| 1. |
- Wågberg, Lars, et al.
(author)
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The build-up of polyelectrolyte multilayers of microfibrillated cellulose and cationic polyelectrolytes
- 2008
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In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 24:3, s. 784-795
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Journal article (peer-reviewed)abstract
- A new type of nanocellulosic material has been prepared by high-pressure homogenization of carboxymethylated cellulose fibers followed by ultrasonication and centrifugation. This material had a cylindrical cross-section as shown by transmission electron microscopy with a diameter of 5-15 nm and a length of up to 1 mu m. Calculations, using the Poisson-Boltzmann equation, showed that the surface potential was between 200 and 250 mV, depending on the pH, the salt concentration, and the size of the fibrils. They also showed that the carboxyl groups on the surface of the nanofibrils are not fully dissociated until the pH has reached pH = similar to 10 in deionized water. Calculations of the interaction between the fibrils using the Derjaguin-Landau-Verwey-Overbeek theory and assuming a cylindrical geometry indicated that there is a large electrostatic repulsion between these fibrils, provided the carboxyl groups are dissociated. If the pH is too low and/or the salt concentration is too high, there will be a large attraction between the fibrils, leading to a rapid aggregation of the fibrils. It is also possible to form polyelectrolyte multilayers (PEMs) by combining different types of polyelectrolytes and microfibrillated cellulose (MFC). In this study, silicon oxide surfaces were first treated with cationic polyelectrolytes before the surfaces were exposed to MFC. The build-up of the layers was monitored with ellipsometry, and they show that it is possible to form very well-defined layers by combinations of MFC and different types of polyelectrolytes and different ionic strengths of the solutions during the adsorption of the polyelectrolyte. A polyelectrolyte with a three-dimensional structure leads to the build-up of thick layers of MFC, whereas the use of a highly charged linear polyelectrolyte leads to the formation of thinner layers of MFC. An increase in the salt concentration during the adsorption of the polyelectrolyte results in the formation of thicker layers of MFC, indicating that the structure of the adsorbed polyelectrolyte has a large influence on the formation of the MFC layer. The films of polyelectrolytes and MFC were so smooth and well-defined that they showed clearly different interference colors, depending on the film thickness. A comparison between the thickness of the films, as measured with ellipsometry, and the thickness estimated from their colors showed good agreement, assuming that the films consisted mainly of solid cellulose with a refractive index of 1.53. Carboxymethylated MFC is thus a new type of nanomaterial that can be combined with oppositely charged polyelectrolytes to form well-defined layers that may be used to form, for example, new types of sensor materials.
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| 2. |
- Ekener, Elisabeth, 1963-, et al.
(author)
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Developing Life Cycle Sustainability Assessment methodology by applying values-based sustainability weighting - Tested on biomass based and fossil transportation fuels
- 2018
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In: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526 .- 1879-1786. ; 181, s. 337-351
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Journal article (peer-reviewed)abstract
- The production and use of transportation fuels can lead to sustainability impacts. Assessing them simultaneously in a holistic way is a challenge. This paper examines methodology for assessing the sustainability performance of products in a more integrated way, including a broad range of social impacts. Life Cycle Sustainability Assessment (LCSA) methodology is applied for this assessment. LSCA often constitutes of the integration of results from social LCA (S-LCA), environmental life cycle assessment (E-LCA) and life cycle costing (LCC). In this study, an S-LCA from an earlier project is extended with a positive social aspect, as well as refined and detailed. E-LCA and LCC results are built from LCA database and literature. Multi Criteria Decision Analysis (MCDA) methodology is applied to integrate the results from the three different assessments into an LCSA. The weighting of key sustainability dimensions in the MCDA is performed in different ways, where the sustainability dimensions are prioritized differently priority based on the assumed values of different stakeholder profiles (Egalitarian, Hierarchist, and Individualist). The developed methodology is tested on selected biomass based and fossil transportation fuels - ethanol produced from Brazilian sugarcane and US corn/maize, and petrol produced from Russian and Nigerian crude oils, where it delineates differences in sustainability performance between products assessed. The outcome in terms of relative ranking of the transportation fuel chains based on sustain ability performance differs when applying different decision-maker profiles. This result highlights and supports views that there is no one single answer regarding which of the alternatives that is most sustainable. Rather, it depends strongly upon the worldview and values held by the decision maker. A key conclusion is that sustainability assessments should pay more attention to potential differences in underlying values held by key stakeholders in relevant societal contexts. The LCSA methodology still faces challenges regarding results integration but MCDA in combination with stakeholder profiles appears to be a useful approach to build on further.
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| 3. |
- Åkerman, Jonas, et al.
(author)
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Low-carbon scenarios for long-distance travel 2060
- 2021
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In: Transportation Research Part D: Transport and Environment. - : Elsevier BV. - 1361-9209 .- 1879-2340. ; 99
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Journal article (peer-reviewed)abstract
- In many industrialised countries, the climate impact from long-distance travel is greater than that from short-distance travel. In this paper, we present five scenarios for long-distance travel in 2060, which are consistent with a 67% probability of limiting global warming to 1.8 degrees. The scenarios concern travel by the Swedish population, but per capita travel volume and fuel use could be generalised globally. A key result is that all scenarios require reductions in Swedish per capita air travel in the range of 38–59% compared to 2017. The direct effect on air travel of implementing a high-speed rail network in Sweden and Northern Europe was found to be modest. A higher emission reduction could be achieved if mixed mode trips comprising rail and air legs were more widely adopted. Finally, the pros and cons of future aviation fuels are discussed, the main candidates being biofuel, electrofuel, and liquid hydrogen.
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| 4. |
- Eriksson, Henrik, 1973, et al.
(author)
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Exploring Quality Challenges and the Validity of Excellence Models
- 2016
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In: International Journal of Operations & Production Management. - 0144-3577 .- 1758-6593. ; 36:10, s. 1201-1221
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Journal article (peer-reviewed)abstract
- Purpose: The purpose is to identify and explore important quality-related challenges facing organizations, and how current excellence models incorporate these challenges.Methodology: The article is based on a Delphi study in Swedish organizations, 49 challenges were generated and ranked according to importance. The top 10 ranked challenges were compared to the principles of four excellence models.Findings: The excellence models seem to still be relevant since their content matches many of the challenges identified. The MBNQA and the SIQ models were found to have the most comprehensive coverage, while the ISO model had limited coverage.Research Limitations/Implications: Three areas for further research were identified: 1) how QM can evolve in different contexts with varying needs in terms of adaptive and explorative capabilities, 2) the interfaces of QM and sustainability, and ways to understand how customers and stakeholders can be active contributors to improvements and 3) the roles of the owners and board of directors in QM, and how to organize and distribute responsibilities of the QM work.Practical and Social Implications: Three important challenges could be addressed in upcoming revisions of excellence models: 1) making QM a strategic issue for company owners; 2) involving customers in the improvement activities; and 3) developing processes that are robust, while still easily adaptable.Originality/Value: The Delphi study has identified upcoming challenges in the QM area based on input from 188 quality professionals.
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| 5. |
- Kulachenko, Artem, et al.
(author)
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Reinventing mechanics of fibre network
- 2008
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In: Progress in Paper Physics Seminar. - Helsinki : Helsinki University Press. ; , s. 185-193
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Conference paper (other academic/artistic)
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| 6. |
- Rahman, Hafizur, et al.
(author)
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The effect of increased pulp yield using additives in the softwood kraft cook on the physical properties of low-grammage handsheets
- 2017
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In: Nordic Pulp & Paper Research Journal. - : AB SVENSK PAPPERSTIDNING. - 0283-2631 .- 2000-0669. ; 32:3, s. 317-323
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Journal article (peer-reviewed)abstract
- The effect of increasing the pulp yield by the addition of sodium borohydride (NaBH4) or polysulfide (PS) in softwood kraft cooking, i.e. enhancing the retention of glucomannan, on the physical properties of low-grammage handsheets was studied. In addition to the yield improvement, an increase in tensile index was observed, especially at lower degrees of beating. These higher yield pulps showed an increase in pore volume, indicating an increased degree of swelling of the fibres. Presumably, the increased flexibility of the fibres affects the bonding strength and leads to the higher tensile index observed.
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| 7. |
- Zhao, Yadong, et al.
(author)
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Cellulose Nanofibers from Softwood, Hardwood, and Tunicate : Preparation-Structure-Film Performance Interrelation
- 2017
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In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:15, s. 13508-13519
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Journal article (peer-reviewed)abstract
- This work reveals the structural variations of cellulose nanofibers (CNF) prepared from different cellulose sources, including softwood (Picea abies), hardwood (Eucalyptus grandis × E. urophylla), and tunicate (Ciona intestinalis), using different preparation processes and their correlations to the formation and performance of the films prepared from the CNF. Here, the CNF are prepared from wood chemical pulps and tunicate isolated cellulose by an identical homogenization treatment subsequent to either an enzymatic hydrolysis or a 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation. They show a large structural diversity in terms of chemical, morphological, and crystalline structure. Among others, the tunicate CNF consist of purer cellulose and have a degree of polymerization higher than that of wood CNF. Introduction of surface charges via the TEMPO-mediated oxidation is found to have significant impacts on the structure, morphology, optical, mechanical, thermal, and hydrophobic properties of the prepared films. For example, the film density is closely related to the charge density of the used CNF, and the tensile stress of the films is correlated to the crystallinity index of the CNF. In turn, the CNF structure is determined by the cellulose sources and the preparation processes. This study provides useful information and knowledge for understanding the importance of the raw material for the quality of CNF for various types of applications.
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| 8. |
- Dima, Elijs, et al.
(author)
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View position impact on QoE in an immersive telepresence system for remote operation
- 2019
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In: 2019 11th International Conference on Quality of Multimedia Experience, QoMEX 2019. - Berlin, Germany : Institute of Electrical and Electronics Engineers Inc.. - 9781538682128
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Conference paper (peer-reviewed)abstract
- In this paper, we investigate how different viewing positions affect a user's Quality of Experience (QoE) and performance in an immersive telepresence system. A QoE experiment has been conducted with 27 participants to assess the general subjective experience and the performance of remotely operating a toy excavator. Two view positions have been tested, an overhead and a ground-level view, respectively, which encourage reliance on stereoscopic depth cues to different extents for accurate operation. Results demonstrate a significant difference between ground and overhead views: the ground view increased the perceived difficulty of the task, whereas the overhead view increased the perceived accomplishment as well as the objective performance of the task. The perceived helpfulness of the overhead view was also significant according to the participants.
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| 9. |
- Hajian, Alireza, et al.
(author)
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Understanding the Dispersive Action of Nanocellulose for Carbon Nanomaterials
- 2017
-
In: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 17:3, s. 1439-1447
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Journal article (peer-reviewed)abstract
- This work aims at understanding the excellent ability of nanocelluloses to disperse carbon nanomaterials (CNs) in aqueous media to form long-term stable colloidal dispersions without the need for chemical functionalization of the CNs or the use of surfactant. These dispersions are useful for composites with high CN content when seeking water-based, efficient, and green pathways for their preparation. To establish a comprehensive understanding of such dispersion mechanism, colloidal characterization of the dispersions has been combined with surface adhesion measurements using colloidal probe atomic force microscopy (AFM) in aqueous media. AFM results based on model surfaces of graphene and nanocellulose further suggest that there is an association between the nanocellulose and the CN. This association is caused by fluctuations of the counterions on the surface of the nanocellulose inducing dipoles in the sp2carbon lattice surface of the CNs. Furthermore, the charges on the nanocellulose will induce an electrostatic stabilization of the nanocellulose–CN complexes that prevents aggregation. On the basis of this understanding, nanocelluloses with high surface charge density were used to disperse and stabilize carbon nanotubes (CNTs) and reduced graphene oxide particles in water, so that further increases in the dispersion limit of CNTs could be obtained. The dispersion limit reached the value of 75 wt % CNTs and resulted in high electrical conductivity (515 S/cm) and high modulus (14 GPa) of the CNT composite nanopapers.
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| 10. |
- Mahmood, Aamir, 1980-, et al.
(author)
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Energy-Reliability Aware Link Optimization for Battery-Powered IoT Devices With Nonideal Power Amplifiers
- 2019
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In: IEEE Internet of Things Journal. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2327-4662. ; 6:3, s. 5058-5067
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Journal article (peer-reviewed)abstract
- In this paper, we study cross-layer optimization of low-power wireless links for reliability-aware applications while considering both the constraints and the nonideal characteristics of the hardware in Internet-of-Things (IoT) devices. Specifically, we define an energy consumption (EC) model that captures the energy cost-of transceiver circuitry, power amplifier (PA), packet error statistics, packet overhead, etc.-in delivering a useful data bit. We derive the EC models for an ideal and two realistic nonlinear PA models. To incorporate packet error statistics, we develop a simple, in the form of elementary functions, and accurate closed-form packet error rate approximation in Rayleigh block-fading. Using the EC models, we derive energy-optimal yet reliability and hardware compliant conditions for limiting unconstrained optimal signal-to-noise ratio (SNR), and payload size. Together with these conditions, we develop a semianalytic algorithm for resource-constrained IoT devices to jointly optimize parameters on physical (modulation size, SNR) and medium access control (payload size and the number of retransmissions) layers in relation to link distance. Our results show that despite reliability constraints, the common notion-higherorder M-ary modulations are energy optimal for short-range communication-prevails, and can provide up to 180% lifetime extension as compared to often used OQPSK modulation in IoT devices. However, the reliability constraints reduce both their range and the energy efficiency, while nonideal traditional PA reduces the range further by 50% and diminishes the energy gains unless a better PA is used.
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