| 1. |
- Ahlgren, Niklas, et al.
(författare)
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PRISMA Mission Extension : Adapting Mission Operations to New and Changing Mission Objectives
- 2012
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Ingår i: SpaceOps 2012 Conference. - Reston, Virigina : American Institute of Aeronautics and Astronautics.
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Konferensbidrag (refereegranskat)abstract
- The PRISMA in-orbit test-bed was launched in June 2010 to demonstrate strategies and technologies for formation flying and rendezvous. OHB Sweden is the prime contractor for the project which is funded by the Swedish National Space Board (SNSB) with support from DLR, CNES, and DTU. In early September of 2011, 15 months after launch, all primary mission objectives of the PRISMA formation flying satellites had been achieved and mission success was declared. Since a significant amount of delta-V capability still remained an open call for new experiments was issued, inviting both old and new experimenters to use the capabilities of the formation. Several interested parties took the opportunity to perform their own experiments with an existing platform, each coming with new mission objectives not previously planned to be flown on the PRISMA satellites. Some of these experiments were close to what had already been achieved within the nominal mission, but some included new ways of using the formation not envisioned by the spacecraft designers. The new experiments span from data collection in specific relative orbits, with a separation from a few meters to several kilometers, to entirely new modules within the on-board software. Changing from a pre-planned technology demonstration mission to operating a commercial resource required adaptation of the original operational concept, taking into account the different levels of experience of the customers and managing the satellites between experiments. This paper describes how these new mission objectives were integrated in operations and how a sometimes very short turn-around between initial concept and experiment execution was implemented with the aid of well established validation processes, high degrees of on-board autonomy and a flexible operations team.
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| 2. |
- Andersson, Roy, et al.
(författare)
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Internationalisering av samverkan (INSA) : Slutrapport
- 2021
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Rapport (populärvet., debatt m.m.)abstract
- Internationaliseringen av den svenska akademin har kommit olika långt vid olika lärosäten och inom olika ämnesområden. Det är dock uppenbart att Sveriges lärosäten aktivt kommer att behöva ytterligare internationalisera sin verksamhet för att kunna påverka ännu mer lokalt, regionalt, nationellt och internationellt. Internationellt samarbete finns givetvis sedan länge inom utbildning och/eller forskning, men sällan sammanhållen med samverkan med näringsliv och offentlig verksamhet. Allt fler lärosäten funderar nu på hur man strategiskt ska koppla ihop internationalisering med lärosätets ambition för samverkan. Högskolornas nästa utmaning är att bygga kompletta internationella kunskapsmiljöer där samverkan kommer att behövas i lika stor grad som på den nationella arenan.
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| 3. |
- Liu, Xijia, 1983-
(författare)
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On Non Parametric Regression and Panel Unit Root Testing
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, two different issues in econometrics are studied, the estimation of regression coefficients and the non-stationartiy analysis in a panel setting.Regarding the first topic, we study a set of measure of location-based estimators (MLBEs) for the slope parameter in a linear regression model with a single stochastic regressor. The median-unbiased MLBEs are interesting as they can be robust to heavy-tailed and, hence, preferable to the ordinary least squares estimator (LSE) in such situations. Two cases, symmetric stable regression and contaminated normal regression, are considered as we investigate the statistical properties of the MLBEs. In addition, we illustrate how our results can be extended to include certain heteroscedastic regressions.There are three papers concerning the second part. In the first paper, we propose a novel way to test the unit roots in the panel setting. The new tests are based on the observation that the trajectory of the cross sectional sample variance behaves differently for stationary than for non-stationary processes. Three different test statistics are proposed. The limiting distributions are derived and the small sample properties are studied by simulations. In the remaining papers, we focus on the studies of the block bootstrap panel unit root tests proposed by Palm, Smeekes and Urbain (2011) which aims at dealing with a rather general cross-sectional dependency structure. One paper studies the robustness of PSU tests by a comparison with two representative tests from the second generation panel unit root tests. In another paper, we generalized the block bootstrap panel unit root tests in the sense of considering the deterministic terms in the model. Two different methods to deal with the deterministic terms are proposed and the asymptotic validity of bootstrap tests under the main null hypothesis is theoretically checked. The small sample properties are studied by simulations.
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| 4. |
- Pokrupa, Nils, et al.
(författare)
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One Year of In-Flight Results from the Prisma Formation Flying Demonstration Mission
- 2011
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Ingår i: 25th Annual AIAA/USU Conference on Small Satellites.
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Konferensbidrag (refereegranskat)abstract
- The Prisma smallsat in-orbit test-bed was launched on the 15th of June, 2010 to demonstrate strategies and technologies for formation flying and rendezvous. The mission consists of two spacecraft: Mango and Tango. Mango is 3-axis stabilized and is equipped with a propulsion system providing full 3D orbit control capability. Tango has a simplified solar magnetic control system and does not have any orbit control capability. The two spacecraft were launched clamped together into a 720/780 km altitude sun synchronous dawn-dusk orbit, and later separated in August of 2010. Since then, the two spacecraft, and rather lean operations team, have been performing a steady march through a tight mission and experiment timeline. This paper gives an overview of the Prisma mission in general and will focus on the lessons that have been learned from running a relatively intense, yet lean, small satellite technology demonstration mission. It has proven to show the value of autonomy and small platform applications, allowing for a high return on effort. Spacecraft autonomy and small, highly competent teams have allowed for quick and cost effective adaptations to changes and problem situations. The broad range of flight results from only one year in operation support these conclusions.
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| 5. |
- Vahlne, Niklas, 1978, et al.
(författare)
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Energy Efficiency at the Base of the Pyramid: A System-Based Market Model for Improved Cooking Stove Adoption
- 2014
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Ingår i: Sustainability. - : MDPI AG. - 2071-1050. ; 6:12, s. 8679-8699
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Tidskriftsartikel (refereegranskat)abstract
- A widespread dissemination of improved cooking stoves in the developing world can lead to considerable improvement of health, to reduced pressure on natural woody resources and to substantial reductions of emissions contributing to global warming. A number of programs have aimed to achieve such dissemination, while few of the programs have had any large-scale success. It has been suggested that a more commercial approach, as opposed to subsidized or freely distributed stoves, would achieve a higher level of success. However, a majority of the households that would benefit from an improved stove are poor and cannot afford the cost of the stove, especially if no monetary savings are possible from a more efficient fuel use, i.e., if the fuel used is collected biomass. The aim of this paper is to propose and evaluate a model that might overcome some of the barriers previous programs have experienced. The proposed model involves commercialization of collected fuels. The methods for evaluation include a qualitative assessment of the proposed model aided by the literature on improved cooking stove programs, fuel wood collection and fuel switching together with a quantitative simplistic model calculation of a hypothetical application of the proposed model principles, in order to assess its financial feasibility. The assessment indicates that the model would increase both households' incentives and means to purchase and use improved cooking stoves. Furthermore, the model could possibly be partly financed based on carbon credits achieved from the reduction of greenhouse gas emissions.
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| 6. |
- Vahlne, Niklas, 1978, et al.
(författare)
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Policy implications for improved cook stove programs-A case study of the importance of village fuel use variations
- 2014
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Ingår i: Energy Policy. - : Elsevier BV. - 0301-4215. ; 66, s. 484-495
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Tidskriftsartikel (refereegranskat)abstract
- Despite the long history of cook stove programs, very few have been successful, often only in areas where biomass is purchased or there is a biomass shortage. Several studies have described how rural households generally rely on several different fuels; which fuels are used may depend on various household characteristics such as location and income. This article explores possible consequences of variations in fuel usage for improved cook stove programs and how this may vary between different areas. Reductions of CO2 equivalent emissions and monetary savings are calculated for hypothetical cook stove deployment using data from a rural energy survey in the Vinh Phdc province of northern Vietnam. The results indicate that the areas may respond differently to the various stove options, both in terms of economy and emission reductions. Furthermore, there are large differences in emission reduction calculations when only Kyoto-gases are included and when non-Kyoto greenhouse agents are added. Assumptions regarding household behavior and stove efficiencies have large impacts on the results, indicating a need for further research on how improved cook stoves may influence households' fuel choices.
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