91 research outputs found
A novel Bayesian strategy for the identification of spatially-varying parameters and model validation in inverse problems: an application to elastography
Get PDFThe present paper proposes a novel Bayesian, computational strategy in the context of model-based inverse problems in elastostatics. On one hand we attempt to provide probabilistic estimates of the material properties and their spatial variability that account for the various sources of uncertainty. On the other hand we attempt to address the question of model fidelity in relation to the experimental reality and particularly in the context of the material constitutive law adopted. This is especially important in biomedical settings when the inferred material properties will be used to make decisions/diagnoses. We propose an expanded parametrization that enables the quantification of model discrepancies in addition to the constitutive parameters. We propose scalable computational strategies for carrying out inference and learning tasks and demonstrate their effectiveness in numerical examples with noiseless and noisy synthetic data.<br/
Hertzian Fields: Exploring WiFi microwave signals as a spatial and embodied sensing medium for art
No full textThesis (Ph.D.)--University of Washington, 2023This dissertation is centered around a series of three artworks (Hertzian Fields) that explore WiFi as a spatial and embodied sensing medium. These works use a new sensing technique developed by the author that leverages the interference of the human body on WiFi signals to create highly responsive live performance and interactive systems. Hertzian Field #1 (2014) is an augmented reality immersive environment using sound to explore the materiality of WiFi communication through its interaction with space and the human body. Hertzian Field #2 (2016) is a 20'-25' augmented reality immersive performance for solo performer, WiFi fields, computers and surround sound that conjures a phenomenology of the hertzian medium explored through sound and movement. The Water Within (Hertzian Field #3 and #3.1) is a reactive wet sauna: an intimate multi-sensory environment of complete immersion, combining WiFi sensing fields, machine listening software, embedded 3D sound, hot steam, and architectural design. Steered by the flows and variable densities of water molecules traced in steam and bodies by (ab)using WiFi, it creates a regenerative post-relational experience that celebrates interference, signal-loss, and disconnecting. The piece exists in two iterations and formats: an interactive installation (2016) and a composed interactive experience (2018).
The dissertation describes the author's conceptual and technical approach in using WiFi microwave signals as an artistic medium. It also examines the background, context, ideas and research processes that led to the creation of these works. In doing so, it lays the foundation for developing a better and deeper understanding of microwaves and WiFi signals, investigates their artistic potential, and discusses related approaches by other artists.
Chapter One (Introduction: The hertzian medium) introduces core ideas and concepts regarding the medium. This includes: a discussion on the impact of wirelessness in contemporary living and how it has transformed our interactions with and understanding of the world; an overview of the physics of electromagnetism and the electromagnetic spectrum; and an investigation of the hertzian (i.e. radio and microwaves) as a multilayered medium consisting of seven interconnected layers: physics, science, imagination, engineering, use, impact, regulation.
Chapter Two (The birth of a medium: Energy becomes technology) introduces a media archaeological approach as a method for grasping what the medium affords, and how our imagination of what we can use it for has developed over time. It presents an overview of key developments in hertzian science, imagined and realized applications, and their impact. This chapter focuses primarily on the early years around Heinrich Hertz’s discovery of electromagnetism, looking at the birth of wireless technologies relevant to the Hertzian Field series: communication, broadcast, hacking and electronic warfare, navigation, meteorology, radio astronomy, and radar, before closing with a section on the development of WiFi.
Chapter Three (Radar and Direction-Finding in sonic art and beyond) surveys musical instruments and artworks based on spatial and/or embodied uses of the hertzian as a sensing medium. The emphasis is on sound-centric practices and specific technologies that have been used to this extent: from capacitative / electric field sensing, to musical instruments utilizing direction-finding principles, to spatial uses of broadcast radio, to doppler radar systems. Instruments discussed include: Theremin and Terpsitone; Pupitre d'Espace; Radio Baton; Marimba Lumina. Artworks by the following artists are examined: Max Neuhaus; Edwin van der Heide; Christina Kubisch; John Cage; Philippa Cullen; Liz Phillips; Sonia Cillari; Tetsuo Kogawa; Anna Friz; Edward Ihnatowicz; Steve Mann; Joe Paradiso / MIT Lab; Arthur Elsenaar; Godfried-Willem Raes.
Chapter Four (First hertzian explorations: From the network to the body, from WiFi to Radar) turns to the author's own work. It presents the first phase (2010-14) of his research trajectory on the hertzian medium, and introduces three projects in which he explored WiFi and broadcast radio.
Chapter Five (Ubiquitous sensing with radio waves and microwaves) dives into the technological context influencing the author's research. It introduces the field of Ubiquitous Sensing and discusses relevant localization and device-free sensing techniques, concluding with a discussion on the physics and biological factors involved so as to comprehend how and why such techniques work.
Chapter Six (Wireless Information Retrieval: Sensing with WiFi signals) presents the device-free WiFi-sensing technique that the author developed for the Hertzian Field series. Combining elements from Ubiquitous Sensing and Music Information Retrieval, this technique performs multi-layered feature extraction on the Received Signal Strength Indication (RSSI) of WiFi Beacon frames to deduce a variety of information related to the movement of uninstrumented bodies, and to changes in environmental factors (e.g. humidity).
Chapter Seven (Composing Hertzian Fields) discusses strategies for creating works with this technique, and examines the three works of the Hertzian Field series in detail. It finally touches on ideas for future work by the author
The role of SDN and NFV for dynamic bandwidth allocation and QoE adaptation of video applications in home networks
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Nutritional characterization of carobs and traditional carob products
No full textTwenty traditional carob products were measured for their nutritional composition, and their results were compared with the pulp of Cypriot carob cultivars. Moisture, ash, fat, proteins, sugars, dietary fibers, minerals, caffeine‐theobromine, carbohydrates, and energy value were determined. Fluctuations of the nutritional composition values based on the ingredients’ chemical synthesis and product manufacturing process were noted. Only 60% of the products had a label indicating their nutritional value, and the majority of them (75%) were consistent with that of labeling. Chemometric analyses distinguished the carob products according to their type and the discriminator components highlighted their particular nutritional value. Carobs can be characterized as functional foods with low‐fat content, high content in dietary fibers, and high content and/or source of minerals; however, carob products partially satisfied those health and nutritional claims as expected. This pilot research contributes to the nutritional estimation of carob and highlights the traditional carob products
On the Achievable Rates of OFDM with Common Phase Error Compensation in Phase Noise Channels
No full textThis paper considers the problem of analytically assessing the maximum achievable rates (capacity) of orthogonal frequency division multiplexing (OFDM) transmissions when the receiver, for complexity reasons, only accounts for the common phase error (CPE) effect due to phase noise impairments with inter-carrier interference (ICI) treated as noise. By recognizing that the functional form of the CPE with respect to the phase noise realization is actually a free design parameter, determination of the capacity is posed as a functional optimization problem with respect to the, so-called, CPE function. A simple lower bound of the capacity is obtained, revealing the performance degradation due to the unknown CPE at the receiver, as well as the suboptimal performance achieved in severe phase noise conditions by the conventional CPE function that is routinely employed in previous works. The existence of an optimal number of subcarriers that balances the effects of the (unknown) CPE and ICI is highlighted and critical system design/operation issues, such as selection of the CPE function and effect of unknown channel on the achievable rate, are discussed. The analysis in this paper can be employed for determining the suitability of OFDM in phase noise channels and provides a tractable utility function for resource allocation purposes.Manuscript received October 7, 2016; revised February 10, 2017 and May 5, 2017; accepted May 6, 2017. Date of publication May 17, 2017; date of current version August 14, 2017. This research work was made possible by grant number NPRP 6-1326-2-532 from the Qatar National Research Fund, QNRF (a member of the Qatar Foundation, QF). The statements made herein are the sole responsibility of the authors. The associate editor coordinating the review of this paper and approving it for publication was G. Colavolpe. (Corresponding author: Stelios Stefanatos.) S. Stefanatos is with the Department of Digital Systems, University of Piraeus, 18534 Piraeus, Greece (e-mail: [email protected]).Scopu
A Greek – Makriyannis
No full textTitle: Ἕνας Ἕλληνας - ὁ Μακρυγιάννης (Α Greek – Makriyannis) Originally published: As a leaflet in Alexandria, 1943 Language: Greek The excerpts used are from Γεωργίου Σεφέρη, Δοκιμές τ. Α,’ (Athens: Ἴκαρος, 1974), pp. 236–237, 240–241, 257–259, 261–262. About the author George (Georgios) Seferis [1900, Smyrna (Tur. Izmir, present-day Turkey) – 1971, Athens]: poet, literary critic and diplomat. His father Stelios Seferiadis was a famous lawyer as well as a translator and poet. The family mili..
A Greek – Makriyannis
No full textTitle: Ἕνας Ἕλληνας - ὁ Μακρυγιάννης (Α Greek – Makriyannis) Originally published: As a leaflet in Alexandria, 1943 Language: Greek The excerpts used are from Γεωργίου Σεφέρη, Δοκιμές τ. Α,’ (Athens: Ἴκαρος, 1974), pp. 236–237, 240–241, 257–259, 261–262. About the author George (Georgios) Seferis [1900, Smyrna (Tur. Izmir, present-day Turkey) – 1971, Athens]: poet, literary critic and diplomat. His father Stelios Seferiadis was a famous lawyer as well as a translator and poet. The family mili..
Towards the Assessment of Soil-Erosion-Related C-Factor on European Scale Using Google Earth Engine and Sentinel-2 Images
No full textSoil erosion is a constant environmental threat for the entirety of Europe. Numerous studies have been published during the last years concerning assessing soil erosion utilising Remote Sensing (RS) and Geographic Information Systems (GIS). Such studies commonly employ empirical erosion models to estimate soil loss on various spatial scales. In this context, empirical models have been highlighted as major approaches to estimate soil loss on various spatial scales. Most of these models analyse environmental factors representing soil-erosion-influencing conditions such as the climate, topography, soil regime, and surface vegetation coverage. In this study, the Google Earth Engine (GEE) cloud computing platform and Sentinel-2 satellite imagery data have been combined to assess the vegetation-coverage-related factor known as cover management factor (C-factor) at a high spatial resolution (10 m) considering a total of 38 European countries. Based on the employment of the RS derivative of the Normalised Difference Vegetation Index (NDVI) for January and December 2019, a C-factor map was generated due to mean annual estimation. National values were then calculated in terms of different types of agricultural land cover classes. Furthermore, the European C-factor (CEUROPE) values concerning the island of Crete (Greece) were compared with relevant values estimated for the island (CCRETE) based on Sentinel-2 images being individually selected at a monthly time-step of 2019 to generate a series of 12 maps for the C-factor in Crete. Our results yielded identical C-factor values for the different approaches. The outcomes denote GEE’s high analytic and processing abilities to analyse massive quantities of data that can provide efficient digital products for soil-erosion-related studies
BECLR: Batch Enhanced Contrastive Unsupervised Few-Shot Learning
No full textThere exists a fundamental gap between human and artificial intelligence. Deep learning models are exceedingly data hungry for learning even the simplest of tasks, whereas humans can easily adapt to new tasks with just a handful of samples. Unsupervised few-shot learning (U-FSL) aspires to bridge this gap, without relying on costly annotations. Inspired by the efficiency of contrastive representation learning, we propose a novel batch enhanced contrastive U-FSL pretraining methodology (coined as BECLR) to infuse instance- and class-level insightswithin a contrastive framework. To enable the sampling of meaningful positives, we introduce an innovative dynamic clustered memory module (DyCE), which maintains highly-separable latent space partitions, through iterative equipartitioned updates. We also propose an effective, optimal transport (OT)-based feature alignment strategy (OpTA), to address sample bias in the U-FSL inference stage and further boost the end-to-end performance of BECLR in low-shot settings. Our extensive experimental evaluation corroborates the efficacy of our design choicesin BECLR, which sets a new state-of-the-art on the most widely adopted U-FSL benchmarks miniImageNet and tieredImageNet (offering up to 14% and 12% improvements, respectively), as well as on challenging cross-domain scenarios.Computer Scienc
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