Academic literature on the topic 'Linjen for teknisk fysikk'

The Maximum Entropy Theory of Ecology (METE), developed by John Harte, presents an entirely new method of making inferences in ecology. The method is based on the established mathematical procedure of Maximum Information Entropy (MaxEnt), developed by Edwin T. Jaynes, and is used to derive a range of important relationships in macroecology. The Maximum Entropy Production (MEP) principle is a more recent theory. This principle was used by Paltridge to successfully predict the climate on Earth in 1975. It has been suggested that this principle can be used for predicting the evolution of ecosystems over time in the framework of METE. This idea is at the very frontier of Harte's theory. This thesis investigates the hypothesis that the information entropy defined in METE is described by the MEP principle.I show that the application of the MEP principle to the information entropy in METE leads to a range of conceptual and mathematical difficulties. I show that the initial hypothesis alone cannot predict the time rate of change, but that it does predict that the number of individual organisms and the total metabolic rate of an ecosystem will continue to grow indefinitely, whereas the number of species will approach one.I also conduct a thorough review of the MEP literature and discuss the possibility of an application of the MEP principle to METE based on analogies. I also study a proof of the MEP principle published by Dewar in 2003 and 2005 in order to investigate the possibility of an application based on first principles. I conclude that the MEP principle has a low probability of success if applied directly to the information entropy in METE.One of the most central relationships derived in METE is the expected number of species in a plot of area $A$. I conduct a numerical simulation in order to study the variance of the actual number of species in a collection of plots. I then suggest two methods to be used for comparison between predictions and observations in METE.I also conduct a numerical study of selectied stability properties of Paltridge's climate model and conclude that none of these can explain the observed MEP state in nature.

This report concerns preliminary studies of fingering and fracturing in gelling materials, with the aim of identifying how the phenomena of fingering transitions into fracturing as the breaking medium gradually becomes more solid-like.

The subject of this thesis is the study of the creation of fault lines in a random lattice, provoked by the successive failure of optimal paths. Using the recently developed Optimal Path Cracked model, we investigate how central characteristics of the successive optimal paths evolve as the lattice breaks down, and how this progression of characteristics depends on the magnitude of disorder imparted on the lattice. We then see how the OPC model, while originally proposed in the context of the shortest path problem, can be generalized to alternate optimal path problems, namely the minimax problem and the widest path problem. It is shown that for a given lattice, the minimax OPC is equal to the the backbone of the shortest OPC. The widest path OPC, although constituting a distinct object on any lattice, is shown to scale with lattice size in the same manner as the minimax OPC and the backbone of the shortest path OPC; with the fundamental process behind it being closely related to the minimax OPC process. Lastly, we explain the connection between the OPC process and a variety of other phenomena which have previously been shown to exhibit similar scaling behavior. We show how the OPC process for the widest path problem can be reduced to the shortest path problem on the dual lattice using the limit of very high disorder, the so-called ultrametric limit, and how an algorithm based on invasion percolation can be used as a quicker method of finding an OPC.

In this master thesis, thin lms of ZnO doped with various cobalt concentra-tions have been grown using Pulsed Laser Deposition (PLD). This growthtechnique is preferred because it is able to grow thin lms from a targetmaterial without changing the elemental ratios from the target. The targetsusing during deposition are sintered pellets of ZnO doped with cobalt, withdoping concentrations of 10, 20 and 30 %.The material was chosen because of its potential for Intermediate BandSolar Cells (IBSC). IBSC is a new concept which aims to create solar cellswhich have higher eciencies than the solar cells available today. From de-tailed balance theory, the concept of intermediate band solar cells shows apotential of a 86 % eciency limit under perfect conditions, which is remark-able compared to the conventional silicon solar cell devices on the markettoday with a eciency limit of 41 %.A series of ZnO thin lms of 10, 20 and 30 % cobalt concentration weredeposited by PLD on a sapphire substrate. These lms were, together with asimilar series containing 1,2 and 5 % cobalt concentration deposited on bothsilicon and sapphire substrates, characterized using Scanning Electron Mi-croscopy (SEM), Energy Dispersive X-ray (EDX) Microanalysis, X-ray Pho-toelectron Spectroscopy (XPS), Hall measurements, X-ray diraction (XRD)and optical transmission spectroscopy.In addition, an attempt to make Schottky diodes of the cobalt dopedZnO thin lms and a p-IB-n junction using GaN:Mg and ZnO:Al as the p-and n- emitter was done. These intermediate band solar cell devices weregoing to be studied by recording dark and illuminated current-voltage (I-V)characteristics.The focus in the study has been to determine which cobalt doping con-centration gives the desired properties for use of ZnO:Co in an intermediateband solar cell device, and to study how a solar cell device with an inter-mediate band material can be realized. The experiments were carried outat NTNU NanoLab, NTNU Department of Physics, NTNU Department ofElectronics and Telecommunications and SINTEF Oslo.Optical transmission spectroscopy and XPS showed that the cobalt inthe ZnO:Co lms were Co2+. This indicates that cobalt is substituting forzink in the ZnO lattice. XRD showed the crystal structure to be c-orientedwith reasonable order. The carrier concentration in the ZnO:Co lms were inthe order of 1018- 1019, decreasing with increasing cobalt concentration. Theresistivity in the samples increased with increasing doping concentration.Investigation of the GaN:Mg wafer showed that it did not have the desiredproperties for device fabrication as it showed n-type conductivity insteadof p-type. The Schottky diodes made of Au-ZnO:Co and Pt-ZnO:Co did not show diode behavior because of surface states in ZnO:Co making ohmiccontacts.

This master's thesis concerns the electrical activity and lifetime in compensated multicrystalline silicon wafers used for solar cell production.Resistivity profiles across grain boundaries have been obtained by a Four Point Probe (FPP). Profiles have been investigated in relation to minority carrier lifetime acquired by Microwave Photo Conductance Decay (uW-PCD).It has been found that a two-step process consisting of pre-annealing at either 600C or at 900C followed by phosphorus diffusion (P) gettering will increase the electrical activity of crystalline defects. It has been proposed that a P gettering step should follow directly after annealing for a better dissolution of metallic precipitates. Introduced defects in the material as a consequence of both pre-annealing at 900$^circ$C and of resistivity measurements before gettering, have possibly enhanced the phosphorus diffusion depth in the gettering process. The higher concentration of phosphorus has lead to an augmented lifetime in the material. Metallic impurity precipitation at defects, affecting the electrical activity and the minority carrier recombination rate, has been observed. A good correlation between grain structure, resistivity- and lifetime profiles has thus been established.

This thesis describes a new instrumental approach designed to measure the complex Young’s modulus on cylindrical samples 1 inch in diameter 2 inch long and typically in the range of 1-70 GPa. Excitation frequencies are from 11 Hz to 167 Hz. The setup is based on the Forced Deformation Method (Batzle et al., 2006) and is capable of measuring phase and magnitude of the dynamic stress and strain. An actuator provides an oscillating force from one end of the plug. Strain is measured on the cylindrical side with three strain gages evenly spaced around the circumference. The lowest recordable magnitude of strain is in the order of 10E-8. Force is measured by a piezoelectric transducer. Values are < 10 N. Plug sample measurements of the Young’s modulus values for Berea sandstone, Castlegate sandstone, Pierre shale, PEEK, and aluminium alloys (ALU-7075 and ALU-6061) are included. Reference material results are in accordance with published values. Some of the instrumentation needed is also given in detail in the previous work (Fintland, 2010).

The effect of clustering during natural aging of three different Al-Mg-Sialloys with equal Mg/Si-ratios, but different Mg+Si contents have beenstudied through hardness measurements and transmission electron mi-croscopy (TEM). Hardness measurements were performed both duringnatural aging (NA) and after various NA times followed by subsequentartificial aging for all alloys, while TEM-investigations were performedon selected samples. The results from the experiments were comparedand the existence of three different clustering processes were discovered.The first process was established to be Si-Si clustering causing a slighthardness increase during natural aging and a strong hardness increaseafter subsequent artificial aging. The second process was found to beMg-Mg clustering causing a significant hardness increase during naturalaging, and a clear decrease in hardness after subsequent artificial aging.The third process was found to be Mg-Si clustering and simultaneoustransformation of mono-clusters into co-clusters. This combined processcauses a hardness increase both during natural aging and after subse-quent artificial aging. The hardness increase is caused by a refinementof alloy microstructure including a higher number of smaller ” needles.This precipitate type was observed for all alloys and conditions. Thenegative effect of Mg-Mg clusters on precipitation hardness is suggestedto be related to the repulsion of Si from these clusters. This hinders theco-clustering of Mg and Si in the areas surrounding these clusters.

Ozone and temperature data from Troll and Rothera research stations has been analyzed in order to trace planetary waves. Seasonal variations were removed and spectral analysis was performed in order to find dominating frequencies. Possible planetary wave oscillations were found in the 4, 5, 8.5, 10-11, 11-13, 14-15, 17-20, 21-24 and 26-45 day bands, some corresponding to the atmospheric normal modes. These were found consistently in both the ozone and temperature data, indicating that the millimeter wave spectroscopy used to measure the ozone is a viable technique for tracing planetary waves in a region of the atmosphere where other measurements are sparse.

Computational fluid dynamics (CFD) was be used to investigate aspects of interaction of flow over two airfoils in relatie motion in detail.%Problem statement2D tandem airfoil setups were studied, where the leading airfoil was performing an oscillating motion in the vertical direction while the trailing airfoil was kept stationary. The NACA 0012 and the S809 airfoils were considered.%ApproachAnsys Fluent v13.0 was used as the CFD solver, and Gambit v2.4.6 was employed for grid generation. All simulations were transient at a Reynolds number of either 2*10^4 (laminar flow) or 3*10^6 (turbulent flow). The Transition SST turbulence model was chosen to model turbulence, and Fluent's sliding grid technique was used to achieve the relative motion between the airfoils.%ResultsThe tandem setup was found able to outperform a single airfoil for similar conditions. The presence of a trailing airfoil did not significantly affect the leading airfoil's performance, whereas it did affect the wake structures significanlty. The suction peak near the nose of the airfoil was found to be the most important factor determining the airfoil's propulsive efficiency. Therefore, leading edge vortex (LEV) shedding was found to be of higher importance than trailing edge vortex (TEV) shedding when airfoil performance was concidered.The asymmetric S809 airfoil provided similar results as the symmetric NACA 0012 airfoil. However, the NACA 0012 airfoil achieved slightly higher propulsive efficiencies for the cases investigated, indicating that a symmetric airfoil is desired for flapping airfoil setups. For the tandem setup the highest propulsive efficienies were 0.766 and 0.742 for the NACA 0012 airfoil and the S809 airfoil, respectively. Both peaks were found at k = 0.3 and h = 0.6 (Sr = 0.11) for the leading airfoil. A maximum thrust coefficient of 2.32 was found for the tandem S809 airfoil setup at k = 1.5 and h = 0.5 (Sr = 0.48).The Strouhal number was found to be an important describing parameter, but additional information about the reduced frequency or the oscillating amplitude was needed in order to fully describe the setup.

In this thesis the strain properties of two InAs/GaAs quantum dot intermediate band solar cell materials have been explored. Both samples were thin films grown on a (100) GaAs substrate. The quantum dot material was InAs, and the bulk material was GaAs. One sample had AlAs-cap, while the other had GaAs-cap. Geometrical phase analysis was used to study the strain. A higher degree of strain was found in the AlAs-capped sample. Negative strain was observed in directly above and below the quantum dots in both samples. A stacking fault in a quantum dot in the AlAs-capped sample was found to relax all the strain. Analysis of the chemical composition of the AlAs-capped sample was performed using HAADF-STEM and multislice analysis. This analysis found an average indium concentration inside the quantum dots of 25% +- 10%, with peaks up to 50%.

Kustekosystemen är mycket viktiga för både biologisk mångfald och ekosystemtjänster, men påverkas samtidigt negativt av ett kontinuerligt ökat nyttjande av kustzonen för boende och olika verksamheter. Ekologisk kompensation är ett förvaltningsverktyg som syftar till att gottgöra oundviklig skada på naturmiljöer, exempelvis arter, naturtyper, ekosystemfunktioner och upplevelsevärden, i samband med mänsklig verksamhet. Verktyget har dock hittills använts i mycket begränsad omfattning i grunda kustmiljöer. Inom projektet ECOCOA, finansierat av Naturvårdsverket, har vi fokuserat på att utvärdera förutsättningarna för ökad användning av ekologisk kompensation i kustområden, som ett av flera verktyg som kan stöda miljövården. Projektets slutrapport (Bergström m.fl. 2021) ger en övergripande bild av samtliga resultat, medan vi i föreliggande rapport ger en fördjupning av de mer konkreta problem som kan uppstå vid handläggning av miljöärenden i förvaltningen, och möjliga lösningar på kort och lång sikt. Rapporten riktar sig i första hand till handläggare som vill utveckla tillämpningen av ekologisk kompensation vid vattenverksamhetsärenden, till tekniska råd vid markoch miljödomstolar, samt miljökonsulter och andra som kan behöva insyn i hur ekologisk kompensation kan användas och vidareutvecklas inom svensk kustmiljöförvaltning. I rapporten återger vi hur man hanterar ekologisk kompensation i svenska kustområden idag, till exempel hur handläggare arbetar med att mäta skada och bedöma omfattningen av kompensationsbehov. Vi beskriver även problematiken med småskaliga anmälningspliktiga ärenden, där den sammanlagda påverkan från många små exploateringar ger upphov till betydande förluster av biologisk mångfald och ekosystemtjänster. Slutligen beskriver vi hur den så kallade särskilda fiskeavgiften, som syftar till att tillvarata fiskeintresset i samband med vattenverksamhetsfrågor, tillämpas idag, samt analyserar hur beräkningsgrunderna skulle kunna utvecklas för att stärka användningen av ekologisk kompensationen som verktyg. Vår sammanställning och utvärdering utgår från ett generellt ramverk som utvecklats inom ECOCOA för att skatta skada och identifiera kompensationsbehov. Ramverket baseras på en kaskadmodell, som visar kopplingar mellan ekosystemets struktur, funktion, ekosystemtjänster och nyttigheter för människor. Modellen kan användas för att synliggöra hur verksamheter påverkar arter och livsmiljöer och vilka kostnader och förluster detta medför. Ramverket kan även användas för att bedöma i vilken omfattning en föreslagen åtgärd faktiskt kompenserar för de förluster som verksamheten innebär. Här följer en kort sammanfattning av resultaten som presenteras i rapporten: • En enkätundersökning riktad till aktörer inom kustförvaltningen visar att ekologisk kompensation i praktiken tillämpas mycket sällan inom kustmiljöförvaltningen idag, och att det finns ett stort behov av att ta fram riktlinjer för dess tillämpning, som stöd till handläggare, konsulter, domstolar och andra aktörer. På en mer generell nivå omfattar detta även ett behov av att förbättra kunskapen om restaureringsmetoder samt att ta fram metoder för värdering av skador på naturvärden. Det finns även ett behov av resurser för Sammanfattning 6 handläggare i form av tid och stöd för att tillämpa ekologisk kompensation i kustförvaltningen. • En utvärdering av befintliga domslut för ett antal tillståndspliktiga (dvs. storskaliga) vattenverksamhetsärenden visar att biologisk mångfald och ekosystemtjänster mycket sällan beaktas på ett sätt som är i linje med Sveriges åtaganden inom till exempel konventionen för biologisk mångfald och EU:s biodiversitetstrategi, där en bärande princip är att ingen nettoförlust ska ske. Det finns ett förbättringsutrymme som borde kunna mötas direkt genom en ökad kunskapsdelning mellan aktörer, och en förbättrad praxis gällande tillämpning av ekologisk kompensation. Samtidigt uppstår flera mer komplexa frågor som berör till exempel behovet av en gemensam fysisk planering och identifiering av lämpliga kompensationsåtgärder, där ett kunskapsbyggande behövs. • Småskalig kustexploatering, exempelvis bryggbyggen och små muddringar, är en särskilt utmanande fråga. Enskilda små ingrepp är anmälningspliktiga (dvs. sällan tillståndspliktiga), och trots att det vid handläggningen av dessa ärenden ställs krav på miljöhänsyn kan det ofta inte bedömas som skäligt att kräva att exploatören själv utför ekologisk kompensation. Den sammanlagda påverkan av dessa många små ingrepp är dock betydande, och det är angeläget att utforma ett system där även småskalig vattenverksamhet kompenserar för sina miljökostnader. Vi undersöker hur ett system för ekologisk kompensation som även omfattar småskalig exploatering skulle kunna se ut, i relation till konceptet habitatbanker eller kompensationspooler, där exploatören kan bidra ekonomiskt till habitatrestaureringar i stället för att själv utföra dem. • Den särskilda fiskeavgiften syftar till att kompensera för skador från vattenverksamheter på fisket och skulle kunna betraktas som ett förvaltningsverktyg för kompensation av en viss typ av förlust. I rapporten utvärderar vi hur det rådande fiskeavgiftssystemet fungerar och utforskar hur det kan fungera ur ett kompensationsperspektiv, samt ger förslag på hur beräkningsmodellen kan utvecklas. Sammantaget finns det ett stort behov av att utveckla ekologisk kompensation som ett av de verktyg som kan bidra till att motverka den allt snabbare förlusten av biologisk mångfald och ekosystemfunktioner. Parallellt behövs ytterligare åtgärder för att stärka skyddet av de känsligaste livsmiljöerna i kustzonen, eftersom bevarande av fungerande livsmiljöer är att föredra som ett mer kostnadseffektivt verktyg än restaurering av störda miljöer.