| 1. |
- Ekberg, Kristoffer, 1990-, et al.
(författare)
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A Comparison of Optimal Gear Shifts for Stiff and Flexible Driveshafts During Accelerations
- 2020
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Konferensbidrag (refereegranskat)abstract
- Reducing the fuel consumption is important and much development work is on engine optimization for best stationary fuel consumption. Here, a solution is developed for the transient operation to get fuel optimal accelerations, considering the actuation of fuel injection, wastegate control and gear utilization. The transient acceleration scenario studied is; a truck is approaching a red light at slow rolling speed, the light turns green and the truck shall be accelerated to 50 km/h with minimum fuel. Optimal control is used to find the fuel optimal control strategies. By using a dynamic engine model, taking the turbocharger dynamics into consideration, the engine air fuel ratio is taken into account. The differences and similarities between a stiff and flexible driveline model, are analyzed. The results show that the most dominating effect is the turbocharger dynamics of the engine. The two drivelines have similar gear changing strategies while the finer details differ due to the additional degrees of freedom that are present in the flexible driveline.
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| 2. |
- Ekberg, Kristoffer, 1984, et al.
(författare)
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A Question of Utter Importance: The Early History of Climate Change and Energy Policy in Sweden, 1974–1983
- 2023
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Ingår i: Environment and History. - 1752-7023 .- 0967-3407. ; 29:3, s. 399-421
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Tidskriftsartikel (refereegranskat)abstract
- This paper studies early arguments in Sweden for combating climate change. We show how scientific results in relation to climate change entered the political sphere as part of the debate on energy in the 1970s, a process we propose to name energysation. We argue that the use of climate science by pro-nuclear political actors served as a way of maintaining a course set by a high-energy society while simultaneously trying to outmanoeuvre the growing environmental anti-nuclear and low-energy movement. When the pro-nuclear power side met with resistance, this led to a displacement of climate change knowledge away from the realm of the national political sphere and specific energy forms, a process we conceptualise as de-energysation. By highlighting conflicts and the political framings of climate change in the early years 1974–1983, we suggest that the history of these frames influences current delay in climate change mitigation and limits the range of actions and ways of addressing the ongoing climate emergency.
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| 3. |
- Ekberg, Kristoffer, 1984, et al.
(författare)
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A Road to Denial: Climate Change and Neoliberal Thought in Sweden, 1988-2000
- 2022
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Ingår i: Contemporary European History. - 0960-7773 .- 1469-2171. ; 31:4, s. 627-644
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Tidskriftsartikel (refereegranskat)abstract
- Neoliberal and conservative actors, financed by the fossil fuel industry, have been identified as crucial parts of a climate change denialist counter movement since at least the 1980s. We claim that this intersection stems from more than just vested interest fuelling advocacy groups. By focusing on the intellectual developments and social networks of core actors in the environmental debate in Sweden, we trace the history of opposition to environmental regulation in a country proclaiming to be an environmental pioneer. Our analysis shows that while the framing of climate change in terms of complexity initially provided actors with arguments for neoliberal policies, the obstruction of climate and environmental action was steeped in a neoliberal thought style. Our findings demonstrate the importance of scrutinising economic paradigms and thought styles that has enabled the delay of climate policy as well as the continued need for historical and geographically specific studies of obstruction.
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| 4. |
- Ekberg, Kristoffer, et al.
(författare)
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Alternativ arbetsglädje : om lyckokänslor i arbetslivet i skiftet mellan 1970- och 1980-tal
- 2017
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Ingår i: Känslornas revolution : kärlek, ilska och lycka på 1970-talet - kärlek, ilska och lycka på 1970-talet. - 9789198327540 ; , s. 214-236
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- 1970-talets känslomönster utmärktes av en dröm om mänsklig gemenskap och befrielse från fördomar samt en vilja att komma i kontakt med sig själv och andra, att söka det äkta, det naturliga, det autentiska och nå en öppenhet. Man ville att det skulle kännas på ett visst sätt att arbeta, vila, skapa, vara solidarisk, konsumera, ha sex, vara barn, förälder, man och kvinna, ung och gammal, överordnad och underordnad. Befrielse och öppenhet var nyckelord. Här skärskådar en grupp historiker, idé- och filmhistoriker detta färgstarka och omvälvande decennium. De granskar allt från politik och medier till kärleksliv och moral. Fram växer en fascinerande bild av hur känslorna blir till regler och mönster – och att normerna för vad människor förväntas känna och faktiskt känner varierar i tid och rum.
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| 5. |
- Ekberg, Kristoffer, 1984, et al.
(författare)
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Crafting counter frames: Shell's corporate strategies in the Nigeria campaign, 1995–1998
- 2023
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Ingår i: Extractive Industries and Society. - : Elsevier BV. - 2214-790X .- 2214-790X. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- In this article we analyse the actions of Royal Dutch/Shell (since 2021, Shell) considering the campaign against them and their operations in Nigeria in the mid-1990s. Using the concept counter-frames we analyse Shell's internal documentation of the campaign to understand how a multinational extractive industry engaged in disputes of legitimacy and against critiques of their operations. Focusing on frame disputes in the campaign the article contributes with an understanding of the practical development of counter-frames. Using historical records in the form of internal situational reports circulated among subsidiaries during the campaign period we show how different strategies such as lobbying, individual contacts, embedded journalists, production of information products and the development of social programs all were developed through a historical and contingent process between subsidiaries, the public and social movement organisations. Rather than solely identifying strategies used by oil companies the paper expose and analyse the internal logics of Shell which add important insights on the development of corporate strategies in in light of environmental and human right campaigns, legislations and standards.
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| 6. |
- Ekberg, Kristoffer, et al.
(författare)
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Cycle Beating - An Analysis of the Boundaries During Vehicle Testing
- 2016
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Ingår i: IFAC PAPERS ONLINE. - : ELSEVIER SCIENCE BV. ; , s. 657-664
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Konferensbidrag (refereegranskat)abstract
- Todays vehicle industry is strictly controlled by environmental legislations. The vehicle industry is spending much money out reducing the fuel consumption and fulfilling the emission requirements to make sales possible in different regions in the world. Before introducing; a vehicle on the market, it is tested according to standardized driving cycles to specify the vehicle pollutant emissions and fuel consumption. These cycles allow some deviation from the reference vehicle speed during tests, e.g. NEDC allows deviations of +/- 2 km/h and +/- 1 s. This paper uses dynamic programming to find fuel optimal velocity profiles, given the allowed deviations of +/- 2 km/h and +/- 1 s from reference speed during drive cycle test. By taking advantage of the allowed deviation, the fuel consumption can be reduced by up to 16.56 % according to model results, ruoriing NEDC if gear selections are unrestricted (i.e. using automatic gearbox), and up to 5.90 % if changing gears according to the specifications in the drive cycle. Two different optimization goals are investigated, minimum amount of mass fuel consumed and best mileage. (C) 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.
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| 7. |
- Ekberg, Kristoffer, et al.
(författare)
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Development and Analysis of Optimal Control Strategy for Gear Changing Patterns During Acceleration
- 2019
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Ingår i: IFAC PAPERSONLINE. - : ELSEVIER. ; , s. 316-321
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Konferensbidrag (refereegranskat)abstract
- Vehicle speed planning for heavy duty vehicles is a powerful tool to reduce the fuel consumption, and thereby the emissions released from the vehicle. By optimizing a driving mission for lowest possible fuel consumption, while still fulfilling the mission deadlines, the fuel consumption could be reduced over that specific mission. If the vehicle is driven by a combustion engine, the engine efficiency will be dependent on the load and speed requirements from the vehicle. By having a gearbox between the engine and the wheels, the engine operating points could be selected by choosing the appropriate gear. When optimizing gear changes, different model complexities can be used. To solve a gear change problem during acceleration, some key aspects needs to be taken into account, for example the loss of propulsion power when disengaging the clutch, how much clutch slip should be allowed, the time it takes for the gearbox to change the gear. The paper presents a method how to formulate and solve a fuel optimal acceleration of a vehicle, where the gear selections are in focus. The method is used to find which gears that should be used to perform a fuel optimal acceleration to a predefined vehicle speed. (C) 2019, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.
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| 8. |
- Ekberg, Kristoffer, et al.
(författare)
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Electrification of a Heavy-Duty CI Truck-Comparison of Electric Turbocharger and Crank Shaft Motor
- 2021
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 14:5
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Tidskriftsartikel (refereegranskat)abstract
- A combustion engine-driven vehicle can be made more fuel efficient over some drive cycles by, for example, introducing electric machines and solutions for electrical energy storage within the vehicles driveline architecture. The possible benefits of different hybridization concepts depend on the architecture, i.e., the type of energy storage, and the placement and sizing of the different driveline components. This paper examines a diesel electric plug-in hybrid truck, where the powertrain includes a diesel engine supported with two electric motors, one supporting the crank shaft and one the turbocharger. Numerical optimal control was used to find energy-optimal control strategies during two different accelerations; the trade-off between using electrical energy and diesel fuel was evaluated using a simulation platform. Fixed-gear acceleration was performed to evaluate the contribution from the two electric motors in co-operation, and individual operation. A second acceleration test case from 8 to 80 km/h was performed to evaluate the resulting optimal control behavior when taking gear changes into account. A cost factor was used to relate the cost of diesel fuel to electrical energy. The selection of the cost factor relates to the allowed usage of electrical energy: a high cost factor results in a high amplification from electrical energy input to total system energy savings, whereas a low cost factor results in an increased usage of electrical energy for propulsion. The difference between fixed-gear and full acceleration is mainly the utilization of the electric crank shaft motor. For the mid-range of the cost factors examined, the crank shaft electric motor is used at the end of the fixed-gear acceleration, but the control sequence is not repeated for each gear during the full acceleration. The electric motor supporting the turbocharger is used for higher cost factors than the crank shaft motor, and the amplification from electrical energy input to total energy savings is also the highest.
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| 9. |
- Ekberg, Kristoffer, 1984
(författare)
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Expertise in conflict – Bert Bolin and Tor Ragnar Gerholm in the debate on energy and environment
- 2022
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Since the political breakthrough of modern environmental problems in the late 1960s, scientists have repeatedly engaged in the public debate on issues such as energy, economic growth, and climate change. Scientific findings have been invoked with the aim of getting politicians and society to act. At the same time, the presence in the public debate has highlighted conflicts over scientific results and societal change. Such conflicts have been studied in the US context to a great extent but far less is known about similar conflicts in other countries. Building on research where we have identified such debates in Sweden, this presentation sketches the outline of a proposed project tracing the conflicts over energy, environment, and climate change through the lens of two key actors. Tor Ragnar Gerholm and Bert Bolin both born in 1925 and died in 2007, came during their careers to become central voices in Swedish energy policy and in the debate about environmental threats, but acted in diametrically different ways. In the presentation I introduce some early findings on two actor’s positions and the “technologies of legitimacy” they used to bring forth their scientific findings and political perspectives.
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| 10. |
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