6-meter wavelength polarimetric inverse synthetic aperture radar mapping of the Moon

Remote sensing of planetary surfaces is an effective method for gaining knowledge of the processes that shape the planetary bodies in our solar system. This is useful for uncovering the environment of the primordial solar system and to study the current state of the upper crusts of the other planets in our neighborhood. A recent 6-meter wavelength polarimetric radar map of the Moon showed unexpectedly low depolarized radar returns in two regions on the lunar nearside. These two areas were a highland region between Mare Imbrium and Mare Frigoris, and the highland area surrounding the Schiller-Zucchius impact basin. These two regions showed characteristics unlike those of typical highland regions of the lunar surface. So far, there has been no readily available explanation for this observation. In this study, it is shown that the likely cause is an increased loss tangent due to chemical differences in the first few hundred meters of the lunar soil. We also show the absence of any coherent subsurface, which could be the preserved remains of an ancient basaltic plain. We do this by comparing the 6-meter polarimetric radar map to other relevant data sets: 1) surface TiO_2 and FeO abundance, 2) surface rock population, 3) radar maps of the Moon with other wavelengths, and 4) visual spectrum images of the Moon. The area near the Schiller-Zucchius basin was shown to be consistent with other areas with similar surface chemical compositions, but the region between Mare Imbrium and Mare Frigoris showed significantly lower mean power in comparison to otherwise similar regions. While we can not conclusively determine the cause, we hypothesize that the low radar return is explained by an increased concentration of iron and titanium oxides in the volume beneath the surface, potentially due to remnants of primordial lunar volcanism. The results show that long wavelength polarimetric radar measurements of the Moon are very powerful tools for studying the earliest stages of the evolution of the Moon

Price Coordination and Consumer Behavior : Evidence from Retail Fuel

This thesis consists of an introduction and three essays on price coordination and consumer behavior in the retail fuel market. Each essay includes one of the research articles that compose the principle part of the thesis. The essays use microeconometric methods and data from the Norwegian retail fuel market to investigate how firms use price leadership to coordinate more frequent price increases, the costs and benefits of price leadership, and long-run dynamics in consumers’ response to changes in the intertemporal price pattern. The introduction summarizes the essays, discusses the merits of studying firm and consumer behavior in the retail fuel market, and elaborates on policy implications of the research in the thesis. Price leadership—a practice involving sequential price changes whereby a leader changes price first and rivals quickly follow—is commonly observed in many retail markets. The first chapter use a unique dataset spanning 14 years with the exact timing of price changes for most Norwegian gasoline stations to study price leadership and coordination in the Norwegian retail gasoline market. The market features asymmetric price cycles where prices slowly fall for several days before being restored to a high level within a few hours. The main contribution is to show how large retail chains use price leadership to both agree on and sustain a new equilibrium with more frequent price hikes. I argue that faster price changes due to a lack of price regulations in Norway can explain why the chains in Norway end up coordinating on a different equilibrium than in other countries. By combining the price data with data on volumes and costs, I estimate that the transition to more frequent price hikes has a substantial positive effect on volume-weighted retail margins. Price leadership can bring about higher prices for all firms in the market, but can also be costly for the leader because it loses volume to rivals in the interim period when it is the sole firm with a high price. The second chapter of my thesis studies the costs and benefits of price leadership in the Norwegian retail gasoline market. The dataset with high-frequency price and volume data coupled with a particular pricing pattern allows the estimation of the costs and benefits of leading price hikes. The main result is that the leader’s volume loss from being the sole firm to raise its price until the other firms match that price increase is small compared with the large margin increases and profit gains resulting from the price jumps. Furthermore, I find that the leader is not worse off than the non-leading firms. The results can assist in explaining why firms are willing to act as regular price leaders. Many retail markets feature intertemporal price variation caused by promotional sales, short-run wholesale price variation, or price cycles where prices fall for several days before quickly being restored to a high level. The third chapter uses 11 years of high-frequency prices and volumes for Norwegian gas stations to study the short- and long-run consumer response to price cycles with a regular low-price period at the same time every week (the sale period). I show that diesel and gasoline consumers over time increasingly fill their tanks during the sale period. Before the transition to the new price pattern, about 21% of the weekly gasoline and diesel volumes are sold in that part of the week. In the first quarter after the transition, the sale-period volume shares increase by 1–2 percentage points. In the subsequent years, the sale-period rebates remain stable while the sale-period volume shares keep rising, to total increases of 6–9 percentage points five years later. The intertemporal price elasticity increases from about -2 immediately after the transition to -6 five years later. These findings emphasize the importance of accounting for dynamics when studying consumer responses to intertemporal price variation and suggest that non-volume-weighted prices may be a poor proxy for the prices consumers pay.Doktorgradsavhandlin

RILU preconditioning; a computational study

AbstractWe present a computational study of the RILU preconditioning strategy applied to finite-difference discretizations of self-adjoint elliptic boundary value problems with highly discontinuous coefficients. The behaviour of the eigenvalues of the preconditioned system, the numerical stability of the factorization process and the efficiency of the preconditioning strategy are discussed

Applications of the DFLU flux to systems of conservation laws

The DFLU numerical flux was introduced in order to solve hyperbolic scalar conservation laws with a flux function discontinuous in space. We show how this flux can be used to solve systems of conservation laws. The obtained numerical flux is very close to a Godunov flux. As an example we consider a system modeling polymer flooding in oil reservoir engineering

Konglomeratrabatten - myte eller realitet? : forklaring av verdieffekter ved urelatert diversifisering gjennom bruk og sammenfatning av tidligere studier

Formålet med denne oppgaven er å forklare verdieffektene av urelatert diversifisering gjennom bruk og sammenfatning av tidligere studier. I første del beskriver og systematiserer vi selskapsfaktorer, som spesielt innvirker på verdien av et konglomerat, i ulike perspektiver. Andre del fokuserer på vanlige målemetoder for å estimere en eventuell konglomeratrabatt, og hva empirisk forskning sier om rabatten. Tverrsnittanalyser viser en signifikant konglomeratrabatt i størrelsesorden 3-19 %. Videre kritiseres svakheter ved målemetodene, som at benyttede data ofte er for unøyaktige og at fundamentale selskapsforhold ikke tas hensyn til. Rabatten er reell i mange tilfeller, men skyldes ofte andre forhold enn diversifiseringen i seg selv. I siste del av utredningen sammenfatter og analyserer vi tidligere gjennomgått teori. Den største, og mest sannsynlige, verdidriveren og verdiforringeren i et konglomerat identifiseres til henholdsvis ressursbasert diversifisering og agentproblemer. Vi finner også at selskapers optimale diversifiseringsnivå varierer stort, og bestemmes av karakteristikker ved selskapet og dets omgivelser

Penalty methods for the numerical solution of American multi-asset option problems

AbstractWe derive and analyze a penalty method for solving American multi-asset option problems. A small, non-linear penalty term is added to the Black–Scholes equation. This approach gives a fixed solution domain, removing the free and moving boundary imposed by the early exercise feature of the contract. Explicit, implicit and semi-implicit finite difference schemes are derived, and in the case of independent assets, we prove that the approximate option prices satisfy some basic properties of the American option problem. Several numerical experiments are carried out in order to investigate the performance of the schemes. We give examples indicating that our results are sharp. Finally, the experiments indicate that in the case of correlated underlying assets, the same properties are valid as in the independent case

Investigation of exceptionally radar-dark regions on the lunar nearside

Presentation at the 19th International EISCAT Symposium 2019 and 46th Annual European Meeting on Atmospheric Studies by Optical Methods, Oulu, Finland, 19.08. - 23.08.19, arranged by the University of Oulu. (http://www.sgo.fi/Events/EISCAT46AM/). Remote sensing of planetary surfaces is an effective method for gaining knowledge of the processes that shape the planetary bodies in our solar system. This is useful for uncovering the environment of the primordial solar system and to study the current state of the upper crusts of the other planets in our neighborhood. A recent 6-meter wavelength polarimetric radar map of the Moon [?] showed unexpectedly low depolarized radar returns in two regions on the lunar nearside. These two areas were a highland region between Mare Imbrium and Mare Frigoris, and the highland area surrounding the Schiller-Zucchius impact basin. These two regions showed characteristics unlike those of typical highland regions of the lunar surface. So far, there has been no readily available explanation for this observation. In this study, it is shown that the likely cause is an increased loss tangent due to chemical differences in the first few hundred meters of the lunar soil. We also show the absence of any coherent subsurface, which could be the preserved remains of an ancient basaltic plain. We do this by comparing the 6-meter polarimetric radar map to other relevant data sets: 1) surface TiO2 and FeO abundance, 2) surface rock population, 3) radar maps of the Moon with other wavelengths, and 4) visual spectrum images of the Moon. The area near the Schiller-Zucchius basin was shown to be consistent with other areas with similar surface chemical compositions, but the region between Mare Imbrium and Mare Frigoris showed significantly lower mean power in comparison to otherwise similar regions. While we can not conclusively determine the cause, we hypothesize that the low radar return is explained by an increased concentration of iron and titanium oxides in the volume beneath the surface, potentially due to remnants of primordial lunar volcanism. The results show that long wavelength polarimetric radar measurements of the Moon are very powerful tools for studying the earliest stages of the evolution of the Moon. The new EISCAT 3D installation will enable new measurements in a wavelength which has not been used before. The facility can also track the Moon to obtain a long observation time, increasing resolution. The multiple receiving locations will provide excellent interferometric baselines to, among other things, resolve the range-Doppler ambiguity. Polarimetric measurements are useful for separating surface and volume scattering, as well as potential target-based decomposition modelling

Workshop om PICO. Godbit fra EAHIL-konferansen, Lisboa, 14.-18. juni 2010.

I forkant av årets EAHIL-konferanse var det satt opp to dager med ”continuing education courses”. Jeg hadde stort utbytte av å være en av syv deltakere på en workshop om PICO. Kursholderne Marion Heijmand, leder for det medisinske biblioteket ved Orbis Medical Centre, Eindhoven, og Hans Ket, ”medisinsk informasjonsspesialist” ved det medisinske bibliotek i Vrije Universiteit (the VU University), Amsterdam, holdt et svært inspirerende og intensivt kurs