| 11. |
- Abdel Hady, Ahmed Wagih Abdallah, 1990, et al.
(författare)
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Micro/nano-structural evolution in spruce wood during soda pulping
- 2021
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 1437-434X .- 0018-3830. ; 75:8, s. 754-764
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Tidskriftsartikel (refereegranskat)abstract
- Alkaline delignification of wood tissue is the core of the global pulping technology and the most prominent large-scale separation of the main wood components. This work aims at improved understanding of the interplay between the topochemistry of alkaline pulping and the associated morphological changes. Morphology and chemical structure of partially soda-delignified wood chips were studied combining X-ray tomography (XRT), X-ray diffraction analysis and compositional characterization (lignin and carbohydrate content). The XRT studies of wet samples (providing 3D structural information without interfering drying effects), allowed observation of the cell wall separation as an increasing amount of lignin was removed with the increasing pulping time. Comparison between the microstructure of the surface and the central parts of the treated chips showed a more delignified microstructure at the surface, which highlights the dependence of the delignification process on the mass transport (hydroxide ions and lignin fragments) through the wood tissue. The crystallite size of cellulose increased in the <200> crystal planes during the early stage of pulping while there was little effect on the <110> plane.
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| 12. |
- Abdulaziz, Mohammed, 1983, et al.
(författare)
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A 10-mW mm-wave phase-locked loop with improved lock time in 28-nm FD-SOI CMOS
- 2019
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 67:4, s. 1588-1600
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 IEEE. This paper presents a millimeter-wave (mm-wave) phase-locked loop (PLL), with an output frequency centered at 54.65 GHz. It demonstrates a mode-switching architecture that considerably improves the lock time, by seamlessly switching between a low-noise mode and a fast-locking mode that is only used during settling. The improvement is used to counteract the increased lock-time caused by cycle-slips that results from using a high reference frequency of 2280 MHz, which is several hundred times the loop bandwidth. Such a reference frequency alleviates the noise requirements on the PLL and is readily available in 5G systems, from the radio frequency PLL. The mm-wave PLL is implemented in a low-power 28-nm fully depleted silicon-on-insulator CMOS process, and its active area is just 0.19 mm 2 . The PLL also features a novel double injection-locked divide-by-3 circuit and a charge-pump mismatch compensation scheme, resulting in state-of-the-art power consumption, and jitter performance in the low-noise mode. In this mode, the in-band phase noise is between-93 and-96 dBc/Hz across the tuning range, and the integrated jitter is between 176 and 212 fs. The total power consumption of the mm-wave PLL is only 10.1 mW, resulting in a best-case PLL figure-of-merit (FOM) of-245 dB. The lock time in low-noise mode is up to 12μs, which is improved to 3μs by switching to the fast-locking mode, at the temporary expense of a power consumption increase to 15.1 mW, an integrated jitter increase to between 245 and 433 fs, and an FOM increase to between-235 and-240 dB.
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| 13. |
- Abele, H., et al.
(författare)
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Particle physics at the European Spallation Source
- 2023
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Ingår i: Physics reports. - : Elsevier. - 0370-1573 .- 1873-6270. ; 1023, s. 1-84
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Forskningsöversikt (refereegranskat)abstract
- Presently under construction in Lund, Sweden, the European Spallation Source (ESS) will be the world’s brightest neutron source. As such, it has the potential for a particle physics program with a unique reach and which is complementary to that available at other facilities. This paper describes proposed particle physics activities for the ESS. These encompass the exploitation of both the neutrons and neutrinos produced at the ESS for high precision (sensitivity) measurements (searches).
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| 14. |
- Abgrall, N., et al.
(författare)
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The large enriched germanium experiment for neutrinoless double beta decay (LEGEND)
- 2017
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Ingår i: AIP Conference Proceedings. - : Author(s). - 1551-7616 .- 0094-243X. ; 1894
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Konferensbidrag (refereegranskat)abstract
- The observation of neutrinoless double-beta decay (0νββ) would show that lepton number is violated, reveal that neu-trinos are Majorana particles, and provide information on neutrino mass. A discovery-capable experiment covering the inverted ordering region, with effective Majorana neutrino masses of 15 - 50 meV, will require a tonne-scale experiment with excellent energy resolution and extremely low backgrounds, at the level of ∼0.1 count /(FWHM·t·yr) in the region of the signal. The current generation 76Ge experiments GERDA and the Majorana Demonstrator, utilizing high purity Germanium detectors with an intrinsic energy resolution of 0.12%, have achieved the lowest backgrounds by over an order of magnitude in the 0νββ signal region of all 0νββ experiments. Building on this success, the LEGEND collaboration has been formed to pursue a tonne-scale 76Ge experiment. The collaboration aims to develop a phased 0νββ experimental program with discovery potential at a half-life approaching or at 1028 years, using existing resources as appropriate to expedite physics results.
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| 15. |
- Abou-Taouk, Abdallah, 1982, et al.
(författare)
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CFD INVESTIGATION OF SWIRL-STABILIZED FLEXI-FUEL BURNER USING METHANE-AIR MIXTURE FOR GAS TURBINES
- 2011
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Ingår i: International Society for Airbreathing Engines, ISABE, Gothenburg, 2011. ; 1, s. 160-172
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Konferensbidrag (refereegranskat)abstract
- Combustion modeling based on a multi-step global reaction mechanism [1] is applied to CFD (Computational Fluid Dynamics) analysis of a scaled swirl-stabilized 4th generation premixed DLE (Dry Low Emission) burner for gas turbines. The flexi-fuel burner consists of a MAIN pre-mixed flame, a premixed PILOT flame and a confined RPL (Rich Pilot Lean) flame. Both steady-state RANS (Reynolds Averaged Navier Stokes) and hybrid URANS/LES (Unsteady RANS/Large Eddy Simulation) results have been computed. The results are compared with high quality experimental data in the form of emission data, PIV (Particle Image Velocimetry) data and OH-PLIF (Planar Laser Induced Fluorescence Imaging) from an atmospheric burner test rig at Lund University [2-3]. There is a good agreement between the CFD simulations and measurements of emissions, velocity field and flame visualization.
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| 16. |
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| 17. |
- Abrahamsson, Maria, et al.
(författare)
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Steric influence on the excited-state lifetimes of ruthenium complexes with bipyridyl-alkanylene-pyridyl ligands.
- 2008
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Ingår i: Inorganic Chemistry. - : ACS. - 0020-1669 .- 1520-510X. ; 47:9, s. 3540-3548
-
Tidskriftsartikel (refereegranskat)abstract
- The structural effect on the metal-to-ligand charge transfer (MLCT) excited-state lifetime has been investigated in bis-tridentate Ru(II)-polypyridyl complexes based on the terpyridine-like ligands [6-(2,2'-bipyridyl)](2-pyridyl)methane (1) and 2-[6-(2,2'-bipyridyl)]-2-(2-pyridyl)propane (2). A homoleptic ([Ru(2)(2)](2+)) and a heteroleptic complex ([Ru(ttpy)(2)](2+)) based on the new ligand 2 have been prepared and their photophysical and structural properties studied experimentally and theoretically and compared to the results for the previously reported [Ru(1)(2)](2+). The excited-state lifetime of the homoleptic Ru-II complex with the isopropylene-bridged ligand 2 was found to be 50 times shorter than that of the corresponding homoleptic Ru-II complex of ligand 1, containing a methylene bridge. A comparison of the ground-state geometries of the two homoleptic complexes shows that steric interactions involving the isopropylene bridges make the coordination to the central Ru-II ion less octahedral in [Ru(2)(2)](2+) than in [Ru(1)(2))(2+). Calculations indicate that the structural differences in these complexes influence their ligand field splittings as well as the relative stabilities of the triplet metal-to-ligand charge transfer ((MLCT)-M-3) and metal-centered ((MC)-M-3) excited states. The large difference in measured excited-state lifetimes for the two homoleptic Ru-II complexes is attributed to a strong influence of steric interactions on the ligand field strength, which in turn affects the activation barriers for thermal conversion from (MLCT)-M-3 states to short-lived (MC)-M-3 states.
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| 18. |
- Abrahmsén-Alami, Susanna, et al.
(författare)
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New release cell for NMR microimaging of tablets Swelling and erosion of poly(ethylene oxide)
- 2007
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Ingår i: International Journal of Pharmaceutics. - : Elsevier BV. - 0378-5173 .- 1873-3476. ; 342:1-2, s. 105-114
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Tidskriftsartikel (refereegranskat)abstract
- A small release cell, in the form of a rotating disc, has been constructed to fit into the MRI equipment. The present work show that both qualitative and quantitative information of the swelling and erosion behavior of hydrophilic extended release (ER) matrix tablets may be obtained using this release cell and non-invasive magnetic resonance imaging (MRI) studies at different time-points during matrix dissolution. The tablet size, core size and the gel layer thickness of ER matrix formulations based on poly(ethylene oxide) have been determined. The dimensional changes as a function of time were found to correspond well to observations made with texture analysis (TA) methodology. Most importantly, the results of the present study show that both the erosion (displacement of the gel-dissolution media interface) and the swelling (decrease of dry tablet core size) proceed with a faster rate in radial than in axial direction using the rotating disk set-up. This behavior was attributed to the higher shear forces experienced in the radial direction. The results also indicate that front synchronization (constant gel layer thickness) is associated with the formation of an almost constant polymer concentration profile through the gel layer at different time-points.
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| 19. |
- Addazi, A., et al.
(författare)
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New high-sensitivity searches for neutrons converting into antineutrons and/or sterile neutrons at the HIBEAM/NNBAR experiment at the European Spallation Source
- 2021
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Ingår i: Journal of Physics G. - : Institute of Physics Publishing (IOPP). - 0954-3899 .- 1361-6471. ; 48:7
-
Tidskriftsartikel (refereegranskat)abstract
- The violation of baryon number, , is an essential ingredient for the preferential creation of matter over antimatter needed to account for the observed baryon asymmetry in the Universe. However, such a process has yet to be experimentally observed. The HIBEAM/NNBAR program is a proposed two-stage experiment at the European Spallation Source to search for baryon number violation. The program will include high-sensitivity searches for processes that violate baryon number by one or two units: free neutron–antineutron oscillation () via mixing, neutron–antineutron oscillation via regeneration from a sterile neutron state (), and neutron disappearance (n → n'); the effective process of neutron regeneration () is also possible. The program can be used to discover and characterize mixing in the neutron, antineutron and sterile neutron sectors. The experiment addresses topical open questions such as the origins of baryogenesis and the nature of dark matter, and is sensitive to scales of new physics substantially in excess of those available at colliders. A goal of the program is to open a discovery window to neutron conversion probabilities (sensitivities) by up to three orders of magnitude compared with previous searches. The opportunity to make such a leap in sensitivity tests should not be squandered. The experiment pulls together a diverse international team of physicists from the particle (collider and low energy) and nuclear physics communities, while also including specialists in neutronics and magnetics.
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| 20. |
- Adebahr, Josefina, et al.
(författare)
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Cation coordination in ion-conducting gels based on PEO-grafted polymers
- 2000
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Ingår i: Solid State Ionics. - 0167-2738. ; 135:1-4, s. 149-154
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Tidskriftsartikel (refereegranskat)abstract
- Ionic conducting polymer gels prepared from PEG-grafted acrylates, ethylene carbonate (EC), dimethyl carbonate (DMC), and LiPF6 are studied by means of infrared and Raman spectroscopy. It is found that the presence of grafted PEO chains substantially changes the coordination of lithium cations from 'cation-solvent' to 'cation-polymer'. Spectroscopic studies show that Li+-PEO coordination is strongly favored in competition with the solvent molecules and dominates completely at ether oxygen to Li-cation ratios (O:Li) of 10:1 and 5:1. At an O:M of 4:1 a solvent-cation interaction arises, in agreement with previously reported MD calculations of a preferred coordination number of 5 in similar systems. The results suggest that the complex interactions which determine long time stability and ionic transport properties can be designed by functionalization of the polymer backbone in PMMA-based gel electrolytes.
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