| 1. |
- Almroth, Andreas, et al.
(författare)
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Further development of SAMPERS and modeling of urban congestion
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The need to more precisely represent the consequences of congestion mitigation policies in urban transport systems calls for replacement of the static equilibrium assignment by DTA in the integrated travel demand and traffic assignment models. Despite of the availability of DTA models and despite of the conceptual clarity of how such integration should take place, only few operational model systems have been developed for large-scale applications. We report on replacement of the static traffic assignment by two different DTAs in the four stage demand model for the Greater Stockholm region: the macroscopic analytic Visum DUE and microscopic simulation Transmodeler. First results show that even without systematic calibration the DTA is in reasonable agreement with observed traffic counts and travel times. The presented experiments did not reveal striking difference between using macroscopic and microscopic assignment package. However, given the clear trend to microscopic modeling and simulation on the travel demand side, the use of micro-simulation-based DTA package appears more natural from system integration perspective.
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| 2. |
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| 3. |
- Cats, Oded, et al.
(författare)
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A dynamic stochastic model for evaluating congestion and crowding effects in transit systems
- 2016
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Ingår i: Transportation Research Part B. - : Elsevier. - 0191-2615 .- 1879-2367. ; 89, s. 43-57
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Tidskriftsartikel (refereegranskat)abstract
- One of the most common motivations for public transport investments is to reduce congestion and increase capacity. Public transport congestion leads to crowding discomfort, denied boardings and lower service reliability. However, transit assignment models and appraisal methodologies usually do not account for the dynamics of public transport congestion and crowding and thus potentially underestimate the related benefits. This study develops a method to capture the benefits of increased capacity by using a dynamic and stochastic transit assignment model. Using an agent-based public transport simulation model, we dynamically model the evolution of network reliability and on-board crowding. The model is embedded in a comprehensive framework for project appraisal.A case study of a metro extension that partially replaces an overloaded bus network in Stockholm demonstrates that congestion effects may account for a substantial share of the expected benefits. A cost-benefit analysis based on a conventional static model will miss more than a third of the benefits. This suggests that failure to represent dynamic congestion effects may substantially underestimate the benefits of projects, especially if they are primarily intended to increase capacity rather than to reduce travel times.
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| 4. |
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| 5. |
- Cats, Oded, 1983-, et al.
(författare)
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Learning and adaptation in dynamic transit assignment models for congested networks
- 2020
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Ingår i: Transportation Research Record. - : SAGE Publications. - 0361-1981 .- 2169-4052. ; 2674:1, s. 113-124
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Tidskriftsartikel (refereegranskat)abstract
- The distribution of passenger demand over the transit network is forecasted using transit assignment models which conventionally assume that passenger loads satisfy network equilibrium conditions. The approach taken in this study is to model transit path choice as a within-day dynamic process influenced by network state variation and real-time information. The iterative network loading process leading to steady-state conditions is performed by means of day-to-day learning implemented in an agent-based simulation model. We explicitly account for adaptation and learning in relation to service uncertainty, on-board crowding and information provision in the context of congested transit networks. This study thus combines the underlying assignment principles that govern transit assignment models and the disaggregate demand modeling enabled by agent-based simulation modeling. The model is applied to a toy network for illustration purposes, followed by a demonstration for the rapid transit network of Stockholm, Sweden. A full-scale application of the proposed model shows the day-to-day travel time and crowding development for different levels of network saturation and when deploying different levels of information availability.
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| 6. |
- Geng, Zeyang, 1991, et al.
(författare)
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On-board Impedance Diagnostics Method of Li-ion Traction Batteries Using Pseudo-Random Binary Sequences
- 2018
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Ingår i: 2018 20th European Conference on Power Electronics and Applications, EPE 2018 ECCE Europe.
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Konferensbidrag (refereegranskat)abstract
- This work deals with the on-board impedance measurements of Li-ion batteries on hybrid electric vehicles/electric vehicles by using pseudo-random binary sequences (PRBSs). The impedance of the battery can be related to its state of charge (SOC) and state of health (SOH). However the battery impedance is frequency dependent which makes it difficult to perform the measurement on a pack level in the vehicles. By using an excitation signal like PRBS, it is possible to extract the impedance information of the battery packs. Experiments are performed with different set-ups to verify the PRBS method. A non-parametric method is used to process the data and extract the impedance measurement. Experiments in the laboratory at different state of charge levels and temperatures are made to validate the PRBS method. It is shown that the PRBS method can produce a valid electrochemical impedance spectrum in a limited frequency range, similar to the result from a high accuracy laboratory impedance analyzer. The method is stable at different SOC levels and temperatures. A simulation of the excitation signal in the vehicle is performed where the electric motor is used as the load. It shows that it is possible to some extent to use the driveline in a hybrid electric vehicle/electric vehicle to perform an on-board battery impedance measurement.
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| 7. |
- Ideland, Jens
(författare)
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Spela leka eller låta bli : Guitar Hero som kommunikativ praktik för unga musiker
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Since 2005, the music related console game Guitar Hero has been sold in huge numbers and widely spread. Young people who study and/or play music often have experienced both gaming and music through taking on the game. Recent studies indicate that Guitar Hero affects conditions for music education (Ericsson & Lindgren, 2010) and that children refer to the game in conversation about music and musicality (Hellgren, 2011). In this study, theories on multimodality (Kress & Van Leeuwen, 2001) are used, along with related perspectives on design for learning (Selander, 2008b) and discourse analysis (Gee 2005a), as a starting point for understanding and analysing Guitar Hero gaming as a communicative practice. The overall aim of this study is to explore conditions for young musicians’ communication (and thereby learning) in the communicative practice and context offered by Guitar Hero. The following research questions are generated: ‐ What strategies and discourses are visualised through actions by the informants in this communicative practice? ‐ What affordances and restrictions regarding communication and meaning making (and thereby learning) does this practice offer, when the informants articulate and act in relation to these discourses? In order to answer these questions a gaming session in a youth centre was conducted with a small group of young musicians, who also attended a specialised music programme in an upper secondary school. A video documentation of this session is the main empirical material in this study. The results of the analysis process are formed as case descriptions that visualise important strategies articulated in the informants’ way of handling the gaming situation in question. Further analysis reveals what discourses about Guitar Hero gaming the informant articulates, and what communicative affordances and restrictions are visualised in the current communicative situation. The results indicate that Guitar Hero offers a nuanced communicative practice. Using available communicative resources the informants are able to articulate knowledge of both digital games and music. Doing so they simultaneously express a situated identity, with a clear connectedness to the identity and musicianship articulated in the school context. In the collectively articulated discourse on Guitar Hero as different from playing music, three gamer positions stand out as socially accepted and favoured ways of approaching the game: The serious gamer, The playing gamer and The uninterested gamer. Guitar Hero stands out as a communicative practice offering opportunities to use and express musical knowledge and perception under the condition that this is not articulated as musical knowledge or playing music.
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| 8. |
- Swietlicki, Erik, et al.
(författare)
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Source identification during the Great Dun Fell Cloud Experiment 1993
- 1997
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Ingår i: Atmospheric Environment. - 1352-2310. ; 31:16, s. 2441-2451
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Tidskriftsartikel (refereegranskat)abstract
- A characterisation of the sources influencing the site for the final field campaign of the EUROTRAC subproject GCE (Ground-based Cloud Experiment) at Great Dun Fell, Cumbria, Great Britain in April-May 1993 is presented. The sources were characterised mainly by means of aerosol filter and cascade impactor data, single particle analysis, gas data, data on aromatic organic compounds, cloud water ionic composition, measurements of aerosol size distributions and hygroscopic properties and various meteorological information. Receptor models applied on the aerosol filter and impactor data sets separately revealed two major source types being a marine sea spray source and a long-range transported anthropogenic pollution source. The results of the receptor models were largely consistent with the other observations used in the source identification. Periods of considerable anthropogenic pollution as well as almost pure marine air masses were clearly identified during the course of the experiment.
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| 9. |
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| 10. |
- West, Gabriel, et al.
(författare)
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Amino acid racemization in Quaternary foraminifera from the Yermak Plateau, Arctic Ocean
- 2019
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Ingår i: Geochronology. - : Copernicus GmbH. - 2628-3719. ; 1:1, s. 53-67
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Tidskriftsartikel (refereegranskat)abstract
- Amino acid racemization (AAR) geochronology is a powerful tool for dating Quaternary marine sediments across the globe, yet its application to Arctic Ocean sediments has been limited. Anomalous rates of AAR in foraminifera from the central Arctic were reported in previously published studies, indicating that either the rate of racemization is higher in this area, or inaccurate age models were used to constrain the sediment ages. This study investigates racemization rates in foraminifera from three well-dated sediment cores taken from the Yermak Plateau during the 2015 TRANSSIZ (TRansitions in the Arctic Seasonal Sea Ice Zone) expedition on RV Polarstern. D and L isomers of the amino acids aspartic acid (Asp) and glutamic acid (Glu) were separated in samples of the planktic foraminifer Neogloboquadrina pachyderma and the benthic species Cassidulina neoteretis to quantify the extent of racemization. In total, 241 subsamples were analysed, extending back to marine oxygen isotope stage (MIS) 7. Two previously published power functions, which relate the extent of racemization of Asp and Glu in foraminifera to sample age are revisited, and a comparison is made between the ages predicted by these calibrated age equations and independent geochronological constraints available for the cores. Our analyses reveal an excellent match between ages predicted by a global compilation of racemization rates for N. pachyderma and confirm that a proposed Arctic-specific calibration curve is not applicable at the Yermak Plateau. These results generally support the rates of AAR determined for other cold bottom water sites and further highlight the anomalous nature of the purportedly high rate of racemization indicated by previous analyses of central Arctic sediments.
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