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Sökning: LAR1:lu > Kungliga Tekniska Högskolan > (2000-2004)

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  • Abrahamsson, M. L. A., et al. (författare)
  • Ruthenium-Manganese Complexes for Artificial Photosynthesis: Factors Controlling Intramolecular Electron Transfer and Excited-State Quenching Reactions
  • 2002
  • Ingår i: Inorganic Chemistry. - The American Chemical Society. - 1520-510X. ; 41:6, s. 1534-1544
  • Tidskriftsartikel (refereegranskat)abstract
    • Continuing our work toward a system mimicking the electron-transfer steps from manganese to P680+ in photosystem II (PS II), we report a series of ruthenium(II)-manganese(II) complexes that display intramolecular electron transfer from manganese(II) to photooxidized ruthenium(III). The electron-transfer rate constant (kET) values span a large range, 1 × 105-2 × 107 s-1, and we have investigated different factors that are responsible for the variation. The reorganization energies determined experimentally ( = 1.5-2.0 eV) are larger than expected for solvent reorganization in complexes of similar size in polar solvents (typically 1.0 eV). This result indicates that the inner reorganization energy is relatively large and, consequently, that at moderate driving force values manganese complexes are not fast donors. Both the type of manganese ligand and the link between the two metals are shown to be of great importance to the electron-transfer rate. In contrast, we show that the quenching of the excited state of the ruthenium(II) moiety by manganese(II) in this series of complexes mainly depends on the distance between the metals. However, by synthetically modifying the sensitizer so that the lowest metal-to-ligand charge transfer state was localized on the nonbridging ruthenium(II) ligands, we could reduce the quenching rate constant in one complex by a factor of 700 without changing the bridging ligand. Still, the manganese(II)-ruthenium(III) electron-transfer rate constant was not reduced. Consequently, the modification resulted in a complex with very favorable properties.
  • Agren, N. D., et al. (författare)
  • First experiments on an evaporative gas turbine pilot power plant: Water circuit chemistry and humidification evaluation
  • 2002
  • Ingår i: Journal of Engineering for Gas Turbines and Power. - American Society of Mechanical Engineers. - 1528-8919. ; 124:1, s. 96-102
  • Tidskriftsartikel (refereegranskat)abstract
    • The evaporative gas turbine (EvGT), also known as the humid air turbine (HAT) cycle, is a novel advanced gas turbine cycle that has attracted considerable interest for the last decade. This high-efficiency cycle shows the potential to be competitive with Diesel engines or combined cycles in small and intermediate scale plants for power production and/or cogeneration. A 0.6 MW natural gas-fired EvGT pilot plant has been constructed by a Swedish national research group in cooperation between universities and industry. The plant is located at the Lund Institute of Technology, Lund, Sweden. The pilot plant uses a humidification tower with metallic packing in which heated water from the flue gas economizer is brought into direct counter current contact with the pressurized air from the compressor This gives an efficient heat recovery and thereby a thermodynamically sound cycle. As the hot sections in high-temperature gas turbines are sensitive to particles and alkali compounds, water quality issues need to be carefully considered. As such, apart from evaluating the thermodynamic and part-load performance characteristics of the plant, and verifying the operation of the high-pressure humidifier, much attention is focused on the water chemistry issues associated with the recovery and reuse of condensate water from the flue gas. A water treatment system has been designed and integrated into the pilot plant. This paper presents the first water quality results from the plant. The experimental results show that the condensate contains low levels of alkali and calcium, around 2 mg/l Sigma(K,Na,Ca), probably originating from the unfiltered compressor intake, About 14 mg/l NO2- +NO3- comes from condensate absorption of flue gas NOx. Some Cu is noted, 16 mg/l, which originates from copper corrosion of the condenser tubes. After CO2 stripping, condensate filtration and a mixed bed ion exchanger the condensate is of suitable quality for reuse as humidification water The need,for large quantities of demineralized water has by manY authors been identified as a drawback for the evaporative cycle. However, by cooling the humid flue gas, the recovery, of condensed water cuts the need of water feed. A self-supporting water circuit can be achieved, with no need for any net addition of water to the system. In the pilot plant, this was achieved by cooling the flue gas to around 35degreesC.
  • Alayon Glazunov, Andres, et al. (författare)
  • On the distribution of relevant radio channel figures in different propagation environments for performance evaluation of WCDMA systems
  • 2001
  • Ingår i: IEEE VTS 53rd Vehicular Technology Conference, VTC 2001 Spring.. - 0-7803-6728-6 ; 1, s. 269-273
  • Konferensbidrag (refereegranskat)abstract
    • A statistical distribution for the number of CDMA RAKE fingers, N T, to be assigned in order to track a given percent of the total received power has been derived. The obtained distribution reveals a strong dependence of NT on the system bandwidth, the median RMS delay spread, its standard deviation and other environment specific parameters. Also, a statistical distribution for the fading width fw, is presented. Some numerical results for both NT and fw are presented as a function of the system bandwidth at different probability levels
  • Alayon Glazunov, Andres (författare)
  • Theoretical analysis of mean effective gain of mobile terminal antennas in Ricean channels
  • 2002
  • Ingår i: 2002 IEEE 56th Vehicular Technology Conference, Proceedings. VTC 2002-Fall.. - 1090-3038. - 0-7803-7467-3 ; 3, s. 1796-1800
  • Konferensbidrag (refereegranskat)abstract
    • The mean effective gain (MEG) for Rice distributed signals impinging at the terminal receiver antenna is presented. Numerical results are presented for three different angular probability distributions of impinging waves. Finally, it is shown that contrary to the Rayleigh channels in Ricean channels there is no inclination angle at which the MEG of the half-wave dipole antenna remains constant regardless the crosspolarization ratio (XPR) of the channel.
  • Algora, A., et al. (författare)
  • Pronounced Shape Change Induced by Quasiparticle Alignment
  • 2000
  • Ingår i: Physical Review C (Nuclear Physics). - American Physical Society. - 0556-2813. ; 61:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Mean lifetimes of high-spin states of Kr-74 have been determined using the Doppler-shift attenuation method. The high-spin states were studied using the Ca-40(Ca-40, alpha 2p) reaction at a beam energy of 160 MeV with the GASP gamma-ray spectrometer. The ground-state band and negative parity side band show the presence of three different configurations in terms of transitional quadrupole deformations. A dramatic shape change was found along the ground-state band after the S-band crossing. The deduced quadrupole deformation changes are well reproduced by cranked Woods-Saxon Strutinsky calculations.
  • Andersson, M., et al. (författare)
  • Size and Structure Characterization of Ethylhydroxyethyl Cellulose by the Combination of Field-Flow Fractionation with Other Techniques. Investigation of Ultralarge Components
  • 2004
  • Ingår i: Biomacromolecules. - The American Chemical Society. - 1526-4602. ; 5:1, s. 97-105
  • Tidskriftsartikel (refereegranskat)abstract
    • Ethylhydroxyethyl cellulose (EHEC) of three different viscosity classes (EHEC I, II, and III) was analyzed by programmed cross-flow asymmetrical flow field-flow fractionation coupled to multiangle light scattering and refractive index detectors to determine their size and molar mass distribution. Two size populations were detected in the two lower viscosity classes, EHEC I and II, one high molar mass and one ultrahigh molar mass (UHM). The two covered molar masses from 104 up to 109 g·mol-1. The highest viscosity class EHEC III was less size-dispersed covering molar masses from 5 × 105 to 5 × 107 g·mol-1. Filtering of the EHEC II solution removed small amounts of compact UHM material. Enzyme treatments were performed on EHEC II to further characterize it. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and anion ion-exchange chromatography coupled to pulsed amperometric detection showed that the UHM component contained EHEC.
  • Ashrafi, S., et al. (författare)
  • Monte-Carlo simulation of the charged particle detector used in the NORDBALL gamma-ray spectrometer
  • 2001
  • Ingår i: Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. - 0168-9002. ; 458:3, s. 690-697
  • Tidskriftsartikel (refereegranskat)abstract
    • The NORDBALL silicon detector array for detecting light charged particles emitted in fusion evaporation reactions was simulated with the Monte-Carlo method. The data from the reaction of 261 MeV Ni-58 ions with Cr-50 nuclei in a 4.8 mg/cm(2) thick target was used to adjust the simulation parameters. Relative population of residual nuclei in the reaction was determined, by comparing the intensities of gamma -rays.
  • Astrom, K. J., et al. (författare)
  • Design of decoupled PI controller for two-by-two systems
  • 2002
  • Ingår i: IEE Proceedings - Control Theory and Applications. - Institution of Engineering and Technology. - 1350-2379. ; 149:1, s. 74-81
  • Tidskriftsartikel (refereegranskat)abstract
    • The design of PI controllers for systems with interacting loops is discussed. It is advantageous to deal with the interaction at the loop level, because supervisory control seldom has sufficient bandwidth. A new scheme based on modified scalar PI design and static decoupling is developed, in which the frequency characteristic of the coupling between the lower-level loops is taken into account. This leads to a design method emphasising the trade-off between the individual loop performances and the interaction indices introduced in the paper. The controller is easily implemented, due to its simple configuration based on standard components. A useful observation is that the interaction can be reduced substantially by using set-point weighting. The method is applied to three examples, including a model of a new laboratory system called the quadruple-tank process
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