC patients. Objectives: Explore associations between serum levels of Kiss1, Kiss1R, GDF, and CEA and disease progression in Iraqi patients with CRC. Methods: A case-control study was conducted, including 72 CRC patients and 36 healthy controls. Patients were stratified into non-metastatic and metastatic groups. Serum biomarker levels were measured using enzyme-link

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Publication Date
Sun Apr 01 2018
Journal Name
Journal Of Educational And Psychological Researches
Problems and needs of Baghdad university students from perspective of college of political sciences and college of engineering’s students
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The current research aims to identify the problems and needs for both college of political science and college of engineering’s students. The sample was (100) male and female student. The results showed bunch of problems which could be organized descendingly, the scientific domain ranged between (2 - 2.42), the mean of the psychological domain was (2.85), the moral domain ranged between (2.2 – 2.28)m the problems of study earned (2.30), the material domain got (1.95), the medical and social domain obtained (1.925), and finally, the family domain received (1.887).

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Publication Date
Thu Dec 30 2021
Journal Name
College Of Islamic Sciences
Heralds of victory and empowerment of Islam From the texts and reality that the Noble Prophet (s) prophesied about
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Idea of ​​research

The global vision for the future of mankind and societies to achieve supremacy, empowerment and victory is limited to the sincerity of the sincere Islamic vision and its evidence, and this true vision is presented through the texts of the Noble Qur’an, the Sunnah of the Prophet and the concrete reality to achieve victory and empowerment of Islam, and does not respond by tracking the movement of history and its interventions.

The Islamic nation is a nation of survival and continuity with God’s promise and it needs to wake up and alert, and leadership that takes its hand into the path of victory and empowerment, and that this promise fulfills conditions of the most important of these is a promis

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Publication Date
Sat Dec 01 2018
Journal Name
Political Sciences Journal
A study in Tunisian - Iraqi Relations and its role in determining strategies for dealing with conflict and peace situations
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If the State attaches great importance to its foreign relations and intends to strengthen them in order to ensure the achievement of the highest national goals and interests. External relations between countries are one of the most prominent features of foreign policy, which depends on a combination of internal and external factors, the modern relations between Tunisia and Tunisia, which goes back to the pre-independence of Tunisia, when Iraq was a supporter of Tunisia's independence from France in the 1940s, Although these relations did not cause any disturbance by the two countries, but they remained weak relations did not develop in all areas except the sports and cultural field, which we will determine the reasons and the pos

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Publication Date
Sat Jul 01 2023
Journal Name
Journal Of Engineering
Comparative Reliability Analysis between Horizontal-Vertical-Diagonal Code and Code with Crosstalk Avoidance and Error Correction for NoC Interconnects
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Ensuring reliable data transmission in Network on Chip (NoC) is one of the most challenging tasks, especially in noisy environments. As crosstalk, interference, and radiation were increased with manufacturers' increasing tendency to reduce the area, increase the frequencies, and reduce the voltages.  So many Error Control Codes (ECC) were proposed with different error detection and correction capacities and various degrees of complexity. Code with Crosstalk Avoidance and Error Correction (CCAEC) for network-on-chip interconnects uses simple parity check bits as the main technique to get high error correction capacity. Per this work, this coding scheme corrects up to 12 random errors, representing a high correction capac

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Publication Date
Mon Jul 01 2013
Journal Name
Journal Of Saudi Chemical Society
Synthesis, characterization and in vitro antimicrobial activity of some novel 5-substituted Schiff and Mannich base of isatin derivatives
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With the aim of developing potential antimicrobials, a series of novel Ciprofloxacin methylene isatin derivatives incorporating different aromatic aldehydes were synthesized and characterized by FTIR, 1H NMR, Mass spectroscopy and bases of elemental analysis. In addition, the in vitro antibacterial and antifungal properties were tested against some human pathogenic microorganisms by employing the disc diffusion technique. A majority of compounds were showing activity against several of the microorganisms. The relationship between the functional group variation and the biological activity of the evaluated compounds is discussed. From comparisons of the compounds, 3c was determined to be the most active compound.

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