1,720,955 research outputs found
Automatic Recognition of General LPI Radar Waveform using SSD and Supplementary Classifier
No full textFor low probability of intercept (LPI) radars, frequency-modulated and phase-modulated continuous waveforms are widely used because of their low peak power compared to that of pulse waves (PW). However, there has been a limited number of studies on recognizing continuous wave (CW) LPI radar, in spite of its importance and popularity. In this paper, in order to recognize both PW and CW LPI radar waveforms, we propose an LPI radar waveform recognition technique (LWRT) based on a single-shot multi-box detector (SSD) and a supplementary classifier. It is demonstrated with Monte Carlo simulations that the proposed LWRT achieves classification performance similar to that of the current LWRT with the highest classification performance for PW LPI radar waveforms, even without the prior condition used in existing LWRTs. For CW LPI radar waveforms, on the other hand, with the combination of the SSD and the supplementary classifier, the proposed LWRT achieves extraordinary recognition performance for all 12 LPI radar modulation schemes (i. e., BPSK, Costas, LFM, Frank, P1, P2, P3, P4, T1, T2, T3, and T4) considered in the literature.
Wireless Interference Mitigation for Emerging Applications and Systems
Full text linkUniversity of Technology Sydney. Faculty of Engineering and Information Technology.Wireless jamming is one of the critical threats to emerging wireless applications, e.g., Ultra-reliable low-latency communication (URLLC). The problem becomes even more challenging when the jamming signals come simultaneously from multiple sources. This thesis aims to investigate and mitigate by leveraging signal beam-forming and machine learning (ML) techniques. It is observed that by varying the correlation coefficients, jammers can ``virtually change'' the jamming channels hence their nullspace even when these channels do not physically change. To tackle the problem, we propose techniques to monitor the jamming residual and effectively update the beam-forming matrix.
However, such a jamming residual monitoring process incurs additional system overhead, thus significantly reducing the spectral efficiency. Even ignoring the unknown strategy of the jammers and the challenging nullspace estimation process, the resulting problem is an integer programming problem, hence intractable to obtain its optimal solution. To deal with such uncertainty and incomplete information, we reformulate it using a partially observable semi-Markov decision process (POSMDP). We then design a deep dueling Q-learning-based technique to quickly obtain the optimal policy for legitimate devices.
Next, we study the methods to deal with jamming signals in the joint radar and communication (JRC) systems. Specifically, novel modulation and demodulation schemes were proposed for a frequency-hopping (FH) JRC system with robustness against jamming. In these schemes, both sub-pulse frequencies and durations are used for information modulation, leading to higher communication data rates. For information demodulation, a novel scheme was proposed by using the time-frequency analysis (TFA) technique and a `you only look once' (YOLO)-based detection system. Simulation results demonstrate the effectiveness of the proposed scheme.
Finally, we study jamming mitigation in joint communication and radar (JCR) systems. Specifically, we study how to optimize the durations of the jamming nullspace estimation, the preamble, and the data transmission phases. Increasing the duration of the nullspace estimation and the preamble phases can increase the radar's performance. However, such an increase also reduces the effective spectral efficiency of the communication function, because the data transmission phase fraction is decreased. Moreover, the surrounding radio environments of the JRC systems are typically dynamic with high uncertainties due to their high mobility, making the duration optimization problem even more challenging. To deal with such uncertainty, we reformulate the problem using a Markov decision process (MDP). Then, we design a deep dueling Q-learning-based technique to quickly obtain the optimal policy
저피탐 레이더 파형 인지 복합 시스템
No full text학위논문(석사) - 한국과학기술원 : 조천식녹색교통대학원, 2019.2,[58 p. :]In this study, a comprehensive automatic low probability of intercept (LPI) radar waveform recognition technique (LWRT) that includes both LPI radar signal classification and parameter extraction is proposed. It is shown with the Monte Carlo simulation that, even without the unrealistic assumptions used in the previous studies, the proposed LWRT achieves classification performance similar to that of the state-of-the-art LWRT for pulse wave (PW) LPI radar waveforms. And by the combination of the single shot multi-box detector (SSD) or YOLOv3 and a supplementary classifier, the proposed LWRT achieves an extraordinary classification performance for continuous (CW) LPI radar waveforms for all the twelve modulation schemes considered in the literature (i.e., BPSK, Costas, LFM, Frank, P1, P2, P3, P4, T1, T2, T3, and T4). Moreover, efficient parameter extraction functions are proposed to effectively estimate the parameters of the intercepted signal, which can help to design the countermeasure in electronic warfare.한국과학기술원 :조천식녹색교통대학원
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
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