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Browsing Fakultet for naturvitenskap og teknologi by Title
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Flåten, Ola; Mjølhus, Einar (Working paper; Arbeidsnotat, Feb-2006)[+][-]
Abstract: This paper demonstrates analytically how a nature reserve may protect the total population, realize maximum sustainable yield (MSY), maximum economic yield (MEY) and consumer surplus (CS) and how this depends on biological growth, migration, reserve size and economic parameters. The pre-reserve population is assumed to follow the logistic growth law and two post-reserve growth models are discussed. For Model A, the post-reserve growth has a common carrying capacity as in the pre-reserve case. In Model B, each sub-population has its own carrying capacity proportionate to its distribution area. Population protection against extinction is assured against low cost harvesting, including zero cost, when relative reserve size is greater than relative migration. Reserve size may be tuned to realize MSY in Model A, but not in Model B. MEY can not be realized in any of the two models, but generally economic yield is greater in Model A than B. CS is greater with a reserve than without. URI: http://hdl.handle.net/10037/939 File(s) in this item: 1
article.pdf (811.5Kb) -
Østerpart, Jørgen Olai Kristensen (Master thesis; Mastergradsoppgave, Feb-2011)[+][-]
Abstract: Using a resonance lidar, atomic Na (sodium) can be observed in the 80-110 km altitude range of the atmosphere. Na belongs to the alkali metal group and is highly reactive, so one could expect that it would quickly react with other particles and leave its atomic state. Its actual behaviour however includes the formation of relatively dense layers which, from the perspective of a stationary lidar, form suddenly and can last for several hours before quickly disappearing again. Several theories on the formation of these layers have been developed, including temperature dependent chemical processes, but none of them seem to explain all of the observed events. In 2008, two articles about these sudden sodium layers were published by scientists who have worked with the Weber Na lidar at the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR), located at Andøya, Norway \((69^{\circ} 16' N, 16^{\circ} 00' E)\). Nesse et al. (2008) describe one particular Na layer observed 5 November 2005 and consider in turn how the most probable theories match the observed data during this event. Heinrich et al. (2008) identify all the sudden Na layers that have been observed on ALOMAR between August 2000 and June 2006 and investigate in particular how these coincide with sporadic E-layers (thin layers of several types of metallic ions). The fourth ECOMA (Existence and Charged State of Meteoric Smoke Particles in the Middle Atmosphere) rocket campaign took place at the Andøya Rocket Range during November and December 2010. The Na lidar was operated to the extent possible during this period, resulting in near real-time data for two of the three rocket launches and a total of 48 hours of measurements which are presented in this text. Using the two formerly mentioned articles as a starting point, I have studied available theory about sudden Na layers and the ALOMAR Na lidar in particular, and the upper atmosphere and resonance lidars in general. While we did not observe any sudden Na layers during the ECOMA measurements, I look into an older dataset as an example. URI: http://hdl.handle.net/10037/3363 File(s) in this item: 1
thesis.pdf (1.327Mb) -
Ha, Hoai Phuong; Tsigas, Philippas; Anshus, Otto J. (Research report; Forskningsrapport, Oct-2008)[+][-]
Abstract: This paper addresses the problem of universal synchronization primitives that can support scalable thread synchronization for large-scale many-core architectures. The universal synchronization primitives that have been deployed widely in conventional architectures, are the compare-and-swap (CAS) and load-linked/store-conditional (LL/SC) primitives. However, such synchronization primitives are expected to reach their scalability limits in the evolution to many-core architectures with thousands of cores.
We introduce a non-blocking full/empty bit primitive, or NB-FEB for short, as a promising synchronization primitive for parallel programming on may-core architectures. We show that the NB-FEB primitive is universal, scalable, feasible and convenient to use. NB-FEB, together with registers, can solve the consensus problem for an arbitrary number of processes (universality). NB-FEB is combinable, namely its memory requests to the same memory location can be combined into only one memory request, which consequently mitigates performance degradation due to synchronization "hot spots" (scalability). Since NB-FEB is a variant of the original full/empty bit that always returns a value instead of waiting for a conditional flag, it is as feasible as the original full/empty bit, which has been implemented in many computer systems (feasibility). The original full/empty bit is well-known as a special-purpose primitive for fast producer-consumer synchronization and has been used extensively in the specific domain of applications. In this paper, we show that NB-FEB can be deployed easily as a general-purpose primitive. Using NB-FEB, we construct a non-blocking software transactional memory system called NBFEB-STM, which can be used to handle concurrent threads conveniently. NBFEB-STM is space efficient: the space complexity of each object updated by N concurrent threads/transactions is Θ(N), the optimal.URI: http://hdl.handle.net/10037/2563 File(s) in this item: 1
report.pdf (256.8Kb) -
Holmstad, Øyvind; Kreutzer, Tor (Research report; Forskningsrapport, 2011)[+][-]
Abstract: This report presents the results of the research conducted by Tor Kreutzer and Ø yvind Holmstad during the summer of 2011 at the University of Troms ø. The goal of the project was to gain practical experience with Near Field Communication (NFC) technology by exploring its properties through hands-on development of applications and services. To explore the applicability and limitations of NFC we have developed a range of diff erent prototype applications and services that utilize the technology in di fferent ways. The applications are mainly implemented on the Android mobile platform, but many of them communicate with servers running on traditional computers. The applications vary widely, from the simple Tagger which can read and write NFC tags, to NFC Presenter which uses NFC to simplify the process of starting presentations from your mobile device. NFC Safari uses the user's location to identify the closest sightseeing spot, and from there on takes him on a city safari. Applications like PartyShare and Are You the One? explores how powerful NFC can be in a social setting. Detailed descriptions and implementation details of all applications can be found in chapter 4. URI: http://hdl.handle.net/10037/4123 File(s) in this item: 1
article.pdf (1.445Mb) -
Kruglikov, Boris (Working paper; Arbeidsnotat, 2000)[+][-]
Abstract: In this paper we consider the normal forms of almost complex structures in a neighborhood of pseudoholomorphic curve. We define normal bundles of such curves and study the properties of linear bundle almost complex structures. We describe 1-jet of the almost complex structure along a curve in terms of its Nijenhuis tensor. For pseudoholomorphic tori we investigate the problem of pseudoholomorphic foliation of the neighborhood. We get some results on nonexistence of the tori deformation. URI: http://hdl.handle.net/10037/2154 File(s) in this item: 1
article.pdf (332.7Kb) -
Akbari, Vahid; Eltoft, Torbjørn; Doulgeris, Anthony Paul (Conference object; Konferansebidrag, 2010)[+][-]
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Doulgeris, Anthony Paul (Doctoral thesis; Doktorgradsavhandling, 18-Feb-2011)[+][-]
Abstract: This thesis describes general methods to analyse polarimetric synthetic aperture radar images, with the primary application of unsupervised image segmentation. The fundamental physics of electromagnetic scattering from distributed targets leads to the image phenomenon called speckle. Speckle is shown to be potentially non-Gaussian and several statistical distributions are investigated. Non-Gaussianity and polarimetry both hold pertinent information about the target medium and methods that utilise both attributes are developed. Two approaches are proposed: a local feature extraction method; and a model-based clustering algorithm. The local feature extraction approach creates a new six-dimensional description of the image by extending standard polarimetric features with a non-Gaussianity measure. Importantly, the non-Gaussianity measure is model independent and therefore does not unduly constrain the analysis. This may be used for subsequent image analysis or for physical parameter extraction, and unsupervised image segmentation is demonstrated with good results. The model-based approach describes a Bayesian clustering algorithm for the K-Wishart model and incorporates both non-Gaussianity and polarimetry. The initial implementation required several key parameters to be given in advance. When compared to the more common Wishart model, the K-Wishart gives similar results for Gaussian image regions, but performs better for non-Gaussian regions. Further development of the model-based method resulted in a novel technique to automatically determine the number of distinct classes supported by the data, given the model and a statistical confidence level. All relevant parameters are subsequently estimated within the algorithm and no special initialisation is required. These are significant advances from existing methods, where key parameters are predetermined and the number of classes are found after many full clustering results are obtained. The methods are general and apply to all coherent imaging systems that exhibit product model based statistics. The methods are demonstrated on several real radar images and with different numbers of polarimetric channels. Description: Paper number 2 of the thesis is not available in Munin due to publisher's restrictions:
Anthony P. Doulgeris, Stian Normann Anfinsen and Torbjørn Eltoft: ’Classification With a Non-Gaussian Model for PolSAR Data’, IEEE transactions on geoscience and remote sensing (2008), vol. 46, no. 10, pp. 2999-3009 Available at http://dx.doi.org/ 10.1109/TGRS.2008.923025URI: http://hdl.handle.net/10037/2962 File(s) in this item: 3
paper1.pdf (14.58Mb)paper3.pdf (2.733Mb)thesis.pdf (957.5Kb) -
Larsen, Reidulv; Berger, Steinar (Book; Bok, Mar-2000)[+][-]
Abstract: Reidulv Larsen og Steinar Berger tilbragte begge det meste av sitt yrkesaktive liv på Nordlysobservatoriet, fra 1940-tallet og fram mot 1990. Gjennom et så langt tidsrom oppsamles et betydelig forråd av kunnskap om institusjonens liv og historie og minner fra arbeidet der. Dette heftet har form av en historisk oversikt, men gjør ikke krav på å være en komplett eller objektiv sådann. URI: http://hdl.handle.net/10037/4392 File(s) in this item: 1
book.pdf (2.290Mb) -
Brekke, Asgeir (Chronicle; Kronikk, 2011)[+][-]
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Vorren, Tore Ola; Laberg, Jan Sverre (Chronicle; Kronikk, 14-Aug-2010)[+][-]
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Vanneste, Maarten; Mienert, Jurgen; Bünz, Stefan; Haflidason, H (Journal article; Tidsskriftartikkel; Peer reviewed, 2010)[+][-]
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Kilen, Isak Ragnvald (Master thesis; Mastergradsoppgave, 19-Jun-2012)[+][-]
Abstract: In this thesis a set of regularized boundary integral equation are introduced that can be used to calculate the Casimir force induced by a two dimensional scalar field. The boundary integral method is compared to the functional integral method and mode summation where possible. Comparisons are done for the case of two parallel plates, two concentric circles and two adjacent circles. The results indicate that the boundary integral method correctly predicts the geometry dependence of the Casimir force on the test problems, but that its value is missing a factor of two compared to the functional integral method and mode summation. After applying various validation procedures on the numerical implementation including a powerful test based on artificial sources, it is concluded that with high probability the missing factor of two is lost somewhere in the theory leading up to the regularized boundary integral equations. URI: http://hdl.handle.net/10037/4376 File(s) in this item: 1
thesis.pdf (1.130Mb) -
Kube, Ralph Arthur (Master thesis; Mastergradsoppgave, May-2010)[+][-]
Abstract: Numerical studies of radial filament motions in the SOL of toroidally confined plasmas are studies. We use a two dimensional two-field model to characterize blob-like structures in the radial-poloidal domain. These structures are observed to achieve velocities in the order of the ion acoustic velocity in the SOL of tokamaks and other toroidal confinement devices. By numerical means we find a scaling of the radial blob velocity that is inversely proportional to the square of the characteristic blob length. Comparison to an analytic solution show that the analytic solutions overestimates radial blob velocities. We also compare the numerical studies to experimental results and find good agreement. URI: http://hdl.handle.net/10037/2573 File(s) in this item: 2
errata (2).pdf (94.88Kb)thesis_opt.pdf (2.910Mb) -
Simonsen, Geir (Master thesis; Mastergradsoppgave, Apr-2010)[+][-]
Abstract: I avhandlingen prøver jeg å vise hvordan nær-othhogonale eksperimenter kan brukes i screeningforsøk URI: http://hdl.handle.net/10037/2476 File(s) in this item: 1
thesis.pdf (1.903Mb) -
Hansen, Lars Kr; Perlovich, German; Bauer-Brandl, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2006)[+][-]
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Hanssen, Øyvind (Master thesis; Mastergradsoppgave, 1994)[+][-]
Abstract: I denne hovedfagsavhandlinga undersøkes avbildningsmekanismer mellom ANSAware applikasjoner og en føderativ omgivelse. Dette gjøres innefor rammen av ODS-gruppas arbeid med samvirkende informasjonssystemer. For å få kunnskap om problemområdet og om hvordan avbildning effektivt kan utføres, utvikles et rammeverk for modellering, design og implementasjon av avbildningsmekanismer. Vi fokuserer spesielt på hvordan man i føderasjonen kan gi inntrykk av ANSAware objekter som persistente. Vi baserer oss på en persistensmodell som innebærer at vi stiller ulike krav til objekt-identitet. Vi trenger bare permanent identitet for noen få objekter. For disse er det behov for mekanismer for transparent forvaltning (aktivisering/passivisering). Vi undersøker to logiske komponenter som samarbeider om avbildning: Objekt-adapter som har ansvaret for forvaltning og objekt-identitet og språkbindinger som representerer programmeringsgrensesnitt for den aktuelle klient-omgivelse og realiserer aksess-transparens ved hjelp av stubs. Vi innfører begrepet proxy-objekt som representerer identifikasjon av objekter i objekt-adapter og presenterer en konseptuell modell for interaksjon med klient. Et gjenbrukbart objekt-orientert rammeverk er realisert. Dette representerer design og delvis implementasjon av objekt-adapter. Denne påbygges med applikasjonsspesifikk software for å bli komplett. En notasjon for definisjon av forvaltning av permanente objekter blir utviklet. Egenskaper ved språkbindinger blir undersøkt. Her gjøres et skille mellom direkte binding hvor klient er i samme prosess og binding via eksplisistt grensesnitt (kanonisk språk). Ei språkbinding til C++ er realisert, og det er skissert et rammeverk for binding til FRIL som er et funksjonelt og objektorientert språk for integrasjon og samvirke mellom ulike informasjonssystemer. Description: Dette er en hovedoppgave URI: http://hdl.handle.net/10037/1248 File(s) in this item: 1
thesis.pdf (2.110Mb) -
Grydeland, Tom (Master thesis; Mastergradsoppgave, 01-Mar-1998)[+][-]
Abstract: The thesis describes observations of strongly enhanced incoherent scatter plasma lines in the auroral ionosphere which were made with the EISCAT UHF radar in 1985. The linear theory of plasma instabilities is reviewed, and several possible explanations are discussed. The observations were found to be of insufficient resolution to unambiguously resolve which one would be the correct explanation. Finally, a new radar experiment design capable of making observations with higher resolution was realised and is presented in some detail. URI: http://hdl.handle.net/10037/239 File(s) in this item: 2
appendix.pdf (10.72Mb)thesis.pdf (1.166Mb) -
Valladares, C.E.; Van Eyken, A.P.; Alcaydé, D.; Rodriguez, J.V.; Ruohoniemi, J.M. (Journal article; Peer reviewed, 1999)[+][-]
Abstract: We report important results of the first campaign specially designed to observe the formation and the initial convection of polar cap patches. The principal instrumentation used in the experiments comprised the EISCAT, the Sondrestrom, and the Super DARN network of radars. The experiment was conducted on February 18, 1996 and was complemented with additional sensors such as the Greenland chain of magnetometers and the WIND and IMP-8 satellites. Two different types of events were seen on this day, and in both events the Sondrestrom radar registered the formation and evolution of large-scale density structures. The first event consisted of the passage of traveling convection vortices (TCV). The other event occurred in association with the development of large plasma jets (LPJ) embedded in the sunward convection part of the dusk cell. TCVs were measured, principally, with the magnetometers located in Greenland, but were also confirmed by the line-of-sight velocities from the Sondrestrom and SuperDARN radars. We found that when the magnetic perturbations associated with the TCVs were larger than 100 nT, then a section of the high-latitude plasma density was eroded by a factor of 2. We suggest that the number density reduction was caused by an enhancement in the O+ recombination due to an elevated Ti, which was produced by the much higher frictional heating inside the vortex. The large plasma jets had a considerable (>1000 km) longitudinal extension and were 200-300 km in width. They were seen principally with the Sondrestrom, and SuperDARN radars. Enhanced ion temperature (Ti) was also observed by the Sondrestrom and EISCAT radars. These channels of high Ti were exactly collocated with the LPJs and some of them with regions of eroded plasma number density. We suggest that the LPJs bring less dense plasma from later local times. However, the recent time history of the plasma flow is important to define the depth of the density depletion. Systematic changes in the latitudinal location and in the intensity of the LPJs were observed in the 2 min time resolution data of the SuperDARN radars. The effect of the abrupt changes in the LPJs location is to create regions containing dayside plasma almost detached from the rest of the oval density. One of these density features was seen by the Sondrestrom radar at 1542 UT. The data presented here suggest that two plasma structuring mechanisms (TCVs and LPJs) can act tens of minutes apart to produce higher levels of density structures in the near noon F-region ionosphere. URI: http://hdl.handle.net/10037/609 File(s) in this item: 1
article.pdf (1.289Mb) -
Henriksen, K.; Rees, D.; Smith, R.W.; Signernes, F.; Brandstrom, U.; Harris, M.; Maskall, G. (Journal article, 1998)[+][-]
Abstract: Two Doppler imaging systems (DIS) or wide-field imaging Fabry-Perot interferometers (FPI), have recently been commissioned, one at the Auroral Station, Adventdalen, Longyearbyen, Svalbard, and the second at the IRF, Kiruna, Sweden. These instruments can provide wide-field (600 * 800 km) images of neutral wind flows in the upper thermosphere, by measuring the Doppler shift of the atomic oxygen forbidden near 630 nm, which is emitted from an altitude of approximately 240 km. From the instrument in Svalbard, at mid-winter, it is possible to observe the dayside polar cusp and the polar cap throughout the entire day, whereas from Kiruna, the night-time auroral oval is observable during the hours of darkness. Measurements of thermospheric dynamics from the DIS can be used in conjunction with observations of ionospheric plasma flows and thermal plasma densities by the EISCAT-Svalbard radar (ESR) and by EISCAT, along with other complementary observations by co-located instruments such as the auroral large-scale imaging system (ALIS). Such combined data sets will allow a wide range of scientific studies to be performed concerning the dynamical response of the thermosphere and ionosphere, and the important energetic and momentum exchange processes resulting from their complex interactions. These processes are particularly important in the immediate vicinity of the polar cusp and within the auroral oval. Early results from Svalbard in late 1995 will be discussed. The DIS in Kiruna observed two interesting geomagnetic disturbances in early 1997, the minor geomagnetic storm of 10, 11 January, and the disturbed period from 7–10 February. During these events, the thermospheric wind response showed some interesting departures from the average behaviour, which we attribute to the result of strong and variable Lorenz forcing (ion drag) and Joule and particle heating during these geomagnetic disturbances. URI: http://hdl.handle.net/10037/567 File(s) in this item: 1
article.pdf (479.5Kb) -
Pless, Gustav (Master thesis; Mastergradsoppgave, 15-May-2009)[+][-]
Abstract: The high-resolution 3D seismic survey EL0001 allowed to document the subsurface fluid migration system and fluid accumulations within Veslemøy High, SW Barents Sea. Fluids migrate both through Cretaceous and Tertiary sediments, but also through younger glacial sediments. Veslemøy High is a structurally isolated high at the Cretaceous and Tertiary levels bounded by N-S trending west-dipping normal faults. Cretaceous to Miocene sediments that consists of deep marine shales dominate in the older part and Plio-Pleistocene successions deposited by glaciomarine processes dominate in the upper part. Fluid accumulations are identified in L. Paleocene to E. Eocene sediments, and in Pliocene to Pleistocene sediments of glacial origin. An extensive high-seismic amplitude anomaly of 790 km2 appears to occur in a fan system within the eastern section of the 3D survey extending into Tromsø Basin. High and negative seismic amplitudes indicate appreciable gas accumulations within the fan. On the seafloor the existence of pockmarks suggest that pockmark formation most likely occurred after the ice-sheet retreat and thus between 15 ka and 12.5-11.5 ka. Pockmarks may represent fluid flow events from violent eruptions associated with deglaciation processes. Some evidence exists that gas may have been generated in deeper basins. Fluids migrated into Veslemøy High primarily along Plio-Pleistocene strata from Sørvestsnaget Basin in the west and along Creataceous-Paleogene strata from Tromsø Basin in the east. As the fluids reach the apex of Veslemøy High vertical migration through giant chimneys and along normal faults dominate. It is important to note that there is no geophysical evidence for fluid migration from Cretaceous sediments that lie directly below the high. URI: http://hdl.handle.net/10037/1910 File(s) in this item: 1
thesis.pdf (9.943Mb)
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