| 1. |
- Bazooyar, Faranak, 1972, et al.
(författare)
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Computational studies of water and carbon dioxide interactions with cellobiose
- 2015
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Ingår i: Journal of Molecular Modeling. - : Springer Science and Business Media LLC. - 0948-5023 .- 1610-2940. ; 21:1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- B3LYP/6-311++G** with dispersion correction (DFT-D) was used to study local and global minimum energy structures of water (H2O) or carbon dioxide (CO2) bonding with a pair of cellobiose molecules. The calculations showed that neither the H2O nor the CO2 prefer to be between the cellobiose molecules, and that the minimum energy structures occur when these molecules bond to the outer surface of the cellobiose pair. The calculations also showed that the low energy structures have a larger number of inter-cellobiose hydrogen bonds than the high energy structures. These results indicate that penetration of H2O or CO2 between adjacent cellobiose pairs, which would assist steam or supercritical CO2 (SC-CO2) explosion of cellulose, is not energetically favored. Comparison of the energies obtained with DFT-D and DFT (the same method but without dispersion correction) show that both hydrogen bonds and van der Waals interactions play an important role in cellobiose-cellobiose interactions.
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| 2. |
- Bazooyar, Faranak, 1972, et al.
(författare)
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Validating empirical force fields for molecular-level simulation of cellulose dissolution
- 2012
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Ingår i: Computational and Theoretical Chemistry. - : Elsevier BV. - 2210-271X .- 2210-2728. ; 984, s. 119-127
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Tidskriftsartikel (refereegranskat)abstract
- The calculations presented here, which include dynamics simulations using molecular mechanics force fields and first principles studies, indicate that the COMPASS force field is preferred over the Dreiding and Universal force fields for studying dissolution of large cellulose structures. The validity of these force fields was assessed by comparing structures and energies of cellobiose, which is the shortest cellulose chain, obtained from the force fields with those obtained from MP2 and DFT methods. In agreement with the first principles methods, COMPASS is the only force field of the three studied here that favors the anti form of cellobiose in the vacuum. This force field was also used to compare changes in energies when hydrating cellobiose with 1-4 water molecules. Although the COMPASS force field does not yield the change from anti to syn minimum energy structure when hydrating with h more than two water molecules - as predicted by OFT - it does predict that the syn conformer is preferred when simulating cellobiose in bulk liquid water and at temperatures relevant to cellulose dissolution. This indicates that the COMPASS force field yields valid structures of cellulose under these conditions. Simulations based on the COMPASS force field show that, due to entropic effects, the syn form of cellobiose is energetically preferred at elevated temperature, both in vacuum and in bulk water. This is also in agreement with DFT calculations.
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| 3. |
- Rousta, Kamran, et al.
(författare)
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Support for designing waste sorting systems : A mini review
- 2017
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Ingår i: Waste Management & Research. - : Sage Publications. - 0734-242X .- 1096-3669. ; 35:11, s. 1099-1111
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Tidskriftsartikel (refereegranskat)abstract
- This article presents a mini review of research aimed at understanding material recovery from municipal solid waste. It focuses on two areas, waste sorting behaviour and collection systems, so that research on the link between these areas could be identified and evaluated. The main results presented and the methods used in the articles are categorised and appraised. The mini review reveals that most of the work that offered design guidelines for waste management systems was based on optimising technical aspects only. In contrast, most of the work that focused on user involvement did not consider developing the technical aspects of the system, but was limited to studies of user behaviour. The only clear consensus among the articles that link user involvement with the technical system is that convenient waste collection infrastructure is crucial for supporting source separation. This mini review reveals that even though the connection between sorting behaviour and technical infrastructure has been explored and described in some articles, there is still a gap when using this knowledge to design waste sorting systems. Future research in this field would benefit from being multidisciplinary and from using complementary methods, so that holistic solutions for material recirculation can be identified. It would be beneficial to actively involve users when developing sorting infrastructures, to be sure to provide a waste management system that will be properly used by them.
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| 4. |
- Samadikhah, Kaveh, 1982, et al.
(författare)
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Continuum-molecular modelling of graphene
- 2012
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Ingår i: Computational materials science. - : Elsevier BV. - 0927-0256 .- 1879-0801. ; 53:1, s. 37-43
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Tidskriftsartikel (refereegranskat)abstract
- membranes using a hierarchical modeling strategy to bridge the scales required to describe and understand the material. Quantum Mechanical (QM) and optimized Molecular Mechanical (MM) models are used to describe details on the nanoscale, while a multiscale continuum mechanical method is used to model the graphene response at the device or micrometer scale. The complete method is obtained on the basis of the Cauchy Born Rule (CBR), where the continuum model is coupled to the atomic field via the CBR and a local discrete fluctuation field. The MM method, often used to model carbon structures, involves the Tersoff--Brenner (TB) potential; however, when applying this potential to graphene with standard parameters one obtains material stress behavior much weaker than experiments. On the other hand, the more fundamental Hartree Fock and Density Functional Theory (DFT) methods are computationally too expensive and very limited in terms of their applicability to model the geometric scale at the device level. In this contribution a simple calibration of some of the TB parameters is proposed in order to reproduce the results obtained from QM calculations. Subsequently, the fine-tuned TB--potential is used for the multiscale modeling of a nano indentation sample, where experimental data are available. Effects of the mechanical response due the calibration are demonstrated.
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| 5. |
- Satyanarayana, K. C., et al.
(författare)
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Analysis of the torsion angle distribution of poly(vinylidene fluoride) in the melt
- 2012
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 53:5, s. 1109-1114
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Tidskriftsartikel (refereegranskat)abstract
- Analysis of the torsion angle distribution of poly(vinylidene fluoride) (PVDF) structures at temperatures above its melting point is addressed by combining first principles methods, atomistic simulations and laboratory experiments. Amorphous, alpha- and beta-conformations of PVDF structures have been considered. The results from the atomistic simulations as well as the experiments show that there is a larger probability of the PVDF torsions to be near +/- 180 degrees at temperatures above the melting point, which is associated more with the beta-conformation than the alpha-conformation.
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