Fakultet for naturvitenskap og teknologi: Nye registreringer
Viser treff 2001-2020 av 5445
-
Numerical Solution of the Parametric Diffusion Equation by Deep Neural Networks
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-05)We perform a comprehensive numerical study of the effect of approximation-theoretical results for neural networks on practical learning problems in the context of numerical analysis. As the underlying model, we study the machine-learning-based solution of parametric partial differential equations. Here, approximation theory for fully-connected neural networks predicts that the performance of the ... -
Quantification of the NA dependent change of shape in the image formation of a z-polarised fluorescent molecule using vectorial diffraction simulations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-19)The point spread function of a fixed fluorophore with its dipole axis colinear to the optical axis appears donut-shaped when seen through a microscope, and its light distribution in the pupil plane is radially polarized. Yet other techniques, such as photolithography, report that this same light distribution in the pupil plane appears as a solid spot. How can this same distribution lead to a spot ... -
Using 3D Convolutional Neural Networks for Real-time Detection of Soccer Events
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06)Developing systems for the automatic detection of events in video is a task which has gained attention in many areas including sports. More specifically, event detection for soccer videos has been studied widely in the literature. However, there are still a number of shortcomings in the state-of-the-art such as high latency, making it challenging to operate at the live edge. In this paper, we present ... -
Demystifying the Origin of Vibrational Coherence Transfer Between the S1 and T1 States of the Pt-pop Complex
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-01)We demonstrate that spin-vibronic coupling is the most significant mechanism in vibrational coherence transfer (VCT) from the singlet (S<sub>1</sub>) to the triplet (T<sub>1</sub>) state of the [Pt<sub>2</sub>(P<sub>2</sub>O<sub>5</sub>H<sub>2</sub>)<sub>4</sub>]<sup>4–</sup> complex. Our time-dependent correlation function-based study shows that the rate of intersystem crossing (<i>k</i><sub>ISC</sub>) ... -
Accurate X-ray Absorption Spectra near L- and M-Edges from Relativistic Four-Component Damped Response Time-Dependent Density Functional Theory
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-27)The simulation of X-ray absorption spectra requires both scalar and spin–orbit (SO) relativistic effects to be taken into account, particularly near L- and M-edges where the SO splitting of core p and d orbitals dominates. Four-component Dirac–Coulomb Hamiltonian-based linear damped response time-dependent density functional theory (4c-DR-TDDFT) calculates spectra directly for a selected frequency ... -
Performance Quantification of Icebreaker Operations in Ice Management by Numerical Simulations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-15)The paper addresses the problem of quantifying and assessing the effectiveness of icebreaker operations in ice management (IM) using a high-fidelity simulator. The numerical model includes an accurate geometric representation of an icebreaker, a cylindrical protected structure, and a synthetic ice environment. A set of key performance indicators (KPIs) are defined and proposed to quantify the ... -
An Evaluation on Diverse Machine Learning Algorithms for Hourly Univariate Wind Power Prediction in the Arctic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-23)Wind power forecasting is crucial for wind power systems, grid load balance, maintenance, and grid operation optimization. The utilization of wind energy in the Arctic regions helps reduce greenhouse gas emissions in this environmentally vulnerable area. In the present study, eight various models, seven of which are representative machine learning algorithms, are used to make 1, 2, and 3 step ... -
Estimating Radiative Forcing With a Nonconstant Feedback Parameter and Linear Response
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-06)A new algorithm is proposed for estimating time-evolving global forcing in climate models. The method is a further development of the work of Forster et al. (2013), <a href=https://doi.org/10.1002/jgrd.50174>https://doi.org/10.1002/jgrd.50174</a>, taking into account the non-constancy of the global feedbacks. We assume that the non-constancy of this global feedback can be explained as a time-scale ... -
Hydration dynamics and the future of small-amplitude afm imaging in air
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-23)Here, we discuss the effects that the dynamics of the hydration layer and other variables, such as the tip radius, have on the availability of imaging regimes in dynamic AFM—including multifrequency AFM. Since small amplitudes are required for high-resolution imaging, we focus on these cases. It is possible to fully immerse a sharp tip under the hydration layer and image with amplitudes similar to ... -
Unification of sparse Bayesian learning algorithms for electromagnetic brain imaging with the majorization minimization framework
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-01)Methods for electro- or magnetoencephalography (EEG/MEG) based brain source imaging (BSI) using sparse Bayesian learning (SBL) have been demonstrated to achieve excellent performance in situations with low numbers of distinct active sources, such as event-related designs. This paper extends the theory and practice of SBL in three important ways. First, we reformulate three existing SBL algorithms ... -
Linking sea ice deformation to ice thickness redistribution using high-resolution satellite and airborne observations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-04)An unusual, large, latent-heat polynya opened and then closed by freezing and convergence north of Greenland’s coast in late winter 2018. The closing presented a natural but well-constrained full-scale ice deformation experiment. We observed the closing of and deformation within the polynya with satellite synthetic-aperture radar (SAR) imagery and measured the accumulated effects of dynamic ... -
Cosheaves
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-21)The categories pCS(X,Pro(k)) of precosheaves and CS(X,Pro(k)) of cosheaves on a small Grothendieck site X, with values in the category Pro(k) of prok-modules, are constructed. It is proved that pCS(X,Pro(k)) satisfies the AB4 and AB5* axioms, while CS(X,Pro(k)) satisfies AB3 and AB5*. Homology theories for cosheaves and precosheaves, based on quasi-projective resolutions, are constructed and investigated. -
Joint optimization of an autoencoder for clustering and embedding
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-21)Deep embedded clustering has become a dominating approach to unsupervised categorization of objects with deep neural networks. The optimization of the most popular methods alternates between the training of a deep autoencoder and a k-means clustering of the autoencoder’s embedding. The diachronic setting, however, prevents the former to beneft from valuable information acquired by the latter. In ... -
seMLP: Self-Evolving Multi-Layer Perceptron in Stock Trading Decision Making
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-24)There is a growing interest in automatic crafting of neural network architectures as opposed to expert tuning to fnd the best architecture. On the other hand, the problem of stock trading is considered one of the most dynamic systems that heavily depends on complex trends of the individual company. This paper proposes a novel self-evolving neural network system called self-evolving Multi-Layer ... -
Revealing the Quasi-Periodic Crystallographic Structure of Self-Assembled SnTiS3 Misfit Compound
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-28)Chemical vapor transport synthesis of SnTiS3 yields a self-assembled heterostructure of two distinct constituent materials, the semiconductor SnS and the semimetal TiS2. The misfit layer compound, although thermodynamically stable, is structurally complex, and precise understanding of the structure is necessary for designing nanoengineered heterojunction compound devices or for theoretical studies. ... -
Determination of the Azimuthal Extent of Coherent E-Region Scatter Using the ICEBEAR Linear Receiver Array
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-03-07)The Ionospheric Continuous-wave E-region Bistatic Experimental Auroral Radar (ICEBEAR) is a VHF coherent scatter radar that operates with a field-of-view centered on 58°N, 106°W and measures characteristics of ionospheric E-region plasma density irregularities. The initial operations of ICEBEAR utilized a wavelength-spaced linear receiving array to determine the angle of arrival of the ionospheric ... -
Relativity as a Synthesis Design Principle: A Comparative Study of [3 + 2] Cycloaddition of Technetium(VII) and Rhenium(VII) Trioxo Complexes with Olefins
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-13)The difference in [3 + 2] cycloaddition reactivity between fac- [MO<sub>3</sub>(tacn)]<sup>+</sup> (M = Re, <sup>99</sup>Tc; tacn = 1,4,7-triazacyclononane) complexes has been reexamined with a selection of unsaturated substrates including sodium 4- vinylbenzenesulfonate, norbornene, 2-butyne, and 2-methyl-3-butyn-2-ol (2MByOH). None of the substrates was found to react with the Re cation in water ... -
Choosing Bad versus Worse: Predictions of Two-Photon-Absorption Strengths Based on Popular Density Functional Approximations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-26)We present a benchmark study of density functional approximation (DFA) performances in predicting the two-photon-absorption strengths in π-conjugated molecules containing electron-donating/-accepting moieties. A set of 48 organic molecules is chosen for this purpose, for which the two-photon-absorption (2PA) parameters are evaluated using different DFAs, including BLYP, PBE, B3LYP, PBE0, CAM-B3LYP, ... -
Investigating the Ubiquitous Presence of Nanometric Water Films on Surfaces
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-25)When we speak of nanometric water films on surfaces we are speaking about a truly ubiquitous phenomenon in nature. All surfaces exposed to ambient conditions are covered by a thin film of water that affects or mediates surface chemistry, general physical-chemical processes on surfaces, and even solid–solid interactions. We have investigated this phenomenon for over a decade by exploiting dynamic ... -
Improved Arctic Sea Ice Freeboard Retrieval From Satellite Altimetry Using Optimized Sea Surface Decorrelation Scales
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-18)A growing number of studies are concluding that the resilience of the Arctic sea ice cover in a warming climate is essentially controlled by its thickness. Satellite radar and laser altimeters have allowed us to routinely monitor sea ice thickness across most of the Arctic Ocean for several decades. However, a key uncertainty remaining in the sea ice thickness retrieval is the error on the sea surface ...