Modeling long-term electricity forward prices

In contrast to forwards and futures on storable commodities, prices of long-term electricity forwards exhibit a dynamics different to that of short-term and mid-term prices. We model long-term electricity forward prices through demand and supply for electricity, adjusted with a risk premium. Long-term prices of electricity, oil, coal, natural gas, emission allowance, imported electricity and aluminum are modeled with a vector autoregressive model. To estimate the model we use weekly prices of far-maturity forwards relevant for Nordic electricity market. Electricity prices experienced few substantial shocks during the period analyzed, however, we found no evidence of a structural break. Cointegration analysis indicates two stationary cointegrating vectors. Nord Pool price is found significant in the short- and the long-run model, while the gas price is insignificant in both. Other variables are significant only in the long-run model. The model shows some influence of the risk premium, however not on the long-term electricity forwards at Nord Pool.Electricity prices; long-term forward prices; VAR modeling; cointegration

From directions to actions – IT support for individual mobility in everyday activities

Being mobile is a crucial factor for taking part in society and living an autonomous live. Nevertheless, the demographic change, more sparse infrastructures and an tendency to move to more urban areas challenges people’s ability to maintain their personal everyday mobility options. One group in society that is especially affected by these challenges are the elderly. While we do not claim that the elderly in general present a homogenous group, but instead represent a very heterogenous group with very different social backgrounds and individual experiences, they do have experienced various changes in their lives, such as retiring and changes in their financial situations as well as physical condition. These experiences made them reflect their current situations as well as anticipate future changes. Thus, working with older adults in order to understand how they decide on adapting to changes in their mobility is very promising. This work, therefor, focusses on how the adoption of transportation opportunities for individual everyday mobility can be supported by using information and communication technologies (ICT). Based on empirical studies with older adults that were carried out in three consecutive Design Case Studies (DCS) in a larger living lab context, we present practice-based insights on how different means of transportation are seen from a user’s perspective. The first DCS represents an empirical framing of this thesis. The findings of that DCS show that the supporting the appropriation of different modes is highly individual, needs contextual adaptations and needs to take into account, that different modes of transportation do not fit all situations encountered by people. Considering this, the second DCS shows exemplary how ridesharing concepts could be altered to make them more suitable for everyday contexts. Specifically, the flexibility that our participants value during their everyday mobility needs to be preserved when engaging in ridesharing. The third DCS presents derives the technological implications from the preceding DCSs and validate the technological feasibility of the proposed ICT-based concept for everyday ridesharing support. The findings highlight that a suitable support for everyday mobility should take into account far more than logistical factors, which play in important role but are highly influenced by routines and therefor presents only little opportunities to be changed. Instead, contextual information that can be derived from the activities that induce the transportation as well as personal meaningful historical information, such as informal naming, known landmarks or typical routes and routines provide opportunities to highlight the suitability of alternatives modes of transportation. In addition, this work also presents a critical reflection of the methods used, especially looking at the role of users in defining the problem and the design space of ICT-based solutions.Mobilität ist ein entscheidender Faktor für die Teilhabe an der Gesellschaft und ein selbstbestimmtes Leben. Dennoch stellen der demografische Wandel, spärlichere Infrastrukturen und die Tendenz, sich in mehr städtische Gebiete zu verlagern, die Fähigkeit der Menschen, ihre persönlichen Mobilitätsoptionen im Alltag aufrechtzuerhalten, in Frage. Eine Gruppe in der Gesellschaft, die von diesen Herausforderungen besonders betroffen ist, sind ältere Menschen. Auch wenn ältere Menschen im Allgemeinen keine homogene Gruppe darstellen, sondern eine sehr heterogene Gruppe mit sehr unterschiedlichen sozialen Hintergründen und individuellen Erfahrungen repräsentieren, haben sie doch verschiedene Veränderungen in ihrem Leben erfahren, wie beispielsweise die Pensionierung und Veränderungen in ihrer finanziellen Situation oder ihrer körperlichen Verfassung. Diese Erfahrungen haben sie dazu veranlasst, ihre gegenwärtige Situation zu reflektieren und zukünftige Veränderungen zu antizipieren. Daher ist die Arbeit mit älteren Erwachsenen vielversprechend, um zu verstehen, wie sie sich an Veränderungen in ihrer Mobilität anpassen. Im Mittelpunkt dieser Arbeit steht daher die Frage, wie durch den Einsatz von Informations- und Kommunikationstechnologien (IKT) die Nutzung von Transportmöglichkeiten für die individuelle Alltagsmobilität unterstützt werden kann. Basierend auf empirischen Studien mit älteren Erwachsenen, die in drei aufeinander folgenden Design Case Studies (DCS) in einem größeren Living-Lab-Kontext durchgeführt wurden, präsentieren wir praxisbezogene Erkenntnisse darüber, wie unterschiedliche Verkehrsmittel aus der Perspektive des Nutzers gesehen werden. Die erste DCS stellt einen empirischen Rahmen dieser Arbeit dar. Die Ergebnisse dieses DCS zeigen, dass die Unterstützung der Aneignung verschiedener Verkehrsträger sehr individuell ist, kontextuelle Anpassungen erfordert und berücksichtigt werden muss, dass verschiedene Verkehrsmittel nicht für alle Situationen geeignet sind. Vor diesem Hintergrund zeigt die zweite DCS exemplarisch, wie Mitfahrkonzepte verändert werden können, um sie alltagstauglicher zu machen. Konkret gilt es, die persönliche Flexibilität während der täglichen Mobilität auch bei Mitfahrgelegenheiten zu erhalten. Die dritte DCS leitet die technologischen Implikationen aus den vorangegangenen DCS ab und validiert die technologische Machbarkeit des vorgeschlagenen IKT-basierten Konzepts für die Unterstützung alltäglicher Fahrgemeinschaften und Mitfahrgelegenheiten. Die Ergebnisse zeigen, dass bei einer geeigneten Unterstützung der alltäglichen Mobilität weit mehr berücksichtigt werden sollte als logistische Faktoren, die zwar eine wichtige Rolle spielen, aber stark von Routinen beeinflusst werden und daher nur geringe Veränderungsmöglichkeiten bieten. Stattdessen bieten Kontextinformationen, die sich aus den transportinduzierenden Aktivitäten ableiten lassen, sowie persönlich relevante Verhaltensinformationen, wie informelle Benennungen öffentlicher Orte oder typische individuelle Routen und Routinen, Möglichkeiten die Eignung alternativer Verkehrsoptionen aufzuzeigen. Darüber hinaus ist diese Arbeit auch eine kritische Reflexion der verwendeten Methoden, vor allem im Hinblick auf die Rolle der Nutzer bei der Definition des Problems und der Design-Raum von IKT-basierten Lösungen

Confirming what we know: Understanding questionable research practices in intro physics labs

Many institutions are changing the focus of their introductory physics labs from verifying physics content towards teaching students about the skills and nature of science. As instruction shifts, so too will the ways students approach and behave in the labs. In this study, we evaluated students' lab notes from an early activity in an experimentation-focused lab course. We found that about 30% of student groups (out of 107 groups at three institutions) recorded questionable research practices in their lab notes, such as subjective interpretations of results or manipulating equipment and data. The large majority of these practices were associated with confirmatory goals, which we suspect stem from students' prior exposure to verification labs. We propose ways for experimentation-focused labs to better engage students in the responsible conduct of research and authentic scientific practice.Comment: 4 pages, 4 figure

A Grid of 3D Stellar Atmosphere Models of Solar Metallicity: I. General Properties, Granulation and Atmospheric Expansion

Present grids of stellar atmosphere models are the workhorses in interpreting stellar observations, and determining their fundamental parameters. These models rely on greatly simplified models of convection, however, lending less predictive power to such models of late type stars. We present a grid of improved and more reliable stellar atmosphere models of late type stars, based on deep, 3D, convective, stellar atmosphere simulations. This grid is to be used in general for interpreting observations, and improve stellar and asteroseismic modeling. We solve the Navier Stokes equations in 3D and concurrent with the radiative transfer equation, for a range of atmospheric parameters, covering most of stellar evolution with convection at the surface. We emphasize use of the best available atomic physics for quantitative predictions and comparisons with observations. We present granulation size, convective expansion of the acoustic cavity, asymptotic adiabat, as function of atmospheric parameters. These and other results are also available in electronic form.Comment: 16 pages, 12 figures. Accepted for publication in ApJ, 201

Improvements to stellar structure models, based on a grid of 3D convection simulations. II. Calibrating the mixing-length formulation

We perform a calibration of the mixing length of convection in stellar structure models against realistic 3D radiation-coupled hydrodynamics (RHD) simulations of convection in stellar surface layers, determining the adiabat deep in convective stellar envelopes. The mixing-length parameter $\alpha$ is calibrated by matching averages of the 3D simulations to 1D stellar envelope models, ensuring identical atomic physics in the two cases. This is done for a previously published grid of solar-metallicity convection simulations, covering from 4200 K to 6900 K on the main sequence, and 4300-5000 K for giants with logg=2.2. Our calibration results in an $\alpha$ varying from 1.6 for the warmest dwarf, which is just cool enough to admit a convective envelope, and up to 2.05 for the coolest dwarfs in our grid. In between these is a triangular plateau of $\alpha$ ~ 1.76. The Sun is located on this plateau and has seen little change during its evolution so far. When stars ascend the giant branch, they largely do so along tracks of constant $\alpha$, with $\alpha$ decreasing with increasing mass.Comment: 22 pages, 15 figures, accepted for publication in MNRA