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Extraordinary runoff from the Greenland ice sheet in 2012 amplified by hypsometry and depleted firn retention
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-05-30)It has been argued that the infiltration and retention of meltwater within firn across the percolation zone of the Greenland ice sheet has the potential to buffer up to ∼ 3.6 mm of global sea-level rise (Harper et al., 2012). Despite evidence confirming active refreezing processes above the equilibrium line, their impact on runoff and proglacial discharge has yet to be assessed. Here, we compare ... -
Scrape-off layer turbulence in TCV: Evidence in support of stochastic modelling.
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-01-28)Intermittent fluctuations in the TCV scrape-off layer have been investigated by analysing long Langmuir probe data time series under stationary conditions, allowing calculation of fluctuation statistics with high accuracy. The ion saturation current signal is dominated by the frequent occurrence of large-amplitude bursts attributed to filament structures moving through the scrape-off layer. The ... -
Access control protocol with node privacy in wireless sensor networks
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11-15)For preventing malicious nodes joining wireless sensor networks (WSNs), an access control mechanism is necessary for the trustworthy cooperation between the nodes. In addition to access control, recently, privacy has been an important topic regarding how to achieve privacy without disclosing the real identity of communicating entities in the WSNs. Based on elliptic curve cryptography, in this paper, ... -
Stochastic modelling of intermittent fluctuations in the scrape-off layer: Correlations, distributions, level crossings, and moment estimation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-05)A stochastic model is presented for intermittent fluctuations in the scrape-off layer of magnetically confined plasmas. The fluctuations in the plasma density are modeled by a super-position of uncorrelated pulses with fixed shape and duration, describing radial motion of blob-like structures. In the case of an exponential pulse shape and exponentially distributed pulse amplitudes, predictions are ... -
Secure and scalable statistical computation of questionnaire data in R
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-08-12)Collecting data via a questionnaire and analyzing them while preserving respondents' privacy may increase the number of respondents and the truthfulness of their responses. It may also reduce the systematic differences between respondents and non-respondents. In this paper, we propose a privacy- preserving method for collecting and analyzing survey responses using secure multi-party computation. The ... -
Human reliability assessment (HRA) in maintenance of production process: A case study
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-04-02)Human reliability makes a considerable contribution to the maintenance performance, safety, and cost-efficiency of any production process. To improve human reliability, the causes of human errors should be identified and the probability of human errors should be quantified. Analysis of human error is very case-specific; the context of the field should be taken into account. The aim of this study is ... -
Are there multiple scaling regimes in Holocene temperature records?
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-04-28)In this article it is discussed how temperature variability on centennial timescales and longer can be described in a simplistic way. By analysing the scaling in late Holocene temperature reconstructions and longer temperature records from Greenland and Antarctic ice cores, we find that the choice of model depends heavily on the data material and timescale one chooses to emphasize. Ignoring data ... -
Comment on "Scaling regimes and linear/nonlinear responses of last millennium climate to volcanic and solar forcing" by S. Lovejoy and C. Varotsos (2016)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-07-13)Lovejoy and Varotsos (2016) (L&V) analyse the temperature response to solar, volcanic, and solar plus volcanic forcing in the Zebiak–Cane (ZC) model, and to solar and solar plus volcanic forcing in the Goddard Institute for Space Studies (GISS) E2-R model. By using a simple wavelet filtering technique they conclude that the responses in the ZC model combine subadditively on timescales from 50 to ... -
Late Quaternary temperature variability described as abrupt transitions on a 1/f noise background
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-03-31)In order to have a scaling description of the climate system that is not inherently non-stationary, the rapid shifts between stadials and interstadials during the last glaciation (the Dansgaard-Oeschger events) cannot be included in the scaling law. The same is true for the shifts between the glacial and interglacial states in the Quaternary climate. When these events are omitted from a scaling ... -
Global warming projections derived from an observation-based minimal model
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-01-29)A simple conceptual model for the global mean surface temperature (GMST) response to CO2 emissions is presented and analysed. It consists of linear long-memory models for the GMST anomaly response 1T to radiative forcing and the atmospheric CO2-concentration response 1C to emission rate. The responses are connected by the standard logarithmic relation between CO2 concentration and its radiative ... -
Applicability Extent of 2-D Heat Equation for Numerical Analysis of a Multiphysics Problem
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-01)This work focuses on thermal problems, solvable using the heat equation. The fundamental question being answered here is: what are the limits of the dimensions that will allow a 3-D thermal problem to be accurately modelled using a 2-D Heat Equation? The presented work solves 2-D and 3-D heat equations using the Finite Difference Method, also known as the Forward-Time Central-Space (FTCS) method, ... -
Analytical and Case Studies of a Sandwich Structure using Euler-Bernoulli Beam Equation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11)This paper presents analytical and case studies of sandwich structures. In this study, the Euler-Bernoulli beam equation is solved analytically for a four-point bending problem. Appropriate initial and boundary conditions are specified to enclose the problem. In addition, the balance coefficient is calculated and the Rule of Mixtures is applied. The focus of this study is to determine the effective ... -
Wind Chill Effect in Cold Climate: Study of Wind Chill Effect Using Infrared Imaging
(Research report; Forskningsrapport, 2016)Wind chill factor is explained as the cooling sensation due to the exposure of wind temperature environment. The wind chill factor depends on air temperature, wind velocity and humidity. Wind chill poses serious health risks. Various wind chill index models are given in literature. In order to understand the wind chill effect, it is important to understand the phenomenon of heat transfer. There are ... -
Analytical Study of Sandwich Structures using Euler–Bernoulli Beam Equation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-01)This paper presents an analytical study of sandwich structures. In this study, the Euler–Bernoulli beam equation is solved analytically for a four-point bending problem. Appropriate initial and boundary conditions are specified to enclose the problem. In addition, the balance coefficient is calculated and the Rule of Mixtures is applied. The focus of this study is to determine the effective material ... -
Effects of substorm electrojet on declination along concurrent geomagnetic latitudes in the northern auroral zone
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-09-02)The geomagnetic field often experiences large fluctuations, especially at high latitudes in the auroral zones. We have found, using simulations, that there are significant differences in the substorm signature, in certain coordinate systems, as a function of longitude. This is confirmed by the analysis of real, measured data from comparable locations. Large geomagnetic fluctuations pose ... -
Delt situasjonsforståelse under søk og redning i nordområdene
(Research report; Forskningsrapport, 2016-05-03)Prosjektets mål er å bidra til økt kunnskap om hvordan etablere delt situasjonsforståelse mellom sentrale aktører innen SAR i Nordområdet. Prosjektgruppa har arbeidet ut ifra en menneske-teknologi-organisasjon (MTO) tilnærming og hvor vi har sett på <br>1) menneskelige og organisatoriske faktorer og <br>2) tekniske faktorer som virker inn på etableringen av delt situasjonsforståelse mellom aktører.<br> ... -
Shock Tube. Detail overview of equipment and instruments in the shock tube experimental setup
(Book; Bok, 2015)The shock tube is a device in which a normal shock wave is produced by the interaction of fluids at significantly high-pressure difference. The shock tube is comprised of two sections known as driver and driven sections. These two sections are interacted with the high-speed valve or a bursting disc. When the interaction happens, a shock wave forms almost instantaneously and propagates into the driven ... -
Empirical analysis of time-lagged cross-correlations in the Norwegian Stock Market. A discussion of the Efficient Market Hypothesis
(Master thesis; Mastergradsoppgave, 2016-12-15)In this thesis we challenge the existence of weak efficiency in the Norwegian Stock Marked, by analysing time-lagged cross-correlations between log-return series from 811 stocks listed on the Oslo stock exchange and by creating prediction strategies based on the discovered patterns. We limit the strategies to predicting the direction of the movements of the time series only, i.e. either generating ... -
Studies Towards the Synthesis of DKP Analogues. Investigations of Bis-lactim Ether Reactivity with Aldehydes and Ketones
(Master thesis; Mastergradsoppgave, 2016-05-19)A group of molecules with the name diketopiperazines (DKP) are called so, because of their diketopiperazine ring as the core structural unit. Mainly there are 3 types of diketopiperazies which only differ in in the position of the keto group, one type has the keto groups in 2,3- position; another in 2,5-; and the third in 2,6- position. The 2,5- isomer has attracted great interest, because of compounds ... -
Characterization and structural analysis of class D β-lactamases: variants and mutants of OXA-type carbapenemases
(Master thesis; Mastergradsoppgave, 2016-05-18)The rise and spread of antibiotic resistant bacteria is posing a serious threat to the global health; antibiotic drugs are rendered ineffective and common infectious diseases become harder or impossible to treat. The beta-lactamase enzymes, with their ability to hydrolyze the beta-lactam antibiotics, are a major cause of resistant bacteria. The OXA-beta-lactamase enzymes are one of the most alarming ...
