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Ranking Using Transition Probabilities Learned from Multi-Attribute Data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-09-13)In this paper, as a novel approach, we learn Markov chain transition probabilities for ranking of multi-attribute data from the inherent structures in the data itself. The procedure is inspired by consensus clustering and exploits a suitable form of the PageRank algorithm. This is very much in the spirit of the original PageRank utilizing the hyperlink structure to learn such probabilities. ... -
Rapid Colorimetric pH-Responsive Gold Nanocomposite Hydrogels for Sensing Applications
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-04-27)Surface functionalization of metallic nanoparticles (NPs) with external groups can be engineered to fabricate sensors that are responsive to various stimuli like temperature, pH, and numerous ions. Herein, we report the synthesis of gold nanoparticles (GNPs) functionalized with 3-mercaptopropionic acid (GNPs-MPA) and the doping of these nanoparticles into hydrogel materials using the ... -
Rapid prototyping of 1xN multifocus gratings via additive direct laser writing
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-05)Multifocus gratings (MFGs) enable microscopes and other imaging systems to record entire Z-stacks of images in a single camera exposure. The exact grating shape depends on microscope parameters like wavelength and magnification and defines the multiplexing onto a grid of MxN Z-slices. To facilitate the swift production and alteration of MFGs for a system and application at hand, we have developed ... -
Rechargeable Iron-Ion Battery Using a Pure Ionic Liquid Electrolyte
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-07)A rechargeable iron-ion battery (Fe-ion battery) has been fabricated in our laboratory using a pure ionic liquid electrolyte. Magnetic ionic liquids of 1-butyl-3-methylimidazolium tetrachloroferrate (BmimFeCl<sub>4</sub>) and 1-methyl-3-octylimidazolium tetrachloroferrate (OmimFeCl<sub>4</sub>) are synthesized and utilized as electrolytes in this work. The chemical structure of the two ionic ... -
Reconsidering Representation Alignment for Multi-View Clustering
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-13)Aligning distributions of view representations is a core component of today’s state of the art models for deep multi-view clustering. However, we identify several drawbacks with naïvely aligning representation distributions. We demonstrate that these drawbacks both lead to less separable clusters in the representation space, and inhibit the model’s ability to prioritize views. Based on these ... -
Reconstructing force profiles with an amplitude-modulation AFM in tapping mode
(Research report; Forskningsrapport, 2020-07)Here we demonstrate how to reconstruct force profiles with an amplitude-modulation AFM operated in in standard tapping mode. Our example is based on the Cypher scanning probe microscope from Asylum Research. The method is based on Sader and Katan’s algorithm, but we have implemented an experimental set-up that allows for robust reconstruction. We discuss the details here. -
Reconstruction of intermittent time series as a superposition of pulses
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05)Fluctuations in a vast range of physical systems can be described as a superposition of uncorrelated pulses with a fixed shape, a process commonly referred to as a (generalized) shot noise or a filtered Poisson process. In this paper, we present a systematic study of a deconvolution method to estimate the arrival times and amplitudes of the pulses from realizations of such processes. The method shows ... -
Reconstruction of precipitating electrons and three-dimensional structure of a pulsating auroral patch from monochromatic auroral images obtained from multiple observation points
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-12)In recent years, aurora observation networks using high-sensitivity cameras have been developed in the polar regions. These networks allow dimmer auroras, such as pulsating auroras (PsAs), to be observed with a high signal-to-noise ratio. We reconstructed the horizontal distribution of precipitating electrons using computed tomography with monochromatic PsA images obtained from three observation ... -
Reconstruction of the full-polarimetric covariance matrix from compact-polarimetric synthetic aperture radar data with convolutional neural networks
(Master thesis; Mastergradsoppgave, 2017-09-05)The focus of this thesis is to find an alternative way to reconstruct a pseudo quadrature polarimetric (quad-pol) covariance matrix from compact polarimetric (compact-pol) data. In the latest years, the compact polarimetry SAR mode was developed and used more and more widely. It provides a good compromise between area covered and information content per pixel [13]. The literature has focused ... -
A red tide in the pack ice of the Arctic Ocean
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-02)In the Arctic Ocean ice algae constitute a key ecosystem component and the ice algal spring bloom a critical event in the annual production cycle. The bulk of ice algal biomass is usually found in the bottom few cm of the sea ice and dominated by pennate diatoms attached to the ice matrix. Here we report a red tide of the phototrophic ciliate <i>Mesodinium rubrum</i> located at the ice-water interface ... -
The red-sky enigma over Svalbard in December 2002
(Journal article; Peer reviewed; Tidsskriftartikkel, 2005-07-27)On 6 December 2002, during winter darkness, an extraordinary event occurred in the sky, as viewed from Longyearbyen (78° N, 15° E), Svalbard, Norway. At 07:30 UT the southeast sky was surprisingly lit up in a deep red colour. The light increased in intensity and spread out across the sky, and at 10:00 UT the illumination was observed to reach the zenith. The event died out at about 12:30 UT. Spectral ... -
Reduced models for geophysical fluid dynamics
(Master thesis; Mastergradsoppgave, 2013-07-16)This thesis present a self-consistent derivation of reduced fluid models for geophysical dynamics confined to the midlatitude region. The reduced model will be derived by use of a regular perturbation method, that gives the same result as the classical models, such as the barotropic and baroclinic quasi-gestrophic potential vorticity model. It will be shown that such a rigorous treatment self-consistently ... -
Reducing Objective Function Mismatch in Deep Clustering with the Unsupervised Companion Objective
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-19)Preservation of local similarity structure is a key challenge in deep clustering. Many recent deep clustering methods therefore use autoencoders to help guide the model's neural network towards an embedding which is more reflective of the input space geometry. However, recent work has shown that autoencoder-based deep clustering models can suffer from objective function mismatch (OFM). In order to ... -
Reinforced Auto-Zoom Net: Towards Accurate and Fast Breast Cancer Segmentation in Whole-Slide Images
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-09-20)Convolutional neural networks have led to significant breakthroughs in the domain of medical image analysis. However, the task of breast cancer segmentation in whole-slide images (WSIs) is still underexplored. WSIs are large histopathological images with extremely high resolution. Constrained by the hardware and field of view, using high-magnification patches can slow down the inference process and ... -
Relating Photoelectrochemistry and Wettability of Sputtered Cu- and N-Doped TiO<sub>2</sub> Thin Films via an Integrated Approach
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06-06)We present here an integrated study of the photoelectrochemical and hydrophilic properties of sputtered TiO<sub>2</sub> thin films, enhanced by means of nitrogen (N) and copper (Cu) doping. We investigated the effect that doping has on both photoelectrochemical efficiency and surface properties by employing a variety of techniques spanning from impedance electrochemical impedance spectroscopy to ... -
Relationship between frequency power spectra and intermittent, large-amplitude bursts in the Alcator C-Mod scrape-off layer
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-08-21)Fluctuations in the boundary region of the Alcator C-Mod tokamak have been analyzed using gas puff imaging data from a set of Ohmically heated plasma density scan experiments. It is found that the relative fluctuation amplitudes are modest and close to normally distributed at the separatrix but become increasingly larger and skewed towards the main chamber wall. The frequency power spectra are ... -
The relationship between small-scale and large-scale ionospheric electron density irregularities generated by powerful HF electromagnetic waves at high latitudes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2006-11-21)Satellite radio beacons were used in June 2001 to probe the ionosphere modified by a radio beam produced by the EISCAT high-power, high-frequency (HF) transmitter located near Tromsø (Norway). Amplitude scintillations and variations of the phase of 150- and 400-MHz signals from Russian navigational satellites passing over the modified region were observed at three receiver sites. In several papers ... -
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 ... -
Relative drift between black aurora and the ionospheric plasma.
(Journal article; Tidsskriftartikkel, 2005-07-27)Black auroras are recognized as spatially well-defined regions within uniform diffuse aurora where the optical emission is significantly reduced. Although a well studied phenomenon, there is no generally accepted theory for black auroras. One theory suggests that black regions are formed when energetic magnetospheric electrons no longer have access to the loss cone. If this blocking mechanism drifts ... -
RELAX: Representation Learning Explainability
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-11)Despite the significant improvements that self-supervised representation learning has led to when learning from unlabeled data, no methods have been developed that explain what influences the learned representation. We address this need through our proposed approach, RELAX, which is the first approach for attribution-based explanations of representations. Our approach can also model the uncertainty ...