1,721,039 research outputs found
Channel estimation for high speed unmanned aerial vehicle with STBC in MIMO radio links
No full textThis paper proposes a channel estimation method based on Kalman filter and adaptive estimation with space-time block code (STBC) and multiple antenna systems [multiple input single output (MISO) and multiple input multiple output (MIMO)] for high speed UAVs. Simulations have been done in time-varying Rayleigh faded channels for BPSK and QPSK. The proposed technique shows a very good error for severely faded channels. Application of Alamouti STBCs with diversity based on multiple antennas provides improved performance in faded wireless channels. Alamouti transmit diversity scheme, however, relies on the availability of accurate channel state information (CSI) for unmanned aerial vehicles (UAVs). Simulation results show that our proposed method achieves accurate estimation for the SNR and Doppler shift in a wide range of velocities and SNRs
UAV Channel Estimation with STBC in MIMO Systems
No full textThe combination of coding with spatial diversity opens up new dimensions in wireless communications with emphasize to Unmanned Aerial Vehicles (UAVs), and can offer effective solutions for wireless communication channels. Application of Alamouti Space-Time Block Codes (STBCs) with diversity with multiple antennas provide improved performance in faded wireless channels. Alamouti transmit diversity scheme, however, relies on the availability of accurate Channel State Information (CSI). This paper proposes a channel estimation method based on Kalman filter with STBC codes and multiple antenna systems, namely Multiple-Input Single-Output (MISO) and Multiple-Input Multiple-Output (MIMO) systems. Simulations have been done in time-varying Rayleigh faded channels for BPSK and QPSK. The proposed technique seems to obtain an error performance closer to that of a known channel information case in severely faded channel considerations
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
Synaptic behaviour in ZnO-rGO composites thin film memristor
No full textA zinc oxide (ZnO)-reduced graphene oxide (rGO) composite thin film memristive device is reported. Further, it has been shown that it is possible to implement Hebbian learning rules like, the spike-timing-dependent plasticity, using this device. Furthermore, a circuit on PCB is developed; this circuit can imitate the biological spike firing scheme and activate the memristor synapse. The fabricated device along with the custom made circuit can be extended for developing future neuromorphic circuit application
A wireless sensor node based on microbial fuel cell
No full textIn recent years there has been a widespread use of wireless sensor networks that found their application in complex systems where a lot of physical quantities have to be monitored. This nodes must deal with different physical quantities and must operate in different environments. In many applications the most critical aspect is the power supply, because frequently is possible to provide power supply by wires and sometimes the use of batteries is not an acceptable solution. This latter limitation occurs when the number of nodes is very high and/or the operation of battery substitution is very complex. Moreover, environmental requests for pollutant reduction and for renewable materials represents another limitation for the use power supply generation based on battery. For these reasons it can be useful to develop power sensor nodes which use energy harvested directly on the operation site, making the sensors energetically autonomous. In this paper we present an innovative sensor node based on Microbial Fuel Cells (MFCs). The implemented node proves the viability of MFC for the energy harvesting in sensor networks. This system uses the electric energy provided by the bacteria present in the soil as power supply for an ultra low power electronic system, based on a micro-controller equipped with a digital transceiver. The designed system is able to acquire data from a sensor and transmit them wirelessly. The scarcity of available energy and the limited voltages of the MFC require to design new schemes for the energy harvesting and the power supply, as well as new working modes which must satisfy the strong energy constraints
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
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