1,721,171 research outputs found
Resolving doppler-ambiguity in OFDM-based joint radar and communication sensors
No full textTypical Joint Radar and Communications sensors exploiting OFDM waveforms evaluate the Range-Doppler Map by implementing the suboptimal batch algorithm with a length of the batches equal to the useful part of the OFDM symbols. As well known, this approach yields Doppler ambiguity for fast moving targets, whose Doppler frequency exceeds the inverse of the symbol duration. This paper presents a technique to resolve the Doppler ambiguity for fast-moving targets by transmitting OFDM symbols with a variable cyclic prefix and by applying an appropriate processing scheme to evaluate the Range Doppler Map. © 2023 German Institute of Navigation (DGON)
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
Detection, characterization and sizing of hydrogen induced cracking in pressure vessels using phased array ultrasonic data processing
Full text linkPressure vessels operating in sour service conditions in refinery environments can be subject to the risk of H2S cracking resulting from the hydrogen entering into the material. This risk, which is related to the specific working conditions and to the quality of the steel used, shall be properly managed in order to maintain the highest safety at a cost-effective level. Nowadays the typical management strategy is based on a risk based inspection (RBI) evaluation to define the inspection plan used in conjunction with a fitness for service (FFS) approach in defining if the vessel, although presenting dangerous defects such as cracks, can still be considered “fit for purpose” for a given time window based on specific fracture mechanics analysis. These vessels are periodically subject to non-destructive evaluation, typically ultrasonic testing. Phased Array (PA) ultrasonic is the latest technology more and more used for this type of application. This paper presents the design and development of an optimized Phased Array ultrasonic inspection technique for the detection and sizing of hydrogen induced cracking (HIC) type flaws used as reference for comparison. Materials used, containing natural operational defects, were inspected in “as-service” conditions. Samples have then been inspected by means of a “full matrix capture” (FMC) acquisition process followed by “total focusing method” (TFM) data post processing. FCM-TFM data have been further post-processed and then used to create a 3D geometrical reconstruction of the volume inspected. Results obtained show the significant improvement that FMC/TFM has over traditional PA inspection techniques both in terms of sensitivity and resolution for this specific type of defect. Moreover, since the FMC allows for the complete time domain signal to be captured from every element of a linear array probe, the full set of data is available for post-processing. Finally, the possibility to reconstruct the geometry of the component from the scans, including the defects present in its volume, represents the ideal solution for a reliable data transferring process to the engineering function for the subsequent FFS analysi
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
Target localization and velocity estimation in near Forward Scatter Radar Systems: Preliminary results
No full textIn this paper we investigate the two-dimensional target localization and motion parameters estimation capabilities of a near Forward Scatter (NFS) Radar system with a dual receiving antenna. Taking advantage of the low-cost Crystal Video Detector (CVD) commonly adopted in Forward Scatter Radar (FSR) configurations, in this work we propose a short-time CVD to test for target detection. Once the target has been detected, the Doppler frequency and the Direction of Arrival measurements extracted at two separate time instants are jointly exploited to localize the target in the (x,y) plane and to estimate its velocity components. As expected the achievable estimation accuracy depends on the time delay between the measurements. The experimental results achieved by means of a passive NFS system where FM transmissions are exploited as waveforms of opportunity support the practical applicability and confirm the effectiveness of the proposed approach
Multichannel Fusion of Subsurface Radar Images at Different Resolutions
No full textThe authors deal with the fusion of multichannel and multiresolution subsurface radar
images collected by different frequency channels. Since each radar frequency is most suited for
the investigation of a specific range of depths, an accurate analysis of the subsurfacc over an
extended depth interval requires images at different channels. By exploiting the physical model of
EM pulse propagation in a stratified medium, three multichannel Wiener filters are derived for
estimation of the subsurface impulse response from a set of radar surveys collected at different
frequencies. By properly combining the echoes received at the different channels, the filters yield
the high resolution of the high-frequency channels for the shallow interfaces and the good SNR of
the low-frequency channels for the decp interfaces. A complete theoretical as well as simulated
performance analysis is prescnted for the proposed filters. Moreover, the fusion techniques are
applied to real data collected at two sites: a homogeneous subsurface with a number of embedded,
known, finite objects and a simple stratified natural terrain. The former is used to assess the proper
operation of the multichannel deconvolution, while the latter is used to show that the desired
optimal performance is achieved for the interfaces at different depths
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