1,720,981 research outputs found
Stratospheric platform applications: reduced cognitive load for multimedia and education
No full textThe proliferation of computing solutions in future communication networks leads to the occurrence of cognitive visual overstimulation (CVO). CVO occurrence arises in multimedia content editing and provisioning of Science, Technology, Engineering, and Mathematics (STEM) education. The presented research proposes a high-altitude platform-based architecture that enable multimedia content editing related to space themes, and insertion in the edge of space i.e., the stratosphere (space horizon) environment. The use of the proposed architecture in content editing and STEM education contexts reduces the CVO by an average of (22–84.1) % and (13.6–31.7) %, respectively. Investigations show that the proposed architecture reduces the latency by an average of 30.3%, and 49.4% considering individual, and multiple content access, respectively. The use of the proposed architecture also reduces the power consumption associated with multimedia content editing by (8.05–42.9) % on average
Network integrated power architecture for terrestrial and modular data center contexts
No full textThe transition to renewable energy is a strategy that has been recognized for future data centers seeking to limit environmental emissions. In addition, innovation has led data center operators to install high-capacity renewable energy farms. However, the energy outputs from these farms are not totally utilized during the epochs of low server utilization. The surplus energy can be used to operate modular data center systems experiencing a power deficit. The presented research proposes an architecture to use surplus power in terrestrial data centers is used to meet the power deficit in modular data center systems. Performance evaluation shows that the proposed mechanism increases the power available to the modular data center by 78.3%. In addition, the proposed mechanism increases the number of communication epochs for modular data centers by 49.7% on average
Architecture of renewable energy system via non-terrestrial communication nodes
No full textThe transition from non-renewable energy sources to green (renewable) energy sources result in challenges that lead to the occurrence of energy gaps at several epochs. Energy gaps occur when the power output from renewable energy sources is insufficient to meet the load demand of retiring non-renewable energy sources. This results in undesirable load-shedding events. The presented research addresses this challenge by proposing new renewable energy sources that have not received sufficient consideration. Two energy sources have been motivated by advances in communication and computing networks in the aspects of underwater data centers and stratosphere-based data centers. The research presents an architecture and mechanism enabling these communication nodes to enable electricity contribution to the grid. Performance evaluation shows that the use of the proposed mechanism reduces the energy gap by at least 1.97% and at most 36.6% on average
Interference protection of radio astronomy services using cognitive radio spectrum sharing models
No full textTCP Stratos for stratosphere based computing platforms
No full textStratosphere computing platforms (SCPs) benefit from free cooling but face challenges necessitating transmission control protocol (TCP) re-design. The redesign should be considered due to stratospheric gravity waves (SGWs), and sudden stratospheric warming (SSWs). SGWs, and SSWs disturb the wireless channel during SCPs packet communications. SCP packet transmission can be done using existing TCP variants at the expense of high packet loss as existing TCP variants do not consider SGWs, and SSWs. TCP variants designed for satellite links are not suitable as they do not explicitly consider the SSW, and SGW. Moreover, the use of SCPs in future internet is at a nascent stage. The presented research proposes a new TCP variant i.e., TCP Stratos. TCP Stratos incorporates a parameter transfer mechanism and comprises loss-based; and delay-based components. However, its window evolution considers the occurrence of SSWs, and SGWs. The performance benefit of the proposed approach is evaluated via MATLAB numerical simulation. MATLAB simulation has been used because of the consideration of the stratosphere. The modelling of the stratosphere in this case is challenging for conventional tools and frameworks. Performance evaluation shows that using TCP Stratos instead of existing TCP variants and improved TCP variants reduces the packet loss rate by an average of (7.1–23.1) % and (3.8–12.8) %, respectively. The throughput is enhanced by an average of (20.5–53)%, and (40.9–70)% when TCP Stratos is used instead of existing TCP variant and modified TCP variant, respectively
Efficient spectrum-handoff schemes for cognitive radio networks
Get PDFRadio spectrum access is important for terrestrial wireless networks, commercial earth observations and terrestrial radio astronomy observations. The services offered by terrestrial wireless networks, commercial earth observations and terrestrial radio astronomy observations have evolved due to technological advances. They are expected to meet increasing users' demands which will require more spectrum. The increasing demand for high throughput by users necessitates allocating additional spectrum to terrestrial wireless networks. Terrestrial radio astronomy observations s require additional bandwidth to observe more spectral windows. Commercial earth observation requires more spectrum for enhanced transmission of earth observation data. The evolution of terrestrial wireless networks, commercial earth observations and terrestrial radio astronomy observations leads to the emergence of new interference scenarios. For instance, terrestrial wireless networks pose interference risks to mobile ground stations; while inter-satellite links can interfere with terrestrial radio astronomy observations. Terrestrial wireless networks, commercial earth observations and terrestrial radio astronomy observations also require mechanisms that will enhance the performance of their users. This thesis proposes a framework that prevents interference between terrestrial wireless networks, commercial earth observations and terrestrial radio astronomy observations when they co-exist; and enhance the performance of their users. The framework uses the cognitive radio; because it is capable of multi-context operation. In the thesis, two interference avoidance mechanisms are presented. The first mechanism prevents interference between terrestrial radio astronomy observations and inter-satellite links. The second mechanism prevent interference between terrestrial wireless networks and the commercial earth observation ground segment. The first interference reductionmechanism determines the inter-satellite link transmission duration. Analysis shows that interference-free inter-satellite links transmission is achievable during terrestrial radio astronomy observation switching for up to 50.7 seconds. The second mechanism enables the mobile ground station, with a trained neural network, to predict the terrestrial wireless network channel idle state. The prediction of the TWN channel idle state prevents interference between the terrestrial wireless network and the mobile ground station. Simulation shows that incorporating prediction in the mobile ground station enhances uplink throughput by 40.6% and reduces latency by 18.6%. In addition, the thesis also presents mechanisms to enhance the performance of the users in terrestrial wireless network, commercial earth observations and terrestrial radio astronomy observations. The thesis presents mechanisms that enhance user performance in homogeneous and heterogeneous terrestrial wireless networks. Mechanisms that enhance the performance of LTE-Advanced users with learning diversity are also presented. Furthermore, a future commercial earth observation network model that increases the accessible earth climatic data is presented. The performance of terrestrial radio astronomy observation users is enhanced by presenting mechanisms that improve angular resolution, power efficiency and reduce infrastructure costs
Nuclear resilient and redundant compute and communication integrated network
No full textFuture communication networks use computing platforms i.e., data centers for enabling content access. The operation of data centers is evolving to meet new requirements such as reducing the operating cost. The use of data centers is recognized to have significant challenges due to high operating costs. The high operating costs arises due to the necessity of data center cooling. The cooling costs can be reduced by siting data centers in the underwater environment. In the underwater environment, data centers are cooled by freely available cold water. However, siting data centers in the underwater environment exposes them to risk from other underwater applications. The use of underwater data centers is susceptible to service loss due to the launch of missiles from submarines in defense applications. Underwater data centers are susceptible to service loss from the launch of missiles from submarines. Hence, it is necessary to design a network architecture that ensures continued service delivery when nuclear attacks occur. The presented research proposes a novel network architecture enabling service continuity in the underwater data center. The proposed architecture incorporates resiliency and comprises terrestrial and non–terrestrial data centers. The proposed network architecture incorporates redundancy and utilizes terrestrial and non-terrestrial data centers. In addition, the research presents a protocol enabling co-existence between underwater data centers and missile launching submarines used in defence applications. The research formulates and evaluates the operational duration, number of packets forwarding paths, and computing resource utilization as the metrics. Performance evaluation shows that the proposed network architecture improves the operational duration and computing resource utilization by an average of (27.7–71.5)% and (23.5–44.2)%, respectively. Furthermore, the proposed network architecture enables the realization of more resilient paths. The use of more resilient paths enhances packet transmission. Evaluation shows that the proposed network architecture enhances the number of resilient packets forwarding paths by (18.2–57.4)% on average
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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