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Sökning: LAR1:cth > Högskolan i Borås > (2010-2013)

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1.
  • Abtahi, Z., et al. (författare)
  • Ethanol production by Mucor indicus at high glucose and ethanol concentrations
  • 2010
  • Ingår i: Minerva Biotecnologica. - : Edizioni Minerva Medica. - 1120-4826 .- 1827-160X. ; 22:3-4, s. 83-89
  • Tidskriftsartikel (refereegranskat)abstract
    • Mucor indicus was cultivated under aerobic and anaerobic conditions to study its tolerance against high concentration of glucose up to 350 g/L and ethanol up to 120 g/L present in the medium. The fungus could grow well even in 350 g/L glucose and produce ethanol, but it was able to assimilate the entire glucose when its concentration was less than 200 g/L. On the other hand, M. indicus produced ethanol as the main product with yield and concentration up to 0.45 g/g and 73 g/L, respectively, while glycerol, its only major byproduct, was produced up to 24 g/L. However, the fungus was not so tolerant against exogenously added ethanol, and it could not grow with more than 40 g/L added ethanol to the culture. Under aerobic conditions, M. indicus displayed different morphology, switching from long filamentous to yeast-like growth forms by increasing initial glucose concentration. This implies that yeast-like growth can be induced by growing M. indicus at high glucose concentration. Under anaerobic conditions, only one yeast-like form was observed.
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2.
  • Adekunle, Kayode (författare)
  • Bio-based Composites from Soybean Oil Thermosets and Natural Fibers
  • 2011
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In order to reduce over-dependency on fossil fuels and to create an environment that is free of non-degradable plastics, and most importantly to reduce greenhouse gas emission, bio-based products are being developed from renewable resources through intense research to substitute conventional petrochemical-based plastics with renewable alternatives and to replace synthetic fibers with natural fibers. Many authors have done quite a lot of work on synthesizing polymers from renewable origin. Polylactic acid (PLA) has been developed and characterized, and it was found that it has enormous potential and can serve as an alternative to conventional thermoplastics in many applications. Modification of the plant oil triglycerides has been discussed by many authors, and research is still going on in this area. The challenge is how to make these renewable polymers more competitive in the market, and if possible to make them 100% bio-based. There is also a major disadvantage to using a bio-based polymer from plant oils because of the high viscosity, which makes impregnation of fibers difficult. Although natural fibers are hydrophilic in nature, the problem of compatibility with the hydrophobic matrix must be solved; however, the viscosity of the bio-based resin from plant oils will complicate the situation even more. This is why many authors have reported blending of the renewable thermoset resin with styrene. In the process of solving one problem, i.e reducing the viscosity of the renewable thermoset resin by blending with reactive diluents such as styrene, another problem which we intended to solve at the initial stage is invariably being created by using a volatile organic solvent like styrene. The solution to this cycle of problems is to synthesize a thermoset resin from plant oils which will have lower viscosity, and at the same time have higher levels of functionality. This will increase the crosslinking density, and they can be cured at room temperature or relatively low temperature. In view of the above considerations, the work included in this thesis has provided a reasonable solution to the compounded problems highlighted above. Three types of bio-based thermoset resins were synthesized and characterized using NMR, DSC, TGA, and FT-IR, and their processability was studied. The three resins were subsequently reinforced with natural fibers (woven and non-woven), glass fibers, and Lyocell fiber and the resulting natural fiber composites were characterized by mechanical, dynamic mechanical, impact, and SEM analyses. These composites can be used extensively in the automotive industry, particularly for the interior components, and also in the construction and furniture industries. Methacrylated soybean oil (MSO), methacrylic anhydride-modified soybean oil (MMSO), and acetic anhydride-modified soybean oil (AMSO) were found to be suitable for manufacture of composites because of their lower viscosity. The MMSO and MSO resins were found to be promising materials because composites manufactured by using them as a matrix showed very good mechanical properties. The MMSO resin can completely wet a fiber without the addition of styrene. It has the highest number of methacrylates per triglyceride and high crosslink density.
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3.
  • Adekunle, Kayode, 1970, et al. (författare)
  • Mechanical properties of natural fiber hybrid composites based on renewable thermoset resins derived from soybean oil, for use in technical applications
  • 2012
  • Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 124:6, s. 4530-4541
  • Tidskriftsartikel (refereegranskat)abstract
    • Natural fiber composites are known to have lower mechanical properties than glass or carbon fiber reinforced composites. The hybrid natural fiber composites prepared in this study have relatively good mechanical properties. Different combinations of woven and non-woven flax fibers were used. The stacking sequence of the fibers was in different orientations, such as 0 degrees, +45 degrees, and 90 degrees. The composites manufactured had good mechanical properties. A tensile strength of about 119 MPa and Young's modulus of about 14 GPa was achieved, with flexural strength and modulus of about 201 MPa and 24 GPa, respectively. For the purposes of comparison, composites were made with a combination of woven fabrics and glass fibers. One ply of a glass fiber mat was sandwiched in the mid-plane and this increased the tensile strength considerably to 168 MPa. Dynamic mechanical analysis was performed in order to determine the storage and loss modulus and the glass transition temperature of the composites. Microstructural analysis was done with scanning electron microscopy.
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4.
  • Anderson, Dan, 1943, et al. (författare)
  • Galerkin approach to approximate solutions of some nonlinear oscillator equations
  • 2010
  • Ingår i: American Journal of Physics. - : American Association of Physics Teachers (AAPT). - 0002-9505 .- 1943-2909. ; 78:9, s. 920-924
  • Tidskriftsartikel (refereegranskat)abstract
    • An analysis based on the Galerkin method is given of some nonlinear oscillator equations that have been analyzed by several other methods, including harmonic balance and direct variational methods. The present analysis is shown to provide simple yet accurate approximate solutions of these nonlinear equations and illustrates the usefulness and the power of the Galerkin method. (C) 2010 American Association of Physics Teachers. [DOI: 10.1119/1.3429974]
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5.
  • Bashir, Tariq (författare)
  • Conjugated Polymer-based Conductive Fibers for Smart Textile Applications
  • 2013
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Electrically conductive or electro-active fibers are the key components of smart and interactive textiles, which could be used in medical, sports, energy, and military applications in the near future. The functionalization of high-performance textile yarns/fibers with conjugated polymers can produce conductive fibers with better electro-mechanical properties, which is difficult with commonly used spinning techniques. In this thesis work, textile-based conductive yarns/fibers were prepared by coating viscose and polyester (PET) yarns with the conjugated polymer PEDOT. For coating purposes, an efficient technique called chemical vapor deposition (CVD) was used, which is a solventless technique and can produce PEDOT polymer layers with high conductivity values. The polymerization of EDOT monomer vapors and coating of oxidant (FeCl3 or FepTS) enriched viscose and PET yarns took place simultaneously. The PEDOT-coated viscose and polyester yarns showed relatively high conductivity values, which could be sufficient for many electronic applications. The polymerization process and the quality of PEDOT polymer strongly depends on different reaction conditions. In this research work, the impact of most of these reaction parameters on the electrical, mechanical, and thermal properties of PEDOT-coated conductive yarns was considered separately. Under specific reaction conditions, it was found that viscose fibers were successfully coated with PEDOT polymer and showed rather high electrical conductivity (≥ 15 S/cm). However, due to the acid hydrolysis of viscose fibers in FeCl3 solutions, the mechanical properties were drastically reduced. In order to improve the mechanical properties of conductive yarns, a relatively stable and chemical-resistant substrate (PET) was coated with PEDOT polymer. Comparative studies between PEDOT-coated viscose and PET conductive yarns showed that the electrical and mechanical properties were enhanced by changing the substrate material. Later on, PEDOT-coated conductive fibers were treated with silicone elastomer solution and due to the thin silicone layers, the hydrophobic properties, flexibility, and durability of coated yarns was improved. Furthermore, a novel electrical resistance-measuring setup was developed, which can be used not only for fibers but also for fabric structures. The electrical characterization of PEDOT-coated conductive yarns showed that it can be used effectively for sensitive fibers without damaging their surface morphology. Finally, the use of conductive yarns as stretch sensors was evaluated. For this purpose, small rectangular knitted patches of conductive yarns were prepared and then the change in electrical resistance values at different extension percentages (5–50%) was investigated. The constant variations in electrical resistance values at different extension and relaxation cycles for longer periods of time revealed that the conductive yarns produced have the potential to be used as stretch sensors for monitoring of vital signs in medical and sports applications.
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6.
  • Bazooyar, Faranak, 1972, et al. (författare)
  • Molecular Modelling of Cellulose Dissolution
  • 2013
  • Ingår i: Journal of Computational and Theoretical Nanoscience. - : American Scientific Publishers. - 1546-1955 .- 1546-1963. ; 10:11, s. 2639-2646
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work we present computational studies that shed light on the molecular mechanism of the initial stages of cellulose dissolution in saturated steam, which is an important pretreatment step in the conversion of lignocellulose to biofuel. The COMPASS, Dreiding and Universal molecular mechanics force fields and the B3LYP density functional with 6-311G, 6-311++G(d, p) and 6-311++G(2d, 2p) basis sets were used to study systems containing glucose, cellobiose and water. These molecular systems were studied since they are sufficiently small to perform the density functional theory calculations in a tractable time, while also being relevant to the dissolution of cellulose in saturated steam. Comparison of the energies and structures obtained from the three force fields with those obtained from the first principles method showed that the COMPASS force field is preferred to the other two and that this force field gives similar structures obtained from the first principles method. This supports the validity of the COMPASS force field for studying cellulose dissolution in saturated steam, and preliminary simulations were performed using grand canonical Monte Carlo and molecular dynamics simulations of cellulose dissolution in saturated steam at 100 degrees C and 1 bar, 160 degrees C and 6.2 bar, and 250 degrees C and 39.7 bar. The results show that the cellulose crystal dissolves in saturated steam at the higher temperatures and pressures.
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7.
  • Bazooyar, Faranak, 1972, et al. (författare)
  • Validating empirical force fields for molecular-level simulation of cellulose dissolution
  • 2012
  • Ingår i: Computational and Theoretical Chemistry. - : Elsevier BV. - 2210-271X .- 2210-2728. ; 984, s. 119-127
  • Tidskriftsartikel (refereegranskat)abstract
    • The calculations presented here, which include dynamics simulations using molecular mechanics force fields and first principles studies, indicate that the COMPASS force field is preferred over the Dreiding and Universal force fields for studying dissolution of large cellulose structures. The validity of these force fields was assessed by comparing structures and energies of cellobiose, which is the shortest cellulose chain, obtained from the force fields with those obtained from MP2 and DFT methods. In agreement with the first principles methods, COMPASS is the only force field of the three studied here that favors the anti form of cellobiose in the vacuum. This force field was also used to compare changes in energies when hydrating cellobiose with 1-4 water molecules. Although the COMPASS force field does not yield the change from anti to syn minimum energy structure when hydrating with h more than two water molecules - as predicted by OFT - it does predict that the syn conformer is preferred when simulating cellobiose in bulk liquid water and at temperatures relevant to cellulose dissolution. This indicates that the COMPASS force field yields valid structures of cellulose under these conditions. Simulations based on the COMPASS force field show that, due to entropic effects, the syn form of cellobiose is energetically preferred at elevated temperature, both in vacuum and in bulk water. This is also in agreement with DFT calculations.
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8.
  • Bengtsson, Anders, 1988, et al. (författare)
  • Counterterms in gravity in the light-front formulation and a D=2 conformal-like symmetry in gravity
  • 2013
  • Ingår i: Journal of High Energy Physics. - : Springer Science and Business Media LLC. - 1029-8479 .- 1126-6708. ; 58:5-6, s. 485-501
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper we discuss gravity in the light-front formulation (light-cone gauge) and show how possible counterterms arise. We find that Poincare invariance is not enough to find the three-point counterterms uniquely. Higher-spin fields can intrude and mimic three-point higher derivative gravity terms. To select the correct term we have to use the remaining reparametrization invariance that exists after the gauge choice. We finally sketch how the corresponding programme for N = 8 Supergravity should work.
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9.
  • Bengtsson, Magnus, 1973, et al. (författare)
  • Influence of throw and compression ratio on particle shape - A full scale investigation and laboratory tests
  • 2010
  • Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 23:7, s. 549-557
  • Tidskriftsartikel (refereegranskat)abstract
    • The machine parameters of throw and eccentric speed affect the particle shape. Their influence on particle shape is however not fully investigated. Preliminary tests on a full-scale crusher had shown certain trends in regard to the flakiness of the product (Fig. 1). These effects were investigated in detail by means of a series of piston-and-die tests, followed by modelling of the laboratory data. An empirical model of a crusher was developed which links the product size distribution and the shape of the particles to operating parameters. The simulator produced trends which were similar to the full-scale data. The throw and eccentric speed affects the utilised compression acting on the rock/rock-bed. This paper presents a method suitable for characterizing the compressive breakage behaviour of rock materials during form conditioned compression. In this method, size reduction is primarily related to geometric compression. The method provides a complete description of the breakage characteristics of the tested rock material when compressive crushing is employed. The results can be used for modelling and simulation purposes in the design of crushing equipment or crushing plants. A novel approach to optimise form conditioned crushing in order to achieve an acceptable particle size and shape is presented. The paper concludes that inter-particle breakage in combination with high compression ratio is beneficial for the particle shape. The full scale tests support this since an increase in throw improves particle shape for particles subjected to inter-particle breakage. © 2009 Elsevier Ltd. All rights reserved.
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10.
  • Bidgoli, Hossein, et al. (författare)
  • Effect of carboxymethylation conditions on water binding capacity of chitosan-based superabsorbents
  • 2010
  • Ingår i: Carbohydrate Research. - : Elsevier - Pergamon. - 0008-6215 .- 1873-426X. ; 345:18, s. 2683-2689
  • Tidskriftsartikel (refereegranskat)abstract
    • A superabsorbent polymer (SAP) from chitosan was provided via carboxymethylation of chitosan, followed by cross-linking with glutaraldehyde and freeze-drying. This work was focused on an investigation of the effects of monochloroacetic acid (MCAA), sodium hydroxide, and reaction time on preparation of carboxymethylchitosan (CMCS). The CMCS products were characterized using FTIR spectroscopy, and their degrees of substitution (DS) were measured using conductimetry and FTIR analysis. The highest DS value was obtained when the carboxymethylation reaction was carried out using 1.75 g MCAA and 1.75 g NaOH per g of chitosan in 4 h. The water solubilities of the CMCS products at various pHs were also evaluated, and the results indicated a significant impact of the reaction parameters on the solubility of CMCS. The CMCSs with the highest DS value resulted in SAPs having the highest water-binding capacity (WBC). TheWBCof the best SAP measured after 10 minexposure in distilled water, 0.9% NaCl solution, synthetic urine, and artificial blood was 104, 33, 30, and 57 g/g, respectively. The WBC of this SAP at pH 2–9 passed a maximum at pH 6.
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