| 1. |
- Berggren, Magnus, et al.
(författare)
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Controlling inter-chain and intra-chain excitations of a poly(thiophene) derivative in thin films
- 1999
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Ingår i: Chemical Physics Letters. - : Elsevier. - 0009-2614 .- 1873-4448. ; 304:1-2, s. 84-90
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Tidskriftsartikel (refereegranskat)abstract
- The decay of photoexcitations in polythiophene chains has been studied in solid solutions of the polymer from room temperature to 4 K. A strong blue shift of the emission spectrum is observed in the polymer blend, as compared to the homopolymer. Dispersion of the polythiophene suppresses the non-radiative processes, which are suggested to be correlated to close contacts of polymer chains. Quantum chemistry modeling of the excited state distributed on two chains corroborate this conclusion.
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| 2. |
- Berggren, Magnus, et al.
(författare)
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Ultraviolet electroluminescence from an organic light emitting diode
- 1995
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Ingår i: Advanced Materials. - : Wiley-VCH Verlag Berlin. - 0935-9648 .- 1521-4095. ; 7:11, s. 900-903
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Tidskriftsartikel (refereegranskat)abstract
- The extension of the emission region for organic LEDs into the ultraviolet region is reported. Emission at 394 nm is achieved by modifying the geometry of a device based on poly(octylphenyl)bithiophene (PTOPT) and poly(octylphenyl)oxadiazole (PBD) which had previously been shown to emit white light. Through changing the geometry the red and green emission peaks have been suppressed and the UV band (from the PBD) enhanced.
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| 3. |
- Granlund, Thomas, et al.
(författare)
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A polythiophene microcavity laser
- 1998
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Ingår i: Chemical Physics Letters. - : Elsevier. - 0009-2614 .- 1873-4448. ; 288:5-6, s. 879-884
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Tidskriftsartikel (refereegranskat)abstract
- We report photopumped lasing in a microcavity device with a polythiophene layer as the emitter. These microcavity devices are built by joining two polymer coated dielectric mirrors at elevated temperature. When photopumping the film, a lasing threshold is observed at 120 nJ/cm(2). Comparative studies with fast pump-probe spectroscopy of thin polythiophene films and the same polymer in photopumped lasing studies, indicate that the gain coefficient is 80 +/- 20 cm(-1), and that the exciton concentration is 2 X 10(17) cm(-3) at the lasing transition, well below the exciton-exciton recombination level. (C) 1998 Elsevier Science B.V. All rights reserved.
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| 4. |
- Granlund, Thomas, et al.
(författare)
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Lasing in substituted polythiophene between dielectric mirrors
- 1999
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Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 102:1-3, s. 1038-1041
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Tidskriftsartikel (refereegranskat)abstract
- We report photopumped lasing in a microcavity device with a polythiophene layer as emitter. The microcavity is made of a polymer film between two dielectric Bragg reflecting mirrors (DBR). The:microcavity devices is built by joining two polymer coated DBR mirrors at elevated temperature. When photopumping the film,a lasing threshold is observed at 120 nJ/cm(2). Comparative studies with fast pump-probe spectroscopy of thin polythiophene films, and the same polymer in photopumped lasing studies, indicate that the gain coefficient is 80 +/- 20 cm(2) and that the exciton concentration is 2X10(17) cm(2) at the lasing transition, well below the exciton-exciton recombination level.
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| 5. |
- Granström, Magnus, et al.
(författare)
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Micrometer- and Nanometer-Sized Polymeric Light-Emitting Diodes
- 1995
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Ingår i: Science. - : American Association for the Advancement of Science. - 0036-8075 .- 1095-9203. ; 267:5203, s. 1479-1481
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Tidskriftsartikel (refereegranskat)abstract
- A method for the fabrication of micrometer- and submicrometer-sized polymeric light-emitting diodes is presented. Such diodes have a variety of applications. Light sources of dimensions around 100 nanometers are required for subwavelength, near-field optical microscopy. Another possible application is patterning on the micrometer and nanometer scale. The diodes have been made in the form of a sandwich structure, with the conductive polymer poly(3,4-ethylene-dioxythiophene) polymerized in the pores of commercially available microfiltration membranes defining the hole-injecting contacts, poly[3-(4-octylphenyl)-2,2-bithiophene] as the light-omitting layer, and a thin film of calcium-aluminum as the electron injector.
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| 6. |
- Granström, Magnus, et al.
(författare)
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Phase separation of conjugated polymers - Tools for new functions in polymer LEDs
- 1997
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Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 85:1-3, s. 1193-1194
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Tidskriftsartikel (refereegranskat)abstract
- Within the single family of substituted poly(thiophenes) it is possible to realize such diverse device designs as voltage controlled colours from polymer LEDs, sub-micron size LEDs, and white light emitters. Many of these features become possible by the use of polymer blends in which one or more poly(thiophenes) are mixed with a matrix polymer (PMMA). The phase structure in these blends can be controlled by stoichiometry and mode of formation. That phase structure can be used to prevent exciton transfer, and to define new colours in polymer LEDs. It also allows us to make anisotropic conductors suitable for contacting optical devices.
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| 7. |
- Granström, Magnus, et al.
(författare)
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Polymeric light-emitting diodes of submicron size - Structures and developments
- 1996
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Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 76:1-3, s. 141-143
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Tidskriftsartikel (refereegranskat)abstract
- Micron- and submicron-sized light-emitting diodes (LEDs) made using conjugated polymers as electroluminescent layers and contact materials are presented. Two different routes to make arrays of such small light sources have been developed. The benefits and drawbacks of the use of the conjugated polymer poly(2,3-ethylene-dioxythiophene) (PEDOT) as hole injector in polymer LEDs are also discussed.
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| 8. |
- Granström, Magnus, et al.
(författare)
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Self organizing polymer films - a route to novel electronic devices based on conjugated polymers
- 1997
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Ingår i: Supramolecular science. - : ELSEVIER SCI LTD. - 0968-5677 .- 1873-4146. ; 4:1-2, s. 27-34
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Tidskriftsartikel (refereegranskat)abstract
- Polymer blends are often used in polymer light emitting diodes as a tool to increase the efficiency of the devices. In this report, we show the necessity to take the phase separation properties of such blends into account, as the miscibility of the involved polymers drastically affects the resulting film structure. By using phase separated polymer blends involving conjugated poly(thiophenes) and different nonconjugated polymers as matrices, different types of applications, such as light emitting diodes with improved voltage control of emitted colour, sub-micron size LEDs and anisotropic conductors are demonstrated. (C) 1997 Elsevier Science Ltd. All rights reserved.
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| 9. |
- Inganäs, Olle, et al.
(författare)
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Thiophene polymers in light emitting diodes : Making multicolour devices
- 1995
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Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 71:1-3, s. 2121-2124
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Tidskriftsartikel (refereegranskat)abstract
- We can control the bandgap of thiophene polymers over 2 eV by choosing the nature, position and regularity of side chain substitutions. Electroluminescence from these polymers cover the full visible spectrum, from the blue into the near infra-red. Blends of these polymer materials allow us to construct voltage controlled variable colour light sources. A newly developed transfer technique allow us to mount thin oriented films of the polymers in polymer LEDs to obtain polarised light sources giving polarisation anisotropys of up to 3. Sub-lambda light sources have been constructed from these polymer materials using nanometer polymer electrodes.
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| 10. |
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| 11. |
- Agelfors, Eva, et al.
(författare)
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Synthetic visual speech driven from auditory speech
- 1999
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Ingår i: Proceedings of Audio-Visual Speech Processing (AVSP'99)).
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Konferensbidrag (refereegranskat)abstract
- We have developed two different methods for using auditory, telephone speech to drive the movements of a synthetic face. In the first method, Hidden Markov Models (HMMs) were trained on a phonetically transcribed telephone speech database. The output of the HMMs was then fed into a rulebased visual speech synthesizer as a string of phonemes together with time labels. In the second method, Artificial Neural Networks (ANNs) were trained on the same database to map acoustic parameters directly to facial control parameters. These target parameter trajectories were generated by using phoneme strings from a database as input to the visual speech synthesis The two methods were evaluated through audiovisual intelligibility tests with ten hearing impaired persons, and compared to “ideal” articulations (where no recognition was involved), a natural face, and to the intelligibility of the audio alone. It was found that the HMM method performs considerably better than the audio alone condition (54% and 34% keywords correct respectively), but not as well as the “ideal” articulating artificial face (64%). The intelligibility for the ANN method was 34% keywords correct.
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| 12. |
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| 13. |
- Berghel, Jonas, 1966-, et al.
(författare)
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From sawdust to pellets. Still a challenge...
- 2012
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Ingår i: Public Service Review European Union. - : European union. ; :33, s. 398-399
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 14. |
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| 15. |
- Berghel, Jonas, 1966-, et al.
(författare)
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Lösningarna finns! Är pelletsproducenterna medvetna om problemen?
- 2011
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Ingår i: Bioenergi. - Gävle : Region Gävleborg. - 9789163391262 ; , s. 25-29
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Sverige är inte längre världsledande som pelletsproducent. USA producerar allra mest pellets i världen. Kanada och Ryssland producerar också allt mer pellets. Ingen av dessa länder har någon omfattande inhemsk konsumtion. I stort sett all pellets exporteras och det sker huvudsakligen till Europa. Sannolikt kommer det att leda till att priset på pellets i Europa sjunker, med följd att lönsamheten för svenska pelletsproducenter minskar.
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| 16. |
- Berghel, Jonas, 1966-, et al.
(författare)
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The effects of kraft lignin additives on wood fuel pellet quality, energy use and shelf life
- 2013
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Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 112:0, s. 64-69
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Tidskriftsartikel (refereegranskat)abstract
- In 2011, the total consumption of pellets in Sweden amounted to 1.9 million tons, which represents an energy value of 9 TWh. The pellets are used in large-scale as well as in small-scale applications, and increased demands on pellet quality are likely to force pellet producers to improve on the pellet properties. One way of increasing pellet quality is by using additives. The purpose of this article, therefore, is to examine kraft lignin as an additive. Pelletswere produced in a small industrial pellet press located at KarlstadUniversity, Karlstad, Sweden, and 1–4% of kraft lignin was added to the pellets. The results indicate that the addition of an increased amount of kraft lignin to the pellets increases their mechanical durability and their lengths. The results also indicate that dry kraft lignin yields pellets with higher durability as compared to wet kraft lignin. The energy demand was unaffected by the increased use of kraft lignin. The general results presented in this paper are useful for producers of lignin, pellet producers and end-users of pellets, who are interested in developing their products and/or improving the production processes.
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| 17. |
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| 18. |
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| 19. |
- Beskow, Jonas, et al.
(författare)
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Expressive animated agents for affective dialogue systems
- 2004
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Ingår i: AFFECTIVE DIALOGUE SYSTEMS, PROCEEDINGS. - BERLIN : SPRINGER. - 3540221433 ; , s. 240-243
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Konferensbidrag (refereegranskat)abstract
- We present our current state of development regarding animated agents applicable to affective dialogue systems. A new set of tools are under development to support the creation of animated characters compatible with the MPEG-4 facial animation standard. Furthermore, we have collected a multimodal expressive speech database including video, audio and 3D point motion registration. One of the objectives of collecting the database is to examine how emotional expression influences articulatory patterns, to be able to model this in our agents. Analysis of the 3D data shows for example that variation in mouth width due to expression greatly exceeds that due to vowel quality.
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| 20. |
- Beskow, Jonas, et al.
(författare)
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The Swedish PFs-Star Multimodal Corpora
- 2004
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Ingår i: Proceedings of LREC Workshop on Models of Human Behaviour for the Specification and Evaluation of Multimodal Input and Output Interfaces. ; , s. 34-37
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Konferensbidrag (refereegranskat)abstract
- The aim of this paper is to present the multimodal speech corpora collected at KTH, in the framework of the European project PF-Star, and discuss some of the issues related to the analysis and implementation of human communicative and emotional visual correlates of speech in synthetic conversational agents. Two multimodal speech corpora have been collected by means of an opto-electronic system, which allows capturing the dynamics of emotional facial expressions with very high precision. The data has been evaluated through a classification test and the results show promising identification rates for the different acted emotions. These multimodal speech corpora will truly represent a valuable source to get more knowledge about how speech articulation and communicative gestures are affected by the expression of emotions.
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| 21. |
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| 22. |
- Frodeson, Stefan, Universitetsadjunkt, 1968-, et al.
(författare)
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The Potential for a Pellet Plant to Become a Biorefinery
- 2019
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Ingår i: Processes. - Basel : MDPI. - 2227-9717. ; 7:4, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- The use of bioenergy has increased globally in recent years, as has the utilization of biomaterials for various new product solutions through various biorefinery concepts. In this study, we introduce the concept of using a mechanical dewatering press in combination with thermal drying in a pellet plant. The purpose of the study is to increase the understanding of the effects a mechanical dewatering press has in a pellet production chain and investigate whether a pellet plant could thus become a biorefinery. The evaluations in this study are based on industrial data and initial tests at the university. The results show that the concept of using the mechanical dewatering press together with a packed moving bed dryer reduces energy use by 50%, compared to using only a packed moving bed dryer. The press water could be used as a raw material for biogas, bioplastics, and biohydrogen. Hence, this study points out the possibilities of a pellet plant increasing the efficiency of the drying step, while moving towards becoming a biorefinery.
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| 23. |
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| 24. |
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| 25. |
- Gustafsson, Lena, et al.
(författare)
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Rapid ecological response and intensified knowledge accumulation following a north European mega-fire
- 2019
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 34:4, s. 234-253
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Forskningsöversikt (refereegranskat)abstract
- Deepened knowledge on response of biota and ecological processes following fire is essential for a future with warmer climate and more disturbances. In 2014 the first mega-fire (13,100 ha) for at least a century in Scandinavia hit south-central Sweden, in a production forest landscape shaped by clearcutting forestry. Ecological dynamics is followed in >20 projects from universities, authorities and citizen science initiatives, rapidly accumulating substantial amounts of data. We outline projects and summarize their results during the first four years, demonstrating a rapid succession of fungi, lichens, vascular plants, birds, mammals, ticks, butterflies, beetles, and drastically altered carbon dynamics. We characterize forest operations including regeneration measures and point to patterns in pest and pathogen infestations. 8,000 ha is set aside for natural succession, with the rest harvested and managed for forest production, offering excellent opportunities for studies on salvage logging effects, already evident for birds. We demonstrate a strong regrowth of deciduous trees, and the protected part will in some decades likely develop into the largest deciduous-dominated area in boreal north Europe outside Russia. Continued studies of biodiversity and ecological processes are urgent for this unique area.
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