Artikler, rapporter og annet (fysikk og teknologi): Recent submissions
Now showing items 501-520 of 947
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Direct growth of single-layer terminated vertical graphene array on germanium by plasma enhanced chemical vapor deposition
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-26)Vertically aligned graphene nanosheet arrays (VAGNAs) exhibit large surface area, excellent electron transport properties, outstanding mechanical strength, high chemical stability, and enhanced electrochemical activity, which makes them highly promising for application in supercapacitors, batteries, fuel cell catalysts, etc. It is shown that VAGNAs terminated with a high-quality single-layer graphene ... -
Unsupervised Feature Extraction – A CNN-Based Approach
(Peer reviewed; Book; Chapter, 2019-05-12)Working with large quantities of digital images can often lead to prohibitive computational challenges due to their massive number of pixels and high dimensionality. The extraction of compressed vectorial representations from images is therefore a task of vital importance in the field of computer vision. In this paper, we propose a new architecture for extracting such features from images in an ... -
The 3‐D Distribution of Artificial Aurora Induced by HF Radio Waves in the Ionosphere
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-21)We present 3‐D excitation rate estimates of artificial aurora in the ionospheric F layer, induced by high‐frequency radio waves from the European Incoherent Scatter heating facility. Simultaneous imaging of the artificial aurora was done with four separate Auroral Large Imaging System stations, permitting tomography‐like 3‐D auroral reconstruction of the enhanced atomic oxygen emissions at 6,300, ... -
The Case for Combining a Large Low‐Band Very High Frequency Transmitter With Multiple Receiving Arrays for Geospace Research: A Geospace Radar
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-09)We argue that combining a high‐power, large‐aperture radar transmitter with several large‐aperture receiving arrays to make a geospace radar—a radar capable of probing near‐Earth space from the upper troposphere through to the solar corona—would transform geospace research. We review the emergence of incoherent scatter radar in the 1960s as an agent that unified early, pioneering research in geospace ... -
Unsupervised Image Regression for Heterogeneous Change Detection
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-14)Change detection (CD) in heterogeneous multitemporal satellite images is an emerging and challenging topic in remote sensing. In particular, one of the main challenges is to tackle the problem in an unsupervised manner. In this paper, we propose an unsupervised framework for bitemporal heterogeneous CD based on the comparison of affinity matrices and image regression. First, our method quantifies ... -
Deep divergence-based approach to clustering
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-08)A promising direction in deep learning research consists in learning representations and simultaneously discovering cluster structure in unlabeled data by optimizing a discriminative loss function. As opposed to supervised deep learning, this line of research is in its infancy, and how to design and optimize suitable loss functions to train deep neural networks for clustering is still an open question. ... -
High-concentration photovoltaics for dual-use with agriculture
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-28)This study assesses the potential of transparent, tracking-integrated CPV to facilitate more effective dual-use of land for simultaneous agricultural and solar energy production. The concept leverages on the fact that a concentration system is a natural light splitter, separating direct solar radiation from the diffuse. Therefore a transparent CPV module using multijunction solar cells can generate ... -
Episodically Active Asteroid 6478 Gault
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-06)We present imaging and spectroscopic observations of 6478 Gault, a ~6 km diameter inner main-belt asteroid currently exhibiting strong, comet-like characteristics. Three distinct tails indicate that ultra-slow dust (ejection speed 0.15 ± 0.05 m s−1) was emitted from Gault in separate episodes beginning UT 2018 October 28 ± 5 (Tail A), UT 2018 December 31 ± 5 (Tail B), and UT 2019 February 10 ± 7 ... -
Adaptive fluctuation imaging captures rapid subcellular dynamics
(Journal article; Tidsskriftartikkel, 2019-07-22)In this work we have explored the live-cell friendly nanoscopy method Multiple Signal Classification Algorithm (MUSICAL) for multi-colour imaging of various organelles and sub-cellular structures in the cardiomyoblast cell line H2c9. We have tested MUSICAL for fast (up to 230Hz), multi-colour time-lapse sequences of various sub-cellular structures (mitochondria, endoplasmic reticulum, microtubules, ... -
Subauroral and polar traveling ionospheric disturbances during 7-9 September 2017 storms
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-12-25)This study provides new scenarios for storm time traveling ionospheric disturbance excitation and subsequent propagation at subauroral and polar latitudes. We used ground‐based total electron content observations from Global Navigation Satellite System receivers combined with wide field, subauroral ionospheric plasma parameters measured with the Millstone Hill Incoherent Scatter Radar during strong ... -
The Discus Comet: C/2014 B1 (Schwartz)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-08)Long-period comet C/2014 B1 (Schwartz) exhibits a remarkable optical appearance, like that of a discus or bi-convex lens viewed edgewise. Our measurements in the four years since discovery reveal a unique elongated dust coma whose orientation is stable with respect to the projected antisolar and orbital directions. With no tail and no trail, the limited influence of radiation pressure on the dust ... -
Machine learning assisted quantification of graphitic surfaces exposure to defined environments
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-17)We show that it is possible to submit the data obtained from physical phenomena as complex as the tip-surface interaction in atomic force microscopy to a specific question of interest and obtain the answer irrespective of the complexity or unknown factors underlying the phenomena. We showcase the power of the method by asking “how many hours has this graphite surface been exposed to ambient conditions?” ... -
A Novel Algorithm for Online Inexact String Matching and its FPGA Implementation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-14)Among the basic cognitive skills of the biological brain in humans and other mammals, a fundamental one is the ability to recognize inexact patterns in a sequence of objects or events. Accelerating inexact string matching procedures is of utmost importance when dealing with practical applications where huge amounts of data must be processed in real time, as usual in bioinformatics or cybersecurity. ... -
Special issue “Recent Advances in MST and EISCAT/Ionospheric Studies – Special Issue of the Joint MST15 and EISCAT18 Meetings, May 2017”
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-09-18)The Fifteenth Workshop on Technical and Scientific Aspects of MST Radar (MST15) and the Eighteenth EISCAT Symposium (EISCAT18) were jointly held in Tokyo, Japan, at the National Institute of Polar Research (NIPR) during May 26–31, 2017. The MST workshops have a long history of being the primary international meetings on the applications and development of mesosphere–stratosphere–troposphere (MST) ... -
Dilated temporal relational adversarial network for generic video summarization
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-10-12)The large amount of videos popping up every day, make it more and more critical that key information within videos can be extracted and understood in a very short time. Video summarization, the task of finding the smallest subset of frames, which still conveys the whole story of a given video, is thus of great significance to improve efficiency of video understanding. We propose a novel Dilated ... -
Spectral Decomposition and Extremes of Atmospheric Meridional Energy Transport in the Northern Hemisphere Midlatitudes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-03)The atmospheric meridional energy transport in the Northern Hemisphere midlatitudes is mainly accomplished by planetary and synoptic waves. A decomposition into wave components highlights the strong seasonal dependence of the transport, with both the total transport and the contributions from planetary and synoptic waves peaking in winter. In both winter and summer months, poleward transport extremes ... -
Rethinking knowledge graph propagation for zero-shot learning
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019)Graph convolutional neural networks have recently shown great potential for the task of zero-shot learning. These models are highly sample efficient as related concepts in the graph structure share statistical strength allowing generalization to new classes when faced with a lack of data. However, multi-layer architectures, which are required to propagate knowledge to distant nodes in the graph, ... -
Chip-Based Resonance Raman Spectroscopy Using Tantalum Pentoxide Waveguides
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-08)Blood analysis is an important diagnostic tool, as it provides a wealth of information about the patient's health. Raman spectroscopy is a promising tool for blood analysis, but widespread clinical application is limited by its low signal strength, as well as complex and costly instrumentation. The growing field of waveguide-based Raman spectroscopy tries to solve these challenges by working toward ... -
Traveling ionospheric disturbances and ionospheric perturbations associated with solar flares in September 2017
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-10)Solar flares provide strong impulsive radiation and energy injection to the sunlit upper atmosphere. The impact on the ionosphere is immense in spatial scale, and therefore, it is not immediately evident if dramatically elevated neutral heating can lead to excitation of acoustic gravity waves. Using primary observations from Global Navigation Satellite System differential TEC (total electron ... -
Assessment of Polarimetric Variability by Distance Geometry for Enhanced Classification of Oil Slicks Using SAR
(Peer reviewed; Chapter; Bokkapittel, 2019-11-14)In this paper, we introduce a new approach for investigation of polarimetric Synthetic Aperture Radar (PolSAR) images for oil slick analysis. Our method aims at enhancing discrimination of oil types by exploring the polarimetric features that can be produced by processing PolSAR scenes without dimensionality reduction. Taking advantage of a mixture description of the interactions among classes within ...