SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "AMNE:(TEKNIK OCH TEKNOLOGIER) AMNE:(Kemiteknik) "

Sökning: AMNE:(TEKNIK OCH TEKNOLOGIER) AMNE:(Kemiteknik)

  • Resultat 1-50 av 12389
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  •  
2.
  • Eivazihollagh, Alireza, et al. (författare)
  • On chelating surfactants : Molecular perspectives and application prospects
  • 2019
  • Ingår i: Journal of Molecular Liquids. - : Elsevier BV. - 0167-7322 .- 1873-3166. ; 278, s. 688-705
  • Tidskriftsartikel (refereegranskat)abstract
    • Chelating agents, molecules that very strongly coordinates certain metal ions, are used industrially as well as in consumer products to minimize disturbances and increase performance of reactions and applications. The widely used sequestering agents, nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) belong to this branch of readily water-soluble compounds. When these chemical structures also have hydrophobic parts, they are prone to adsorb at air-water interfaces and to self-assemble. Such bifunctional molecules can be called chelating surfactants and will have more extended utilization prospects than common chelating agents or ordinary ionic surfactants. The present review attempts to highlight the fundamental behavior of chelating surfactants in solution and at interfaces, and their very specific interactions with metal ions. Methods to recover chelating surfactants from metal chelates are also described. Moreover, utilization of chelating surfactants in applications for metal removal in environmental engineering and mineral processing, as well as for metal control in the fields of biology, chemistry and physics, is exemplified and discussed.
  •  
3.
  • Trigo, João Pedro, 1995, et al. (författare)
  • Mild blanching prior to pH-shift processing of Saccharina latissima retains protein extraction yields and amino acid levels of extracts while minimizing iodine content
  • 2023
  • Ingår i: Food Chemistry. - : Elsevier BV. - 0308-8146 .- 1873-7072. ; 404
  • Tidskriftsartikel (refereegranskat)abstract
    • The seaweed Saccharina latissima is often blanched to lower iodine levels, however, it is not known how blanching affects protein extraction. We assessed the effect of blanching or soaking (80/45/12 °C, 2 min) on protein yield and protein extract characteristics after pH-shift processing of S. latissima. Average protein yields and extract amino acid levels ranked treatments as follows: blanching-45 °C ∼ control > soaking ∼ blanching-80 °C. Although blanching-45 °C decreased protein solubilization yield at pH 12, it increased isoelectric protein precipitation yield at pH 2 (p < 0.05). The former could be explained by a higher ratio of large peptides/proteins in the blanched biomass as shown by HP-SEC, whereas the latter by blanching-induced lowering of ionic strength, as verified by a dialysis model. Moreover, blanching-45 °C yielded a protein extract with 49 % less iodine compared with the control extract. We recommend blanching-45 °C since it is effective at removing iodine and does not compromise total protein extraction yield.
  •  
4.
  • Grishenkov, Dmitry, 1983-, et al. (författare)
  • Characterization of Acoustic Properties of PVA-Shelled Ultrasound Contrast Agents
  • 2010
  • Ingår i: Ultrasound Contrast Agents. - Italia : Springer-Verlag. - 9788847014930 ; , s. 99-108
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • This work examines the acoustic behavior of ultrasound contrast agents made of poly (vinyl alcohol) (PVA) shelled microbubbles manufactured at three different pH and temperature conditions. Backscattering amplitude, attenuation coefficient and phase velocity of ultrasonic waves propagating through suspensions of PVA contrast agents were measured at temperature values ranging between 24 oC and 37 oC in a frequency range from 3 MHz to 13 MHz.  A significant enhancement of the backscattering amplitude and displaying a weak dependence on temperature were observed.  Attenuation and phase velocity, on the other hand, showed higher sensitivity to temperature variations.  The dependence on system parameters such as the number of cycles, frequency, and exposure of the peak negative pressure, Pthr, at which ultrasound contrast agents fracture was also investigated.  The effects of temperature, blood, and, wherever data are available, of the dimension of the microbubbles on Pthr are also considered.  The large shell thickness notwithstanding, the results of this investigation show that at room temperature PVA contrast agents fracture at negative peak pressure values within the recommended safety limit.  Furthermore, Pthr decreases with increasing temperature, radius of the microbubbles, and number of cycles of the incident wave.  In conclusion, these results suggest that PVA-shelled microbubbles may offer a potentially viable system to be employed for both imaging and therapeutic purposes.
  •  
5.
  • Hoveskog, Maya (författare)
  • Innovation-related Activities in a Low-tech Industry : A Study of the Electroplating and Surface Treatment Industry in Sweden
  • 2011
  • Ingår i: Research on Technology, Innovation and Marketing Management 2009‐2011. - Halmstad : Högskolan i Halmstad. - 9789197507516 ; , s. 55-81
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • Given the complex and interdependent nature of innovation, it is a diverse phenomenon which takes place both in high‐ and low‐tech industries. The purpose of this paper is to increase our understanding about low‐tech industries’ innovation‐related activities and the specific capabilities of the companies that influence those. To achieve this purpose this study has performed an empirical analysis of the Swedish context of the Swedish Electroplating and Surface Treatment Industry (ESTI) and the characteristics of the companies operating in it. It investigated how the companies perceived their expertise and innovative activities in comparison with their main competitors. The main types of innovation the ESTI companieshad undertaken in a three‐year period (2004–2006) were studied. The research and development (R&D) and personnel qualification improvement expenditures were explored. The study looked into collaboration and the factors which companies perceived as important in order to collaborate. Our empirical evidence shows that innovation in the ESTI is shaped notby R&D but by other determinants, such as specific and rare capabilities in, for example, processing technologies, logistics, ability to spot, evaluate and exploit external knowledge as well as their ability to establish and sustain intercompany relationships. Strong relationships and integration with customers and suppliers emerge as pivotal for the innovation‐related activities in the ESTI. Additionally, close collaboration, facilitated by a strong intermediate institution, such as the Swedish Association of Surface Treatment Companies (Svensk YtbehandlingsFörening – SYF, also shape the innovation‐related activities in the ESTI.
  •  
6.
  •  
7.
  • Almgren, Karin, et al. (författare)
  • Role of fibre-fibre and fibre-matrix adhesion in stress transfer in composites made from resin-impregnated paper sheets.
  • 2009
  • Ingår i: International Journal of Adhesion and Adhesives. - : Elsevier BV. - 0143-7496 .- 1879-0127. ; 29:5, s. 551-557
  • Tidskriftsartikel (refereegranskat)abstract
    • Paper-reinforced plastics are gaining increased interest as packaging materials, where mechanical properties are of great importance. Strength and stress transfer in paper sheets are controlled by fibre-fibre bonds. In paper-reinforced plastics, where the sheet is impregnated with a polymer resin, other stress-transfer mechanisms may be more important. The influence of fibre-fibre bonds on the strength of paper-reinforced plastics was therefore investigated. Paper sheets with different degrees of fibre-fibre bonding were manufactured and used as reinforcement in a polymeric matrix. Image analysis tools were used to verify that the difference in the degree of fibre-fibre bonding had been preserved in the composite materials. Strength and stiffness of the composites were experimentally determined and showed no correlation to the degree of fibre-fibre bonding, in contrast to the behaviour of unimpregnated paper sheets. The degree of fibre-fibre bonding is therefore believed to have little importance in this type of material, where stress is mainly transferred through the fibre-matrix interface.
  •  
8.
  • Bessman, Alexander, et al. (författare)
  • Aging effects of AC harmonics on lithium-ion cells
  • 2019
  • Ingår i: Journal of Energy Storage. - : Elsevier. - 2352-152X .- 2352-1538. ; 21, s. 741-749
  • Tidskriftsartikel (refereegranskat)abstract
    • With the vehicle industry poised to take the step into the era of electric vehicles, concerns have been raised that AC harmonics arising from switching of power electronics and harmonics in electric machinery may damage the battery. In light of this, we have studied the effect of several different frequencies on the aging of 28 Ah commercial NMC/graphite prismatic lithium-ion battery cells. The tested frequencies are 1 Hz, 100 Hz, and 1 kHz, all with a peak amplitude of 21 A. Both the effect on cycled cells and calendar aged cells is tested. The cycled cells are cycled at a rate of 1C:1C, i.e., 28 A during both charging and discharging, with the exception of a period of constant voltage at the end of every charge. After running for one year, the cycled cells have completed approximately 2000 cycles. The cells are characterized periodically to follow how their capacities and power capabilities evolve. After completion of the test about 80% of the initial capacity remained and no increase in resistance was observed. No negative effect on either capacity fade or power fade is observed in this study, and no difference in aging mechanism is detected when using non-invasive electrochemical methods of post mortem investigation.
  •  
9.
  •  
10.
  • Lindström, Stefan B, 1974-, et al. (författare)
  • A numerical investigation of the rheology of sheared fiber suspensions
  • 2009
  • Ingår i: Physics of fluids. - : AIP Publishing. - 1070-6631 .- 1089-7666. ; 21:8, s. 083301-
  • Tidskriftsartikel (refereegranskat)abstract
    • Particle-level simulations are performed to study the rheology of monodispersed non-Brownian fibers suspended in a Newtonian fluid in shear flow. The effects of fiber aspect ratio, concentration, and interparticle friction on the stress tensor of the suspension in the steady state and on the tendency of fiber agglomeration are investigated. Semiempirical expressions for the steady state apparent shear viscosity and the steady state first and second normal stress difference were obtained for the case of well dispersed suspensions in the nonconcentrated regimes. The simulation predictions of the specific viscosity were in fair agreement with previous experimental investigations.
  •  
11.
  • Lindström, Stefan B, 1974-, et al. (författare)
  • Simulation of semidilute suspensions of non-Brownian fibres in shear flow
  • 2008
  • Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 128:2, s. 024901-
  • Tidskriftsartikel (refereegranskat)abstract
    • Particle-level simulations are performed to study semidilute suspensions of monodispersed non-Brownian fibers in shear flow, with a Newtonian fluid medium. The incompressible three-dimensional Navier-Stokes equations are used to describe the motion of the medium, while fibers are modeled as chains of fiber segments, interacting with the fluid through viscous drag forces. The two-way coupling between the solids and the fluid phase is taken into account by enforcing momentum conservation. The model includes long-range and short-range hydrodynamic fiber-fiber interactions, as well as mechanical interactions. The simulations rendered the time-dependent fiber orientation distribution, whose time average was found to agree with experimental data in the literature. The viscosity and first normal stress difference was calculated from the orientation distribution using the slender body theory of Batchelor [J. Fluid Mech. 46, 813--829 (1971)], with corrections for the finite fiber aspect ratios. The viscosity was also obtained from direct computation of the shear stresses of the suspension for comparison. These two types of predictions compared well in the semidilute regime. At higher concentrations, however, a discrepancy was seen, most likely due to mechanical interactions, which are only accounted for in the direct computation method. The simulated viscosity determined directly from shear stresses was in good agreement with experimental data found in the literature. The first normal stress difference was found to be proportional to the square of the volume concentration of fibers in the semidilute regime. As concentrations approached the concentrated regime, the first normal stress difference became proportional to volume concentration.
  •  
12.
  • Lindström, Stefan B, 1974-, et al. (författare)
  • Simulation of the motion of flexible fibres in viscous fluid flow
  • 2007
  • Ingår i: Physics of fluids. - : AIP Publishing. - 1070-6631 .- 1089-7666. ; 19:11, s. 113307-1-113307-16
  • Tidskriftsartikel (refereegranskat)abstract
    • A model for flexible fibers in viscous fluid flow is proposed, and its predictions compared with experiments found in the literature. The incompressible three-dimensional Navier-Stokes equations are employed to describe the fluid motion, while fibers are modeled as chains of fiber segments, interacting with the fluid through viscous and dynamic drag forces. Fiber segments, from the same or from different fibers, interact with each other through normal, frictional and lubrication forces. Momentum conservation is enforced on the system to capture the two-way coupling between phases. Quantitative predictions could be made, and showed good agreement with experimental data, for the period time of Jeffery orbits in shear flow, as well as for the amount of bending of flexible fibers in shear flow. Simulations, using the proposed model, also successfully reproduced the different regimes of motion for threadlike particles, ranging from rigid fiber motion to complicated orbiting behavior, including coiling and self-entanglement.
  •  
13.
  • Moldenhauer, Patrick, 1983, et al. (författare)
  • Chemical-looping combustion with heavy liquid fuels in a 10 kW pilot plant
  • 2017
  • Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 156, s. 124-137
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, chemical-looping combustion was performed with highly viscous vacuum residue. A fuel reactor with a fuel-injection system for liquid fuels was designed and built for a chemical-looping reactor with the nominal fuel input of 10 kWth. The gas velocities in the riser section and at the gas-distribution nozzles of this unit are comparable to those of industrial circulating fluidized-bed boilers. Reference experiments were performed with an ilmenite oxygen carrier and two different fuel blends that contained 40 wt.% and respectively 80 wt.% of vacuum residue in fuel oil 1. Fuel conversion was in line with that of experiments from an earlier campaign, where fuel oil 1 was used as fuel. The fuel contained a significant fraction of sulfur, but no SO2 was detected in the flue gas of the air reactor. More experiments were performed using an oxygen carrier based on calcium manganite. The oxygen carrier was exposed to fluidization at hot conditions (more than 600°C) for about 95 h, out of which fuel was injected during a total of 9.6 h. Undiluted vacuum residue, fuel oil 1 as well as different blends of these two were used as fuel. Furthermore, the parameters fuel flow, fuel-reactor temperature and air flow in the air reactor were varied to observe trends in fuel conversion. The experiments were carried out with a fuel flow corresponding to 4.0-6.2 kWth and an oxygen carrier-to-fuel ratio of about 1300-2000 kg/MWth (fuel-reactor bed mass per thermal fuel-power). With undiluted vacuum residue as fuel and a fuel-reactor temperature of 1000°C, up to 93% of all carbon leaving the fuel reactor was in the form of CO2. Carbon leakage from fuel reactor to air reactor was usually below 1% for all fuel types tested, but no SO2 was detected in the off-gas from the air reactor. The reactivity of the calcium manganite-based material decreased over the course of the experiments, which is likely due to sulfur poisoning. No defluidization or agglomeration problems were experienced over the course of the experimental campaign.
  •  
14.
  • Kihlman, Martin, et al. (författare)
  • Cellulose Dissolution in an Alkali Based Solvent : Influence of Additives and Pretreatments
  • 2013
  • Ingår i: Journal of the Brazilian Chemical Society. - : SOC BRASILEIRA QUIMICA, Brazil. - 0103-5053 .- 1678-4790. ; 24:2, s. 295-303
  • Tidskriftsartikel (refereegranskat)abstract
    • The distinction between thermodynamic and kinetics in cellulose dissolution is seldom considered in the literature. Therefore, herein an attempt to discuss this topic and illustrate our hypotheses on the basis of simple experiments was made. It is well-known that cellulose can be dissolved in a aqueous sodium hydroxide (NaOH/H2O) solvent at low temperature but it is here shown that such an alkaline solvent can be considerably improved regarding solubility, stability and rheological properties as a whole if different additives (salts and amphiphilic molecules) are used in the dissolution stage. This work probes new aqueous routes to dissolve cellulose, thereby improving the potential to commercially dissolve cellulose in an inexpensive and environmentally friendly manner.
  •  
15.
  • Marra, Eva, et al. (författare)
  • Oxygen reduction reaction kinetics on a Pt thin layer electrode in AEMFC
  • 2022
  • Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 435, s. 141376-141376
  • Tidskriftsartikel (refereegranskat)abstract
    • The study of the catalytic activity in a fuel cell is challenging, as mass transport, gas crossover and the counterelectrode are generally interfering. In this study, a Pt electrode consisting of a thin film deposited on the gasdiffusion layer was employed to study the oxygen reduction reaction (ORR) in an operating Anion Exchange Membrane Fuel Cell (AEMFC). The 2D Pt electrode was assembled together with a conventional porous Pt/Ccounter electrode and an extra Pt/C layer and membrane to reduce the H2 crossover. Polarization curves atdifferent O2 partial pressures were recorded and the resulting reproducible ORR activities were normalized withrespect to the active surface area (ECSA), obtained by CO stripping. As expected, decreasing the O2 partialpressure results in a negative shift in open circuit voltage (OCV), cell voltage and maximum attainable currentdensity. For cell voltages above 0.8 V a fairly constant Tafel slope of 60 mV dec−1 was recorded but at lowervoltages the slope increases rapidly. The observed Tafel slope can be explained by a theoretical model with anassociative mechanism where charge- and proton-transfer steps are decoupled, and the proton transfer is the rate-determining step. A reaction order of 1 with respect to O2 was obtained at 0.65 V which corresponds well withthe mechanism suggested above. Based on the obtained catalyst activities, the electrode performance is com­parable to good porous electrodes found in the field. The methodology presented in this study is expected to beuseful in future kinetic studies of other catalysts for AEMFC.
  •  
16.
  • Syed, Hanif Uddin, et al. (författare)
  • A comparison of cold and hot caustic extraction of a spruce dissolving sulfite pulp prior to final bleaching
  • 2013
  • Ingår i: Appita journal. - : Appita. - 1038-6807. ; 66:3, s. 229-234
  • Tidskriftsartikel (refereegranskat)abstract
    • A magnesium sulfite pulp producer modified its pulping process to dissolving pulping in 2011 and needed a purification stage after the digester to obtain a sufficiently low hemicellulose content. The dissolving pulp was intended for viscose production and an R-18 value of at least 95% and an intrinsic viscosity below 550 dm(3)/kg was requested. The results showed, as could be expected, a correlation between lower dissolving pulp yield and a higher degree Of purification with respect to cellulose. The R-18 values and the intrinsic viscosities of the dissolving pulps were found to increase with increasing sodium hydroxide concentration and/or higher temperature in the extraction Stage. The pulp yield was found to be higher with higher temperature for the cold caustic extraction stage (CCE); for hot caustic extraction (HQ E) the pulp yield became lower with higher temperature. The specified R-18 value was easiest to reach using hot caustic extraction.
  •  
17.
  • Das, Oisik, et al. (författare)
  • Naturally-occurring bromophenol to develop fire retardant gluten biopolymers
  • 2020
  • Ingår i: Journal of Cleaner Production. - : Elsevier. - 0959-6526 .- 1879-1786. ; 243
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of the study was to impart fire retardancy in wheat gluten polymer through naturally-occurring additives such as lanosol. The fire properties of lanosol were compared with two other conventional brominated fire retardants (Tetrabromobisphenol A and Hexabromocyclododecane). Samples containing fire retardants and gluten were prepared through compression moulding process and then characterised for their fire and mechanical properties. All fire retardants enhanced the reaction-to-fire and thermal properties of gluten while generating V-0 (i.e. vertical position and self-extinguished) ratings in the UL-94 test. The presence of all the fire retardants increased the modulus of the gluten polymer but the fire retardant particles were detrimental for the tensile strength. Nevertheless, lanosol addition delayed ignition and lowered peak heat release rate of gluten by the maximum amount, thereby leading to relatively higher fire performance index (compared to the other fire retardants). Lanosol also allowed the gluten to create a dense char barrier layer during burning that impeded the transfer of heat and flammable volatiles. The fact that only 4 wt% lanosol was able to cause self-extinguishment under direct flame and reduce peak heat release rate by a significant 50% coupled with its inherent occurrence in nature, raises the question if lanosol can be a potential fire retardant in polymeric systems, although it is a bromophenol.
  •  
18.
  • Kulachenko, Artem, et al. (författare)
  • Reinventing mechanics of fibre network
  • 2008
  • Ingår i: Progress in Paper Physics Seminar. - Helsinki : Helsinki University Press. ; , s. 185-193
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)
  •  
19.
  • Lindström, Stefan B, 1974-, et al. (författare)
  • A model for flexible fibres in viscous and inert fluid
  • 2007
  • Ingår i: 61st Appita annual conference and exhibition, Gold Coast, Australia, 6-9 May 2007, 2007 International paper physics conference, 6pp [Carlton, Australia: Appita, 2007. ; , s. 23-28, s. 23-28
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • A model is proposed for simulating the motion of flexible fibres in fluid flow. Care has been taken to include typical papermaking conditions into the validity range of the model. Fibres are modelled as chains of fibre segments, whose motion is governed by Newton's second law. The fluid motion is calculated from the three-dimensional incompressible Navier-Stokes equations. By enforcing momentum conservation, the two-way coupling between the solids and fluid phase is taken into account. Fibre-fibre interactions as well as self-interactions include normal, frictional and lubrication forces. Furthermore, the model considers nonlaminar fibre-fluid interactions and particle inertia. Simulation results were compared with experimental data found in the literature. The model predicts very well the orbit period of rigid fibre motion in shear flow. Quantitative predictions were made for the amount of bending of flexible fibres in shear flow. It was also possible to reproduce the different regimes of motion of flexible fibres in shear flow, ranging from rigid motion to coiled motion and self-entanglement.
  •  
20.
  • Lindström, Stefan B, 1974-, et al. (författare)
  • Evolution of the paper structure along the length of a twin-wire former
  • 2009
  • Ingår i: ADVANCES IN PULP AND PAPER RESEARCH, OXFORD 2009, VOLS 1-3. - Bury, UK : Pulp Paper Fund. Res. Soc.. - 9780954527266 ; , s. 207-245, s. 207-245
  • Konferensbidrag (refereegranskat)abstract
    • A particle-level numerical model is used to simulate forming with a twin-wire former configuration. The development of the paper structure along the length of the former is observed to explain the effects ofthe dewatering elements on the paper structure at different jet-to-wire speed ratios, consistencies, and target basis weights. The simulations indicate that most of the structure development takes place in the initial part of forming (forming roll) and, in some instances, at the drop to atmospheric pressure after the forming roll. Dramatic effects onthe through-thickness fibre orientation anisotropy are observed when the consistency is varied by changing the jet thickness, while changes in basis weight had less impact. The through-thickness concentration gradient was almost uniform throughout the forming process, except in the lower range of typical papermaking consistencies. This indicates that the dewatering mechanism is normally thickening, rather than filtration.
  •  
21.
  • Lindström, Stefan B, 1974- (författare)
  • Modelling and simulation of paper structure development
  • 2008
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    •      A numerical tool has been developed for particle-level simulations of fibre suspension flows, particularly forming of the fibre network structure of paper sheets in the paper machine. The model considers inert fibres of various equilibrium shapes, and finite stiffness, interacting with each other through normal, frictional, and lubrication forces, and with the surrounding fluid medium through hydrodynamic forces. Fibre–fluid interactions in the non-creeping flow regime are taken into account, and the two-way coupling between the solids and the fluid phases is included by enforcing momentum conservation between phases. The incompressible three-dimensional Navier–Stokes equations are employed tomodel themotion of the fluid medium.The validity of the model has been tested by comparing simulation results with experimental data from the literature. It was demonstrated that the model predicts well the motion of isolated fibres in shear flow over a wide range of fibre flexibilities. It was also shown that the model predicts details of the orientation distribution of multiple, straight, rigid fibres in a sheared suspension. Furthermore, model predictions of the shear viscosity and first normal stress difference were in fair agreement with experimental data found in the literature. Since the model is based solely on first principles physics, quantitative predictions could be made without any parameter fitting. Based on these validations, a series of simulations have been performed to investigate the basic mechanisms responsible for the development of the stress tensor components for monodispersed, non-Brownian fibres suspended in a Newtonian fluid in shear flow. The effects of fibre aspect ratio, concentration, and inter-particle friction, as well as the tendency of fibre agglomeration, were examined in the nonconcentrated regimes. For the case of well dispersed suspensions, semi-empirical relationships were found between the aforementioned fibre suspension properties, and the steady state apparent shear viscosity, and the first/second normal stress differences. Finally, simulations have been conducted for the development of paper structures in the forming section of the paper machine. The conditions used for the simulations were retrieved from pilot-scale forming trial data in the literature, and from real pulp fibre analyses. Dewatering was simulated by moving two forming fabrics toward each other through a fibre suspension. Effects of the jet-to-wire speed difference on the fibre orientation anisotropy, the mass density distribution, and three-dimensionality of the fibre network, were investigated. Simulation results showed that the model captures well the essential features of the forming effects on these paper structure parameters, and also posed newquestions on the conventional wisdom of the forming mechanics.  
  •  
22.
  • Lindström, Stefan B, 1974- (författare)
  • Simulations of the Dynamics of Fibre Suspension Flows
  • 2007
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • A new model for simulating non-Brownian flexible fibres suspended in a Newtonian fluid has been developed. Special attention has been given to include realistic flow conditions found in the industrial papermaking process in the key features of the model; it is the intention of the author to employ the model in simulations of the forming section of the paper machine in future studies.The model considers inert fibres of various shapes and finite stiffness, interacting with each other through normal, frictional and lubrication forces, and with the surrounding fluid medium through hydrodynamic forces. Fibre-fluid interactions in the non-creeping flow regime are taken into account, and the two-way coupling between the solids and the fluid phase is included by enforcing momentum conservation between phases. The incompressible three-dimensional Navier-Stokes equations are employed to model the motion of the fluid medium.The validity of the model has been tested by comparing simulation results with experimental data from the literature. It was demonstrated that the model predicts the motion of isolated fibres in shear flow over a wide range of fibre flexibilities. It was also shown that the model predicts details of the orientation distribution of multiple straight, rigid fibres in a sheared suspension. Model predictions of the viscosity and first normal stress difference were in good agreement with experimental data found in the literature. Since the model is based solely on first-principles physics, quantitative predictions could be made without any parameter fitting.
  •  
23.
  •  
24.
  • Salvador, Christian Mark, 1989, et al. (författare)
  • Indoor ozone/human chemistry and ventilation strategies
  • 2019
  • Ingår i: Indoor Air. - : Hindawi Limited. - 1600-0668 .- 0905-6947. ; 29:6, s. 913-925
  • Tidskriftsartikel (refereegranskat)abstract
    • This study aimed to better understand and quantify the influence of ventilation strategies on occupant-related indoor air chemistry. The oxidation of human skin oil constituents was studied in a continuously ventilated climate chamber at two air exchange rates (1 h-1 and 3 h-1 ) and two initial ozone mixing ratios (30 and 60 ppb). Additional measurements were performed to investigate the effect of intermittent ventilation ("off" followed by "on"). Soiled t-shirts were used to simulate the presence of occupants. A time-of-flight-chemical ionization mass spectrometer (ToF-CIMS) in positive mode using protonated water clusters was used to measure the oxygenated reaction products geranyl acetone, 6-methyl-5-hepten-2-one (6-MHO) and 4-oxopentanal (4-OPA). The measurement data were used in a series of mass balance models accounting for formation and removal processes. Reactions of ozone with squalene occurring on the surface of the t-shirts are mass transport limited; ventilation rate has only a small effect on this surface chemistry. Ozone-squalene reactions on the t-shirts produced gas-phase geranyl acetone, which was subsequently removed almost equally by ventilation and further reaction with ozone. About 70% of gas-phase 6-MHO was produced in surface reactions on the t-shirts, the remainder in secondary gas-phase reactions of ozone with geranyl acetone. 6-MHO was primarily removed by ventilation, while further reaction with ozone was responsible for about a third of its removal. 4-OPA was formed primarily on the surfaces of the shirts (~60%); gas-phase reactions of ozone with geranyl acetone and 6-MHO accounted for ~30% and ~10%, respectively. 4-OPA was removed entirely by ventilation. The results from the intermittent ventilation scenarios showed delayed formation of the reaction products and lower product concentrations compared to continuous ventilation.
  •  
25.
  • Lie, Christer, et al. (författare)
  • Aspects of water-induced mottle when printing on coated paper in sheet-fed lithographic offset
  • 2007
  • Ingår i: ADVANCES IN PRINTING AND MEDIA TECHNOLOGY, VOL XXXIV  . - Zagreb : ACTA GRAPHICA PUBL. ; , s. 59-67
  • Konferensbidrag (refereegranskat)abstract
    • Uneven print density, print mottle or mottle, call cause severe print quality problems and is a frequent problem for printers. Print mottle can occur ill sheet-fed offset due to several reasons related to both the paper and its coating and the printing press. The aim of the project was therefore to improve our knowledge of the influence on mottle related to the fountain solution which dampens the paper surface, water induced mottle. Pilot coated papers were produced and printed in a full-scale 4-colour sheet-fed offset printing press. During printing a specially designed test form was used. This must be used together with a blanket which has cut-out areas corresponding to the areas oil the test form. In this way it is possible to create a number of different printing situations oil the same printed paper sheet. The results from the print trials show that fountain solution from the previous printing unit can cause a decreased print density and dot gain. Water induced print mottle is Caused by the fountain solution from the previous printing unit. Back-trap from the following print units Will have a smoothing effect and will decrease the mottle. The results are based oil a hypothesis test at the 5% level. Water induced mottle can be related to both the printing process and the paper. The structure of the paper coating, Uneven porosity distribution, has a high influence oil water induced mottle while the effect of the Surface chemistry is low. The paper with high SB latex content showed the most uneven porosity distribution.
  •  
26.
  • Soares, Rúdi, 1984-, et al. (författare)
  • Li-ion battery and dc-link capacitor technologies – Electric drivetrain applications : A literature study
  • 2014
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Modern electrical vehicle drivetrains use a DC-link capacitor to decouple the battery from the power electronics.This topology is thought to be necessary for a number of reasons, including among others preventing damage to the battery and reducing electromagnetic interference.However, the DC-link capacitor is a bulky component which makes the entire drivetrain less modular by its presence.For this reason, an interdisciplinary research project has been launched to investigate the possibility of improving electrical vehicle drivetrains by having PhD students from the fields of electrical engineering and applied electrochemisty working closely together.The initial goal of this project will be to attempt to remove the DC-link capacitor entirely, in order to determine whether this adversely affects the battery longevity.Depending on the results from this initial test, other potential problems with removing the DC-link capacitor will be identfied and addessed.
  •  
27.
  • Andersson, Helene, 1983, et al. (författare)
  • Effects of molecular weight on permeability and microstructure of mixed ethyl-hydroxypropyl-cellulose films
  • 2013
  • Ingår i: European Journal of Pharmaceutical Sciences. - : Elsevier BV. - 0928-0987 .- 1879-0720. ; 48:1-2, s. 240-248
  • Tidskriftsartikel (refereegranskat)abstract
    • Films of ethyl cellulose (EC) and water-soluble hydroxypropyl cellulose (HPC) can be used for extended release coatings in oral formulations. The permeability and microstructure of free EC/HPC films with 30% w/w HPC were studied to investigate effects of EC molecular weight. Phase separation during film spraying and subsequent HPC leaching after immersion in aqueous media cause pore formation in such films. It was found that sprayed films were porous throughout the bulk of the films after water immersion. The molecular weight affected HPC leaching, pore morphology and film permeability; increasing the molecular weight resulted in decreasing permeability. A model to distinguish the major factors contributing to diffusion retardation in porous films showed that the trend in permeability was determined predominantly by factors associated with the geometry and arrangement of pores, independent of the diffusing species. The film with the highest molecular weight did, however, show an additional contribution from pore wall/permeant interactions. In addition, rapid drying and increasing molecular weight resulted in smaller pores, which suggest that phase separation kinetics affects the final microstructure of EC/HPC films. Thus, the molecular weight influences the microstructural features of pores, which are crucial for mass transport in EC/HPC films.
  •  
28.
  • Cho, Sung-Woo, et al. (författare)
  • Properties of Wheat Gluten/Poly(lactic acid) Laminates
  • 2010
  • Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 58:12, s. 7344-7350
  • Tidskriftsartikel (refereegranskat)abstract
    • Laminates of compression-molded glycerol-plasticized wheat gluten (WG) films surrounded and supported by poly(lactic acid) (PLA) films have been produced and characterized. The objective was to obtain a fully renewable high gas barrier film with sufficient mechanical integrity to function in, for example, extrusion-coating paper/board applications. It was shown that the lamination made it possible to make films with a broad range of glycerol contents (0-30 wt %) with greater strength than single unsupported WG films. The low plasticizer contents yielded laminates with very good oxygen barrier properties. In addition, whereas the unsupported WO films had an immeasurably high water vapor transmission rate (WVTR), the laminate showed values that were finite and surprisingly, in several cases, also lower than that of PLA. Besides being a mechanical support (as evidenced by bending and tensile data) and a shield between the WG and surrounding moisture, the PLA layer also prevented the loss of the glycerol plasticizer from the WG layer. This was observed after the laminate had been aged on an "absorbing" blotting paper for up to 17 weeks. The interlayer adhesion (peel strength) decreased with decreasing glycerol content and increasing WG film molding temperature (130 degrees C instead of 110 degrees C). The latter effect was probably due to a higher protein aggregation, as revealed by infrared spectroscopy. The lamination temperature (110-140 degrees C) did not, however, have a major effect on the final peel strength.
  •  
29.
  • Fernandes, Susana C. M., et al. (författare)
  • Transparent chitosan films reinforced with a high content of nanofibrillated cellulose
  • 2010
  • Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 81:2, s. 394-401
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper reports the preparation and characterization of nanocomposite films based on different chitosan matrices and nanofibrillated cellulose (NFC) for the purpose of improving strength properties. The nanocomposite films were prepared by a simple procedure of casting a water-based suspension of chitosan and NFC, and were characterized by several techniques: namely SEM, X-ray diffraction, visible spectrophotometry, TGA, tensile and dynamic-mechanical analysis. The films obtained were shown to be highly transparent (transmittance varying between 90 and 20% depending on the type of chitosan and NFC content), flexible, displayed better mechanical properties, with a maximum increment on the Young's modulus of 78% and 150% for high molecular weight (HCH) and water-soluble high molecular weight (WSHCH) filled chitosans, respectively; and of 200% and 320% for low molecular weight (LCH) and water-soluble filled (WSLCH) chitosans, respectively. The filled films also showed increased thermal stability, with, for example, an increase in the initial degradation temperature (Td(i)) from 227 degrees C in the unfilled LCH film up to 271 degrees C in filled LCHNFC50% nanocomposite films, and a maximum degradation temperature (Tdi) raising from 304 degrees C to 313 degrees C for the same materials.
  •  
30.
  • Xia, Chen (författare)
  • Development of Natural Mineral Composites for Low-Temperature Solid Oxide Fuel Cells
  • 2018
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Solid oxide fuel cells (SOFCs) have attracted growing attention worldwide because of their high conversion efficiency and low emissions when paired with clean fuel sources. Currently, reducing the temperature of SOFC to a low-temperature (LT) range is a mainstream trend of SOFC research. One effective way to reach this target is to explore alternative electrolytes that can maintain a desirable ionic conductivity at low temperatures. Meanwhile, it has been found that natural minerals hold great potential as functional materials for energy conversion technologies, especially ion-conducting hematite and rare-earth oxides. This thesis presents an experimental investigation of novel composite electrolytes based on two common natural minerals: hematite (LW) (α-Fe2O3) and La0.33Ce0.62Pr0.05O2-δ (LCP) for LT-SOFCs application. Initially, hematite (LW) and LCP are characterized and demonstrated as electrolytes in SOFCs. It is found the hematite ore is a mixture of α-Fe2O3, silica, and calcite, while the LCP mineral is a La/Pr co-doped CeO2. Both hematite (LW) and LCP cells exhibit encouraging performance with power densities of 150-225 and 295-401 mW cm-2 at 500-600 ℃, respectively.Following above findings, two mineral based nanocomposites – hematite-LCP and LCP/K2WO4 – are developed. Electrochemical and electrical studies reveal that the hematite-LCP gains a significantly enhanced conductivity (0.116 S cm-1 at 600 ℃) compared to individual hematite (LW) and LCP. The hematite-LCP based SOFC exhibits attractive power densities of 386-625 mW cm-2 at 450-600 ℃. Further investigation indicates that heterophasic interfacial conduction plays a crucial role in resulting in the good performance. Another composite LCP/K2WO4 is synthesized from LCP and tungstate through a wet-chemical route. The obtained composites exhibit enhanced grain boundary conduction compared to that of LCP. The composition dependence of the electrical conductivity has been studied, indicating that 90 wt% LCP/10 wt% K2WO4 is the optimum proportion with highest ionic conductivity and negligible electronic conductivity. The corresponding SOFC displays the highest power density of 500 mW cm-2 at 550 ℃. Furthermore, by incorporating a semiconductor La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) into LCP and hematite-LCP, respectively, two semiconducting-ionic composites LCP-LSCF and hematite/LCP-LSCF are designed. Crystallographic and morphological characterizations are carried out to gain insight into the material features, and the two composites are applied as the intermediate membrane layer in LT electrolyte-layer free fuel cells (EFFCs). Investigations in terms of conductivity and fuel cell performance reveal that the two composites obtain improved ionic conductivities and cell power outputs compared with those of LCP and hematite-LCP. It is also found the two composites possess mixed ionic and electronic conductivities, which are balanced in the optimal composites. Additionally, stability and Schottky junction of the best-performance EFFC are studied to verify its reliability. 
  •  
31.
  • Xia, Chen (författare)
  • Natural hematite for next-generation solid oxide fuel cells
  • 2015
  • Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 26:6, s. 938-942
  • Tidskriftsartikel (refereegranskat)abstract
    • Natural hematite ore is used as a novel electrolyte material for advanced solid oxide fuel cells (SOFCs). This hematite-based system exhibits a maximum power density of 225 mW cm −2 at 600 °C and reaches 467 mW cm −2 whenthe hematite is mixed with perovskite-structured La 0.6Sr0.4Co0.2Fe0.8O3–δ.These results demonstrate that natural materials for next-generation SOFCs can infl uence the multiutilization of natural resources, thereby affecting the environment and energy sustainability.
  •  
32.
  • van der Wijngaart, Wouter, et al. (författare)
  • Valve-less diffuser fluid micropump
  • 1999
  • Ingår i: Gordon Research Conference 1999, Analytical Chemistry, New Hampshire, USA.
  • Konferensbidrag (refereegranskat)
  •  
33.
  • Brandin, Jan, 1958-, et al. (författare)
  • A review of thermo-chemical conversion of biomass into biofuels-focusing on gas cleaning and up-grading process steps
  • 2017
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • It is not easy to replace fossil-based fuels in the transport sector, however, an appealing solution is to use biomass and waste for the production of renewable alternatives. Thermochemical conversion of biomass for production of synthetic transport fuels by the use of gasification is a promising way to meet these goals.One of the key challenges in using gasification systems with biomass and waste as feedstock is the upgrading of the raw gas produced in the gasifier. These materials replacing oil and coal contain large amounts of demanding impurities, such as alkali, inorganic compounds, sulphur and chlorine compounds. Therefore, as for all multi-step processes, the heat management and hence the total efficiency depend on the different clean-up units. Unfortunately, the available conventional gas filtering units for removing particulates and impurities, and also subsequent catalytic conversion steps have lower optimum working temperatures than the operating temperature in the gasification units.This report focuses on on-going research and development to find new technology solutions and on the key critical technology challenges concerning the purification and upgrading of the raw gas to synthesis gas and the subsequent different fuel synthesis processes, such as hot gas filtration, clever heating solutions and a higher degree of process integration as well as catalysts more resistant towards deactivation. This means that the temperature should be as high as possible for any particular upgrading unit in the refining system. Nevertheless, the temperature and pressure of the cleaned synthesis gas must meet the requirements of the downstream application, i.e. Fischer-Tropsch diesel or methanol.Before using the gas produced in the gasifier a number of impurities needs to be removed. These include particles, tars, sulphur and ammonia. Particles are formed in gasification, irrespective of the type of gasifier design used. A first, coarse separation is performed in one or several cyclone filters at high temperature. Thereafter bag-house filters (e.g. ceramic or textile) maybe used to separate the finer particles. A problem is, however, tar condensation in the filters and there is much work performed on trying to achieve filtration at as high a temperature as possible.The far most stressed technical barriers regarding cleaning of the gases are tars. To remove the tar from the product gas there is a number of alternatives, but most important is that the gasifier is operated at optimal conditions for minimising initial tar formation. In fluid bed and entrained flow gasification a first step may be catalytic tar cracking after particle removal. In fluid bed gasification a catalyst, active in tar cracking, may be added to the fluidising bed to further remove any tar formed in the bed. In this kind of tar removal, natural minerals such as dolomite and olivine, are normally used, or catalysts normally used in hydrocarbon reforming or cracking. The tar can be reformed to CO and hydrogen by thermal reforming as well, when the temperature is increased to 1300ºC and the tar decomposes. Another method for removing tar from the gas is to scrub it by using hot oil (200-300ºC). The tar dissolves in the hot oil, which can be partly regenerated and the remaining tar-containing part is either burned or sent back to the gasifier for regasification.Other important aspects are that the sulphur content of the gas depends on the type of biomass used, the gasification agent used etc., but a level at or above 100 ppm is not unusual. Sulphur levels this high are not acceptable if there are catalytic processes down-stream, or if the emissions of e.g. SO2 are to be kept down. The sulphur may be separated by adsorbing it in ZnO, an irreversible process, or a commercially available reversible adsorbent can be used. There is also the possibility of scrubbing the gas with an amine solution. If a reversible alternative is chosen, elementary sulphur may be produced using the Claus process.Furthermore, the levels of ammonia formed in gasification (3,000 ppm is not uncommon) are normally not considered a problem. When combusting the gas, nitrogen or in the worst case NOx (so-called fuel NOx) is formed; there are, however, indications that there could be problems. Especially when the gasification is followed by down-stream catalytic processes, steam reforming in particular, where the catalyst might suffer from deactivation by long-term exposure to ammonia.The composition of the product gas depends very much on the gasification technology, the gasifying agent and the biomass feedstock. Of particular significance is the choice of gasifying agent, i.e. air, oxygen, water, since it has a huge impact on the composition and quality of the gas, The gasifying agent also affects the choice of cleaning and upgrading processes to syngas and its suitability for different end-use applications as fuels or green chemicals.The ideal upgraded syngas consists of H2 and CO at a correct ratio with very low water and CO2 content allowed. This means that the tars, particulates, alkali salts and inorganic compounds mentioned earlier have to be removed for most of the applications. By using oxygen as the gasifying agent, instead of air, the content of nitrogen may be minimised without expensive nitrogen separation.In summary, there are a number of uses with respect to produced synthesis gas. The major applications will be discussed, starting with the production of hydrogen and then followed by the synthesis of synthetic natural gas, methanol, dimethyl ether, Fischer-Tropsch diesel and higher alcohol synthesis, and describing alternatives combining these methods. The SNG and methanol synthesis are equilibrium constrained, while the synthesis of DME (one-step route), FT diesel and alcohols are not. All of the reactions are exothermal (with the exception of steam reforming of methane and tars) and therefore handling the temperature increase in the reactors is essential. In addition, the synthesis of methanol has to be performed at high pressure (50-100 bar) to be industrially viable.There will be a compromise between the capital cost of the whole cleaning unit and the system efficiency, since solid waste, e.g. ash, sorbents, bed material and waste water all involve handling costs. Consequently, installing very effective catalysts, results in unnecessary costs because of expensive gas cleaning; however the synthesis units further down-stream, especially for Fischer-Tropsch diesel, and DME/methanol will profit from an effective gas cleaning which extends the catalysts life-time. The catalyst materials in the upgrading processes essentially need to be more stable and resistant to different kinds of deactivation.Finally, process intensification is an important development throughout chemical industries, which includes simultaneous integration of both synthesis steps and separation, other examples are advanced heat exchangers with heat integration in order to increase the heat transfer rates. Another example is to combine exothermic and endothermic reactions to support reforming reactions by using the intrinsic energy content. For cost-effective solutions and efficient application, new solutions for cleaning and up-grading of the gases are necessary.
  •  
34.
  • Halvarsson, Sören, 1956- (författare)
  • Manufacture of straw MDF and fibreboards
  • 2010
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The purpose of this thesis was to develop an economical, sustainable, and environmentally friendly straw Medium Density Fibreboard (MDF) process, capable of full-scale manufacturing and to produce MDF of requested quality. The investigated straw was based on wheat (Triticum aestivum L.) and rice (Oryzae sativa L.). In this thesis three different methods were taken for manufacture of straw MDF; (A) wheat-straw fibre was blowline blended with melamine-modified urea-formaldehyde (MUF), (B) rice-straw fibre was mixed with methylene diphenyl diisocyanate (MDI) in a resin drum-blender, and (C) wheat-straw fibre was activated in the blowline by the addition of Fenton’s reagent (H2O2/Fe2+) for production of non-resin MDF panels.  The MUF/wheat straw MDF panels were approved according to the requirements of the EN standard for MDF (EN 622-5, 2006). The MDI/rice-straw MDF panels were approved according to requirements of the standard for MDF of the American National Standard Institute (ANSI A208.2-2002). The non-resin wheat-straw panels showed mediocre MDF panel properties and were not approved according to the requirements in the MDF standard. The dry process for wood-based MDF was modified for production of straw MDF. The straw MDF process was divided into seven main process steps. 1.       Size-reduction (hammer-milling) and screening of straw 2.       Wetting and heating of straw 3.       Defibration 4.       Resination of straw fibre 5.       Mat forming 6.       Pre-pressing 7.       Hot-pressing       The primary results were that the straw MDF process was capable of providing satisfactory straw MDF panels based on different types of straw species and adhesives. Moreover, the straw MDF process was performed in pilot-plant scale and demonstrated as a suitable method for producing straw MDF from straw bales to finished straw MDF panels. In the environmental perspective the agricultural straw-waste is a suitable source for producing MDF to avoid open field burning and to capture carbon dioxide (CO2), the biological sink for extended time into MDF panels, instead of converting straw directly into bio energy or applying straw fibre a few times as recycled paper. Additionally, the straw MDF panels can be recycled or converted to energy after utilization. A relationship between water retention value (WRV) of resinated straw fibres, the thickness swelling of corresponding straw MDF panels, and the amount of applied adhesive was determined. WRV of the straw fibre increased and the TS of straw MDF declined as a function of the resin content. The empirical models developed were of acceptable significance and the R2 values were 0.69 (WRV) and 0.75 (TS), respectively. Reduced thickness swelling of MDF as the resin content is increased is well-known. The increase of WRV as a function of added polymers is not completely established within the science of fibre swelling. Fortunately, more fundamental research can be initiated and likely a simple method for prediction of thickness swelling of MDF by analysis of the dried and resinated MDF fibres is possible.
  •  
35.
  • Hosseini, Seyedehsan, 1994 (författare)
  • Additive-Driven Improvements in Interfacial Properties and Processing of TMP-Polymer Composites
  • 2023
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Efforts to address environmental concerns have resulted in new regulations designed to plan the reduction of plastic and synthetic polymer usage, necessitating the search for sustainable natural alternatives with comparable cost-effectiveness and mechanical performance. Thermomechanical pulp (TMP) fibres are one of the most affordable natural fibres that have no chemical refining in production, production have a high yield of 90-98% and TMP fibres have been demonstrated to improve the mechanical characteristics (strength, stiffness and toughness) of wood-polymer composites (WPCs) compared to the pure polymer. The integration of TMP fibres with non-polar synthetic polymers remains a challenge due to surface polarity differences. This PhD thesis aims to ease the processing of TMP fibre composites through the incorporation of additives. The hypothesis posits that incorporating magnesium stearate (MgSt), molybdenum disulfide (MoS2) and alkyl ketene dimer (AKD) as additives in TMP composites will enhance interfacial properties, resulting in improved processability and flow behaviour at high temperatures. MoS2 is known for its interaction with lignin, which exists in TMP and MgSt is recognised for its ability to improve flow in pharmaceutical processing when combined with cellulose, also a component of TMP. AKD modifies the hydrophilic properties of lignocellulosic surfaces. The experimental work explores the effect of these additives on the properties of TMP composites of ethylene acrylic acid copolymer (EAA) and polypropylene (PP) matrices. The dynamic mechanical analysis (DMA) and mechanical analysis results reveal that MoS2 exhibits superior interaction with TMP fibres, yielding enhanced interfacial properties compared to MgSt in between EAA and TMP fibres. Rheological studies elucidate the transition from a fluid-like state to a network-like structure upon the incorporation of TMP into the PP matrix. The incorporation of AKD with C18 reduces the viscosity of TMP-PP composites and PP itself, and, as determined through theoretical Hansen solubility parameter (HSP) calculations, increases compatibility between cellulose in TMP fibres and PP. The addition of AKD influences both the colour (lighter) and shape (smoother surface) of the extrudate filaments in the TMP-PP composites, indicative of improved processing. In addition, frictional analysis demonstrates the reduction of the coefficient of friction (COF) between metal and TMP fibre by MgSt and AKD treatments.
  •  
36.
  • Stedt, Kristoffer, 1991, et al. (författare)
  • Post-harvest cultivation with seafood process waters improves protein levels of Ulva fenestrata while retaining important food sensory attributes
  • 2022
  • Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745.
  • Tidskriftsartikel (refereegranskat)abstract
    • Seaweed aquaculture can provide the growing human population with a sustainable source of proteins. Sea-based cultivation is an effective method for farming seaweeds on a large scale and can yield high biomass output. However, the quality and biochemical composition of the biomass is seasonally dependent, which limits the harvests to certain periods of the year. Here we show the possibility to extend the sea-based cultivation season of Ulva fenestrata when aiming for high protein levels, by post-harvest treatment in herring production process waters. We harvested U. fenestrata at an optimal period in terms of yield, but suboptimal in terms of protein content. We then cultivated the seaweed in onshore tank systems with the nutrient-rich process waters for 14 days. We monitored biomass yield, crude protein content, amino acid composition, and content of the health concerning metals arsenic, mercury, lead, and cadmium, as well as the sensory properties of the dried biomass. After cultivation in the process waters, biomass yields were 30 - 40% higher (210 – 230 g fresh weight) compared to in seawater (160 g fresh weight). Also, the crude protein and amino acid content increased three to five times in the process waters, reaching 12 - 17 and 15 – 21% dry weight, respectively. The protein enriched biomass followed food graded standards for heavy metal content, and consumption of the biomass does not exceed health based reference points. Additionally, no sensory attributes regarded as negative were found. This rapid, post-harvest treatment can help extend the cultivation season of sea-based seaweed farms, maximizing their output of sustainable proteins.
  •  
37.
  • Steinhagen, Sophie, et al. (författare)
  • Harvest time can affect the optimal yield and quality of sea lettuce (Ulva fenestrata) in a sustainable sea-based cultivation : Seasonal Cultivation of Ulva fenestrata
  • 2022
  • Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 9
  • Tidskriftsartikel (refereegranskat)abstract
    • Seaweed biomass is a renewable resource with multiple applications. Sea-based cultivation of seaweeds can provide high biomass yields, low construction, operation, and maintenance costs and could offer an environmentally and economically sustainable alternative to land-based cultivations. The biochemical profile of sea-grown biomass depends on seasonal variation in environmental factors, and the optimization of harvest time is important for the quality of the produced biomass. To identify optimal harvest times of Swedish sea-based cultivated sea lettuce (Ulva fenestrata), this study monitored biomass yield, morphology, chemical composition, fertility, and biofouling at five different harvesting times in April - June 2020. The highest biomass yields (approx. 1.2 kg fw [m rope]-1) were observed in late spring (May). The number and size of holes in the thalli and the amount of fertile and fouled tissue increased with prolonged growth season, which together led to a significant decline in both biomass yield and quality during summer (June). Early spring (April) conditions were optimal for obtaining high fatty acid, protein, biochar, phenolic, and pigment contents in the biomass, whereas carbohydrate and ash content, as well as essential and non-essential elements, increased later in the growth season. Our study results show that the optimal harvest time of sea-based cultivated U. fenestrata depends on the downstream application of the biomass and must be carefully selected to balance yield, quality, and desired biochemical contents to maximize the output of future sea-based algal cultivations in the European Northern Hemisphere.
  •  
38.
  •  
39.
  • Vera, C. M., et al. (författare)
  • A preliminary study on the selectivity of linear polynuclear aromatic hydrocarbons in SFC using phenyl-type stationary phases
  • 2015
  • Ingår i: Microchemical journal (Print). - : Elsevier. - 0026-265X .- 1095-9149. ; 121, s. 136-140
  • Tidskriftsartikel (refereegranskat)abstract
    • The retention behaviour of a homologous series of polyaromatic hydrocarbons was evaluated on two phenyl-type stationary phases in reversed phase supercritical fluid chromatography (SFC). These phases were the Synergi polar-RP phase and the Cosmosil 5PBB phase, both of which are polar end-capped and incorporate an ether in a propyl chain that tethers the phenyl ring to the silica surface. The Cosmosil 5PBB phase also has five bromine atoms on the phenyl ring. The retention capacity of the Cosmosil column was substantially greater than the Synergi column. However, selectivity on the Cosmosil column was effectively independent of the acetonitrile modifier composition in the CO2 mobile phase, whereas, selectivity on the Synergi column was greatly affected by the acetonitrile modifier in the CO2 mobile phase. The results from this study showed that selectivity and retention studies in HPLC cannot be used to predict selectivity and retention behaviour in SFC. (C) 2015 Elsevier B.V. All rights reserved.
  •  
40.
  • Land, Cecilia (författare)
  • Laboratory method for the study of moisture-induced waviness in paper
  • 2004
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Paper that is subjected to moisture undergoes dimensional changes. It expands during moistening and shrinks during drying. When the paper is under tension between rollers, the effects are complex since shrinkage and expansion are restricted in the width direction. Waves can then appear on the paper web. This can be a problem in heatset web offset printing. The problem is known as waviness or fluting. The printed papers exhibit a wavy shape, which is visually disturbing due to light reflections which create glossy streaks. The aim of the work described in this thesis was to develop a method suitable for studying the moisture- and tension-induced waviness. Experiments were carried out on a laboratory scale to study how such waves develop during moistening and drying. The experimental setup was based on a modified tensile tester. A CCD camera and image analysis based on the STFI-OptiTopo technique was used to characterise the waviness. Moistening and drying were achieved by changing the surrounding air humidity. The method was used to study the effect of moisture uptake by the paper, and to evaluate the effect of tension on the waviness. It was found that increasing moisture resulted in a higher waviness amplitude, but that the web tension controlled the wavelength of the waviness. A high tension gave rise to a shorter wavelength. The measured wavelength was compared with a previously suggested model and the predicted wavelength was about twice as high as the measured wavelength.
  •  
41.
  • Zhou, Ming, et al. (författare)
  • Oligoamine ionic liquids supported on mesoporous microspheres for CO2 separation with good sorption kinetics and low cost
  • 2020
  • Ingår i: Journal of CO2 Utilization. - : Elsevier. - 2212-9820 .- 2212-9839. ; 39
  • Tidskriftsartikel (refereegranskat)abstract
    • Ionic liquids display good CO2 absorption capacity but poor absorption kinetics and high costs. In the present work, we show that these problems can be solved by impregnating the new low cost ionic liquid pentaethylenehexammonium chloride [PEHA][Cl] and the corresponding amine precursor on a low cost mesoporous microsphere support. Nitrogen adsorption/ desorption, high-resolution SEM and thermogravimetric analysis were employed to analyze the structural and thermal properties of the prepared sorbents. The CO2 adsorption and desorption performance was studied by column experiments and mathematical models were fitted to the data. The results showed that sorbents displayed excellent sorption kinetics and capacity, comparable to the best reports in the literature. In addition, the sorbents could be regenerated and displayed high thermal stability. Finally, the costs of the sorbents developed in the present work is much lower than previously reported sorbents. Therefore this novel supported IL system could be promising for industrial CO2 removal and recovery applications.
  •  
42.
  •  
43.
  • Malkoch, Michael, et al. (författare)
  • Synthesis and characterization of 2,2-bis(methylol)propionic acid dendrimers with different cores and terminal groups
  • 2004
  • Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 42:7, s. 1758-1767
  • Tidskriftsartikel (refereegranskat)abstract
    • Three sets of aliphatic polyester dendrimers based on 2,2-bis(methylol)propionic acid (bis-MPA) were synthesized. Two of the sets had benzylidene terminal groups and either a trimethylolpropane or triphenolic core moiety. The last set had acetonide terminal groups and a triphenolic core moiety. Benzylidene-[G#1]-anhydride and acetonide-[G#1] -anhydride were used as the reactive building blocks in the construction of all dendrimers. The large excess of building blocks used in the coupling reactions initially resulted in considerable material loss. This waste was eliminated through the development of a recycling method. H-1 and C-13 NMR and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) analysis were used to verify the purity of all compounds. Size exclusion chromatography (SEC) was used, as well as MALDI-TOF, for molecular weight determinations. The SEC measurements were conducted with a universal calibration method and an online right-angle laser light scattering detector. Measured dendrimer molecular weights were close to their theoretical molar masses. Observations were also made of the hydrodynamic radius and intrinsic viscosity for the different dendrimers.
  •  
44.
  • Deshpande, Raghu, 1979- (författare)
  • The initial phase of the sodium bisulfite pulping of softwood dissolving pulp
  • 2015
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The sulfite pulping process is today practised in only a small number of pulp mills around the globe and the number of sulfite mills that use sodium as the base (cation) is less than five. However, due to the increasing interest in the wood based biorefinery concept, the benefits of sulfite pulping and especially the sodium based variety, has recently gained a lot of interest. It was therefore considered to be of high importance to further study the sodium based sulfite process to investigate if its benefits could be better utilized in the future in the production of dissolving pulps. Of specific interest was to investigate how the pulping conditions in the initial part of the cook (≥ 60 % pulp yield) should be performed in the best way.Thus, this thesis is focused on the initial phase of single stage sodium bisulfite cooking of either 100 % spruce or 100 % pine wood chips. The cooking experiments were carried out with either a lab prepared or a mill prepared cooking acid and the temperature and cooking time were varied. Activation energies for different wood components were investigated as well as side reactions concerning the formation of thiosulfate and sulfate.
  •  
45.
  • Endrodi, Balázs, et al. (författare)
  • Suppressed oxygen evolution during chlorateformation from hypochlorite in the presenceof chromium(VI)
  • 2019
  • Ingår i: Journal of chemical technology and biotechnology (1986). - : Wiley. - 0268-2575 .- 1097-4660. ; 94:5, s. 1520-1527
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Chromium(VI) is a crucial electrolyte component in industrial chlorate production. Due to its toxicity, iturgently needs to be abandoned and its functions fulfilled by new solutions. In the industrial production of sodium chlorate,homogeneous decomposition of the hypochlorite intermediate to chlorate is a key step. As a competing loss reaction,hypochlorite can decompose to oxygen. How chromium(VI) affects these reactions is not well understood.RESULTS: This work shows, for the first time, that chromium(VI) selectively accelerates the chlorate formation from hypochloriteboth in dilute and concentrated, industrially relevant solutions. The effect of the ionic strength and the specific contributionof different electrolyte components were systematically studied. By simultaneously measuring the concentration decayof hypochlorite (UV–vis spectroscopy) and the oxygen formation (mass spectrometry), both the rate and the selectivity of thereactions were evaluated.CONCLUSION: In the presence of chromium(VI) the hypochlorite decomposition is described by the sum of an uncatalyzedand a parallel catalyzed reaction, where oxygen only forms in the uncatalyzed reaction. When removing chromium(VI),the homogeneous oxygen formation increases, causing economic and safety concerns. The need for a catalyst selectivefor chlorate formation is emphasized.
  •  
46.
  • H. Moud, Pouya (författare)
  • Catalytic Conversion of Undesired Organic Compounds to Syngas in Biomass Gasification and Pyrolysis Applications
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Reliable energy supply is a major concern and crucial for development of the global society. To address the dependency on fossil fuel and the negative effects of this reliance on climate, there is a need for a transition to cleaner sources. An attractive solution for replacing fossil-based products is renewable substitutes produced from biomass. Gasification and pyrolysis are two promising thermochemical conversion technologies, facing challenges before large-scale commercialization becomes viable. In case of biomass gasification, tar is often and undesired by-product. An attractive option to convert tar into syngas is nickel-based catalytic steam reforming (SR). For biomass pyrolysis, catalytic SR is in early stages of investigation as a feasible option for bio-crude conversion to syngas.The focus of the thesis is partly dedicated to describe research aimed at increasing the knowledge around tar reforming mechanisms and effect of biomass-derived impurities on Ni-based tar reforming catalyst downstream of gasifiers. The work focuses on better understanding of gas-phase alkali interaction with Ni-based catalyst surface under realistic conditions. A methodology was successfully developed to enable controlled investigation of the combined sulfur (S) and potassium (K) interaction with the catalyst. The most striking result was that K appears to lower the sulfur coverage and increases methane and tar reforming activity. Additionally, the results obtained in the atomistic investigations are discussed in terms of naphthalene adsorption, dehydrogenation and carbon passivation of nickel.Furthermore, the thesis describes research performed on pyrolysis gas pre-conditioning at a small-industrial scale, using an iron-based catalyst. Findings showed that Fe-based materials are potential candidates for application in a pyrolysis gas pre-conditioning step before further treatment or use, and a way for generating a hydrogen-enriched gas without the need for bio-crude condensation.
  •  
47.
  • Kumar, Vikash, et al. (författare)
  • Poplar carbohydrate-active enzymes : whole-genome annotation and functional analyses based on RNA expression data
  • 2019
  • Ingår i: The Plant Journal. - Hoboken : John Wiley & Sons. - 0960-7412 .- 1365-313X. ; 99:4, s. 589-609
  • Tidskriftsartikel (refereegranskat)abstract
    • Carbohydrate-active enzymes (CAZymes) catalyze the formation and modification of glycoproteins, glycolipids, starch, secondary metabolites and cell wall biopolymers. They are key enzymes for the biosynthesis of food and renewable biomass. Woody biomass is particularly important for long-term carbon storage and as an abundant renewable natural resource for many industrial applications. This study presents a re-annotation of CAZyme genes in the current Populus trichocarpa genome assembly and in silico functional characterization, based on high-resolution RNA-Seq data sets. Altogether, 1914 CAZyme and expansin genes were annotated in 101 families. About 1797 of these genes were found expressed in at least one Populus organ. We identified genes involved in the biosynthesis of different cell wall polymers and their paralogs. Whereas similar families exist in poplar and Arabidopsis thaliana (with the exception of CBM13 found only in poplar), a few families had significantly different copy numbers between the two species. To identify the transcriptional coordination and functional relatedness within the CAZymes and other proteins, we performed co-expression network analysis of CAZymes in wood-forming tissues using the AspWood database () for Populus tremula. This provided an overview of the transcriptional changes in CAZymes during the transition from primary to secondary wall formation, and the clustering of transcripts into potential regulons. Candidate enzymes involved in the biosynthesis of polysaccharides were identified along with many tissue-specific uncharacterized genes and transcription factors. These collections offer a rich source of targets for the modification of secondary cell wall biosynthesis and other developmental processes in woody plants.
  •  
48.
  • Liu, Longcheng, et al. (författare)
  • Solute transport along a single fracture in a porous rock : a simple analytical solution and its extension for modeling velocity dispersion
  • 2017
  • Ingår i: Hydrogeology Journal. - : Springer Berlin/Heidelberg. - 1431-2174 .- 1435-0157.
  • Tidskriftsartikel (refereegranskat)abstract
    • A simple and robust solution is developed for the problem of solute transport along a single fracture in a porous rock. The solution is referred to as the solution to the single-flow-path model and takes the form of a convolution of two functions. The first function is the probability density function of residence-time distribution of a conservative solute in the fracture-only system as if the rock matrix is impermeable. The second function is the response of the fracture-matrix system to the input source when Fickian-type dispersion is completely neglected; thus, the effects of Fickian-type dispersion and matrix diffusion have been decoupled. It is also found that the solution can be understood in a way in line with the concept of velocity dispersion in fractured rocks. The solution is therefore extended into more general cases to also account for velocity variation between the channels. This leads to a development of the multi-channel model followed by detailed statistical descriptions of channel properties and sensitivity analysis of the model upon changes in the model key parameters. The simulation results obtained by the multi-channel model in this study fairly well agree with what is often observed in field experiments—i.e. the unchanged Peclet number with distance, which cannot be predicted by the classical advection-dispersion equation. In light of the findings from the aforementioned analysis, it is suggested that forced-gradient experiments can result in considerably different estimates of dispersivity compared to what can be found in natural-gradient systems for typical channel widths.
  •  
49.
  • Paulraj, Alagar Raj, 1989-, et al. (författare)
  • NiFeOx as a Bifunctional Electrocatalyst for Oxygen Reduction (OR) and Evolution (OE) Reaction in Alkaline Media
  • 2018
  • Ingår i: Catalysts. - : MDPI AG. - 2073-4344. ; 8:8
  • Tidskriftsartikel (refereegranskat)abstract
    • This article reports the two-step synthesis of NiFeOx nanomaterials and their characterization and bifunctional electrocatalytic activity measurements in alkaline electrolyte for metal-air batteries. The samples were mostly in layered double hydroxide at the initial temperature, but upon heat treatment, they were converted to NiFe2O4 phases. The electrochemical behaviour of the different samples was studied by linear sweep voltammetry and cyclic voltammetry on the glassy carbon electrode. The OER catalyst activity was observed for low mass loadings (0.125 mg cm−2), whereas high catalyst loading exhibited the best performance on the ORR side. The sample heat-treated at 250 °C delivered the highest bi-functional oxygen evolution and reduction reaction activity (OER/ORR) thanks to its thin-holey nanosheet-like structure with higher nickel oxidation state at 250 °C. This work further helps to develop low-cost electrocatalyst development for metal-air batteries
  •  
50.
  • Shahkarami, Pirouz, 1986-, et al. (författare)
  • Channel Network Concept — an Integrated Approach to Visualize Solute Transport in Fractured Rocks
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • The advection-dispersion equation, ADE, has commonly been used to visualize solute transport in fractured rock. However, there is one key question that has to be addressed before the mathematical form of the so-called Fickian dispersion that underlies the ADE takes on physical meaning in fractures. What is the travel distance, or travel time, required before the Fickian condition is met and the ADE becomes physically reasonable? A simple theory is presented in this study to address this question in tapered channels. It is shown that spreading of solute under forced-gradient flow conditions is mostly dominated by advective mechanisms, though the ADE might be valid in the channels under natural flow conditions. This implies that the use of the ADE and macro dispersion coefficient might be misleading when applied to interpret field tracer experiment results. Furthermore, several concerns are raised in this paper with regard to utilizing the concept of field-scale matrix diffusion coefficient in fractured rocks. The concerns are mainly directed toward the uncertainties and potential bias involved in finding the continuum model parameters.In light of the findings of this study and empirical evidences, it is suggested that it is feasible and more realistic to describe flow and solute transport in fractured rocks as taking place in three-dimensional networks of channels, as embodied in the channel network concept, CN-concept. It is argued that this conceptualization provides a convenient framework to capture the impacts of spatial heterogeneities in fractured rocks and can accommodate the physical mechanisms underlying the behavior of solute transport in such porous media. All these issues are discussed in this paper in relation to analyzing and predicting actual tracer tests in fractured crystalline rocks.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-50 av 12389
Typ av publikation
tidskriftsartikel (7592)
konferensbidrag (2311)
doktorsavhandling (877)
licentiatavhandling (525)
annan publikation (275)
rapport (248)
visa fler...
bokkapitel (227)
forskningsöversikt (213)
patent (67)
bok (24)
samlingsverk (redaktörskap) (18)
proceedings (redaktörskap) (12)
konstnärligt arbete (5)
visa färre...
Typ av innehåll
refereegranskat (9277)
övrigt vetenskapligt/konstnärligt (2852)
populärvet., debatt m.m. (257)
Författare/redaktör
Skoglundh, Magnus, 1 ... (357)
Berntsson, Thore, 19 ... (236)
Hedlund, Jonas (218)
Olsson, Louise, 1974 (183)
Zacchi, Guido (161)
Jannasch, Patric (154)
visa fler...
Hakkarainen, Minna (148)
Järnström, Lars (139)
Mattisson, Tobias, 1 ... (132)
Lyngfelt, Anders, 19 ... (126)
Jönsson, Ann-Sofi (116)
Rasmuson, Anders, 19 ... (116)
Lindbergh, Göran (116)
Theliander, Hans, 19 ... (114)
Carlsson, Per-Anders ... (113)
Albertsson, Ann-Chri ... (112)
Germgård, Ulf (111)
Leion, Henrik, 1976 (108)
Lipnizki, Frank (107)
Harvey, Simon, 1965 (106)
Fridell, Erik, 1963 (102)
Hulteberg, Christian (101)
Ström, Henrik, 1981 (101)
Creaser, Derek, 1966 (100)
Vamling, Lennart, 19 ... (98)
Galbe, Mats (97)
Hedenqvist, Mikael S ... (94)
Ek, Monica (91)
Andersson, Arne (88)
Sterte, Johan (87)
Stenström, Stig (86)
Thunman, Henrik, 197 ... (86)
Lidén, Gunnar (84)
Karlsson, Sigbritt (82)
Grahn, Mattias (82)
Holmberg, Krister, 1 ... (80)
Nilsson, Bernt (79)
Wågberg, Lars (79)
Rasmuson, Åke C. (78)
Palmqvist, Anders, 1 ... (78)
Järnström, Lars, 195 ... (78)
Martinez, Joaquin (76)
Broström, Markus (75)
Johnsson, Filip, 196 ... (74)
Andersson, Bengt, 19 ... (71)
Wallberg, Ola (70)
Rydén, Magnus, 1975 (69)
Sverdrup, Harald (69)
Karlsson, Hans (66)
Härelind Ingelsten, ... (66)
visa färre...
Lärosäte
Chalmers tekniska högskola (4675)
Kungliga Tekniska Högskolan (2973)
Lunds universitet (1931)
Karlstads universitet (857)
Luleå tekniska universitet (705)
RISE (544)
visa fler...
Mittuniversitetet (508)
Umeå universitet (383)
Linköpings universitet (295)
Uppsala universitet (268)
Göteborgs universitet (222)
Högskolan i Borås (208)
Sveriges Lantbruksuniversitet (208)
Stockholms universitet (180)
Linnéuniversitetet (151)
Mälardalens universitet (102)
Högskolan i Skövde (29)
Karolinska Institutet (26)
Högskolan Dalarna (23)
Malmö universitet (16)
Örebro universitet (14)
Jönköping University (13)
IVL Svenska Miljöinstitutet (13)
Högskolan Kristianstad (12)
Högskolan i Halmstad (11)
Högskolan i Gävle (11)
Högskolan Väst (9)
Blekinge Tekniska Högskola (3)
Riksantikvarieämbetet (2)
Naturvårdsverket (1)
VTI - Statens väg- och transportforskningsinstitut (1)
Röda Korsets Högskola (1)
visa färre...
Språk
Engelska (12113)
Svenska (248)
Spanska (16)
Tyska (5)
Danska (2)
Odefinierat språk (2)
visa fler...
Franska (1)
Norska (1)
Finska (1)
visa färre...
Forskningsämne (UKÄ/SCB)
Teknik (12387)
Naturvetenskap (3045)
Lantbruksvetenskap (244)
Medicin och hälsovetenskap (131)
Samhällsvetenskap (76)
Humaniora (39)

År

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy