| 1. |
- Allison, Robert S., et al.
(författare)
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Perspectives on the definition of visually lossless quality for mobile and large format displays
- 2018
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Ingår i: Journal of Electronic Imaging (JEI). - 1017-9909 .- 1560-229X. ; 27:5, s. 1-23
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Tidskriftsartikel (refereegranskat)abstract
- Advances in imaging and display engineering have given rise to new and improved image and videoapplications that aim to maximize visual quality under given resource constraints (e.g., power, bandwidth).Because the human visual system is an imperfect sensor, the images/videos can be represented in a mathematicallylossy fashion but with enough fidelity that the losses are visually imperceptible—commonly termed“visually lossless.” Although a great deal of research has focused on gaining a better understanding ofthe limits of human vision when viewing natural images/video, a universally or even largely accepted definitionof visually lossless remains elusive. Differences in testing methodologies, research objectives, and targetapplications have led to multiple ad-hoc definitions that are often difficult to compare to or otherwise employ inother settings. We present a compendium of technical experiments relating to both vision science and visualquality testing that together explore the research and business perspectives of visually lossless image quality,as well as review recent scientific advances. Together, the studies presented in this paper suggest that a singledefinition of visually lossless quality might not be appropriate; rather, a better goal would be to establish varyinglevels of visually lossless quality that can be quantified in terms of the testing paradigm.
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| 2. |
- DeCarolis, Joseph, et al.
(författare)
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Formalizing best practice for energy system optimization modelling
- 2017
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Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 194, s. 184-198
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Forskningsöversikt (refereegranskat)abstract
- Energy system optimization models (ESOMs) are widely used to generate insight that informs energy and environmental policy. Using ESOMs to produce policy-relevant insight requires significant modeler judgement, yet little formal guidance exists on how to conduct analysis with ESOMs. To address this shortcoming, we draw on our collective modelling experience and conduct an extensive literature review to formalize best practice for energy system optimization modelling. We begin by articulating a set of overarching principles that can be used to guide ESOM-based analysis. To help operationalize the guiding principles, we outline and explain critical steps in the modelling process, including how to formulate research questions, set spatio-temporal boundaries, consider appropriate model features, conduct and refine the analysis, quantify uncertainty, and communicate insights. We highlight the need to develop and refine formal guidance on ESOM application, which comes at a critical time as ESOMs are being used to inform national climate targets.
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| 3. |
- Dreier, Dennis, 1990-
(författare)
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Transition Technologies for Electrification and Optimisation of Bus Transport Systems
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The topical issue of climate change has increasingly become important as scenarios indicate an increase of 2.5–7.8°C in the global mean temperature by the end of this century, if no greenhouse gas emissions are reduced. The transport sector depends strongly on fossil fuels and has been therefore considered as one key sector concerning climate change mitigation. In this regard, a key role is played by cities, since progressing urbanisation will presumably lead to a higher demand for urban transport.This doctoral thesis addresses the transition phase of public bus transport systems by exploring electrification as a vector for decarbonisation. The C40-city of Curitiba in Southern Brazil is used as a case study. The research is of explorative and empirical nature. Quantitative research methods are applied to compare bus technologies as well as new optimisation models and planning tools are developed to support data analytics and research in the areas of simulation, optimisation and (long-term) planning of energy and transport systems at different levels of consideration.The results from the comparison of different buses show large potentials to save energy and reduce emissions during the operation phase, for example, when using hybrid-electric or plug-in hybrid-electric buses instead of conventional buses. Moreover, energy savings in the operation phase also imply avoidance of fuel production and supply. Additionally, electrified buses can also reduce operational uncertainty caused by varying driving cycles and fluctuating fuel prices concerning an absolute variation of both energy use and fuel cost in the operation phase.A real-time optimisation model was developed, and its concept tested to estimate potentials for energy savings and all-electric operation from the operational optimisation of a plug-in hybrid-electric bus fleet. Different management strategies were simulated concerning the charging schedule and all-electric operation of the bus fleet. While energy savings can be significantly increased through a structural change towards more electrified buses, a large potential to increase the total all-electric operation of the bus fleet was estimated through operational optimisation. Consequently, both a structural change and operational optimisation should be jointly applied to maximise the benefits gained from electrification in a bus transport system.The software system OSeMOSYS-PuLP was developed for empirical deterministic-stochastic modelling based on the OSeMOSYS modelling framework, which enables the use of a Monte Carlo simulation. The open source design of the tool shall enhance transparency and trustworthiness in studies. It is transferable to many cases and makes it possible for analysts and researchers to generate new sets of conclusions together with associated probability distributions considering the use of real-world datasets, e.g. from open data initiatives as the one in Curitiba.In summary, the research findings, applied methods and developed tools can be used to support and inform analysts and decision-makers in the area of transport and energy systems planning in data-driven decision-making processes to develop and assess different technological options and strategies at different levels while considering associated uncertainties.
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| 4. |
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| 5. |
- Forsberg, Jonas, 1982-
(författare)
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On the road to climate neutral Swedish transportation: Energy system modelling to support the transition at national, regional, and local levels
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Transportation is a critical pillar of modern society. Over the past decades, growth in mobility of people and goods have been both enabled by and dependent upon fossil fuels. Strong action is needed to break this dependence in order to reduce CO2. The overall aim of this thesis is to support the transition towards climate neutral transportation in Sweden considering local, regional, and national settings, by use of TIMES-based ESOMs. This is addressed by i) developing and adapting transport sector representation in TIMES models considering context specific conditions and preferences, ii) applying the models to define and explore alternative long-term scenarios that meet the overall goals, iii) and identify key measures and policy implications for achieving climate neutral transportation.In Paper I (Local setting) key considerations and requirements in respect of modelling local energy transition of transportation in a TIMES energy system modelling framework was outlined. The model was then applied to address potential trade-offs between global climate concerns and local air quality issues (Paper II – Local setting). The results showed that decarbonisation with biofuels does little to enhance local air quality, while zero-emission vehicles – that eliminate all local tailpipe emissions – can induce significant upstream CO2 emissions (from energy supply sectors). Comprehensive multi-level strategies are needed to drastically reduce both CO2 and local air pollutants. In Paper III (Regional setting), a participatory modelling approach was applied that involved local practitioners from 15 municipalities. The model results showed that strong national policies can drive down CO2 emissions drastically, and that the impacts from sub-national strategies was very limited under these policies. Still, during the discussions with local practitioners it was emphasized that local action is needed for enabling the measures seen as cost-efficient in the model analysis.The TIMES-Sweden model was adapted and used to explore key decarbonisation options in passenger and freight transportation, in a whole-energy-systems perspective. The model was disaggregated to capture underlying contextual heterogeneity in passenger transportation found across the country (Paper IV – National setting). The results showed that different policy strategies have different implications depending on the context, thus, underpinning a shift from one-size-fits-all policies into more regionally tailored strategies. Next (Paper V – National setting), the same model was used to investigate principally different modes of decarbonising domestic freight transportation. The results showed that road freight electrification reduces total demand for electricity over the entire energy system compared to the biofuel and the e-fuel pathways respectively, while also freeing biomass for other purposes than producing biofuels for road vehicles.Finally, the usefulness of ESOMs to identify policies to accelerate the decarbonization of transportation has been demonstrated, while outlining some challenges. For local level, the necessary data to calibrate the model was often not available, or available but with a system boundary representation incompliant with the model approach (e.g., fuel statistics). At the national level, a new approach was introduced that capture the underlying contextual factors of different actors. While capturing differences between urban, suburban and rural conditions, more research is needed to identify policies that ensure a just transition across socioeconomic groups.
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| 6. |
- Im, Annie, et al.
(författare)
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Risk Factors for Graft-versus-Host Disease in Haploidentical Hematopoietic Cell Transplantation Using Post-Transplant Cyclophosphamide
- 2020
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Ingår i: Biology of blood and marrow transplantation. - : Elsevier BV. - 1083-8791 .- 1523-6536. ; 26:8, s. 1459-1468
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Tidskriftsartikel (refereegranskat)abstract
- Post-transplant cyclophosphamide (PTCy) has significantly increased the successful use of haploidentical donors with a relatively low incidence of graft-versus-host disease (GVHD). Given its increasing use, we sought to determine risk factors for GVHD after haploidentical hematopoietic cell transplantation (haplo-HCT) using PTCy. Data from the Center for International Blood and Marrow Transplant Research on adult patients with acute myeloid leukemia, acute lymphoblastic leukemia, myelodysplastic syndrome, or chronic myeloid leukemia who underwent PTCy-based haplo-HCT (2013 to 2016) were analyzed and categorized into 4 groups based on myeloablative (MA) or reduced-intensity conditioning (RIC) and bone marrow (BM) or peripheral blood (PB) graft source. In total, 646 patients were identified (MA-BM = 79, MA-PB = 183, RIC-BM = 192, RIC-PB = 192). The incidence of grade 2 to 4 acute GVHD at 6 months was highest in MA-PB (44%), followed by RIC-PB (36%), MA-BM (36%), and RIC-BM (30%) (P = .002). The incidence of chronic GVHD at 1 year was 40%, 34%, 24%, and 20%, respectively (P < .001). In multivariable analysis, there was no impact of stem cell source or conditioning regimen on grade 2 to 4 acute GVHD; however, older donor age (30 to 49 versus <29 years) was significantly associated with higher rates of grade 2 to 4 acute GVHD (hazard ratio [HR], 1.53; 95% confidence interval [CI], 1.11 to 2.12; P = .01). In contrast, PB compared to BM as a stem cell source was a significant risk factor for the development of chronic GVHD (HR, 1.70; 95% CI, 1.11 to 2.62; P = .01) in the RIC setting. There were no differences in relapse or overall survival between groups. Donor age and graft source are risk factors for acute and chronic GVHD, respectively, after PTCy-based haplo-HCT. Our results indicate that in RIC haplo-HCT, the risk of chronic GVHD is higher with PB stem cells, without any difference in relapse or overall survival.
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| 7. |
- Jewell, Jessica, 1982, et al.
(författare)
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Reply to: Why fossil fuel producer subsidies matter
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 578:7793, s. E5-E7
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- López, A., et al.
(författare)
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Laboratory characterization and astrophysical detection of vibrationally excited states of vinyl cyanide in Orion-KL
- 2014
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 572
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Tidskriftsartikel (refereegranskat)abstract
- Context. We perform a laboratory characterization in the 18–1893 GHz range and astronomical detection between 80–280 GHz in Orion-KL with IRAM-30 m of CH2CHCN (vinyl cyanide) in its ground and vibrationally excited states. Aims. Our aim is to improve the understanding of rotational spectra of vibrationally excited vinyl cyanide with new laboratory data and analysis. The laboratory results allow searching for these excited state transitions in the Orion-KL line survey. Furthermore, rotational lines of CH2CHCN contribute to the understanding of the physical and chemical properties of the cloud. Methods. Laboratory measurements of CH2CHCN made on several different frequency-modulated spectrometers were combined into a single broadband 50–1900 GHz spectrum and its assignment was confirmed by Stark modulation spectra recorded in the 18–40 GHz region and by ab-initio anharmonic force field calculations. For analyzing the emission lines of vinyl cyanide detected in Orion-KL we used the excitation and radiative transfer code (MADEX) at LTE conditions. Results. Detailed characterization of laboratory spectra of CH2CHCN in nine different excited vibrational states: ?11 = 1, ?15 = 1, 2) ⇔ (?10 = 1,?15 = 1) ⇔ (?11 = 1,?14 = 1), and ?11 = 4 are determined, as well as the detection of transitions in the ?11 = 2and ?11 = 2, ?10 = 1 ⇔ (?11 = 1,?15 = 1), ?11 = 3/?15 = 2/?14 = 1, (?11 = 1,?10 = 1) ⇔ (?11 = 2,?15 = 1), ?9 = 1, (?11 = 1,?15 = The rotational transitions of the ground state of this molecule emerge from four cloud components of hot core nature, which trace the ?11 = 3 states for the first time in Orion-KL and of those in the ?10 = 1 ⇔ (?11 = 1,?15 = 1) dyad of states for the first time in space. physical and chemical conditions of high mass star forming regions in the Orion-KL Nebula. The lowest energy vibrationally excited states of vinyl cyanide, such as ?11 = 1 (at 328.5 K), ?15 = 1 (at 478.6 K), ?11 = 2 (at 657.8 K), the ?10 = 1 ⇔ (?11 = 1,?15 = 1) dyad (at 806.4/809.9 K), and ?11 = 3 (at 987.9 K), are populated under warm and dense conditions, so they probe the hottest parts of the Orion-KL source. The vibrational temperatures derived for the ?11 = 1, ?11 = 2, and ?15 = 1 states are 252 ± 76K, 242 ± 121K, column density of CH2CHCN in the ground state is (3.0 ± 0.9) × 1015 cm−2. We report the detection of methyl isocyanide (CH3NC) and 227 ± 68K, respectively; all of them are close to the mean kinetic temperature of the hot core component (210K). The total for the first time in Orion-KL and a tentative detection of vinyl isocyanide (CH2CHNC). We also give column density ratios between the cyanide and isocyanide isomers, obtaining a N(CH3NC)/N(CH3CN) ratio of 0.002. Conclusions. Laboratory characterization of many previously unassigned vibrationally excited states of vinyl cyanide ranging from microwave to THz frequencies allowed us to detect these molecular species in Orion-KL. Column density, rotational and vibrational temperatures for CH2CHCN in their ground and excited states, and the isotopologues have been constrained by means of a sample of more than 1000 lines in this survey.
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| 9. |
- Moksnes, Nandi, 1982-
(författare)
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Exploring spatial and temporal resolution in energy systems modelling : a model-based analysis focused on the developing electricity systems
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The energy system is undergoing a transition in many parts of the world with this transition being driven by several factors such as climate change, and economic and social development. Agenda 2030, with its 17 Sustainable Development Goals (SDGs), has set the direction on where development should be focussed. There are still around 675 million people who lack access to electricity (SDG7), mainly in Sub-Saharan Africa. The energy system is also responsible for emitting most greenhouse gas (GHG) emissions and is closely connected to SDG 13, climate action.Energy models can provide insight into the implications of different interventions in the system. However, the transition also poses new challenges for energy modelling. New spatiotemporal questions arise with 1) the penetration of renewable technologies to mitigate GHG emissions, with location-specific intermittent supply options such as wind and solar PV panels, and 2) the low share of the population living near the existing electricity network in many Sub-Saharan countries and the decreasing cost of off-grid and mini-grid supply options.This change increases the number of technologies and details needed in the system which in turn increases complexity in the models. Complexity can be defined in terms of four aspects: spatial, temporal, mathematical and, system scope. However, more detail, both parametrical and structural, can introduce more potential errors and uncertainty into the model. Therefore, energy models should be as simple as possible and as complex as necessary.This thesis aims to give quantifiable and qualitative insights into the mathematical, spatial, and temporal aspects of energy systems modelling for both national and regional system scopes, along with their policy implications. The thesis explores the trade-offs between which mathematical method is applied when modelling electricity access, and the global sensitivity of parametrical and structural parameters in ESOMs.The method for achieving the aim of the thesis uses a four-step approach. First, the geospatial electrification problem is explored by developing two different models, a linear programming model, using the model generator GEOSeMOSYS, and a heuristic method, soft-linking the open-source tools OnSSET and OSeMOSYS. Second, these two models are compared in order to understand the differences between them with respect to computational effort, results, insight, and effectiveness in modelling electricity access in a developing country. Third, the linear programming model developed for this thesis is then explored using the method of Morris global sensitivity analysis to understand the importance of spatial and temporal resolution compared to other parameters such as demand, discount rate, and capital cost. Fourth and finally, the global sensitivity analysis method of factor mapping, using scenario discovery, is explored to understand parameters that determine cost and low carbon futures in the regional multi-country energy systems optimisation model ‘South America Model Base’ (SAMBA).The results show that the two methods for optimising electrification show similar trends when the demand is changed, with low demand predominantly resulting in PV panels and batteries to serve the formerly unelectrified population, while higher demand results in more grid-connected households. The demand level and profile for newly electrified households result in different service levels and possibilities for adding more appliances over time. The competitiveness of PV panels with batteries decreases significantly when the demand profile increases during the night. The two methods in this thesis have different solution times with the linear programming method having a much longer solution time, furthermore, the mathematical approaches to solve the transmission network are different, and both methods have trade-offs in their results. These trade-offs are in the mathematical approach where OnSSET uses a one-at-the-time optimisation leading to a suboptimal overall network, and GEOSeMOSYS rely on the assumption of linearity, which leads to very small incremental installations of transmission lines.The global sensitivity analysis of GEOSeMOSYS for electricity access showed that the structural parameters, spatial and temporal resolution, influence the result parameters and cannot be simplified without changing the results. The temporal resolution had a greater influence on the assessed results parameters than the spatial resolution, indicating that it is more significant. For the South American system, the parameters that determine low carbon emission pathways are low/medium demand and low/medium discount rates.This thesis has therefore shown that, even though models should be as simple as possible, the spatial and temporal resolution cannot be simplified to a one-node analysis or low temporal resolution without this affecting the results. The mathematical choice for selecting the method of electricity access was analysed and trade-offs were highlighted. The main trade-off was in the network expansion where both methods use approximations that can lead to over/underestimating the investment need. The soft-linked method is a good option to understand a higher level to explore electricity access. If the question is more complex (e.g., adding transportation, heating and cooling), then GEOSeMOSYS provides more readily available options for expanding the analysis, but at a coarse spatial resolution. Demand is a critical parameter in energy models, as is shown in this thesis, and determines both the cost and the potential for achieving low carbon futures. Therefore, including more demand functionalities (such as demand side management and price elasticity) in energy models could help to further detail future demands, and this is identified as future work.
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| 10. |
- Rogan, Fionn, et al.
(författare)
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LEAPs and Bounds-an Energy Demand and Constraint Optimised Model of the Irish Energy System
- 2014
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Ingår i: Energy Efficiency. - : Springer Science and Business Media LLC. - 1570-646X .- 1570-6478. ; 7:3, s. 441-466
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Tidskriftsartikel (refereegranskat)abstract
- This paper builds a model of energy demand and supply for Ireland with a focus on evaluating, and providing insights for, energy efficiency policies. The demand-side comprises sectoral sub-models, with a detailed bottom-up approach used for the transport and residential sectors and a top-down approach used for the industry and services sectors. The supply side uses the linear programming optimisation features of the Open Source Energy Modelling System applied to electricity generation to calculate the least-cost solution. This paper presents the first national level model developed within the Long Range Energy Alternatives Planning software to combine detailed end-use analysis on the demand side with a cost-minimising optimisation approach for modelling the electricity generation sector. Through three scenarios over the period 2009-2020, the model examines the aggregate impact on energy demand of a selection of current and proposed energy efficiency policies. In 2020, energy demand in the energy efficiency scenario is 8.6 % lower than the reference scenario and 11.1 % lower in the energy efficiency + scenario.
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