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Browsing Fakultet for naturvitenskap og teknologi by Title
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Lychagin, Valentin V.; Goldberg, Vladislav V. (Journal article; Tidsskriftartikkel; Peer reviewed, 04-May-2006)[+][-]
Abstract: We find an invariant characterization of planar webs of maximum rank. For 4-webs, we prove that a planar 4-web is of maximum rank three if and only if it is linearizable and its curvature vanishes. This result leads to the direct web-theoretical proof of the Poincar´e’s theorem: a planar 4- web of maximum rank is linearizable. We also find an invariant intrinsic characterization of planar 4-webs of rank two and one and prove that in general such webs are not linearizable. This solves the Blaschke problem “to find invariant conditions for a planar 4-web to be of rank 1 or 2 or 3”. Finally, we find invariant characterization of planar 5-webs of maximum rank and prove than in general such webs are not linearizable. Description: Dette er forfatternes aksepterte versjon. URI: http://hdl.handle.net/10037/2049 File(s) in this item: 1
article.pdf (373.4Kb) -
Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)[+][-]
Abstract: Dedicated to the memory of Björn Roos (1937–2010), one of the fathers of modern multiconfigurational quantum chemistry, who also cared deeply about chemical applications, and a fun and inspiring friend to countless theoretically oriented chemists. URI: http://hdl.handle.net/10037/4086 File(s) in this item: 1
article.pdf (132.1Kb) -
Sudmann, Nils P.; Johansen, Dag (Research report; Forskningsrapport, 2000)[+][-]
Abstract: In this paper we will show that it is possible to combine mobile agent technology with existing non-mobile data mining applications. The motivation for this is the advantage mobile agents offer in moving the computation closer to the data in a distributed system. This can save bandwidth and increase performance when the data is condensed as a result of data mining. URI: http://hdl.handle.net/10037/357 File(s) in this item: 1
report.pdf (70.91Kb) -
Kluken, Lars Grytbakk (Master thesis; Mastergradsoppgave, 30-Sep-2011)[+][-]
Abstract: Temperatures at 90 km altitude above Ramfjordmoen (69°N, 19°E) have been obtained with the Nippon/Norwegian Tromsø Meteor Radar. The temperatures have been derived from meteor radar decay rates using two techniques: the pressure based and the temperature gradient based methods. The results have been compared to the Microwave Limb Sounder (MLS) instrument on board the Aura spacecraft. It was found that the pressure method was simpler to implement than the temperature gradient method and gave better results in relation to the MLS temperatures. With the use of a technique for statistical comparison of geophysical data, the intrinsic uncertainty of the radar temperatures was estimated to be less than 4 K. Two attempts to combine the two techniques in order to measure both temperatures and pressure with the meteor radar have been carried out. One of the approaches proved to be feasible and gave promising results. This indicates that the meteor radar may have the potential of producing continuous temperature and pressure measurements virtually independent of external data. A new collocated sodium lidar is introduced and some initial comparisons are carried out between the two instruments. At times there were large discrepancies, but more data is necessary in order to obtain reliable results. Finally, some possible uses of the radar temperatures are proposed. A method for investigating long term trends is discussed in detail. The data available resulted in a trend of - 2.2 K per decade, but more data is required to establish a trend with higher confidence. It was estimated that approximately 13 years of data are needed to determine the trend with a probability of 90 %. URI: http://hdl.handle.net/10037/3712 File(s) in this item: 1
thesis.pdf (3.063Mb) -
Ryeng, Kristoffer (Master thesis; Mastergradsoppgave, 01-Oct-2008)[+][-]
Abstract: Motivasjonen for denne oppgaven er en aktiv, smertefri og ufarlig metode for deteksjon av brystkreft ved bruk av ultrabredbånd mikrobølgeradar. Montering av lavstøyforsterker direkte etter mottakerantennen har en positiv effekt på signal-til-støyforholdet i radar-systemet, og en vesentlig del av oppgaven er å måle lavstøyforsterkeren gir. Grunnleggende teori om mikrobølger, antenner, forsterkere, støy og ultrabredbåndssystemer presenteres. Målesystemet som benyttes blir delvis karakterisert og tre radarsystemer blir presentert, monostatisk radar, bistatisk radar og bistatisk radar med tilkoplet lavstøyforsterker. De tre radarsystemene og deres evne til å detektere metalliske plan- og kulereflektorer ble så målt og vurdert. Alle radarsystemene detekterte planreflektoren på 37x40mm, men bare det monostatiske systemet klarte å detektere kulereflektoren med radius 15mm. Det skyldes blant annet at de bistatiske systemene har lenger signalvei, og en omfattende justering av systemene bør utføres for å redusere denne. Monteringen av aktivt element fikk mindre effekt enn forventet, trolig fordi cross-talk mellom sender- og mottakerantenne var så stor at forsterkeren gikk i metning. Det kan i såfall kompenseres med å sende mindre effekt, men vil ikke være en ideell løsning. Til tross for dette, er tilsynelatende faseinformasjonen i signalet beholdt, slik at man har fått resultater av målingene som er gjort med forsterkeren. Det skal dog ikke utelukkes at man fått større utbytte dersom forsterkeren hadde operert i sitt egentlige operasjonsområde. URI: http://hdl.handle.net/10037/1771 File(s) in this item: 1
thesis.pdf (4.525Mb) -
Winther, Henrik (Master thesis; Mastergradsoppgave, May-2012)[+][-]
Abstract: We classify the almost complex structures on homogeneous spaces M = G/H of real dimension less than or equal to 6 with semi-simple isotropy group H. URI: http://hdl.handle.net/10037/4372 File(s) in this item: 1
thesis.pdf (611.0Kb) -
Hall, Chris; Husøy, Bjørn Ove (Research report; Forskningsrapport, 2004)[+][-]
Abstract: Although the Tromsø Medium Frequency Radar situated at Ramfjordmoen, Norway (69°N, 19°E) has been operating for over a quarter of a century, no definitive altitude calibration has ever been documented using independent measurements of the same atmosphere. Here we perform calibrations using the recently installed (November 2003) Nippon/Norway Tromsø Meteor Radar by identifying wind features in the same volume. We also perform an independent check using oscilloscope measurements supplemented by an acoustic delay line. Description: This publication is the inaugural report in the series Tromsø Geophysical Observatory Reports. URI: http://hdl.handle.net/10037/2411 File(s) in this item: 1
article.pdf (983.8Kb) -
Nácher Rodríguez, María (Master thesis; Mastergradsoppgave, 25-Jun-2007)[+][-]
Abstract: In the present master thesis the dynamical behavior of the Mini-Dusty rockets will be analyzed with the aim to obtain accurate information on the absolute coning and orientation history during the flight, and in particular around all the critical phases. URI: http://hdl.handle.net/10037/1200 File(s) in this item: 1
thesis.pdf (5.801Mb) -
Fyhn, Anne Birgitte (Doctoral thesis; Doktorgradsavhandling, 13-Jun-2007)[+][-]
Abstract: The thesis enlightens how the choice of context as well as the approach to mathematics is important in introducing the concepts of angles. The analyses indicate that students should not be introduced to measuring angles before they are able to sort out angles according to their sizes. Angles can be introduced by use of the students’ bodies in a climbing context, where the word angle refers to bent shape. Climbing is an activity which to a large extent is experienced as exciting and fun. The idea is to base the teaching on the students’ talk about climbing. The teacher’s job is to guide the students to build up their understanding of angles as a tool for improved climbing technique. The students’ use of drawing and text in describing and explaining angles in a climbing context is analysed. These analyses indicate that the teaching should point out differences between narrative and analytical text and drawing and then the students’ analytical drawings can function as basis for their further work with geometry. The thesis focuses on students’ mathematising of climbing and on how the participating teachers relate to this activity. The analyses indicate that the teachers need some experience with inductive teaching of mathematics in some practical context before they are able to grasp the value of their students’ mathematising. Thus two DVDs are made. The first one shows how inductive physical geometry activities can function as basis for written and oral tasks in mathematics. The second DVD shows how students can mathematise climbing with respect to angles, and how experiences from one climbing situation can function as basis for adapting the teaching of angles to the students’ different levels of understanding. Description: DVD 1, which is part of the thesis introduction, is not made available in Munin due to restrictions in the Personal Data Act. URI: http://hdl.handle.net/10037/994 File(s) in this item: 8
climbingangles_2007_no.wmv (63.10Mb)climbingangles_2007.wmv (66.94Mb)dvd_info.pdf (75.34Kb)Paper_I.pdf (344.7Kb)(more files) -
Pflug, Alexander; Johnson, Kenneth; Engh, Richard Alan (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)[+][-]
Abstract: With its ability to show the interactions between drug-target proteins and small-molecule ligands, X-ray crystallography is an essential tool in drug-discovery programmes. However, its usefulness can be limited by crystallization artifacts or by the data resolution, and in particular when assumptions of unimodal binding (and isotropic motion) do not apply. Discrepancies between the modelled crystal structure and the physiological range of structures generally prevent quantitative estimation of binding energies. Improved crystal structure resolution will often not aid energy estimation because the conditions which provide the highest rigidity and resolution are not likely to reflect physiological conditions. Instead, strategies must be employed to measure and model flexibility and multiple binding modes to supplement crystallographic information. One useful tool is the use of anomalous dispersion for small molecules that contain suitable atoms. Here, an analysis of the binding of the kinase inhibitor H-89 to protein kinase A (PKA) is presented. H-89 contains a bromobenzene moiety that apparently binds with multiple conformations in the kinase ATP pocket. Using anomalous dispersion methods, it was possible to resolve these conformations into two distinct binding geometries. Description: This article is part of Alexander Pflugs' doctoral thesis, available in Munin at http://hdl.handle.net/10037/4145 URI: http://hdl.handle.net/10037/4645 File(s) in this item: 1
article.pdf (1.012Mb) -
Kruglikov, Boris (Chapter; Bokkapittel, 20-Dec-2007)[+][-]
Abstract: In this note we discuss some formal properties of universal linearization operator, relate this to brackets of non-linear differential operators and discuss application to the calculus of auxiliary integrals, used in compatibility reductions of PDEs. URI: http://hdl.handle.net/10037/2125 File(s) in this item: 1
article.pdf (153.4Kb) -
Leiros, Hanna-Kirsti S. (Conference object; Konferansebidrag, 02-Sep-2010)[+][-]
Description: Innlegg på seminaret "Science - who cares?" ved NT-fak, Universitetet i Tromsø. URI: http://hdl.handle.net/10037/2697 File(s) in this item: 1
article.pdf (2.376Mb) -
Hall, Chris (Journal article; Peer reviewed, 2001)[+][-]
Abstract: The Reynolds number Re is used as a metric to assess whether or not a flow may contain turbulence. In a weakly ionised gas with an external electric field imposed, ions exert a drag on the neutral particles. Thus, a component of the neutral motion is attributable to the ion-drag. An analogy to Re has been proposed in which the ion-drag-induced velocity contribution to the neutral motion is used. This analogy thus represents the destabilising effect of the electric field on the neutral dynamics. Here quantisation of this proposed metric is investigated. URI: http://hdl.handle.net/10037/575 File(s) in this item: 1
article.pdf (122.7Kb) -
Marzullo, Keith; Johansen, Dag; Lauvset, Kåre J. (Research report; Forskningsrapport, 1998)[+][-]
Abstract: We devise a mobile agent middleware architecture for supporting distributed applications in a wide-area network. The architecture provides a structural framework for functional components that are needed to support mobile agents in asymmetric networking environments. URI: http://hdl.handle.net/10037/363 File(s) in this item: 1
report.pdf (88.72Kb) -
Khalaila, Ahmad; Eliassen, Frank (Research report; Forskningsrapport, Apr-1997)[+][-]
Abstract: A large class of linear recursive queries compute the bill-of-materials of database relations.This paper presents a novel algorithm that computes the bill-of-materials of its argument's (database) relation. The algorithm uses a special join operation that accumulates the cost of composite parts, without constructing the transitive closure of the argument relation, thus saving time and space. We argue that this algorithm outperforms existent algorithms in the order of the diameter of the graph represented in the argument relation. This is made possible by exploiting knowledge of the level each tuple of the argument relation belongs to. Moreover, this algorithm in contrast to transitive closure based processing, produces data at a very early stage of the processing which renders it suitable for pipelined distributed data processing. URI: http://hdl.handle.net/10037/368 File(s) in this item: 1
report.pdf (249.6Kb) -
Johansen, Dag; Marzullo, Keith; Lauvset, Kåre J. (Research report; Forskningsrapport, 06-Oct-2000)[+][-]
Abstract: This paper presents a generic software architecture for large-scale distributed applications where mobile agents are an integral part. We have devised this architecture through completion of a series of mobile agent systems and associated applications over the last 8 years. URI: http://hdl.handle.net/10037/403 File(s) in this item: 1
report.pdf (185.9Kb) -
Grydeland, Tom; Chau, J.L.; La Hoz, C.; Brekke, Asgeir (Journal article; Peer reviewed, 31-Jan-2005)[+][-]
Abstract: Interferometric imaging (aperture synthesis imaging) is a technique used by radio astronomers to achieve angular resolution that far surpasses what is possible with a single large aperture. A similar technique has been used for radar imaging studies of equatorial ionospheric phenomena at the Jicamarca Radio Observatory. We present plans for adding an interferometric imaging capability to the EISCAT Svalbard Radar (ESR), a capability which will contribute significantly to several areas of active research, including naturally and artificially enhanced ion-acoustic echoes and their detailed relation in space and time to optical phenomena, polar mesospheric summer echoes (PMSE), and meteor studies. Interferometry using the two antennas of the ESR has demonstrated the existence of extremely narrow, fieldaligned scattering structures, but having only a single baseline is a severe limitation for such studies. Building additional IS-class antennas at the ESR is not a trivial task. However, the very high scattering levels in enhanced ion-acoustic echoes and PMSE means that a passive receiver antenna of more modest gain should still be capable of detecting these echoes. In this paper we present simulations of what an imaging interferometer will be capable of observing for different antenna configurations and brightness distributions, under ideal conditions, using two different image inversion algorithms. We also discuss different antenna and receiver technologies. URI: http://hdl.handle.net/10037/548 File(s) in this item: 1
article.pdf (334.7Kb) -
Isham, B.; Rietveld, Michael T.; Hagfors, T.; Belyey, Vasyl; Khudukon, B.; La Hoz, Cesar; Yurik, R.Yu; Brekke, Asgeir; Tereshchenko, E.D.; Grill, M.; Heinselman, C. (Journal article; Peer reviewed, 31-Jan-2005)[+][-]
Abstract: When the Earth's ionosphere is irradiated by a radiofrequency (RF) electromagnetic wave of sufficiently high power density and tuned to match a natural E- or F-region plasma frequency, ionospheric magnetoionic wave modes may be excited and may generate RF electromagnetic sideband waves via nonlinear interactions. These secondary emissions, which may then escape from the ionosphere, have been termed stimulated electromagnetic emission or SEE. The frequency spectra of this radiation has been studied extensively, and a number of characteristic spectral features have been identified and in some cases related to particular plasma processes. The separation in frequency between the RF pump and the harmonics of the local electron gyrofrequency is critical in determining the amount of anomalous absorption suffered by the pump wave and the spectral properties of the stimulated sidebands. The pump can excite electrostatic waves which do not propagate away but can in some cases be observed via radio-wave scattering from the electron density fluctuations associated with them. These enhanced density fluctuations are created by processes commonly referred to as upper-hybrid and Langmuir turbulence. Langmuir turbulence has been the subject of 930-MHz scattering observations with antenna scanning through several pre-selected angles between the geographic and geomagnetic zenith directions, and a preference for pointing angles between the Spitze angle and geomagnetic field-aligned was identified. Other phenomena, such as the generation of enhanced electron temperatures and artificial aurora, have more recently been shown to have special behavior at similar angles, near but apparently not quite at field-aligned. In view of this evidence for angular structure in several pump-induced effects, in light of the rich variety of SEE phenomena strongly dependent on the geomagnetic field via the frequency interval between the pump and the gyrofrequency harmonics, and in view of the not yet understood but complex relationship between electrostatic fluctuations and SEE, it is of interest to investigate experimentally whether a similar angular structure is present in the various spectral features of the SEE signals and to compare the results with radar and other observations of RF-pump-induced effects. To this end we describe a simple two-element radio interferometer designed to search for aspect angle dependence of SEE features. We present an example of the initial data produced by this system, and draw preliminary conclusions based on the example data. URI: http://hdl.handle.net/10037/565 File(s) in this item: 1
article.pdf (5.513Mb) -
Renesse, Robbert van; Johansen, Dag; Schneider, Fred B. (Research report; Forskningsrapport, Jun-1995)[+][-]
Abstract: This report briefly introduces TACOMA Version 1.0. This distributed system supports agents, computations that can roam the internet. The report presents the TACOMA project, the computational model, how to get started, and the basic TACOMA abstractions. URI: http://hdl.handle.net/10037/382 File(s) in this item: 1
report.pdf (129.2Kb) -
Larsen, Are (Master thesis; Mastergradsoppgave, 15-May-2009)[+][-]
Abstract: This work concentrates on using the ICM algorithm for image restoration. The algorithm has been applied to fMRI recordings and mole pictures URI: http://hdl.handle.net/10037/2071 File(s) in this item: 1
thesis.pdf (3.404Mb)
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