1,720,967 research outputs found
Location-free Semi-directional Flooding for On-demand Routing in Low-Rate Wireless Mesh Networks
No full textIn this paper, we propose a novel on-demand routing protocol for IEEE 802.15.4-based low rate wireless mesh networks (LRWMNs). The novelty of our work is that the proposed routing algorithms enable route discovery packets (RREQs) to be semi-directionally flooded with respect to a source-destination pair in a distributed manner without either physical or virtual location systems. Instead, we use the logical tree distance derived from the hierarchical addressing structure. The idea behind this is that nodes with longer tree distance to the destination than that of the source-destination pair are not involved in flooding RREQs. To evaluate the algorithms, we apply our algorithms into AODVjr and carry out extensive simulations while comparing the algorithms with AODVjr using network-wide flooding (NWF). Results show that the proposed algorithms drastically reduce RREQ overhead while providing comparable or better performance than NWF in AODVjr
Wind-Blown Foliage and Human-Induced Fading in Ground-Surface Narrowband Communications at 400 MHz
No full textAs small-scale fading is a spatial phenomenon, the movement of objects in the environment around static sensor nodes can induce significant fades. However, there have not been many works characterizing small-scale fading due to environmental factors for ground-surface wireless communications. We first measure the temporal fading characteristics experienced by antennas located just 1.5 cm above the surface of the ground due to wind-blown foliage or human movement in the environment for a narrowband channel in the 400-MHz frequency band. We then compare the extracted data to existing distributions and show that fading due to wind-blown foliage can be modeled as a Nakagami-m distribution, with wind speed and excess path-loss-dependent m shape factors. The alpha-mu distribution best characterizes the small-scale fading of a single human pedestrian, which is shown to have a repeatable pattern and can be up to 40 dB below the no-fading mean, whereas the Rician distribution, with an excess path-loss-dependent K-factor, can be used to characterize fading from multiple human pedestrians. We also report the second-order statistics of the average fade duration and the level crossing rate for fading caused by wind-blown foliage and multiple human pedestrians. Finally, we discuss the significance of the results on wireless sensor network protocol design and applications
Adaptive Queue Management Scheme For Internet Congestion Control
No full textThis thesis presents a new queue management scheme for congestion control in TCP/IP(Transmission Control protocol/Internet protocol) Networks. Congestion control in TCP/IP networks is very important to prevent congestion collapses which can lead to a loss in Internet services
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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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