Below Horizon Aircraft Detection Using Deep Learning for Vision-Based Sense and Avoid

Commercial operation of unmanned aerial vehicles (UAVs) would benefit from an onboard ability to sense and avoid (SAA) potential mid-air collision threats. In this paper we present a new approach for detection of aircraft below the horizon. We address some of the challenges faced by existing vision-based SAA methods such as detecting stationary aircraft (that have no relative motion to the background), rejecting moving ground vehicles, and simultaneous detection of multiple aircraft. We propose a multi-stage, vision-based aircraft detection system which utilises deep learning to produce candidate aircraft that we track over time. We evaluate the performance of our proposed system on real flight data where we demonstrate detection ranges comparable to the state of the art with the additional capability of detecting stationary aircraft, rejecting moving ground vehicles, and tracking multiple aircraft

Buddhism, Christianity, and The Matrix: The Dialectic of Myth-Making in Contemporary Cinema

This essay analyzes the recent film The Matrix from the perspective of modern-day myth-making. After a brief plot summary of the film, I note the well-documented parallels to the Christian messianic narrative of Jesus. I then go on to highlight the often overlooked parallels to the Buddhist existential analysis of the human condition. In particular, I note a remarkable resonance between The Matrix and the fourth century (C.E.) philosophical school of Buddhism known as Yogacara. By highlighting the syncretic or combinative nature of the film\u27s symbolic narrative, I submit The Matrix as a cinematic example of the dialectical process of myth-making by means of Peter Berger\u27s theory of socio-cultural construction. Humans are mythologizing and, as Peter Berger would suggest, world-building creatures. We appropriate elements from our past and present to fashion epic narratives and myths for a variety of existential, sociological, and religious ends. Myths are not fixed narrative forms, however. Studies of traditionally oral cultures evidence considerable elasticity in the details of a particular myth.[i] And history also demonstrates that myths often evolve as a result of cultural diffusion and contact. Myths are constantly adapted to new cultural contexts and worldly realities. While the invention of writing inspired a more fixed status for some myths, it did not halt the ongoing adaptation and amalgamation of previously disparate mythological themes and concepts. In this essay, I will examine the recent popular science-fiction film The Matrix, written and directed by Larry and Andy Wachowski, from this perspective of mythological adaptation. While the Christian metaphors throughout the film have been well noted, significant elements of a Buddhist worldview are often overlooked. In particular, the symbolic and existential parallels to a fourth century (C.E.) philosophical school of Buddhism know as Consciousness-only (Vijñavada/Yogacara) are indeed striking. In addition to noting such parallels, I will submit The Matrix as a provocative example of modern-day myth-making. Appropriating familiar symbols and motifs into a new epic narrative is clearly not a contemporary phenomenon and I will borrow from Peter Berger\u27s dialectical theory of world building to elucidate this process. The foundation myths of many religions arguably reflect the same dialectical process I will try to illuminate here. Although The Matrix is not likely to become the foundation myth for a new religion, it will perhaps inform the worldviews, if only subtly and temporarily, of thousands of young adults. Indeed, this is the destiny of most myths. But who knows, this may become a classic along the lines of The Wizard of Oz or Star Wars. To characterize a contemporary film as myth is not without problems, not the least of which is qualifying such a genre into an acceptable definition of myth. Here I will adopt a definition offered by Finnish folklorist Lauri Honko. She delineates four criteria of myth with respect to form (narrative of sacred origin), content (cosmogonic in terms of cultural origin or existential condition), function (model for human activity), and context (in the sense that myth provides the ideological content for a sacred form of behavior ).[ii] I suggest that The Matrix qualifies in all respects as a mythological narrative. It is also important to note that myths are not disembodied texts divorced from time or place. Their language, symbols, and meaning are invariably tied to the context and worldview of origin. Moreover, the functional use of myths may range from a children\u27s story hour to a mechanism of political legitimization. In other words, myths serve any number of social, religious, ideological, or pedagogical functions. Movies, like any narrative form, can be considered a form of myth if they meet the criteria noted above. Star Wars, The Fisher King, Blade Runner, and 2001: A Space Odyssey represent appropriate examples according to this perspective. [i] See, for example, Raymond Firth\u27s The Plasticity of Myth, Ethnoligica 2 (1960), 181-88. [ii] Lauri Honko. The Problem of Defining Myth in Sacred Narrative: Readings in the Theory of Myth (Berkeley: University of California Press, 1984), 49-51

Convergence is Only Skin Deep: Craniofacial Evolution in Electric Fishes from South America and Africa (Apteronotidae and Mormyridae)

Apteronotidae and Mormyridae are species-rich clades of weakly electric fishes from Neotropical and Afrotropical freshwaters, respectively, known for their high morphological disparity and often regarded as a classic example of convergent evolution. Here, we use CT-imaging and 3D geometric morphometrics to quantify disparity in craniofacial morphologies, and to test the hypothesis of convergent skull-shape evolution in a phylogenetic context. For this study, we examined 391 specimens representing 78 species of Apteronotidae and Mormyridae including 30 of 37 (81%) of all valid genera with the goal to sample most of the craniofacial disparity known in these clades. We found no overlap between Apteronotidae and Mormyridae in the skull-shape morphospace using PCA and a common landmark scheme, and therefore no instances of complete phenotypic convergence. Instead, we found multiple potential instances of incomplete convergence, and at least one parallel shift among electric fish clades. The greatest components of shape variance in both families are the same as observed for most vertebrate clades: heterocephaly (i.e., opposite changes in relative sizes of the snout and braincase regions of the skull), and heterorhynchy (i.e., dorsoventral changes in relative snout flexion and mouth position). Mormyrid species examined here exhibit less cran- iofacial disparity than do apteronotids, potentially due to constraints associated with a larger brain size, ecological constraints related to food-type availability. Patterns of craniofacial evolution in these two clades depict a complex story of phenotypic divergence and convergence in which certain superficial similarities of external morphology obscure deeper osteological and presumably developmental differences of skull form and function. Among apteronotid and mormyrid electric fishes, craniofa- cial convergence is only skin deep

Optimal Bayesian Quickest Detection for Hidden Markov Models and Structured Generalisations

In this paper we consider the problem of quickly detecting changes in hidden Markov models (HMMs) in a Bayesian setting, as well as several structured generalisations including changes in statistically periodic processes, quickest detection of a Markov process across a sensor array, quickest detection of a moving target in a sensor network and quickest change detection (QCD) in multistream data. Our main result establishes an optimal Bayesian HMM QCD rule with a threshold structure. This framework and proof techniques allow us to to elegantly establish optimal rules for several structured generalisations by showing that these problems are special cases of the Bayesian HMM QCD problem. We develop bounds to characterise the performance of our optimal rule and provide an efficient method for computing the test statistic. Finally, we examine the performance of our rule in several simulation examples and propose a technique for calculating the optimal threshold

Balance differences in people with Parkinson disease with and without freezing of gait

Published in final edited form as: Gait Posture. 2015 September ; 42(3): 306–309. doi:10.1016/j.gaitpost.2015.06.007.BACKGROUND: Freezing of gait (FOG) is a relatively common and remarkably disabling impairment associated with Parkinson disease (PD). Laboratory-based measures indicate that individuals with FOG (PD+FOG) have greater balance deficits than those without FOG (PD-FOG). Whether such differences also can be detected using clinical balance tests has not been investigated. We sought to determine if balance and specific aspects of balance, measured using Balance Evaluation Systems Test (BESTest), differs between PD+FOG and PD-FOG. Furthermore, we aimed to determine if time-efficient clinical balance measures (i.e. Mini-BESTest, Berg Balance Scale (BBS)) could detect balance differences between PD+FOG and PD-FOG. METHODS: Balance of 78 individuals with PD, grouped as either PD+FOG (n=32) or PD-FOG (n=46), was measured using the BESTest, Mini-BESTest, and BBS. Between-groups comparisons were conducted for these measures and for the six sections of the BESTest using analysis of covariance. A PD composite score was used as a covariate. RESULTS: Controlling for motor sign severity, PD duration, and age, PD+FOG had worse balance than PD-FOG when measured using the BESTest (p=0.008, F=7.35) and Mini-BESTest (p=0.002, F=10.37), but not the BBS (p=0.27, F=1.26). BESTest section differences were noted between PD+FOG and PD-FOG for reactive postural responses (p<0.001, F=14.42) and stability in gait (p=0.003, F=9.18). CONCLUSIONS: The BESTest and Mini-BESTest, which specifically assessed reactive postural responses and stability in gait, were more likely than the BBS to detect differences in balance between PD+FOG and PD-FOG. Because it is more time efficient to administer, the Mini-BESTest may be the preferred tool for assessing balance deficits associated with FOG.This study was conducted with funding from the Davis Phinney Foundation, Parkinson's Disease Foundation, NIH R01 NS077959, NIH UL1 TR000448, Greater St. Louis American Parkinson Disease Association (APDA), APDA Center for Advanced PD Research at Washington University in St. Louis. The funding sources had no role in the study design, in the collection, analysis and interpretation of data; in the writing of the manuscript; or in the decision to submit the manuscript for publication. (Davis Phinney Foundation; Parkinson's Disease Foundation; R01 NS077959 - NIH; UL1 TR000448 - NIH; Greater St. Louis American Parkinson Disease Association (APDA); APDA Center for Advanced PD Research at Washington University in St. Louis