1,720,974 research outputs found
Drone detection and classification based on radar cross section signatures
No full textIn this work, we show how drone detection and classification can be enabled by leveraging a database of radar cross section (RCS) signatures. First, we present a set of measurement results of the RCS of a carbon fiber drone model at 28 GHz. The measurements were performed in an anechoic chamber and provide essential information about the RCS signature of the specific drone. Then, we assess the RCS-based detection probability and the range error by running simulations in urban environments. The drones were positioned at different distances, from 30m to 90m, and the RCS signatures used for the detection and classification were obtained experimentally
Characterizing 60 GHz Patch Antenna Segments for Fully Digital Transceiver
No full textIn this work, we present the simulation and measurement results of patch antenna elements operating at 60 GHz for future integration with fully digital transceiver. The antennas are fabricated on Rogers 4350B substrate of 168 μm thickness and their radiation patterns are measured both in the anechoic chamber and planar near-field range. In addition, different types of transmission lines are designed and fabricated. Results for both patch antennas and transmission lines show rather good agreement between simulation and measurements. The measured -10dB bandwidth of single element is 1.76 GHz around center frequency of 60.3 GHz. In the future, 1x4 patch antenna array will be integrated with the four channel software-defined radio
What Positioning Accuracy is Sufficient for Reliable mmWave A2G Channel Measurements?
No full textIn this work, we investigate the significance of position accuracy for unmanned aerial vehicle (UAV) during millimeter-wave (mmWave) channel measurements. The studies are performed at 28 and 60 GHz frequencies. First, we study the effect of the error in the link distances on the 3GPP channel models. Second, we present ray tracing simulations performed in urban environment. We verify that the horizontal/vertical accuracy of ±0.5/0.8 meters may be enough to get reliable data. It should be noted that better accuracy can still improve the results but will require more effort to achieve. In addition, it is confirmed that more severe effect will be visible on the path loss values, while other parameters are not affected as strongly for the LOS case. We present the root mean square error for different positioning accuracies with respect to the reference case, i.e. no error in the UAV position, in angular and time domains which increases linearly with the decreasing accuracy
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
Multi-Array Designs for mmWave and Sub-THz Communication to UAVs
No full textUnmanned Aerial Vehicles (UAVs) are steadily being considered for scenarios demanding high bandwidth, low latency communications for video and sensor data transfer as well as real-Time control. UAVs may also be used as mobile aerial Base Station (BS) for maintaining the communication in emergency scenarios. The millimeter wave (mmWave) bands, including the sub-THz frequencies above 100 GHz, are an attractive technology for high data rate UAV connectivity due to the wide bandwidths available at these frequencies. This paper studies antenna and codebook design for UAV communication at both 28 and 140 GHz with realistic antenna simulations and flight patterns. The analysis shows that multi-Array configurations with proper codebook design are necessary for uniform spherical coverage and become particularly important in long range applications. The paper thus proposes a four array design with patch antennas. Simulations indicate that the design can achieve in excess of 1 Gbps data rates at a range of 1 km, with reasonable power levels and moderate rain fades. A simulation with a real public safety mission flight shows that beam tracking can be maintained even under high drone movements and rotations
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
Lightweight UAV-based Measurement System for Air-to-Ground Channels at 28 GHz
No full textWireless communication at millimeter wave frequencies is an attractive option for high-bit-rate connectivity to unmanned aerial vehicles (UAVs). However, conducting the channel measurements necessary to assess the communication performance at these frequencies has been challenging due to the severe payload and power restrictions in commercial UAVs. This work presents a novel lightweight (approximately 1.3kg) channel measurement system at 28GHz installed on a commercially available UAV. A ground transmitter equipped with a horn antenna conveys sounding signals to a UAV equipped with a lightweight spectrum analyzer. We demonstrate that the measurements can be highly influenced by the onboard antenna pattern as shaped by the UAV's frame. A calibration procedure is presented to correct for the resulting angular variations in antenna gain. The measurement setup is then validated on real flights from an airstrip at distances in excess of 300m
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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