Artikler, rapporter og annet (matematikk og statistikk): Recent submissions
Now showing items 121-140 of 336
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Algebraforståelse blant studentene i brukerkurs i matematikk ved UiT
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-24)Ved Institutt for matematikk og statistikk UiT – Norges arktiske universitet ble Brukerkurset i matematikk høsten 2020 lagt om til et prosjektbasert emne og ny eksamensform med avsluttende muntlig gruppeeksamen. Et av målene for vår studie er å kartlegge ferdigheter og forståelse i algebra i begynnelsen av semesteret og hvordan studentene videre møter de algebraiske aktivitetene i prosjektene. I ... -
The Tipping Effect of Delayed Interventions on the Evolution of COVID-19 Incidence
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-23)We combine infectious disease transmission and the non-pharmaceutical (NPI) intervention response to disease incidence into one closed model consisting of two coupled delay differential equations for the incidence rate and the time-dependent reproduction number. The model contains three parameters, the initial reproduction number, the intervention strength, and the response delay. The response is ... -
Convergence and completeness for square-well Stark resonant state expansions
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-02)In this paper, we investigate the completeness of the Stark resonant states for a particle in a square-well potential. We find that the resonant state expansions for target functions converge inside the potential well and that the existence of this convergence does not depend on the depth of the potential well, <i>V</i><sub>0</sub>. By analyzing the asymptotic form of the terms in these expansions, ... -
Constructing a partially transparent computational boundary for UPPE using leaky modes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-19)In this paper, we introduce a method for creating a transparent computational boundary for the simulation of unidirectional propagation of optical beams and pulses using leaky modes. The key element of the method is the introduction of an artificial-index material outside a chosen computational domain and utilization of the quasi-normal modes associated with such artificial structure. The method is ... -
Symmetric ideals, Specht polynomials and solutions to symmetric systems of equations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-18)An ideal of polynomials is symmetric if it is closed under permutations of variables. We relate general symmetric ideals to the so called Specht ideals generated by all Specht polynomials of a given shape. We show a connection between the leading monomials of polynomials in the ideal and the Specht polynomials contained in the ideal. This provides applications in several contexts. Most notably, this ... -
Instance Segmentation of Microscopic Foraminifera
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-16)Foraminifera are single-celled marine organisms that construct shells that remain as fossils in the marine sediments. Classifying and counting these fossils are important in paleo-oceanographic and -climatological research. However, the identification and counting process has been performed manually since the 1800s and is laborious and time-consuming. In this work, we present a deep learning-based ... -
Classification of Simply-Transitive Levi Non-Degenerate Hypersurfaces in C^3
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-24)Holomorphically homogeneous Cauchy–Riemann (CR) real hypersurfaces M<sup>3</sup>⊂C<sup>2</sup> were classified by Élie Cartan in 1932. In the next dimension, we complete the classification of simply-transitive Levi non-degenerate hypersurfaces M<sup>5</sup>⊂C<sup>3</sup> using a novel Lie algebraic approach independent of any earlier classifications of abstract Lie algebras. Central to our approach ... -
Estimation of Excess Mortality and Years of Life Lost to COVID-19 in Norway and Sweden between March and November 2020
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-08)We estimate the weekly excess all-cause mortality in Norway and Sweden, the years of life lost (YLL) attributed to COVID-19 in Sweden, and the significance of mortality displacement. We computed the expected mortality by taking into account the declining trend and the seasonality in mortality in the two countries over the past 20 years. From the excess mortality in Sweden in 2019/20, we estimated ... -
Machine Learning in Chronic Pain Research: A Scoping Review
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-02)Given the high prevalence and associated cost of chronic pain, it has a significant impact on individuals and society. Improvements in the treatment and management of chronic pain may increase patients’ quality of life and reduce societal costs. In this paper, we evaluate state-of-the-art machine learning approaches in chronic pain research. A literature search was conducted using the PubMed, IEEE ... -
Modelling suggests limited change in the reproduction number from reopening Norwegian kindergartens and schools during the COVID-19 pandemic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-25)<i>Background</i> - To suppress the COVID-19 outbreak, the Norwegian government closed all schools on March 13, 2020. The kindergartens reopened on April 20, and the schools on April 27 and May 11 of 2020. The effect of these measures is largely unknown since the role of children in the spread of the SARS-CoV-2 virus is still unclear. There are only a few studies of school closures as a separate ... -
De-identifying Swedish EHR text using public resources in the general domain
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020)Sensitive data is normally required to develop rule-based or train machine learning-based models for de-identifying electronic health record (EHR) clinical notes; and this presents important problems for patient privacy. In this study, we add non-sensitive public datasets to EHR training data; (i) scientific medical text and (ii) Wikipedia word vectors. The data, all in Swedish, is used to train a ... -
Challenges and opportunities beyond structured data in analysis of electronic health records
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-14)Electronic health records (EHR) contain a lot of valuable information about individual patients and the whole population. Besides structured data, unstructured data in EHRs can provide extra, valuable information but the analytics processes are complex, time-consuming, and often require excessive manual effort. Among unstructured data, clinical text and images are the two most popular and important ... -
Higher weight spectra of codes from Veronese threefolds
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-23)We study binary linear codes C obtained from the quadric Veronese embedding of P<sup>3</sup> in P<sup>9</sup> over F<sub>2</sub>. We show how one can find the higher weight spectra of these codes. Our method will be a study of the Stanley-Reisner rings of a series of matroids associated to each code <i>C</i>. -
Joint Invariants of Linear Symplectic Actions
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-07)We review computations of joint invariants on a linear symplectic space, discuss variations for an extension of group and space and relate this to other equivalence problems and approaches, most importantly to differential invariants. -
Differential Invariants of Linear Symplectic Actions
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-07)We consider the equivalence problem for symplectic and conformal symplectic group actions on submanifolds and functions of symplectic and contact linear spaces. This is solved by computing differential invariants via the Lie-Tresse theorem. -
Vaccination criteria based on factors influencing COVID-19 diffusion and mortality
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-15)SARS-CoV-2 is highly contagious, rapidly turned into a pandemic, and is causing a relevant number of critical to severe life-threatening COVID-19 patients. However, robust statistical studies of a large cohort of patients, potentially useful to implement a vaccination campaign, are rare. We analyzed public data of about 19,000 patients for the period 28 February to 15 May 2020 by several mathematical ... -
G(3)-supergeometry and a supersymmetric extension of the Hilbert–Cartan equation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-23)We realize the simple Lie superalgebra <i>G</i>(3) as supersymmetry of various geometric structures, most importantly super-versions of the Hilbert–Cartan equation (SHC) and Cartan's involutive PDE system that exhibit <i>G</i>(2) symmetry. We provide the symmetries explicitly and compute, via the first Spencer cohomology groups, the Tanaka–Weisfeiler prolongation of the negatively graded Lie ... -
Hyperspectral imaging for the detection of glioblastoma tumor cells in H&E slides using convolution neural networks
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-30)Hyperspectral imaging (HSI) technology has demonstrated potential to provide useful information about the chemical composition of tissue and its morphological features in a single image modality. Deep learning (DL) techniques have demonstrated the ability of automatic feature extraction from data for a successful classification. In this study, we exploit HSI and DL for the automatic differentiation ... -
Towards detection and classification of microscopic foraminifera using transfer learning
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-06)<p>Foraminifera are single-celled marine organisms, which may have a planktic or benthic lifestyle. During their life cycle they construct shells consisting of one or more chambers, and these shells remain as fossils in marine sediments. Classifying and counting these fossils have become an important tool in e.g. oceanography and climatology. <p>Currently the process of identifying and counting ... -
Snow avalanche segmentation in SAR images with Fully Convolutional Neural Networks
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-10)Knowledge about frequency and location of snow avalanche activity is essential for forecasting and mapping of snow avalanche hazard. Traditional field monitoring of avalanche activity has limitations, especially when surveying large and remote areas. In recent years, avalanche detection in Sentinel-1 radar satellite imagery has been developed to improve monitoring. However, the current state-of-the-art ...