79 research outputs found
A novel Bayesian strategy for the identification of spatially-varying parameters and model validation in inverse problems: an application to elastography
No full textThe 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
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
Sentinel data management on Google Earth Engine
No full textSummarization: The need for data management and correlation within a spatial context has led the scientific community to develop platforms that can handle a variety of spatio-temporal data. Geographic Information Systems have helped many scientific disciplines in data analysis and management as well as decision-making through appropriate spatial information processing. In recent years, in the information systems industry, the rapid development of the Cloud technology has also been introduced in the field of Geographic Information Systems (GIS). In the framework of the Data Democratization, namely the open availability of large volumes of data and the ability to visualize and process them by the average user, the Google Earth Engine platform was developed. By offering daily data collected from various satellite imagery services (e.g. ESA, USGS, MODIS) and at the same time providing the user with a programming API application development environment, it enables any researcher to make use of satellite remote sensing data. This diploma thesis aims at exploring the possibilities of the platform, by developing a number of remote sensing applications. Through the successful implementation of all the algorithms, the familiarization with the application and the interaction with the community, we conclude that Earth Engine can become a platform for data analysis, and also a powerful analytical tool in the hands of the experienced programmer. Περίληψη: Η ανάγκη για διαχείριση και συσχέτιση δεδομένων μέσα σε ένα χωρικό πλαίσιο, οδήγησε την επιστημονική κοινότητα στην ανάπτυξη πληροφοριακών συστημάτων τα οποία μπορούν να διαχειριστούν ποικίλα χωροχρονικά δεδομένα. Οι πλατφόρμες Γεωγραφικών Πληροφοριακών Συστημάτων εδώ και αρκετά χρόνια βοηθούν πολλούς επιστημονικούς κλάδους στην ανάλυση και διαχείριση δεδομένων καθώς και στη διαδικασία λήψης αποφάσεων μέσα από την κατάλληλη επεξεργασία της χωρικής πληροφορίας. Τα τελευταία χρόνια στον κλάδο των πληροφοριακών συστημάτων η ραγδαία εξέλιξη της τεχνολογίας Νέφους, εισήχθη και στον κλάδο των Γεωγραφικών Πληροφοριακών Συστημάτων (GIS). Στο πλαίσιο της Δημοκρατικοποίησης της πληροφορίας, δηλαδή την ανοικτή διάθεση μεγάλου όγκου δεδομένων και την ικανότητα οπτικοποίησης και επεξεργασίας αυτών από το μέσο χρήστη, αναπτύχθηκε η πλατφόρμα Google Earth Engine. Προσφέροντας καθημερινά δεδομένα, που συλλέγονται από διάφορες υπηρεσίες δορυφορικών συστημάτων (π.χ. ESA, USGS, MODIS) και ταυτόχρονα διαθέτοντας στο χρήστη ένα προγραμματιστικό περιβάλλον ανάπτυξης εφαρμογών API, δίνει τη δυνατότητα σε οποιονδήποτε ερευνητή να κάνει χρήση δεδομένων δορυφορικής Τηλεπισκόπησης. Η διπλωματική εργασία στοχεύει στη διερεύνηση των δυνατοτήτων της πλατφόρμας, μέσω της ανάπτυξης πλήθους εφαρμογών Τηλεπισκόπησης. Μέσα από την επιτυχή υλοποίηση όλων των αλγορίθμων, την τριβή με την εφαρμογή και την αλληλεπίδραση που υπήρξε με την κοινότητα, συμπεραίνουμε ότι η Earth Engine, μπορεί να αποτελέσει μια πλατφόρμα εξοικείωσης με την ανάλυση δεδομένων, αλλά και ένα πανίσχυρο αναλυτικό εργαλείο στα χέρια του έμπειρου προγραμματιστή
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
Assessment of Intra-Annual and Inter-Annual Variabilities of Soil Erosion in Crete Island (Greece) by Incorporating the Dynamic “Nature” of R and C-Factors in RUSLE Modeling
No full textUnder the continuously changing conditions of the environment, the exploration of spatial variability of soil erosion at a sub-annual temporal resolution, as well as the identification of high-soil loss time periods and areas, are crucial for implementing mitigation and land management interventions. The main objective of this study was to estimate the monthly and seasonal soil loss rates by water-induced soil erosion in Greek island of Crete for two recent hydrologically contrasting years, 2016 (dry) and 2019 (wet), as a result of Revised Universal Soil Loss Equation (RUSLE) modeling. The impact of temporal variability of the two dynamic RUSLE factors, namely rainfall erosivity (R) and cover management (C), was explored by using rainfall and remotely sensed vegetation data time-series of high temporal resolution. Soil, topographical, and land use/cover data were exploited to represent the other three static RUSLE factors, namely soil erodibility (K), slope length and steepness (LS) and support practice (P). The estimated rates were mapped presenting the spatio-temporal distribution of soil loss for the study area on a both intra-annual and inter-annual basis. The identification of high-loss months/seasons and areas in the island was achieved by these maps. Autumn (about 35 t ha−1) with October (about 61 t ha−1) in 2016, and winter (about 96 t ha−1) with February (146 t ha−1) in 2019 presented the highest mean soil loss rates on a seasonal and monthly, respectively, basis. Summer (0.22–0.25 t ha−1), with its including months, showed the lowest rates in both examined years. The intense monthly fluctuations of R-factor were found to be more influential on water-induced soil erosion than the more stabilized tendency of C-factor. In both years, olive groves in terms of agricultural land use and Chania prefecture in terms of administrative division, were detected as the most prone spatial units to erosion
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..
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
Anamnesis of tomorrow: Rediscovering the raison d’être of the National Archives of the Netherlands in the age of digital transformation.
No full textAn archive is a repository of documents, usually of historical importance. Therefore, one could say that the National Archive of the Netherlands exists as a result of the documents it holds. In fact, its contents include: 137 km of documents, 15 million photographs, 300,000 historical maps and drawings, and 800 terabyte of digital files. However, as our everyday life becomes more and more digital, the National Archive faces a distinctive upcoming change; transitioning from document-centredness to data-centredness. Within this framework, this project aims to answer the following question: Do archival buildings have a future in the Digital Age? Can archives exist without documents? Or are they destined for obsolescence? Through a qualitative research in the cultural value and societal role of archives the project seeks answers to the above questions. In continuation, new questions are brought up which aim to direct the project in an architectural conclusion. Whether the Archive remains as we know it or changes, one thing is sure; the purpose of the existing building has to be redefined. In this pursuit, several ingredients are put together which relate to social, contextual, structural, architectural and sustainability issues. The project considers not only the re-design of the National Archive building but the wider re-design of the site, as an important piece of urban fabric to the city of the Hague.All things considered, the National Archive is to be visualised as a more public place and a piece of public infrastructure that responds to a multiplicity of challenges.Architecture, Urbanism and Building Sciences | Building Technolog
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