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- Jakobsson, Fredrik Lars Emil, 1974-
(författare)
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Charge transport modulation in organic electronic diodes
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Since the discovery of conducting polymers three decades ago the field of organic electronics has evolved rapidly. Organic light emitting diodes have already reached the consumer market, while organic solar cells and transistors are rapidly maturing. One of the great benefits with this class of materials is that they can be processed from solution. This enables several very cheap production methods, such as printing and spin coating, and opens up the possibility to use unconventional substrates, such as flexible plastic foils and paper. Another great benefit is the possibility of tailoring the molecules through carefully controlled synthesis, resulting in a multitude of different functionalities.This thesis reports how charge transport can be altered in solid-state organic electronic devices, with specific focus on memory applications. The first six chapters give a brief review of the field of solid-state organic electronics, with focus on electronic properties, resistance switch mechanisms and systems. Paper 1 and 3 treat Rose Bengal switch devices in detail – how to improve these devices for use in cross-point arrays as well as the origin of the switch effect. Paper 2 investigates how the work function of a conducting polymer can be modified to allow for better electron injection into an organic light emitting diode. The aim of the work in papers 4 and 5 is to understand the behavior of switchable charge trap devices based on blends of photochromic molecules and organic semiconductors. With this in mind, charge transport in the presence of traps is investigated in paper 4 and photochromic molecules is investigated using quantum chemical methods in paper 5.
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| 2. |
- Scarpa, Simone, 1976-
(författare)
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The local welfare system as a scale question
- 2016
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Ingår i: <em>Combating poverty in local welfare systems – active inclusion strategies in European cities</em>. - Basingstoke : Palgrave Macmillan. - 9781137531902 ; , s. 29-51
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Bokkapitel (refereegranskat)
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| 3. |
- Ye, Pengcheng
(författare)
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Zeolite Membrane Separation at Low Temperature
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The energy consumption of separation process accounts for a large part inchemical industry. Membrane processes use much less energy compared to thecurrently used thermally driven processes and could thereby reduce energyconsumption in industry significantly. Zeolite membranes have severalsuperiorities over the commercially available polymeric membranes, e.g. higherflux, higher chemical and thermal stability. There have been extensive studieson zeolite membrane separation at high temperature during the past decades,whereas scientific reports at low temperature are rather scarce. It is of interest toexplore the performance under this condition.Zeolite membranes were for the first time evaluated for gas separation atcryogenic temperature in the present work. Air separation by ultra-thin MFImembranes was carried out with a feed pressure varying from 100 mbar to 5 barover the temperature range of 62– 110 K. The membranes were found to beoxygen selective at all the conditions investigated. The observed results werewell above the upper bound in the 2008 Robeson selectivity-permeability plotwhen the feed pressure was not higher than 1 bar. The O2/N2 separation factorreached 5.0, corresponding membrane selectivity 6.3 at 67 K and a feed pressureof 100 mbar, with a high O2 permeance of 8.6 × 10-7 mol m-2 s-1 Pa-1. Theperformance of our membrane (in terms of selectivity and permeability in Barrer)was comparable to that recently reported in Science by Carta et al., but 100times higher in term of permeance or flux.The selectivity to O2 should primarily emanate from condensation of O2 in thezeolite pores blocking the transport of N2. In addition, the O2/N2 selectivityincreased with decreasing feed pressure. Thus, the selectivity should also beenhanced by a weaker adsorption of N2 at the relatively lower feed pressures.The present work has therefore indicated the optimum conditions for airseparation using MFI membranes, namely low feed pressures and cryogenictemperatures.Synthesis gas generated from biomass or waste is a renewable energy resource,mainly consisting of CO, CO2, H2 and H2O. It is necessary to remove some CO2from the synthesis gas to arrive at optimum composition of the gas for e.g.methanol synthesis. In this work, zeolite membranes were also studied for CO2separation from H2 and CO at low temperatures down to 238 K with a feedpressure of 9 bar. The highest separation factor was 109 for CO2/H2 separationat 238 K and 21 for CO2/CO separation at 258 K, significantly higher than thatat room temperature. This is attractive for practical CO2 separation.In summary, the present work has demonstrated the potential of MFI zeolitemembranes for O2/N2 separation and CO2 separation from synthesis gas at lowtemperature.
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| 4. |
- Graf, Heike
(författare)
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Schlager i öst och väst
- 2002
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Ingår i: Hello Europe! Tallinn calling!. - Huddinge : Medie- och kommunikationsvetenskap. ; , s. 23-32
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 5. |
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| 6. |
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Övervakning av bokdominerade naturreservat: extensiv övervakning av skogsbiotopers innehåll med inriktning mot biologisk mångfald
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Inventeringen utfördes i 3 bokskogsdominerade områden, Jättaberget, Bökeskogen och Bjurkär, vid tidpunkten redan skyddade områden på väg att skyddas. Alla är i dag naturreservat. Syftet med undersökningen var att beskriva skosbiotopernas innehåll, speciellt med avseende på träd- och vedstrukturer. Dessutom ingick en noggrann inventering av indikatorarter (troligtvis endast mossor, lavar och storsvamp).Uppgifterna som framtogs vid inventeringen fördes in i databasen "Extensiv övervakning av skogsbiotoper"De funna indikatorarterna, varav en del rödlistade, finns angivna i en tabell i rapporten på sidan 19.
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| 7. |
- Albernaz, Daniel L., et al.
(författare)
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Droplet deformation and heat transfer in isotropic turbulence
- 2017
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Ingår i: Journal of Fluid Mechanics. - : Cambridge University Press. - 0022-1120 .- 1469-7645. ; 820, s. 61-85
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Tidskriftsartikel (refereegranskat)abstract
- The heat and mass transfer of deformable droplets in turbulent flows is crucial. to a wide range of applications, such as cloud dynamics and internal combustion engines. This study investigates a single droplet undergoing phase change in isotropic turbulence using numerical simulations with a hybrid lattice Boltzmann scheme. Phase separation is controlled by a non-ideal equation of state and density contrast is taken into consideration. Droplet deformation is caused by pressure and shear stress at the droplet interface. The statistics of thermodynamic variables are quantified and averaged over both the liquid and vapour phases. The occurrence of evaporation and condensation is correlated to temperature fluctuations, surface tension variation and turbulence intensity. The temporal spectra of droplet deformations are analysed and related to the droplet surface area. Different modes of oscillation are clearly identified from the deformation power spectrum for low Taylor Reynolds number Re, whereas nonlinearities are produced with the increase of Re A, as intermediate frequencies are seen to overlap. As an outcome, a continuous spectrum is observed, which shows a decrease in the power spectrum that scales as similar to f(-3) Correlations between the droplet Weber number, deformation parameter, fluctuations of the droplet volume and thermodynamic variables are also developed.
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| 8. |
- Cornebise, Julien, et al.
(författare)
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Adaptive sequential Monte Carlo by means of mixture of experts
- 2014
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Ingår i: Statistics and Computing. - : Springer Science and Business Media LLC. - 0960-3174 .- 1573-1375. ; 24:3, s. 317-337
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Tidskriftsartikel (refereegranskat)abstract
- Appropriately designing the proposal kernel of particle filters is an issue of significant importance, since a bad choice may lead to deterioration of the particle sample and, consequently, waste of computational power. In this paper we introduce a novel algorithm adaptively approximating the so-called optimal proposal kernel by a mixture of integrated curved exponential distributions with logistic weights. This family of distributions, referred to as mixtures of experts, is broad enough to be used in the presence of multi-modality or strongly skewed distributions. The mixtures are fitted, via online-EM methods, to the optimal kernel through minimisation of the Kullback-Leibler divergence between the auxiliary target and instrumental distributions of the particle filter. At each iteration of the particle filter, the algorithm is required to solve only a single optimisation problem for the whole particle sample, yielding an algorithm with only linear complexity. In addition, we illustrate in a simulation study how the method can be successfully applied to optimal filtering in nonlinear state-space models.
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