1,721,011 research outputs found
Reconfigurable intelligent surface for future wireless communication
Full text linkIn the current era of wireless communication, there is a constant demand for higher data rates to support the increasing use of data-intensive applications such as streaming video, online gaming, and high-definition video conferencing. These applications require a fast and reliable wireless connection to function properly. The demand for wireless services is constantly increasing, but the amount of available spectrum is finite. This means that network operators must find ways to use the available spectrum efficiently in order to support a large number of users and data-intensive applications. A more straightforward choice is to utilise higher frequencies which provide more bandwidth, but this, on the other hand, reduces the coverage area. Consequently, this would require a smaller cell size with more base stations raising deployment costs. Overall, meeting the demands of users in the current era of wireless communication requires a comprehensive and strategic approach to addressing the various challenges faced by network operators.
Lately, the concept of Reconfigurable Intelligent Surface (RIS) has been introduced, which is a technology that consists of nearly passive elements, i.e., active only when voltage is applied, with no Radio Frequency (RF) chain. Instead of tuning the network endpoints, the RIS is utilized to manipulate the propagation channel environment. It is envisioned that RIS will provide numerous benefits by 1) expanding the coverage area, 2) reducing the network deployment cost, 3) improving the energy efficiency of the network and 4) increasing the network capacity.
The thesis presents the world’s first in-house developed RIS prototype consisting of ‘4096 elements’ at Sub-6 GHz. The operation frequency of the RIS is kept around 3.75 GHz, which is compatible with the existing 5G operating bands. The elements are controlled via PositiveIntrinsic-Negative (PIN) diodes which switch between two-phase states. Furthermore, every unit element is individually controlled, which makes it usable to operate in the near field and perform channel estimation. The operational power consumption of the proposed RIS is observed to be 12-15 watts with beam switching speed reaching 15 ms.
Two distinct application areas have been explored, i.e., RIS-assisted wireless communication and RIS-assisted health care for vitals detection. In the communication scenario, the RIS is able to focus the beam at different angles and perform conventional beam steering in real time. Additionally, a demonstration of the Orthogonal Frequency Division Multiplexing (OFDM) communication setup shows the channel manipulation by the RIS with transmitter and receiver in the non-line-of-sight (NLoS). Experiments reveal improved signal conditions attained in the presence of RIS. In the context of health care, the benefit of RIS is investigated for vitals detection, including heartbeat and breathing rate. It is shown that RIS can assist in detecting the heartbeat and breathing rate in the NLoS. Alongside, the E-field exposure around the human head (Phantom model) is investigated in the presence of RIS. Measurement results show that the RIS can reduce the E-field exposure around the head by dynamically changing its electrical aperture, thereby resulting in a reduction of the uplink energy at the user’s terminal. Hence, the overall motivation of the thesis is to explore and investigate the efficacy of RIS both in communication and healthcare scenarios
Contactless Sensing Using Intelligent Walls
Full text linkHuman activity monitoring is a fascinating field of study that can help the disabled and/or elderly patients to live independently. Different ways have been proposed to identify human activities, including using sensors, cameras, wearables, and non-contact microwave sensing. Microwave sensing has recently attracted a great deal of attention because of its ability to resolve the privacy problems associated with cameras and the discomfort produced by wearables. Existing microwave sensing approaches, however, have the fundamental problem of requiring regulated and perfect conditions for high-accuracy activity detections, which limits their widespread application in non-line-of-sight (Non-LOS) contexts. Intelligent wireless walls (IWW) are proposed to enable high-precision activity monitoring in complicated areas where standard microwave sensing is ineffective. The IWW is a reconfigurable intelligent surface (RIS) capable of beam steering and beamforming and incorporated with machine learning algorithms, can accurately and automatically recognise human behaviours. Two complicated environments were considered for the experiment: a corridor junction scenario in which the transmitter and receiver are located in distinct corridor sections and a multi-floor situation in which the transmitter and receiver are located on various building levels. Three separate bodily movements are evaluated in each of the environments: sitting, standing, and walking. Two individuals, one male and one female, performed these tasks in both scenarios. It is shown that IWW provides a maximum detection increase of 28% in a multi-floor situation and 25% in a corridor junction scenario when compared to conventional microwave sensing without RIS
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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