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| 2. |
- Wemming, Hannes, 1984-
(författare)
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Experiments and Modelling of Composite–Aluminium Bolted Joints
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aeronautical industry has always strived towards weight-efficient structures since they improve aircraft performance, enable more fuel or payload, reduce cost of manufacturing and operating the aircraft, and reduce the fuel consumption and emissions. Modern airframes are often built in materials with high strength-toweight and stiffness-to-weight ratio, such as aluminium or fibre composites. Fibre composite materials are becoming increasingly common, requiring bolted joints between composite and aluminium parts. Bolted joints are often weak points in the structure, and understanding their mechanical properties in terms of stiffness and strength is of great importance for designing aircraft that are safe to fly. The aim of the research presented in this licentiate thesis is to improve the understanding of shear-loaded, composite–aluminium, bolted joints in terms of structural compliance, deformation, load distribution, strength and failure, by performing experiments and developing simulation models that describe those experiments. Experiments are performed where the optical digital image correlation (DIC) technique is used to measure the deformation of the test specimen surface during quasistatic load application until specimen failure. The DIC method enables more detailed deformation measurements compared to traditional methods. Data processing algorithms for noise reduction of DIC measurement data are developed and the results are used in a novel way to detect beginning bearing damage within the material by observing the specimen surface. The experimental DIC data is used for adapting models, where the goal is to create a structural element that represents a fastener. A structural element is computationally efficient and suitable for implementation in large scale models of airframe structures in an industrial context. A model is proposed and the selection of parameters for this model are investigated. The parameters are identified by fitting to experimental data. This licentiate thesis is divided into two parts, where the first part gives an introduction and background to the research, while the second part consists of two appended papers.
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| 3. |
- Acke, Filip, 1968, et al.
(författare)
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Influence of the platinum-support interaction on the direct reduction of NOx under lean conditions
- 1998
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Ingår i: Studies in Surface Science and Catalysis. - 0167-2991. ; 116, s. 285-294
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Tidskriftsartikel (refereegranskat)abstract
- Catalysts containing Pt supported on SiC, Al2O3 and ZSM-5 were prepared and studied for NOx reduction by C3H6 in Oz excess under transient (temperature ramps) and steady-state conditions. The maximum NOx reduction activity in the heating ramp experiments was similar for Pt/SiC and Pt/ZSM-5, while Pt/Al2O3 showed higher maximum activity. Both N-2 and N2O formation was observed for all catalysts, although the respective amounts varied with the investigated system. Highest Nz selectivity was observed for Pt/Al2O3. When the NOx reduction activity was studied under steady-state conditions the activity of Pt/Al2O3 decreased substantially (mainly due to a loss in N-2 production). Pt/ZSM-5 became somewhat more selective towards Na production whereas the activity and selectivity of Pt/SiC remained at about the same values as far the heating ramp experiments. Adsorbed species on the surface of the different catalysts were investigated using in-situ FTIR in order to obtain information about the reaction mechanisms. The adsorption of species on Pt/SiC was negligible, while a number of absorption bands were observed for Pt/Al2O3 (N and C containing species, and -NCO) and Pt/ZSM-5 (HC).
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| 4. |
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| 5. |
- Azar, Christian, 1969, et al.
(författare)
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Att jämföra koldioxid och metan – varför GWP inte ger hela bilden
- 2016
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Ingår i: Uppsalainiativet.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Eftersom det finns fler växthusgaser än en, så behöver vi kunna göra relevanta jämförelser mellan utsläpp av olika sådana. Hur stort metanutsläpp orsakar lika mycket förhöjd växthuseffekt som en given mängd koldioxid? Frågan är mer komplicerad än man kanske först anar, och vi har idag glädjen att presentera ett gästinlägg om saken av Chalmersforskarna Christian Azar, David Bryngelsson, Daniel Johansson, Erik Sterner och Stefan Wirsenius. /O.H.
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| 6. |
- Bryngelsson, David, 1981, et al.
(författare)
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How Do Dietary Choices Influence the Energy-System Cost of Stabilizing the Climate?
- 2017
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Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 10:2
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Tidskriftsartikel (refereegranskat)abstract
- We investigate how different global dietary scenarios affect the constraints on, and costs of, transforming the energy system to reach a global temperature stabilization limit of 2 degrees C above the pre-industrial level. A global food and agriculture model, World Food Supply Model (WOFSUM), is used to create three dietary scenarios and to calculate the CH4 and N2O emissions resulting from their respective food-supply chains. The diets are: (i) a reference diet based on current trends; (ii) a diet with high (reference-level) meat consumption, but without ruminant products (i.e., no beef, lamb, or dairy, only pork and poultry); and (iii) a vegan diet. The estimated CH4 and N2O emissions from food production are fed into a coupled energy and climate-system optimization model to quantify the energy system implications of the different dietary scenarios, given a 2 degrees C target. The results indicate that a phase-out of ruminant products substantially increases the emission space for CO2 by about 250 GtC which reduces the necessary pace of the energy system transition and cuts the net present value energy-system mitigation costs by 25%, for staying below 2 degrees C. Importantly, the additional cost savings with a vegan diet--beyond those achieved with a phase-out of ruminant products--are marginal (only one additional percentage point). This means that a general reduction of meat consumption is a far less effective strategy for meeting the 2 degrees C target than a reduction of beef and dairy consumption.
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| 7. |
- Chadwick, D., et al.
(författare)
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Digital inclusion and participation of people with intellectual disabilities during COVID-19 : A rapid review and international bricolage
- 2022
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Ingår i: Journal of Policy and Practice in Intellectual Disabilities. - : Wiley. - 1741-1122 .- 1741-1130. ; 19:3, s. 242-256
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Tidskriftsartikel (refereegranskat)abstract
- The COVID-19 pandemic has meant a rapid transfer of everyday activities to the online world. Information and communication technologies (ICTs) have become more embedded than ever in people's lives. This investigation addresses how this change has affected the lives of people with intellectual disabilities (ID). A two-step design was used. A rapid review was conducted on empirical studies published between January 2019 and June 2021. Search terms related to ID, ICT use and COVID-19. A qualitative international bricolage was also conducted corresponding to author nationalities. Data gathered from the review and bricolage were analysed separately using thematic analysis and relationally synthesised. Digital solutions to provide access to COVID-19 information and guidance seemed inadequate but were seldom empirically studied. Digital poverty, literacy and exclusion remain significant issues for people with ID internationally. People and their carers experienced reduced and removed service provision, loneliness and impoverished daily lives during the pandemic; amelioration of which was facilitated by digital solutions. One solution often used was videoconferencing. Prior experience of digital participation, adequate finances, connection, support and digital literacy mentoring for both people with ID and those providing services and support facilitated digital inclusion. Digital exclusion during COVID-19 was exacerbated by sociopolitical, structural, individual and support-related barriers. Although awareness of digital exclusion appears to have been raised, the extent to which this has led to action and change remains unclear. Despite digital exclusion and digital participation benefitting continuation of life, social and emotional well-being and autonomy, COVID-19 has not provided the impetus to eradicate digital poverty for people with ID. Governmental support, digital education, creativity and problem solving are required to enable people with ID the human right to be included in the digital world at this essential time and into the future.
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| 8. |
- de Peppo, Giuseppe Maria, 1981, et al.
(författare)
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Osteogenic response of human mesenchymal stem cells to well-defined nanoscale topography in vitro
- 2014
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Ingår i: International journal of nanomedicine. - : Informa UK Limited. - 1176-9114 .- 1178-2013. ; 9:1, s. 2499-2515
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Tidskriftsartikel (refereegranskat)abstract
- Background: Patterning medical devices at the nanoscale level enables the manipulation of cell behavior and tissue regeneration, with topographic features recognized as playing a significant role in the osseointegration of implantable devices. Methods: In this study, we assessed the ability of titanium-coated hemisphere-like topographic nanostructures of different sizes (approximately 50, 100, and 200 nm) to influence the morphology, proliferation, and osteogenic differentiation of human mesenchymal stem cells (hMSCs). Results: We found that the proliferation and osteogenic differentiation of hMSCs was influenced by the size of the underlying structures, suggesting that size variations in topographic features at the nanoscale level, independently of chemistry, can be exploited to control hMSC behavior in a size-dependent fashion. Conclusion: Our studies demonstrate that colloidal lithography, in combination with coating technologies, can be exploited to investigate the cell response to well defined nanoscale topography and to develop next-generation surfaces that guide tissue regeneration and promote implant integration.
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| 9. |
- Fridell, Erik, 1963, et al.
(författare)
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Investigation of NOx storage catalysts
- 1997
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Ingår i: 4th International Congress on Catalysis and Automotive Pollution Control (CAPoC4) in Brussels, Belgium, April 9-11, 1997.
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Konferensbidrag (refereegranskat)
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| 10. |
- Fridell, Erik, 1963, et al.
(författare)
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Investigations of NOx storage catalysts
- 1998
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Ingår i: Studies in Surface Science and Catalysis. - 0167-2991. ; 116, s. 537-547
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Tidskriftsartikel (refereegranskat)abstract
- NOx storage catalysts are used to reduce nitrogen oxides from lean-burn vehicles. The nitrogen oxides are stored in the catalyst during lean conditions and subsequently released and reduced during short periods of rich conditions. In the present study, we systematically investigate the sequence of elementary steps in the NOx reduction cycle, and the extent to which these steps influence the maximum NOx, reduction potential of the catalyst. As a model system, we use barium oxide as the NOx, storing compound in a Pt/Rh/Al2O3 system. Kinetics of NO oxidation, NO and NO2 adsorption, NO and NO2 release and reduction are studied under controlled conditions with systematic variations of temperature, gas composition, and storing/release times. The transient experiments comprise a storing phase using a lean NO/C3H6/O2/N2 gas mixture, and a regenerating phase where the O2 now is turned off. Experimentally, a significant amount of NOx is found to be stored in the Ba-containing material. A maximum in NOx storage is observed around 380 degrees C. For most of the experiments, there are clear NO and NO2 desorption peaks upon switching from the storing to the regeneration phase. TPD studies of NO and NO2 reveal a significant difference between prereduced and pre-oxidised samples where the former produce predominantly N2 and N2O at around 200 degrees C while NO and O2 desorb from the latter around 500 degrees C. In situ FTIR spectra show nitrate peaks in the region 1300-1400 cm(-1) when NOx is stored under lean conditions.
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