Change search
Refine search result
1234567 1 - 50 of 11502
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Aaltonen, J.
    et al.
    Olofsson, Bo
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Direct current (DC) resistivity measurements in long-term groundwater monitoring programmes2002In: Environmental Geology, ISSN 0943-0105, E-ISSN 1432-0495, Vol. 41, no 6, p. 662-671Article in journal (Refereed)
  • 2.
    Aaltonen, Jaana
    KTH, Superseded Departments, Civil and Environmental Engineering.
    Ground Monitoring using Resistivity Measurements in Glaciated Terrains2001Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The most common method of monitoring and mapping groundwatercontaminants is to extract and analyse a number of groundwatersamples from wells in the investigation area. However, thereare a number of limitations with this type of point-wiseinvestigation, as it is hard to acquire an adequate picture ofa heterogeneous and anisotropic subsurface using a fewpoints.

    To overcome the limitations of point investigations and toimprove ground monitoring investigations in a cost-effectiveway, support can be provided by direct current resistivitymeasurements, which give a characterisation of the electricalproperties of a ground volume.

    The main objective with this work was to investigate theusability of the resistivity method as a support in monitoringgroundwater contaminants in glaciated terrains and underdifferent seasons, both in long-term monitoring programmes andintracer tests.

    The work comprised field investigations at several differentsanitary landfills and four tracer tests in differentgeological environments, around the Stockholm region. The maininvestigations have been done at Högbytorp, Stockholmwhich has been used for long-term investigations of theresistivity variation, together with a field set up formonitoring and measurements on seasonal variation in soilmoisture, ground temperature and precipitation.

    It can be concluded that the use of resistivity measurementssupplies valuable information in the case of mapping andmonitoring conductive groundwater contaminants andfurthermore:

    The variation in resistivity (in shallow investigations<1 m) can be extensive between different seasons (around30 % compared to a mean value in till and clay soils) andshould be considered, so that anthropogenic affects can beseparated from natural resistivity variation. For deeperinvestigations (>5 m) the seasonal resistivity variationwas more moderate (around 15% compared to a mean value intill and clay soils).

    Soil moisture variation shows a strong relationship toresistivity variation in the investigated clay and tillsoils. Together with temperature correction 47 to 65% of thevariation has been explained.

    Three types of monitoring systems can be applied:Permanently installed, partly installed and fully mobilesystems. For the actual measurements, all three types can useeither high-density techniques such as CVES (ContinuousVertical Electrical Sounding) or low-density measuring withone or some different electrode spacings.

    The suggested evaluation tool for monitoring programmesshowed that it was possible to detect a decrease of 15 % inthe mean value at a specific site using Modified Double Masscalculations between resistivity time series and time seriesat a reference site with a comparable seasonalvariation.

    Resistivity measurements may be used as a valuablecomplement to groundwater sampling in tracer tests. Adecrease in resistivity, a minimum and a recovery phasereflect the passage of a NaCl-solution, which can be used toestimate flow velocity and flow patterns of the investigatedaquifer. The achieved recovery of NaCl in the tracer testscarried out was estimated to 20 to 70 %.

    The measurement system for long-term monitoring or tracertests, which should be chosen with regard to layout andfrequency, depends on the purpose of measurement and onsite-specific conditions and therefore no standard solutioncan be proposed.

    Key words:Resistivity, Direct Current, Monitoring,Groundwater, Contaminant, Tracer test, Geophysics.

  • 3.
    Aaltonen, Jaana
    KTH, Superseded Departments, Civil and Environmental Engineering.
    The use of direct current resisitivity methods in landfill investigations: a study on glaciated terrains1998Licentiate thesis, monograph (Other scientific)
  • 4.
    Aare, Magnus
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Prevention of Head Injuries - focusing Specifically on Oblique Impacts2003Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The massive number of injuries sustained in trafficaccidents is a growing problem worldwide, especially indeveloping countries. In 1998, more than one million peoplewere killed in traffic accidents worldwide, while about tentimes as many people were injured. Injuries to the centralnervous system and in particular to the headare especiallycritical to human life. This thesis contains five researchpapers looking at head injuries and head protection, proposingnew and more efficient ways of protecting the head, especiallyin traffic accidents.

    In order to define the national dimensions of the patternsof injuries incurred in motorcycle and moped accidents inSweden, a statistical survey was performed on data spanning a13-year period (Paper A). In Sweden, 27,100 individualsreceived in-patient care for motorcycle and moped accidentinjuries between 1987 and 1999. The motorcycle and moped injuryrate reduced in the second half of the study period, so toowere the total number of days of treatment per year. Males hadeight times the incidence of injuries of females. Head injurieswere the single most frequent diagnosis, followed by fracturesof the lower limbs. Concussion was the most frequent headinjury. These statistics clearly show the need for better headinjury prevention systems.

    According to the statistics, the most common type of impactto the head in motorcycle and moped accidents is an obliqueimpact. Oblique impacts generate rotations of the head, whichare a common cause of the most severe head injuries. Thereforea new test rig was constructed to reproduce oblique impacts toa helmeted dummy head, simulating those occurring in real lifeaccidents (Paper B). The new test rig was shown to provideuseful data at speeds of up to 50 km/h and with impact anglesvarying from purely tangential to purely radial. Thisinnovative test rig appears to provide an accurate method formeasuring accelerations in oblique impacts to helmets.

    When testing the performances of motorcycle helmets,discrepancies are usually seen in the test results. In order toevaluate these discrepancies, the finite element method (FEM)was used for simulations of a few oblique helmet impacts (PaperC). Amongthe parameters studied, the coefficients of frictionbetween the impacting surface and the helmet and between thehead and the helmet had the most significant influence on therotational accelerations. Additionally, a thinner andconsequently also weaker shell and a weaker liner, providedbetter protection for the impacts studied.

    Since there are no generally accepted global injurythresholds for oblique impacts to the human head, a study wasdesigned to propose new injury tolerances accounting for bothtranslations and rotations of the head (Paper D). In thatstudy, FE models of (a) a human head, (b) a Hybrid III dummyhead, and (c) the experimental helmet were used. Differentcriteria were proposed for different impact scenarios. Both thetranslational and the rotational effects were found to beimportant when proposing a predictor equation for the strainlevels experienced by the human brain in simulated impacts tothe head.

    In order to reduce the level of head injuries in society andto better understand helmet impacts from different aspect, aballistic impact was also studied (Paper E). The effects ofdifferent helmet shell stiffness and different angles ofimpacts were simulated. In this study, the same FE head modelfrom Paper D was used, however here it was protected with amodel of a composite ballistic helmet. It was concluded thatthe helmet shell should be stiff enough to prevent the insideof the shell from striking the skull, and that the strainsarising in the brain tissue were higher for some obliqueimpacts than for purely radial ones.

    In conclusion, this thesis describes the injury pattern ofmotorcycle and moped accidents in Sweden. This thesis showsthat the injuries sustained from these accidents can bereduced. In order to study both translational as well asrotational impacts, a new laboratory test rig was designed. Byusing the finite element method, it is possible to simulaterealistic impacts to the head and also to predict how severehead injuries may potentially be prevented.

  • 5.
    Aare, Magnus
    KTH, Superseded Departments, Aeronautical Engineering.
    Prevention of head injury by a new type of helmet system2002Licentiate thesis, comprehensive summary (Other scientific)
  • 6.
    Aare, Magnus
    et al.
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Kleiven, Svein
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Halldin, Peter
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Injury tolerances for oblique impact helmet testing2004In: International Journal of Crashworthiness, ISSN 1358-8265, E-ISSN 1754-2111, Vol. 9, no 1, p. 15-23Article in journal (Refereed)
    Abstract [en]

    The most frequently sustained severe injuries in motorcycle crashes are injuries to the head, and many of these are caused by rotational force. Rotational force is most commonly the result of oblique impacts to the head. Good testing methods for evaluating the effects of such impacts are currently lacking. There is also a need for improving our understanding of the effects of oblique impacts on the human head. Helmet standards currently in use today do not measure rotational effects in test dummy heads. However rotational force to the head results in large shear strains arising in the brain, which has been proposed as a cause of traumatic brain injuries like diffuse axonal injuries (DAI). This paper investigates a number of well-defined impacts, simulated using a detailed finite element (FE) model of the human head, an FE model of the Hybrid III dummy head and an FE model of a helmet. The same simulations were performed on both the FE human head model and the FE Hybrid III head model, both fitted with helmets. Simulations on both these heads were performed to describe the relationship between load levels in the FE Hybrid III head model and strains in the brain tissue in the FE human head model. In this study, the change in rotational velocity and the head injury criterion (HIC) value were chosen as appropriate measurements. It was concluded that both rotational and translational effects are important when predicting the strain levels in the human brain.

  • 7.
    Aarno, Daniel
    et al.
    KTH, Superseded Departments, Numerical Analysis and Computer Science, NADA.
    Kragic, Danica
    KTH, Superseded Departments, Numerical Analysis and Computer Science, NADA.
    Christensen, Henrik
    KTH, Superseded Departments, Numerical Analysis and Computer Science, NADA.
    Artificial potential biased probabilistic roadmap method2004In: 2004 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1- 5, PROCEEDINGS, 2004, p. 461-466Conference paper (Refereed)
    Abstract [en]

    Probabilistic roadmap methods (PRMs) have been successfully used to solve difficult path planning problems but their efficiency is limited when the free space contains narrow passages through which the robot must pass. This paper presents a new sampling scheme that aims to increase the probability of finding paths through narrow passages. Here, a biased sampling scheme is used to increase the distribution of nodes in narrow regions of the free space. A partial computation of the artificial potential field is used to bias the distribution of nodes.

  • 8.
    Aas, Wenche
    KTH, Superseded Departments, Chemistry.
    Constitution, dynamics and structure of binary and ternary actinide complexes1999Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Stoichiometry, ligand exchange reactions, coordinationgeometry and stability of complexes of type UO2LpFq(H2O)3-n(p= 1–2,q= 1-3), where L is one of the bidentate ligandspicolinate, oxalate, carbonate or acetate have beeninvestigated using single crystal X-ray diffraction, an arrayof19F-,13C-,17O- and1H-NMR techniques and potentiometric titration usingboth F-and H+selective electrodes. The experiments wereperformed in a 1.00 M NaClO4medium. The equilibrium constants were determinedat 25°C while most of the kinetic experiments were done at- 5°C. The equilibrium constants for the stepwise additionof F-to UO2L and UO2L2indicates that the prior coordination of L toU(VI) has a fairly small effect on the subsequent bonding offluoride, except for a statistical effect determined by thenumber of available coordination sites. This indicates thatternary complexes might be important for the speciation andtransport of hexavalent actinides in ground and surface watersystems. A single crystal structure of UO2(picolinate)F32-has been determined showing the same pentagonalbipyramidal symmetry as in aqueous solution studied by NMR. Theexchangeable donor atoms are situated in a plane perpendicularto the linear uranyl group. The complexes show a variety ofdifferent exchange reactions depending on the ligand used. Ithas been possible to quantify external fluoride and the otherligands exchange reactions as well asintra-molecular reactions. This type of detailedinformation has not been observed in aqueous solution before.Water takes a critical part in the exchange mechanism, and whenit is eliminated from the inner coordination sphere a muchslower kinetics can be observed.19F-NMR has showed to be a powerful technique tostudy these reactions, both because of the sensitivity of thisNMR nucleus and also the possibility to observe reactions wherefluoride is not directly involved in the mechanism. TernaryTh(edta)F1-2and (UO2)2(edta)2F1-4have been investigated using1H and19F-NMR. The fluoride complexation to Cm(III) wasstudied using time resolved fluorescence spectroscopy (TRLFS)and the stability constant for the CmF2+complex was determined at 25°C in 1.0 mNaCl.

    Keywords. Ternary complexes, actinides,dioxouranium(VI), curium(III), thorium(IV), ligand exchange,isomers, NMR, potentiometric titrations, aqueous solution,oxalate, picolinate, acetate, EDTA.

  • 9. Aastrup, T.
    et al.
    Wadsak, M.
    Leygraf, Christofer
    KTH, Superseded Departments, Materials Science and Engineering.
    Schreiner, M.
    In situ studies of the initial atmospheric corrosion of copper influence of humidity, sulfur dioxide, ozone, and nitrogen dioxide2000In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 147, no 7, p. 2543-2551Article in journal (Refereed)
    Abstract [en]

    Infrared reflection absorption spectroscopy and quartz crystal microbalance, integrated into a one-surface analytical system, and complemented with tapping mode atomic force microscopy, has been used to explore the metal/atmosphere interfacial region under atmospheric pressure conditions. This unique combination of ill situ techniques, all possessing submonolayer sensitivity, has revealed information on the different accelerating roles of ozone (O-3) and nitrogen dioxide (NO2) on the SO2-induced atmospheric corrosion of copper. The formation of reaction products could be followed quantitatively with respect to chemical identity and kinetics. Exposure in SO2-containing humidified air resulted in CuSO3. xH(2)O-like species, formed atop a cuprous oxide, designated Cu2O, all over the copper surface. O-3 introduction resulted in an accelerated mass gain with an increased formation rate of both Cu2O and of CuSO4. xH(2)O all over the surface. NO2 introduction resulted in less mass gain than observed under SO2 and O-3, with no formation of new Cu2O, an initial oxidation of CuSO3. xH(2)O to CuSO4. xH(2)O, and with sulfite oxidation gradually replaced by copper nitrate formation, possibly as CuNO3(OH)(3) The formation rates of the dominating end products, CuSO4. xH(2)O in SO2/O-3 and Cu2NO3(OH)(3) in SO2/NO2 seemed to be limited by the supply of the gaseous constituents.

  • 10. Aastrup, T.
    et al.
    Wadsak, M.
    Schreiner, M.
    Leygraf, Christofer
    KTH, Superseded Departments, Materials Science and Engineering.
    Experimental in situ studies of copper exposed to humidified air2000In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 42, no 6, p. 957-967Article in journal (Refereed)
    Abstract [en]

    Three complementary experimental techniques for in situ surface analysis have been combined for the first time in order to explore the chemistry and physics of a copper surface exposed to humidified air. Infrared reflection absorption spectroscopy, quartz crystal microbalance and atomic force microscopy provide a congruent picture of the processes occurring at the surface. At a given relative humidity, cuprous oxide forms according to an approximately logarithmic rate law. In addition, an aqueous adlayer of constant mass physisorbs on the surface. Increased relative humidity stimulates the physisorption of water and enhances the nucleation rate of oxide grains, thereby increasing the formation rate of cuprous oxide.

  • 11.
    Aastrup, Teodor
    KTH, Superseded Departments, Materials Science and Engineering.
    In situ investigations of the metal/atmophere interface1999Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis presents a new experimental setup for surfaceanalysis studies, incorporating chemical information frominfrared reflection absorption spectroscopy (IRAS) andquantitative information from quartz crystal microbalance(QCM). The integrated IRAS/QCM surface analysis system enablesin situstudies to be conducted of the metal/atmosphereinteraction on a sub-monolayer level. In combination withtopographical information from tapping mode atomic forcemicroscopy (TM-AFM), it was possible to follow the formation ofcorrosion products providing information about chemicalidentity, quantity and lateral distribution. The newlydeveloped system was used to study the influence of relativehumidity (RH) and levels of sulfur dioxide (SO2), ozone (O3)and nitrogen dioxide (NO2) down to concentrations of subparts-per-million (ppm), on the initial stages of atmosphericcorrosion of copper.

    Exposure to RH led to the formation of small grains ofcuprous oxide (Cu2O), with an average diameter of approximately40 nm. The grain nucleation rate increased with increasing RHdue to the increasing amount of physisorbed water on thesurface.

    Exposure to RH and SO2 led to the formation of coppersulfite (CuSO3•xH2O) species as well as reduction in therate of Cu2O formation. The formation of CuSO3•xH2Ooccurred through the dissolution and consecutive precipitationof surface-bound copper sulfite complexes.

    The roles of O3 and NO2 in the SO2-induced atmosphericcorrosion of copper was also investigated. O3 was found to havea two-fold effect, resulting in the oxidation of the coppersulfite species to copper sulfate and the enhancement of Cu2Oformation. NO2 promoted the oxidation of copper sulfitespecies, though less efficiently than O3, and reduced Cu2Oformation. In addition, copper nitrate formation wasobserved.

    IRAS was also used to investigate the interaction betweenSO2 and surfaces made of platinum and palladium. Sulfuric acidformation was observed on both metals, showing the importanceof the surface on the formation of the metal/atmospherereaction products.

    Keywords:Atmospheric corrosion, IR-spectroscopy, IRAS,QCM, AFM, SO2, O3, NO2, Cu.

  • 12. Abadei, S.
    et al.
    Gevorgian, S.
    Cho, C. R.
    Grishin, Alexander M.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Low-frequency and microwave performances of laser-ablated epitaxial Na0.5K0.5NbO3 films on high-resistivity SiO2/Si substrates2002In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 91, no 4, p. 2267-2276Article in journal (Refereed)
    Abstract [en]

    The dielectric properties of laser-ablated 0.5-mum-thick c-axis epitaxial Na0.5K0.5NbO3 (NKN) films on high-resistivity (>7.7 kOmega cm) silicon SiO2/Si substrates are studied experimentally in the temperature interval of 30-320 K and at frequencies of 1.0 MHz-40 GHz. The films are grown by laser ablation from a stoichiometric target. For the measurements, planar 0.5-mum-thick gold electrodes (interdigital and straight slot) are photolithography defined on the top surface of NKN films. The slot width between the electrodes is 2.0 or 4.0 mum. At low frequencies (f<1.0 GHz), the structure performance is that of a typical metal-dielectric-semiconductor type, where two of this type of capacitor are connected back to back. At these frequencies, the large change in the capacitance (more than 10 times at 1.0 MHz), due to the applied dc field, is mainly due to the changes in depletion layer thickness at the surface of silicon. The associated losses are also large, tan delta>1. At microwave frequencies (f>10 GHz), the voltage dependence of the capacitance is given by the NKN film. More than a 13% capacitance change at 40 V dc bias and a Q factor of more than 15 are observed at 40 GHz, which make the structure useful for applications in electrically tunable millimeter-wave devices.

  • 13. Abadei, S.
    et al.
    Gevorgian, S.
    Cho, C. R.
    Grishin, Alexander M.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Andreasson, J.
    Lindback, T.
    DC field dependent properties of Na0.5K0.5NbO3/SiO2/Si structures at millimeter-wave frequencies2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, no 13, p. 1900-1902Article in journal (Refereed)
    Abstract [en]

    Dielectric properties of laser-ablated 0.5-mum-thick c-axis epitaxial Na0.5K0.5NbO3 films on high-resistivity (7.7 Omega cm) silicon SiO2/Si substrate are studied experimentally at frequencies up to 40 GHz. For measurements, planar 0.5-mum-thick gold electrodes (interdigital and straight slot) are photolithography defined on the top surface of Na0.5K0.5NbO3 films. The slot width between the electrodes is 2 or 4 mum. 13% capacitance change at 40 V dc bias and Q factor more than 15 are observed at 40 GHz, which makes the structure useful for applications in electrically tunable millimeter-wave devices.

  • 14.
    Abarkan, Abdellah
    KTH, Superseded Departments, Architecture.
    Reshaping regional planning: A northern perspective2004In: European Urban and Regional Studies, ISSN 0969-7764, E-ISSN 1461-7145, Vol. 11, no 2, p. 180-181Article, book review (Refereed)
  • 15. Abbondanno, U
    et al.
    Carlson, Per
    KTH, Superseded Departments, Physics.
    Peskov, Vladimir
    KTH, Superseded Departments, Physics.
    Zanini, L
    et al.,
    New experimental validation of the pulse height weighting technique for capture cross-section measurements2004In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 521, no 2-3, p. 454-467Article in journal (Refereed)
    Abstract [en]

    The accuracy of the pulse height weighting technique for the determination of neutron capture cross-sections is investigated. The technique is applied to measurements performed with C6D6 liquid scintillation detectors of two different types using capture samples of various dimensions. The data for well-known (n, gamma) resonances are analyzed using weighting functions obtained from Monte Carlo simulations of the experimental set-up. Several causes of systematic deviation are identified and their effect is quantified. In all the cases measured the reaction yield agrees with the standard value within 2%.

  • 16. Abdalla, M. A.
    et al.
    Frojdh, C.
    Petersson, C. Sture
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A CMOS APS for dental X-ray imaging using scintillating sensors2001In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 460, no 1, p. 197-203Article in journal (Refereed)
    Abstract [en]

    In this paper we present an integrating CMOS Active Pixel Sensor (APS) circuit to be used with scintillator type X-ray sensors for intra oral dental X-ray imaging systems. Different pixel architectures were constructed to explore their performance characteristics and to study the feasibility of the development of such systems using the CMOS technology. A prototype 64 x 80 pixel array has been implemented in a CMOS 0.8 mum double poly n-well process with a pixel pitch of 50 mum. A spectral sensitivity measurement for the different pixels topologies, as well as measured X-ray direct absorption in the different APSs are presented. A measurement of the output signal showed a good linearity over a wide dynamic range. This chip showed that the very low sensitivity of the CMOS APSs to direct X-ray exposure adds a great advantage to the various CMOS advantages over CCD-based imaging systems,

  • 17. Abdalla, M. A.
    et al.
    Frojdh, C.
    Petersson, C. Sture
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    An integrating CMOS APS for X-ray imaging with an in-pixel preamplifier2001In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 466, no 1, p. 232-236Article in journal (Refereed)
    Abstract [en]

    We present in this paper an integrating CMOS Active Pixel Sensor (APS) circuit coated with scintillator type sensors for intra-oral dental X-ray imaging systems. The photosensing element in the pixel is formed by the p-diffusion on the n-well diode. The advantage of this photosensor is its very low direct absorption of X-rays compared to the other available photosensing elements in the CMOS pixel. The pixel features an integrating capacitor in the feedback loop of a preamplifier of a finite gain in order to increase the optical sensitivity. To verify the effectiveness of this in-pixel preamplification, a prototype 32 x 80 element CMOS active pixel array was implemented in a 0.8 mum CMOS double poly, n-well process with a pixel pitch of 50 mum. Measured results confirmed the improved optical sensitivity performance of the APS. Various measurements on device performance are presented.

  • 18.
    Abdalla, Munir
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Pixel Detectors and Electronics for High Energy Radiation Imaging2001Doctoral thesis, comprehensive summary (Other scientific)
  • 19. Abe, T.
    et al.
    Sundman, Bo
    KTH, Superseded Departments, Materials Science and Engineering.
    A description of the effect of short range ordering in the compound energy formalism2003In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 27, no 4, p. 403-408Article in journal (Refereed)
    Abstract [en]

    The current state of the compound energy formalism (CEF) to model ordering and the technique to handle short range ordering (SRO) were discussed. Although there are some methods which allow better treatment for SRO, such as the cluster variation method (CVM) or the Monte Carlo method (MC), these methods are difficult to handle in multi-component systems because of their complexity. In the compound energy formalism, SRO is not explicitly described. However it is possible to take the contribution of SRO to the Gibbs free energy into account through the reciprocal parameter, which has the same concentration dependency as DeltaG(m)(SRO). Introducing the reciprocal parameter of the form, L-i,L-j:i,L-j for the two sublattice model and L-i,L-j:i,L-j:*:* for the four sublattice model, one can satisfactorily describe the contribution of SRO to the Gibbs free energy in the CEF.

  • 20.
    Abenius, Erik
    KTH, Superseded Departments, Numerical Analysis and Computer Science, NADA.
    Time-Domain Inverse Electromagnetic Scattering using FDTD and Gradient-based Minimization2004Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    The thesis addresses time-domain inverse electromagneticscattering for determining unknown characteristics of an objectfrom observations of the scattered .eld. Applications includenon-destructive characterization of media and optimization ofmaterial properties, for example the design of radar absorbingmaterials.A nother interesting application is the parameteroptimization of subcell models to avoid detailed modeling ofcomplex geometries.

    The inverse problem is formulated as an optimal controlproblem where the cost function to be minimized is thedi.erence between the estimated and observed .elds, and thecontrol parameters are the unknown object characteristics. Theproblem is solved in a deterministic gradient-basedoptimization algorithm using a parallel 2D FDTD scheme for thedirect problem.This approach is computationally intensive sincethe direct problem needs to be solved in every optimizationiteration in order to compute an estimated .eld.H ighlyaccurate analytical gradients are computed from the adjointformulation.In addition to giving better accuracy than .nitedi.erences, the analytical gradients also have the advantage ofonly requiring one direct and one adjoint problem to be solvedregardless of the number of parameters.

    When absorbing boundary conditions are used to truncate thecomputational domain, the equations are non-reversible and theentire time-history of the direct solution needs to be storedfor the gradient computation.Ho wever, using an additionaldirect simulation and a restart procedure it is possible tokeep the storage at an acceptable level.

    The inverse method has been successfully applied to a widerange of industrial problems within the European project,IMPACT (Inverse Methods for Wave Propagation Applications inTime-Domain).T he results presented here includecharacterization of layered dispersive media, determination ofparameters in subcell models for thin sheets and narrow slotsand optimization problems where the observed .eld is given bydesign objectives.

  • 21. Aberg, D.
    et al.
    Hallén, Anders.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Pellegrino, P.
    Svensson, B. G.
    Nitrogen deactivation by implantation-induced defects in 4H-SiC epitaxial layers2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, no 19, p. 2908-2910Article in journal (Refereed)
    Abstract [en]

    Ion implantation causes free charge carrier reduction due to damage in the crystalline structure. Here, nitrogen-doped 4H silicon carbide (n type) epitaxial layers have been investigated using low ion doses in order to resolve the initial stage of the charge carrier reduction. It was found that the reduction of free carriers per ion-induced vacancy increases with increasing nitrogen content. Nitrogen is suggested to be deactivated through reaction with migrating point defects, and silicon vacancies or alternatively interstitials are proposed as the most likely candidates.

  • 22. Aberg, D.
    et al.
    Hallén, Anders.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Pellegrino, P.
    Svensson, B. G.
    Nitrogen passivation by implantation-induced point defects in 4H-SiC epitaxial layers2001In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 184, no 04-jan, p. 263-267Article in journal (Refereed)
    Abstract [en]

    Ion implantation causes damage to the crystal lattice resulting in the loss of free charge carriers. In this study, low dose implantations using different ions and implantation doses are made to resolve the initial carrier loss in nitrogen-doped epitaxial layers. A strong dependence of compensation on nitrogen concentration is seen, showing that nitrogen is passivated by implantation-induced point defects. An activation energy of 3.2 eV for the dissociation of the passivated nitrogen center is obtained.

  • 23. Aberg, J
    et al.
    Persson, S
    Hellberg, Per-Erik
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Zhang, Shi-Li
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Smith, U
    Ericson, F
    Engstrom, M
    Kaplan, W
    Electrical properties of the TiSi2-Si transition region in contacts: The influence of an interposed layer of Nb2001In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 90, no 5, p. 2380-2388Article in journal (Refereed)
    Abstract [en]

    The influence of an interposed ultrathin Nb layer between Ti and Si on the silicide formation and the electrical contact between the silicide formed and the Si substrate is investigated. The presence of the Nb interlayer results in the formation of ternary alloy (Nb,Ti)Si-2 in the C40 crystallographic structure adjacent to the Si substrate. Depending on the nature of the Si substrates and/or the amount of the initial Nb, the interfacial C40 (Nb,Ti)Si-2 leads, in turn, to either epitaxial growth of a highly faulted metastable C40 TiSi2 or formation of the desired C54 TiSi2 at a lower temperature than needed for it to form in reference samples with Ti deposited directly on Si. On p-type substrates doped to various concentrations, the Nb also leads to a considerably lower specific contact resistivity than that obtained in the reference samples: a twofold to fourfold reduction in the contact resistivity is found using cross-bridge Kelvin structures in combination with two-dimensional numerical simulation. As C40 (Nb,Ti)Si-2 forms at the interface when an interfacial Nb is present, the interface characterized is likely to represent the one between (Nb,Ti)Si-2 and Si. For the reference samples, the interface studied is between TiSi2 and Si.

  • 24. Aberg, V.
    et al.
    Bostrom, D.
    Fischer, Andreas
    KTH, Superseded Departments, Chemistry.
    Almqvist, F.
    Synthesis and absolute configuration of methyl(-)-(3R)-8-(4-bromophenyl)-7-(naphthalen-1-yl-methyl)-5-oxo-2,3-dihydro-5H-thiazolo 3,2-a pyridine-3-carboxylate2002In: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 58, p. o812-o814Article in journal (Refereed)
    Abstract [en]

    The title molecule, C26H20BrNO3S, contains a ring-fused 2-pyridinone framework substituted with a 4-bromo-phenyl-, a naphthalen-1-ylmethyl and a methoxycarbonyl substituent. The main goal of this work was to confirm the stereochemistry for the methoxycarbonyl substituent, which proved to be 3R. Moreover, the 4-bromophenyl substituent was shown to be rotated out of the plane of the 2-pyridinone ring, with a torsion angle of 61.2 (5)degrees. To allow the best packing arrangement, the naphthalen-1-ylmethyl substituent is positioned to mediate an intermolecular pi-pi interaction.

  • 25.
    Abili Nejad, Maryam
    KTH, Superseded Departments, Chemistry.
    Kinetics for oxidation of CRUD model compounds2004Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The formation of CRUD (Chalk River Unidentified Deposit) inwater-cooled nuclear reactors constitute a severe problem. Thestability of CRUD under reactor conditions (high flux ofionizing radition, high temperature and pressure) must be knownin order to minimize the problem. The kinetics for CRUDoxidation by H2O2 and the two more potent oxidants IrCl62-and MnO4- has been studied using aqueous suspensions ofthree metal oxide powders, Fe3O4, Fe2CoO4 and Fe2NiO4. The metal oxides were used as model compounds forCRUD. The latter two oxidants were employed to study therelationship between kinetics and the reduction potential ofthe oxidant. In addition, the activation energies for thereaction between H2O2and the three metal oxides of CRUD model weredetermined. The mechanism of the reaction is discussedindicating that the final solid product in all three cases isFe2O3. Our experimental results show that the reactivityof the metal oxides towards oxidants is in the order Fe2CoO4>Fe3O4>Fe2NiO4. The relative reactivities of Fe2CoO4 and Fe3O4are in contrast with that expected from the studyof the ionization potentials of the divalent metals in theoxides. In addition to the experimental studies, thetheoretical grounds for kinetics of reactions in particlesolutions are discussed. The theoretical discussion is alsoused to explain the somewhat unexpected trends in reactivityobserved experimentally. The same reaction trend is alsoobserved in the reaction of the metal oxides with IrCl62-and MnO4-.

    We found experimentally that the logarithm of second orderrate constants of the reaction of metal oxides with oxidantsagainst the one electron potential of the oxidants follows aparabolic behavior in agreement with the Marcus theory forelectron transfer reactions. This work constitutes a good basisfor the design of further model studies aiming at resolving thestability of CRUD under reactor conditions.

    Keywords:Reactor Chemistry, Radiolysis, Oxidation,Kinetics, CRUD, Metal oxide

  • 26. Aboelfotoh, M. O.
    et al.
    Frojdh, C.
    Petersson, C. Sture
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Schottky-barrier behavior of metals on n- and p-type 6H-SiC2003In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 67, no 7Article in journal (Refereed)
    Abstract [en]

    The Schottky-barrier height of a number of metals (Ti, Ni, Cu, and Au) on n- and p-type Si-terminated 6H-SiC has been measured in the temperature range 150-500 K. It is found that the barrier height to n-type 6H-SiC does not exhibit a temperature dependence, while for p-type 6H-SiC the change in the barrier height with temperature follows very closely the change in the indirect energy gap in 6H-SiC. These results are inconsistent with models of Schottky-barrier formation based on the concept of a charge neutrality level. Furthermore, the present results cannot be reconciled with a defect pinning mechanism, contrary to the conclusions of earlier studies on III-V compound semiconductors. We suggest that chemical bonding at the metal-semiconductor interface plays an important role in determining the Schottky-barrier height.

  • 27. Abraham, T.
    et al.
    Kumpulainen, A.
    Xu, Z.
    Rutland, Mark W
    KTH, Superseded Departments, Chemistry.
    Claesson, Per M.
    KTH, Superseded Departments, Chemistry.
    Masliyah, J.
    Polyelectrolyte-mediated interaction between similarly charged surfaces: Role of divalent counter ions in tuning surface forces2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, no 26, p. 8321-8327Article in journal (Refereed)
    Abstract [en]

    The effects of divalent salts (CaCl2, MgCl2 and BaCl2) in promoting the adsorption of weakly charged polyelectrolyte (polyacrylic acid), PAA, Mw similar to 250000 g/mol) on mica surfaces and their role in tuning the nature of interactions between such adsorbed polyelectrolyte layers were studied using the interferometric surface forces apparatus. With mica surfaces in 3 mM MgCl2 solutions at pH similar to8.0-9.0, the addition of 10 ppm PAA resulted in a long-range attractive bridging force and a short-range repulsive steric force. This force profile indicates a low surface coverage and weak adsorption. The range of the force can be related to the characteristic length scale R-G of polyelectrolyte chains using a scaling description. An increase of the PAA concentration to 50 ppm changed the attractive force profile to a monotonic, long-range repulsive interaction extending up to 600 Angstrom due to the increased surface coverage of polyelectrolyte chains on the mica surfaces. Comparison of the measured forces with a scaling mean field model suggests that the adsorbed polyelectrolyte chains are stretched, which eventually give rise to the polyelectrolyte brush like structure. When the mica surfaces were preincubated in 3 mM CaCl2 at pH similar to8.0-9.0, in contrast to the case of 3 MM MgCl2, the addition of 10 ppm PAA resulted in a more complex force profile: long-range repulsive forces extending up to 800 Angstrom followed by an attractive force regime and a second repulsive force regime at shorter separations. The long-range electrosteric forces can be attributed to strong adsorption of polyelectrolyte chains on mica surfaces (high surface coverage) which is facilitated by the presence of Ca2+ ions, while the intermediate range attractive forces can be ascribed to Ca2+ assisted bridging between adsorbed polyelectrolyte chains. Also interesting is to note various relaxation processes present in this system. In contrast to both MgCl2 and CaCl2 systems, with mica surfaces in 3 mM BaCl2 solution at pH similar to8.0-9.0, the addition of 10 ppm PAA resulted in precipitation of polyelectrolyte chains on mica surfaces, resulting in an extremely long-range monotonic repulsive force profile. In summary, our study showed that divalent counterions (Mg2+, Ca2+, and Ba2+) exhibit significantly different behavior in promoting PAA adsorption on mica surfaces, modifying and controlling various surface interactions.

  • 28.
    Abrahamsson, Lars
    et al.
    KTH, Superseded Departments, Electric Power Systems.
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Optimal PowerFlow (OPF) Model with Unified AC-DC Load Flow and Optimal Commitmentfor an AC-catenary Railway Power Supply System (RPSS) fed by aHigh Voltage DC (HVDC) transmission lineManuscript (preprint) (Other academic)
    Abstract [en]

    In this paper an alternative railway power systems design based on an HVDC feeder is studied. The HVDC feeder is connected to the catenary by converters. Such an HVDC line is also appropriate for DC-fed railways and AC-fed railways working at public frequency.

    A unit commitment optimal power flow model has been developed and is applied on a test system. In this paper, the model is presented in detail. The model, in the form of an MINLP program, uses unified AC-DC power flow to minimize the entire railway power system losses.

    Simulations of the proposed solution show clear advantages regarding transmission losses and voltages compared to conventional systems, especially for cases with long distances between feeding points to the catenary, and when there are substantial amounts of regeneration from the trains.

  • 29. Abrikosov, I. A.
    et al.
    Olovsson, W.
    Johansson, Börje
    KTH, Superseded Departments, Materials Science and Engineering.
    Valence-band hybridization and core level shifts in random Ag-Pd alloys2001In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 8717, no 17Article in journal (Refereed)
  • 30.
    Ackalin, Jan
    KTH, Superseded Departments, Production Systems.
    The process of resetting in small batch size manufacturing of mechanical parts1999Licentiate thesis, monograph (Other scientific)
  • 31. Acker, A.
    et al.
    Henrot, A.
    Poghosyan, M.
    Shahgholian, Henrik
    KTH, Superseded Departments, Mathematics.
    The multi-layer free boundary problem for the p-Laplacian in convex domains2004In: Interfaces and free boundaries (Print), ISSN 1463-9963, E-ISSN 1463-9971, Vol. 6, no 1, p. 81-103Article in journal (Refereed)
    Abstract [en]

    The main result of this paper concerns existence of classical solutions to the multi-layer Bernoulli free boundary problem with nonlinear joining conditions and the p-Laplacian as governing operator. The present treatment of the two-layer case involves technical refinements of the one-layer case, studied earlier by two of the authors. The existence treatment of the multi-layer case is largely based on a reduction to the two-layer case, in which uniform separation of the free boundaries plays a key role.

  • 32.
    Ackerberg, Björn
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Application of some statistical methods for evaluation of groundwater observations2002Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    With the objective of reviewing different statisticalmethods for evaluation of groundwater data and the design of agroundwater observation network, a comprehensive literaturesurvey was performed. The literature survey focuses on spatialstatistics (geostatistics) but also includes methods toevaluate time-series of groundwater data and the determinationof the sampling frequency. A method is developed which providesa means of quantifying the accuracy of an existing groundwatermonitoring network with regards to spatial interpolation andthe locations of the corresponding observation points. Thespatial interpolation method of ordinary kriging was used. Aresult from ordinary kriging was estimated (interpolated)levels at unmeasured points, but also a kriging variance. Thekriging variance can be interpreted as a measure of theestimation accuracy and used as a criterion for network design.Design of a monitoring network for groundwater levels in anarea includes the selection of: - the number of observationpoints and - the spatial locations of observation points.The method was applied to design a monitoring network inan area in a glaciofluvial deposit, the Nybro esker, which isthe main aquifer for the water supply of the Kalmar-Nybroregion in the southeast of Sweden. This thesis shows that it ispossible to quantify the accuracy of an existing observationnetwork using the average kriging variance as a measure ofaccuracy. It is also possible to describe how this krigingvariance changes (increases) when the observation network isreduced. By using this variance is it possible to rank thedifferent points in the network as to their relativeimportance. It is thus possible to identify the points, whichare to be removed when the observation network is reduced, onepoint at a time. This study shows that a monitoring network inthe study area could be reduced by 35% while the increase inaverage estimation (kriging) variance is only about 10%.Although the method is applied to groundwater levels in aglaciofluvial deposit, it is applicable also to other variablesthat can be considered regionalized and to other geologicalenvironments.

  • 33.
    Ackermann, Thomas
    KTH, Superseded Departments, Electrical Systems.
    Distributed Resources in a Re-Regulated Market Environment2004Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    This thesis analyses the value that distributed resources(DR) can contribute to an economically effcient operation of are-regulated electricity market and discusses the relevantchanges in the regulatory framework to allow the appropriatedevelopment of DR whenever DR may increase the economiceffciency of the electricity market.

    Distributed resources thereby combine two aspects:Distributed generation and demand-side resources. Distributedgeneration is defined as generation within the distributionsystem or on the customer side of the meter. Demand-sideresources are those load resources on the customer-side thatcan be used to shift electricity demand from peak to off-peakperiods, or to reduce the overall electricity demand.

    To gain a better understanding of the value that DR mayprovide in a re-regulated market, an analysis of there-regulation approaches in England andWales, Scandinavia,Australia, New Zealand as well as in two regions in the USA isperformed. The key findings of this analysis are that non ofthe re-regulation approaches put special emphasis on DR. Thecomparison also shows that despite very different approachesused in the various markets, the remaining re-regulationproblems are very similar. These key problems are mainlyrelated to market power in the various markets and littlecompetition in network services.

    The thesis shows that DR has the potential to improveoverall economic market effciency by reducing market powerissues and increasing competition in network services. Forinstance, many DR business schemes have no incentive toexercise market power, because withholding generation may havea negative impact on the complex revenue stream from differentincome sources. While this may not allow the general conclusionthat DR will always provide benefits to market operation, it isimportant to consider that not all DR need to provide suchbenefits, as it was also shown that already comparatively smallamounts of demand resources or distributed generation cansignificantlyreduce market power issues. In addition, it wasalso shown that DR can introduce competition into networkservices and therefore can provide incentives for distributionand transmission network companies to operate more costeffectively.

    It was also demonstrated that the potential of DR to improveoverall economic market effciency will only be realized if:

    1. DR is developed in the correct size, i.e. DR should fitinto an existing distribution network and may increase networkutilization rate,2. DR is developed at the correct location in thenetwork, e.g. in areas with congestion problems,3. DR is in operation during the correct times, whenbeneficial to the market, e.g. during times when market powerissues may arise, and4. independent ownership of DR projects isencouraged.

    Market regulations therefore must provide the correctincentives for the correct siting and operation of DR as wellas for independent ownership. The thesis uses examples andempirical data to explain the relevant regulatory aspects indetail and provides suggestions for a regulatory framework thatconsiders the potential of DR to improve overall economiceffciency in an electricity market.

  • 34.
    Ackermann, Thomas
    et al.
    KTH, Superseded Departments.
    Andersson, G.
    Söder, Lennart
    KTH, Superseded Departments.
    Distributed generation: a definition2001In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 57, no 3, p. 195-204Article in journal (Refereed)
  • 35.
    Ackermann, Thomas
    et al.
    KTH, Superseded Departments.
    Andersson, G.
    Söder, Lennart
    KTH, Superseded Departments.
    Overview of government and market driven programs for the promotion of renewable power generation2001In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 22, no 1-3, p. 197-204Article in journal (Refereed)
  • 36.
    Ackermann, Thomas
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Andersson, Göran
    Söder, Lennart
    KTH, Superseded Departments.
    Electricity market regulations and their impact on distributed generation2000In: Electric Utility Deregulation and Restructuring and Power Technologies, 2000. Proceedings. DRPT 2000. International Conference on, 2000, p. 608-613Conference paper (Refereed)
    Abstract [en]

    Distributed generation (DG) has attracted a lot of attention recently and might become more important in future power generation systems. As different definitions are used worldwide, the paper briefly discusses the definition of DG. The future development of DG, however, will, to a not insignificant part, depend on the legal framework. As the legal framework can vary significantly for different competitive electricity markets, this paper briefly identifies and analyses some variations in the regulatory approaches, e.g. for power exchanges, balance services and ancillary services, in different countries. It also illustrates the influence of market regulations on the development of distributed power generation. Based on this analysis, it can be concluded that regulatory aspects might decisively influence the development of distributed power generation

  • 37.
    Ackermann, Thomas
    et al.
    KTH, Superseded Departments.
    Söder, Lennart
    KTH, Superseded Departments.
    An overview of wind energy-status 20022002In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 6, no 1-2, p. 67-128Article, review/survey (Refereed)
  • 38.
    Ackermann, Thomas
    et al.
    KTH, Superseded Departments.
    Söder, Lennart
    KTH, Superseded Departments.
    Wind energy technology and current status: a review2000In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 4, no 4, p. 315-374Article, review/survey (Refereed)
  • 39. Adachi, N.
    et al.
    Denysenkov, V. P.
    Khartsev, Sergiy
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Okuda, T.
    Epitaxial Bi3Fe5O12(001) films grown by pulsed laser deposition and reactive ion beam sputtering techniques2000In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 88, no 5, p. 2734-2739Article in journal (Refereed)
    Abstract [en]

    We report on processing and comparative characterization of epitaxial Bi3Fe5O12 (BIG) films grown onto Gd-3(ScGa)(5)O-12[GSGG,(001)] single crystal using pulsed laser deposition (PLD) and reactive ion beam sputtering (RIBS) techniques. A very high deposition rate of about 0.8 mu m/h has been achieved in the PLD process. Comprehensive x-ray diffraction analyses reveal epitaxial quality both of the films: they are single phase, exclusively (001) oriented, the full width at half maximum of the rocking curve of (004) Bragg reflection is 0.06 deg for PLD and 0.05 deg for RIBS film, strongly in-plane textured with cube-on-cube film-to-substrate epitaxial relationship. Saturation magnetization 4 pi M-s and Faraday rotation at 635 nm were found to be 1400 Gs and -7.8 deg/mu m in PLD-BIG, and 1200 Gs and -6.9 deg/mu m in RIBS-BIG. Ferromagnetic resonance (FMR) measurements performed at 9.25 GHz yielded the gyromagnetic ratio gamma=1.797x10(7) l/s Oe, 1.826x10(7) l/s Oe; the constants of uniaxial magnetic anisotropy were K-u(*)=-8.66x10(4) erg/cm(3), -8.60x10(4) erg/cm(3); the cubic magnetic anisotropy K-1=-2.7x10(3) erg/cm(3),-3.8x10(3) erg/cm(3); and the FMR linewidth Delta H=25 and 34 Oe for PLD and RIBS films correspondingly. High Faraday rotation, low microwave loss, and low coercive field less than or equal to 40 Oe of BIG/GSGG(001) films promise their use in integrated magneto-optic applications.

  • 40. Adachi, N.
    et al.
    Okuda, T.
    Denysenkov, Vasyl
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Jalali-Roudsar, Amir
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Grishin, Alexander
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Magnetic properties of single crystal film Bi3Fe5O12 prepared onto Sm3(Sc, Ga)5O12(111)2002In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 242, no Part 2, p. 775-777Article in journal (Refereed)
    Abstract [en]

    Magnetic properties of single crystal Bi3Fe5O12 has been investigated in the temperature range between 2 and 670K. The Sm3(Sc,Ga)5O12 wafer has been used for substrates. Due to the small contribution of the substrate's magnetization, the film's magnetization can be clearly estimated to be 2040G (0K) and the Curie temperature has been estimated to be around 650K.

  • 41.
    Adam, Constantin
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Stadler, Rolf
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Patterns for Routing and Self-Stabilization2004In: NOMS 2004: IEEE/IFIP NETWORK OPERATIONS AND MANAGMENT SYMPOSIUM - MANAGING NEXT GENERATION CONVERGENCE NETWORKS AND SERVICES, New York: IEEE , 2004, p. 61-74Conference paper (Refereed)
    Abstract [en]

    This paper contributes towards engineering self-stabilizing networks and Services. We propose the use of navigation patterns, which define how information for state updates is disseminated in the system, as fundamental building blocks for self-stabilizing systems. We present two navigation patterns for self-stabilization: the progaressive wave pattern and the stationary wave pattern. The progressive wave pattern defines the update dissemination in Internet routing systems running the DUAL and OSPF protocols. Similarly, the stationary wave pattern defines the interactions of peer nodes in structured-peer-to-peer systems, including Chord, Pastry, Tapestry, and CAN. It turns out that both patterns are related. They both disseminate information in form of waves, i.e, sets of messages that originate from single events. Patterns can be instrumented to obtain wave statistics, which enables monitoring the process of self-stabilization in a system. We focus on Internet routing and peer-to-peer systems in this work, since we believe that studying these (existing) systems can lead to engineering principles for self-stabilizing system in various application areas.

  • 42.
    Adamopoulos, Othon
    KTH, Superseded Departments, Materials Science and Engineering.
    A study on nanosized certium oxides systems for environmental catalysis2003Licentiate thesis, comprehensive summary (Other scientific)
  • 43.
    Adamsson, Carl
    et al.
    KTH, Superseded Departments, Physics.
    Anglart, Henryk
    KTH, Superseded Departments, Physics.
    Dryout predictions in bwr fuel assemblies with spacers2004In: Proceedings of the Sixth International Conference on Nuclear Thermal-Hydraulics, Operation and Safety, 2004Conference paper (Refereed)
    Abstract [en]

    A new spacer model has been implemented into the subchannel code Mona-3 and validated against dryout experiments in various rod bundles with different number of spacers and different spacer designs. The spacer-induced deposition enhancement is captured by proper modeling of the turbulence intensity downstream of a spacer.

    The Mona-3 code with the new spacer model captures spacer effects in a correct manner. Both the effect of the number of spacers and the effect of the spacer design are predicted correctly. In particular, the critical power difference between 24-rod bundles with 6 and with 7 spacers is measured to be larger than the difference between 25-rod bundles with 6 and with 7 spacers. This experimental finding is well captured with the Mona-3 code with the present spacer model.

  • 44.
    Adamsson, Niklas
    KTH, Superseded Departments, Machine Design.
    Model-based development of mechatronic systems — Reducing the gaps between competencies?2004In: Proceedings of TMCE 2004: The fifth international symposium on Tools and Methods of Competitive Engineering / [ed] Horvath I, Xirouchakis P, Rotterdam: MILLPRESS SCIENCE PUBLISHERS , 2004, Vol. 1(2), no 405-414, p. 405-413Conference paper (Refereed)
    Abstract [en]

    This paper presents the results of a multiple case study performed within the Swedish vehicle industry. The objective of the study was to explore and describe how modeling affects collaboration within multidisciplinary product development from the perspective of developers. Most research on mechatronics design is focused on technology and/or is limited to one or a few of the disciplines involved. By contrast, the focus of this study is on collaboration between and integration of different technical disciplines. A total of 21 semi-structured interviews were conducted during a period of five months. The criterion for a valid case was that it concerned a development project including distributed functionality and multidisciplinary teams. The main conclusions are that a higher degree of competence integration is needed as complexity increases, that a mutually agreed language is needed within an organization, that the modeling approach within an organization should be aligned, that the tasks where different technical disciplines meet must be identified in order to achieve early system integration, and that short-term co-locations would increase understanding and problem solving efficiency. This research has many similarities with earlier research performed on integrated product development, hut has a different focus level. Instead of on marketing-manufacturing-R&D, the focus is on the technical disciplines within R&D.

  • 45. Addario-Berry, L
    et al.
    Chor, B
    Hallett, M
    Lagergren, Jens
    KTH, Superseded Departments, Numerical Analysis and Computer Science, NADA.
    Panconesi, A
    Wareham, T
    Ancestral maximum likelihood of evolutionary trees is hard2004In: Journal of Bioinformatics and Computational Biology, ISSN 0219-7200, E-ISSN 1757-6334, Vol. 2, no 2, p. 257-271Article in journal (Refereed)
    Abstract [en]

    Maximum likelihood (ML) (Felsenstein, 1981) is an increasingly popular optimality criterion for selecting evolutionary trees. Finding optimal ML trees appears to be a very hard computational task - in particular, algorithms and heuristics for ML take longer to run than algorithms and heuristics for maximum parsimony (MP). However, while MP has been known to be NP-complete for over 20 years, no such hardness result has been obtained so far for ML. In this work we make a first step in this direction by proving that ancestral maximum likelihood (AML) is NP-complete. The input to this problem is a set of aligned sequences of equal length and the goal is to find a tree and an assignment of ancestral sequences for all of that tree's internal vertices such that the likelihood of generating both the ancestral and contemporary sequences is maximized. Our NP-hardness proof follows that for MP given in (Day, Johnson and Sankoff, 1986) in that we use the same reduction from VERTEX COVER; however, the proof of correctness for this reduction relative to AML is different and substantially more involved.

  • 46.
    Adiseno,
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Design Aspects of Fully Integrated Multiband Multistandard Front-End Receivers2003Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    In this thesis, design aspects of fully integrated multibandmultistandard front-end receivers are investigated based onthree fundamental aspects: noise, linearity and operatingfrequency. System level studies were carried out to investigatethe effects of different modulation techniques, duplexing andmultiple access methods on the noise, linearity and selectivityperformance of the circuit. Based on these studies and thelow-cost consideration, zero-IF, low-IF and wideband-IFreceiver architectures are promising architectures. These havea common circuit topology in a direct connection between theLNA and the mixer, which has been explored in this work toimprove the overall RF-to-IF linearity. One front-end circuitapproach is used to achieve a low-cost solution, leading to anew multiband multistandard front-end receiver architecture.This architecture needs a circuit whose performance isadaptable due to different requirements specified in differentstandards, works across several RF-bands and uses a minimumamount ofexternal components.

    Five new circuit topologies suitable for a front-endreceiver consisting of an LNA and mixer (low-noise converter orLNC) were developed. A dual-loop wide-band feedback techniquewas applied in all circuits investigated in this thesis. Threeof the circuits were implemented in 0.18 mm RF-CMOS and 25 GHzbipolar technologies. Measurement results of the circuitsconfirmed the correctness of the design approach.

    The circuits were measured in several RF-bands, i.e. in the900 MHz, 1.8 GHz and 2.4 GHz bands, with S11 ranging from–9.2 dB to–17 dB. The circuits have a typicalperformance of 18-20 dB RF-to-IF gain, 3.5-4 dB DSB NF and upto +4.5 dBm IIP3. In addition, the circuit performance can beadjusted by varying the circuit’s first-stage biascurrent. The circuits may work at frequencies higher than 3GHz, as only 1.5 dB of attenuation is found at 3 GHz and nopeaking is noticed. In the CMOS circuit, the extrapolated gainat 5 GHz is about 15 dB which is consistent with the simulationresult. The die-area of each of the circuits is less than 1mm2.

  • 47.
    Adiseno,
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Design aspects of low-noise amplifiers in low-IF receivers for wireless applications2001Licentiate thesis, comprehensive summary (Other scientific)
  • 48. Adiseno,
    et al.
    Ismail, Mohammed
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Olsson, Håkan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A wide-band RF front-end for multiband multistandard high-linearity low-IF wireless receivers2002In: IEEE Journal of Solid-State Circuits, ISSN 0018-9200, E-ISSN 1558-173X, Vol. 37, no 9, p. 1162-1168Article in journal (Refereed)
    Abstract [en]

    A wide-band radio-frequency (RF) front-end is designed with a balanced combined low-noise amplifier and a switching mixer (a low-noise converter) in RF Si-bipolar process with an f(T) of 25 GHz. The circuit achieves 20-dB conversion gain, higher than -4.5-dBm RF-to-IF IIP3 (+15.5-dBm OIP3) and less than 3.8-dB double-side-band noise figure in 900-MHz (e.g., GSM) and 1.9-GHz (e.g., WCDMA) frequency bands. The -1-dB compression point is -20 dBm at 13-mA dc current consumption from a single 5-V supply. The local-oscillator leakage to the input is less than -56 dBm in the 900-MHz band and less than -63 dBm in the 1.9-GHz band. The -3-dB bandwidth of the amplifier is larger than 3 GHz and a wide-band matching at the input with - 10 to -41-dB S-11 is achieved in the frequency bands of interest by applying a dual-loop wide-band active feedback. The die area is 0.69 x 0.9 mm(2). The circuit is suitable for area-efficient multiband multistandard low-IF receivers.

  • 49. Adiseno,
    et al.
    Ismail, Mohammed
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Olsson, Håkan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Multiband high-linearity front-end receivers for wireless applications2002In: Analog Integrated Circuits and Signal Processing, ISSN 0925-1030, E-ISSN 1573-1979, Vol. 30, no 1, p. 59-67Article in journal (Refereed)
    Abstract [en]

    In this paper, a modified front-end receiver configuration, which consists of an LNA and mixer suitable for zero-IF or low-IF receivers, is presented. The idea is to achieve a better linearity for receivers by combining circuit and system level solutions. Three circuit topologies, two in bipolar and one in CMOS technology, are presented in this paper with their simulation results. One of the bipolar topologies has been implemented and measurement results are presented. An IIP3 of up to +0.6 dBm of a combined bipolar LNA and mixer is achieved, depending on frequency of interest and with an acceptable noise figure performance at a current consumption of less than 13 mA from 5 V supply voltage in one circuit and 3 V supply voltage in the other one. An IIP3 up to +5 dBm is achieved for the CMOS topology at a lower overall gain and acceptable noise figure (14.4 mA and 3 V). All circuits presented in this paper are wideband circuits, suitable for area-efficient multiband receivers.

  • 50.
    Adolfi, Sofia
    et al.
    KTH, Superseded Departments, Casting of Metals.
    Lagerstedt, Anders
    KTH, Superseded Departments, Casting of Metals.
    Sarnet, Jan
    Scana Steel Björneborg AB.
    Fredriksson, Hasse
    KTH, Superseded Departments, Casting of Metals.
    Macrosegregation In Ingot Cast Tool Steel2004Report (Other academic)
1234567 1 - 50 of 11502
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf