| 1. |
- Abbaszad Rafi, Abdolrahim, et al.
(author)
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A facile route for concurrent fabrication and surface selective functionalization of cellulose nanofibers by lactic acid mediated catalysis
- 2023
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In: Scientific Reports. - : Springer Nature. - 2045-2322 .- 2045-2322. ; 13:1
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Journal article (peer-reviewed)abstract
- Celulose nanofibers are lightweight, recycable, biodegradable, and renewable. Hence, there is a great interest of using them instead of fossil-based components in new materials and biocomposites. In this study, we disclose an environmentally benign (green) one-step reaction approach to fabricate lactic acid ester functionalized cellulose nanofibrils from wood-derived pulp fibers in high yields. This was accomplished by converting wood-derived pulp fibers to nanofibrillated “cellulose lactate” under mild conditions using lactic acid as both the reaction media and catalyst. Thus, in parallel to the cellulose nanofibril production, concurrent lactic acid-catalyzed esterification of lactic acid to the cellulose nanofibers surface occured. The direct lactic acid esterification, which is a surface selective functionalization and reversible (de-attaching the ester groups by cleavage of the ester bonds), of the cellulose nanofibrils was confirmed by low numbers of degree of substitution, and FT-IR analyses. Thus, autocatalytic esterification and cellulose hydrolysis occurred without the need of metal based or a harsh mineral acid catalysts, which has disadvantages such as acid corrosiveness and high recovery cost of acid. Moreover, adding a mineral acid as a co-catalyst significantly decreased the yield of the nanocellulose. The lactic acid media is successfully recycled in multiple reaction cycles producing the corresponding nanocellulose fibers in high yields. The disclosed green cellulose nanofibril production route is industrial relevant and gives direct access to nanocellulose for use in variety of applications such as sustainable filaments, composites, packaging and strengthening of recycled fibers.
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| 2. |
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| 3. |
- Andersson, Erik, et al.
(author)
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Ambio fit for the 2020s
- 2022
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In: Ambio. - : Springer Nature. - 0044-7447 .- 1654-7209. ; 51:5, s. 1091-1093
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Journal article (peer-reviewed)
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| 4. |
- Andersson, Morgan, 1965, et al.
(author)
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New Swedish forensic psychiatric facilities: visions and outcomes.
- 2013
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In: Facilities. - : Emerald. - 0263-2772 .- 1758-7131. ; 31:1/2, s. 24-38
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Journal article (peer-reviewed)abstract
- Purpose – The purpose of this paper is to map significant features of the physical design of nine recently planned facilities for forensic psychiatric care in Sweden. The present paper is focused on differences in the physical design, static security adaptations, visions and goals for the projects, economy and steering processes. Design/methodology/approach – In June 2008, records concerning major forensic psychiatric construction projects, planned or carried out between 1970 and 2008, were requested from all 21 regions in Sweden. The documents were collected, organized, critically examined, and analyzed in their contexts. Extensive data have also been retrieved from the internet. Findings – In spite of the common national legislation governing forensic psychiatric care, the projects show great diversity in the physical design and, after 2006, increasing emphasis on static security. The collected material indicates different visions and goals and little coordination between them. It also suggests that the decisions rarely have been preceded by scientific studies or, as it appears, systematic needs assessments. There were also considerable variations in the interpretation of the legislation stipulating public access to official documentation and the time-frame allowed for such requests. Research limitations/implications – Limitations of the project especially relate to the incompleteness of the documents received. Originality/value – This mainly descriptive paper provides an overview of contemporary Swedish forensic psychiatric construction projects, planned for or realized after 2000. This paper points out structural and physical differences between these projects. The systematised documents are made available for research purposes within different disciplines.
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| 5. |
- Andric, Jelena, 1979, et al.
(author)
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A particle-level rigid fiber model for high-Reynolds number flow, implemented in a general-purpose CFD code
- 2013
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In: 8th International Conference on Multiphase Flow ICMF 2013, Korea.
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Conference paper (peer-reviewed)abstract
- A particle-level rigid fiber model has been integrated into a general-purpose, open source computational fluid dynamics code to carry out detailed studies of fiber–flow interactions in realistic flow fields. The fibers are modeled as chains of cylindrical segments, and their translational and rotational degrees of freedom are considered. The equations of motion contain the contributions from hydrodynamic forces and torques, and the segment inertia is taken into account. The model is validated for the rotational motion of isolated fibers in simple shear flow, and the computed period of rotation is in good agreement with the one computed using Jeffery’s equation for a prolate spheroid with an equivalent aspect ratio. The model is applied by suspending a number of fibers in the swirling flow of a conical diffuser, resembling one stage in the dry-forming of pulp mats. The Reynolds-averaged Navier–Stokes equations with an eddy-viscosity turbulence model are employed to describe the fluid motion, and a one-way coupling between the fibers and the fluid phase is included. The dependence of the fiber motion on initial position and density is analyzed.
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| 6. |
- Andric, Jelena, 1979, et al.
(author)
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A study of a flexible fiber model and its behavior in DNS of turbulent channel flow
- 2013
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In: Acta Mechanica. - : Springer Science and Business Media LLC. - 0001-5970 .- 1619-6937. ; 224:10, s. 2359-2374
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Journal article (peer-reviewed)abstract
- The dynamics of individual flexible fibers in a turbulent flow field have been analyzed, varying their initial position, density and length. A particlelevel fiber model has been integrated into a general-purpose, open source Computational Fluid Dynamics (CFD) code. The fibers are modeled as chains of cylindrical segments connected by ball and socket joints. The equations of motion of the fibers contain the inertia of the segments, the contributions from hydrodynamic forces and torques, and the connectivity forces at the joints. Direct Numerical Simulation (DNS) of the incompressible Navier–Stokes equations is used to describe the fluid flow in a plane channel and a one-way coupling is considered between the fibers and the fluid phase. We investigate the translational motion of fibers by considering the mean square displacement of their trajectories. We find that the fiber motion is primarily governed by velocity correlations of the flow fluctuations. In addition, we show that there is a clear tendency of the thread-like fibers to evolve into complex geometrical configurations in a turbulent flow field, in fashion similar to random conformations of polymer strands subjected to thermal fluctuations in a suspension. Finally, we show that fiber inertia has a significant impact on reorientation time-scales of fibers suspended in a turbulent flow field.
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| 7. |
- Andric, Jelena, 1979, et al.
(author)
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Ballistic deflection of fibres in decelerating flow
- 2016
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In: International Journal of Multiphase Flow. - : Elsevier BV. - 0301-9322 .- 1879-3533. ; 85, s. 57-66
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Journal article (peer-reviewed)abstract
- We investigate the motion of inertial, rod-like fibres in the decelerating flow of a wedge-shaped channel with non-creeping fibre-flow interactions. We consider the trajectories of isolated fibres to identify the conditions for which these trajectories deflect from the streamlines of the flow as well as a rectilinear path. We carry out analytical and numerical studies under the assumption of an infinite fibre hydrodynamic resistance to transverse flow, and we expand the numerical study by taking into account a finite transverse hydrodynamic resistance. The analytical analysis identifies a longitudinal ballistic number Bℓ and a transverse ballistic number Bt as two dimensionless parameters that govern the fibre dynamics. It is found that Bℓ is the product of the Stokes number Stℓ in the longitudinal direction of the fibre and the channel opening angle β. As anticipated, a fibre moves along the streamlines in the viscosity-dominated regime (Bℓ « 1, Bt « 1), while it moves in a straight line without being rotated in the inertia-dominated regime (Bt » 1). The focus of the present study is on the intermediate regime (Bℓ » 1, Bt
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| 8. |
- Andric, Jelena, 1979, et al.
(author)
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Particle-level simulations of flocculation in a fiber suspension flowing through a diffuser
- 2017
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In: Thermal Science. - : VINCA INST NUCLEAR SCI. - 0354-9836 .- 2334-7163. ; 21, s. S573-S583
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Journal article (peer-reviewed)abstract
- We investigate flocculation in dilute suspensions of rigid, straight fibers in a decelerating flow field of a diffuser. We carry out numerical studies using a particle-level simulation technique that takes into account the fiber inertia and the non-creeping fiber-flow interactions. The fluid flow is governed by the Reynolds-averaged Navier-Stokes equations with the standard k-omega eddy-viscosity turbulence model. A one-way coupling between the fibers and the flow is considered with a stochastic model for the fiber dispersion due to turbulence. The fibers interact through short-range attractive forces that cause them to aggregate into flocs when fiber-fiber collisions occur. We show that ballistic deflection of fibers greatly increases the flocculation in the diffuser. The inlet fiber kinematics and the fiber inertia are the main parameters that affect fiber flocculation in the pre-diffuser region.
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| 9. |
- Andric, Jelena, 1979, et al.
(author)
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Rheological properties of dilute suspensions of rigid and flexible fibers
- 2014
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In: Journal of Non-Newtonian Fluid Mechanics. - : Elsevier BV. - 0377-0257 .- 1873-2631. ; 212, s. 36-46
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Journal article (peer-reviewed)abstract
- Particle-level simulations are used to study the rheology of monodispersed suspensions of rigid and flexible fibers in a creeping, simple shear flow of a Newtonian fluid. We also investigate the influence of different equilibrium shapes (straight and curved) of the fibers on the behavior of the suspension. A parametric study of the impacts of fiber flexural rigidity and morphology on rheology quantifies the effects of these realistic fiber features on the experimentally accessible rheological properties. A fiber is modeled as a chain of rigid cylindrical segments, interacting through a two-way coupling with the fluid described by the incompressible three-dimensional Navier--Stokes equations. The initial fiber configuration is in the flow--gradient plane. We show that, when the shear rate is increased, straight flexible fibers undergo a buckling transition, leading to the development of finite first and second normal stress differences and a reduction of the viscosity. These effects, triggered by shape fluctuations, are dissimilar to the effects induced by the curvature of stiff, curved fibers, for which the viscosity increases with the curvature of the fiber. An analysis of the orbital drift of fibers initially oriented at an angle to the flow--gradient plane provides an estimate for the time-scale within which the prediction of the rheological behavior is valid. The information obtained in this work can be used in the experimental characterization of fiber morphology and mechanics through rheology.
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| 10. |
- Arvidsson, Rickard, 1984, et al.
(author)
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Assessing the Environmental Impacts of Palm Oil
- 2011
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In: Palm Oil: Nutrition, Uses and Impacts. - : Nova Science Publishers, Inc.. - 9781612099217 ; , s. 159-186
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Book chapter (other academic/artistic)abstract
- Palm oil is used for cooking in Southeast Asia and Africa and as a food additive in a number of processed foods world-wide. The production of palm oil is increasing, and it is of special interest from a nutritional point of view due to its high energy content and its significant content of micronutrients. In addition, palm oil is increasingly used to produce various biofuels. Due to large production volumes and diverse applications of palm oil, it is highly interesting and important to study the environmental impacts of its production. This chapter discusses how the environmental impacts of palm oil can be assessed, focusing on the life cycle environmental impacts of palm oil in comparison to similar products. A brief overview of life cycle assessment as a method is given, and results are presented together with suggestions for environmental improvements of palm oil cultivation and production. It is shown that the magnitude of the environmental impacts connected to palm oil in relation to other products is heavily affected by the choice of environmental indicators, which in LCA studies consist of both an environmental impact category and a so-called functional unit. Regarding impact categories, the global warming and acidification potentials of palm oil are lower than those of rapeseed oil per kg oil. The water footprint of palm oil and rapeseed oil are about the same on a mass basis, but for the two land use indicators soil erosion and heavy metal accumulation, rapeseed oil has a lower impact than palm oil. Specific interest is given to the life cycle energy use of palm oil in response to the unclear and diverse definitions of this impact category in different studies. It is concluded that there is a need to carefully define the energy use impact category when reporting on palm oil or similar products, and also to differentiate between different kinds of energy sources. If instead of mass the micronutrient content is applied as functional unit, palm oil still has lower global warming potential and acidification than rapeseed oil when compared on the basis of vitamin E content. However, if β-carotene content is used as functional unit, rapeseed oil is not relevant for comparison due to its negligible content of β-carotene. For that case, palm oil is therefore instead compared to tomatoes on a β-carotene basis, since tomatoes are rich in β-carotene. The tomatoes were shown to perform better then palm oil regarding global warming potential on a β-carotene basis. The effects of time and scale on the environmental impacts of palm oil, which includes changes in technical performance and electricity sources, are also discussed in this chapter. It is shown that combustion of the methane formed from the palm oil mill effluent can significantly reduce the global warming potential.
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