English
norskInstitutt for fysikk og teknologi: Recent submissions
Now showing items 621-640 of 1276
-
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 ... -
Lumikot: Fast auroral transients during the growth phase of substorms
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-25)The development of a magnetospheric substorm may be classified into three phases: growth, expansion, and recovery. The growth phase is important as it includes processes that lead to the expansion. In a recent growth-phase study, a type of fast discrete auroral transient phenomena -- referred to as Lumikot -- were observed. The Lumikot are several kilometers across and move in the high-energy ... -
Relationship between the source size at the diffuser plane and the longitudinal spatial coherence function of the optical coherence microscopy system
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-25)Coherence properties of light sources are indispensable for optical coherence microscopy/tomography as they greatly influence the signal-to-noise ratio, axial resolution, and penetration depth of the system. In the present paper, we report the investigation of longitudinal spatial coherence properties of a pseudothermal light source (PTS) as a function of the laser spot size at the rotating diffuser ... -
Thickness-Dependent Resonant Raman and E' Photoluminescence Spectra of Indium Selenide and Indium Selenide/Graphene Heterostructures
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-28)Atomically thin, two-dimensional (2D) indium selenide (InSe) has attracted considerable attention because of the dependence of its bandgap on sample thickness, making it suitable for small-scale optoelectronic device applications. In this work, by the use of Raman spectroscopy with three different laser wavelengths, including 488, 532, and 633 nm, representing resonant, near-resonant, and conventional ... -
Hybrid graphene metasurface for near-infrared absorbers
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-19)We experimentally demonstrated an amorphous graphene-based metasurface yielding near-infrared super absorber characteristic. The structure is obtained by alternatively combining magnetron-sputtering deposition and graphene transfer coating fabrication techniques. The thickness constraint of the physical vapor–deposited amorphous metallic layer is unlocked and as a result, the as-fabricated graphene-based ... -
Comparative net energy analysis of renewable electricity and carbon capture and storage
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-08)Carbon capture and storage (CCS) for fossil-fuel power plants is perceived as a critical technology for climate mitigation. Nevertheless, limited installed capacity to date raises concerns about the ability of CCS to scale sufficiently. Conversely, scalable renewable electricity installations—solar and wind—are already deployed at scale and have demonstrated a rapid expansion potential. Here we show ... -
Evaluation of Six Atmospheric Reanalyses over Arctic Sea Ice from Winter to Early Summer
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-19)This study evaluates the performance of six atmospheric reanalyses (ERA-Interim, ERA5, JRA-55, CFSv2, MERRA-2, and ASRv2) over Arctic sea ice from winter to early summer. The reanalyses are evaluated using observations from the Norwegian Young Sea Ice campaign (N-ICE2015), a 5-month ice drift in pack ice north of Svalbard. N-ICE2015 observations include surface meteorology, vertical profiles from ... -
High-Throughput Total Internal Reflection Fluorescence and Direct Stochastic Optical Reconstruction Microscopy Using a Photonic Chip
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-16)Total internal reflection fluorescence (TIRF) is commonly used in single molecule localization based super-resolution microscopy as it gives enhanced contrast due to optical sectioning. The conventional approach is to use high numerical aperture microscope TIRF objectives for both excitation and collection, severely limiting the field of view and throughput. We present a novel approach to generating ... -
On the Role of the Atmospheric Energy Transport in 2xCO2-Induced Polar Amplification in CESM1
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-12)A doubling of the atmospheric CO<sub>2</sub> content leads to global warming that is amplified in the polar regions. The CO<sub>2</sub> forcing also leads to a change of the atmospheric energy transport. This transport change affects the local warming induced by the CO<sub>2</sub> forcing. Using the Community Earth System Model (CESM), the direct response to the transport change is investigated. ... -
Patch Size Evolution During Pulsating Aurora
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-30)We report both decreasing and increasing trends in the patch sizes during pulsating aurora events. About 150 pulsating auroral events over the Fennoscandian Lapland have been successfully analyzed for their average patch size, total patch area, and number of patches as a function of event time, typically 1–2 hr. An automatic routine has been developed to detect patches in the all‐sky camera images. ...
