English
norskFakultet for naturvitenskap og teknologi: Recent submissions
Now showing items 4461-4480 of 5442
-
Group Based Asymmetry – A Fast Saliency Algorithm
(Chapter; Bokkapittel, 2015-12-18)In this paper, we propose a saliency model that makes two major changes in a latest state-of-the-art model known as group based asymmetry. First, based on the properties of the dihedral group D4 we simplify the asymmetry calculations associated with the measurement of saliency. This results is an algorithm which reduces the number of calculations by at-least half that makes it the fastest among the ... -
DeltaTree: A Locality-aware Concurrent Search Tree
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-06-15)Like other fundamental abstractions for high-performance computing, search trees need to support both high concurrency and data locality. However, existing locality-aware search trees based on the van Emde Boas layout (vEB-based trees), poorly support concurrent (update) operations. We present DeltaTree, a practical locality-aware concurrent search tree that integrates both locality-optimization ... -
Geophysical constraints on the dynamics and retreat of the Barents Sea ice sheet as a palaeobenchmark for models of marine icesheet deglaciation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-11-14)Our understanding of processes relating to the retreat of marine-based ice sheets, such as the West Antarctic Ice Sheet and tidewater-terminating glaciers in Greenland today, is still limited. In particular, the role of ice-stream instabilities and oceanographic dynamics in driving their collapse are poorly constrained beyond observational timescales. Over numerous glaciations during the Quaternary, ... -
Controls on gas hydrate system evolution in a region of active fluid flow in the SW Barents Sea
(Journal article; Tidsskriftartikkel, 2015-09)The location and stability of gas hydrates in the SW Barents Sea is poorly constrained due to complex geological, geochemical, and geophysical conditions, including poor controls on regional heat flow and gas chemistry. Understanding the stability of gas hydrates in this region is important, as recent studies suggest destabilizing hydrates may lead to methane discharge into the ocean and possibly ... -
Naturvitenskapens grunnlag og begrensning. Seminarrapport
(Research report; Forskningsrapport, 1979)Foredrag av Arthur E. Wilder-Smith og Udo Middelmann holdt ved NTH i 1979 -
Long-memory effects in linear response models of Earth's temperature and implications for future global warming
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014-07-15)A linearized energy-balance model for global temperature is formulated, featuring a scale-invariant longrange memory (LRM) response and stochastic forcing representing the influence on the ocean heat reservoir from atmospheric weather systems. The model is parameterized by an effective response strength, the stochastic forcing strength, and the memory exponent. The instrumental global surface ... -
Dørene lukkes for klimamålene
(Chronicle; Kronikk, 2015-11-10) -
Global warming projections derived from an observation-based minimal model
(Journal article; Tidsskriftartikkel, 2015-09-18)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 ∆T to radiative forcing and atmospheric CO2 - 5 concentration response ∆C to emission rate. The responses are connected by the standard logarithmic relation between CO2 concentration and its radiative ... -
Attribution in the presence of a long-memory climate response
(Journal article; Tidsskriftartikkel, 2015-08-10)Multiple, linear regression is employed to attribute variability in the global surface temperature to various forcing components and prominent internal climatic modes. The purpose of the study is to asses how sensitive attribution is to long-range memory 5 (LRM) in the model for the temperature response. The model response to a given forcing component is its fingerprint, and is different for a ... -
Are there multiple scaling regimes in Holocene temperature records?
(Journal article; Tidsskriftartikkel, 2015-07-17)The concept of multiple scaling regimes in temperature time series is examined, with emphasis on the question whether or not a mono-scaling model can be rejected from the data at hand. A model with only one regime is simpler and is preferred if this 5 explains the observed variability. Our analysis of spectra from reconstructed air temperature from Greenland and Antarctica ice cores shows that ... -
Spatiotemporal Long-Range Persistence in Earth’s Temperature Field: Analysis of Stochastic-Diffusive Energy Balance Models
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-11-01)A two-dimensional stochastic–diffusive energy balance model (EBM) formulated on a sphere by G. R. North et al. is explored and generalized. Instantaneous and frequency-dependent spatial autocorrelation functions and local temporal power spectral densities are computed for local sites and for spatially averaged surface temperature signals up to the global scale. On time scales up to the relaxation ... -
Late quaternary temperature variability described as abrupt transitions on a 1/f noise background
(Journal article; Tidsskriftartikkel, 2015-11-09)We show that in order to have a scaling description of the climate system that is not inherently non-stationary, the rapid shifts between stadial and interstadial conditions during the last glaciation cannot be included in the scaling law. The same is true for the 5 shifts between the glacial and interglacial states in the quaternary climate. When these events are omitted from a scaling analysis ... -
Short-Time Ice Drift and Deformation Measurements Using Multi-Mission Synethetic Aperture Radar
(Journal article; Tidsskriftartikkel, 2015-06)Norway is in a good position regarding frequent access to synthetic aperture radar data. A Norwegian– Canadian agreement provides large quotas of RADARSAT-2 images used operationally by e.g. the Norwegian Ice Service. More recently, Norway’s participation in the Copernicus program also allows rapid access to SENTINEL-1A data. By combining these data sources we can get satellite time series ... -
Seismic Modeling of Free Gas Occurrences and Bottom Simulation Reflection (BSR) Beneath Hydrate-bearing Sediments
(Master thesis; Mastergradsoppgave, 2016-01-17)This master thesis study uses seismic modeling to better understand the seismic response of the free gas that accumulates beneath hydrate-bearing sediments. To this end, I developed 12 different geological models ranging from very simple geometries to anticline structures. Within these models, I varied the distribution of free gas in the layers beneath the BSR. Sediment properties were taken from ... -
Stochastic modelling of intermittent scrape-off layer plasma fluctuations
(Master thesis; Mastergradsoppgave, 2015-05-15)In the tokamak scrape-off layer, radial motion of blob-like structures is the dominant mechanism for transport of particles and heat. Fixed point probe measurements in the Tokamak à Configuration Variable scrape-off layer reveal highly intermittent fluctuations in the ion saturation current. These measurements are well described by a shot noise process with exponential pulse shapes, exponentially ... -
Late Triassic channel systems at the Loppa High, SW Barents Sea
(Master thesis; Mastergradsoppgave, 2015-12-23)The study is based on the 3D seismic dataset (LN09M01). The study area is located in the southwest Barents Sea, south-western flank of the Loppa High. In the SW Barents Sea, the Middle to Late Triassic interval incorporates relatively thick and widespread fluvial system in the Snadd Formation, which is characterized by distinctive abundance of channel bodies of varying shape and extend. During ... -
Statistical Unmixing of SAR Images
(Journal article; Tidsskriftartikkel, 2016-02-03)A method is presented which uses logarithmic statistics to detect and characterise class mixtures and targets in background clutter in synthetic aperture radar (SAR) images. Mixtures of ground cover types show up as extreme radar texture in statistical analysis of SAR images. Instead of modelling this as a spatially nonstationary radar cross section, this paper demonstrates how a mixture model ... -
Vertical Diversity-Oriented Synthesis with Dibenzylideneacetones. Multivariate Optimization and Diversity Exploration.
(Master thesis; Mastergradsoppgave, 2015-05-18)DOS was planned from dibenzylideneacetone to generate compound library with structural diversity, which can undergo further transformations. In the presented work, dibenzylideneacetone was cyclized under Robinson Annulation reaction. The resulting cyclization product was optimized using Multivariate response surface method. Response surface analysis helped to determine both significant variables ... -
Overlevelsesanalyse med tidsavhengige forklaringsvariabler med bruk av Cox proporsjonal hasard regresjonsmodell
(Master thesis; Mastergradsoppgave, 2015-12-15)I denne mastergradsoppgaven ble det brukt overlevelsesanalyse med tidsavhengige variabler til å estimere en Cox proporsjonal hasard regresjonsmodell. Variablene stammet fra forskningsprosjektet ''Kvinner og kreft'' (The Norwegian Women and Cancer post genome cohort study - NOWAC) ved universitetet i Tromsø og besto av 57 561 kvinner. Modellen ble brukes til lage en modell av hasard raten til kvinnene ... -
Linear scaling Coulomb interaction in the multiwavelet basis, a parallel implementation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014-08-27)We present a parallel and linear scaling implementation of the calculation of the electrostatic potential arising from an arbitrary charge distribution. Our approach is making use of the multi-resolution basis of multiwavelets. The potential is obtained as the direct solution of the Poisson equation in its Green’s function integral form. In the multiwavelet basis, the formally non local ...
