Infrastrukturbaserte 802.11 trådløse nett og 802.11i : nettverksoppgradering og performance-evaluering

IEEE 802.11i er en standard som spesifiserer sikkerhet i IEEE 802.11 trådløse nettverk. Denne oppgaven tar for seg oppgradering av infrastrukturbaserte 802.11 trådløse nettverk til 802.11i og ser på konsekvenser for brukeren. Throughput måles ved bruk av sikkerhetsmekanismen CCMP med standarden IEEE 802.1X for autentisering i stedet for WEP og forsøker å avdekke forskjeller i performance. De involverte standarder gjennomgås, oppgradering til 802.11i forklares, throughput måles og oppgradering og resultatene diskuteres. Forslag til anvendelsesområder gis. Oppgaven konkluderer med at CCMP benytter dobbelt så mange byte for å overføre informasjon nødvendig for sikkerhetsmekanismen som WEP, og at denne forskjellen i overhead lar seg måle selv for overføringer med store pakker

Quantifying the Market Value of Wave Power compared to Wind&Solar - a case study

This study discusses the market value of electricity production by different sustainable sources, and shows how it is influenced by the correlation between electricity market price and energy production. The generic discussion is accompanied by a case study comparing the value of wave, wind and solar power using time series data for production and prices generated by grid and market simulations. The study has shown that simplified common-practise approaches (which do not consider correlation) fail to correctly reveal the market value of electricity production. It has also been shown that wave power can achieve a market value that is significantly higher than wind and slightly higher than solar. These differences in market value have been explained through correlation between electricity production and price, which is different for different energy sources. The study has identified competitive advantages of wave power towards the dominant sustainable energy sources, that need to be taken into account when competitiveness and profitability are to be assessed.acceptedVersio

Sosial og faglig inkludering av barn med spesielle behov i barneskolen.

Denne studien undersøker problemstillingen: «Hvordan erfarer foreldre til barn med spesielle behov at barnet ble inkludert sosialt og faglig i barneskolen?». Formålet med denne studien har vært å kunne belyse hvordan foreldre erfarer denne inkluderingen og hvordan den har fungert. Hensikten var å kunne få frem hvilke erfaringer foreldrene sitter igjen med etter at det har gått mellom fire til åtte år etter endt barneskole for deres barn. I forlengelsen av dette, var hensikten å kunne avdekke og belyse områder hvor det var behov for forbedring. En ønskelig konsekvens er at denne studien vil kunne øke kunnskapen rundt hvordan lærere og ansatte ved skoler kan legge til rette for god inkludering av barn med spesielle behov. Problemstillingen besvares med bakgrunn i fire kvalitative forskningsintervjuer. Utvalget består av fire deltakere, med totalt fem barn i alderen 16-21 år. Disse barna hadde rett på spesialundervisning fra første til syvende klasse. Utvalget ble rekruttert fra sosiale medier og gjennom personlig nettverk. Overordnet gir funnene fra denne studien et bilde av hvordan den generelle inkluderingen av barnet var av varierende kvalitet. I studiens funn kommer det frem ulike momenter som bygger grunnlag for inkludering. Disse var: Kontakt med skolen, undervisning, kompetanse og elevsyn og vennskap. I de tilfellene hvor foreldrene var mindre fornøyde med inkluderingen av barnet, var disse momentene ikke til stede eller ikke så bra som forventet. På den andre siden, er disse momentene til stede hos foreldrene som hadde en positiv opplevelse av inkluderingen. Videre viser studien at det finnes faktorer som kan jobber mot inkludering. Dette var skoleledelse og samarbeid mellom instansene. Samlet sett indikerer funnene at det er en variasjon i foreldrenes opplevelse av barnets inkludering og at det er et forbedringspotensiale hos skolene i arbeidet med å inkludere barn med spesielle behov. Resultatene av denne studien belyser hva som kan jobbe mot inkludering og hva som må være til stede for å lykkes med inkludering

Association of area-level education with the regional growth trajectories of rates of antibacterial dispensing to patients under 3 years in Norway: a longitudinal retrospective study

Objective To examine the association between area-level education and the local growth trajectories in antibacterial dispensing rates in Norwegian municipalities among children under 3 years old. Design Retrospective, longitudinal study using individual primary care prescription data from the Norwegian Prescription Database for the period 2006–2016. Data were collected on the date of dispensing, the type and amount of antibiotic, the patient’s age, sex and municipality of residence and linked to municipality-level statistics on education available from Statistics Norway. We used multilevel growth curve modelling, with a linear trend variable modelled as a random effect and a cross-level interaction between linear trends and the proportion of the population in the municipality having received a university or college education. Setting The local government level in Norway. The sample includes all municipalities over the study period. Outcome measure Number of dispensed antibacterial prescriptions per 100 children in individual primary care by municipality and year. Results We identified a significant negative linear trend in the square root of the dispensing rate for children under 3 years old during the period. This trend varied between municipalities. A negative cross-level interaction term between population education levels and random trends showed that municipalities with an average level of population education saw a reduction in their square root dispensing rates of −0.053 (95% CI −0.066 to −0.039) prescriptions per 100 children. Each additional percentage point in population education contributed a further −0.0034 (95% CI −0.006 to –0.001) reduction to the square root dispensing rate. Conclusions Municipalities in which a larger proportion of the local population have high educational achievements have been more successful in reducing antibacterial dispensing rates in children under 3 years old. Adopting area-level strategies and addressing local community disadvantages may help to optimise practices and prescribing patterns across local communities

The Low Emission Oil and Gas Open reference platform—An off-grid energy system for renewable integration studies

The data that support the findings of this study are openly available in Zenodo at https://doi.org/10.5281/zenodo (7373223)This article introduces and describes the integrated energy system of the Low Emission Oil and Gas Open reference platform. It is a hypothetical case meant to represent a typical oil and gas installation in the North Sea. The aim of this detailed specification is to serve as an open reference case where all the information about it can be publicly shared, facilitating benchmarking and collaboration. The relevance of this reference case of an off-grid energy system is not limited to the oil and gas industry, since it can also be seen as a special kind of electrical micro grid. The remote offshore location makes it especially relevant for studying offshore wind power and ocean energy sources like wave power. The specification has an emphasis on the energy system and electrical configuration, but also includes a basic description of the oil field and processing system. The intention is that it will serve as a basis for energy system studies and relating power system stability analyses regarding the integration of renewable energy sources. This allows for comparisons of a base case with different design modifications, new operational planning methods, power management strategies and control concepts. Examples of possible modifications are the replacement of gas turbines by wind turbines, addition of energy storage systems, a more variable operation of loads etc. The last part of the article demonstrates the behaviour of the reference platform implemented in two software tools: one for operational planning and one for dynamic power system analyses.publishedVersio

Molecules in Real Cavities with Quantum Electrodynamical Density Functional Theory

Rapid experimental progress in realizing strongly coupled light-matter systems in complex electromagnetic environments necessitates the development of theoretical methods capable of treating light and matter from first principles. A popular such method is quantum electrodynamical density functional theory (QEDFT) which is a generalization of density functional theory to situations where the electronic system is coupled to quantized light modes. While this method provides a powerful description of the electronic system and the quantized modes of light, it has so far been unable to deal correctly with absorbing and dispersing electromagnetic media in practice. In addition, the cavity field strength parameters have not been linked to the real electromagnetic environment in which the matter is embedded meaning that these are effectively free parameters. In this paper, we discuss how macroscopic QED (MQED) can be invoked to correctly parameterize QEDFT for realistic optical cavity setups. To exemplify this approach, we consider the example of a absorbing spherical cavity and study the impact of different parameters of both the environment and the electronic system on the transition from weak-to-strong coupling. As a result of our work, the coupling parameters in general, lossy environments can be now expressed in terms of the classical Dyadic Green's Function. Because the Dyadic Green's Function is completely determined by the electromagnetic environment and the boundary conditions, it thus removes the light-matter coupling strengths as free parameters. As part of this work, we also provide an easy to use tool that can calculate the cavity coupling strengths for simple cavity setups

Indirect band gap semiconductors for thin-film photovoltaics: High-throughput calculation of phonon-assisted absorption

Discovery of high-performance materials remains one of the most active areas in photovoltaics (PV) research. Indirect band gap materials form the largest part of the semiconductor chemical space, but predicting their suitability for PV applications from first principles calculations remains challenging. Here we propose a computationally efficient method to account for phonon assisted absorption across the indirect band gap and use it to screen 127 experimentally known binary semiconductors for their potential as thin film PV absorbers. Using screening descriptors for absorption, carrier transport, and nonradiative recombination, we identify 28 potential candidate materials. The list, which contains 20 indirect band gap semiconductors, comprises both well established (3), emerging (16), and previously unexplored (9) absorber materials. Most of the new compounds are anion rich chalcogenides (TiS$_3$, Ga$_2$Te$_5$) and phosphides (PdP$_2$, CdP$_4$, MgP$_4$, BaP$_3$) containing homoelemental bonds, and represent a new frontier in PV materials research. Our work highlights the previously underexplored potential of indirect band gap materials for optoelectronic thin-film technologies

Signatures of Non-Markovianity in Cavity-QED with Color Centers in 2D Materials

Light-matter interactions of defects in two dimensional materials are expected to be profoundly impacted by strong coupling to phonons. In this work, we combine ab initio calculations of a defect in hBN, with a fully quantum mechanical and numerically exact description of a cavity-defect system to elucidate this impact. We show that even at weak light-matter coupling, the dynamical evolution of the cavity-defect system has clear signatures of non-markovian phonon effects, and that linear absorption spectra show the emergence of hybridised light-matter-phonon states in regimes of strong light-matter coupling. We emphasise that our methodology is general, and can be applied to a wide variety of material/defect systems.Comment: 7 pages, 3 figures + 8 pages supplemen

Operational Planning and Power Management System for Offshore Platform With Wind Energy Supply – Impacts on CO2 Reduction and Power Quality

publishedVersio

Accurate Dielectric Response of Solids: Combining the Bethe-Salpeter Equation with the Random Phase Approximation

The Bethe-Salpeter equation (BSE) can provide an accurate description of low-energy optical spectra of insulating crystals - even when excitonic effects are important. However, due to high computational costs it is only possible to include a few bands in the BSE Hamiltonian. As a consequence, the dielectric screening given by the real part of the dielectric function can be significantly underestimated by the BSE. Here we show that universally accurate optical response functions can be obtained by combining a four-point BSE-like equation for the irreducible polarisability with a two-point Dyson equation which includes the higher-lying transitions within the random phase approximation (RPA). The new method is referred to as BSE+. It has a computational cost comparable to the BSE but a much faster convergence with respect to the size of the electron-hole basis. We use the method to calculate refractive indices and electron energy loss spectra for a test set of semiconductors and insulators. In all cases the BSE+ yields excellent agreement with experimental data across a wide frequency range and outperforms both BSE and RPA.Comment: 6 pages, 4 figure