| 1. |
- Brodin, Gert, et al.
(författare)
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Excitation of electromagnetic wake fields in a magnetized plasma
- 1998
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Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1063-651X .- 1095-3787. ; 57:6, s. 7041-7047
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Tidskriftsartikel (refereegranskat)abstract
- We consider propagation of short electromagnetic pulses in a magnetized plasma. A self-consistent system of equations describing wake-field generation in the weakly nonlinear limit is derived. Due to the external magnetic field, the generated wake field becomes partially electromagnetic. The equations are applicable for arbitrary directions of propagation as compared to the external magnetic field. The conservation laws for the system are discussed in detail. The energy decrease rate and the frequency decrease rate of the short pulse are determined
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| 2. |
- Häggquist, Elisabeth
(författare)
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The Economic Value and Adoption of Geological Information in Sweden
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The purposes of this thesis are to: (a) provide a review of previous research on the economic value of geological information, including the identification of important lessons from such work: and (b) assess the current use and non-use of geological information in Swedish municipalities. The thesis consists of three papers all related to the assessment or adoption of geological information.Paper I provides a review of previous research on the economic value of geological information and other earth observations as well as related products, services and infrastructure. Furthermore, the paper identifies important lessons and issues that require increased attention in future research. The review of prior research shows that significant economic benefits are attached to the use of geological information. The value of geological information has typically been measured in terms of avoided costs. Still, it is difficult to compare results across studies since they differ in scope and make alternative assumptions concerning which sectors to cover. Furthermore, previous research is not uniform in its treatment of potential (rather than only existing) users, and it employs varying conceptions of avoided costs. The paper concludes that future research should devote more attention to the public and experience good characteristics of this type of information, thus highlighting the preconditions for information adoption as well as addressing the role of potential users. A number of specific methodological challenges also deserve further scrutiny in future research, such as the use of discount rates and benefit-transfer approaches in the empirical context of geological information.Based on the results of Paper I it is important to also analyze what, beyond technological advances, influences the adoption of geological information. Paper II and III investigate the determinants of adopting geological information in the public sector with an emphasis on Swedish municipalities. Paper II contributes to the literature by theoretical explanations and empirical findings on individual and organizational effects influencing the adoption of geological information. In this paper an information adoption model is proposed and tested against data collected from 677 officials in Swedish municipalities. The model is estimated using linear probability (LPM) and instrument variable generalized method of moment (IV-GMM) approaches. The results suggest that perceived advantages have the largest effect on the likelihood of adopting geological information, but also follow-up education (motivation) and gender are found to affect adoption behavior. In addition, the results also indicate a group effect within working units. Some implications of the findings and future research areas are discussed.Paper III further investigates the adoption of geological information in the public sector by considering social effects (collegial advice), and whether the information is jointly adopted with related information. The related information considered in this paper is other geoinformation such as map data, demographic information concerning population or building information. The empirical analysis builds on the survey sent out to officials at Swedish municipalities. The information adoption model is estimated using probit and bivariate probits. The results suggest that the adoption of geological and related information is a joint and complementary decision. It is also found that collegial advice, perceived skills from education, motivation to adopt, perceived advantage, gender and working unit affect the likelihood of adopting geological information.
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| 3. |
- Johansson, Jonny, et al.
(författare)
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Project: EISCAT 3D
- 2007
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Annan publikation (populärvet., debatt m.m.)
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| 4. |
- Lundberg, Jonas, et al.
(författare)
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Perturbation method for the Vlasov-Poisson system
- 1998
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Ingår i: Journal of Plasma Physics. - 0022-3778 .- 1469-7807. ; 60, s. 181-192
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Tidskriftsartikel (refereegranskat)abstract
- A perturbation method for the Vlasov-Poisson system is presented. It is self-consistent and entirely based on Lie transformations, which are considered as active transformations, generating the dynamics of the particle distribution function in the space of distribution functions. The main result is a set of three equations that forms a good starting point for a wide variety of problems concerning nonlinear wave propagation. Besides being efficient, the new perturbation method is systematic and therefore also suited for the use of computer algebra.
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| 5. |
- Rouchitsas, Alexandros, 1980-
(författare)
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Virtual Human Characters for Autonomous Vehicle-to-Pedestrian Communication
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Pedestrians base their street-crossing decisions on both vehicle-centric cues, like speed and acceleration, and driver-centric cues, like gaze direction and facial expression. In the future, however, drivers of autonomous vehicles will be preoccupied with non-driving related activities and thus unavailable to provide pedestrians with relevant communicative cues. External human-machine interfaces (eHMIs) hold promise for filling the expected communication gap by providing information about the current state and future behaviour of an autonomous vehicle, to primarily ensure pedestrian safety and improve traffic flow, but also promote public acceptance of autonomous vehicle technology. The aim of this thesis is the development of an intuitive, culture-transcending eHMI, that can support multiple pedestrians in parallel make appropriate street-crossing decisions by communicating pedestrian acknowledgement and vehicle intention. In the proposed anthropomorphic eHMI concept, a virtual human character (VHC) is displayed on the windshield to communicate pedestrian acknowledgement and vehicle intention via gaze direction and facial expression, respectively. The performance of different implementations of the proposed concept is evaluated in the context of three monitor-based, laboratory experiments where participants performed a crossing intention task. Four papers are appended to the thesis. Paper I provides an overview of controlled studies that employed naive participants to evaluate eHMI concepts. Paper II evaluates the effectiveness of the proposed concept in supporting a single pedestrian or two co-located pedestrians make appropriate street-crossing decisions. Paper III evaluates the efficiency of emotional facial expressions in communicating non-yielding intention. Paper IV evaluates the efficiency of emotional and conversational facial expressions in communicating yielding and non-yielding intention. An implementation of the proposed anthropomorphic eHMI concept where a male VHC communicates non-yielding intention via an angry expression, cruising intention via cheek puff, and yielding intention via nod, is shown to be both highly effective in ensuring the safety of a single pedestrian or even two co-located pedestrians without compromising traffic flow in either case, and the most efficient. Importantly, this level of effectiveness is reached in the absence of any explanation of the rationale behind the eHMI concept or training to interact with it successfully.
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